[PATCH v2 1/8] kbuild: fix and refactor single target build

Masahiro Yamada
2022-09-06T06:14:14Z

The single target build has a subtle bug for the combination for
an individual file and a subdirectory.

[1] 'make kernel/fork.i' builds only kernel/fork.i

$ make kernel/fork.i
CALL scripts/checksyscalls.sh
DESCEND objtool
CPP kernel/fork.i

[2] 'make kernel/' builds only under the kernel/ directory.

$ make kernel/
CALL scripts/checksyscalls.sh
DESCEND objtool
CC kernel/fork.o
CC kernel/exec_domain.o
[snip]
CC kernel/rseq.o
AR kernel/built-in.a

But, if you try to do [1] and [2] in a single command, you will get
only [1] with a weird log:

$ make kernel/fork.i kernel/
CALL scripts/checksyscalls.sh
DESCEND objtool
CPP kernel/fork.i
make[2]: Nothing to be done for 'kernel/'.

With 'make kernel/fork.i kernel/', you should get both [1] and [2].

Rewrite the single target build.

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

Changes in v2:
- New

Makefile | 9 ++++---
scripts/Makefile.build | 54 +++++++++++++-----------------------------
2 files changed, 20 insertions(+), 43 deletions(-)

diff --git a/Makefile b/Makefile
index 0af9dd405fb1..373cd2f0f49e 100644
--- a/Makefile
+++ b/Makefile
@@ -1824,11 +1824,11 @@ single_modpost: $(single-no-ko) modules_prepare
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
$(Q)rm -f $(MODORDER)

-export KBUILD_SINGLE_TARGETS := $(addprefix $(extmod_prefix), $(single-no-ko))
+single-goals := $(addprefix $(extmod_prefix), $(single-no-ko))

# trim unrelated directories
build-dirs := $(foreach d, $(build-dirs), \
- $(if $(filter $(d)/%, $(KBUILD_SINGLE_TARGETS)), $(d)))
+ $(if $(filter $d/%, $(single-goals)), $d))

endif

@@ -1840,9 +1840,8 @@ endif
PHONY += descend $(build-dirs)
descend: $(build-dirs)
$(build-dirs): prepare
- $(Q)$(MAKE) $(build)=$@ \
- single-build=$(if $(filter-out $@/, $(filter $@/%, $(KBUILD_SINGLE_TARGETS))),1) \
- need-builtin=1 need-modorder=1
+ $(Q)$(MAKE) $(build)=$@ need-builtin=1 need-modorder=1 \
+ $(filter $@/%, $(single-goals))

clean-dirs := $(addprefix _clean_, $(clean-dirs))
PHONY += $(clean-dirs) clean
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 0df488d0bbb0..91d2e5461a3e 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -5,8 +5,8 @@

src := $(obj)

-PHONY := __build
-__build:
+PHONY := $(obj)/
+$(obj)/:

# Init all relevant variables used in kbuild files so
# 1) they have correct type
@@ -323,7 +323,7 @@ $(obj)/%.o: $(src)/%.S FORCE

targets += $(filter-out $(subdir-builtin), $(real-obj-y))
targets += $(filter-out $(subdir-modorder), $(real-obj-m))
-targets += $(real-dtb-y) $(lib-y) $(always-y) $(MAKECMDGOALS)
+targets += $(real-dtb-y) $(lib-y) $(always-y)

# Linker scripts preprocessor (.lds.S -> .lds)
# ---------------------------------------------------------------------------
@@ -400,8 +400,6 @@ $(multi-obj-m): %.o: %.mod FORCE
$(call if_changed_rule,ld_multi_m)
$(call multi_depend, $(multi-obj-m), .o, -objs -y -m)

-targets := $(filter-out $(PHONY), $(targets))
-
# Add intermediate targets:
# When building objects with specific suffix patterns, add intermediate
# targets that the final targets are derived from.
@@ -420,52 +418,29 @@ targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
# Build
# ---------------------------------------------------------------------------

-ifdef single-build
-
-KBUILD_SINGLE_TARGETS := $(filter $(obj)/%, $(KBUILD_SINGLE_TARGETS))
-
-curdir-single := $(sort $(foreach x, $(KBUILD_SINGLE_TARGETS), \
- $(if $(filter $(x) $(basename $(x)).o, $(targets)), $(x))))
-
-# Handle single targets without any rule: show "Nothing to be done for ..." or
-# "No rule to make target ..." depending on whether the target exists.
-unknown-single := $(filter-out $(addsuffix /%, $(subdir-ym)), \
- $(filter-out $(curdir-single), $(KBUILD_SINGLE_TARGETS)))
-
-single-subdirs := $(foreach d, $(subdir-ym), \
- $(if $(filter $(d)/%, $(KBUILD_SINGLE_TARGETS)), $(d)))
-
-__build: $(curdir-single) $(single-subdirs)
-ifneq ($(unknown-single),)
- $(Q)$(MAKE) -f /dev/null $(unknown-single)
-endif
+$(obj)/: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
+ $(if $(KBUILD_MODULES), $(targets-for-modules)) \
+ $(subdir-ym) $(always-y)
@:

-ifeq ($(curdir-single),)
-# Nothing to do in this directory. Do not include any .*.cmd file for speed-up
-targets :=
-else
-targets += $(curdir-single)
-endif
+# Single targets
+# ---------------------------------------------------------------------------

-else
+single-subdirs := $(foreach d, $(subdir-ym), $(if $(filter $d/%, $(MAKECMDGOALS)), $d))
+single-subdir-goals := $(filter $(addsuffix /%, $(single-subdirs)), $(MAKECMDGOALS))

-__build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
- $(if $(KBUILD_MODULES), $(targets-for-modules)) \
- $(subdir-ym) $(always-y)
+$(single-subdir-goals): $(single-subdirs)
@:

-endif
-
# Descending
# ---------------------------------------------------------------------------

PHONY += $(subdir-ym)
$(subdir-ym):
$(Q)$(MAKE) $(build)=$@ \
- $(if $(filter $@/, $(KBUILD_SINGLE_TARGETS)),single-build=) \
need-builtin=$(if $(filter $@/built-in.a, $(subdir-builtin)),1) \
- need-modorder=$(if $(filter $@/modules.order, $(subdir-modorder)),1)
+ need-modorder=$(if $(filter $@/modules.order, $(subdir-modorder)),1) \
+ $(filter $@/%, $(single-subdir-goals))

# Add FORCE to the prequisites of a target to force it to be always rebuilt.
# ---------------------------------------------------------------------------
@@ -474,6 +449,9 @@ PHONY += FORCE

FORCE:

+targets += $(filter-out $(single-subdir-goals), $(MAKECMDGOALS))
+targets := $(filter-out $(PHONY), $(targets))
+
# Read all saved command lines and dependencies for the $(targets) we
# may be building above, using $(if_changed{,_dep}). As an
# optimization, we don't need to read them if the target does not
--
2.34.1