linux-kernel - Re: [PATCH 2/4] selftests: Fix seccomp to support relocatable build (O=objdir)

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Date:   Thu, 05 Mar 2020 11:22:00 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Shuah Khan <skhan@...uxfoundation.org>,
        Kees Cook <keescook@...omium.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, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH 2/4] selftests: Fix seccomp to support relocatable build (O=objdir)

Shuah Khan <skhan@...uxfoundation.org> writes:
> On 3/4/20 3:42 PM, Kees Cook wrote:
>> On Wed, Mar 04, 2020 at 03:13:33PM -0700, Shuah Khan wrote:
>>> Fix seccomp relocatable builds. This is a simple fix to use the
>>> right lib.mk variable TEST_GEN_PROGS for objects to leverage
>>> lib.mk common framework for relocatable builds.
>>>
>>> Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
>>> ---
>>>   tools/testing/selftests/seccomp/Makefile | 16 +++-------------
>>>   1 file changed, 3 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/tools/testing/selftests/seccomp/Makefile b/tools/testing/selftests/seccomp/Makefile
>>> index 1760b3e39730..a8a9717fc1be 100644
>>> --- a/tools/testing/selftests/seccomp/Makefile
>>> +++ b/tools/testing/selftests/seccomp/Makefile
>>> @@ -1,17 +1,7 @@
>>>   # SPDX-License-Identifier: GPL-2.0
>>> -all:
>>> -
>>> -include ../lib.mk
>>> -
>>> -.PHONY: all clean
>>> -
>>> -BINARIES := seccomp_bpf seccomp_benchmark
>>>   CFLAGS += -Wl,-no-as-needed -Wall
>>> +LDFLAGS += -lpthread
>>>   
>>> -seccomp_bpf: seccomp_bpf.c ../kselftest_harness.h
>> 
>> How is the ../kselftest_harness.h dependency detected in the resulting
>> build rules?
>> 
>> Otherwise, looks good.
>
> Didn't see any problems. I will look into adding the dependency.

Before:

  $ make --no-print-directory -C tools/testing/selftests/ TARGETS=seccomp
  make --no-builtin-rules INSTALL_HDR_PATH=$BUILD/usr \
          ARCH=powerpc -C ../../.. headers_install
    INSTALL /home/michael/build/adhoc/kselftest/usr/include
  gcc -Wl,-no-as-needed -Wall  seccomp_bpf.c -lpthread -o seccomp_bpf
  gcc -Wl,-no-as-needed -Wall    seccomp_benchmark.c   -o seccomp_benchmark
  
  $ touch tools/testing/selftests/kselftest_harness.h
  
  $ make --no-print-directory -C tools/testing/selftests/ TARGETS=seccomp
  make --no-builtin-rules INSTALL_HDR_PATH=$BUILD/usr \
          ARCH=powerpc -C ../../.. headers_install
    INSTALL /home/michael/build/adhoc/kselftest/usr/include
  gcc -Wl,-no-as-needed -Wall  seccomp_bpf.c -lpthread -o seccomp_bpf
  $

Note that touching the header causes it to rebuild seccomp_bpf.

With this patch applied:

  $ make --no-print-directory -C tools/testing/selftests/ TARGETS=seccomp
  make -s --no-builtin-rules INSTALL_HDR_PATH=$BUILD/usr \
          ARCH=powerpc -C ../../.. headers_install
  gcc -Wl,-no-as-needed -Wall  -lpthread  seccomp_bpf.c  -o /home/michael/build/adhoc/kselftest/seccomp/seccomp_bpf
  gcc -Wl,-no-as-needed -Wall  -lpthread  seccomp_benchmark.c  -o /home/michael/build/adhoc/kselftest/seccomp/seccomp_benchmark
  
  $ touch tools/testing/selftests/kselftest_harness.h
  
  $ make --no-print-directory -C tools/testing/selftests/ TARGETS=seccomp
  make -s --no-builtin-rules INSTALL_HDR_PATH=$BUILD/usr \
          ARCH=powerpc -C ../../.. headers_install
  make[1]: Nothing to be done for 'all'.
  $


So yeah it still needs:

seccomp_bpf: ../kselftest_harness.h


cheers