[PATCH v2 00/11] kbuild: support building external modules in a separate build directory

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* [PATCH v2 00/11] kbuild: support building external modules in a separate build directory
@ 2024-11-10  1:34 Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 01/11] kbuild: replace two $(abs_objtree) with $(CURDIR) in top Makefile Masahiro Yamada
                   ` (10 more replies)
  0 siblings, 11 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-10  1:34 UTC (permalink / raw)
  To: linux-kbuild; +Cc: linux-kernel, rust-for-linux, cocci, Masahiro Yamada


There has been a long-standing request to support building external
modules in a separate build directory.

In v2, 05/11 introduces a 'srcroot' variable.
(I am not sure if this is the best name, though)
$(srcroot) points to the top of the source directory.
  - When M= is not given, it is the top of the kernel source
  - When M= is given, it is the top of the external module source


Masahiro Yamada (11):
  kbuild: replace two $(abs_objtree) with $(CURDIR) in top Makefile
  kbuild: add $(objtree)/ prefix to some in-kernel build artifacts
  kbuild: rename abs_objtree to abs_output
  kbuild: use 'output' variable to create the output directory
  kbuild: change working directory to external module directory with M=
  kbuild: remove extmod_prefix, MODORDER, MODULES_NSDEPS variables
  kbuild: support building external modules in a separate build
    directory
  kbuild: support -fmacro-prefix-map for external modules
  kbuild: use absolute path in the generated wrapper Makefile
  kbuild: make wrapper Makefile more convenient for external modules
  kbuild: allow to start building external modules in any directory

 Documentation/dev-tools/coccinelle.rst |  20 +--
 Documentation/kbuild/kbuild.rst        |   8 +-
 Documentation/kbuild/makefiles.rst     |  14 ++
 Documentation/kbuild/modules.rst       |  29 ++++-
 Makefile                               | 173 ++++++++++++++++---------
 arch/arm/Makefile                      |   4 +-
 arch/arm64/Makefile                    |   2 +-
 arch/powerpc/Makefile                  |   4 +-
 arch/riscv/Makefile                    |   2 +-
 rust/Makefile                          |   4 +-
 scripts/Kbuild.include                 |   2 +-
 scripts/Makefile.build                 |   6 +-
 scripts/Makefile.clean                 |   2 +-
 scripts/Makefile.compiler              |   2 +-
 scripts/Makefile.host                  |   8 +-
 scripts/Makefile.lib                   |   2 -
 scripts/Makefile.modfinal              |  20 +--
 scripts/Makefile.modinst               |   8 +-
 scripts/Makefile.modpost               |  24 ++--
 scripts/coccicheck                     |   6 +-
 scripts/depmod.sh                      |   4 +-
 scripts/nsdeps                         |  10 +-
 scripts/package/install-extmod-build   |   7 +
 23 files changed, 220 insertions(+), 141 deletions(-)

-- 
2.43.0


^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v2 01/11] kbuild: replace two $(abs_objtree) with $(CURDIR) in top Makefile
  2024-11-10  1:34 [PATCH v2 00/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
@ 2024-11-10  1:34 ` Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 02/11] kbuild: add $(objtree)/ prefix to some in-kernel build artifacts Masahiro Yamada
                   ` (9 subsequent siblings)
  10 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-10  1:34 UTC (permalink / raw)
  To: linux-kbuild
  Cc: linux-kernel, rust-for-linux, cocci, Masahiro Yamada,
	Nicolas Schier

Kbuild changes the working directory until it matches $(abs_objtree).

When $(need-sub-make) is empty, $(abs_objtree) is the same as $(CURDIR).

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
---

(no changes since v1)

 Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 8dceb6830486..891d28e54791 100644
--- a/Makefile
+++ b/Makefile
@@ -228,12 +228,12 @@ else # need-sub-make
 
 # We process the rest of the Makefile if this is the final invocation of make
 
-ifeq ($(abs_srctree),$(abs_objtree))
+ifeq ($(abs_srctree),$(CURDIR))
         # building in the source tree
         srctree := .
 	building_out_of_srctree :=
 else
-        ifeq ($(abs_srctree)/,$(dir $(abs_objtree)))
+        ifeq ($(abs_srctree)/,$(dir $(CURDIR)))
                 # building in a subdirectory of the source tree
                 srctree := ..
         else
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 33+ messages in thread

* [PATCH v2 02/11] kbuild: add $(objtree)/ prefix to some in-kernel build artifacts
  2024-11-10  1:34 [PATCH v2 00/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 01/11] kbuild: replace two $(abs_objtree) with $(CURDIR) in top Makefile Masahiro Yamada
@ 2024-11-10  1:34 ` Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 03/11] kbuild: rename abs_objtree to abs_output Masahiro Yamada
                   ` (8 subsequent siblings)
  10 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-10  1:34 UTC (permalink / raw)
  To: linux-kbuild
  Cc: linux-kernel, rust-for-linux, cocci, Masahiro Yamada,
	Nicolas Schier

$(objtree) refers to the top of the output directory of kernel builds.

This commit adds the explicit $(objtree)/ prefix to build artifacts
needed for building external modules.

This change has no immediate impact, as the top-level Makefile
currently defines:

  objtree         := .

This commit prepares for supporting the building of external modules
in a different directory.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
---

Changes in v2:
  - Add more $(objtree)/ to arch/*/Makefile

 Makefile                  | 10 +++++-----
 arch/arm/Makefile         |  4 ++--
 arch/arm64/Makefile       |  2 +-
 arch/powerpc/Makefile     |  4 ++--
 arch/riscv/Makefile       |  2 +-
 scripts/Kbuild.include    |  2 +-
 scripts/Makefile.build    |  4 ++--
 scripts/Makefile.modfinal | 14 +++++++-------
 scripts/Makefile.modinst  |  2 +-
 scripts/Makefile.modpost  | 12 ++++++------
 scripts/depmod.sh         |  4 ++--
 11 files changed, 30 insertions(+), 30 deletions(-)

diff --git a/Makefile b/Makefile
index 891d28e54791..9b8f4f4cb01b 100644
--- a/Makefile
+++ b/Makefile
@@ -354,7 +354,7 @@ else # !mixed-build
 include $(srctree)/scripts/Kbuild.include
 
 # Read KERNELRELEASE from include/config/kernel.release (if it exists)
-KERNELRELEASE = $(call read-file, include/config/kernel.release)
+KERNELRELEASE = $(call read-file, $(objtree)/include/config/kernel.release)
 KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
 export VERSION PATCHLEVEL SUBLEVEL KERNELRELEASE KERNELVERSION
 
@@ -720,7 +720,7 @@ endif
 export KBUILD_MODULES KBUILD_BUILTIN
 
 ifdef need-config
-include include/config/auto.conf
+include $(objtree)/include/config/auto.conf
 endif
 
 ifeq ($(KBUILD_EXTMOD),)
@@ -783,13 +783,13 @@ else # !may-sync-config
 # and include/config/auto.conf but do not care if they are up-to-date.
 # Use auto.conf to show the error message
 
-checked-configs := include/generated/autoconf.h include/generated/rustc_cfg include/config/auto.conf
+checked-configs := $(addprefix $(objtree)/, include/generated/autoconf.h include/generated/rustc_cfg include/config/auto.conf)
 missing-configs := $(filter-out $(wildcard $(checked-configs)), $(checked-configs))
 
 ifdef missing-configs
-PHONY += include/config/auto.conf
+PHONY += $(objtree)/include/config/auto.conf
 
-include/config/auto.conf:
+$(objtree)/include/config/auto.conf:
 	@echo   >&2 '***'
 	@echo   >&2 '***  ERROR: Kernel configuration is invalid. The following files are missing:'
 	@printf >&2 '***    - %s\n' $(missing-configs)
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index aafebf145738..00ca7886b18e 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -264,13 +264,13 @@ stack_protector_prepare: prepare0
 		-mstack-protector-guard=tls \
 		-mstack-protector-guard-offset=$(shell	\
 			awk '{if ($$2 == "TSK_STACK_CANARY") print $$3;}'\
-				include/generated/asm-offsets.h))
+				$(objtree)/include/generated/asm-offsets.h))
 else
 stack_protector_prepare: prepare0
 	$(eval SSP_PLUGIN_CFLAGS := \
 		-fplugin-arg-arm_ssp_per_task_plugin-offset=$(shell	\
 			awk '{if ($$2 == "TSK_STACK_CANARY") print $$3;}'\
-				include/generated/asm-offsets.h))
+				$(objtree)/include/generated/asm-offsets.h))
 	$(eval KBUILD_CFLAGS += $(SSP_PLUGIN_CFLAGS))
 	$(eval GCC_PLUGINS_CFLAGS += $(SSP_PLUGIN_CFLAGS))
 endif
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 9efd3f37c2fd..358c68565bfd 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -71,7 +71,7 @@ stack_protector_prepare: prepare0
 				-mstack-protector-guard-reg=sp_el0	  \
 				-mstack-protector-guard-offset=$(shell	  \
 			awk '{if ($$2 == "TSK_STACK_CANARY") print $$3;}' \
-					include/generated/asm-offsets.h))
+				$(objtree)/include/generated/asm-offsets.h))
 endif
 
 ifeq ($(CONFIG_ARM64_BTI_KERNEL),y)
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index bbfe4a1f06ef..321b596d2550 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -402,9 +402,9 @@ prepare: stack_protector_prepare
 PHONY += stack_protector_prepare
 stack_protector_prepare: prepare0
 ifdef CONFIG_PPC64
-	$(eval KBUILD_CFLAGS += -mstack-protector-guard-offset=$(shell awk '{if ($$2 == "PACA_CANARY") print $$3;}' include/generated/asm-offsets.h))
+	$(eval KBUILD_CFLAGS += -mstack-protector-guard-offset=$(shell awk '{if ($$2 == "PACA_CANARY") print $$3;}' $(objtree)/include/generated/asm-offsets.h))
 else
-	$(eval KBUILD_CFLAGS += -mstack-protector-guard-offset=$(shell awk '{if ($$2 == "TASK_CANARY") print $$3;}' include/generated/asm-offsets.h))
+	$(eval KBUILD_CFLAGS += -mstack-protector-guard-offset=$(shell awk '{if ($$2 == "TASK_CANARY") print $$3;}' $(objtree)/include/generated/asm-offsets.h))
 endif
 endif
 
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index d469db9f46f4..a08cfeb6cbf9 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -129,7 +129,7 @@ stack_protector_prepare: prepare0
 				-mstack-protector-guard-reg=tp		  \
 				-mstack-protector-guard-offset=$(shell	  \
 			awk '{if ($$2 == "TSK_STACK_CANARY") print $$3;}' \
-					include/generated/asm-offsets.h))
+				$(objtree)/include/generated/asm-offsets.h))
 endif
 
 # arch specific predefines for sparse
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index ed8a7493524b..8c311b997e24 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -205,7 +205,7 @@ if_changed_dep = $(if $(if-changed-cond),$(cmd_and_fixdep),@:)
 
 cmd_and_fixdep =                                                             \
 	$(cmd);                                                              \
-	scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).cmd;\
+	$(objtree)/scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).cmd;\
 	rm -f $(depfile)
 
 # Usage: $(call if_changed_rule,foo)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 8f423a1faf50..64cd046f8fd8 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -34,7 +34,7 @@ subdir-asflags-y :=
 subdir-ccflags-y :=
 
 # Read auto.conf if it exists, otherwise ignore
--include include/config/auto.conf
+-include $(objtree)/include/config/auto.conf
 
 include $(srctree)/scripts/Kbuild.include
 include $(srctree)/scripts/Makefile.compiler
@@ -107,7 +107,7 @@ cmd_cpp_i_c       = $(CPP) $(c_flags) -o $@ $<
 $(obj)/%.i: $(obj)/%.c FORCE
 	$(call if_changed_dep,cpp_i_c)
 
-genksyms = scripts/genksyms/genksyms		\
+genksyms = $(objtree)/scripts/genksyms/genksyms	\
 	$(if $(1), -T $(2))			\
 	$(if $(KBUILD_PRESERVE), -p)		\
 	-r $(or $(wildcard $(2:.symtypes=.symref)), /dev/null)
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index 1482884ec3ca..6d8aa3059ee2 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -6,7 +6,7 @@
 PHONY := __modfinal
 __modfinal:
 
-include include/config/auto.conf
+include $(objtree)/include/config/auto.conf
 include $(srctree)/scripts/Kbuild.include
 
 # for c_flags
@@ -37,15 +37,15 @@ quiet_cmd_ld_ko_o = LD [M]  $@
       cmd_ld_ko_o =							\
 	$(LD) -r $(KBUILD_LDFLAGS)					\
 		$(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE)		\
-		-T scripts/module.lds -o $@ $(filter %.o, $^)
+		-T $(objtree)/scripts/module.lds -o $@ $(filter %.o, $^)
 
 quiet_cmd_btf_ko = BTF [M] $@
       cmd_btf_ko = 							\
-	if [ ! -f vmlinux ]; then					\
+	if [ ! -f $(objtree)/vmlinux ]; then				\
 		printf "Skipping BTF generation for %s due to unavailability of vmlinux\n" $@ 1>&2; \
 	else								\
-		LLVM_OBJCOPY="$(OBJCOPY)" $(PAHOLE) -J $(PAHOLE_FLAGS) $(MODULE_PAHOLE_FLAGS) --btf_base vmlinux $@; \
-		$(RESOLVE_BTFIDS) -b vmlinux $@; 			\
+		LLVM_OBJCOPY="$(OBJCOPY)" $(PAHOLE) -J $(PAHOLE_FLAGS) $(MODULE_PAHOLE_FLAGS) --btf_base $(objtree)/vmlinux $@; \
+		$(RESOLVE_BTFIDS) -b $(objtree)/vmlinux $@;		\
 	fi;
 
 # Same as newer-prereqs, but allows to exclude specified extra dependencies
@@ -57,8 +57,8 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check),      \
 	printf '%s\n' 'savedcmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
 
 # Re-generate module BTFs if either module's .ko or vmlinux changed
-%.ko: %.o %.mod.o $(extmod_prefix).module-common.o scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),vmlinux) FORCE
-	+$(call if_changed_except,ld_ko_o,vmlinux)
+%.ko: %.o %.mod.o $(extmod_prefix).module-common.o $(objtree)/scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),$(objtree)/vmlinux) FORCE
+	+$(call if_changed_except,ld_ko_o,$(objtree)/vmlinux)
 ifdef CONFIG_DEBUG_INFO_BTF_MODULES
 	+$(if $(newer-prereqs),$(call cmd,btf_ko))
 endif
diff --git a/scripts/Makefile.modinst b/scripts/Makefile.modinst
index d97720943189..6fa9af4a25b4 100644
--- a/scripts/Makefile.modinst
+++ b/scripts/Makefile.modinst
@@ -6,7 +6,7 @@
 PHONY := __modinst
 __modinst:
 
-include include/config/auto.conf
+include $(objtree)/include/config/auto.conf
 include $(srctree)/scripts/Kbuild.include
 
 install-y :=
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 44936ebad161..12e7c15d099c 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -35,10 +35,10 @@
 PHONY := __modpost
 __modpost:
 
-include include/config/auto.conf
+include $(objtree)/include/config/auto.conf
 include $(srctree)/scripts/Kbuild.include
 
-MODPOST = scripts/mod/modpost
+MODPOST = $(objtree)/scripts/mod/modpost
 
 modpost-args =										\
 	$(if $(CONFIG_MODULES),-M)							\
@@ -119,11 +119,11 @@ include $(kbuild-file)
 
 output-symdump := $(KBUILD_EXTMOD)/Module.symvers
 
-ifeq ($(wildcard Module.symvers),)
-missing-input := Module.symvers
+ifeq ($(wildcard $(objtree)/Module.symvers),)
+missing-input := $(objtree)/Module.symvers
 else
-modpost-args += -i Module.symvers
-modpost-deps += Module.symvers
+modpost-args += -i $(objtree)/Module.symvers
+modpost-deps += $(objtree)/Module.symvers
 endif
 
 modpost-args += -e $(addprefix -i , $(KBUILD_EXTRA_SYMBOLS))
diff --git a/scripts/depmod.sh b/scripts/depmod.sh
index e22da27fe13e..3c34fecacbc8 100755
--- a/scripts/depmod.sh
+++ b/scripts/depmod.sh
@@ -12,7 +12,7 @@ KERNELRELEASE=$1
 
 : ${DEPMOD:=depmod}
 
-if ! test -r System.map ; then
+if ! test -r "${objtree}/System.map" ; then
 	echo "Warning: modules_install: missing 'System.map' file. Skipping depmod." >&2
 	exit 0
 fi
@@ -25,7 +25,7 @@ if [ -z $(command -v $DEPMOD) ]; then
 	exit 0
 fi
 
-set -- -ae -F System.map
+set -- -ae -F "${objtree}/System.map"
 if test -n "$INSTALL_MOD_PATH"; then
 	set -- "$@" -b "$INSTALL_MOD_PATH"
 fi
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 33+ messages in thread

* [PATCH v2 03/11] kbuild: rename abs_objtree to abs_output
  2024-11-10  1:34 [PATCH v2 00/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 01/11] kbuild: replace two $(abs_objtree) with $(CURDIR) in top Makefile Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 02/11] kbuild: add $(objtree)/ prefix to some in-kernel build artifacts Masahiro Yamada
@ 2024-11-10  1:34 ` Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 04/11] kbuild: use 'output' variable to create the output directory Masahiro Yamada
                   ` (7 subsequent siblings)
  10 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-10  1:34 UTC (permalink / raw)
  To: linux-kbuild
  Cc: linux-kernel, rust-for-linux, cocci, Masahiro Yamada,
	Nicolas Schier

'objtree' refers to the top of the output directory of kernel builds.

Rename abs_objtree to a more generic name, to better reflect its use in
the context of external module builds.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
---

(no changes since v1)

 Makefile | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/Makefile b/Makefile
index 9b8f4f4cb01b..deb3f01863f8 100644
--- a/Makefile
+++ b/Makefile
@@ -40,7 +40,7 @@ __all:
 
 this-makefile := $(lastword $(MAKEFILE_LIST))
 abs_srctree := $(realpath $(dir $(this-makefile)))
-abs_objtree := $(CURDIR)
+abs_output := $(CURDIR)
 
 ifneq ($(sub_make_done),1)
 
@@ -185,8 +185,8 @@ ifneq ($(KBUILD_OUTPUT),)
 # $(realpath ...) gets empty if the path does not exist. Run 'mkdir -p' first.
 $(shell mkdir -p "$(KBUILD_OUTPUT)")
 # $(realpath ...) resolves symlinks
-abs_objtree := $(realpath $(KBUILD_OUTPUT))
-$(if $(abs_objtree),,$(error failed to create output directory "$(KBUILD_OUTPUT)"))
+abs_output := $(realpath $(KBUILD_OUTPUT))
+$(if $(abs_output),,$(error failed to create output directory "$(KBUILD_OUTPUT)"))
 endif # ifneq ($(KBUILD_OUTPUT),)
 
 ifneq ($(words $(subst :, ,$(abs_srctree))), 1)
@@ -197,7 +197,7 @@ export sub_make_done := 1
 
 endif # sub_make_done
 
-ifeq ($(abs_objtree),$(CURDIR))
+ifeq ($(abs_output),$(CURDIR))
 # Suppress "Entering directory ..." if we are at the final work directory.
 no-print-directory := --no-print-directory
 else
@@ -221,7 +221,7 @@ $(filter-out $(this-makefile), $(MAKECMDGOALS)) __all: __sub-make
 
 # Invoke a second make in the output directory, passing relevant variables
 __sub-make:
-	$(Q)$(MAKE) $(no-print-directory) -C $(abs_objtree) \
+	$(Q)$(MAKE) $(no-print-directory) -C $(abs_output) \
 	-f $(abs_srctree)/Makefile $(MAKECMDGOALS)
 
 else # need-sub-make
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 33+ messages in thread

* [PATCH v2 04/11] kbuild: use 'output' variable to create the output directory
  2024-11-10  1:34 [PATCH v2 00/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
                   ` (2 preceding siblings ...)
  2024-11-10  1:34 ` [PATCH v2 03/11] kbuild: rename abs_objtree to abs_output Masahiro Yamada
@ 2024-11-10  1:34 ` Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 05/11] kbuild: change working directory to external module directory with M= Masahiro Yamada
                   ` (6 subsequent siblings)
  10 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-10  1:34 UTC (permalink / raw)
  To: linux-kbuild
  Cc: linux-kernel, rust-for-linux, cocci, Masahiro Yamada,
	Nicolas Schier

$(KBUILD_OUTPUT) specifies the output directory of kernel builds.

Use a more generic name, 'output', to better reflect this code hunk in
the context of external module builds.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
---

(no changes since v1)

 Makefile | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index deb3f01863f8..cf1d55560ae2 100644
--- a/Makefile
+++ b/Makefile
@@ -176,18 +176,20 @@ export KBUILD_EXTRA_WARN
 # The O= assignment takes precedence over the KBUILD_OUTPUT environment
 # variable.
 
-# Do we want to change the working directory?
 ifeq ("$(origin O)", "command line")
   KBUILD_OUTPUT := $(O)
 endif
 
-ifneq ($(KBUILD_OUTPUT),)
+output := $(KBUILD_OUTPUT)
+
+# Do we want to change the working directory?
+ifneq ($(output),)
 # $(realpath ...) gets empty if the path does not exist. Run 'mkdir -p' first.
-$(shell mkdir -p "$(KBUILD_OUTPUT)")
+$(shell mkdir -p "$(output)")
 # $(realpath ...) resolves symlinks
-abs_output := $(realpath $(KBUILD_OUTPUT))
-$(if $(abs_output),,$(error failed to create output directory "$(KBUILD_OUTPUT)"))
-endif # ifneq ($(KBUILD_OUTPUT),)
+abs_output := $(realpath $(output))
+$(if $(abs_output),,$(error failed to create output directory "$(output)"))
+endif
 
 ifneq ($(words $(subst :, ,$(abs_srctree))), 1)
 $(error source directory cannot contain spaces or colons)
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 33+ messages in thread

* [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-11-10  1:34 [PATCH v2 00/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
                   ` (3 preceding siblings ...)
  2024-11-10  1:34 ` [PATCH v2 04/11] kbuild: use 'output' variable to create the output directory Masahiro Yamada
@ 2024-11-10  1:34 ` Masahiro Yamada
  2024-11-18 14:47   ` Nicolas Schier
                     ` (5 more replies)
  2024-11-10  1:34 ` [PATCH v2 06/11] kbuild: remove extmod_prefix, MODORDER, MODULES_NSDEPS variables Masahiro Yamada
                   ` (5 subsequent siblings)
  10 siblings, 6 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-10  1:34 UTC (permalink / raw)
  To: linux-kbuild; +Cc: linux-kernel, rust-for-linux, cocci, Masahiro Yamada

Currently, Kbuild always operates in the output directory of the kernel,
even when building external modules. This increases the risk of external
module Makefiles attempting to write to the kernel directory.

This commit switches the working directory to the external module
directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
some build artifacts.

The command for building external modules maintains backward
compatibility, but Makefiles that rely on working in the kernel
directory may break. In such cases, $(objtree) and $(srctree) should
be used to refer to the output and source directories of the kernel.

The appearance of the build log will change as follows:

[Before]

  $ make -C /path/to/my/linux M=/path/to/my/externel/module
  make: Entering directory '/path/to/my/linux'
    CC [M]  /path/to/my/externel/module/helloworld.o
    MODPOST /path/to/my/externel/module/Module.symvers
    CC [M]  /path/to/my/externel/module/helloworld.mod.o
    CC [M]  /path/to/my/externel/module/.module-common.o
    LD [M]  /path/to/my/externel/module/helloworld.ko
  make: Leaving directory '/path/to/my/linux'

[After]

  $ make -C /path/to/my/linux M=/path/to/my/externel/module
  make: Entering directory '/path/to/my/linux'
  make[1]: Entering directory '/path/to/my/externel/module'
    CC [M]  helloworld.o
    MODPOST Module.symvers
    CC [M]  helloworld.mod.o
    CC [M]  .module-common.o
    LD [M]  helloworld.ko
  make[1]: Leaving directory '/path/to/my/externel/module'
  make: Leaving directory '/path/to/my/linux'

Printing "Entering directory" twice is cumbersome. This will be
addressed later.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

Changes in v2:
 - Introduce a new 'srcroot' variable and clean-up code
 - Reword Documentation/dev-tools/coccinelle.rst

 Documentation/dev-tools/coccinelle.rst | 20 ++-----
 Documentation/kbuild/makefiles.rst     | 14 +++++
 Makefile                               | 80 +++++++++++++++-----------
 rust/Makefile                          |  4 +-
 scripts/Makefile.build                 |  2 +-
 scripts/Makefile.clean                 |  2 +-
 scripts/Makefile.compiler              |  2 +-
 scripts/Makefile.modpost               |  6 +-
 scripts/coccicheck                     |  6 +-
 scripts/nsdeps                         |  8 +--
 scripts/package/install-extmod-build   |  7 +++
 11 files changed, 85 insertions(+), 66 deletions(-)

diff --git a/Documentation/dev-tools/coccinelle.rst b/Documentation/dev-tools/coccinelle.rst
index 535ce126fb4f..6e70a1e9a3c0 100644
--- a/Documentation/dev-tools/coccinelle.rst
+++ b/Documentation/dev-tools/coccinelle.rst
@@ -250,25 +250,17 @@ variables for .cocciconfig is as follows:
 - Your directory from which spatch is called is processed next
 - The directory provided with the ``--dir`` option is processed last, if used
 
-Since coccicheck runs through make, it naturally runs from the kernel
-proper dir; as such the second rule above would be implied for picking up a
-.cocciconfig when using ``make coccicheck``.
-
 ``make coccicheck`` also supports using M= targets. If you do not supply
 any M= target, it is assumed you want to target the entire kernel.
 The kernel coccicheck script has::
 
-    if [ "$KBUILD_EXTMOD" = "" ] ; then
-        OPTIONS="--dir $srctree $COCCIINCLUDE"
-    else
-        OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
-    fi
+    OPTIONS="--dir $srcroot $COCCIINCLUDE"
 
-KBUILD_EXTMOD is set when an explicit target with M= is used. For both cases
-the spatch ``--dir`` argument is used, as such third rule applies when whether
-M= is used or not, and when M= is used the target directory can have its own
-.cocciconfig file. When M= is not passed as an argument to coccicheck the
-target directory is the same as the directory from where spatch was called.
+Here, $srcroot refers to the source directory of the target: it points to the
+external module's source directory when M= used, and otherwise, to the kernel
+source directory. The third rule ensures the spatch reads the .cocciconfig from
+the target directory, allowing external modules to have their own .cocciconfig
+file.
 
 If not using the kernel's coccicheck target, keep the above precedence
 order logic of .cocciconfig reading. If using the kernel's coccicheck target,
diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
index 7964e0c245ae..d36519f194dc 100644
--- a/Documentation/kbuild/makefiles.rst
+++ b/Documentation/kbuild/makefiles.rst
@@ -449,6 +449,20 @@ $(obj)
   to prerequisites are referenced with $(src) (because they are not
   generated files).
 
+$(srcroot)
+  $(srcroot) refers to the root of the source you are building, which can be
+  either the kernel source or the external modules source, depending on whether
+  KBUILD_EXTMOD is set. This can be either a relative or an absolute path, but
+  if KBUILD_ABS_SRCTREE=1 is set, it is always an absolute path.
+
+$(srctree)
+  $(srctree) refers to the root of the kernel source tree. When building the
+  kernel, this is the same as $(srcroot).
+
+$(objtree)
+  $(objtree) refers to the root of the kernel object tree. It is ``.`` when
+  building the kernel, but it is different when building external modules.
+
 $(kecho)
   echoing information to user in a rule is often a good practice
   but when execution ``make -s`` one does not expect to see any output
diff --git a/Makefile b/Makefile
index cf1d55560ae2..e5f7ac7647a7 100644
--- a/Makefile
+++ b/Makefile
@@ -180,7 +180,24 @@ ifeq ("$(origin O)", "command line")
   KBUILD_OUTPUT := $(O)
 endif
 
-output := $(KBUILD_OUTPUT)
+ifdef KBUILD_EXTMOD
+    ifdef KBUILD_OUTPUT
+        objtree := $(realpath $(KBUILD_OUTPUT))
+        $(if $(objtree),,$(error specified kernel directory "$(KBUILD_OUTPUT)" does not exist))
+    else
+        objtree := $(CURDIR)
+    endif
+    output := $(KBUILD_EXTMOD)
+    # KBUILD_EXTMOD might be a relative path. Remember its absolute path before
+    # Make changes the working directory.
+    srcroot := $(realpath $(KBUILD_EXTMOD))
+    $(if $(srcroot),,$(error specified external module directory "$(KBUILD_EXTMOD)" does not exist))
+else
+    objtree := .
+    output := $(KBUILD_OUTPUT)
+endif
+
+export objtree srcroot
 
 # Do we want to change the working directory?
 ifneq ($(output),)
@@ -230,35 +247,33 @@ else # need-sub-make
 
 # We process the rest of the Makefile if this is the final invocation of make
 
-ifeq ($(abs_srctree),$(CURDIR))
-        # building in the source tree
-        srctree := .
-	building_out_of_srctree :=
+ifndef KBUILD_EXTMOD
+srcroot := $(abs_srctree)
+endif
+
+ifeq ($(srcroot),$(CURDIR))
+building_out_of_srctree :=
 else
-        ifeq ($(abs_srctree)/,$(dir $(CURDIR)))
-                # building in a subdirectory of the source tree
-                srctree := ..
-        else
-                srctree := $(abs_srctree)
-        endif
-	building_out_of_srctree := 1
+export building_out_of_srctree :=1
 endif
 
-ifneq ($(KBUILD_ABS_SRCTREE),)
-srctree := $(abs_srctree)
+ifdef KBUILD_ABS_SRCTREE
+    # Do not nothing. Use the absolute path.
+else ifeq ($(srcroot),$(CURDIR))
+    # Building in the source.
+    srcroot := .
+else ifeq ($(srcroot)/,$(dir $(CURDIR)))
+    # Building in a subdirectory of the source.
+    srcroot := ..
 endif
 
-objtree		:= .
+export srctree := $(if $(KBUILD_EXTMOD),$(abs_srctree),$(srcroot))
 
-VPATH		:=
-
-ifeq ($(KBUILD_EXTMOD),)
 ifdef building_out_of_srctree
-VPATH		:= $(srctree)
+export VPATH := $(srcroot)
+else
+VPATH :=
 endif
-endif
-
-export building_out_of_srctree srctree objtree VPATH
 
 # To make sure we do not include .config for any of the *config targets
 # catch them early, and hand them over to scripts/kconfig/Makefile
@@ -711,7 +726,7 @@ endif
 # in addition to whatever we do anyway.
 # Just "make" or "make all" shall build modules as well
 
-ifneq ($(filter all modules nsdeps %compile_commands.json clang-%,$(MAKECMDGOALS)),)
+ifneq ($(filter all modules nsdeps compile_commands.json clang-%,$(MAKECMDGOALS)),)
   KBUILD_MODULES := 1
 endif
 
@@ -1107,7 +1122,7 @@ export MODLIB
 
 PHONY += prepare0
 
-export extmod_prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)
+export extmod_prefix =
 export MODORDER := $(extmod_prefix)modules.order
 export MODULES_NSDEPS := $(extmod_prefix)modules.nsdeps
 
@@ -1799,14 +1814,10 @@ filechk_kernel.release = echo $(KERNELRELEASE)
 KBUILD_BUILTIN :=
 KBUILD_MODULES := 1
 
-build-dir := $(KBUILD_EXTMOD)
+build-dir := .
 
-compile_commands.json: $(extmod_prefix)compile_commands.json
-PHONY += compile_commands.json
-
-clean-dirs := $(KBUILD_EXTMOD)
-clean: private rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps \
-	$(KBUILD_EXTMOD)/compile_commands.json
+clean-dirs := .
+clean: private rm-files := Module.symvers modules.nsdeps compile_commands.json
 
 PHONY += prepare
 # now expand this into a simple variable to reduce the cost of shell evaluations
@@ -1948,7 +1959,7 @@ $(clean-dirs):
 
 clean: $(clean-dirs)
 	$(call cmd,rmfiles)
-	@find $(or $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
+	@find . $(RCS_FIND_IGNORE) \
 		\( -name '*.[aios]' -o -name '*.rsi' -o -name '*.ko' -o -name '.*.cmd' \
 		-o -name '*.ko.*' \
 		-o -name '*.dtb' -o -name '*.dtbo' \
@@ -1981,7 +1992,12 @@ tags TAGS cscope gtags: FORCE
 PHONY += rust-analyzer
 rust-analyzer:
 	+$(Q)$(CONFIG_SHELL) $(srctree)/scripts/rust_is_available.sh
+ifdef KBUILD_EXTMOD
+# FIXME: external modules must not descend into a sub-directory of the kernel
+	$(Q)$(MAKE) $(build)=$(objtree)/rust src=$(srctree)/rust $@
+else
 	$(Q)$(MAKE) $(build)=rust $@
+endif
 
 # Script to generate missing namespace dependencies
 # ---------------------------------------------------------------------------
diff --git a/rust/Makefile b/rust/Makefile
index b5e0a73b78f3..742740816c4b 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -362,8 +362,8 @@ rust-analyzer:
 	$(Q)$(srctree)/scripts/generate_rust_analyzer.py \
 		--cfgs='core=$(core-cfgs)' --cfgs='alloc=$(alloc-cfgs)' \
 		$(realpath $(srctree)) $(realpath $(objtree)) \
-		$(rustc_sysroot) $(RUST_LIB_SRC) $(KBUILD_EXTMOD) > \
-		$(if $(KBUILD_EXTMOD),$(extmod_prefix),$(objtree))/rust-project.json
+		$(rustc_sysroot) $(RUST_LIB_SRC) $(if $(KBUILD_EXTMOD),$(srcroot)) \
+		> rust-project.json
 
 redirect-intrinsics = \
 	__addsf3 __eqsf2 __extendsfdf2 __gesf2 __lesf2 __ltsf2 __mulsf3 __nesf2 __truncdfsf2 __unordsf2 \
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 64cd046f8fd8..1aa928a6fb4f 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -3,7 +3,7 @@
 # Building
 # ==========================================================================
 
-src := $(if $(VPATH),$(VPATH)/)$(obj)
+src := $(srcroot)/$(obj)
 
 PHONY := $(obj)/
 $(obj)/:
diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean
index 4fcfab40ed61..6ead00ec7313 100644
--- a/scripts/Makefile.clean
+++ b/scripts/Makefile.clean
@@ -3,7 +3,7 @@
 # Cleaning up
 # ==========================================================================
 
-src := $(if $(VPATH),$(VPATH)/)$(obj)
+src := $(srcroot)/$(obj)
 
 PHONY := __clean
 __clean:
diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
index e0842496d26e..8c1029687e2e 100644
--- a/scripts/Makefile.compiler
+++ b/scripts/Makefile.compiler
@@ -13,7 +13,7 @@ cc-cross-prefix = $(firstword $(foreach c, $(1), \
 			$(if $(shell command -v -- $(c)gcc 2>/dev/null), $(c))))
 
 # output directory for tests below
-TMPOUT = $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/).tmp_$$$$
+TMPOUT = .tmp_$$$$
 
 # try-run
 # Usage: option = $(call try-run, $(CC)...-o "$$TMP",option-ok,otherwise)
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 12e7c15d099c..78d2ca4f25f5 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -111,13 +111,13 @@ endif
 else
 
 # set src + obj - they may be used in the modules's Makefile
-obj := $(KBUILD_EXTMOD)
-src := $(if $(VPATH),$(VPATH)/)$(obj)
+obj := .
+src := $(srcroot)
 
 # Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS
 include $(kbuild-file)
 
-output-symdump := $(KBUILD_EXTMOD)/Module.symvers
+output-symdump := Module.symvers
 
 ifeq ($(wildcard $(objtree)/Module.symvers),)
 missing-input := $(objtree)/Module.symvers
diff --git a/scripts/coccicheck b/scripts/coccicheck
index e52cb43fede6..0e6bc5a10320 100755
--- a/scripts/coccicheck
+++ b/scripts/coccicheck
@@ -80,11 +80,7 @@ command results in a shift count error.'
     NPROC=1
 else
     ONLINE=0
-    if [ "$KBUILD_EXTMOD" = "" ] ; then
-        OPTIONS="--dir $srctree $COCCIINCLUDE"
-    else
-        OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
-    fi
+    OPTIONS="--dir $srcroot $COCCIINCLUDE"
 
     # Use only one thread per core by default if hyperthreading is enabled
     THREADS_PER_CORE=$(LANG=C lscpu | grep "Thread(s) per core: " | tr -cd "[:digit:]")
diff --git a/scripts/nsdeps b/scripts/nsdeps
index f1718cc0d700..8ca12e2b5c03 100644
--- a/scripts/nsdeps
+++ b/scripts/nsdeps
@@ -19,12 +19,6 @@ if ! { echo "$SPATCH_REQ_VERSION"; echo "$SPATCH_VERSION"; } | sort -CV ; then
 	exit 1
 fi
 
-if [ "$KBUILD_EXTMOD" ]; then
-	src_prefix=
-else
-	src_prefix=$srctree/
-fi
-
 generate_deps_for_ns() {
 	$SPATCH --very-quiet --in-place --sp-file \
 		$srctree/scripts/coccinelle/misc/add_namespace.cocci -D nsdeps -D ns=$1 $2
@@ -34,7 +28,7 @@ generate_deps() {
 	local mod=${1%.ko:}
 	shift
 	local namespaces="$*"
-	local mod_source_files=$(sed "s|^\(.*\)\.o$|${src_prefix}\1.c|" $mod.mod)
+	local mod_source_files=$(sed "s|^\(.*\)\.o$|${srcroot}/\1.c|" $mod.mod)
 
 	for ns in $namespaces; do
 		echo "Adding namespace $ns to module $mod.ko."
diff --git a/scripts/package/install-extmod-build b/scripts/package/install-extmod-build
index 7ec1f061a519..64d958ee45f3 100755
--- a/scripts/package/install-extmod-build
+++ b/scripts/package/install-extmod-build
@@ -51,6 +51,13 @@ mkdir -p "${destdir}"
 if [ "${CC}" != "${HOSTCC}" ]; then
 	echo "Rebuilding host programs with ${CC}..."
 
+	# This leverages external module building.
+	# - Clear sub_make_done to allow the top-level Makefile to redo sub-make.
+	# - Filter out --no-print-directory to print "Entering directory" logs
+	#   when Make changes the working directory.
+	unset sub_make_done
+	MAKEFLAGS=$(echo "${MAKEFLAGS}" | sed s/--no-print-directory//)
+
 	cat <<-'EOF' >  "${destdir}/Kbuild"
 	subdir-y := scripts
 	EOF
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-11-10  1:34 ` [PATCH v2 05/11] kbuild: change working directory to external module directory with M= Masahiro Yamada
@ 2024-11-18 14:47   ` Nicolas Schier
  2024-11-18 17:02     ` Masahiro Yamada
  2024-12-04 20:51   ` Alison Schofield
                     ` (4 subsequent siblings)
  5 siblings, 1 reply; 33+ messages in thread
From: Nicolas Schier @ 2024-11-18 14:47 UTC (permalink / raw)
  To: Masahiro Yamada
  Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci, Nicolas Schier

On Sun, Nov 10, 2024 at 10:34:33AM +0900, Masahiro Yamada wrote:
> Currently, Kbuild always operates in the output directory of the kernel,
> even when building external modules. This increases the risk of external
> module Makefiles attempting to write to the kernel directory.
> 
> This commit switches the working directory to the external module
> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> some build artifacts.
> 
> The command for building external modules maintains backward
> compatibility, but Makefiles that rely on working in the kernel
> directory may break. In such cases, $(objtree) and $(srctree) should
> be used to refer to the output and source directories of the kernel.
> 
> The appearance of the build log will change as follows:
> 
> [Before]
> 
>   $ make -C /path/to/my/linux M=/path/to/my/externel/module
>   make: Entering directory '/path/to/my/linux'
>     CC [M]  /path/to/my/externel/module/helloworld.o
>     MODPOST /path/to/my/externel/module/Module.symvers
>     CC [M]  /path/to/my/externel/module/helloworld.mod.o
>     CC [M]  /path/to/my/externel/module/.module-common.o
>     LD [M]  /path/to/my/externel/module/helloworld.ko
>   make: Leaving directory '/path/to/my/linux'
> 
> [After]
> 
>   $ make -C /path/to/my/linux M=/path/to/my/externel/module
>   make: Entering directory '/path/to/my/linux'
>   make[1]: Entering directory '/path/to/my/externel/module'
>     CC [M]  helloworld.o
>     MODPOST Module.symvers
>     CC [M]  helloworld.mod.o
>     CC [M]  .module-common.o
>     LD [M]  helloworld.ko
>   make[1]: Leaving directory '/path/to/my/externel/module'
>   make: Leaving directory '/path/to/my/linux'
> 
> Printing "Entering directory" twice is cumbersome. This will be
> addressed later.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
> 
> Changes in v2:
>  - Introduce a new 'srcroot' variable and clean-up code
>  - Reword Documentation/dev-tools/coccinelle.rst
> 
>  Documentation/dev-tools/coccinelle.rst | 20 ++-----
>  Documentation/kbuild/makefiles.rst     | 14 +++++
>  Makefile                               | 80 +++++++++++++++-----------
>  rust/Makefile                          |  4 +-
>  scripts/Makefile.build                 |  2 +-
>  scripts/Makefile.clean                 |  2 +-
>  scripts/Makefile.compiler              |  2 +-
>  scripts/Makefile.modpost               |  6 +-
>  scripts/coccicheck                     |  6 +-
>  scripts/nsdeps                         |  8 +--
>  scripts/package/install-extmod-build   |  7 +++
>  11 files changed, 85 insertions(+), 66 deletions(-)
> 
> diff --git a/Documentation/dev-tools/coccinelle.rst b/Documentation/dev-tools/coccinelle.rst
> index 535ce126fb4f..6e70a1e9a3c0 100644
> --- a/Documentation/dev-tools/coccinelle.rst
> +++ b/Documentation/dev-tools/coccinelle.rst
> @@ -250,25 +250,17 @@ variables for .cocciconfig is as follows:
>  - Your directory from which spatch is called is processed next
>  - The directory provided with the ``--dir`` option is processed last, if used
>  
> -Since coccicheck runs through make, it naturally runs from the kernel
> -proper dir; as such the second rule above would be implied for picking up a
> -.cocciconfig when using ``make coccicheck``.
> -
>  ``make coccicheck`` also supports using M= targets. If you do not supply
>  any M= target, it is assumed you want to target the entire kernel.
>  The kernel coccicheck script has::
>  
> -    if [ "$KBUILD_EXTMOD" = "" ] ; then
> -        OPTIONS="--dir $srctree $COCCIINCLUDE"
> -    else
> -        OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
> -    fi
> +    OPTIONS="--dir $srcroot $COCCIINCLUDE"
>  
> -KBUILD_EXTMOD is set when an explicit target with M= is used. For both cases
> -the spatch ``--dir`` argument is used, as such third rule applies when whether
> -M= is used or not, and when M= is used the target directory can have its own
> -.cocciconfig file. When M= is not passed as an argument to coccicheck the
> -target directory is the same as the directory from where spatch was called.
> +Here, $srcroot refers to the source directory of the target: it points to the
> +external module's source directory when M= used, and otherwise, to the kernel
> +source directory. The third rule ensures the spatch reads the .cocciconfig from
> +the target directory, allowing external modules to have their own .cocciconfig
> +file.
>  
>  If not using the kernel's coccicheck target, keep the above precedence
>  order logic of .cocciconfig reading. If using the kernel's coccicheck target,
> diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
> index 7964e0c245ae..d36519f194dc 100644
> --- a/Documentation/kbuild/makefiles.rst
> +++ b/Documentation/kbuild/makefiles.rst
> @@ -449,6 +449,20 @@ $(obj)
>    to prerequisites are referenced with $(src) (because they are not
>    generated files).
>  
> +$(srcroot)
> +  $(srcroot) refers to the root of the source you are building, which can be
> +  either the kernel source or the external modules source, depending on whether
> +  KBUILD_EXTMOD is set. This can be either a relative or an absolute path, but
> +  if KBUILD_ABS_SRCTREE=1 is set, it is always an absolute path.
> +
> +$(srctree)
> +  $(srctree) refers to the root of the kernel source tree. When building the
> +  kernel, this is the same as $(srcroot).
> +
> +$(objtree)
> +  $(objtree) refers to the root of the kernel object tree. It is ``.`` when
> +  building the kernel, but it is different when building external modules.
> +

Thanks, I think it's nice that there is now such a clear definition.
$(srcroot) sounds fine to me.

>  $(kecho)
>    echoing information to user in a rule is often a good practice
>    but when execution ``make -s`` one does not expect to see any output
> diff --git a/Makefile b/Makefile
> index cf1d55560ae2..e5f7ac7647a7 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -180,7 +180,24 @@ ifeq ("$(origin O)", "command line")
>    KBUILD_OUTPUT := $(O)
>  endif
>  
> -output := $(KBUILD_OUTPUT)
> +ifdef KBUILD_EXTMOD
> +    ifdef KBUILD_OUTPUT
> +        objtree := $(realpath $(KBUILD_OUTPUT))
> +        $(if $(objtree),,$(error specified kernel directory "$(KBUILD_OUTPUT)" does not exist))
> +    else
> +        objtree := $(CURDIR)
> +    endif
> +    output := $(KBUILD_EXTMOD)
> +    # KBUILD_EXTMOD might be a relative path. Remember its absolute path before
> +    # Make changes the working directory.
> +    srcroot := $(realpath $(KBUILD_EXTMOD))
> +    $(if $(srcroot),,$(error specified external module directory "$(KBUILD_EXTMOD)" does not exist))
> +else
> +    objtree := .
> +    output := $(KBUILD_OUTPUT)
> +endif
> +
> +export objtree srcroot
>  
>  # Do we want to change the working directory?
>  ifneq ($(output),)
> @@ -230,35 +247,33 @@ else # need-sub-make
>  
>  # We process the rest of the Makefile if this is the final invocation of make
>  
> -ifeq ($(abs_srctree),$(CURDIR))
> -        # building in the source tree
> -        srctree := .
> -	building_out_of_srctree :=
> +ifndef KBUILD_EXTMOD
> +srcroot := $(abs_srctree)
> +endif
> +
> +ifeq ($(srcroot),$(CURDIR))
> +building_out_of_srctree :=
>  else
> -        ifeq ($(abs_srctree)/,$(dir $(CURDIR)))
> -                # building in a subdirectory of the source tree
> -                srctree := ..
> -        else
> -                srctree := $(abs_srctree)
> -        endif
> -	building_out_of_srctree := 1
> +export building_out_of_srctree :=1
>  endif
>  
> -ifneq ($(KBUILD_ABS_SRCTREE),)
> -srctree := $(abs_srctree)
> +ifdef KBUILD_ABS_SRCTREE
> +    # Do not nothing. Use the absolute path.
> +else ifeq ($(srcroot),$(CURDIR))
> +    # Building in the source.
> +    srcroot := .
> +else ifeq ($(srcroot)/,$(dir $(CURDIR)))
> +    # Building in a subdirectory of the source.
> +    srcroot := ..
>  endif
>  
> -objtree		:= .
> +export srctree := $(if $(KBUILD_EXTMOD),$(abs_srctree),$(srcroot))

With this patch applied, the following breaks for me:

    $ make O=build M=fs/btrfs CONFIG_BTRFS_FS=m
    make[1]: Entering directory '/data/linux/kbuild-review/fs/btrfs'
      CC [M]  super.o
    In file included from <command-line>:
    /data/linux/kbuild-review/include/linux/compiler_types.h:89:10: fatal error: linux/compiler_attributes.h: No such file or directory
       89 | #include <linux/compiler_attributes.h>
          |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    compilation terminated.

Adding 'ccflags-y += -I$(srctree)/include' to fs/btrfs/Makefile breaks
the build loudly.  I could make it build again with

diff --git a/Makefile b/Makefile
index e5f7ac7647a7b..3d95911f1a68f 100644
--- a/Makefile
+++ b/Makefile
@@ -555,7 +555,7 @@ USERINCLUDE    := \
 LINUXINCLUDE    := \
                -I$(srctree)/arch/$(SRCARCH)/include \
                -I$(objtree)/arch/$(SRCARCH)/include/generated \
-               $(if $(building_out_of_srctree),-I$(srctree)/include) \
+               $(if $(or $(building_out_of_srctree),$(filter $(srctree)/%, $(CURDIR))),-I$(srctree)/include) \
                -I$(objtree)/include \
                $(USERINCLUDE)

but this does not feel good.  It building in-tree modules in this way a
valid thing to do?

Kind regards,
Nicolas

^ permalink raw reply related	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-11-18 14:47   ` Nicolas Schier
@ 2024-11-18 17:02     ` Masahiro Yamada
  2024-11-27 15:29       ` Nicolas Schier
  0 siblings, 1 reply; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-18 17:02 UTC (permalink / raw)
  To: Nicolas Schier
  Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci, Nicolas Schier

On Mon, Nov 18, 2024 at 11:47 PM Nicolas Schier <n.schier@avm.de> wrote:
>
> On Sun, Nov 10, 2024 at 10:34:33AM +0900, Masahiro Yamada wrote:
> > Currently, Kbuild always operates in the output directory of the kernel,
> > even when building external modules. This increases the risk of external
> > module Makefiles attempting to write to the kernel directory.
> >
> > This commit switches the working directory to the external module
> > directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> > some build artifacts.
> >
> > The command for building external modules maintains backward
> > compatibility, but Makefiles that rely on working in the kernel
> > directory may break. In such cases, $(objtree) and $(srctree) should
> > be used to refer to the output and source directories of the kernel.
> >
> > The appearance of the build log will change as follows:
> >
> > [Before]
> >
> >   $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >   make: Entering directory '/path/to/my/linux'
> >     CC [M]  /path/to/my/externel/module/helloworld.o
> >     MODPOST /path/to/my/externel/module/Module.symvers
> >     CC [M]  /path/to/my/externel/module/helloworld.mod.o
> >     CC [M]  /path/to/my/externel/module/.module-common.o
> >     LD [M]  /path/to/my/externel/module/helloworld.ko
> >   make: Leaving directory '/path/to/my/linux'
> >
> > [After]
> >
> >   $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >   make: Entering directory '/path/to/my/linux'
> >   make[1]: Entering directory '/path/to/my/externel/module'
> >     CC [M]  helloworld.o
> >     MODPOST Module.symvers
> >     CC [M]  helloworld.mod.o
> >     CC [M]  .module-common.o
> >     LD [M]  helloworld.ko
> >   make[1]: Leaving directory '/path/to/my/externel/module'
> >   make: Leaving directory '/path/to/my/linux'
> >
> > Printing "Entering directory" twice is cumbersome. This will be
> > addressed later.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > ---
> >
> > Changes in v2:
> >  - Introduce a new 'srcroot' variable and clean-up code
> >  - Reword Documentation/dev-tools/coccinelle.rst
> >
> >  Documentation/dev-tools/coccinelle.rst | 20 ++-----
> >  Documentation/kbuild/makefiles.rst     | 14 +++++
> >  Makefile                               | 80 +++++++++++++++-----------
> >  rust/Makefile                          |  4 +-
> >  scripts/Makefile.build                 |  2 +-
> >  scripts/Makefile.clean                 |  2 +-
> >  scripts/Makefile.compiler              |  2 +-
> >  scripts/Makefile.modpost               |  6 +-
> >  scripts/coccicheck                     |  6 +-
> >  scripts/nsdeps                         |  8 +--
> >  scripts/package/install-extmod-build   |  7 +++
> >  11 files changed, 85 insertions(+), 66 deletions(-)
> >
> > diff --git a/Documentation/dev-tools/coccinelle.rst b/Documentation/dev-tools/coccinelle.rst
> > index 535ce126fb4f..6e70a1e9a3c0 100644
> > --- a/Documentation/dev-tools/coccinelle.rst
> > +++ b/Documentation/dev-tools/coccinelle.rst
> > @@ -250,25 +250,17 @@ variables for .cocciconfig is as follows:
> >  - Your directory from which spatch is called is processed next
> >  - The directory provided with the ``--dir`` option is processed last, if used
> >
> > -Since coccicheck runs through make, it naturally runs from the kernel
> > -proper dir; as such the second rule above would be implied for picking up a
> > -.cocciconfig when using ``make coccicheck``.
> > -
> >  ``make coccicheck`` also supports using M= targets. If you do not supply
> >  any M= target, it is assumed you want to target the entire kernel.
> >  The kernel coccicheck script has::
> >
> > -    if [ "$KBUILD_EXTMOD" = "" ] ; then
> > -        OPTIONS="--dir $srctree $COCCIINCLUDE"
> > -    else
> > -        OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
> > -    fi
> > +    OPTIONS="--dir $srcroot $COCCIINCLUDE"
> >
> > -KBUILD_EXTMOD is set when an explicit target with M= is used. For both cases
> > -the spatch ``--dir`` argument is used, as such third rule applies when whether
> > -M= is used or not, and when M= is used the target directory can have its own
> > -.cocciconfig file. When M= is not passed as an argument to coccicheck the
> > -target directory is the same as the directory from where spatch was called.
> > +Here, $srcroot refers to the source directory of the target: it points to the
> > +external module's source directory when M= used, and otherwise, to the kernel
> > +source directory. The third rule ensures the spatch reads the .cocciconfig from
> > +the target directory, allowing external modules to have their own .cocciconfig
> > +file.
> >
> >  If not using the kernel's coccicheck target, keep the above precedence
> >  order logic of .cocciconfig reading. If using the kernel's coccicheck target,
> > diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
> > index 7964e0c245ae..d36519f194dc 100644
> > --- a/Documentation/kbuild/makefiles.rst
> > +++ b/Documentation/kbuild/makefiles.rst
> > @@ -449,6 +449,20 @@ $(obj)
> >    to prerequisites are referenced with $(src) (because they are not
> >    generated files).
> >
> > +$(srcroot)
> > +  $(srcroot) refers to the root of the source you are building, which can be
> > +  either the kernel source or the external modules source, depending on whether
> > +  KBUILD_EXTMOD is set. This can be either a relative or an absolute path, but
> > +  if KBUILD_ABS_SRCTREE=1 is set, it is always an absolute path.
> > +
> > +$(srctree)
> > +  $(srctree) refers to the root of the kernel source tree. When building the
> > +  kernel, this is the same as $(srcroot).
> > +
> > +$(objtree)
> > +  $(objtree) refers to the root of the kernel object tree. It is ``.`` when
> > +  building the kernel, but it is different when building external modules.
> > +
>
> Thanks, I think it's nice that there is now such a clear definition.
> $(srcroot) sounds fine to me.
>
> >  $(kecho)
> >    echoing information to user in a rule is often a good practice
> >    but when execution ``make -s`` one does not expect to see any output
> > diff --git a/Makefile b/Makefile
> > index cf1d55560ae2..e5f7ac7647a7 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -180,7 +180,24 @@ ifeq ("$(origin O)", "command line")
> >    KBUILD_OUTPUT := $(O)
> >  endif
> >
> > -output := $(KBUILD_OUTPUT)
> > +ifdef KBUILD_EXTMOD
> > +    ifdef KBUILD_OUTPUT
> > +        objtree := $(realpath $(KBUILD_OUTPUT))
> > +        $(if $(objtree),,$(error specified kernel directory "$(KBUILD_OUTPUT)" does not exist))
> > +    else
> > +        objtree := $(CURDIR)
> > +    endif
> > +    output := $(KBUILD_EXTMOD)
> > +    # KBUILD_EXTMOD might be a relative path. Remember its absolute path before
> > +    # Make changes the working directory.
> > +    srcroot := $(realpath $(KBUILD_EXTMOD))
> > +    $(if $(srcroot),,$(error specified external module directory "$(KBUILD_EXTMOD)" does not exist))
> > +else
> > +    objtree := .
> > +    output := $(KBUILD_OUTPUT)
> > +endif
> > +
> > +export objtree srcroot
> >
> >  # Do we want to change the working directory?
> >  ifneq ($(output),)
> > @@ -230,35 +247,33 @@ else # need-sub-make
> >
> >  # We process the rest of the Makefile if this is the final invocation of make
> >
> > -ifeq ($(abs_srctree),$(CURDIR))
> > -        # building in the source tree
> > -        srctree := .
> > -     building_out_of_srctree :=
> > +ifndef KBUILD_EXTMOD
> > +srcroot := $(abs_srctree)
> > +endif
> > +
> > +ifeq ($(srcroot),$(CURDIR))
> > +building_out_of_srctree :=
> >  else
> > -        ifeq ($(abs_srctree)/,$(dir $(CURDIR)))
> > -                # building in a subdirectory of the source tree
> > -                srctree := ..
> > -        else
> > -                srctree := $(abs_srctree)
> > -        endif
> > -     building_out_of_srctree := 1
> > +export building_out_of_srctree :=1
> >  endif
> >
> > -ifneq ($(KBUILD_ABS_SRCTREE),)
> > -srctree := $(abs_srctree)
> > +ifdef KBUILD_ABS_SRCTREE
> > +    # Do not nothing. Use the absolute path.
> > +else ifeq ($(srcroot),$(CURDIR))
> > +    # Building in the source.
> > +    srcroot := .
> > +else ifeq ($(srcroot)/,$(dir $(CURDIR)))
> > +    # Building in a subdirectory of the source.
> > +    srcroot := ..
> >  endif
> >
> > -objtree              := .
> > +export srctree := $(if $(KBUILD_EXTMOD),$(abs_srctree),$(srcroot))
>
> With this patch applied, the following breaks for me:
>
>     $ make O=build M=fs/btrfs CONFIG_BTRFS_FS=m
>     make[1]: Entering directory '/data/linux/kbuild-review/fs/btrfs'
>       CC [M]  super.o
>     In file included from <command-line>:
>     /data/linux/kbuild-review/include/linux/compiler_types.h:89:10: fatal error: linux/compiler_attributes.h: No such file or directory
>        89 | #include <linux/compiler_attributes.h>
>           |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>     compilation terminated.
>
> Adding 'ccflags-y += -I$(srctree)/include' to fs/btrfs/Makefile breaks
> the build loudly.  I could make it build again with
>
> diff --git a/Makefile b/Makefile
> index e5f7ac7647a7b..3d95911f1a68f 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -555,7 +555,7 @@ USERINCLUDE    := \
>  LINUXINCLUDE    := \
>                 -I$(srctree)/arch/$(SRCARCH)/include \
>                 -I$(objtree)/arch/$(SRCARCH)/include/generated \
> -               $(if $(building_out_of_srctree),-I$(srctree)/include) \
> +               $(if $(or $(building_out_of_srctree),$(filter $(srctree)/%, $(CURDIR))),-I$(srctree)/include) \
>                 -I$(objtree)/include \
>                 $(USERINCLUDE)
>
> but this does not feel good.  It building in-tree modules in this way a
> valid thing to do?

Yes, it is a valid way.

This got broken with this commit, and fixed by the later commit,
"kbuild: support building external modules in a separate build directory".

I will move the change for LINUXINCLUDE to this commit.

Thanks for comprehensive testing!

-- 
Best Regards
Masahiro Yamada

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-11-18 17:02     ` Masahiro Yamada
@ 2024-11-27 15:29       ` Nicolas Schier
  2024-11-27 23:15         ` Masahiro Yamada
  0 siblings, 1 reply; 33+ messages in thread
From: Nicolas Schier @ 2024-11-27 15:29 UTC (permalink / raw)
  To: Masahiro Yamada; +Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci

On Tue, Nov 19, 2024 at 02:02:05AM +0900, Masahiro Yamada wrote:
> On Mon, Nov 18, 2024 at 11:47 PM Nicolas Schier <n.schier@avm.de> wrote:
> >
> > On Sun, Nov 10, 2024 at 10:34:33AM +0900, Masahiro Yamada wrote:
> > > Currently, Kbuild always operates in the output directory of the kernel,
> > > even when building external modules. This increases the risk of external
> > > module Makefiles attempting to write to the kernel directory.
> > >
> > > This commit switches the working directory to the external module
> > > directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> > > some build artifacts.
> > >
> > > The command for building external modules maintains backward
> > > compatibility, but Makefiles that rely on working in the kernel
> > > directory may break. In such cases, $(objtree) and $(srctree) should
> > > be used to refer to the output and source directories of the kernel.
> > >
> > > The appearance of the build log will change as follows:
> > >
> > > [Before]
> > >
> > >   $ make -C /path/to/my/linux M=/path/to/my/externel/module
> > >   make: Entering directory '/path/to/my/linux'
> > >     CC [M]  /path/to/my/externel/module/helloworld.o
> > >     MODPOST /path/to/my/externel/module/Module.symvers
> > >     CC [M]  /path/to/my/externel/module/helloworld.mod.o
> > >     CC [M]  /path/to/my/externel/module/.module-common.o
> > >     LD [M]  /path/to/my/externel/module/helloworld.ko
> > >   make: Leaving directory '/path/to/my/linux'
> > >
> > > [After]
> > >
> > >   $ make -C /path/to/my/linux M=/path/to/my/externel/module
> > >   make: Entering directory '/path/to/my/linux'
> > >   make[1]: Entering directory '/path/to/my/externel/module'
> > >     CC [M]  helloworld.o
> > >     MODPOST Module.symvers
> > >     CC [M]  helloworld.mod.o
> > >     CC [M]  .module-common.o
> > >     LD [M]  helloworld.ko
> > >   make[1]: Leaving directory '/path/to/my/externel/module'
> > >   make: Leaving directory '/path/to/my/linux'
> > >
> > > Printing "Entering directory" twice is cumbersome. This will be
> > > addressed later.
> > >
> > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > > ---
> > >
> > > Changes in v2:
> > >  - Introduce a new 'srcroot' variable and clean-up code
> > >  - Reword Documentation/dev-tools/coccinelle.rst
> > >
> > >  Documentation/dev-tools/coccinelle.rst | 20 ++-----
> > >  Documentation/kbuild/makefiles.rst     | 14 +++++
> > >  Makefile                               | 80 +++++++++++++++-----------
> > >  rust/Makefile                          |  4 +-
> > >  scripts/Makefile.build                 |  2 +-
> > >  scripts/Makefile.clean                 |  2 +-
> > >  scripts/Makefile.compiler              |  2 +-
> > >  scripts/Makefile.modpost               |  6 +-
> > >  scripts/coccicheck                     |  6 +-
> > >  scripts/nsdeps                         |  8 +--
> > >  scripts/package/install-extmod-build   |  7 +++
> > >  11 files changed, 85 insertions(+), 66 deletions(-)
> > >
> > > diff --git a/Documentation/dev-tools/coccinelle.rst b/Documentation/dev-tools/coccinelle.rst
> > > index 535ce126fb4f..6e70a1e9a3c0 100644
> > > --- a/Documentation/dev-tools/coccinelle.rst
> > > +++ b/Documentation/dev-tools/coccinelle.rst
> > > @@ -250,25 +250,17 @@ variables for .cocciconfig is as follows:
> > >  - Your directory from which spatch is called is processed next
> > >  - The directory provided with the ``--dir`` option is processed last, if used
> > >
> > > -Since coccicheck runs through make, it naturally runs from the kernel
> > > -proper dir; as such the second rule above would be implied for picking up a
> > > -.cocciconfig when using ``make coccicheck``.
> > > -
> > >  ``make coccicheck`` also supports using M= targets. If you do not supply
> > >  any M= target, it is assumed you want to target the entire kernel.
> > >  The kernel coccicheck script has::
> > >
> > > -    if [ "$KBUILD_EXTMOD" = "" ] ; then
> > > -        OPTIONS="--dir $srctree $COCCIINCLUDE"
> > > -    else
> > > -        OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
> > > -    fi
> > > +    OPTIONS="--dir $srcroot $COCCIINCLUDE"
> > >
> > > -KBUILD_EXTMOD is set when an explicit target with M= is used. For both cases
> > > -the spatch ``--dir`` argument is used, as such third rule applies when whether
> > > -M= is used or not, and when M= is used the target directory can have its own
> > > -.cocciconfig file. When M= is not passed as an argument to coccicheck the
> > > -target directory is the same as the directory from where spatch was called.
> > > +Here, $srcroot refers to the source directory of the target: it points to the
> > > +external module's source directory when M= used, and otherwise, to the kernel
> > > +source directory. The third rule ensures the spatch reads the .cocciconfig from
> > > +the target directory, allowing external modules to have their own .cocciconfig
> > > +file.
> > >
> > >  If not using the kernel's coccicheck target, keep the above precedence
> > >  order logic of .cocciconfig reading. If using the kernel's coccicheck target,
> > > diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
> > > index 7964e0c245ae..d36519f194dc 100644
> > > --- a/Documentation/kbuild/makefiles.rst
> > > +++ b/Documentation/kbuild/makefiles.rst
> > > @@ -449,6 +449,20 @@ $(obj)
> > >    to prerequisites are referenced with $(src) (because they are not
> > >    generated files).
> > >
> > > +$(srcroot)
> > > +  $(srcroot) refers to the root of the source you are building, which can be
> > > +  either the kernel source or the external modules source, depending on whether
> > > +  KBUILD_EXTMOD is set. This can be either a relative or an absolute path, but
> > > +  if KBUILD_ABS_SRCTREE=1 is set, it is always an absolute path.
> > > +
> > > +$(srctree)
> > > +  $(srctree) refers to the root of the kernel source tree. When building the
> > > +  kernel, this is the same as $(srcroot).
> > > +
> > > +$(objtree)
> > > +  $(objtree) refers to the root of the kernel object tree. It is ``.`` when
> > > +  building the kernel, but it is different when building external modules.
> > > +
> >
> > Thanks, I think it's nice that there is now such a clear definition.
> > $(srcroot) sounds fine to me.
> >
> > >  $(kecho)
> > >    echoing information to user in a rule is often a good practice
> > >    but when execution ``make -s`` one does not expect to see any output
> > > diff --git a/Makefile b/Makefile
> > > index cf1d55560ae2..e5f7ac7647a7 100644
> > > --- a/Makefile
> > > +++ b/Makefile
> > > @@ -180,7 +180,24 @@ ifeq ("$(origin O)", "command line")
> > >    KBUILD_OUTPUT := $(O)
> > >  endif
> > >
> > > -output := $(KBUILD_OUTPUT)
> > > +ifdef KBUILD_EXTMOD
> > > +    ifdef KBUILD_OUTPUT
> > > +        objtree := $(realpath $(KBUILD_OUTPUT))
> > > +        $(if $(objtree),,$(error specified kernel directory "$(KBUILD_OUTPUT)" does not exist))
> > > +    else
> > > +        objtree := $(CURDIR)
> > > +    endif
> > > +    output := $(KBUILD_EXTMOD)
> > > +    # KBUILD_EXTMOD might be a relative path. Remember its absolute path before
> > > +    # Make changes the working directory.
> > > +    srcroot := $(realpath $(KBUILD_EXTMOD))
> > > +    $(if $(srcroot),,$(error specified external module directory "$(KBUILD_EXTMOD)" does not exist))
> > > +else
> > > +    objtree := .
> > > +    output := $(KBUILD_OUTPUT)
> > > +endif
> > > +
> > > +export objtree srcroot
> > >
> > >  # Do we want to change the working directory?
> > >  ifneq ($(output),)
> > > @@ -230,35 +247,33 @@ else # need-sub-make
> > >
> > >  # We process the rest of the Makefile if this is the final invocation of make
> > >
> > > -ifeq ($(abs_srctree),$(CURDIR))
> > > -        # building in the source tree
> > > -        srctree := .
> > > -     building_out_of_srctree :=
> > > +ifndef KBUILD_EXTMOD
> > > +srcroot := $(abs_srctree)
> > > +endif
> > > +
> > > +ifeq ($(srcroot),$(CURDIR))
> > > +building_out_of_srctree :=
> > >  else
> > > -        ifeq ($(abs_srctree)/,$(dir $(CURDIR)))
> > > -                # building in a subdirectory of the source tree
> > > -                srctree := ..
> > > -        else
> > > -                srctree := $(abs_srctree)
> > > -        endif
> > > -     building_out_of_srctree := 1
> > > +export building_out_of_srctree :=1

Nit: Adding a space between ':=1' for consistency?

> > >  endif
> > >
> > > -ifneq ($(KBUILD_ABS_SRCTREE),)
> > > -srctree := $(abs_srctree)
> > > +ifdef KBUILD_ABS_SRCTREE
> > > +    # Do not nothing. Use the absolute path.

Is this a superfluous "not"?

"Do nothing. Use the absolute path."?

> > > +else ifeq ($(srcroot),$(CURDIR))
> > > +    # Building in the source.
> > > +    srcroot := .
> > > +else ifeq ($(srcroot)/,$(dir $(CURDIR)))
> > > +    # Building in a subdirectory of the source.
> > > +    srcroot := ..
> > >  endif
> > >
> > > -objtree              := .
> > > +export srctree := $(if $(KBUILD_EXTMOD),$(abs_srctree),$(srcroot))
> >
> > With this patch applied, the following breaks for me:
> >
> >     $ make O=build M=fs/btrfs CONFIG_BTRFS_FS=m
> >     make[1]: Entering directory '/data/linux/kbuild-review/fs/btrfs'
> >       CC [M]  super.o
> >     In file included from <command-line>:
> >     /data/linux/kbuild-review/include/linux/compiler_types.h:89:10: fatal error: linux/compiler_attributes.h: No such file or directory
> >        89 | #include <linux/compiler_attributes.h>
> >           |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >     compilation terminated.
> >
> > Adding 'ccflags-y += -I$(srctree)/include' to fs/btrfs/Makefile breaks
> > the build loudly.  I could make it build again with
> >
> > diff --git a/Makefile b/Makefile
> > index e5f7ac7647a7b..3d95911f1a68f 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -555,7 +555,7 @@ USERINCLUDE    := \
> >  LINUXINCLUDE    := \
> >                 -I$(srctree)/arch/$(SRCARCH)/include \
> >                 -I$(objtree)/arch/$(SRCARCH)/include/generated \
> > -               $(if $(building_out_of_srctree),-I$(srctree)/include) \
> > +               $(if $(or $(building_out_of_srctree),$(filter $(srctree)/%, $(CURDIR))),-I$(srctree)/include) \
> >                 -I$(objtree)/include \
> >                 $(USERINCLUDE)
> >
> > but this does not feel good.  It building in-tree modules in this way a
> > valid thing to do?
> 
> Yes, it is a valid way.
> 
> This got broken with this commit, and fixed by the later commit,
> "kbuild: support building external modules in a separate build directory".
> 
> I will move the change for LINUXINCLUDE to this commit.

ah, thanks.  I should have seen that.

> > -VPATH		:=
> > -
> > -ifeq ($(KBUILD_EXTMOD),)
> >  ifdef building_out_of_srctree
> > -VPATH		:= $(srctree)
> > +export VPATH := $(srcroot)
> > +else
> > +VPATH :=
> >  endif
> > -endif
> > -
> > -export building_out_of_srctree srctree objtree VPATH
> >  
> >  # To make sure we do not include .config for any of the *config targets
> >  # catch them early, and hand them over to scripts/kconfig/Makefile
> > @@ -711,7 +726,7 @@ endif
> >  # in addition to whatever we do anyway.
> >  # Just "make" or "make all" shall build modules as well
> >  
> > -ifneq ($(filter all modules nsdeps %compile_commands.json clang-%,$(MAKECMDGOALS)),)
> > +ifneq ($(filter all modules nsdeps compile_commands.json clang-%,$(MAKECMDGOALS)),)
> >    KBUILD_MODULES := 1
> >  endif
> >  
> > @@ -1107,7 +1122,7 @@ export MODLIB
> >  
> >  PHONY += prepare0
> >  
> > -export extmod_prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)
> > +export extmod_prefix =
> >  export MODORDER := $(extmod_prefix)modules.order
> >  export MODULES_NSDEPS := $(extmod_prefix)modules.nsdeps
> >  
> > @@ -1799,14 +1814,10 @@ filechk_kernel.release = echo $(KERNELRELEASE)
> >  KBUILD_BUILTIN :=
> >  KBUILD_MODULES := 1
> >  
> > -build-dir := $(KBUILD_EXTMOD)
> > +build-dir := .
> >  
> > -compile_commands.json: $(extmod_prefix)compile_commands.json
> > -PHONY += compile_commands.json
> > -
> > -clean-dirs := $(KBUILD_EXTMOD)
> > -clean: private rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps \
> > -	$(KBUILD_EXTMOD)/compile_commands.json
> > +clean-dirs := .
> > +clean: private rm-files := Module.symvers modules.nsdeps compile_commands.json
> >  
> >  PHONY += prepare
> >  # now expand this into a simple variable to reduce the cost of shell evaluations
> > @@ -1948,7 +1959,7 @@ $(clean-dirs):
> >  
> >  clean: $(clean-dirs)
> >  	$(call cmd,rmfiles)
> > -	@find $(or $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
> > +	@find . $(RCS_FIND_IGNORE) \
> >  		\( -name '*.[aios]' -o -name '*.rsi' -o -name '*.ko' -o -name '.*.cmd' \
> >  		-o -name '*.ko.*' \
> >  		-o -name '*.dtb' -o -name '*.dtbo' \
> > @@ -1981,7 +1992,12 @@ tags TAGS cscope gtags: FORCE
> >  PHONY += rust-analyzer
> >  rust-analyzer:
> >  	+$(Q)$(CONFIG_SHELL) $(srctree)/scripts/rust_is_available.sh
> > +ifdef KBUILD_EXTMOD
> > +# FIXME: external modules must not descend into a sub-directory of the kernel
> > +	$(Q)$(MAKE) $(build)=$(objtree)/rust src=$(srctree)/rust $@
> > +else
> >  	$(Q)$(MAKE) $(build)=rust $@
> > +endif
> >  
> >  # Script to generate missing namespace dependencies
> >  # ---------------------------------------------------------------------------
> > diff --git a/rust/Makefile b/rust/Makefile
> > index b5e0a73b78f3..742740816c4b 100644
> > --- a/rust/Makefile
> > +++ b/rust/Makefile
> > @@ -362,8 +362,8 @@ rust-analyzer:
> >  	$(Q)$(srctree)/scripts/generate_rust_analyzer.py \
> >  		--cfgs='core=$(core-cfgs)' --cfgs='alloc=$(alloc-cfgs)' \
> >  		$(realpath $(srctree)) $(realpath $(objtree)) \
> > -		$(rustc_sysroot) $(RUST_LIB_SRC) $(KBUILD_EXTMOD) > \
> > -		$(if $(KBUILD_EXTMOD),$(extmod_prefix),$(objtree))/rust-project.json
> > +		$(rustc_sysroot) $(RUST_LIB_SRC) $(if $(KBUILD_EXTMOD),$(srcroot)) \
> > +		> rust-project.json
> >  
> >  redirect-intrinsics = \
> >  	__addsf3 __eqsf2 __extendsfdf2 __gesf2 __lesf2 __ltsf2 __mulsf3 __nesf2 __truncdfsf2 __unordsf2 \
> > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > index 64cd046f8fd8..1aa928a6fb4f 100644
> > --- a/scripts/Makefile.build
> > +++ b/scripts/Makefile.build
> > @@ -3,7 +3,7 @@
> >  # Building
> >  # ==========================================================================
> >  
> > -src := $(if $(VPATH),$(VPATH)/)$(obj)
> > +src := $(srcroot)/$(obj)
> >  
> >  PHONY := $(obj)/
> >  $(obj)/:
> > diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean
> > index 4fcfab40ed61..6ead00ec7313 100644
> > --- a/scripts/Makefile.clean
> > +++ b/scripts/Makefile.clean
> > @@ -3,7 +3,7 @@
> >  # Cleaning up
> >  # ==========================================================================
> >  
> > -src := $(if $(VPATH),$(VPATH)/)$(obj)
> > +src := $(srcroot)/$(obj)
> >  
> >  PHONY := __clean
> >  __clean:
> > diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
> > index e0842496d26e..8c1029687e2e 100644
> > --- a/scripts/Makefile.compiler
> > +++ b/scripts/Makefile.compiler
> > @@ -13,7 +13,7 @@ cc-cross-prefix = $(firstword $(foreach c, $(1), \
> >  			$(if $(shell command -v -- $(c)gcc 2>/dev/null), $(c))))
> >  
> >  # output directory for tests below
> > -TMPOUT = $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/).tmp_$$$$
> > +TMPOUT = .tmp_$$$$
> >  
> >  # try-run
> >  # Usage: option = $(call try-run, $(CC)...-o "$$TMP",option-ok,otherwise)
> > diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
> > index 12e7c15d099c..78d2ca4f25f5 100644
> > --- a/scripts/Makefile.modpost
> > +++ b/scripts/Makefile.modpost
> > @@ -111,13 +111,13 @@ endif
> >  else
> >  
> >  # set src + obj - they may be used in the modules's Makefile
> > -obj := $(KBUILD_EXTMOD)
> > -src := $(if $(VPATH),$(VPATH)/)$(obj)
> > +obj := .
> > +src := $(srcroot)
> >  
> >  # Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS
> >  include $(kbuild-file)
> >  
> > -output-symdump := $(KBUILD_EXTMOD)/Module.symvers
> > +output-symdump := Module.symvers
> >  
> >  ifeq ($(wildcard $(objtree)/Module.symvers),)
> >  missing-input := $(objtree)/Module.symvers
> > diff --git a/scripts/coccicheck b/scripts/coccicheck
> > index e52cb43fede6..0e6bc5a10320 100755
> > --- a/scripts/coccicheck
> > +++ b/scripts/coccicheck
> > @@ -80,11 +80,7 @@ command results in a shift count error.'
> >      NPROC=1
> >  else
> >      ONLINE=0
> > -    if [ "$KBUILD_EXTMOD" = "" ] ; then
> > -        OPTIONS="--dir $srctree $COCCIINCLUDE"
> > -    else
> > -        OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
> > -    fi
> > +    OPTIONS="--dir $srcroot $COCCIINCLUDE"
> >  
> >      # Use only one thread per core by default if hyperthreading is enabled
> >      THREADS_PER_CORE=$(LANG=C lscpu | grep "Thread(s) per core: " | tr -cd "[:digit:]")
> > diff --git a/scripts/nsdeps b/scripts/nsdeps
> > index f1718cc0d700..8ca12e2b5c03 100644
> > --- a/scripts/nsdeps
> > +++ b/scripts/nsdeps
> > @@ -19,12 +19,6 @@ if ! { echo "$SPATCH_REQ_VERSION"; echo "$SPATCH_VERSION"; } | sort -CV ; then
> >  	exit 1
> >  fi
> >  
> > -if [ "$KBUILD_EXTMOD" ]; then
> > -	src_prefix=
> > -else
> > -	src_prefix=$srctree/
> > -fi
> > -
> >  generate_deps_for_ns() {
> >  	$SPATCH --very-quiet --in-place --sp-file \
> >  		$srctree/scripts/coccinelle/misc/add_namespace.cocci -D nsdeps -D ns=$1 $2
> > @@ -34,7 +28,7 @@ generate_deps() {
> >  	local mod=${1%.ko:}
> >  	shift
> >  	local namespaces="$*"
> > -	local mod_source_files=$(sed "s|^\(.*\)\.o$|${src_prefix}\1.c|" $mod.mod)
> > +	local mod_source_files=$(sed "s|^\(.*\)\.o$|${srcroot}/\1.c|" $mod.mod)
> >  
> >  	for ns in $namespaces; do
> >  		echo "Adding namespace $ns to module $mod.ko."
> > diff --git a/scripts/package/install-extmod-build b/scripts/package/install-extmod-build
> > index 7ec1f061a519..64d958ee45f3 100755
> > --- a/scripts/package/install-extmod-build
> > +++ b/scripts/package/install-extmod-build
> > @@ -51,6 +51,13 @@ mkdir -p "${destdir}"
> >  if [ "${CC}" != "${HOSTCC}" ]; then
> >  	echo "Rebuilding host programs with ${CC}..."
> >  
> > +	# This leverages external module building.
> > +	# - Clear sub_make_done to allow the top-level Makefile to redo sub-make.
> > +	# - Filter out --no-print-directory to print "Entering directory" logs
> > +	#   when Make changes the working directory.
> > +	unset sub_make_done
> > +	MAKEFLAGS=$(echo "${MAKEFLAGS}" | sed s/--no-print-directory//)
> > +
> >  	cat <<-'EOF' >  "${destdir}/Kbuild"
> >  	subdir-y := scripts
> >  	EOF
> > -- 
> > 2.43.0


Thanks, again!

Reviewed-by: Nicolas Schier <n.schier@avm.de>

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-11-27 15:29       ` Nicolas Schier
@ 2024-11-27 23:15         ` Masahiro Yamada
  0 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-27 23:15 UTC (permalink / raw)
  To: Nicolas Schier; +Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci

On Thu, Nov 28, 2024 at 12:29 AM Nicolas Schier <n.schier@avm.de> wrote:
>
> On Tue, Nov 19, 2024 at 02:02:05AM +0900, Masahiro Yamada wrote:
> > On Mon, Nov 18, 2024 at 11:47 PM Nicolas Schier <n.schier@avm.de> wrote:
> > >
> > > On Sun, Nov 10, 2024 at 10:34:33AM +0900, Masahiro Yamada wrote:
> > > > Currently, Kbuild always operates in the output directory of the kernel,
> > > > even when building external modules. This increases the risk of external
> > > > module Makefiles attempting to write to the kernel directory.
> > > >
> > > > This commit switches the working directory to the external module
> > > > directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> > > > some build artifacts.
> > > >
> > > > The command for building external modules maintains backward
> > > > compatibility, but Makefiles that rely on working in the kernel
> > > > directory may break. In such cases, $(objtree) and $(srctree) should
> > > > be used to refer to the output and source directories of the kernel.
> > > >
> > > > The appearance of the build log will change as follows:
> > > >
> > > > [Before]
> > > >
> > > >   $ make -C /path/to/my/linux M=/path/to/my/externel/module
> > > >   make: Entering directory '/path/to/my/linux'
> > > >     CC [M]  /path/to/my/externel/module/helloworld.o
> > > >     MODPOST /path/to/my/externel/module/Module.symvers
> > > >     CC [M]  /path/to/my/externel/module/helloworld.mod.o
> > > >     CC [M]  /path/to/my/externel/module/.module-common.o
> > > >     LD [M]  /path/to/my/externel/module/helloworld.ko
> > > >   make: Leaving directory '/path/to/my/linux'
> > > >
> > > > [After]
> > > >
> > > >   $ make -C /path/to/my/linux M=/path/to/my/externel/module
> > > >   make: Entering directory '/path/to/my/linux'
> > > >   make[1]: Entering directory '/path/to/my/externel/module'
> > > >     CC [M]  helloworld.o
> > > >     MODPOST Module.symvers
> > > >     CC [M]  helloworld.mod.o
> > > >     CC [M]  .module-common.o
> > > >     LD [M]  helloworld.ko
> > > >   make[1]: Leaving directory '/path/to/my/externel/module'
> > > >   make: Leaving directory '/path/to/my/linux'
> > > >
> > > > Printing "Entering directory" twice is cumbersome. This will be
> > > > addressed later.
> > > >
> > > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > > > ---
> > > >
> > > > Changes in v2:
> > > >  - Introduce a new 'srcroot' variable and clean-up code
> > > >  - Reword Documentation/dev-tools/coccinelle.rst
> > > >
> > > >  Documentation/dev-tools/coccinelle.rst | 20 ++-----
> > > >  Documentation/kbuild/makefiles.rst     | 14 +++++
> > > >  Makefile                               | 80 +++++++++++++++-----------
> > > >  rust/Makefile                          |  4 +-
> > > >  scripts/Makefile.build                 |  2 +-
> > > >  scripts/Makefile.clean                 |  2 +-
> > > >  scripts/Makefile.compiler              |  2 +-
> > > >  scripts/Makefile.modpost               |  6 +-
> > > >  scripts/coccicheck                     |  6 +-
> > > >  scripts/nsdeps                         |  8 +--
> > > >  scripts/package/install-extmod-build   |  7 +++
> > > >  11 files changed, 85 insertions(+), 66 deletions(-)
> > > >
> > > > diff --git a/Documentation/dev-tools/coccinelle.rst b/Documentation/dev-tools/coccinelle.rst
> > > > index 535ce126fb4f..6e70a1e9a3c0 100644
> > > > --- a/Documentation/dev-tools/coccinelle.rst
> > > > +++ b/Documentation/dev-tools/coccinelle.rst
> > > > @@ -250,25 +250,17 @@ variables for .cocciconfig is as follows:
> > > >  - Your directory from which spatch is called is processed next
> > > >  - The directory provided with the ``--dir`` option is processed last, if used
> > > >
> > > > -Since coccicheck runs through make, it naturally runs from the kernel
> > > > -proper dir; as such the second rule above would be implied for picking up a
> > > > -.cocciconfig when using ``make coccicheck``.
> > > > -
> > > >  ``make coccicheck`` also supports using M= targets. If you do not supply
> > > >  any M= target, it is assumed you want to target the entire kernel.
> > > >  The kernel coccicheck script has::
> > > >
> > > > -    if [ "$KBUILD_EXTMOD" = "" ] ; then
> > > > -        OPTIONS="--dir $srctree $COCCIINCLUDE"
> > > > -    else
> > > > -        OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
> > > > -    fi
> > > > +    OPTIONS="--dir $srcroot $COCCIINCLUDE"
> > > >
> > > > -KBUILD_EXTMOD is set when an explicit target with M= is used. For both cases
> > > > -the spatch ``--dir`` argument is used, as such third rule applies when whether
> > > > -M= is used or not, and when M= is used the target directory can have its own
> > > > -.cocciconfig file. When M= is not passed as an argument to coccicheck the
> > > > -target directory is the same as the directory from where spatch was called.
> > > > +Here, $srcroot refers to the source directory of the target: it points to the
> > > > +external module's source directory when M= used, and otherwise, to the kernel
> > > > +source directory. The third rule ensures the spatch reads the .cocciconfig from
> > > > +the target directory, allowing external modules to have their own .cocciconfig
> > > > +file.
> > > >
> > > >  If not using the kernel's coccicheck target, keep the above precedence
> > > >  order logic of .cocciconfig reading. If using the kernel's coccicheck target,
> > > > diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
> > > > index 7964e0c245ae..d36519f194dc 100644
> > > > --- a/Documentation/kbuild/makefiles.rst
> > > > +++ b/Documentation/kbuild/makefiles.rst
> > > > @@ -449,6 +449,20 @@ $(obj)
> > > >    to prerequisites are referenced with $(src) (because they are not
> > > >    generated files).
> > > >
> > > > +$(srcroot)
> > > > +  $(srcroot) refers to the root of the source you are building, which can be
> > > > +  either the kernel source or the external modules source, depending on whether
> > > > +  KBUILD_EXTMOD is set. This can be either a relative or an absolute path, but
> > > > +  if KBUILD_ABS_SRCTREE=1 is set, it is always an absolute path.
> > > > +
> > > > +$(srctree)
> > > > +  $(srctree) refers to the root of the kernel source tree. When building the
> > > > +  kernel, this is the same as $(srcroot).
> > > > +
> > > > +$(objtree)
> > > > +  $(objtree) refers to the root of the kernel object tree. It is ``.`` when
> > > > +  building the kernel, but it is different when building external modules.
> > > > +
> > >
> > > Thanks, I think it's nice that there is now such a clear definition.
> > > $(srcroot) sounds fine to me.
> > >
> > > >  $(kecho)
> > > >    echoing information to user in a rule is often a good practice
> > > >    but when execution ``make -s`` one does not expect to see any output
> > > > diff --git a/Makefile b/Makefile
> > > > index cf1d55560ae2..e5f7ac7647a7 100644
> > > > --- a/Makefile
> > > > +++ b/Makefile
> > > > @@ -180,7 +180,24 @@ ifeq ("$(origin O)", "command line")
> > > >    KBUILD_OUTPUT := $(O)
> > > >  endif
> > > >
> > > > -output := $(KBUILD_OUTPUT)
> > > > +ifdef KBUILD_EXTMOD
> > > > +    ifdef KBUILD_OUTPUT
> > > > +        objtree := $(realpath $(KBUILD_OUTPUT))
> > > > +        $(if $(objtree),,$(error specified kernel directory "$(KBUILD_OUTPUT)" does not exist))
> > > > +    else
> > > > +        objtree := $(CURDIR)
> > > > +    endif
> > > > +    output := $(KBUILD_EXTMOD)
> > > > +    # KBUILD_EXTMOD might be a relative path. Remember its absolute path before
> > > > +    # Make changes the working directory.
> > > > +    srcroot := $(realpath $(KBUILD_EXTMOD))
> > > > +    $(if $(srcroot),,$(error specified external module directory "$(KBUILD_EXTMOD)" does not exist))
> > > > +else
> > > > +    objtree := .
> > > > +    output := $(KBUILD_OUTPUT)
> > > > +endif
> > > > +
> > > > +export objtree srcroot
> > > >
> > > >  # Do we want to change the working directory?
> > > >  ifneq ($(output),)
> > > > @@ -230,35 +247,33 @@ else # need-sub-make
> > > >
> > > >  # We process the rest of the Makefile if this is the final invocation of make
> > > >
> > > > -ifeq ($(abs_srctree),$(CURDIR))
> > > > -        # building in the source tree
> > > > -        srctree := .
> > > > -     building_out_of_srctree :=
> > > > +ifndef KBUILD_EXTMOD
> > > > +srcroot := $(abs_srctree)
> > > > +endif
> > > > +
> > > > +ifeq ($(srcroot),$(CURDIR))
> > > > +building_out_of_srctree :=
> > > >  else
> > > > -        ifeq ($(abs_srctree)/,$(dir $(CURDIR)))
> > > > -                # building in a subdirectory of the source tree
> > > > -                srctree := ..
> > > > -        else
> > > > -                srctree := $(abs_srctree)
> > > > -        endif
> > > > -     building_out_of_srctree := 1
> > > > +export building_out_of_srctree :=1
>
> Nit: Adding a space between ':=1' for consistency?
>
> > > >  endif
> > > >
> > > > -ifneq ($(KBUILD_ABS_SRCTREE),)
> > > > -srctree := $(abs_srctree)
> > > > +ifdef KBUILD_ABS_SRCTREE
> > > > +    # Do not nothing. Use the absolute path.
>
> Is this a superfluous "not"?
>
> "Do nothing. Use the absolute path."?


Thanks. I folded both.



>
>
> Thanks, again!
>
> Reviewed-by: Nicolas Schier <n.schier@avm.de>

Thanks for the review!


-- 
Best Regards
Masahiro Yamada

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-11-10  1:34 ` [PATCH v2 05/11] kbuild: change working directory to external module directory with M= Masahiro Yamada
  2024-11-18 14:47   ` Nicolas Schier
@ 2024-12-04 20:51   ` Alison Schofield
  2024-12-05  2:33     ` Masahiro Yamada
  2024-12-04 23:35   ` Charlie Jenkins
                     ` (3 subsequent siblings)
  5 siblings, 1 reply; 33+ messages in thread
From: Alison Schofield @ 2024-12-04 20:51 UTC (permalink / raw)
  To: Masahiro Yamada
  Cc: Vishal Verma, Ira Weiny, linux-kbuild, linux-kernel,
	rust-for-linux, cocci

On Sun, Nov 10, 2024 at 10:34:33AM +0900, Masahiro Yamada wrote:
> Currently, Kbuild always operates in the output directory of the kernel,
> even when building external modules. This increases the risk of external
> module Makefiles attempting to write to the kernel directory.
> 
> This commit switches the working directory to the external module
> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> some build artifacts.
> 
> The command for building external modules maintains backward
> compatibility, but Makefiles that rely on working in the kernel
> directory may break. In such cases, $(objtree) and $(srctree) should
> be used to refer to the output and source directories of the kernel.
> 
> The appearance of the build log will change as follows:
> 
> [Before]
> 
>   $ make -C /path/to/my/linux M=/path/to/my/externel/module
>   make: Entering directory '/path/to/my/linux'
>     CC [M]  /path/to/my/externel/module/helloworld.o
>     MODPOST /path/to/my/externel/module/Module.symvers
>     CC [M]  /path/to/my/externel/module/helloworld.mod.o
>     CC [M]  /path/to/my/externel/module/.module-common.o
>     LD [M]  /path/to/my/externel/module/helloworld.ko
>   make: Leaving directory '/path/to/my/linux'
> 
> [After]
> 
>   $ make -C /path/to/my/linux M=/path/to/my/externel/module
>   make: Entering directory '/path/to/my/linux'
>   make[1]: Entering directory '/path/to/my/externel/module'
>     CC [M]  helloworld.o
>     MODPOST Module.symvers
>     CC [M]  helloworld.mod.o
>     CC [M]  .module-common.o
>     LD [M]  helloworld.ko
>   make[1]: Leaving directory '/path/to/my/externel/module'
>   make: Leaving directory '/path/to/my/linux'
> 
> Printing "Entering directory" twice is cumbersome. This will be
> addressed later.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---

With this in v6.13-rc1 the cxl-test module fails depmod.
It causes depmod  to be invoked from the incorrect place
(or something doesn't respect INSTALL_MOD_PATH)

Is there something additional that this cxl-test module needs
to do?

Repro:
/git/new$ make V=1 M=tools/testing/cxl INSTALL_MOD_PATH=qbuild/mkosi.extra/ modules_install

Outputs:
make  -C /home/cxluser/git/new/tools/testing/cxl \
-f /home/cxluser/git/new/Makefile modules_install
make[1]: Entering directory '/home/cxluser/git/new/tools/testing/cxl'
make --no-print-directory -C /home/cxluser/git/new/tools/testing/cxl \
-f /home/cxluser/git/new/Makefile modules_install
make -f /home/cxluser/git/new/scripts/Makefile.modinst \
sign-only=
# INSTALL qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_acpi.ko
  cp cxl_acpi.ko qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_acpi.ko
# cmd_strip qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_acpi.ko
  :
# cmd_sign qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_acpi.ko
  :
# INSTALL qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_pmem.ko
  cp cxl_pmem.ko qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_pmem.ko
# cmd_strip qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_pmem.ko
  :
# cmd_sign qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_pmem.ko
  :
# INSTALL qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_port.ko
  cp cxl_port.ko qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_port.ko
# cmd_strip qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_port.ko
  :
# cmd_sign qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_port.ko
  :
# INSTALL qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_mem.ko
  cp cxl_mem.ko qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_mem.ko
# cmd_strip qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_mem.ko
  :
# cmd_sign qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_mem.ko
  :
# INSTALL qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_core.ko
  cp cxl_core.ko qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_core.ko
# cmd_strip qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_core.ko
  :
# cmd_sign qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_core.ko
  :
# INSTALL qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/test/cxl_test.ko
  cp test/cxl_test.ko qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/test/cxl_test.ko
# cmd_strip qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/test/cxl_test.ko
  :
# cmd_sign qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/test/cxl_test.ko
  :
# INSTALL qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/test/cxl_mock.ko
  cp test/cxl_mock.ko qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/test/cxl_mock.ko
# cmd_strip qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/test/cxl_mock.ko
  :
# cmd_sign qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/test/cxl_mock.ko
  :
# INSTALL qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/test/cxl_mock_mem.ko
  cp test/cxl_mock_mem.ko qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/test/cxl_mock_mem.ko
# cmd_strip qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/test/cxl_mock_mem.ko
  :
# cmd_sign qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/test/cxl_mock_mem.ko
  :
# DEPMOD  qbuild/mkosi.extra//lib/modules/6.13.0-rc1+
  /home/cxluser/git/new/scripts/depmod.sh 6.13.0-rc1+
depmod: WARNING: could not open modules.order at /home/cxluser/git/new/tools/testing/cxl/qbuild/mkosi.extra//lib/modules/6.13.0-rc1+: No such file or directory
depmod: WARNING: /home/cxluser/git/new/tools/testing/cxl/qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/test/cxl_mock.ko needs unknown symbol nvdimm_bus_register
depmod: WARNING: /home/cxluser/git/new/tools/testing/cxl/qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_pmem.ko needs unknown symbol to_nvdimm
depmod: WARNING: /home/cxluser/git/new/tools/testing/cxl/qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_pmem.ko needs unknown symbol __nvdimm_create
depmod: WARNING: /home/cxluser/git/new/tools/testing/cxl/qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_pmem.ko needs unknown symbol nvdimm_bus_unregister
depmod: WARNING: /home/cxluser/git/new/tools/testing/cxl/qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_pmem.ko needs unknown symbol nvdimm_region_delete
depmod: WARNING: /home/cxluser/git/new/tools/testing/cxl/qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_pmem.ko needs unknown symbol nvdimm_delete
depmod: WARNING: /home/cxluser/git/new/tools/testing/cxl/qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_pmem.ko needs unknown symbol nvdimm_provider_data
depmod: WARNING: /home/cxluser/git/new/tools/testing/cxl/qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_pmem.ko needs unknown symbol nvdimm_pmem_region_create
depmod: WARNING: /home/cxluser/git/new/tools/testing/cxl/qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_pmem.ko needs unknown symbol nd_fletcher64
depmod: WARNING: /home/cxluser/git/new/tools/testing/cxl/qbuild/mkosi.extra//lib/modules/6.13.0-rc1+/updates/cxl_pmem.ko needs unknown symbol nvdimm_cmd_mask
depmod: WARNING: could not open modules.builtin at /home/cxluser/git/new/tools/testing/cxl/qbuild/mkosi.extra//lib/modules/6.13.0-rc1+: No such file or directory
make[1]: Leaving directory '/home/cxluser/git/new/tools/testing/cxl'
cxluser@MySS:~/git/new$




> 
> Changes in v2:
>  - Introduce a new 'srcroot' variable and clean-up code
>  - Reword Documentation/dev-tools/coccinelle.rst
> 
>  Documentation/dev-tools/coccinelle.rst | 20 ++-----
>  Documentation/kbuild/makefiles.rst     | 14 +++++
>  Makefile                               | 80 +++++++++++++++-----------
>  rust/Makefile                          |  4 +-
>  scripts/Makefile.build                 |  2 +-
>  scripts/Makefile.clean                 |  2 +-
>  scripts/Makefile.compiler              |  2 +-
>  scripts/Makefile.modpost               |  6 +-
>  scripts/coccicheck                     |  6 +-
>  scripts/nsdeps                         |  8 +--
>  scripts/package/install-extmod-build   |  7 +++
>  11 files changed, 85 insertions(+), 66 deletions(-)
> 
> diff --git a/Documentation/dev-tools/coccinelle.rst b/Documentation/dev-tools/coccinelle.rst
> index 535ce126fb4f..6e70a1e9a3c0 100644
> --- a/Documentation/dev-tools/coccinelle.rst
> +++ b/Documentation/dev-tools/coccinelle.rst
> @@ -250,25 +250,17 @@ variables for .cocciconfig is as follows:
>  - Your directory from which spatch is called is processed next
>  - The directory provided with the ``--dir`` option is processed last, if used
>  
> -Since coccicheck runs through make, it naturally runs from the kernel
> -proper dir; as such the second rule above would be implied for picking up a
> -.cocciconfig when using ``make coccicheck``.
> -
>  ``make coccicheck`` also supports using M= targets. If you do not supply
>  any M= target, it is assumed you want to target the entire kernel.
>  The kernel coccicheck script has::
>  
> -    if [ "$KBUILD_EXTMOD" = "" ] ; then
> -        OPTIONS="--dir $srctree $COCCIINCLUDE"
> -    else
> -        OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
> -    fi
> +    OPTIONS="--dir $srcroot $COCCIINCLUDE"
>  
> -KBUILD_EXTMOD is set when an explicit target with M= is used. For both cases
> -the spatch ``--dir`` argument is used, as such third rule applies when whether
> -M= is used or not, and when M= is used the target directory can have its own
> -.cocciconfig file. When M= is not passed as an argument to coccicheck the
> -target directory is the same as the directory from where spatch was called.
> +Here, $srcroot refers to the source directory of the target: it points to the
> +external module's source directory when M= used, and otherwise, to the kernel
> +source directory. The third rule ensures the spatch reads the .cocciconfig from
> +the target directory, allowing external modules to have their own .cocciconfig
> +file.
>  
>  If not using the kernel's coccicheck target, keep the above precedence
>  order logic of .cocciconfig reading. If using the kernel's coccicheck target,
> diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
> index 7964e0c245ae..d36519f194dc 100644
> --- a/Documentation/kbuild/makefiles.rst
> +++ b/Documentation/kbuild/makefiles.rst
> @@ -449,6 +449,20 @@ $(obj)
>    to prerequisites are referenced with $(src) (because they are not
>    generated files).
>  
> +$(srcroot)
> +  $(srcroot) refers to the root of the source you are building, which can be
> +  either the kernel source or the external modules source, depending on whether
> +  KBUILD_EXTMOD is set. This can be either a relative or an absolute path, but
> +  if KBUILD_ABS_SRCTREE=1 is set, it is always an absolute path.
> +
> +$(srctree)
> +  $(srctree) refers to the root of the kernel source tree. When building the
> +  kernel, this is the same as $(srcroot).
> +
> +$(objtree)
> +  $(objtree) refers to the root of the kernel object tree. It is ``.`` when
> +  building the kernel, but it is different when building external modules.
> +
>  $(kecho)
>    echoing information to user in a rule is often a good practice
>    but when execution ``make -s`` one does not expect to see any output
> diff --git a/Makefile b/Makefile
> index cf1d55560ae2..e5f7ac7647a7 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -180,7 +180,24 @@ ifeq ("$(origin O)", "command line")
>    KBUILD_OUTPUT := $(O)
>  endif
>  
> -output := $(KBUILD_OUTPUT)
> +ifdef KBUILD_EXTMOD
> +    ifdef KBUILD_OUTPUT
> +        objtree := $(realpath $(KBUILD_OUTPUT))
> +        $(if $(objtree),,$(error specified kernel directory "$(KBUILD_OUTPUT)" does not exist))
> +    else
> +        objtree := $(CURDIR)
> +    endif
> +    output := $(KBUILD_EXTMOD)
> +    # KBUILD_EXTMOD might be a relative path. Remember its absolute path before
> +    # Make changes the working directory.
> +    srcroot := $(realpath $(KBUILD_EXTMOD))
> +    $(if $(srcroot),,$(error specified external module directory "$(KBUILD_EXTMOD)" does not exist))
> +else
> +    objtree := .
> +    output := $(KBUILD_OUTPUT)
> +endif
> +
> +export objtree srcroot
>  
>  # Do we want to change the working directory?
>  ifneq ($(output),)
> @@ -230,35 +247,33 @@ else # need-sub-make
>  
>  # We process the rest of the Makefile if this is the final invocation of make
>  
> -ifeq ($(abs_srctree),$(CURDIR))
> -        # building in the source tree
> -        srctree := .
> -	building_out_of_srctree :=
> +ifndef KBUILD_EXTMOD
> +srcroot := $(abs_srctree)
> +endif
> +
> +ifeq ($(srcroot),$(CURDIR))
> +building_out_of_srctree :=
>  else
> -        ifeq ($(abs_srctree)/,$(dir $(CURDIR)))
> -                # building in a subdirectory of the source tree
> -                srctree := ..
> -        else
> -                srctree := $(abs_srctree)
> -        endif
> -	building_out_of_srctree := 1
> +export building_out_of_srctree :=1
>  endif
>  
> -ifneq ($(KBUILD_ABS_SRCTREE),)
> -srctree := $(abs_srctree)
> +ifdef KBUILD_ABS_SRCTREE
> +    # Do not nothing. Use the absolute path.
> +else ifeq ($(srcroot),$(CURDIR))
> +    # Building in the source.
> +    srcroot := .
> +else ifeq ($(srcroot)/,$(dir $(CURDIR)))
> +    # Building in a subdirectory of the source.
> +    srcroot := ..
>  endif
>  
> -objtree		:= .
> +export srctree := $(if $(KBUILD_EXTMOD),$(abs_srctree),$(srcroot))
>  
> -VPATH		:=
> -
> -ifeq ($(KBUILD_EXTMOD),)
>  ifdef building_out_of_srctree
> -VPATH		:= $(srctree)
> +export VPATH := $(srcroot)
> +else
> +VPATH :=
>  endif
> -endif
> -
> -export building_out_of_srctree srctree objtree VPATH
>  
>  # To make sure we do not include .config for any of the *config targets
>  # catch them early, and hand them over to scripts/kconfig/Makefile
> @@ -711,7 +726,7 @@ endif
>  # in addition to whatever we do anyway.
>  # Just "make" or "make all" shall build modules as well
>  
> -ifneq ($(filter all modules nsdeps %compile_commands.json clang-%,$(MAKECMDGOALS)),)
> +ifneq ($(filter all modules nsdeps compile_commands.json clang-%,$(MAKECMDGOALS)),)
>    KBUILD_MODULES := 1
>  endif
>  
> @@ -1107,7 +1122,7 @@ export MODLIB
>  
>  PHONY += prepare0
>  
> -export extmod_prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)
> +export extmod_prefix =
>  export MODORDER := $(extmod_prefix)modules.order
>  export MODULES_NSDEPS := $(extmod_prefix)modules.nsdeps
>  
> @@ -1799,14 +1814,10 @@ filechk_kernel.release = echo $(KERNELRELEASE)
>  KBUILD_BUILTIN :=
>  KBUILD_MODULES := 1
>  
> -build-dir := $(KBUILD_EXTMOD)
> +build-dir := .
>  
> -compile_commands.json: $(extmod_prefix)compile_commands.json
> -PHONY += compile_commands.json
> -
> -clean-dirs := $(KBUILD_EXTMOD)
> -clean: private rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps \
> -	$(KBUILD_EXTMOD)/compile_commands.json
> +clean-dirs := .
> +clean: private rm-files := Module.symvers modules.nsdeps compile_commands.json
>  
>  PHONY += prepare
>  # now expand this into a simple variable to reduce the cost of shell evaluations
> @@ -1948,7 +1959,7 @@ $(clean-dirs):
>  
>  clean: $(clean-dirs)
>  	$(call cmd,rmfiles)
> -	@find $(or $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
> +	@find . $(RCS_FIND_IGNORE) \
>  		\( -name '*.[aios]' -o -name '*.rsi' -o -name '*.ko' -o -name '.*.cmd' \
>  		-o -name '*.ko.*' \
>  		-o -name '*.dtb' -o -name '*.dtbo' \
> @@ -1981,7 +1992,12 @@ tags TAGS cscope gtags: FORCE
>  PHONY += rust-analyzer
>  rust-analyzer:
>  	+$(Q)$(CONFIG_SHELL) $(srctree)/scripts/rust_is_available.sh
> +ifdef KBUILD_EXTMOD
> +# FIXME: external modules must not descend into a sub-directory of the kernel
> +	$(Q)$(MAKE) $(build)=$(objtree)/rust src=$(srctree)/rust $@
> +else
>  	$(Q)$(MAKE) $(build)=rust $@
> +endif
>  
>  # Script to generate missing namespace dependencies
>  # ---------------------------------------------------------------------------
> diff --git a/rust/Makefile b/rust/Makefile
> index b5e0a73b78f3..742740816c4b 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -362,8 +362,8 @@ rust-analyzer:
>  	$(Q)$(srctree)/scripts/generate_rust_analyzer.py \
>  		--cfgs='core=$(core-cfgs)' --cfgs='alloc=$(alloc-cfgs)' \
>  		$(realpath $(srctree)) $(realpath $(objtree)) \
> -		$(rustc_sysroot) $(RUST_LIB_SRC) $(KBUILD_EXTMOD) > \
> -		$(if $(KBUILD_EXTMOD),$(extmod_prefix),$(objtree))/rust-project.json
> +		$(rustc_sysroot) $(RUST_LIB_SRC) $(if $(KBUILD_EXTMOD),$(srcroot)) \
> +		> rust-project.json
>  
>  redirect-intrinsics = \
>  	__addsf3 __eqsf2 __extendsfdf2 __gesf2 __lesf2 __ltsf2 __mulsf3 __nesf2 __truncdfsf2 __unordsf2 \
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 64cd046f8fd8..1aa928a6fb4f 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -3,7 +3,7 @@
>  # Building
>  # ==========================================================================
>  
> -src := $(if $(VPATH),$(VPATH)/)$(obj)
> +src := $(srcroot)/$(obj)
>  
>  PHONY := $(obj)/
>  $(obj)/:
> diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean
> index 4fcfab40ed61..6ead00ec7313 100644
> --- a/scripts/Makefile.clean
> +++ b/scripts/Makefile.clean
> @@ -3,7 +3,7 @@
>  # Cleaning up
>  # ==========================================================================
>  
> -src := $(if $(VPATH),$(VPATH)/)$(obj)
> +src := $(srcroot)/$(obj)
>  
>  PHONY := __clean
>  __clean:
> diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
> index e0842496d26e..8c1029687e2e 100644
> --- a/scripts/Makefile.compiler
> +++ b/scripts/Makefile.compiler
> @@ -13,7 +13,7 @@ cc-cross-prefix = $(firstword $(foreach c, $(1), \
>  			$(if $(shell command -v -- $(c)gcc 2>/dev/null), $(c))))
>  
>  # output directory for tests below
> -TMPOUT = $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/).tmp_$$$$
> +TMPOUT = .tmp_$$$$
>  
>  # try-run
>  # Usage: option = $(call try-run, $(CC)...-o "$$TMP",option-ok,otherwise)
> diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
> index 12e7c15d099c..78d2ca4f25f5 100644
> --- a/scripts/Makefile.modpost
> +++ b/scripts/Makefile.modpost
> @@ -111,13 +111,13 @@ endif
>  else
>  
>  # set src + obj - they may be used in the modules's Makefile
> -obj := $(KBUILD_EXTMOD)
> -src := $(if $(VPATH),$(VPATH)/)$(obj)
> +obj := .
> +src := $(srcroot)
>  
>  # Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS
>  include $(kbuild-file)
>  
> -output-symdump := $(KBUILD_EXTMOD)/Module.symvers
> +output-symdump := Module.symvers
>  
>  ifeq ($(wildcard $(objtree)/Module.symvers),)
>  missing-input := $(objtree)/Module.symvers
> diff --git a/scripts/coccicheck b/scripts/coccicheck
> index e52cb43fede6..0e6bc5a10320 100755
> --- a/scripts/coccicheck
> +++ b/scripts/coccicheck
> @@ -80,11 +80,7 @@ command results in a shift count error.'
>      NPROC=1
>  else
>      ONLINE=0
> -    if [ "$KBUILD_EXTMOD" = "" ] ; then
> -        OPTIONS="--dir $srctree $COCCIINCLUDE"
> -    else
> -        OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
> -    fi
> +    OPTIONS="--dir $srcroot $COCCIINCLUDE"
>  
>      # Use only one thread per core by default if hyperthreading is enabled
>      THREADS_PER_CORE=$(LANG=C lscpu | grep "Thread(s) per core: " | tr -cd "[:digit:]")
> diff --git a/scripts/nsdeps b/scripts/nsdeps
> index f1718cc0d700..8ca12e2b5c03 100644
> --- a/scripts/nsdeps
> +++ b/scripts/nsdeps
> @@ -19,12 +19,6 @@ if ! { echo "$SPATCH_REQ_VERSION"; echo "$SPATCH_VERSION"; } | sort -CV ; then
>  	exit 1
>  fi
>  
> -if [ "$KBUILD_EXTMOD" ]; then
> -	src_prefix=
> -else
> -	src_prefix=$srctree/
> -fi
> -
>  generate_deps_for_ns() {
>  	$SPATCH --very-quiet --in-place --sp-file \
>  		$srctree/scripts/coccinelle/misc/add_namespace.cocci -D nsdeps -D ns=$1 $2
> @@ -34,7 +28,7 @@ generate_deps() {
>  	local mod=${1%.ko:}
>  	shift
>  	local namespaces="$*"
> -	local mod_source_files=$(sed "s|^\(.*\)\.o$|${src_prefix}\1.c|" $mod.mod)
> +	local mod_source_files=$(sed "s|^\(.*\)\.o$|${srcroot}/\1.c|" $mod.mod)
>  
>  	for ns in $namespaces; do
>  		echo "Adding namespace $ns to module $mod.ko."
> diff --git a/scripts/package/install-extmod-build b/scripts/package/install-extmod-build
> index 7ec1f061a519..64d958ee45f3 100755
> --- a/scripts/package/install-extmod-build
> +++ b/scripts/package/install-extmod-build
> @@ -51,6 +51,13 @@ mkdir -p "${destdir}"
>  if [ "${CC}" != "${HOSTCC}" ]; then
>  	echo "Rebuilding host programs with ${CC}..."
>  
> +	# This leverages external module building.
> +	# - Clear sub_make_done to allow the top-level Makefile to redo sub-make.
> +	# - Filter out --no-print-directory to print "Entering directory" logs
> +	#   when Make changes the working directory.
> +	unset sub_make_done
> +	MAKEFLAGS=$(echo "${MAKEFLAGS}" | sed s/--no-print-directory//)
> +
>  	cat <<-'EOF' >  "${destdir}/Kbuild"
>  	subdir-y := scripts
>  	EOF
> -- 
> 2.43.0
> 

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-12-04 20:51   ` Alison Schofield
@ 2024-12-05  2:33     ` Masahiro Yamada
  0 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-12-05  2:33 UTC (permalink / raw)
  To: Alison Schofield
  Cc: Vishal Verma, Ira Weiny, linux-kbuild, linux-kernel,
	rust-for-linux, cocci

On Thu, Dec 5, 2024 at 5:51 AM Alison Schofield
<alison.schofield@intel.com> wrote:
>
> On Sun, Nov 10, 2024 at 10:34:33AM +0900, Masahiro Yamada wrote:
> > Currently, Kbuild always operates in the output directory of the kernel,
> > even when building external modules. This increases the risk of external
> > module Makefiles attempting to write to the kernel directory.
> >
> > This commit switches the working directory to the external module
> > directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> > some build artifacts.
> >
> > The command for building external modules maintains backward
> > compatibility, but Makefiles that rely on working in the kernel
> > directory may break. In such cases, $(objtree) and $(srctree) should
> > be used to refer to the output and source directories of the kernel.
> >
> > The appearance of the build log will change as follows:
> >
> > [Before]
> >
> >   $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >   make: Entering directory '/path/to/my/linux'
> >     CC [M]  /path/to/my/externel/module/helloworld.o
> >     MODPOST /path/to/my/externel/module/Module.symvers
> >     CC [M]  /path/to/my/externel/module/helloworld.mod.o
> >     CC [M]  /path/to/my/externel/module/.module-common.o
> >     LD [M]  /path/to/my/externel/module/helloworld.ko
> >   make: Leaving directory '/path/to/my/linux'
> >
> > [After]
> >
> >   $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >   make: Entering directory '/path/to/my/linux'
> >   make[1]: Entering directory '/path/to/my/externel/module'
> >     CC [M]  helloworld.o
> >     MODPOST Module.symvers
> >     CC [M]  helloworld.mod.o
> >     CC [M]  .module-common.o
> >     LD [M]  helloworld.ko
> >   make[1]: Leaving directory '/path/to/my/externel/module'
> >   make: Leaving directory '/path/to/my/linux'
> >
> > Printing "Entering directory" twice is cumbersome. This will be
> > addressed later.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > ---
>
> With this in v6.13-rc1 the cxl-test module fails depmod.
> It causes depmod  to be invoked from the incorrect place
> (or something doesn't respect INSTALL_MOD_PATH)
>
> Is there something additional that this cxl-test module needs
> to do?
>
> Repro:
> /git/new$ make V=1 M=tools/testing/cxl INSTALL_MOD_PATH=qbuild/mkosi.extra/ modules_install

Kbuild changes the working directory, so you need to specify
an absolute path for INSTALL_MOD_PATH.

INSTALL_MOD_PATH=$(realpath qbuild/mkosi.extra/)




-- 
Best Regards
Masahiro Yamada

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-11-10  1:34 ` [PATCH v2 05/11] kbuild: change working directory to external module directory with M= Masahiro Yamada
  2024-11-18 14:47   ` Nicolas Schier
  2024-12-04 20:51   ` Alison Schofield
@ 2024-12-04 23:35   ` Charlie Jenkins
  2024-12-05  2:48     ` Masahiro Yamada
  2024-12-09 13:46   ` Thorsten Blum
                     ` (2 subsequent siblings)
  5 siblings, 1 reply; 33+ messages in thread
From: Charlie Jenkins @ 2024-12-04 23:35 UTC (permalink / raw)
  To: Masahiro Yamada; +Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci

On Sun, Nov 10, 2024 at 10:34:33AM +0900, Masahiro Yamada wrote:
> Currently, Kbuild always operates in the output directory of the kernel,
> even when building external modules. This increases the risk of external
> module Makefiles attempting to write to the kernel directory.
> 
> This commit switches the working directory to the external module
> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> some build artifacts.
> 
> The command for building external modules maintains backward
> compatibility, but Makefiles that rely on working in the kernel
> directory may break. In such cases, $(objtree) and $(srctree) should
> be used to refer to the output and source directories of the kernel.
> 
> The appearance of the build log will change as follows:
> 
> [Before]
> 
>   $ make -C /path/to/my/linux M=/path/to/my/externel/module
>   make: Entering directory '/path/to/my/linux'
>     CC [M]  /path/to/my/externel/module/helloworld.o
>     MODPOST /path/to/my/externel/module/Module.symvers
>     CC [M]  /path/to/my/externel/module/helloworld.mod.o
>     CC [M]  /path/to/my/externel/module/.module-common.o
>     LD [M]  /path/to/my/externel/module/helloworld.ko
>   make: Leaving directory '/path/to/my/linux'
> 
> [After]
> 
>   $ make -C /path/to/my/linux M=/path/to/my/externel/module
>   make: Entering directory '/path/to/my/linux'
>   make[1]: Entering directory '/path/to/my/externel/module'
>     CC [M]  helloworld.o
>     MODPOST Module.symvers
>     CC [M]  helloworld.mod.o
>     CC [M]  .module-common.o
>     LD [M]  helloworld.ko
>   make[1]: Leaving directory '/path/to/my/externel/module'
>   make: Leaving directory '/path/to/my/linux'
> 
> Printing "Entering directory" twice is cumbersome. This will be
> addressed later.

This change has caused O=<relative directory> to fail.

For example:

make O=build defconfig
make -j$(nproc) V=1 O=build bindeb-pkg

outputs:

make ARCH=x86 KERNELRELEASE=6.13.0-rc1 KBUILD_BUILD_VERSION=3  run-command KBUILD_RUN_COMMAND='+$(srctree)/scripts/package/builddeb linux-libc-dev'
dh_installchangelogs -plinux-image-6.13.0-rc1
../scripts/package/builddeb linux-headers-6.13.0-rc1
dh_compress -plinux-image-6.13.0-rc1
dh_fixperms -plinux-image-6.13.0-rc1
dh_gencontrol -plinux-image-6.13.0-rc1 -- -fdebian/image.files
Rebuilding host programs with x86_64-linux-gnu-gcc...
make[6]: Entering directory '/scratch/kernels/linux/build'
/scratch/kernels/linux/Makefile:190: *** specified kernel directory "build" does not exist.  Stop.

It is stepping into this directory and then trying to find the directory
it just stepped into so $(realpath $(KBUILD_OUTPUT)) returns an empty
string.

Using an absolute directory resolves this problem, but I believe it
shouldn't be necessary.

- Charlie

> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
> 
> Changes in v2:
>  - Introduce a new 'srcroot' variable and clean-up code
>  - Reword Documentation/dev-tools/coccinelle.rst
> 
>  Documentation/dev-tools/coccinelle.rst | 20 ++-----
>  Documentation/kbuild/makefiles.rst     | 14 +++++
>  Makefile                               | 80 +++++++++++++++-----------
>  rust/Makefile                          |  4 +-
>  scripts/Makefile.build                 |  2 +-
>  scripts/Makefile.clean                 |  2 +-
>  scripts/Makefile.compiler              |  2 +-
>  scripts/Makefile.modpost               |  6 +-
>  scripts/coccicheck                     |  6 +-
>  scripts/nsdeps                         |  8 +--
>  scripts/package/install-extmod-build   |  7 +++
>  11 files changed, 85 insertions(+), 66 deletions(-)
> 
> diff --git a/Documentation/dev-tools/coccinelle.rst b/Documentation/dev-tools/coccinelle.rst
> index 535ce126fb4f..6e70a1e9a3c0 100644
> --- a/Documentation/dev-tools/coccinelle.rst
> +++ b/Documentation/dev-tools/coccinelle.rst
> @@ -250,25 +250,17 @@ variables for .cocciconfig is as follows:
>  - Your directory from which spatch is called is processed next
>  - The directory provided with the ``--dir`` option is processed last, if used
>  
> -Since coccicheck runs through make, it naturally runs from the kernel
> -proper dir; as such the second rule above would be implied for picking up a
> -.cocciconfig when using ``make coccicheck``.
> -
>  ``make coccicheck`` also supports using M= targets. If you do not supply
>  any M= target, it is assumed you want to target the entire kernel.
>  The kernel coccicheck script has::
>  
> -    if [ "$KBUILD_EXTMOD" = "" ] ; then
> -        OPTIONS="--dir $srctree $COCCIINCLUDE"
> -    else
> -        OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
> -    fi
> +    OPTIONS="--dir $srcroot $COCCIINCLUDE"
>  
> -KBUILD_EXTMOD is set when an explicit target with M= is used. For both cases
> -the spatch ``--dir`` argument is used, as such third rule applies when whether
> -M= is used or not, and when M= is used the target directory can have its own
> -.cocciconfig file. When M= is not passed as an argument to coccicheck the
> -target directory is the same as the directory from where spatch was called.
> +Here, $srcroot refers to the source directory of the target: it points to the
> +external module's source directory when M= used, and otherwise, to the kernel
> +source directory. The third rule ensures the spatch reads the .cocciconfig from
> +the target directory, allowing external modules to have their own .cocciconfig
> +file.
>  
>  If not using the kernel's coccicheck target, keep the above precedence
>  order logic of .cocciconfig reading. If using the kernel's coccicheck target,
> diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
> index 7964e0c245ae..d36519f194dc 100644
> --- a/Documentation/kbuild/makefiles.rst
> +++ b/Documentation/kbuild/makefiles.rst
> @@ -449,6 +449,20 @@ $(obj)
>    to prerequisites are referenced with $(src) (because they are not
>    generated files).
>  
> +$(srcroot)
> +  $(srcroot) refers to the root of the source you are building, which can be
> +  either the kernel source or the external modules source, depending on whether
> +  KBUILD_EXTMOD is set. This can be either a relative or an absolute path, but
> +  if KBUILD_ABS_SRCTREE=1 is set, it is always an absolute path.
> +
> +$(srctree)
> +  $(srctree) refers to the root of the kernel source tree. When building the
> +  kernel, this is the same as $(srcroot).
> +
> +$(objtree)
> +  $(objtree) refers to the root of the kernel object tree. It is ``.`` when
> +  building the kernel, but it is different when building external modules.
> +
>  $(kecho)
>    echoing information to user in a rule is often a good practice
>    but when execution ``make -s`` one does not expect to see any output
> diff --git a/Makefile b/Makefile
> index cf1d55560ae2..e5f7ac7647a7 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -180,7 +180,24 @@ ifeq ("$(origin O)", "command line")
>    KBUILD_OUTPUT := $(O)
>  endif
>  
> -output := $(KBUILD_OUTPUT)
> +ifdef KBUILD_EXTMOD
> +    ifdef KBUILD_OUTPUT
> +        objtree := $(realpath $(KBUILD_OUTPUT))
> +        $(if $(objtree),,$(error specified kernel directory "$(KBUILD_OUTPUT)" does not exist))
> +    else
> +        objtree := $(CURDIR)
> +    endif
> +    output := $(KBUILD_EXTMOD)
> +    # KBUILD_EXTMOD might be a relative path. Remember its absolute path before
> +    # Make changes the working directory.
> +    srcroot := $(realpath $(KBUILD_EXTMOD))
> +    $(if $(srcroot),,$(error specified external module directory "$(KBUILD_EXTMOD)" does not exist))
> +else
> +    objtree := .
> +    output := $(KBUILD_OUTPUT)
> +endif
> +
> +export objtree srcroot
>  
>  # Do we want to change the working directory?
>  ifneq ($(output),)
> @@ -230,35 +247,33 @@ else # need-sub-make
>  
>  # We process the rest of the Makefile if this is the final invocation of make
>  
> -ifeq ($(abs_srctree),$(CURDIR))
> -        # building in the source tree
> -        srctree := .
> -	building_out_of_srctree :=
> +ifndef KBUILD_EXTMOD
> +srcroot := $(abs_srctree)
> +endif
> +
> +ifeq ($(srcroot),$(CURDIR))
> +building_out_of_srctree :=
>  else
> -        ifeq ($(abs_srctree)/,$(dir $(CURDIR)))
> -                # building in a subdirectory of the source tree
> -                srctree := ..
> -        else
> -                srctree := $(abs_srctree)
> -        endif
> -	building_out_of_srctree := 1
> +export building_out_of_srctree :=1
>  endif
>  
> -ifneq ($(KBUILD_ABS_SRCTREE),)
> -srctree := $(abs_srctree)
> +ifdef KBUILD_ABS_SRCTREE
> +    # Do not nothing. Use the absolute path.
> +else ifeq ($(srcroot),$(CURDIR))
> +    # Building in the source.
> +    srcroot := .
> +else ifeq ($(srcroot)/,$(dir $(CURDIR)))
> +    # Building in a subdirectory of the source.
> +    srcroot := ..
>  endif
>  
> -objtree		:= .
> +export srctree := $(if $(KBUILD_EXTMOD),$(abs_srctree),$(srcroot))
>  
> -VPATH		:=
> -
> -ifeq ($(KBUILD_EXTMOD),)
>  ifdef building_out_of_srctree
> -VPATH		:= $(srctree)
> +export VPATH := $(srcroot)
> +else
> +VPATH :=
>  endif
> -endif
> -
> -export building_out_of_srctree srctree objtree VPATH
>  
>  # To make sure we do not include .config for any of the *config targets
>  # catch them early, and hand them over to scripts/kconfig/Makefile
> @@ -711,7 +726,7 @@ endif
>  # in addition to whatever we do anyway.
>  # Just "make" or "make all" shall build modules as well
>  
> -ifneq ($(filter all modules nsdeps %compile_commands.json clang-%,$(MAKECMDGOALS)),)
> +ifneq ($(filter all modules nsdeps compile_commands.json clang-%,$(MAKECMDGOALS)),)
>    KBUILD_MODULES := 1
>  endif
>  
> @@ -1107,7 +1122,7 @@ export MODLIB
>  
>  PHONY += prepare0
>  
> -export extmod_prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)
> +export extmod_prefix =
>  export MODORDER := $(extmod_prefix)modules.order
>  export MODULES_NSDEPS := $(extmod_prefix)modules.nsdeps
>  
> @@ -1799,14 +1814,10 @@ filechk_kernel.release = echo $(KERNELRELEASE)
>  KBUILD_BUILTIN :=
>  KBUILD_MODULES := 1
>  
> -build-dir := $(KBUILD_EXTMOD)
> +build-dir := .
>  
> -compile_commands.json: $(extmod_prefix)compile_commands.json
> -PHONY += compile_commands.json
> -
> -clean-dirs := $(KBUILD_EXTMOD)
> -clean: private rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps \
> -	$(KBUILD_EXTMOD)/compile_commands.json
> +clean-dirs := .
> +clean: private rm-files := Module.symvers modules.nsdeps compile_commands.json
>  
>  PHONY += prepare
>  # now expand this into a simple variable to reduce the cost of shell evaluations
> @@ -1948,7 +1959,7 @@ $(clean-dirs):
>  
>  clean: $(clean-dirs)
>  	$(call cmd,rmfiles)
> -	@find $(or $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
> +	@find . $(RCS_FIND_IGNORE) \
>  		\( -name '*.[aios]' -o -name '*.rsi' -o -name '*.ko' -o -name '.*.cmd' \
>  		-o -name '*.ko.*' \
>  		-o -name '*.dtb' -o -name '*.dtbo' \
> @@ -1981,7 +1992,12 @@ tags TAGS cscope gtags: FORCE
>  PHONY += rust-analyzer
>  rust-analyzer:
>  	+$(Q)$(CONFIG_SHELL) $(srctree)/scripts/rust_is_available.sh
> +ifdef KBUILD_EXTMOD
> +# FIXME: external modules must not descend into a sub-directory of the kernel
> +	$(Q)$(MAKE) $(build)=$(objtree)/rust src=$(srctree)/rust $@
> +else
>  	$(Q)$(MAKE) $(build)=rust $@
> +endif
>  
>  # Script to generate missing namespace dependencies
>  # ---------------------------------------------------------------------------
> diff --git a/rust/Makefile b/rust/Makefile
> index b5e0a73b78f3..742740816c4b 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -362,8 +362,8 @@ rust-analyzer:
>  	$(Q)$(srctree)/scripts/generate_rust_analyzer.py \
>  		--cfgs='core=$(core-cfgs)' --cfgs='alloc=$(alloc-cfgs)' \
>  		$(realpath $(srctree)) $(realpath $(objtree)) \
> -		$(rustc_sysroot) $(RUST_LIB_SRC) $(KBUILD_EXTMOD) > \
> -		$(if $(KBUILD_EXTMOD),$(extmod_prefix),$(objtree))/rust-project.json
> +		$(rustc_sysroot) $(RUST_LIB_SRC) $(if $(KBUILD_EXTMOD),$(srcroot)) \
> +		> rust-project.json
>  
>  redirect-intrinsics = \
>  	__addsf3 __eqsf2 __extendsfdf2 __gesf2 __lesf2 __ltsf2 __mulsf3 __nesf2 __truncdfsf2 __unordsf2 \
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 64cd046f8fd8..1aa928a6fb4f 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -3,7 +3,7 @@
>  # Building
>  # ==========================================================================
>  
> -src := $(if $(VPATH),$(VPATH)/)$(obj)
> +src := $(srcroot)/$(obj)
>  
>  PHONY := $(obj)/
>  $(obj)/:
> diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean
> index 4fcfab40ed61..6ead00ec7313 100644
> --- a/scripts/Makefile.clean
> +++ b/scripts/Makefile.clean
> @@ -3,7 +3,7 @@
>  # Cleaning up
>  # ==========================================================================
>  
> -src := $(if $(VPATH),$(VPATH)/)$(obj)
> +src := $(srcroot)/$(obj)
>  
>  PHONY := __clean
>  __clean:
> diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
> index e0842496d26e..8c1029687e2e 100644
> --- a/scripts/Makefile.compiler
> +++ b/scripts/Makefile.compiler
> @@ -13,7 +13,7 @@ cc-cross-prefix = $(firstword $(foreach c, $(1), \
>  			$(if $(shell command -v -- $(c)gcc 2>/dev/null), $(c))))
>  
>  # output directory for tests below
> -TMPOUT = $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/).tmp_$$$$
> +TMPOUT = .tmp_$$$$
>  
>  # try-run
>  # Usage: option = $(call try-run, $(CC)...-o "$$TMP",option-ok,otherwise)
> diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
> index 12e7c15d099c..78d2ca4f25f5 100644
> --- a/scripts/Makefile.modpost
> +++ b/scripts/Makefile.modpost
> @@ -111,13 +111,13 @@ endif
>  else
>  
>  # set src + obj - they may be used in the modules's Makefile
> -obj := $(KBUILD_EXTMOD)
> -src := $(if $(VPATH),$(VPATH)/)$(obj)
> +obj := .
> +src := $(srcroot)
>  
>  # Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS
>  include $(kbuild-file)
>  
> -output-symdump := $(KBUILD_EXTMOD)/Module.symvers
> +output-symdump := Module.symvers
>  
>  ifeq ($(wildcard $(objtree)/Module.symvers),)
>  missing-input := $(objtree)/Module.symvers
> diff --git a/scripts/coccicheck b/scripts/coccicheck
> index e52cb43fede6..0e6bc5a10320 100755
> --- a/scripts/coccicheck
> +++ b/scripts/coccicheck
> @@ -80,11 +80,7 @@ command results in a shift count error.'
>      NPROC=1
>  else
>      ONLINE=0
> -    if [ "$KBUILD_EXTMOD" = "" ] ; then
> -        OPTIONS="--dir $srctree $COCCIINCLUDE"
> -    else
> -        OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
> -    fi
> +    OPTIONS="--dir $srcroot $COCCIINCLUDE"
>  
>      # Use only one thread per core by default if hyperthreading is enabled
>      THREADS_PER_CORE=$(LANG=C lscpu | grep "Thread(s) per core: " | tr -cd "[:digit:]")
> diff --git a/scripts/nsdeps b/scripts/nsdeps
> index f1718cc0d700..8ca12e2b5c03 100644
> --- a/scripts/nsdeps
> +++ b/scripts/nsdeps
> @@ -19,12 +19,6 @@ if ! { echo "$SPATCH_REQ_VERSION"; echo "$SPATCH_VERSION"; } | sort -CV ; then
>  	exit 1
>  fi
>  
> -if [ "$KBUILD_EXTMOD" ]; then
> -	src_prefix=
> -else
> -	src_prefix=$srctree/
> -fi
> -
>  generate_deps_for_ns() {
>  	$SPATCH --very-quiet --in-place --sp-file \
>  		$srctree/scripts/coccinelle/misc/add_namespace.cocci -D nsdeps -D ns=$1 $2
> @@ -34,7 +28,7 @@ generate_deps() {
>  	local mod=${1%.ko:}
>  	shift
>  	local namespaces="$*"
> -	local mod_source_files=$(sed "s|^\(.*\)\.o$|${src_prefix}\1.c|" $mod.mod)
> +	local mod_source_files=$(sed "s|^\(.*\)\.o$|${srcroot}/\1.c|" $mod.mod)
>  
>  	for ns in $namespaces; do
>  		echo "Adding namespace $ns to module $mod.ko."
> diff --git a/scripts/package/install-extmod-build b/scripts/package/install-extmod-build
> index 7ec1f061a519..64d958ee45f3 100755
> --- a/scripts/package/install-extmod-build
> +++ b/scripts/package/install-extmod-build
> @@ -51,6 +51,13 @@ mkdir -p "${destdir}"
>  if [ "${CC}" != "${HOSTCC}" ]; then
>  	echo "Rebuilding host programs with ${CC}..."
>  
> +	# This leverages external module building.
> +	# - Clear sub_make_done to allow the top-level Makefile to redo sub-make.
> +	# - Filter out --no-print-directory to print "Entering directory" logs
> +	#   when Make changes the working directory.
> +	unset sub_make_done
> +	MAKEFLAGS=$(echo "${MAKEFLAGS}" | sed s/--no-print-directory//)
> +
>  	cat <<-'EOF' >  "${destdir}/Kbuild"
>  	subdir-y := scripts
>  	EOF
> -- 
> 2.43.0

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-12-04 23:35   ` Charlie Jenkins
@ 2024-12-05  2:48     ` Masahiro Yamada
  2024-12-05  6:27       ` Charlie Jenkins
  0 siblings, 1 reply; 33+ messages in thread
From: Masahiro Yamada @ 2024-12-05  2:48 UTC (permalink / raw)
  To: Charlie Jenkins; +Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci

On Thu, Dec 5, 2024 at 8:35 AM Charlie Jenkins <charlie@rivosinc.com> wrote:
>
> On Sun, Nov 10, 2024 at 10:34:33AM +0900, Masahiro Yamada wrote:
> > Currently, Kbuild always operates in the output directory of the kernel,
> > even when building external modules. This increases the risk of external
> > module Makefiles attempting to write to the kernel directory.
> >
> > This commit switches the working directory to the external module
> > directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> > some build artifacts.
> >
> > The command for building external modules maintains backward
> > compatibility, but Makefiles that rely on working in the kernel
> > directory may break. In such cases, $(objtree) and $(srctree) should
> > be used to refer to the output and source directories of the kernel.
> >
> > The appearance of the build log will change as follows:
> >
> > [Before]
> >
> >   $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >   make: Entering directory '/path/to/my/linux'
> >     CC [M]  /path/to/my/externel/module/helloworld.o
> >     MODPOST /path/to/my/externel/module/Module.symvers
> >     CC [M]  /path/to/my/externel/module/helloworld.mod.o
> >     CC [M]  /path/to/my/externel/module/.module-common.o
> >     LD [M]  /path/to/my/externel/module/helloworld.ko
> >   make: Leaving directory '/path/to/my/linux'
> >
> > [After]
> >
> >   $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >   make: Entering directory '/path/to/my/linux'
> >   make[1]: Entering directory '/path/to/my/externel/module'
> >     CC [M]  helloworld.o
> >     MODPOST Module.symvers
> >     CC [M]  helloworld.mod.o
> >     CC [M]  .module-common.o
> >     LD [M]  helloworld.ko
> >   make[1]: Leaving directory '/path/to/my/externel/module'
> >   make: Leaving directory '/path/to/my/linux'
> >
> > Printing "Entering directory" twice is cumbersome. This will be
> > addressed later.
>
> This change has caused O=<relative directory> to fail.
>
> For example:
>
> make O=build defconfig
> make -j$(nproc) V=1 O=build bindeb-pkg
>
> outputs:
>
> make ARCH=x86 KERNELRELEASE=6.13.0-rc1 KBUILD_BUILD_VERSION=3  run-command KBUILD_RUN_COMMAND='+$(srctree)/scripts/package/builddeb linux-libc-dev'
> dh_installchangelogs -plinux-image-6.13.0-rc1
> ../scripts/package/builddeb linux-headers-6.13.0-rc1
> dh_compress -plinux-image-6.13.0-rc1
> dh_fixperms -plinux-image-6.13.0-rc1
> dh_gencontrol -plinux-image-6.13.0-rc1 -- -fdebian/image.files
> Rebuilding host programs with x86_64-linux-gnu-gcc...
> make[6]: Entering directory '/scratch/kernels/linux/build'
> /scratch/kernels/linux/Makefile:190: *** specified kernel directory "build" does not exist.  Stop.
>
> It is stepping into this directory and then trying to find the directory
> it just stepped into so $(realpath $(KBUILD_OUTPUT)) returns an empty
> string.
>
> Using an absolute directory resolves this problem, but I believe it
> shouldn't be necessary.


Agree.

I will apply the following fixup unless I have a better idea.




diff --git a/scripts/package/install-extmod-build
b/scripts/package/install-extmod-build
index 64d958ee45f3..85af1573db31 100755
--- a/scripts/package/install-extmod-build
+++ b/scripts/package/install-extmod-build
@@ -69,7 +69,7 @@ if [ "${CC}" != "${HOSTCC}" ]; then
        #
        # Use the single-target build to avoid the modpost invocation, which
        # would overwrite Module.symvers.
-       "${MAKE}" HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/
+       "${MAKE}" O=. HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/

        cat <<-'EOF' >  "${destdir}/scripts/Kbuild"
        subdir-y := basic
@@ -78,7 +78,7 @@ if [ "${CC}" != "${HOSTCC}" ]; then
        EOF

        # Run once again to rebuild scripts/basic/ and scripts/mod/modpost.
-       "${MAKE}" HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/
+       "${MAKE}" O=. HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/

        rm -f "${destdir}/Kbuild" "${destdir}/scripts/Kbuild"
 fi



--
Best Regards
Masahiro Yamada

^ permalink raw reply related	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-12-05  2:48     ` Masahiro Yamada
@ 2024-12-05  6:27       ` Charlie Jenkins
  0 siblings, 0 replies; 33+ messages in thread
From: Charlie Jenkins @ 2024-12-05  6:27 UTC (permalink / raw)
  To: Masahiro Yamada; +Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci

On Thu, Dec 05, 2024 at 11:48:08AM +0900, Masahiro Yamada wrote:
> On Thu, Dec 5, 2024 at 8:35 AM Charlie Jenkins <charlie@rivosinc.com> wrote:
> >
> > On Sun, Nov 10, 2024 at 10:34:33AM +0900, Masahiro Yamada wrote:
> > > Currently, Kbuild always operates in the output directory of the kernel,
> > > even when building external modules. This increases the risk of external
> > > module Makefiles attempting to write to the kernel directory.
> > >
> > > This commit switches the working directory to the external module
> > > directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> > > some build artifacts.
> > >
> > > The command for building external modules maintains backward
> > > compatibility, but Makefiles that rely on working in the kernel
> > > directory may break. In such cases, $(objtree) and $(srctree) should
> > > be used to refer to the output and source directories of the kernel.
> > >
> > > The appearance of the build log will change as follows:
> > >
> > > [Before]
> > >
> > >   $ make -C /path/to/my/linux M=/path/to/my/externel/module
> > >   make: Entering directory '/path/to/my/linux'
> > >     CC [M]  /path/to/my/externel/module/helloworld.o
> > >     MODPOST /path/to/my/externel/module/Module.symvers
> > >     CC [M]  /path/to/my/externel/module/helloworld.mod.o
> > >     CC [M]  /path/to/my/externel/module/.module-common.o
> > >     LD [M]  /path/to/my/externel/module/helloworld.ko
> > >   make: Leaving directory '/path/to/my/linux'
> > >
> > > [After]
> > >
> > >   $ make -C /path/to/my/linux M=/path/to/my/externel/module
> > >   make: Entering directory '/path/to/my/linux'
> > >   make[1]: Entering directory '/path/to/my/externel/module'
> > >     CC [M]  helloworld.o
> > >     MODPOST Module.symvers
> > >     CC [M]  helloworld.mod.o
> > >     CC [M]  .module-common.o
> > >     LD [M]  helloworld.ko
> > >   make[1]: Leaving directory '/path/to/my/externel/module'
> > >   make: Leaving directory '/path/to/my/linux'
> > >
> > > Printing "Entering directory" twice is cumbersome. This will be
> > > addressed later.
> >
> > This change has caused O=<relative directory> to fail.
> >
> > For example:
> >
> > make O=build defconfig
> > make -j$(nproc) V=1 O=build bindeb-pkg
> >
> > outputs:
> >
> > make ARCH=x86 KERNELRELEASE=6.13.0-rc1 KBUILD_BUILD_VERSION=3  run-command KBUILD_RUN_COMMAND='+$(srctree)/scripts/package/builddeb linux-libc-dev'
> > dh_installchangelogs -plinux-image-6.13.0-rc1
> > ../scripts/package/builddeb linux-headers-6.13.0-rc1
> > dh_compress -plinux-image-6.13.0-rc1
> > dh_fixperms -plinux-image-6.13.0-rc1
> > dh_gencontrol -plinux-image-6.13.0-rc1 -- -fdebian/image.files
> > Rebuilding host programs with x86_64-linux-gnu-gcc...
> > make[6]: Entering directory '/scratch/kernels/linux/build'
> > /scratch/kernels/linux/Makefile:190: *** specified kernel directory "build" does not exist.  Stop.
> >
> > It is stepping into this directory and then trying to find the directory
> > it just stepped into so $(realpath $(KBUILD_OUTPUT)) returns an empty
> > string.
> >
> > Using an absolute directory resolves this problem, but I believe it
> > shouldn't be necessary.
> 
> 
> Agree.
> 
> I will apply the following fixup unless I have a better idea.
> 
> 
> 
> 
> diff --git a/scripts/package/install-extmod-build
> b/scripts/package/install-extmod-build
> index 64d958ee45f3..85af1573db31 100755
> --- a/scripts/package/install-extmod-build
> +++ b/scripts/package/install-extmod-build
> @@ -69,7 +69,7 @@ if [ "${CC}" != "${HOSTCC}" ]; then
>         #
>         # Use the single-target build to avoid the modpost invocation, which
>         # would overwrite Module.symvers.
> -       "${MAKE}" HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/
> +       "${MAKE}" O=. HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/
> 
>         cat <<-'EOF' >  "${destdir}/scripts/Kbuild"
>         subdir-y := basic
> @@ -78,7 +78,7 @@ if [ "${CC}" != "${HOSTCC}" ]; then
>         EOF
> 
>         # Run once again to rebuild scripts/basic/ and scripts/mod/modpost.
> -       "${MAKE}" HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/
> +       "${MAKE}" O=. HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/
> 
>         rm -f "${destdir}/Kbuild" "${destdir}/scripts/Kbuild"
>  fi
> 

Looks fine to me :)

If this is what you decide on, feel free to add my tags.

Tested-by: Charlie Jenkins <charlie@rivosinc.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>

> 
> 
> --
> Best Regards
> Masahiro Yamada

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-11-10  1:34 ` [PATCH v2 05/11] kbuild: change working directory to external module directory with M= Masahiro Yamada
                     ` (2 preceding siblings ...)
  2024-12-04 23:35   ` Charlie Jenkins
@ 2024-12-09 13:46   ` Thorsten Blum
  2024-12-09 13:55     ` Thorsten Blum
  2024-12-10 15:34   ` Jon Hunter
  2025-01-27 23:08   ` Qu Wenruo
  5 siblings, 1 reply; 33+ messages in thread
From: Thorsten Blum @ 2024-12-09 13:46 UTC (permalink / raw)
  To: Masahiro Yamada; +Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci

On 10. Nov 2024, at 02:34, Masahiro Yamada wrote:
> 
> Currently, Kbuild always operates in the output directory of the kernel,
> even when building external modules. This increases the risk of external
> module Makefiles attempting to write to the kernel directory.
> 
> This commit switches the working directory to the external module
> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> some build artifacts.
> 
> The command for building external modules maintains backward
> compatibility, but Makefiles that rely on working in the kernel
> directory may break. In such cases, $(objtree) and $(srctree) should
> be used to refer to the output and source directories of the kernel.
> 
> The appearance of the build log will change as follows:
> 
> [Before]
> 
>  $ make -C /path/to/my/linux M=/path/to/my/externel/module
>  make: Entering directory '/path/to/my/linux'
>    CC [M]  /path/to/my/externel/module/helloworld.o
>    MODPOST /path/to/my/externel/module/Module.symvers
>    CC [M]  /path/to/my/externel/module/helloworld.mod.o
>    CC [M]  /path/to/my/externel/module/.module-common.o
>    LD [M]  /path/to/my/externel/module/helloworld.ko
>  make: Leaving directory '/path/to/my/linux'
> 
> [After]
> 
>  $ make -C /path/to/my/linux M=/path/to/my/externel/module
>  make: Entering directory '/path/to/my/linux'
>  make[1]: Entering directory '/path/to/my/externel/module'
>    CC [M]  helloworld.o
>    MODPOST Module.symvers
>    CC [M]  helloworld.mod.o
>    CC [M]  .module-common.o
>    LD [M]  helloworld.ko
>  make[1]: Leaving directory '/path/to/my/externel/module'
>  make: Leaving directory '/path/to/my/linux'
> 
> Printing "Entering directory" twice is cumbersome. This will be
> addressed later.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---

Hi Masahiro,

I get the following error since this patch is in master, but only when
using COCCI= in combination with M=<relative or absolute path>.

It works when I either use COCCI= or M=, but not with both.

$ make coccicheck COCCI=scripts/coccinelle/misc/flexible_array.cocci M=arch/
make[1]: Entering directory '/home/fedora/linux/arch'
You have not explicitly specified the mode to use. Using default "report" mode.
Available modes are the following: patch, report, context, org, chain
You can specify the mode with "make coccicheck MODE=<mode>"
Note however that some modes are not implemented by some semantic patches.

Please check for false positives in the output before submitting a patch.
When using "patch" mode, carefully review the patch before submitting it.

grep: scripts/coccinelle/misc/flexible_array.cocci: No such file or directory
grep: scripts/coccinelle/misc/flexible_array.cocci: No such file or directory
/usr/bin/spatch -D report --no-show-diff --very-quiet --cocci-file scripts/coccinelle/misc/flexible_array.cocci --patch /home/fedora/linux --dir . -I /home/fedora/linux/arch/arm64/include -I /home/fedora/linux/arch/arm64/include/generated -I /home/fedora/linux/include -I /home/fedora/linux/include -I /home/fedora/linux/arch/arm64/include/uapi -I /home/fedora/linux/arch/arm64/include/generated/uapi -I /home/fedora/linux/include/uapi -I /home/fedora/linux/include/generated/uapi --include /home/fedora/linux/include/linux/compiler-version.h --include /home/fedora/linux/include/linux/kconfig.h --jobs 4 --chunksize 1
Fatal error: exception Sys_error("scripts/coccinelle/misc/flexible_array.cocci: No such file or directory")
coccicheck failed
make[2]: *** [/home/fedora/linux/Makefile:2089: coccicheck] Error 2
make[1]: *** [/home/fedora/linux/Makefile:251: __sub-make] Error 2
make[1]: Leaving directory '/home/fedora/linux/arch'
make: *** [Makefile:251: __sub-make] Error 2

Thanks,
Thorsten

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-12-09 13:46   ` Thorsten Blum
@ 2024-12-09 13:55     ` Thorsten Blum
  2024-12-10 10:47       ` Masahiro Yamada
  0 siblings, 1 reply; 33+ messages in thread
From: Thorsten Blum @ 2024-12-09 13:55 UTC (permalink / raw)
  To: Masahiro Yamada; +Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci

On 9. Dec 2024, at 14:46, Thorsten Blum wrote:
> On 10. Nov 2024, at 02:34, Masahiro Yamada wrote:
>> 
>> Currently, Kbuild always operates in the output directory of the kernel,
>> even when building external modules. This increases the risk of external
>> module Makefiles attempting to write to the kernel directory.
>> 
>> This commit switches the working directory to the external module
>> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
>> some build artifacts.
>> 
>> The command for building external modules maintains backward
>> compatibility, but Makefiles that rely on working in the kernel
>> directory may break. In such cases, $(objtree) and $(srctree) should
>> be used to refer to the output and source directories of the kernel.
>> 
>> The appearance of the build log will change as follows:
>> 
>> [Before]
>> 
>> $ make -C /path/to/my/linux M=/path/to/my/externel/module
>> make: Entering directory '/path/to/my/linux'
>>   CC [M]  /path/to/my/externel/module/helloworld.o
>>   MODPOST /path/to/my/externel/module/Module.symvers
>>   CC [M]  /path/to/my/externel/module/helloworld.mod.o
>>   CC [M]  /path/to/my/externel/module/.module-common.o
>>   LD [M]  /path/to/my/externel/module/helloworld.ko
>> make: Leaving directory '/path/to/my/linux'
>> 
>> [After]
>> 
>> $ make -C /path/to/my/linux M=/path/to/my/externel/module
>> make: Entering directory '/path/to/my/linux'
>> make[1]: Entering directory '/path/to/my/externel/module'
>>   CC [M]  helloworld.o
>>   MODPOST Module.symvers
>>   CC [M]  helloworld.mod.o
>>   CC [M]  .module-common.o
>>   LD [M]  helloworld.ko
>> make[1]: Leaving directory '/path/to/my/externel/module'
>> make: Leaving directory '/path/to/my/linux'
>> 
>> Printing "Entering directory" twice is cumbersome. This will be
>> addressed later.
>> 
>> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
>> ---
> 
> Hi Masahiro,
> 
> I get the following error since this patch is in master, but only when
> using COCCI= in combination with M=<relative or absolute path>.
> 
> It works when I either use COCCI= or M=, but not with both.

Using the absolute path of the cocci script fixes my problem, but this
used to work with relative paths too.

$ make coccicheck COCCI=$(pwd)/scripts/coccinelle/misc/flexible_array.cocci M=arch/

Thanks,
Thorsten


^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-12-09 13:55     ` Thorsten Blum
@ 2024-12-10 10:47       ` Masahiro Yamada
  2024-12-10 11:06         ` Thorsten Blum
  0 siblings, 1 reply; 33+ messages in thread
From: Masahiro Yamada @ 2024-12-10 10:47 UTC (permalink / raw)
  To: Thorsten Blum; +Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci

On Mon, Dec 9, 2024 at 10:56 PM Thorsten Blum <thorsten.blum@linux.dev> wrote:
>
> On 9. Dec 2024, at 14:46, Thorsten Blum wrote:
> > On 10. Nov 2024, at 02:34, Masahiro Yamada wrote:
> >>
> >> Currently, Kbuild always operates in the output directory of the kernel,
> >> even when building external modules. This increases the risk of external
> >> module Makefiles attempting to write to the kernel directory.
> >>
> >> This commit switches the working directory to the external module
> >> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> >> some build artifacts.
> >>
> >> The command for building external modules maintains backward
> >> compatibility, but Makefiles that rely on working in the kernel
> >> directory may break. In such cases, $(objtree) and $(srctree) should
> >> be used to refer to the output and source directories of the kernel.
> >>
> >> The appearance of the build log will change as follows:
> >>
> >> [Before]
> >>
> >> $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >> make: Entering directory '/path/to/my/linux'
> >>   CC [M]  /path/to/my/externel/module/helloworld.o
> >>   MODPOST /path/to/my/externel/module/Module.symvers
> >>   CC [M]  /path/to/my/externel/module/helloworld.mod.o
> >>   CC [M]  /path/to/my/externel/module/.module-common.o
> >>   LD [M]  /path/to/my/externel/module/helloworld.ko
> >> make: Leaving directory '/path/to/my/linux'
> >>
> >> [After]
> >>
> >> $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >> make: Entering directory '/path/to/my/linux'
> >> make[1]: Entering directory '/path/to/my/externel/module'
> >>   CC [M]  helloworld.o
> >>   MODPOST Module.symvers
> >>   CC [M]  helloworld.mod.o
> >>   CC [M]  .module-common.o
> >>   LD [M]  helloworld.ko
> >> make[1]: Leaving directory '/path/to/my/externel/module'
> >> make: Leaving directory '/path/to/my/linux'
> >>
> >> Printing "Entering directory" twice is cumbersome. This will be
> >> addressed later.
> >>
> >> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> >> ---
> >
> > Hi Masahiro,
> >
> > I get the following error since this patch is in master, but only when
> > using COCCI= in combination with M=<relative or absolute path>.
> >
> > It works when I either use COCCI= or M=, but not with both.
>
> Using the absolute path of the cocci script fixes my problem, but this
> used to work with relative paths too.
>
> $ make coccicheck COCCI=$(pwd)/scripts/coccinelle/misc/flexible_array.cocci M=arch/

M= looks a bit weird for the upstream code, but
I think using the absolute path is the right thing to do.


-- 
Best Regards
Masahiro Yamada

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-12-10 10:47       ` Masahiro Yamada
@ 2024-12-10 11:06         ` Thorsten Blum
  2024-12-11  2:36           ` Masahiro Yamada
  0 siblings, 1 reply; 33+ messages in thread
From: Thorsten Blum @ 2024-12-10 11:06 UTC (permalink / raw)
  To: Masahiro Yamada; +Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci

On 10. Dec 2024, at 11:47, Masahiro Yamada wrote:
> On Mon, Dec 9, 2024 at 10:56 PM Thorsten Blum wrote:
>> On 9. Dec 2024, at 14:46, Thorsten Blum wrote:
>>> On 10. Nov 2024, at 02:34, Masahiro Yamada wrote:
>>>> 
>>>> Currently, Kbuild always operates in the output directory of the kernel,
>>>> even when building external modules. This increases the risk of external
>>>> module Makefiles attempting to write to the kernel directory.
>>>> 
>>>> This commit switches the working directory to the external module
>>>> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
>>>> some build artifacts.
>>>> 
>>>> The command for building external modules maintains backward
>>>> compatibility, but Makefiles that rely on working in the kernel
>>>> directory may break. In such cases, $(objtree) and $(srctree) should
>>>> be used to refer to the output and source directories of the kernel.
>>>> 
>>>> The appearance of the build log will change as follows:
>>>> 
>>>> [Before]
>>>> 
>>>> $ make -C /path/to/my/linux M=/path/to/my/externel/module
>>>> make: Entering directory '/path/to/my/linux'
>>>> CC [M]  /path/to/my/externel/module/helloworld.o
>>>> MODPOST /path/to/my/externel/module/Module.symvers
>>>> CC [M]  /path/to/my/externel/module/helloworld.mod.o
>>>> CC [M]  /path/to/my/externel/module/.module-common.o
>>>> LD [M]  /path/to/my/externel/module/helloworld.ko
>>>> make: Leaving directory '/path/to/my/linux'
>>>> 
>>>> [After]
>>>> 
>>>> $ make -C /path/to/my/linux M=/path/to/my/externel/module
>>>> make: Entering directory '/path/to/my/linux'
>>>> make[1]: Entering directory '/path/to/my/externel/module'
>>>> CC [M]  helloworld.o
>>>> MODPOST Module.symvers
>>>> CC [M]  helloworld.mod.o
>>>> CC [M]  .module-common.o
>>>> LD [M]  helloworld.ko
>>>> make[1]: Leaving directory '/path/to/my/externel/module'
>>>> make: Leaving directory '/path/to/my/linux'
>>>> 
>>>> Printing "Entering directory" twice is cumbersome. This will be
>>>> addressed later.
>>>> 
>>>> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
>>>> ---
>>> 
>>> Hi Masahiro,
>>> 
>>> I get the following error since this patch is in master, but only when
>>> using COCCI= in combination with M=<relative or absolute path>.
>>> 
>>> It works when I either use COCCI= or M=, but not with both.
>> 
>> Using the absolute path of the cocci script fixes my problem, but this
>> used to work with relative paths too.
>> 
>> $ make coccicheck COCCI=$(pwd)/scripts/coccinelle/misc/flexible_array.cocci M=arch/
> 
> M= looks a bit weird for the upstream code, but
> I think using the absolute path is the right thing to do.

The documentation[1] uses M= and also COCCI= with relative paths and
some of the examples don't work anymore.

Could you try this one?

```
export COCCI=scripts/coccinelle/misc/irqf_oneshot.cocci
make coccicheck DEBUG_FILE="err.log" MODE=report SPFLAGS="--profile --show-trying" M=./drivers/mfd
```

I get this:

$ export COCCI=scripts/coccinelle/misc/irqf_oneshot.cocci
$ make coccicheck DEBUG_FILE="err.log" MODE=report SPFLAGS="--profile --show-trying" M=./drivers/mfd
make[1]: Entering directory '/home/fedora/linux/drivers/mfd'

Please check for false positives in the output before submitting a patch.
When using "patch" mode, carefully review the patch before submitting it.

grep: scripts/coccinelle/misc/irqf_oneshot.cocci: No such file or directory
grep: scripts/coccinelle/misc/irqf_oneshot.cocci: No such file or directory
coccicheck failed
make[2]: *** [/home/fedora/linux/Makefile:2089: coccicheck] Error 2
make[1]: *** [/home/fedora/linux/Makefile:251: __sub-make] Error 2
make[1]: Leaving directory '/home/fedora/linux/drivers/mfd'
make: *** [Makefile:251: __sub-make] Error 2

Thanks,
Thorsten

[1] https://www.kernel.org/doc/html/latest/dev-tools/coccinelle.html


^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-12-10 11:06         ` Thorsten Blum
@ 2024-12-11  2:36           ` Masahiro Yamada
  0 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-12-11  2:36 UTC (permalink / raw)
  To: Thorsten Blum; +Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci

On Tue, Dec 10, 2024 at 8:06 PM Thorsten Blum <thorsten.blum@linux.dev> wrote:
>
> On 10. Dec 2024, at 11:47, Masahiro Yamada wrote:
> > On Mon, Dec 9, 2024 at 10:56 PM Thorsten Blum wrote:
> >> On 9. Dec 2024, at 14:46, Thorsten Blum wrote:
> >>> On 10. Nov 2024, at 02:34, Masahiro Yamada wrote:
> >>>>
> >>>> Currently, Kbuild always operates in the output directory of the kernel,
> >>>> even when building external modules. This increases the risk of external
> >>>> module Makefiles attempting to write to the kernel directory.
> >>>>
> >>>> This commit switches the working directory to the external module
> >>>> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> >>>> some build artifacts.
> >>>>
> >>>> The command for building external modules maintains backward
> >>>> compatibility, but Makefiles that rely on working in the kernel
> >>>> directory may break. In such cases, $(objtree) and $(srctree) should
> >>>> be used to refer to the output and source directories of the kernel.
> >>>>
> >>>> The appearance of the build log will change as follows:
> >>>>
> >>>> [Before]
> >>>>
> >>>> $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >>>> make: Entering directory '/path/to/my/linux'
> >>>> CC [M]  /path/to/my/externel/module/helloworld.o
> >>>> MODPOST /path/to/my/externel/module/Module.symvers
> >>>> CC [M]  /path/to/my/externel/module/helloworld.mod.o
> >>>> CC [M]  /path/to/my/externel/module/.module-common.o
> >>>> LD [M]  /path/to/my/externel/module/helloworld.ko
> >>>> make: Leaving directory '/path/to/my/linux'
> >>>>
> >>>> [After]
> >>>>
> >>>> $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >>>> make: Entering directory '/path/to/my/linux'
> >>>> make[1]: Entering directory '/path/to/my/externel/module'
> >>>> CC [M]  helloworld.o
> >>>> MODPOST Module.symvers
> >>>> CC [M]  helloworld.mod.o
> >>>> CC [M]  .module-common.o
> >>>> LD [M]  helloworld.ko
> >>>> make[1]: Leaving directory '/path/to/my/externel/module'
> >>>> make: Leaving directory '/path/to/my/linux'
> >>>>
> >>>> Printing "Entering directory" twice is cumbersome. This will be
> >>>> addressed later.
> >>>>
> >>>> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> >>>> ---
> >>>
> >>> Hi Masahiro,
> >>>
> >>> I get the following error since this patch is in master, but only when
> >>> using COCCI= in combination with M=<relative or absolute path>.
> >>>
> >>> It works when I either use COCCI= or M=, but not with both.
> >>
> >> Using the absolute path of the cocci script fixes my problem, but this
> >> used to work with relative paths too.
> >>
> >> $ make coccicheck COCCI=$(pwd)/scripts/coccinelle/misc/flexible_array.cocci M=arch/
> >
> > M= looks a bit weird for the upstream code, but
> > I think using the absolute path is the right thing to do.
>
> The documentation[1] uses M= and also COCCI= with relative paths and
> some of the examples don't work anymore.

I know.

This is what cocci people hoped to work.

If something is broken in coccicheck, it must be fixed.




-- 
Best Regards
Masahiro Yamada

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-11-10  1:34 ` [PATCH v2 05/11] kbuild: change working directory to external module directory with M= Masahiro Yamada
                     ` (3 preceding siblings ...)
  2024-12-09 13:46   ` Thorsten Blum
@ 2024-12-10 15:34   ` Jon Hunter
  2024-12-11  2:39     ` Masahiro Yamada
  2025-01-27 23:08   ` Qu Wenruo
  5 siblings, 1 reply; 33+ messages in thread
From: Jon Hunter @ 2024-12-10 15:34 UTC (permalink / raw)
  To: Masahiro Yamada, linux-kbuild
  Cc: linux-kernel, rust-for-linux, cocci, linux-tegra@vger.kernel.org

Hi Masahiro,

On 10/11/2024 01:34, Masahiro Yamada wrote:
> Currently, Kbuild always operates in the output directory of the kernel,
> even when building external modules. This increases the risk of external
> module Makefiles attempting to write to the kernel directory.
> 
> This commit switches the working directory to the external module
> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> some build artifacts.
> 
> The command for building external modules maintains backward
> compatibility, but Makefiles that rely on working in the kernel
> directory may break. In such cases, $(objtree) and $(srctree) should
> be used to refer to the output and source directories of the kernel.
> 
> The appearance of the build log will change as follows:
> 
> [Before]
> 
>    $ make -C /path/to/my/linux M=/path/to/my/externel/module
>    make: Entering directory '/path/to/my/linux'
>      CC [M]  /path/to/my/externel/module/helloworld.o
>      MODPOST /path/to/my/externel/module/Module.symvers
>      CC [M]  /path/to/my/externel/module/helloworld.mod.o
>      CC [M]  /path/to/my/externel/module/.module-common.o
>      LD [M]  /path/to/my/externel/module/helloworld.ko
>    make: Leaving directory '/path/to/my/linux'
> 
> [After]
> 
>    $ make -C /path/to/my/linux M=/path/to/my/externel/module
>    make: Entering directory '/path/to/my/linux'
>    make[1]: Entering directory '/path/to/my/externel/module'
>      CC [M]  helloworld.o
>      MODPOST Module.symvers
>      CC [M]  helloworld.mod.o
>      CC [M]  .module-common.o
>      LD [M]  helloworld.ko
>    make[1]: Leaving directory '/path/to/my/externel/module'
>    make: Leaving directory '/path/to/my/linux'
> 
> Printing "Entering directory" twice is cumbersome. This will be
> addressed later.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>


Since this change I have been observing the following build error when 
building an external module ...

  MODPOST Module.symvers
ERROR: modpost: drivers/gpu/host1x/host1x: 'host1x_device_init' exported
     twice. Previous export was in drivers/gpu/host1x/host1x.ko
ERROR: modpost: drivers/gpu/host1x/host1x: 'host1x_device_exit' exported
     twice. Previous export was in drivers/gpu/host1x/host1x.ko

Now host1x is an upstream driver, but I have a local copy that using to 
stage development changes (and avoid polluting the upstream driver). 
Plus I can swap between which version I am using on a live system.

What I noticed is that previously the Modules.symvers for the external 
module had the full path of the external module for the name. However, 
now the name is just the relative path and in this case 
'drivers/gpu/host1x/host1x'. Hence, this clashes with the in-kernel 
driver and we get the 'exported twice' error.

I have been looking to see if there is a way to fix this because it has 
been a useful feature to override an upstream driver with a locally 
modified version.

Thanks
Jon

-- 
nvpublic


^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-12-10 15:34   ` Jon Hunter
@ 2024-12-11  2:39     ` Masahiro Yamada
  2024-12-11 12:21       ` Jon Hunter
  0 siblings, 1 reply; 33+ messages in thread
From: Masahiro Yamada @ 2024-12-11  2:39 UTC (permalink / raw)
  To: Jon Hunter
  Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci,
	linux-tegra@vger.kernel.org

On Wed, Dec 11, 2024 at 12:34 AM Jon Hunter <jonathanh@nvidia.com> wrote:
>
> Hi Masahiro,
>
> On 10/11/2024 01:34, Masahiro Yamada wrote:
> > Currently, Kbuild always operates in the output directory of the kernel,
> > even when building external modules. This increases the risk of external
> > module Makefiles attempting to write to the kernel directory.
> >
> > This commit switches the working directory to the external module
> > directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> > some build artifacts.
> >
> > The command for building external modules maintains backward
> > compatibility, but Makefiles that rely on working in the kernel
> > directory may break. In such cases, $(objtree) and $(srctree) should
> > be used to refer to the output and source directories of the kernel.
> >
> > The appearance of the build log will change as follows:
> >
> > [Before]
> >
> >    $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >    make: Entering directory '/path/to/my/linux'
> >      CC [M]  /path/to/my/externel/module/helloworld.o
> >      MODPOST /path/to/my/externel/module/Module.symvers
> >      CC [M]  /path/to/my/externel/module/helloworld.mod.o
> >      CC [M]  /path/to/my/externel/module/.module-common.o
> >      LD [M]  /path/to/my/externel/module/helloworld.ko
> >    make: Leaving directory '/path/to/my/linux'
> >
> > [After]
> >
> >    $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >    make: Entering directory '/path/to/my/linux'
> >    make[1]: Entering directory '/path/to/my/externel/module'
> >      CC [M]  helloworld.o
> >      MODPOST Module.symvers
> >      CC [M]  helloworld.mod.o
> >      CC [M]  .module-common.o
> >      LD [M]  helloworld.ko
> >    make[1]: Leaving directory '/path/to/my/externel/module'
> >    make: Leaving directory '/path/to/my/linux'
> >
> > Printing "Entering directory" twice is cumbersome. This will be
> > addressed later.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
>
>
> Since this change I have been observing the following build error when
> building an external module ...
>
>   MODPOST Module.symvers
> ERROR: modpost: drivers/gpu/host1x/host1x: 'host1x_device_init' exported
>      twice. Previous export was in drivers/gpu/host1x/host1x.ko
> ERROR: modpost: drivers/gpu/host1x/host1x: 'host1x_device_exit' exported
>      twice. Previous export was in drivers/gpu/host1x/host1x.ko
>
> Now host1x is an upstream driver, but I have a local copy that using to
> stage development changes (and avoid polluting the upstream driver).
> Plus I can swap between which version I am using on a live system.
>
> What I noticed is that previously the Modules.symvers for the external
> module had the full path of the external module for the name. However,
> now the name is just the relative path and in this case
> 'drivers/gpu/host1x/host1x'. Hence, this clashes with the in-kernel
> driver and we get the 'exported twice' error.
>
> I have been looking to see if there is a way to fix this because it has
> been a useful feature to override an upstream driver with a locally
> modified version.


I do not know how to reproduce it.

  if (s && (!external_module || s->module->is_vmlinux || s->module == mod)) {

is not checking the module path at all.
I do not understand why it was affected.



-- 
Best Regards
Masahiro Yamada

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-12-11  2:39     ` Masahiro Yamada
@ 2024-12-11 12:21       ` Jon Hunter
  2024-12-12  2:08         ` Masahiro Yamada
  0 siblings, 1 reply; 33+ messages in thread
From: Jon Hunter @ 2024-12-11 12:21 UTC (permalink / raw)
  To: Masahiro Yamada
  Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci,
	linux-tegra@vger.kernel.org


On 11/12/2024 02:39, Masahiro Yamada wrote:
> On Wed, Dec 11, 2024 at 12:34 AM Jon Hunter <jonathanh@nvidia.com> wrote:
>>
>> Hi Masahiro,
>>
>> On 10/11/2024 01:34, Masahiro Yamada wrote:
>>> Currently, Kbuild always operates in the output directory of the kernel,
>>> even when building external modules. This increases the risk of external
>>> module Makefiles attempting to write to the kernel directory.
>>>
>>> This commit switches the working directory to the external module
>>> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
>>> some build artifacts.
>>>
>>> The command for building external modules maintains backward
>>> compatibility, but Makefiles that rely on working in the kernel
>>> directory may break. In such cases, $(objtree) and $(srctree) should
>>> be used to refer to the output and source directories of the kernel.
>>>
>>> The appearance of the build log will change as follows:
>>>
>>> [Before]
>>>
>>>     $ make -C /path/to/my/linux M=/path/to/my/externel/module
>>>     make: Entering directory '/path/to/my/linux'
>>>       CC [M]  /path/to/my/externel/module/helloworld.o
>>>       MODPOST /path/to/my/externel/module/Module.symvers
>>>       CC [M]  /path/to/my/externel/module/helloworld.mod.o
>>>       CC [M]  /path/to/my/externel/module/.module-common.o
>>>       LD [M]  /path/to/my/externel/module/helloworld.ko
>>>     make: Leaving directory '/path/to/my/linux'
>>>
>>> [After]
>>>
>>>     $ make -C /path/to/my/linux M=/path/to/my/externel/module
>>>     make: Entering directory '/path/to/my/linux'
>>>     make[1]: Entering directory '/path/to/my/externel/module'
>>>       CC [M]  helloworld.o
>>>       MODPOST Module.symvers
>>>       CC [M]  helloworld.mod.o
>>>       CC [M]  .module-common.o
>>>       LD [M]  helloworld.ko
>>>     make[1]: Leaving directory '/path/to/my/externel/module'
>>>     make: Leaving directory '/path/to/my/linux'
>>>
>>> Printing "Entering directory" twice is cumbersome. This will be
>>> addressed later.
>>>
>>> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
>>
>>
>> Since this change I have been observing the following build error when
>> building an external module ...
>>
>>    MODPOST Module.symvers
>> ERROR: modpost: drivers/gpu/host1x/host1x: 'host1x_device_init' exported
>>       twice. Previous export was in drivers/gpu/host1x/host1x.ko
>> ERROR: modpost: drivers/gpu/host1x/host1x: 'host1x_device_exit' exported
>>       twice. Previous export was in drivers/gpu/host1x/host1x.ko
>>
>> Now host1x is an upstream driver, but I have a local copy that using to
>> stage development changes (and avoid polluting the upstream driver).
>> Plus I can swap between which version I am using on a live system.
>>
>> What I noticed is that previously the Modules.symvers for the external
>> module had the full path of the external module for the name. However,
>> now the name is just the relative path and in this case
>> 'drivers/gpu/host1x/host1x'. Hence, this clashes with the in-kernel
>> driver and we get the 'exported twice' error.
>>
>> I have been looking to see if there is a way to fix this because it has
>> been a useful feature to override an upstream driver with a locally
>> modified version.
> 
> 
> I do not know how to reproduce it.
> 
>    if (s && (!external_module || s->module->is_vmlinux || s->module == mod)) {
> 
> is not checking the module path at all.
> I do not understand why it was affected.


So this is not explicitly checking the path, but comparing the contents
of the Module.symvers before and after this change for the external
module I see ...

$ grep -r host1x_device_init Module.symvers
0x00000000      host1x_device_init      /absolute/path/to/drivers/gpu/host1x/host1x        EXPORT_SYMBOL

And now I see ...

$ grep -r host1x_device_init Module.symvers
0x00000000      host1x_device_init      drivers/gpu/host1x/host1x  EXPORT_SYMBOL

So the problem is that now there is no longer an absolute path in the
external modules Module.symvers and so conflicts with the kernel's.

Does that make sense?

Jon

-- 
nvpublic


^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-12-11 12:21       ` Jon Hunter
@ 2024-12-12  2:08         ` Masahiro Yamada
  2024-12-12  6:00           ` Jon Hunter
  0 siblings, 1 reply; 33+ messages in thread
From: Masahiro Yamada @ 2024-12-12  2:08 UTC (permalink / raw)
  To: Jon Hunter
  Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci,
	linux-tegra@vger.kernel.org

On Wed, Dec 11, 2024 at 9:21 PM Jon Hunter <jonathanh@nvidia.com> wrote:
>
>
> On 11/12/2024 02:39, Masahiro Yamada wrote:
> > On Wed, Dec 11, 2024 at 12:34 AM Jon Hunter <jonathanh@nvidia.com> wrote:
> >>
> >> Hi Masahiro,
> >>
> >> On 10/11/2024 01:34, Masahiro Yamada wrote:
> >>> Currently, Kbuild always operates in the output directory of the kernel,
> >>> even when building external modules. This increases the risk of external
> >>> module Makefiles attempting to write to the kernel directory.
> >>>
> >>> This commit switches the working directory to the external module
> >>> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> >>> some build artifacts.
> >>>
> >>> The command for building external modules maintains backward
> >>> compatibility, but Makefiles that rely on working in the kernel
> >>> directory may break. In such cases, $(objtree) and $(srctree) should
> >>> be used to refer to the output and source directories of the kernel.
> >>>
> >>> The appearance of the build log will change as follows:
> >>>
> >>> [Before]
> >>>
> >>>     $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >>>     make: Entering directory '/path/to/my/linux'
> >>>       CC [M]  /path/to/my/externel/module/helloworld.o
> >>>       MODPOST /path/to/my/externel/module/Module.symvers
> >>>       CC [M]  /path/to/my/externel/module/helloworld.mod.o
> >>>       CC [M]  /path/to/my/externel/module/.module-common.o
> >>>       LD [M]  /path/to/my/externel/module/helloworld.ko
> >>>     make: Leaving directory '/path/to/my/linux'
> >>>
> >>> [After]
> >>>
> >>>     $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >>>     make: Entering directory '/path/to/my/linux'
> >>>     make[1]: Entering directory '/path/to/my/externel/module'
> >>>       CC [M]  helloworld.o
> >>>       MODPOST Module.symvers
> >>>       CC [M]  helloworld.mod.o
> >>>       CC [M]  .module-common.o
> >>>       LD [M]  helloworld.ko
> >>>     make[1]: Leaving directory '/path/to/my/externel/module'
> >>>     make: Leaving directory '/path/to/my/linux'
> >>>
> >>> Printing "Entering directory" twice is cumbersome. This will be
> >>> addressed later.
> >>>
> >>> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> >>
> >>
> >> Since this change I have been observing the following build error when
> >> building an external module ...
> >>
> >>    MODPOST Module.symvers
> >> ERROR: modpost: drivers/gpu/host1x/host1x: 'host1x_device_init' exported
> >>       twice. Previous export was in drivers/gpu/host1x/host1x.ko
> >> ERROR: modpost: drivers/gpu/host1x/host1x: 'host1x_device_exit' exported
> >>       twice. Previous export was in drivers/gpu/host1x/host1x.ko
> >>
> >> Now host1x is an upstream driver, but I have a local copy that using to
> >> stage development changes (and avoid polluting the upstream driver).
> >> Plus I can swap between which version I am using on a live system.
> >>
> >> What I noticed is that previously the Modules.symvers for the external
> >> module had the full path of the external module for the name. However,
> >> now the name is just the relative path and in this case
> >> 'drivers/gpu/host1x/host1x'. Hence, this clashes with the in-kernel
> >> driver and we get the 'exported twice' error.
> >>
> >> I have been looking to see if there is a way to fix this because it has
> >> been a useful feature to override an upstream driver with a locally
> >> modified version.
> >
> >
> > I do not know how to reproduce it.
> >
> >    if (s && (!external_module || s->module->is_vmlinux || s->module == mod)) {
> >
> > is not checking the module path at all.
> > I do not understand why it was affected.
>
>
> So this is not explicitly checking the path, but comparing the contents
> of the Module.symvers before and after this change for the external
> module I see ...
>
> $ grep -r host1x_device_init Module.symvers
> 0x00000000      host1x_device_init      /absolute/path/to/drivers/gpu/host1x/host1x        EXPORT_SYMBOL
>
> And now I see ...
>
> $ grep -r host1x_device_init Module.symvers
> 0x00000000      host1x_device_init      drivers/gpu/host1x/host1x  EXPORT_SYMBOL
>
> So the problem is that now there is no longer an absolute path in the
> external modules Module.symvers and so conflicts with the kernel's.
>
> Does that make sense?


As I said, I do not know how to reproduce it.

Please provide the steps to reproduce it.





--
Best Regards
Masahiro Yamada

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-12-12  2:08         ` Masahiro Yamada
@ 2024-12-12  6:00           ` Jon Hunter
  2024-12-12 15:49             ` Masahiro Yamada
  0 siblings, 1 reply; 33+ messages in thread
From: Jon Hunter @ 2024-12-12  6:00 UTC (permalink / raw)
  To: Masahiro Yamada
  Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci,
	linux-tegra@vger.kernel.org


On 12/12/2024 02:08, Masahiro Yamada wrote:
> On Wed, Dec 11, 2024 at 9:21 PM Jon Hunter <jonathanh@nvidia.com> wrote:
>>
>>
>> On 11/12/2024 02:39, Masahiro Yamada wrote:
>>> On Wed, Dec 11, 2024 at 12:34 AM Jon Hunter <jonathanh@nvidia.com> wrote:
>>>>
>>>> Hi Masahiro,
>>>>
>>>> On 10/11/2024 01:34, Masahiro Yamada wrote:
>>>>> Currently, Kbuild always operates in the output directory of the kernel,
>>>>> even when building external modules. This increases the risk of external
>>>>> module Makefiles attempting to write to the kernel directory.
>>>>>
>>>>> This commit switches the working directory to the external module
>>>>> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
>>>>> some build artifacts.
>>>>>
>>>>> The command for building external modules maintains backward
>>>>> compatibility, but Makefiles that rely on working in the kernel
>>>>> directory may break. In such cases, $(objtree) and $(srctree) should
>>>>> be used to refer to the output and source directories of the kernel.
>>>>>
>>>>> The appearance of the build log will change as follows:
>>>>>
>>>>> [Before]
>>>>>
>>>>>      $ make -C /path/to/my/linux M=/path/to/my/externel/module
>>>>>      make: Entering directory '/path/to/my/linux'
>>>>>        CC [M]  /path/to/my/externel/module/helloworld.o
>>>>>        MODPOST /path/to/my/externel/module/Module.symvers
>>>>>        CC [M]  /path/to/my/externel/module/helloworld.mod.o
>>>>>        CC [M]  /path/to/my/externel/module/.module-common.o
>>>>>        LD [M]  /path/to/my/externel/module/helloworld.ko
>>>>>      make: Leaving directory '/path/to/my/linux'
>>>>>
>>>>> [After]
>>>>>
>>>>>      $ make -C /path/to/my/linux M=/path/to/my/externel/module
>>>>>      make: Entering directory '/path/to/my/linux'
>>>>>      make[1]: Entering directory '/path/to/my/externel/module'
>>>>>        CC [M]  helloworld.o
>>>>>        MODPOST Module.symvers
>>>>>        CC [M]  helloworld.mod.o
>>>>>        CC [M]  .module-common.o
>>>>>        LD [M]  helloworld.ko
>>>>>      make[1]: Leaving directory '/path/to/my/externel/module'
>>>>>      make: Leaving directory '/path/to/my/linux'
>>>>>
>>>>> Printing "Entering directory" twice is cumbersome. This will be
>>>>> addressed later.
>>>>>
>>>>> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
>>>>
>>>>
>>>> Since this change I have been observing the following build error when
>>>> building an external module ...
>>>>
>>>>     MODPOST Module.symvers
>>>> ERROR: modpost: drivers/gpu/host1x/host1x: 'host1x_device_init' exported
>>>>        twice. Previous export was in drivers/gpu/host1x/host1x.ko
>>>> ERROR: modpost: drivers/gpu/host1x/host1x: 'host1x_device_exit' exported
>>>>        twice. Previous export was in drivers/gpu/host1x/host1x.ko
>>>>
>>>> Now host1x is an upstream driver, but I have a local copy that using to
>>>> stage development changes (and avoid polluting the upstream driver).
>>>> Plus I can swap between which version I am using on a live system.
>>>>
>>>> What I noticed is that previously the Modules.symvers for the external
>>>> module had the full path of the external module for the name. However,
>>>> now the name is just the relative path and in this case
>>>> 'drivers/gpu/host1x/host1x'. Hence, this clashes with the in-kernel
>>>> driver and we get the 'exported twice' error.
>>>>
>>>> I have been looking to see if there is a way to fix this because it has
>>>> been a useful feature to override an upstream driver with a locally
>>>> modified version.
>>>
>>>
>>> I do not know how to reproduce it.
>>>
>>>     if (s && (!external_module || s->module->is_vmlinux || s->module == mod)) {
>>>
>>> is not checking the module path at all.
>>> I do not understand why it was affected.
>>
>>
>> So this is not explicitly checking the path, but comparing the contents
>> of the Module.symvers before and after this change for the external
>> module I see ...
>>
>> $ grep -r host1x_device_init Module.symvers
>> 0x00000000      host1x_device_init      /absolute/path/to/drivers/gpu/host1x/host1x        EXPORT_SYMBOL
>>
>> And now I see ...
>>
>> $ grep -r host1x_device_init Module.symvers
>> 0x00000000      host1x_device_init      drivers/gpu/host1x/host1x  EXPORT_SYMBOL
>>
>> So the problem is that now there is no longer an absolute path in the
>> external modules Module.symvers and so conflicts with the kernel's.
>>
>> Does that make sense?
> 
> 
> As I said, I do not know how to reproduce it.
> 
> Please provide the steps to reproduce it.

Got it! The steps would be ...

1. Create an external module by copying using an existing upstream
    driver (such as host1x).
2. Create a new external module that uses the external module from step
    1 and uses KBUILD_EXTRA_SYMBOLS to reference the Module.symvers for
    the driver in step 1.

Thanks!
Jon

-- 
nvpublic


^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-12-12  6:00           ` Jon Hunter
@ 2024-12-12 15:49             ` Masahiro Yamada
  0 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-12-12 15:49 UTC (permalink / raw)
  To: Jon Hunter
  Cc: linux-kbuild, linux-kernel, rust-for-linux, cocci,
	linux-tegra@vger.kernel.org

On Thu, Dec 12, 2024 at 3:00 PM Jon Hunter <jonathanh@nvidia.com> wrote:
>
>
> On 12/12/2024 02:08, Masahiro Yamada wrote:
> > On Wed, Dec 11, 2024 at 9:21 PM Jon Hunter <jonathanh@nvidia.com> wrote:
> >>
> >>
> >> On 11/12/2024 02:39, Masahiro Yamada wrote:
> >>> On Wed, Dec 11, 2024 at 12:34 AM Jon Hunter <jonathanh@nvidia.com> wrote:
> >>>>
> >>>> Hi Masahiro,
> >>>>
> >>>> On 10/11/2024 01:34, Masahiro Yamada wrote:
> >>>>> Currently, Kbuild always operates in the output directory of the kernel,
> >>>>> even when building external modules. This increases the risk of external
> >>>>> module Makefiles attempting to write to the kernel directory.
> >>>>>
> >>>>> This commit switches the working directory to the external module
> >>>>> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> >>>>> some build artifacts.
> >>>>>
> >>>>> The command for building external modules maintains backward
> >>>>> compatibility, but Makefiles that rely on working in the kernel
> >>>>> directory may break. In such cases, $(objtree) and $(srctree) should
> >>>>> be used to refer to the output and source directories of the kernel.
> >>>>>
> >>>>> The appearance of the build log will change as follows:
> >>>>>
> >>>>> [Before]
> >>>>>
> >>>>>      $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >>>>>      make: Entering directory '/path/to/my/linux'
> >>>>>        CC [M]  /path/to/my/externel/module/helloworld.o
> >>>>>        MODPOST /path/to/my/externel/module/Module.symvers
> >>>>>        CC [M]  /path/to/my/externel/module/helloworld.mod.o
> >>>>>        CC [M]  /path/to/my/externel/module/.module-common.o
> >>>>>        LD [M]  /path/to/my/externel/module/helloworld.ko
> >>>>>      make: Leaving directory '/path/to/my/linux'
> >>>>>
> >>>>> [After]
> >>>>>
> >>>>>      $ make -C /path/to/my/linux M=/path/to/my/externel/module
> >>>>>      make: Entering directory '/path/to/my/linux'
> >>>>>      make[1]: Entering directory '/path/to/my/externel/module'
> >>>>>        CC [M]  helloworld.o
> >>>>>        MODPOST Module.symvers
> >>>>>        CC [M]  helloworld.mod.o
> >>>>>        CC [M]  .module-common.o
> >>>>>        LD [M]  helloworld.ko
> >>>>>      make[1]: Leaving directory '/path/to/my/externel/module'
> >>>>>      make: Leaving directory '/path/to/my/linux'
> >>>>>
> >>>>> Printing "Entering directory" twice is cumbersome. This will be
> >>>>> addressed later.
> >>>>>
> >>>>> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> >>>>
> >>>>
> >>>> Since this change I have been observing the following build error when
> >>>> building an external module ...
> >>>>
> >>>>     MODPOST Module.symvers
> >>>> ERROR: modpost: drivers/gpu/host1x/host1x: 'host1x_device_init' exported
> >>>>        twice. Previous export was in drivers/gpu/host1x/host1x.ko
> >>>> ERROR: modpost: drivers/gpu/host1x/host1x: 'host1x_device_exit' exported
> >>>>        twice. Previous export was in drivers/gpu/host1x/host1x.ko
> >>>>
> >>>> Now host1x is an upstream driver, but I have a local copy that using to
> >>>> stage development changes (and avoid polluting the upstream driver).
> >>>> Plus I can swap between which version I am using on a live system.
> >>>>
> >>>> What I noticed is that previously the Modules.symvers for the external
> >>>> module had the full path of the external module for the name. However,
> >>>> now the name is just the relative path and in this case
> >>>> 'drivers/gpu/host1x/host1x'. Hence, this clashes with the in-kernel
> >>>> driver and we get the 'exported twice' error.
> >>>>
> >>>> I have been looking to see if there is a way to fix this because it has
> >>>> been a useful feature to override an upstream driver with a locally
> >>>> modified version.
> >>>
> >>>
> >>> I do not know how to reproduce it.
> >>>
> >>>     if (s && (!external_module || s->module->is_vmlinux || s->module == mod)) {
> >>>
> >>> is not checking the module path at all.
> >>> I do not understand why it was affected.
> >>
> >>
> >> So this is not explicitly checking the path, but comparing the contents
> >> of the Module.symvers before and after this change for the external
> >> module I see ...
> >>
> >> $ grep -r host1x_device_init Module.symvers
> >> 0x00000000      host1x_device_init      /absolute/path/to/drivers/gpu/host1x/host1x        EXPORT_SYMBOL
> >>
> >> And now I see ...
> >>
> >> $ grep -r host1x_device_init Module.symvers
> >> 0x00000000      host1x_device_init      drivers/gpu/host1x/host1x  EXPORT_SYMBOL
> >>
> >> So the problem is that now there is no longer an absolute path in the
> >> external modules Module.symvers and so conflicts with the kernel's.
> >>
> >> Does that make sense?
> >
> >
> > As I said, I do not know how to reproduce it.
> >
> > Please provide the steps to reproduce it.
>
> Got it! The steps would be ...
>
> 1. Create an external module by copying using an existing upstream
>     driver (such as host1x).
> 2. Create a new external module that uses the external module from step
>     1 and uses KBUILD_EXTRA_SYMBOLS to reference the Module.symvers for
>     the driver in step 1.
>
> Thanks!
> Jon


OK, now I understand, and posted a patch.
Thanks.

-- 
Best Regards
Masahiro Yamada

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 05/11] kbuild: change working directory to external module directory with M=
  2024-11-10  1:34 ` [PATCH v2 05/11] kbuild: change working directory to external module directory with M= Masahiro Yamada
                     ` (4 preceding siblings ...)
  2024-12-10 15:34   ` Jon Hunter
@ 2025-01-27 23:08   ` Qu Wenruo
  5 siblings, 0 replies; 33+ messages in thread
From: Qu Wenruo @ 2025-01-27 23:08 UTC (permalink / raw)
  To: Masahiro Yamada, linux-kbuild; +Cc: linux-kernel, rust-for-linux, cocci

Hi Masahiro-san,

Thanks for your contribution, but it looks like this is breaking quite
some vim/nvim quick fixes.

If there is some compiling errors/warnings, the path will be the one
inside the module directory, no matter if it's out-of-tree or upstreamed.

Is there anyway to get back the full filename so that vim/nvim quick fix
can work again?

Thanks,
Qu

在 2024/11/10 12:04, Masahiro Yamada 写道:
> Currently, Kbuild always operates in the output directory of the kernel,
> even when building external modules. This increases the risk of external
> module Makefiles attempting to write to the kernel directory.
>
> This commit switches the working directory to the external module
> directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> some build artifacts.
>
> The command for building external modules maintains backward
> compatibility, but Makefiles that rely on working in the kernel
> directory may break. In such cases, $(objtree) and $(srctree) should
> be used to refer to the output and source directories of the kernel.
>
> The appearance of the build log will change as follows:
>
> [Before]
>
>    $ make -C /path/to/my/linux M=/path/to/my/externel/module
>    make: Entering directory '/path/to/my/linux'
>      CC [M]  /path/to/my/externel/module/helloworld.o
>      MODPOST /path/to/my/externel/module/Module.symvers
>      CC [M]  /path/to/my/externel/module/helloworld.mod.o
>      CC [M]  /path/to/my/externel/module/.module-common.o
>      LD [M]  /path/to/my/externel/module/helloworld.ko
>    make: Leaving directory '/path/to/my/linux'
>
> [After]
>
>    $ make -C /path/to/my/linux M=/path/to/my/externel/module
>    make: Entering directory '/path/to/my/linux'
>    make[1]: Entering directory '/path/to/my/externel/module'
>      CC [M]  helloworld.o
>      MODPOST Module.symvers
>      CC [M]  helloworld.mod.o
>      CC [M]  .module-common.o
>      LD [M]  helloworld.ko
>    make[1]: Leaving directory '/path/to/my/externel/module'
>    make: Leaving directory '/path/to/my/linux'
>
> Printing "Entering directory" twice is cumbersome. This will be
> addressed later.
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
>
> Changes in v2:
>   - Introduce a new 'srcroot' variable and clean-up code
>   - Reword Documentation/dev-tools/coccinelle.rst
>
>   Documentation/dev-tools/coccinelle.rst | 20 ++-----
>   Documentation/kbuild/makefiles.rst     | 14 +++++
>   Makefile                               | 80 +++++++++++++++-----------
>   rust/Makefile                          |  4 +-
>   scripts/Makefile.build                 |  2 +-
>   scripts/Makefile.clean                 |  2 +-
>   scripts/Makefile.compiler              |  2 +-
>   scripts/Makefile.modpost               |  6 +-
>   scripts/coccicheck                     |  6 +-
>   scripts/nsdeps                         |  8 +--
>   scripts/package/install-extmod-build   |  7 +++
>   11 files changed, 85 insertions(+), 66 deletions(-)
>
> diff --git a/Documentation/dev-tools/coccinelle.rst b/Documentation/dev-tools/coccinelle.rst
> index 535ce126fb4f..6e70a1e9a3c0 100644
> --- a/Documentation/dev-tools/coccinelle.rst
> +++ b/Documentation/dev-tools/coccinelle.rst
> @@ -250,25 +250,17 @@ variables for .cocciconfig is as follows:
>   - Your directory from which spatch is called is processed next
>   - The directory provided with the ``--dir`` option is processed last, if used
>
> -Since coccicheck runs through make, it naturally runs from the kernel
> -proper dir; as such the second rule above would be implied for picking up a
> -.cocciconfig when using ``make coccicheck``.
> -
>   ``make coccicheck`` also supports using M= targets. If you do not supply
>   any M= target, it is assumed you want to target the entire kernel.
>   The kernel coccicheck script has::
>
> -    if [ "$KBUILD_EXTMOD" = "" ] ; then
> -        OPTIONS="--dir $srctree $COCCIINCLUDE"
> -    else
> -        OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
> -    fi
> +    OPTIONS="--dir $srcroot $COCCIINCLUDE"
>
> -KBUILD_EXTMOD is set when an explicit target with M= is used. For both cases
> -the spatch ``--dir`` argument is used, as such third rule applies when whether
> -M= is used or not, and when M= is used the target directory can have its own
> -.cocciconfig file. When M= is not passed as an argument to coccicheck the
> -target directory is the same as the directory from where spatch was called.
> +Here, $srcroot refers to the source directory of the target: it points to the
> +external module's source directory when M= used, and otherwise, to the kernel
> +source directory. The third rule ensures the spatch reads the .cocciconfig from
> +the target directory, allowing external modules to have their own .cocciconfig
> +file.
>
>   If not using the kernel's coccicheck target, keep the above precedence
>   order logic of .cocciconfig reading. If using the kernel's coccicheck target,
> diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
> index 7964e0c245ae..d36519f194dc 100644
> --- a/Documentation/kbuild/makefiles.rst
> +++ b/Documentation/kbuild/makefiles.rst
> @@ -449,6 +449,20 @@ $(obj)
>     to prerequisites are referenced with $(src) (because they are not
>     generated files).
>
> +$(srcroot)
> +  $(srcroot) refers to the root of the source you are building, which can be
> +  either the kernel source or the external modules source, depending on whether
> +  KBUILD_EXTMOD is set. This can be either a relative or an absolute path, but
> +  if KBUILD_ABS_SRCTREE=1 is set, it is always an absolute path.
> +
> +$(srctree)
> +  $(srctree) refers to the root of the kernel source tree. When building the
> +  kernel, this is the same as $(srcroot).
> +
> +$(objtree)
> +  $(objtree) refers to the root of the kernel object tree. It is ``.`` when
> +  building the kernel, but it is different when building external modules.
> +
>   $(kecho)
>     echoing information to user in a rule is often a good practice
>     but when execution ``make -s`` one does not expect to see any output
> diff --git a/Makefile b/Makefile
> index cf1d55560ae2..e5f7ac7647a7 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -180,7 +180,24 @@ ifeq ("$(origin O)", "command line")
>     KBUILD_OUTPUT := $(O)
>   endif
>
> -output := $(KBUILD_OUTPUT)
> +ifdef KBUILD_EXTMOD
> +    ifdef KBUILD_OUTPUT
> +        objtree := $(realpath $(KBUILD_OUTPUT))
> +        $(if $(objtree),,$(error specified kernel directory "$(KBUILD_OUTPUT)" does not exist))
> +    else
> +        objtree := $(CURDIR)
> +    endif
> +    output := $(KBUILD_EXTMOD)
> +    # KBUILD_EXTMOD might be a relative path. Remember its absolute path before
> +    # Make changes the working directory.
> +    srcroot := $(realpath $(KBUILD_EXTMOD))
> +    $(if $(srcroot),,$(error specified external module directory "$(KBUILD_EXTMOD)" does not exist))
> +else
> +    objtree := .
> +    output := $(KBUILD_OUTPUT)
> +endif
> +
> +export objtree srcroot
>
>   # Do we want to change the working directory?
>   ifneq ($(output),)
> @@ -230,35 +247,33 @@ else # need-sub-make
>
>   # We process the rest of the Makefile if this is the final invocation of make
>
> -ifeq ($(abs_srctree),$(CURDIR))
> -        # building in the source tree
> -        srctree := .
> -	building_out_of_srctree :=
> +ifndef KBUILD_EXTMOD
> +srcroot := $(abs_srctree)
> +endif
> +
> +ifeq ($(srcroot),$(CURDIR))
> +building_out_of_srctree :=
>   else
> -        ifeq ($(abs_srctree)/,$(dir $(CURDIR)))
> -                # building in a subdirectory of the source tree
> -                srctree := ..
> -        else
> -                srctree := $(abs_srctree)
> -        endif
> -	building_out_of_srctree := 1
> +export building_out_of_srctree :=1
>   endif
>
> -ifneq ($(KBUILD_ABS_SRCTREE),)
> -srctree := $(abs_srctree)
> +ifdef KBUILD_ABS_SRCTREE
> +    # Do not nothing. Use the absolute path.
> +else ifeq ($(srcroot),$(CURDIR))
> +    # Building in the source.
> +    srcroot := .
> +else ifeq ($(srcroot)/,$(dir $(CURDIR)))
> +    # Building in a subdirectory of the source.
> +    srcroot := ..
>   endif
>
> -objtree		:= .
> +export srctree := $(if $(KBUILD_EXTMOD),$(abs_srctree),$(srcroot))
>
> -VPATH		:=
> -
> -ifeq ($(KBUILD_EXTMOD),)
>   ifdef building_out_of_srctree
> -VPATH		:= $(srctree)
> +export VPATH := $(srcroot)
> +else
> +VPATH :=
>   endif
> -endif
> -
> -export building_out_of_srctree srctree objtree VPATH
>
>   # To make sure we do not include .config for any of the *config targets
>   # catch them early, and hand them over to scripts/kconfig/Makefile
> @@ -711,7 +726,7 @@ endif
>   # in addition to whatever we do anyway.
>   # Just "make" or "make all" shall build modules as well
>
> -ifneq ($(filter all modules nsdeps %compile_commands.json clang-%,$(MAKECMDGOALS)),)
> +ifneq ($(filter all modules nsdeps compile_commands.json clang-%,$(MAKECMDGOALS)),)
>     KBUILD_MODULES := 1
>   endif
>
> @@ -1107,7 +1122,7 @@ export MODLIB
>
>   PHONY += prepare0
>
> -export extmod_prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)
> +export extmod_prefix =
>   export MODORDER := $(extmod_prefix)modules.order
>   export MODULES_NSDEPS := $(extmod_prefix)modules.nsdeps
>
> @@ -1799,14 +1814,10 @@ filechk_kernel.release = echo $(KERNELRELEASE)
>   KBUILD_BUILTIN :=
>   KBUILD_MODULES := 1
>
> -build-dir := $(KBUILD_EXTMOD)
> +build-dir := .
>
> -compile_commands.json: $(extmod_prefix)compile_commands.json
> -PHONY += compile_commands.json
> -
> -clean-dirs := $(KBUILD_EXTMOD)
> -clean: private rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps \
> -	$(KBUILD_EXTMOD)/compile_commands.json
> +clean-dirs := .
> +clean: private rm-files := Module.symvers modules.nsdeps compile_commands.json
>
>   PHONY += prepare
>   # now expand this into a simple variable to reduce the cost of shell evaluations
> @@ -1948,7 +1959,7 @@ $(clean-dirs):
>
>   clean: $(clean-dirs)
>   	$(call cmd,rmfiles)
> -	@find $(or $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
> +	@find . $(RCS_FIND_IGNORE) \
>   		\( -name '*.[aios]' -o -name '*.rsi' -o -name '*.ko' -o -name '.*.cmd' \
>   		-o -name '*.ko.*' \
>   		-o -name '*.dtb' -o -name '*.dtbo' \
> @@ -1981,7 +1992,12 @@ tags TAGS cscope gtags: FORCE
>   PHONY += rust-analyzer
>   rust-analyzer:
>   	+$(Q)$(CONFIG_SHELL) $(srctree)/scripts/rust_is_available.sh
> +ifdef KBUILD_EXTMOD
> +# FIXME: external modules must not descend into a sub-directory of the kernel
> +	$(Q)$(MAKE) $(build)=$(objtree)/rust src=$(srctree)/rust $@
> +else
>   	$(Q)$(MAKE) $(build)=rust $@
> +endif
>
>   # Script to generate missing namespace dependencies
>   # ---------------------------------------------------------------------------
> diff --git a/rust/Makefile b/rust/Makefile
> index b5e0a73b78f3..742740816c4b 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -362,8 +362,8 @@ rust-analyzer:
>   	$(Q)$(srctree)/scripts/generate_rust_analyzer.py \
>   		--cfgs='core=$(core-cfgs)' --cfgs='alloc=$(alloc-cfgs)' \
>   		$(realpath $(srctree)) $(realpath $(objtree)) \
> -		$(rustc_sysroot) $(RUST_LIB_SRC) $(KBUILD_EXTMOD) > \
> -		$(if $(KBUILD_EXTMOD),$(extmod_prefix),$(objtree))/rust-project.json
> +		$(rustc_sysroot) $(RUST_LIB_SRC) $(if $(KBUILD_EXTMOD),$(srcroot)) \
> +		> rust-project.json
>
>   redirect-intrinsics = \
>   	__addsf3 __eqsf2 __extendsfdf2 __gesf2 __lesf2 __ltsf2 __mulsf3 __nesf2 __truncdfsf2 __unordsf2 \
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 64cd046f8fd8..1aa928a6fb4f 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -3,7 +3,7 @@
>   # Building
>   # ==========================================================================
>
> -src := $(if $(VPATH),$(VPATH)/)$(obj)
> +src := $(srcroot)/$(obj)
>
>   PHONY := $(obj)/
>   $(obj)/:
> diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean
> index 4fcfab40ed61..6ead00ec7313 100644
> --- a/scripts/Makefile.clean
> +++ b/scripts/Makefile.clean
> @@ -3,7 +3,7 @@
>   # Cleaning up
>   # ==========================================================================
>
> -src := $(if $(VPATH),$(VPATH)/)$(obj)
> +src := $(srcroot)/$(obj)
>
>   PHONY := __clean
>   __clean:
> diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
> index e0842496d26e..8c1029687e2e 100644
> --- a/scripts/Makefile.compiler
> +++ b/scripts/Makefile.compiler
> @@ -13,7 +13,7 @@ cc-cross-prefix = $(firstword $(foreach c, $(1), \
>   			$(if $(shell command -v -- $(c)gcc 2>/dev/null), $(c))))
>
>   # output directory for tests below
> -TMPOUT = $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/).tmp_$$$$
> +TMPOUT = .tmp_$$$$
>
>   # try-run
>   # Usage: option = $(call try-run, $(CC)...-o "$$TMP",option-ok,otherwise)
> diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
> index 12e7c15d099c..78d2ca4f25f5 100644
> --- a/scripts/Makefile.modpost
> +++ b/scripts/Makefile.modpost
> @@ -111,13 +111,13 @@ endif
>   else
>
>   # set src + obj - they may be used in the modules's Makefile
> -obj := $(KBUILD_EXTMOD)
> -src := $(if $(VPATH),$(VPATH)/)$(obj)
> +obj := .
> +src := $(srcroot)
>
>   # Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS
>   include $(kbuild-file)
>
> -output-symdump := $(KBUILD_EXTMOD)/Module.symvers
> +output-symdump := Module.symvers
>
>   ifeq ($(wildcard $(objtree)/Module.symvers),)
>   missing-input := $(objtree)/Module.symvers
> diff --git a/scripts/coccicheck b/scripts/coccicheck
> index e52cb43fede6..0e6bc5a10320 100755
> --- a/scripts/coccicheck
> +++ b/scripts/coccicheck
> @@ -80,11 +80,7 @@ command results in a shift count error.'
>       NPROC=1
>   else
>       ONLINE=0
> -    if [ "$KBUILD_EXTMOD" = "" ] ; then
> -        OPTIONS="--dir $srctree $COCCIINCLUDE"
> -    else
> -        OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
> -    fi
> +    OPTIONS="--dir $srcroot $COCCIINCLUDE"
>
>       # Use only one thread per core by default if hyperthreading is enabled
>       THREADS_PER_CORE=$(LANG=C lscpu | grep "Thread(s) per core: " | tr -cd "[:digit:]")
> diff --git a/scripts/nsdeps b/scripts/nsdeps
> index f1718cc0d700..8ca12e2b5c03 100644
> --- a/scripts/nsdeps
> +++ b/scripts/nsdeps
> @@ -19,12 +19,6 @@ if ! { echo "$SPATCH_REQ_VERSION"; echo "$SPATCH_VERSION"; } | sort -CV ; then
>   	exit 1
>   fi
>
> -if [ "$KBUILD_EXTMOD" ]; then
> -	src_prefix=
> -else
> -	src_prefix=$srctree/
> -fi
> -
>   generate_deps_for_ns() {
>   	$SPATCH --very-quiet --in-place --sp-file \
>   		$srctree/scripts/coccinelle/misc/add_namespace.cocci -D nsdeps -D ns=$1 $2
> @@ -34,7 +28,7 @@ generate_deps() {
>   	local mod=${1%.ko:}
>   	shift
>   	local namespaces="$*"
> -	local mod_source_files=$(sed "s|^\(.*\)\.o$|${src_prefix}\1.c|" $mod.mod)
> +	local mod_source_files=$(sed "s|^\(.*\)\.o$|${srcroot}/\1.c|" $mod.mod)
>
>   	for ns in $namespaces; do
>   		echo "Adding namespace $ns to module $mod.ko."
> diff --git a/scripts/package/install-extmod-build b/scripts/package/install-extmod-build
> index 7ec1f061a519..64d958ee45f3 100755
> --- a/scripts/package/install-extmod-build
> +++ b/scripts/package/install-extmod-build
> @@ -51,6 +51,13 @@ mkdir -p "${destdir}"
>   if [ "${CC}" != "${HOSTCC}" ]; then
>   	echo "Rebuilding host programs with ${CC}..."
>
> +	# This leverages external module building.
> +	# - Clear sub_make_done to allow the top-level Makefile to redo sub-make.
> +	# - Filter out --no-print-directory to print "Entering directory" logs
> +	#   when Make changes the working directory.
> +	unset sub_make_done
> +	MAKEFLAGS=$(echo "${MAKEFLAGS}" | sed s/--no-print-directory//)
> +
>   	cat <<-'EOF' >  "${destdir}/Kbuild"
>   	subdir-y := scripts
>   	EOF


^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v2 06/11] kbuild: remove extmod_prefix, MODORDER, MODULES_NSDEPS variables
  2024-11-10  1:34 [PATCH v2 00/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
                   ` (4 preceding siblings ...)
  2024-11-10  1:34 ` [PATCH v2 05/11] kbuild: change working directory to external module directory with M= Masahiro Yamada
@ 2024-11-10  1:34 ` Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 07/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
                   ` (4 subsequent siblings)
  10 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-10  1:34 UTC (permalink / raw)
  To: linux-kbuild
  Cc: linux-kernel, rust-for-linux, cocci, Masahiro Yamada,
	Nicolas Schier

With the previous changes, $(extmod_prefix), $(MODORDER), and
$(MODULES_NSDEPS) are constant. (empty, modules.order, and
modules.nsdeps, respectively).

Remove these variables and hard-code their values.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
---

Changes in v2:
 - More cleanups

 Makefile                  | 22 +++++++++-------------
 scripts/Makefile.modfinal |  8 ++++----
 scripts/Makefile.modinst  |  6 +++---
 scripts/Makefile.modpost  |  6 +++---
 scripts/nsdeps            |  2 +-
 5 files changed, 20 insertions(+), 24 deletions(-)

diff --git a/Makefile b/Makefile
index e5f7ac7647a7..c7eeb10455b6 100644
--- a/Makefile
+++ b/Makefile
@@ -1122,10 +1122,6 @@ export MODLIB
 
 PHONY += prepare0
 
-export extmod_prefix =
-export MODORDER := $(extmod_prefix)modules.order
-export MODULES_NSDEPS := $(extmod_prefix)modules.nsdeps
-
 ifeq ($(KBUILD_EXTMOD),)
 
 build-dir	:= .
@@ -1876,7 +1872,7 @@ endif
 
 ifdef CONFIG_MODULES
 
-$(MODORDER): $(build-dir)
+modules.order: $(build-dir)
 	@:
 
 # KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
@@ -1887,7 +1883,7 @@ ifneq ($(KBUILD_MODPOST_NOFINAL),1)
 endif
 
 PHONY += modules_check
-modules_check: $(MODORDER)
+modules_check: modules.order
 	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/modules-check.sh $<
 
 else # CONFIG_MODULES
@@ -1928,15 +1924,15 @@ $(single-ko): single_modules
 $(single-no-ko): $(build-dir)
 	@:
 
-# Remove MODORDER when done because it is not the real one.
+# Remove modules.order when done because it is not the real one.
 PHONY += single_modules
 single_modules: $(single-no-ko) modules_prepare
-	$(Q){ $(foreach m, $(single-ko), echo $(extmod_prefix)$(m:%.ko=%.o);) } > $(MODORDER)
+	$(Q){ $(foreach m, $(single-ko), echo $(m:%.ko=%.o);) } > modules.order
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
 ifneq ($(KBUILD_MODPOST_NOFINAL),1)
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modfinal
 endif
-	$(Q)rm -f $(MODORDER)
+	$(Q)rm -f modules.order
 
 single-goals := $(addprefix $(build-dir)/, $(single-no-ko))
 
@@ -2013,12 +2009,12 @@ nsdeps: modules
 quiet_cmd_gen_compile_commands = GEN     $@
       cmd_gen_compile_commands = $(PYTHON3) $< -a $(AR) -o $@ $(filter-out $<, $(real-prereqs))
 
-$(extmod_prefix)compile_commands.json: $(srctree)/scripts/clang-tools/gen_compile_commands.py \
+compile_commands.json: $(srctree)/scripts/clang-tools/gen_compile_commands.py \
 	$(if $(KBUILD_EXTMOD),, vmlinux.a $(KBUILD_VMLINUX_LIBS)) \
-	$(if $(CONFIG_MODULES), $(MODORDER)) FORCE
+	$(if $(CONFIG_MODULES), modules.order) FORCE
 	$(call if_changed,gen_compile_commands)
 
-targets += $(extmod_prefix)compile_commands.json
+targets += compile_commands.json
 
 PHONY += clang-tidy clang-analyzer
 
@@ -2026,7 +2022,7 @@ ifdef CONFIG_CC_IS_CLANG
 quiet_cmd_clang_tools = CHECK   $<
       cmd_clang_tools = $(PYTHON3) $(srctree)/scripts/clang-tools/run-clang-tools.py $@ $<
 
-clang-tidy clang-analyzer: $(extmod_prefix)compile_commands.json
+clang-tidy clang-analyzer: compile_commands.json
 	$(call cmd,clang_tools)
 else
 clang-tidy clang-analyzer:
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index 6d8aa3059ee2..bab53884f7e3 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -13,7 +13,7 @@ include $(srctree)/scripts/Kbuild.include
 include $(srctree)/scripts/Makefile.lib
 
 # find all modules listed in modules.order
-modules := $(call read-file, $(MODORDER))
+modules := $(call read-file, modules.order)
 
 __modfinal: $(modules:%.o=%.ko)
 	@:
@@ -30,7 +30,7 @@ quiet_cmd_cc_o_c = CC [M]  $@
 %.mod.o: %.mod.c FORCE
 	$(call if_changed_dep,cc_o_c)
 
-$(extmod_prefix).module-common.o: $(srctree)/scripts/module-common.c FORCE
+.module-common.o: $(srctree)/scripts/module-common.c FORCE
 	$(call if_changed_dep,cc_o_c)
 
 quiet_cmd_ld_ko_o = LD [M]  $@
@@ -57,13 +57,13 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check),      \
 	printf '%s\n' 'savedcmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
 
 # Re-generate module BTFs if either module's .ko or vmlinux changed
-%.ko: %.o %.mod.o $(extmod_prefix).module-common.o $(objtree)/scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),$(objtree)/vmlinux) FORCE
+%.ko: %.o %.mod.o .module-common.o $(objtree)/scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),$(objtree)/vmlinux) FORCE
 	+$(call if_changed_except,ld_ko_o,$(objtree)/vmlinux)
 ifdef CONFIG_DEBUG_INFO_BTF_MODULES
 	+$(if $(newer-prereqs),$(call cmd,btf_ko))
 endif
 
-targets += $(modules:%.o=%.ko) $(modules:%.o=%.mod.o) $(extmod_prefix).module-common.o
+targets += $(modules:%.o=%.ko) $(modules:%.o=%.mod.o) .module-common.o
 
 # Add FORCE to the prerequisites of a target to force it to be always rebuilt.
 # ---------------------------------------------------------------------------
diff --git a/scripts/Makefile.modinst b/scripts/Makefile.modinst
index 6fa9af4a25b4..f97c9926ed31 100644
--- a/scripts/Makefile.modinst
+++ b/scripts/Makefile.modinst
@@ -40,7 +40,7 @@ $(addprefix $(MODLIB)/, modules.builtin modules.builtin.modinfo modules.builtin.
 
 endif
 
-modules := $(call read-file, $(MODORDER))
+modules := $(call read-file, modules.order)
 
 ifeq ($(KBUILD_EXTMOD),)
 dst := $(MODLIB)/kernel
@@ -59,7 +59,7 @@ suffix-$(CONFIG_MODULE_COMPRESS_XZ)	:= .xz
 suffix-$(CONFIG_MODULE_COMPRESS_ZSTD)	:= .zst
 endif
 
-modules := $(patsubst $(extmod_prefix)%.o, $(dst)/%.ko$(suffix-y), $(modules))
+modules := $(patsubst %.o, $(dst)/%.ko$(suffix-y), $(modules))
 install-$(CONFIG_MODULES) += $(modules)
 
 __modinst: $(install-y)
@@ -119,7 +119,7 @@ endif
 # Create necessary directories
 $(foreach dir, $(sort $(dir $(install-y))), $(shell mkdir -p $(dir)))
 
-$(dst)/%.ko: $(extmod_prefix)%.ko FORCE
+$(dst)/%.ko: %.ko FORCE
 	$(call cmd,install)
 	$(call cmd,strip)
 	$(call cmd,sign)
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 78d2ca4f25f5..ab0e94ea6249 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -46,7 +46,7 @@ modpost-args =										\
 	$(if $(CONFIG_MODULE_SRCVERSION_ALL),-a)					\
 	$(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E)					\
 	$(if $(KBUILD_MODPOST_WARN),-w)							\
-	$(if $(KBUILD_NSDEPS),-d $(MODULES_NSDEPS))					\
+	$(if $(KBUILD_NSDEPS),-d modules.nsdeps)					\
 	$(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS)$(KBUILD_NSDEPS),-N)	\
 	$(if $(findstring 1, $(KBUILD_EXTRA_WARN)),-W)					\
 	-o $@
@@ -61,8 +61,8 @@ endif
 # Read out modules.order to pass in modpost.
 # Otherwise, allmodconfig would fail with "Argument list too long".
 ifdef KBUILD_MODULES
-modpost-args += -T $(MODORDER)
-modpost-deps += $(MODORDER)
+modpost-args += -T modules.order
+modpost-deps += modules.order
 endif
 
 ifeq ($(KBUILD_EXTMOD),)
diff --git a/scripts/nsdeps b/scripts/nsdeps
index 8ca12e2b5c03..bab4ec870e50 100644
--- a/scripts/nsdeps
+++ b/scripts/nsdeps
@@ -51,4 +51,4 @@ generate_deps() {
 while read line
 do
 	generate_deps $line
-done < $MODULES_NSDEPS
+done < modules.nsdeps
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 33+ messages in thread

* [PATCH v2 07/11] kbuild: support building external modules in a separate build directory
  2024-11-10  1:34 [PATCH v2 00/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
                   ` (5 preceding siblings ...)
  2024-11-10  1:34 ` [PATCH v2 06/11] kbuild: remove extmod_prefix, MODORDER, MODULES_NSDEPS variables Masahiro Yamada
@ 2024-11-10  1:34 ` Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 08/11] kbuild: support -fmacro-prefix-map for external modules Masahiro Yamada
                   ` (3 subsequent siblings)
  10 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-10  1:34 UTC (permalink / raw)
  To: linux-kbuild
  Cc: linux-kernel, rust-for-linux, cocci, Masahiro Yamada,
	Nicolas Schier

There has been a long-standing request to support building external
modules in a separate build directory.

This commit introduces a new environment variable, KBUILD_EXTMOD_OUTPUT,
and its shorthand Make variable, MO.

A simple usage:

 $ make -C <kernel-dir> M=<module-src-dir> MO=<module-build-dir>

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
---

Changes in v2:
  - Add -I $(src) -I $(obj) for external modules as well
  - Fix a typo 'Speficies' to 'Specifies'.

 Documentation/kbuild/kbuild.rst  |  8 +++++++-
 Documentation/kbuild/modules.rst |  8 +++++++-
 Makefile                         | 22 +++++++++++++++++++---
 scripts/Makefile.host            |  8 +++-----
 scripts/Makefile.lib             |  2 --
 5 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst
index 1796b3eba37b..17c9f920f03d 100644
--- a/Documentation/kbuild/kbuild.rst
+++ b/Documentation/kbuild/kbuild.rst
@@ -137,12 +137,18 @@ Specify the output directory when building the kernel.
 This variable can also be used to point to the kernel output directory when
 building external modules against a pre-built kernel in a separate build
 directory. Please note that this does NOT specify the output directory for the
-external modules themselves.
+external modules themselves. (Use KBUILD_EXTMOD_OUTPUT for that purpose.)
 
 The output directory can also be specified using "O=...".
 
 Setting "O=..." takes precedence over KBUILD_OUTPUT.
 
+KBUILD_EXTMOD_OUTPUT
+--------------------
+Specify the output directory for external modules.
+
+Setting "MO=..." takes precedence over KBUILD_EXTMOD_OUTPUT.
+
 KBUILD_EXTRA_WARN
 -----------------
 Specify the extra build checks. The same value can be assigned by passing
diff --git a/Documentation/kbuild/modules.rst b/Documentation/kbuild/modules.rst
index cd5a54d91e6d..a01f3754c7fc 100644
--- a/Documentation/kbuild/modules.rst
+++ b/Documentation/kbuild/modules.rst
@@ -66,7 +66,10 @@ Options
 	of the kernel output directory if the kernel was built in a separate
 	build directory.)
 
-	make -C $KDIR M=$PWD
+	You can optionally pass MO= option if you want to build the modules in
+	a separate directory.
+
+	make -C $KDIR M=$PWD [MO=$BUILD_DIR]
 
 	-C $KDIR
 		The directory that contains the kernel and relevant build
@@ -80,6 +83,9 @@ Options
 		directory where the external module (kbuild file) is
 		located.
 
+	MO=$BUILD_DIR
+		Specifies a separate output directory for the external module.
+
 Targets
 -------
 
diff --git a/Makefile b/Makefile
index c7eeb10455b6..38ce19747728 100644
--- a/Makefile
+++ b/Makefile
@@ -134,6 +134,10 @@ ifeq ("$(origin M)", "command line")
   KBUILD_EXTMOD := $(M)
 endif
 
+ifeq ("$(origin MO)", "command line")
+  KBUILD_EXTMOD_OUTPUT := $(MO)
+endif
+
 $(if $(word 2, $(KBUILD_EXTMOD)), \
 	$(error building multiple external modules is not supported))
 
@@ -187,7 +191,7 @@ ifdef KBUILD_EXTMOD
     else
         objtree := $(CURDIR)
     endif
-    output := $(KBUILD_EXTMOD)
+    output := $(or $(KBUILD_EXTMOD_OUTPUT),$(KBUILD_EXTMOD))
     # KBUILD_EXTMOD might be a relative path. Remember its absolute path before
     # Make changes the working directory.
     srcroot := $(realpath $(KBUILD_EXTMOD))
@@ -555,7 +559,7 @@ USERINCLUDE    := \
 LINUXINCLUDE    := \
 		-I$(srctree)/arch/$(SRCARCH)/include \
 		-I$(objtree)/arch/$(SRCARCH)/include/generated \
-		$(if $(building_out_of_srctree),-I$(srctree)/include) \
+		-I$(srctree)/include \
 		-I$(objtree)/include \
 		$(USERINCLUDE)
 
@@ -645,6 +649,7 @@ quiet_cmd_makefile = GEN     Makefile
 	} > Makefile
 
 outputmakefile:
+ifeq ($(KBUILD_EXTMOD),)
 	@if [ -f $(srctree)/.config -o \
 		 -d $(srctree)/include/config -o \
 		 -d $(srctree)/arch/$(SRCARCH)/include/generated ]; then \
@@ -654,7 +659,16 @@ outputmakefile:
 		echo >&2 "***"; \
 		false; \
 	fi
-	$(Q)ln -fsn $(srctree) source
+else
+	@if [ -f $(srcroot)/modules.order ]; then \
+		echo >&2 "***"; \
+		echo >&2 "*** The external module source tree is not clean."; \
+		echo >&2 "*** Please run 'make -C $(abs_srctree) M=$(realpath $(srcroot)) clean'"; \
+		echo >&2 "***"; \
+		false; \
+	fi
+endif
+	$(Q)ln -fsn $(srcroot) source
 	$(call cmd,makefile)
 	$(Q)test -e .gitignore || \
 	{ echo "# this is build directory, ignore it"; echo "*"; } > .gitignore
@@ -1940,6 +1954,8 @@ KBUILD_MODULES := 1
 
 endif
 
+prepare: outputmakefile
+
 # Preset locale variables to speed up the build process. Limit locale
 # tweaks to this spot to avoid wrong language settings when running
 # make menuconfig etc.
diff --git a/scripts/Makefile.host b/scripts/Makefile.host
index e01c13a588dd..c1dedf646a39 100644
--- a/scripts/Makefile.host
+++ b/scripts/Makefile.host
@@ -96,12 +96,10 @@ hostrust_flags = --out-dir $(dir $@) --emit=dep-info=$(depfile) \
                  $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
                  $(HOSTRUSTFLAGS_$(target-stem))
 
-# $(objtree)/$(obj) for including generated headers from checkin source files
-ifeq ($(KBUILD_EXTMOD),)
+# $(obj) for including generated headers from checkin source files
 ifdef building_out_of_srctree
-hostc_flags   += -I $(objtree)/$(obj)
-hostcxx_flags += -I $(objtree)/$(obj)
-endif
+hostc_flags   += -I $(obj)
+hostcxx_flags += -I $(obj)
 endif
 
 #####
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index e7859ad90224..5660dfc9ed36 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -213,13 +213,11 @@ endif
 
 # $(src) for including checkin headers from generated source files
 # $(obj) for including generated headers from checkin source files
-ifeq ($(KBUILD_EXTMOD),)
 ifdef building_out_of_srctree
 _c_flags   += $(addprefix -I, $(src) $(obj))
 _a_flags   += $(addprefix -I, $(src) $(obj))
 _cpp_flags += $(addprefix -I, $(src) $(obj))
 endif
-endif
 
 # If $(is-kernel-object) is 'y', this object will be linked to vmlinux or modules
 is-kernel-object = $(or $(part-of-builtin),$(part-of-module))
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 33+ messages in thread

* [PATCH v2 08/11] kbuild: support -fmacro-prefix-map for external modules
  2024-11-10  1:34 [PATCH v2 00/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
                   ` (6 preceding siblings ...)
  2024-11-10  1:34 ` [PATCH v2 07/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
@ 2024-11-10  1:34 ` Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 09/11] kbuild: use absolute path in the generated wrapper Makefile Masahiro Yamada
                   ` (2 subsequent siblings)
  10 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-10  1:34 UTC (permalink / raw)
  To: linux-kbuild
  Cc: linux-kernel, rust-for-linux, cocci, Masahiro Yamada,
	Nicolas Schier

This commit makes -fmacro-prefix-map work for external modules built in
a separate output directory. It improves the reproducibility of external
modules and provides the benefits described in commit a73619a845d5
("kbuild: use -fmacro-prefix-map to make __FILE__ a relative path").

When building_out_of_srctree is not defined (e.g., when the kernel or
external module is built in the source directory), this option is
unnecessary.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
---

Changes in v2:
  - Check building_out_of_srctree instead of VPATH

 Makefile | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 38ce19747728..5488aa96b46b 100644
--- a/Makefile
+++ b/Makefile
@@ -1041,8 +1041,10 @@ ifdef CONFIG_CC_IS_GCC
 KBUILD_CFLAGS   += -fconserve-stack
 endif
 
-# change __FILE__ to the relative path from the srctree
-KBUILD_CPPFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
+# change __FILE__ to the relative path to the source directory
+ifdef building_out_of_srctree
+KBUILD_CPPFLAGS += $(call cc-option,-fmacro-prefix-map=$(srcroot)/=)
+endif
 
 # include additional Makefiles when needed
 include-y			:= scripts/Makefile.extrawarn
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 33+ messages in thread

* [PATCH v2 09/11] kbuild: use absolute path in the generated wrapper Makefile
  2024-11-10  1:34 [PATCH v2 00/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
                   ` (7 preceding siblings ...)
  2024-11-10  1:34 ` [PATCH v2 08/11] kbuild: support -fmacro-prefix-map for external modules Masahiro Yamada
@ 2024-11-10  1:34 ` Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 10/11] kbuild: make wrapper Makefile more convenient for external modules Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 11/11] kbuild: allow to start building external modules in any directory Masahiro Yamada
  10 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-10  1:34 UTC (permalink / raw)
  To: linux-kbuild
  Cc: linux-kernel, rust-for-linux, cocci, Masahiro Yamada,
	Nicolas Schier

Keep the consistent behavior when this Makefile is invoked from another
directory.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
---

(no changes since v1)

 Makefile | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 5488aa96b46b..35e34cce4942 100644
--- a/Makefile
+++ b/Makefile
@@ -644,8 +644,9 @@ ifdef building_out_of_srctree
 
 quiet_cmd_makefile = GEN     Makefile
       cmd_makefile = { \
-	echo "\# Automatically generated by $(srctree)/Makefile: don't edit"; \
-	echo "include $(srctree)/Makefile"; \
+	echo "\# Automatically generated by $(abs_srctree)/Makefile: don't edit"; \
+	echo "export KBUILD_OUTPUT = $(CURDIR)"; \
+	echo "include $(abs_srctree)/Makefile"; \
 	} > Makefile
 
 outputmakefile:
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 33+ messages in thread

* [PATCH v2 10/11] kbuild: make wrapper Makefile more convenient for external modules
  2024-11-10  1:34 [PATCH v2 00/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
                   ` (8 preceding siblings ...)
  2024-11-10  1:34 ` [PATCH v2 09/11] kbuild: use absolute path in the generated wrapper Makefile Masahiro Yamada
@ 2024-11-10  1:34 ` Masahiro Yamada
  2024-11-10  1:34 ` [PATCH v2 11/11] kbuild: allow to start building external modules in any directory Masahiro Yamada
  10 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-10  1:34 UTC (permalink / raw)
  To: linux-kbuild
  Cc: linux-kernel, rust-for-linux, cocci, Masahiro Yamada,
	Nicolas Schier

When Kbuild starts building in a separate output directory, it generates
a wrapper Makefile, allowing you to invoke 'make' from the output
directory.

This commit makes it more convenient, so you can invoke 'make' without
M= or MO=.

First, you need to build external modules in a separate directory:

  $ make M=/path/to/module/source/dir MO=/path/to/module/build/dir

Once the wrapper Makefile is generated in /path/to/module/build/dir,
you can proceed as follows:

  $ cd /path/to/module/build/dir
  $ make

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
---

Changes in v2:
 - use $(srcroot) instead of $(_vpath)

 Makefile | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 35e34cce4942..df002595341a 100644
--- a/Makefile
+++ b/Makefile
@@ -642,10 +642,20 @@ ifdef building_out_of_srctree
 # At the same time when output Makefile generated, generate .gitignore to
 # ignore whole output directory
 
+ifdef KBUILD_EXTMOD
+print_env_for_makefile = \
+	echo "export KBUILD_OUTPUT = $(objtree)"; \
+	echo "export KBUILD_EXTMOD = $(realpath $(srcroot))" ; \
+	echo "export KBUILD_EXTMOD_OUTPUT = $(CURDIR)"
+else
+print_env_for_makefile = \
+	echo "export KBUILD_OUTPUT = $(CURDIR)"
+endif
+
 quiet_cmd_makefile = GEN     Makefile
       cmd_makefile = { \
 	echo "\# Automatically generated by $(abs_srctree)/Makefile: don't edit"; \
-	echo "export KBUILD_OUTPUT = $(CURDIR)"; \
+	$(print_env_for_makefile); \
 	echo "include $(abs_srctree)/Makefile"; \
 	} > Makefile
 
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 33+ messages in thread

* [PATCH v2 11/11] kbuild: allow to start building external modules in any directory
  2024-11-10  1:34 [PATCH v2 00/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
                   ` (9 preceding siblings ...)
  2024-11-10  1:34 ` [PATCH v2 10/11] kbuild: make wrapper Makefile more convenient for external modules Masahiro Yamada
@ 2024-11-10  1:34 ` Masahiro Yamada
  10 siblings, 0 replies; 33+ messages in thread
From: Masahiro Yamada @ 2024-11-10  1:34 UTC (permalink / raw)
  To: linux-kbuild
  Cc: linux-kernel, rust-for-linux, cocci, Masahiro Yamada,
	Nicolas Schier

Unless an explicit O= option is provided, external module builds must
start from the kernel directory.

This can be achieved by using the -C option:

  $ make -C /path/to/kernel M=/path/to/external/module

This commit allows starting external module builds from any directory,
so you can also do the following:

  $ make -f /path/to/kernel/Makefile M=/path/to/external/module

The key difference is that the -C option changes the working directory
and parses the Makefile located there, while the -f option only
specifies the Makefile to use.

As shown in the examples in Documentation/kbuild/modules.rst, external
modules usually have a wrapper Makefile that allows you to build them
without specifying any make arguments. The Makefile typically contains
a rule as follows:

    KDIR ?= /path/to/kernel
    default:
            $(MAKE) -C $(KDIR) M=$(CURDIR) $(MAKECMDGOALS)

The log will appear as follows:

    $ make
    make -C /path/to/kernel M=/path/to/external/module
    make[1]: Entering directory '/path/to/kernel'
    make[2]: Entering directory '/path/to/external/module'
      CC [M]  helloworld.o
      MODPOST Module.symvers
      CC [M]  helloworld.mod.o
      CC [M]  .module-common.o
      LD [M]  helloworld.ko
    make[2]: Leaving directory '/path/to/external/module'
    make[1]: Leaving directory '/path/to/kernel'

This changes the working directory twice because the -C option first
switches to the kernel directory, and then Kbuild internally recurses
back to the external module directory.

With this commit, the wrapper Makefile can directly include the kernel
Makefile:

    KDIR ?= /path/to/kernel
    export KBUILD_EXTMOD := $(realpath $(dir $(lastword $(MAKEFILE_LIST))))
    include $(KDIR)/Makefile

This avoids unnecessary sub-make invocations:

    $ make
      CC [M]  helloworld.o
      MODPOST Module.symvers
      CC [M]  helloworld.mod.o
      CC [M]  .module-common.o
      LD [M]  helloworld.ko

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
---

Changes in v2:
  - Fix typos in the commit description (s/exernal/external/)
  - Fix `uname -r` to $(shell uname -r) in Example 3

 Documentation/kbuild/modules.rst | 21 +++++++++++++++++++++
 Makefile                         |  8 ++++++--
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/Documentation/kbuild/modules.rst b/Documentation/kbuild/modules.rst
index a01f3754c7fc..101de236cd0c 100644
--- a/Documentation/kbuild/modules.rst
+++ b/Documentation/kbuild/modules.rst
@@ -59,6 +59,12 @@ Command Syntax
 
 		$ make -C /lib/modules/`uname -r`/build M=$PWD modules_install
 
+	Starting from Linux 6.13, you can use the -f option instead of -C. This
+	will avoid unnecessary change of the working directory. The external
+	module will be output to the directory where you invoke make.
+
+		$ make -f /lib/modules/`uname -r`/build/Makefile M=$PWD
+
 Options
 -------
 
@@ -221,6 +227,21 @@ Separate Kbuild File and Makefile
 	consisting of several hundred lines, and here it really pays
 	off to separate the kbuild part from the rest.
 
+	Linux 6.13 and later support another way. The external module Makefile
+	can include the kernel Makefile directly, rather than invoking sub Make.
+
+	Example 3::
+
+		--> filename: Kbuild
+		obj-m  := 8123.o
+		8123-y := 8123_if.o 8123_pci.o
+
+		--> filename: Makefile
+		KDIR ?= /lib/modules/$(shell uname -r)/build
+		export KBUILD_EXTMOD := $(realpath $(dir $(lastword $(MAKEFILE_LIST))))
+		include $(KDIR)/Makefile
+
+
 Building Multiple Modules
 -------------------------
 
diff --git a/Makefile b/Makefile
index df002595341a..0825a9a58ca9 100644
--- a/Makefile
+++ b/Makefile
@@ -189,9 +189,13 @@ ifdef KBUILD_EXTMOD
         objtree := $(realpath $(KBUILD_OUTPUT))
         $(if $(objtree),,$(error specified kernel directory "$(KBUILD_OUTPUT)" does not exist))
     else
-        objtree := $(CURDIR)
+        objtree := $(abs_srctree)
     endif
-    output := $(or $(KBUILD_EXTMOD_OUTPUT),$(KBUILD_EXTMOD))
+    # If Make is invoked from the kernel directory (either kernel
+    # source directory or kernel build directory), external modules
+    # are built in $(KBUILD_EXTMOD) for backward compatibility,
+    # otherwise, built in the current directory.
+    output := $(or $(KBUILD_EXTMOD_OUTPUT),$(if $(filter $(CURDIR),$(objtree) $(abs_srctree)),$(KBUILD_EXTMOD)))
     # KBUILD_EXTMOD might be a relative path. Remember its absolute path before
     # Make changes the working directory.
     srcroot := $(realpath $(KBUILD_EXTMOD))
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 33+ messages in thread

end of thread, other threads:[~2025-01-27 23:08 UTC | newest]

Thread overview: 33+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2024-11-10  1:34 [PATCH v2 00/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
2024-11-10  1:34 ` [PATCH v2 01/11] kbuild: replace two $(abs_objtree) with $(CURDIR) in top Makefile Masahiro Yamada
2024-11-10  1:34 ` [PATCH v2 02/11] kbuild: add $(objtree)/ prefix to some in-kernel build artifacts Masahiro Yamada
2024-11-10  1:34 ` [PATCH v2 03/11] kbuild: rename abs_objtree to abs_output Masahiro Yamada
2024-11-10  1:34 ` [PATCH v2 04/11] kbuild: use 'output' variable to create the output directory Masahiro Yamada
2024-11-10  1:34 ` [PATCH v2 05/11] kbuild: change working directory to external module directory with M= Masahiro Yamada
2024-11-18 14:47   ` Nicolas Schier
2024-11-18 17:02     ` Masahiro Yamada
2024-11-27 15:29       ` Nicolas Schier
2024-11-27 23:15         ` Masahiro Yamada
2024-12-04 20:51   ` Alison Schofield
2024-12-05  2:33     ` Masahiro Yamada
2024-12-04 23:35   ` Charlie Jenkins
2024-12-05  2:48     ` Masahiro Yamada
2024-12-05  6:27       ` Charlie Jenkins
2024-12-09 13:46   ` Thorsten Blum
2024-12-09 13:55     ` Thorsten Blum
2024-12-10 10:47       ` Masahiro Yamada
2024-12-10 11:06         ` Thorsten Blum
2024-12-11  2:36           ` Masahiro Yamada
2024-12-10 15:34   ` Jon Hunter
2024-12-11  2:39     ` Masahiro Yamada
2024-12-11 12:21       ` Jon Hunter
2024-12-12  2:08         ` Masahiro Yamada
2024-12-12  6:00           ` Jon Hunter
2024-12-12 15:49             ` Masahiro Yamada
2025-01-27 23:08   ` Qu Wenruo
2024-11-10  1:34 ` [PATCH v2 06/11] kbuild: remove extmod_prefix, MODORDER, MODULES_NSDEPS variables Masahiro Yamada
2024-11-10  1:34 ` [PATCH v2 07/11] kbuild: support building external modules in a separate build directory Masahiro Yamada
2024-11-10  1:34 ` [PATCH v2 08/11] kbuild: support -fmacro-prefix-map for external modules Masahiro Yamada
2024-11-10  1:34 ` [PATCH v2 09/11] kbuild: use absolute path in the generated wrapper Makefile Masahiro Yamada
2024-11-10  1:34 ` [PATCH v2 10/11] kbuild: make wrapper Makefile more convenient for external modules Masahiro Yamada
2024-11-10  1:34 ` [PATCH v2 11/11] kbuild: allow to start building external modules in any directory Masahiro Yamada

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