Re: [PATCH v3] selftests: Fix seccomp to support relocatable build (O=objdir)

Michael Ellerman
2020-03-16T12:13:08Z

Shuah Khan <skhan@linuxfoundation.org> writes:
> Fix seccomp relocatable builds. This is a simple fix to use the right
> lib.mk variable TEST_GEN_PROGS with dependency on kselftest_harness.h
> header, and defining LDFLAGS for pthread lib.
>
> Removes custom clean rule which is no longer necessary with the use of
> TEST_GEN_PROGS.
>
> Uses $(OUTPUT) defined in lib.mk to handle build relocation.
>
> The following use-cases work with this change:
>
> In seccomp directory:
> make all and make clean
>
> From top level from main Makefile:
> make kselftest-install O=objdir ARCH=arm64 HOSTCC=gcc \
> CROSS_COMPILE=aarch64-linux-gnu- TARGETS=seccomp
>
> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
> ---
>
> Changes since v2:
> -- Using TEST_GEN_PROGS is sufficient to generate objects.
> Addresses review comments from Kees Cook.
>
> tools/testing/selftests/seccomp/Makefile | 18 ++++++++----------
> 1 file changed, 8 insertions(+), 10 deletions(-)
>
> diff --git a/tools/testing/selftests/seccomp/Makefile b/tools/testing/selftests/seccomp/Makefile
> index 1760b3e39730..a0388fd2c3f2 100644
> --- a/tools/testing/selftests/seccomp/Makefile
> +++ b/tools/testing/selftests/seccomp/Makefile
> @@ -1,17 +1,15 @@
> # SPDX-License-Identifier: GPL-2.0
> -all:
> -
> -include ../lib.mk
> +CFLAGS += -Wl,-no-as-needed -Wall
> +LDFLAGS += -lpthread
>
> .PHONY: all clean
>
> -BINARIES := seccomp_bpf seccomp_benchmark
> -CFLAGS += -Wl,-no-as-needed -Wall
> +include ../lib.mk
> +
> +# OUTPUT set by lib.mk
> +TEST_GEN_PROGS := $(OUTPUT)/seccomp_bpf $(OUTPUT)/seccomp_benchmark
>
> -seccomp_bpf: seccomp_bpf.c ../kselftest_harness.h
> - $(CC) $(CFLAGS) $(LDFLAGS) $< -lpthread -o $@
> +$(TEST_GEN_PROGS): ../kselftest_harness.h
>
> -TEST_PROGS += $(BINARIES)
> -EXTRA_CLEAN := $(BINARIES)
> +all: $(TEST_GEN_PROGS)
>
> -all: $(BINARIES)

It shouldn't be that complicated. We just need to define TEST_GEN_PROGS
before including lib.mk, and then add the dependency on the harness
after we include lib.mk (so that TEST_GEN_PROGS has been updated to
prefix $(OUTPUT)).

eg:

# SPDX-License-Identifier: GPL-2.0
CFLAGS += -Wl,-no-as-needed -Wall
LDFLAGS += -lpthread

TEST_GEN_PROGS := seccomp_bpf seccomp_benchmark

include ../lib.mk

$(TEST_GEN_PROGS): ../kselftest_harness.h

Normal in-tree build:

selftests$ make TARGETS=seccomp
make[1]: Entering directory '/home/michael/linux/tools/testing/selftests/seccomp'
gcc -Wl,-no-as-needed -Wall -lpthread seccomp_bpf.c ../kselftest_harness.h -o /home/michael/linux/tools/testing/selftests/seccomp/seccomp_bpf
gcc -Wl,-no-as-needed -Wall -lpthread seccomp_benchmark.c ../kselftest_harness.h -o /home/michael/linux/tools/testing/selftests/seccomp/seccomp_benchmark
make[1]: Leaving directory '/home/michael/linux/tools/testing/selftests/seccomp'

selftests$ ls -l seccomp/
total 388
-rw-rw-r-- 1 michael michael 41 Jan 9 12:00 config
-rw-rw-r-- 1 michael michael 201 Mar 16 23:04 Makefile
-rwxrwxr-x 1 michael michael 70824 Mar 16 23:07 seccomp_benchmark*
-rw-rw-r-- 1 michael michael 2289 Feb 17 21:39 seccomp_benchmark.c
-rwxrwxr-x 1 michael michael 290520 Mar 16 23:07 seccomp_bpf*
-rw-rw-r-- 1 michael michael 94778 Mar 5 23:33 seccomp_bpf.c

O= build:

selftests$ make TARGETS=seccomp O=$PWD/build
make[1]: Entering directory '/home/michael/linux/tools/testing/selftests/seccomp'
gcc -Wl,-no-as-needed -Wall -lpthread seccomp_bpf.c ../kselftest_harness.h -o /home/michael/linux/tools/testing/selftests/build/seccomp/seccomp_bpf
gcc -Wl,-no-as-needed -Wall -lpthread seccomp_benchmark.c ../kselftest_harness.h -o /home/michael/linux/tools/testing/selftests/build/seccomp/seccomp_benchmark
make[1]: Leaving directory '/home/michael/linux/tools/testing/selftests/seccomp'

selftests$ ls -l build/seccomp/
total 280
-rwxrwxr-x 1 michael michael 70824 Mar 16 23:05 seccomp_benchmark*
-rwxrwxr-x 1 michael michael 290520 Mar 16 23:05 seccomp_bpf*

Build in the directory itself:
selftests$ cd seccomp
seccomp$ make
gcc -Wl,-no-as-needed -Wall -lpthread seccomp_bpf.c ../kselftest_harness.h -o /home/michael/linux/tools/testing/selftests/seccomp/seccomp_bpf
gcc -Wl,-no-as-needed -Wall -lpthread seccomp_benchmark.c ../kselftest_harness.h -o /home/michael/linux/tools/testing/selftests/seccomp/seccomp_benchmark

seccomp$ ls -l
total 388
-rw-rw-r-- 1 michael michael 41 Jan 9 12:00 config
-rw-rw-r-- 1 michael michael 201 Mar 16 23:04 Makefile
-rwxrwxr-x 1 michael michael 70824 Mar 16 23:06 seccomp_benchmark*
-rw-rw-r-- 1 michael michael 2289 Feb 17 21:39 seccomp_benchmark.c
-rwxrwxr-x 1 michael michael 290520 Mar 16 23:06 seccomp_bpf*
-rw-rw-r-- 1 michael michael 94778 Mar 5 23:33 seccomp_bpf.c

cheers