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

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Date:   Fri, 13 Mar 2020 16:18:03 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     shuah@...nel.org, luto@...capital.net, wad@...omium.org,
        daniel@...earbox.net, kafai@...com, yhs@...com, andriin@...com,
        gregkh@...uxfoundation.org, tglx@...utronix.de,
        khilman@...libre.com, mpe@...erman.id.au,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v3] selftests: Fix seccomp to support relocatable build
 (O=objdir)

On Fri, Mar 13, 2020 at 03:24:04PM -0600, Shuah Khan wrote:
> 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@...uxfoundation.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

Isn't this line redundant to ../lib.mk's?

>  
> -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)

And isn't this one too?

I think if those are removed it should all still work? Regardless:

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

>  
> -all: $(BINARIES)
> -- 
> 2.20.1
> 

-- 
Kees Cook