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

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Message-ID: <85ce71dc-e7f8-74ed-f495-dcb46255908a@linuxfoundation.org>
Date:   Fri, 13 Mar 2020 17:38:06 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     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, mpe@...erman.id.au,
        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 v3] selftests: Fix seccomp to support relocatable build
 (O=objdir)

On 3/13/20 5:18 PM, Kees Cook wrote:
> 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?

make in seccomp directory won't work. lib.mk won't build it.
One reason why I wanted to clearly call this out as CUSTOM
program.

But it does make sense to reduce additional EXTRA_CLEAN by
just using TEST_GEN_PROGS.
> 
> I think if those are removed it should all still work? Regardless:
> 
diff Makefile
diff --git a/tools/testing/selftests/seccomp/Makefile 
b/tools/testing/selftests/seccomp/Makefile
index a0388fd2c3f2..d3d256654cb1 100644
--- a/tools/testing/selftests/seccomp/Makefile
+++ b/tools/testing/selftests/seccomp/Makefile
@@ -2,7 +2,7 @@
  CFLAGS += -Wl,-no-as-needed -Wall
  LDFLAGS += -lpthread

-.PHONY: all clean
+#.PHONY: all clean

  include ../lib.mk

@@ -11,5 +11,5 @@ TEST_GEN_PROGS := $(OUTPUT)/seccomp_bpf 
$(OUTPUT)/seccomp_benchmark

  $(TEST_GEN_PROGS): ../kselftest_harness.h

-all: $(TEST_GEN_PROGS)
+#$all: $(TEST_GEN_PROGS)

With this:

make
make: Nothing to be done for 'all'.

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

I am addressing your comment about other tests that de[end on
kselftest_harness.h. I have a few patches ready to be sent.

thanks,
-- Shuah