[PATCH 0/3] selftests/bpf: Fixes for out-of-tree builds

[PATCH 0/3] selftests/bpf: Fixes for out-of-tree builds

[Ricardo B. Marlière (SUSE)]

Hello,

When doing a simple out-of-tree build, e.g.:

$ git clean -fdx
$ mkdir ../build
$ make defconfig O=../build
$ scripts/kconfig/merge_config.sh -O ../build ../build/.config tools/testing/selftests/bpf/{config,config.x86_64}
$ make O=../build
$ make -C tools/testing/selftests install O=$PWD/../build SKIP_TARGETS= TARGETS=bpf

Will leave behind several build artifacts:

$ git clean -fdx
Removing tools/testing/selftests/bpf/libarena/asan.bpf.o
Removing tools/testing/selftests/bpf/libarena/asan_asan.bpf.o
Removing tools/testing/selftests/bpf/libarena/buddy.bpf.o
Removing tools/testing/selftests/bpf/libarena/buddy_asan.bpf.o
Removing tools/testing/selftests/bpf/libarena/common.bpf.o
Removing tools/testing/selftests/bpf/libarena/common_asan.bpf.o
Removing tools/testing/selftests/bpf/libarena/libarena.bpf.o
Removing tools/testing/selftests/bpf/libarena/libarena.skel.h
Removing tools/testing/selftests/bpf/libarena/libarena_asan.bpf.o
Removing tools/testing/selftests/bpf/libarena/libarena_asan.skel.h
Removing tools/testing/selftests/bpf/libarena/rbtree.bpf.o
Removing tools/testing/selftests/bpf/libarena/rbtree_asan.bpf.o
Removing tools/testing/selftests/bpf/libarena/spmc.bpf.o
Removing tools/testing/selftests/bpf/libarena/spmc_asan.bpf.o
Removing tools/testing/selftests/bpf/libarena/st_asan_buddy.bpf.o
Removing tools/testing/selftests/bpf/libarena/st_asan_buddy_asan.bpf.o
Removing tools/testing/selftests/bpf/libarena/st_buddy.bpf.o
Removing tools/testing/selftests/bpf/libarena/st_buddy_asan.bpf.o
Removing tools/testing/selftests/bpf/libarena/test_parallel_spmc.bpf.o
Removing tools/testing/selftests/bpf/libarena/test_parallel_spmc_asan.bpf.o
Removing tools/testing/selftests/bpf/libarena/test_rbtree.bpf.o
Removing tools/testing/selftests/bpf/libarena/test_rbtree_asan.bpf.o
Removing tools/testing/selftests/bpf/libarena/test_spmc.bpf.o
Removing tools/testing/selftests/bpf/libarena/test_spmc_asan.bpf.o
Removing tools/testing/selftests/bpf/map_tests/tests.h
Removing tools/testing/selftests/bpf/prog_tests/tests.h
Removing tools/testing/selftests/bpf/test_kmods/..module-common.o.cmd
Removing tools/testing/selftests/bpf/test_kmods/.Module.symvers.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_modorder_x.ko.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_modorder_x.mod.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_modorder_x.mod.o.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_modorder_x.o.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_modorder_y.ko.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_modorder_y.mod.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_modorder_y.mod.o.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_modorder_y.o.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_no_cfi.ko.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_no_cfi.mod.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_no_cfi.mod.o.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_no_cfi.o.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_rqspinlock.ko.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_rqspinlock.mod.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_rqspinlock.mod.o.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_test_rqspinlock.o.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_testmod.ko.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_testmod.mod.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_testmod.mod.o.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_testmod.o.cmd
Removing tools/testing/selftests/bpf/test_kmods/.bpf_testmod.o.d
Removing tools/testing/selftests/bpf/test_kmods/.module-common.o
Removing tools/testing/selftests/bpf/test_kmods/.modules.order.cmd
Removing tools/testing/selftests/bpf/test_kmods/Module.symvers
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_modorder_x.ko
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_modorder_x.mod
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_modorder_x.mod.c
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_modorder_x.mod.o
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_modorder_x.o
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_modorder_y.ko
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_modorder_y.mod
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_modorder_y.mod.c
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_modorder_y.mod.o
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_modorder_y.o
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_no_cfi.ko
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_no_cfi.mod
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_no_cfi.mod.c
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_no_cfi.mod.o
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_no_cfi.o
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_rqspinlock.ko
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_rqspinlock.mod
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_rqspinlock.mod.c
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_rqspinlock.mod.o
Removing tools/testing/selftests/bpf/test_kmods/bpf_test_rqspinlock.o
Removing tools/testing/selftests/bpf/test_kmods/bpf_testmod.ko
Removing tools/testing/selftests/bpf/test_kmods/bpf_testmod.mod
Removing tools/testing/selftests/bpf/test_kmods/bpf_testmod.mod.c
Removing tools/testing/selftests/bpf/test_kmods/bpf_testmod.mod.o
Removing tools/testing/selftests/bpf/test_kmods/bpf_testmod.o
Removing tools/testing/selftests/bpf/test_kmods/modules.order
Removing tools/testing/selftests/bpf/verification_cert.h
Removing tools/testing/selftests/bpf/verifier/tests.h

This series fixes this.

Assisted-by: claude sonnet
Signed-off-by: Ricardo B. Marlière (SUSE) <ricardo@marliere.net>
---
Ricardo B. Marlière (SUSE) (3):
      selftests/bpf: Route generated test headers to OUTPUT
      selftests/bpf: Route libarena build artifacts to OUTPUT
      selftests/bpf: Route test_kmods build artifacts to OUTPUT

 tools/testing/selftests/bpf/Makefile            | 45 ++++++++++++++-----------
 tools/testing/selftests/bpf/libarena/Makefile   | 24 +++++++------
 tools/testing/selftests/bpf/test_kmods/Makefile |  3 ++
 3 files changed, 42 insertions(+), 30 deletions(-)
---
base-commit: 62cc90241548d5570ee68e01aaba6506964e9811
change-id: 20260728-selftests-bpf_oot-da8b59be69fc

Best regards,
--  
Ricardo B. Marlière (SUSE) <ricardo@marliere.net>

[PATCH 1/3] selftests/bpf: Route generated test headers to OUTPUT

[Ricardo B. Marlière (SUSE)]

When building with O= the test-runner enumeration headers
(prog_tests/tests.h, map_tests/tests.h), the verifier test list
(verifier/tests.h) and the signing certificate header (verification_cert.h)
are written into the source tree instead of the out-of-tree build
directory.

Fix TRUNNER_TESTS_HDR to resolve under $(OUTPUT) and add an order-only
prerequisite so the subdirectory exists before the recipe runs. The mkdir
must precede the shell redirect in the same command, so use '&&' rather
than nesting mkdir inside the parenthesised group (the redirect opens the
file before the subshell starts).

Fix VERIFY_SIG_HDR likewise; the recipe already writes to $@ so no further
changes are needed there.

For verifier/tests.h, also resolve the target under $(OUTPUT) and generate
absolute paths in the '#include' directives, since the relative '"file.c"'
form would resolve against the output directory rather than the source
tree.

Signed-off-by: Ricardo B. Marlière (SUSE) <ricardo@marliere.net>
---
 tools/testing/selftests/bpf/Makefile | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index b642ee489ea6..b289183475d4 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -580,7 +580,7 @@ TRUNNER_EXTRA_OBJS := $$(patsubst %.c,$$(TRUNNER_OUTPUT)/%.o,		\
 TRUNNER_LIB_OBJS := $$(patsubst %.c,$$(TRUNNER_OUTPUT)/%.o,		\
 				 $$(filter %.c,$(TRUNNER_LIB_SOURCES)))
 TRUNNER_EXTRA_HDRS := $$(filter %.h,$(TRUNNER_EXTRA_SOURCES))
-TRUNNER_TESTS_HDR := $(TRUNNER_TESTS_DIR)/tests.h
+TRUNNER_TESTS_HDR := $(OUTPUT)/$(TRUNNER_TESTS_DIR)/tests.h
 TRUNNER_BPF_SRCS := $$(notdir $$(wildcard $(TRUNNER_BPF_PROGS_DIR)/*.c))
 TRUNNER_BPF_OBJS := $$(patsubst %.c,$$(TRUNNER_OUTPUT)/%.bpf.o, $$(TRUNNER_BPF_SRCS))
 TRUNNER_BPF_SKELS := $$(patsubst %.c,$$(TRUNNER_OUTPUT)/%.skel.h,	\
@@ -720,9 +720,9 @@ endif
 # ensure we set up tests.h header generation rule just once
 ifeq ($($(TRUNNER_TESTS_DIR)-tests-hdr),)
 $(TRUNNER_TESTS_DIR)-tests-hdr := y
-$(TRUNNER_TESTS_HDR): $(TRUNNER_TESTS_DIR)/*.c
+$(TRUNNER_TESTS_HDR): $(TRUNNER_TESTS_DIR)/*.c | $(TRUNNER_OUTPUT)
 	$$(call msg,TEST-HDR,$(TRUNNER_BINARY),$$@)
-	$$(shell (echo '/* Generated header, do not edit */';					\
+	$$(shell mkdir -p $$(dir $$@) && (echo '/* Generated header, do not edit */';			\
 		  sed -n -E 's/^void (serial_)?test_([a-zA-Z0-9_]+)\((void)?\).*/DEFINE_TEST(\2)/p'	\
 			$(TRUNNER_TESTS_DIR)/*.c | sort ;	\
 		 ) > $$@)
@@ -802,7 +802,7 @@ $(OUTPUT)/$(TRUNNER_BINARY): $(if $(filter test_progs%,$1),$(if $(PERMISSIVE),$$
 endef
 
 VERIFY_SIG_SETUP := $(CURDIR)/verify_sig_setup.sh
-VERIFY_SIG_HDR := verification_cert.h
+VERIFY_SIG_HDR := $(OUTPUT)/verification_cert.h
 VERIFICATION_CERT   := $(BUILD_DIR)/signing_key.der
 PRIVATE_KEY := $(BUILD_DIR)/signing_key.pem
 
@@ -923,14 +923,14 @@ $(eval $(call DEFINE_TEST_RUNNER,test_maps))
 # It is much simpler than test_maps/test_progs and sufficiently different from
 # them (e.g., test.h is using completely pattern), that it's worth just
 # explicitly defining all the rules explicitly.
-verifier/tests.h: verifier/*.c
-	$(shell ( cd verifier/; \
+$(OUTPUT)/verifier/tests.h: verifier/*.c | $(OUTPUT)
+	$(shell mkdir -p $(OUTPUT)/verifier && ( \
 		  echo '/* Generated header, do not edit */'; \
 		  echo '#ifdef FILL_ARRAY'; \
-		  ls *.c 2> /dev/null | sed -e 's@\(.*\)@#include \"\1\"@'; \
+		  ls verifier/*.c 2> /dev/null | sed -e 's@\(.*\)@#include "$(CURDIR)/\1"@'; \
 		  echo '#endif' \
-		) > verifier/tests.h)
-$(OUTPUT)/test_verifier: test_verifier.c verifier/tests.h $(BPFOBJ) | $(OUTPUT)
+		) > $(OUTPUT)/verifier/tests.h)
+$(OUTPUT)/test_verifier: test_verifier.c $(OUTPUT)/verifier/tests.h $(BPFOBJ) | $(OUTPUT)
 	$(call msg,BINARY,,$@)
 	$(Q)$(CC) $(CFLAGS) $(filter %.a %.o %.c,$^) $(LDLIBS) -o $@
 

-- 
2.55.0

[PATCH 2/3] selftests/bpf: Route libarena build artifacts to OUTPUT

[Ricardo B. Marlière (SUSE)]

libarena's BPF objects, linked objects, and skeleton headers are always
written into the source tree regardless of whether an out-of-tree build
directory was specified via O=.

Add OUTPUT support to libarena/Makefile: default OUTPUT to '.' for
standalone builds, prefix all generated file targets with $(OUTPUT)/, and
use addprefix to propagate the directory into the per-object lists. Create
$(OUTPUT) at Makefile-load time with a $(shell mkdir -p) so all rules have
a valid destination.

In the parent bpf/Makefile, pass OUTPUT="$(OUTPUT)/libarena" in
LIBARENA_MAKE_ARGS and update LIBARENA_SKEL/LIBARENA_ASAN_SKEL to reflect
the new location. Pass the absolute target path as the make goal so the
sub-make goal matches the $(OUTPUT)/... rule in libarena/Makefile
regardless of the invocation directory.

Signed-off-by: Ricardo B. Marlière (SUSE) <ricardo@marliere.net>
---
 tools/testing/selftests/bpf/Makefile          | 11 ++++++-----
 tools/testing/selftests/bpf/libarena/Makefile | 24 ++++++++++++++----------
 2 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index b289183475d4..7d42632f9d42 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -826,7 +826,8 @@ LIBARENA_MAKE_ARGS = \
 		CLANG="$(CLANG)" \
 		BPF_CFLAGS="$(BPF_CFLAGS) $(CLANG_CFLAGS)" \
 		BPF_TARGET_ENDIAN="$(BPF_TARGET_ENDIAN)" \
-		Q="$(Q)"
+		Q="$(Q)" \
+		OUTPUT="$(OUTPUT)/libarena"
 
 LIBARENA_BPF_DEPS := $(wildcard libarena/Makefile		\
 				 libarena/include/*		\
@@ -835,17 +836,17 @@ LIBARENA_BPF_DEPS := $(wildcard libarena/Makefile		\
 				 libarena/selftests/*		\
 				 libarena/*.bpf.o)
 
-LIBARENA_SKEL := libarena/libarena.skel.h
+LIBARENA_SKEL := $(OUTPUT)/libarena/libarena.skel.h
 
 $(LIBARENA_SKEL): $(INCLUDE_DIR)/vmlinux.h $(BPFOBJ) $(LIBARENA_BPF_DEPS)
-	+$(MAKE) -C libarena libarena.skel.h $(LIBARENA_MAKE_ARGS)
+	+$(MAKE) -C libarena $(LIBARENA_SKEL) $(LIBARENA_MAKE_ARGS)
 
 ifneq ($(CLANG_HAS_ARENA_ASAN),)
-LIBARENA_ASAN_SKEL := libarena/libarena_asan.skel.h
+LIBARENA_ASAN_SKEL := $(OUTPUT)/libarena/libarena_asan.skel.h
 CFLAGS += -DHAS_BPF_ARENA_ASAN
 
 $(LIBARENA_ASAN_SKEL): $(INCLUDE_DIR)/vmlinux.h $(BPFOBJ) $(LIBARENA_BPF_DEPS)
-	+$(MAKE) -C libarena libarena_asan.skel.h $(LIBARENA_MAKE_ARGS)
+	+$(MAKE) -C libarena $(LIBARENA_ASAN_SKEL) $(LIBARENA_MAKE_ARGS)
 endif
 
 # Define test_progs test runner.
diff --git a/tools/testing/selftests/bpf/libarena/Makefile b/tools/testing/selftests/bpf/libarena/Makefile
index 5e2ab514805e..195d5f833186 100644
--- a/tools/testing/selftests/bpf/libarena/Makefile
+++ b/tools/testing/selftests/bpf/libarena/Makefile
@@ -27,10 +27,14 @@ BPFDIR=$(abspath $(LIBARENA)/..)
 INCLUDE_DIR ?= $(BPFDIR)/tools/include
 LIBBPF_INCLUDE ?= $(INCLUDE_DIR)
 
+# Build output directory; defaults to in-tree for standalone builds.
+OUTPUT ?= .
+$(shell mkdir -p $(OUTPUT))
+
 # Scan src/ and selftests/ to generate the final binaries
 LIBARENA_SOURCES = $(wildcard $(LIBARENA)/src/*.bpf.c) $(wildcard $(LIBARENA)/selftests/*.bpf.c)
-LIBARENA_OBJECTS = $(notdir $(LIBARENA_SOURCES:.bpf.c=.bpf.o))
-LIBARENA_OBJECTS_ASAN = $(notdir $(LIBARENA_SOURCES:.bpf.c=_asan.bpf.o))
+LIBARENA_OBJECTS = $(addprefix $(OUTPUT)/,$(notdir $(LIBARENA_SOURCES:.bpf.c=.bpf.o)))
+LIBARENA_OBJECTS_ASAN = $(addprefix $(OUTPUT)/,$(notdir $(LIBARENA_SOURCES:.bpf.c=_asan.bpf.o)))
 
 INCLUDES = -I$(LIBARENA)/include -I$(BPFDIR)
 ifneq ($(INCLUDE_DIR),)
@@ -61,32 +65,32 @@ CFLAGS += $(INCLUDES)
 vpath %.bpf.c $(LIBARENA)/src $(LIBARENA)/selftests
 vpath %.c $(LIBARENA)/src $(LIBARENA)/selftests
 
-skeletons: libarena.skel.h libarena_asan.skel.h
+skeletons: $(OUTPUT)/libarena.skel.h $(OUTPUT)/libarena_asan.skel.h
 .PHONY: skeletons
 
-libarena_asan.skel.h: libarena_asan.bpf.o
+$(OUTPUT)/libarena_asan.skel.h: $(OUTPUT)/libarena_asan.bpf.o
 	$(call msg,GEN-SKEL,libarena,$@)
 	$(Q)$(BPFTOOL) gen skeleton $< name "libarena_asan" > $@
 
-libarena.skel.h: libarena.bpf.o
+$(OUTPUT)/libarena.skel.h: $(OUTPUT)/libarena.bpf.o
 	$(call msg,GEN-SKEL,libarena,$@)
 	$(Q)$(BPFTOOL) gen skeleton $< name "libarena" > $@
 
-libarena_asan.bpf.o: $(LIBARENA_OBJECTS_ASAN)
+$(OUTPUT)/libarena_asan.bpf.o: $(LIBARENA_OBJECTS_ASAN)
 	$(call msg,GEN-OBJ,libarena,$@)
 	$(Q)$(BPFTOOL) gen object $@ $^
 
-libarena.bpf.o: $(LIBARENA_OBJECTS)
+$(OUTPUT)/libarena.bpf.o: $(LIBARENA_OBJECTS)
 	$(call msg,GEN-OBJ,libarena,$@)
 	$(Q)$(BPFTOOL) gen object $@ $^
 
-%_asan.bpf.o: %.bpf.c
+$(OUTPUT)/%_asan.bpf.o: %.bpf.c
 	$(call msg,CLNG-BPF,libarena,$@)
 	$(Q)$(CLANG) $(BPF_CFLAGS) $(ASAN_FLAGS) -DBPF_ARENA_ASAN $(BPF_TARGET_ENDIAN) -c $< -o $@
 
-%.bpf.o: %.bpf.c
+$(OUTPUT)/%.bpf.o: %.bpf.c
 	$(call msg,CLNG-BPF,libarena,$@)
 	$(Q)$(CLANG) $(BPF_CFLAGS) $(BPF_TARGET_ENDIAN) -c $< -o $@
 
 clean:
-	$(Q)rm -f *.skel.h *.bpf.o *.linked*.o
+	$(Q)rm -f $(OUTPUT)/*.skel.h $(OUTPUT)/*.bpf.o $(OUTPUT)/*.linked*.o

-- 
2.55.0

[PATCH 3/3] selftests/bpf: Route test_kmods build artifacts to OUTPUT

[Ricardo B. Marlière (SUSE)]

When building bpf selftests with O=, the kernel module intermediates (.ko,
.o, .mod.*, .cmd files, Module.symvers, modules.order) produced by the
test_kmods sub-make are placed in the source tree instead of the
out-of-tree directory, because kbuild external-module builds always write
output to the M= source directory by default.

Introduce TEST_KMODS_OUTDIR in bpf/Makefile that resolves to
$(OUTPUT)/test_kmods when OUTPUT is set, and fall back to the in-tree
test_kmods/ directory for standalone builds. Update the pattern rule, the
RM invocation, and the copy rule to use this variable, and pass
OUTPUT=$(OUTPUT)/test_kmods to the test_kmods sub-make.

In test_kmods/Makefile, forward the received OUTPUT value as MO= to the
kernel Makefile. The top-level kernel Makefile maps MO= to
KBUILD_EXTMOD_OUTPUT, which redirects all external-module build output to
the specified directory. The kernel also creates that directory
automatically, so no explicit mkdir is needed.

Also update the CLEAN target in bpf/Makefile to propagate OUTPUT to both
the test_kmods and libarena sub-makes so that clean removes from the
correct location.

Signed-off-by: Ricardo B. Marlière (SUSE) <ricardo@marliere.net>
---
 tools/testing/selftests/bpf/Makefile            | 16 ++++++++++------
 tools/testing/selftests/bpf/test_kmods/Makefile |  3 +++
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 7d42632f9d42..b150a66f3c25 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -135,6 +135,9 @@ TEST_PROGS_EXTENDED := \
 TEST_KMODS := bpf_testmod.ko bpf_test_no_cfi.ko bpf_test_modorder_x.ko \
 	bpf_test_modorder_y.ko bpf_test_rqspinlock.ko
 TEST_KMOD_TARGETS = $(addprefix $(OUTPUT)/,$(TEST_KMODS))
+# Build directory for kernel modules: routed to $(OUTPUT)/test_kmods when
+# OUTPUT is set so that kbuild intermediates stay out of the source tree.
+TEST_KMODS_OUTDIR := $(if $(OUTPUT),$(OUTPUT)/test_kmods,test_kmods)
 
 # Compile but not part of 'make run_tests'
 TEST_GEN_PROGS_EXTENDED = \
@@ -163,8 +166,8 @@ override define CLEAN
 	$(Q)$(RM) -r $(TEST_GEN_FILES)
 	$(Q)$(RM) -r $(TEST_KMODS)
 	$(Q)$(RM) -r $(EXTRA_CLEAN)
-	$(Q)$(MAKE) -C test_kmods clean
-	$(Q)$(MAKE) -C libarena clean
+	$(Q)$(MAKE) -C test_kmods $(if $(OUTPUT),OUTPUT=$(OUTPUT)/test_kmods) clean
+	$(Q)$(MAKE) -C libarena $(if $(OUTPUT),OUTPUT=$(OUTPUT)/libarena) clean
 	$(Q)$(MAKE) docs-clean
 endef
 
@@ -301,17 +304,18 @@ $(OUTPUT)/sign-file: ../../../../scripts/sign-file.c
 # support that for regular rules. However, pattern matching rules are implicitly
 # treated as grouped even with older versions of make, so as a workaround, the
 # subst() turns the rule into a pattern matching rule
-$(addprefix test_kmods/,$(subst .ko,%ko,$(TEST_KMODS))): $(VMLINUX_BTF) $(RESOLVE_BTFIDS) $(wildcard test_kmods/Makefile test_kmods/*.[ch])
-	$(Q)$(RM) test_kmods/*.ko test_kmods/*.mod.o # force re-compilation
+$(addprefix $(TEST_KMODS_OUTDIR)/,$(subst .ko,%ko,$(TEST_KMODS))): $(VMLINUX_BTF) $(RESOLVE_BTFIDS) $(wildcard test_kmods/Makefile test_kmods/*.[ch])
+	$(Q)$(RM) $(TEST_KMODS_OUTDIR)/*.ko $(TEST_KMODS_OUTDIR)/*.mod.o # force re-compilation
 	$(Q)$(MAKE) $(submake_extras) -C test_kmods				\
 		$(if $(O),O=$(abspath $(O)))					\
 		$(if $(KBUILD_OUTPUT),KBUILD_OUTPUT=$(abspath $(KBUILD_OUTPUT)))\
+		$(if $(OUTPUT),OUTPUT=$(OUTPUT)/test_kmods)			\
 		RESOLVE_BTFIDS=$(RESOLVE_BTFIDS)				\
 		EXTRA_CFLAGS='' EXTRA_LDFLAGS=''
 
-$(TEST_KMOD_TARGETS): $(addprefix test_kmods/,$(TEST_KMODS))
+$(TEST_KMOD_TARGETS): $(addprefix $(TEST_KMODS_OUTDIR)/,$(TEST_KMODS))
 	$(call msg,MOD,,$@)
-	$(Q)$(if $(PERMISSIVE),if [ -f test_kmods/$(@F) ]; then )cp test_kmods/$(@F) $@$(if $(PERMISSIVE),; fi)
+	$(Q)$(if $(PERMISSIVE),if [ -f $(TEST_KMODS_OUTDIR)/$(@F) ]; then )cp $(TEST_KMODS_OUTDIR)/$(@F) $@$(if $(PERMISSIVE),; fi)
 
 
 DEFAULT_BPFTOOL := $(HOST_SCRATCH_DIR)/sbin/bpftool
diff --git a/tools/testing/selftests/bpf/test_kmods/Makefile b/tools/testing/selftests/bpf/test_kmods/Makefile
index 031c7454ce65..53e47e715ec4 100644
--- a/tools/testing/selftests/bpf/test_kmods/Makefile
+++ b/tools/testing/selftests/bpf/test_kmods/Makefile
@@ -32,14 +32,17 @@ PERMISSIVE := $(filter 0,$(BPF_STRICT_BUILD))
 all:
 ifeq ($(PERMISSIVE),)
 	$(Q)$(MAKE) -C $(KDIR) $(if $(KMOD_O_VALID),O=$(KMOD_O_VALID) KBUILD_OUTPUT=$(KMOD_O_VALID),KBUILD_OUTPUT=) \
+		$(if $(OUTPUT),MO=$(OUTPUT)) \
 		M=$(TEST_KMOD_DIR) modules
 else ifneq ("$(wildcard $(KDIR))", "")
 	$(Q)$(MAKE) -C $(KDIR) $(if $(KMOD_O_VALID),O=$(KMOD_O_VALID) KBUILD_OUTPUT=$(KMOD_O_VALID),KBUILD_OUTPUT=) \
+		$(if $(OUTPUT),MO=$(OUTPUT)) \
 		M=$(TEST_KMOD_DIR) modules
 endif
 
 clean:
 ifneq ("$(wildcard $(KDIR))", "")
 	$(Q)$(MAKE) -C $(KDIR) $(if $(KMOD_O_VALID),O=$(KMOD_O_VALID) KBUILD_OUTPUT=$(KMOD_O_VALID),KBUILD_OUTPUT=) \
+		$(if $(OUTPUT),MO=$(OUTPUT)) \
 		M=$(TEST_KMOD_DIR) clean
 endif

-- 
2.55.0

Re: [PATCH 0/3] selftests/bpf: Fixes for out-of-tree builds

[Ihor Solodrai]

On 7/28/26 5:06 PM, Ricardo B. Marlière (SUSE) wrote:
> Hello,
> 
> When doing a simple out-of-tree build, e.g.:
> 
> $ git clean -fdx
> $ mkdir ../build
> $ make defconfig O=../build
> $ scripts/kconfig/merge_config.sh -O ../build ../build/.config tools/testing/selftests/bpf/{config,config.x86_64}
> $ make O=../build
> $ make -C tools/testing/selftests install O=$PWD/../build SKIP_TARGETS= TARGETS=bpf
> 
> Will leave behind several build artifacts:
> 
> [...]
> 
> This series fixes this.

Hi Ricardo,

I think we should wait for the selftests makefile refactoring series [1]
to land first, and then address the issues you've found.

When you do the respin, please test both build and clean with an
in-tree kernel build and with O=

Sending a few comments in a bit.

[1] https://lore.kernel.org/bpf/20260804170156.1709916-1-nickolay.lysenko@gmail.com/


> 
> [...]
> 

Re: [PATCH 1/3] selftests/bpf: Route generated test headers to OUTPUT

[Ihor Solodrai]

On 7/28/26 5:06 PM, Ricardo B. Marlière (SUSE) wrote:
> [...]
>  
> @@ -923,14 +923,14 @@ $(eval $(call DEFINE_TEST_RUNNER,test_maps))
>  # It is much simpler than test_maps/test_progs and sufficiently different from
>  # them (e.g., test.h is using completely pattern), that it's worth just
>  # explicitly defining all the rules explicitly.
> -verifier/tests.h: verifier/*.c
> -	$(shell ( cd verifier/; \
> +$(OUTPUT)/verifier/tests.h: verifier/*.c | $(OUTPUT)
> +	$(shell mkdir -p $(OUTPUT)/verifier && ( \
>  		  echo '/* Generated header, do not edit */'; \
>  		  echo '#ifdef FILL_ARRAY'; \
> -		  ls *.c 2> /dev/null | sed -e 's@\(.*\)@#include \"\1\"@'; \
> +		  ls verifier/*.c 2> /dev/null | sed -e 's@\(.*\)@#include "$(CURDIR)/\1"@'; \

This can break if $(CURDIR) contains '@'.

In such case sed fails, but make returns success and generates
verifier/tests.h with zero #include lines. And this would silently
skip all the tests.

Also at line 1046:

EXTRA_CLEAN := $(SCRATCH_DIR) $(HOST_SCRATCH_DIR)			\
	prog_tests/tests.h map_tests/tests.h verifier/tests.h		\

These are the old source-tree locations. Should be updated?

>  		  echo '#endif' \
> -		) > verifier/tests.h)
> -$(OUTPUT)/test_verifier: test_verifier.c verifier/tests.h $(BPFOBJ) | $(OUTPUT)
> +		) > $(OUTPUT)/verifier/tests.h)
> +$(OUTPUT)/test_verifier: test_verifier.c $(OUTPUT)/verifier/tests.h $(BPFOBJ) | $(OUTPUT)
>  	$(call msg,BINARY,,$@)
>  	$(Q)$(CC) $(CFLAGS) $(filter %.a %.o %.c,$^) $(LDLIBS) -o $@
>  
> 

Re: [PATCH 2/3] selftests/bpf: Route libarena build artifacts to OUTPUT

[Ihor Solodrai]

On 7/28/26 5:06 PM, Ricardo B. Marlière (SUSE) wrote:
> libarena's BPF objects, linked objects, and skeleton headers are always
> written into the source tree regardless of whether an out-of-tree build
> directory was specified via O=.
> 
> Add OUTPUT support to libarena/Makefile: default OUTPUT to '.' for
> standalone builds, prefix all generated file targets with $(OUTPUT)/, and
> use addprefix to propagate the directory into the per-object lists. Create
> $(OUTPUT) at Makefile-load time with a $(shell mkdir -p) so all rules have
> a valid destination.
> 
> In the parent bpf/Makefile, pass OUTPUT="$(OUTPUT)/libarena" in
> LIBARENA_MAKE_ARGS and update LIBARENA_SKEL/LIBARENA_ASAN_SKEL to reflect
> the new location. Pass the absolute target path as the make goal so the
> sub-make goal matches the $(OUTPUT)/... rule in libarena/Makefile
> regardless of the invocation directory.
> 
> Signed-off-by: Ricardo B. Marlière (SUSE) <ricardo@marliere.net>
> ---
>  tools/testing/selftests/bpf/Makefile          | 11 ++++++-----
>  tools/testing/selftests/bpf/libarena/Makefile | 24 ++++++++++++++----------
>  2 files changed, 20 insertions(+), 15 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index b289183475d4..7d42632f9d42 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -826,7 +826,8 @@ LIBARENA_MAKE_ARGS = \
>  		CLANG="$(CLANG)" \
>  		BPF_CFLAGS="$(BPF_CFLAGS) $(CLANG_CFLAGS)" \
>  		BPF_TARGET_ENDIAN="$(BPF_TARGET_ENDIAN)" \
> -		Q="$(Q)"
> +		Q="$(Q)" \
> +		OUTPUT="$(OUTPUT)/libarena"
>  
>  LIBARENA_BPF_DEPS := $(wildcard libarena/Makefile		\
>  				 libarena/include/*		\
> @@ -835,17 +836,17 @@ LIBARENA_BPF_DEPS := $(wildcard libarena/Makefile		\
>  				 libarena/selftests/*		\
>  				 libarena/*.bpf.o)
>  
> -LIBARENA_SKEL := libarena/libarena.skel.h
> +LIBARENA_SKEL := $(OUTPUT)/libarena/libarena.skel.h
>  
>  $(LIBARENA_SKEL): $(INCLUDE_DIR)/vmlinux.h $(BPFOBJ) $(LIBARENA_BPF_DEPS)
> -	+$(MAKE) -C libarena libarena.skel.h $(LIBARENA_MAKE_ARGS)
> +	+$(MAKE) -C libarena $(LIBARENA_SKEL) $(LIBARENA_MAKE_ARGS)
>  
>  ifneq ($(CLANG_HAS_ARENA_ASAN),)
> -LIBARENA_ASAN_SKEL := libarena/libarena_asan.skel.h
> +LIBARENA_ASAN_SKEL := $(OUTPUT)/libarena/libarena_asan.skel.h
>  CFLAGS += -DHAS_BPF_ARENA_ASAN
>  
>  $(LIBARENA_ASAN_SKEL): $(INCLUDE_DIR)/vmlinux.h $(BPFOBJ) $(LIBARENA_BPF_DEPS)
> -	+$(MAKE) -C libarena libarena_asan.skel.h $(LIBARENA_MAKE_ARGS)
> +	+$(MAKE) -C libarena $(LIBARENA_ASAN_SKEL) $(LIBARENA_MAKE_ARGS)
>  endif
>  
>  # Define test_progs test runner.
> diff --git a/tools/testing/selftests/bpf/libarena/Makefile b/tools/testing/selftests/bpf/libarena/Makefile
> index 5e2ab514805e..195d5f833186 100644
> --- a/tools/testing/selftests/bpf/libarena/Makefile
> +++ b/tools/testing/selftests/bpf/libarena/Makefile
> @@ -27,10 +27,14 @@ BPFDIR=$(abspath $(LIBARENA)/..)
>  INCLUDE_DIR ?= $(BPFDIR)/tools/include
>  LIBBPF_INCLUDE ?= $(INCLUDE_DIR)
>  
> +# Build output directory; defaults to in-tree for standalone builds.
> +OUTPUT ?= .
> +$(shell mkdir -p $(OUTPUT))

This runs while make parses the file, including under make -n, and
discards mkdir's status. Let's create $(OUTPUT) via order-only
directory prereq instead.

> +
>  # Scan src/ and selftests/ to generate the final binaries
>  LIBARENA_SOURCES = $(wildcard $(LIBARENA)/src/*.bpf.c) $(wildcard $(LIBARENA)/selftests/*.bpf.c)
> -LIBARENA_OBJECTS = $(notdir $(LIBARENA_SOURCES:.bpf.c=.bpf.o))
> -LIBARENA_OBJECTS_ASAN = $(notdir $(LIBARENA_SOURCES:.bpf.c=_asan.bpf.o))
> +LIBARENA_OBJECTS = $(addprefix $(OUTPUT)/,$(notdir $(LIBARENA_SOURCES:.bpf.c=.bpf.o)))
> +LIBARENA_OBJECTS_ASAN = $(addprefix $(OUTPUT)/,$(notdir $(LIBARENA_SOURCES:.bpf.c=_asan.bpf.o)))
>  
>  INCLUDES = -I$(LIBARENA)/include -I$(BPFDIR)
>  ifneq ($(INCLUDE_DIR),)
> @@ -61,32 +65,32 @@ CFLAGS += $(INCLUDES)
>  vpath %.bpf.c $(LIBARENA)/src $(LIBARENA)/selftests
>  vpath %.c $(LIBARENA)/src $(LIBARENA)/selftests
>  
> -skeletons: libarena.skel.h libarena_asan.skel.h
> +skeletons: $(OUTPUT)/libarena.skel.h $(OUTPUT)/libarena_asan.skel.h
>  .PHONY: skeletons
>  
> -libarena_asan.skel.h: libarena_asan.bpf.o
> +$(OUTPUT)/libarena_asan.skel.h: $(OUTPUT)/libarena_asan.bpf.o
>  	$(call msg,GEN-SKEL,libarena,$@)
>  	$(Q)$(BPFTOOL) gen skeleton $< name "libarena_asan" > $@
>  
> -libarena.skel.h: libarena.bpf.o
> +$(OUTPUT)/libarena.skel.h: $(OUTPUT)/libarena.bpf.o
>  	$(call msg,GEN-SKEL,libarena,$@)
>  	$(Q)$(BPFTOOL) gen skeleton $< name "libarena" > $@
>  
> -libarena_asan.bpf.o: $(LIBARENA_OBJECTS_ASAN)
> +$(OUTPUT)/libarena_asan.bpf.o: $(LIBARENA_OBJECTS_ASAN)
>  	$(call msg,GEN-OBJ,libarena,$@)
>  	$(Q)$(BPFTOOL) gen object $@ $^
>  
> -libarena.bpf.o: $(LIBARENA_OBJECTS)
> +$(OUTPUT)/libarena.bpf.o: $(LIBARENA_OBJECTS)
>  	$(call msg,GEN-OBJ,libarena,$@)
>  	$(Q)$(BPFTOOL) gen object $@ $^
>  
> -%_asan.bpf.o: %.bpf.c
> +$(OUTPUT)/%_asan.bpf.o: %.bpf.c
>  	$(call msg,CLNG-BPF,libarena,$@)
>  	$(Q)$(CLANG) $(BPF_CFLAGS) $(ASAN_FLAGS) -DBPF_ARENA_ASAN $(BPF_TARGET_ENDIAN) -c $< -o $@
>  
> -%.bpf.o: %.bpf.c
> +$(OUTPUT)/%.bpf.o: %.bpf.c
>  	$(call msg,CLNG-BPF,libarena,$@)
>  	$(Q)$(CLANG) $(BPF_CFLAGS) $(BPF_TARGET_ENDIAN) -c $< -o $@
>  
>  clean:
> -	$(Q)rm -f *.skel.h *.bpf.o *.linked*.o
> +	$(Q)rm -f $(OUTPUT)/*.skel.h $(OUTPUT)/*.bpf.o $(OUTPUT)/*.linked*.o
> 

Re: [PATCH 3/3] selftests/bpf: Route test_kmods build artifacts to OUTPUT

[Ihor Solodrai]

On 7/28/26 5:06 PM, Ricardo B. Marlière (SUSE) wrote:
> [...]
> 
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index 7d42632f9d42..b150a66f3c25 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -135,6 +135,9 @@ TEST_PROGS_EXTENDED := \
>  TEST_KMODS := bpf_testmod.ko bpf_test_no_cfi.ko bpf_test_modorder_x.ko \
>  	bpf_test_modorder_y.ko bpf_test_rqspinlock.ko
>  TEST_KMOD_TARGETS = $(addprefix $(OUTPUT)/,$(TEST_KMODS))
> +# Build directory for kernel modules: routed to $(OUTPUT)/test_kmods when
> +# OUTPUT is set so that kbuild intermediates stay out of the source tree.
> +TEST_KMODS_OUTDIR := $(if $(OUTPUT),$(OUTPUT)/test_kmods,test_kmods)
>  
>  # Compile but not part of 'make run_tests'
>  TEST_GEN_PROGS_EXTENDED = \
> @@ -163,8 +166,8 @@ override define CLEAN
>  	$(Q)$(RM) -r $(TEST_GEN_FILES)
>  	$(Q)$(RM) -r $(TEST_KMODS)
>  	$(Q)$(RM) -r $(EXTRA_CLEAN)
> -	$(Q)$(MAKE) -C test_kmods clean
> -	$(Q)$(MAKE) -C libarena clean
> +	$(Q)$(MAKE) -C test_kmods $(if $(OUTPUT),OUTPUT=$(OUTPUT)/test_kmods) clean
> +	$(Q)$(MAKE) -C libarena $(if $(OUTPUT),OUTPUT=$(OUTPUT)/libarena) clean

This is broken. What happens if the caller set OUTPUT but not O= ?

If at linux root you do:

  $ make defconfig && make -j$(nproc)
  $ mkdir -p /tmp/kout
  $ make -C tools/testing/selftests/bpf OUTPUT=/tmp/kout clean

it destroys the root Makefile:

  $ git diff --stat -- Makefile
  Makefile | 2364 +------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  1 file changed, 5 insertions(+), 2359 deletions(-)

  $ cat Makefile
  # Automatically generated by /home/isolodrai/sandbox/2026-08-06.review.out-of-tree-fixes/linux/Makefile: don't edit
  export KBUILD_OUTPUT = /home/isolodrai/sandbox/2026-08-06.review.out-of-tree-fixes/linux
  export KBUILD_EXTMOD = /home/isolodrai/sandbox/2026-08-06.review.out-of-tree-fixes/linux/tools/testing/selftests/bpf/test_kmods
  export KBUILD_EXTMOD_OUTPUT = /tmp/kout/test_kmods
  include /home/isolodrai/sandbox/2026-08-06.review.out-of-tree-fixes/linux/Makefile

pw-bot: cr


Also the selftests clean loop runs clean rules this way [1]:

clean:
	@for TARGET in $(TARGETS) $(INSTALL_DEP_TARGETS); do \
		BUILD_TARGET=$$BUILD/$$TARGET;	\
		$(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET clean;\
	done;

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/testing/selftests/Makefile?h=v7.2-rc6#n325


>  	$(Q)$(MAKE) docs-clean
>  endef
>  
> [...]
> 

Re: [PATCH 0/3] selftests/bpf: Fixes for out-of-tree builds

[Ricardo B. Marlière]

On Thu Aug 6, 2026 at 5:29 PM -03, Ihor Solodrai wrote:
> On 7/28/26 5:06 PM, Ricardo B. Marlière (SUSE) wrote:
>> Hello,
>> 
>> When doing a simple out-of-tree build, e.g.:
>> 
>> $ git clean -fdx
>> $ mkdir ../build
>> $ make defconfig O=../build
>> $ scripts/kconfig/merge_config.sh -O ../build ../build/.config tools/testing/selftests/bpf/{config,config.x86_64}
>> $ make O=../build
>> $ make -C tools/testing/selftests install O=$PWD/../build SKIP_TARGETS= TARGETS=bpf
>> 
>> Will leave behind several build artifacts:
>> 
>> [...]
>> 
>> This series fixes this.
>
> Hi Ricardo,
>
> I think we should wait for the selftests makefile refactoring series [1]
> to land first, and then address the issues you've found.

Makes sense.

>
> When you do the respin, please test both build and clean with an
> in-tree kernel build and with O=
>
> Sending a few comments in a bit.

Ack, thanks for the reviews!

>
> [1] https://lore.kernel.org/bpf/20260804170156.1709916-1-nickolay.lysenko@gmail.com/
>
>
>> 
>> [...]
>>