linux-kernel - Re: [PATCH] selftests/landlock: fix broken include of linux/landlock.h

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Date:   Thu, 4 Aug 2022 21:38:34 +0200
From:   Guillaume Tucker <guillaume.tucker@...labora.com>
To:     Mickaël Salaün <mic@...ikod.net>,
        Shuah Khan <shuah@...nel.org>
Cc:     Anders Roxell <anders.roxell@...aro.org>, Tim.Bird@...y.com,
        kernel@...labora.com, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: Re: [PATCH] selftests/landlock: fix broken include of
 linux/landlock.h

On 04/08/2022 12:36, Mickaël Salaün wrote:
> 
> On 03/08/2022 22:13, Guillaume Tucker wrote:
>> Revert part of the earlier changes to fix the kselftest build when
>> using a sub-directory from the top of the tree as this broke the
>> landlock test build as a side-effect when building with "make -C
>> tools/testing/selftests/landlock".
>>
>> Reported-by: Mickaël Salaün <mic@...ikod.net>
>> Fixes: a917dd94b832 ("selftests/landlock: drop deprecated headers dependency")
>> Fixes: f2745dc0ba3d ("selftests: stop using KSFT_KHDR_INSTALL")
>> Signed-off-by: Guillaume Tucker <guillaume.tucker@...labora.com>
>> ---
>>   tools/testing/selftests/landlock/Makefile | 7 +++++--
>>   1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/testing/selftests/landlock/Makefile b/tools/testing/selftests/landlock/Makefile
>> index a6959df28eb0..02868ac3bc71 100644
>> --- a/tools/testing/selftests/landlock/Makefile
>> +++ b/tools/testing/selftests/landlock/Makefile
>> @@ -9,10 +9,13 @@ TEST_GEN_PROGS := $(src_test:.c=)
>>   TEST_GEN_PROGS_EXTENDED := true
>>     OVERRIDE_TARGETS := 1
>> +top_srcdir := ../../../..
> 
> Not sure it changes much, but most other selftests Makefiles use "top_srcdir = ../../../.." (without ":="). Why this change?

I didn't simply apply your diff but edited the file by hand to
test various combinations and see what side effects it might
have.  So when I added top_srcdir I typed it by hand and used :=
as a reflex since it's the standard way of assigning variables.
Using = instead only makes a difference when the r-value has
something dynamic as it will be re-evaluated every time it's
used.  So for constant values, I guess it's more of a question of
coding style and conventions.  Maybe all the top_srcdir variables
should be changed to := but that's unnecessary churn...  Either
way, it's benign.

Shuah, feel free to change this back to = in this particular case
if it's more consistent with other Makefiles.  Consistency is
often better than arbitrary rules.  Or conversely, change to :=
for the khdr_dir definition...  Entirely up to you I think.

Thanks,
Guillaume

>>   include ../lib.mk
>>   +khdr_dir = $(top_srcdir)/usr/include
>> +
>>   $(OUTPUT)/true: true.c
>>       $(LINK.c) $< $(LDLIBS) -o $@ -static
>>   -$(OUTPUT)/%_test: %_test.c ../kselftest_harness.h common.h
>> -    $(LINK.c) $< $(LDLIBS) -o $@ -lcap
>> +$(OUTPUT)/%_test: %_test.c $(khdr_dir)/linux/landlock.h ../kselftest_harness.h common.h
>> +    $(LINK.c) $< $(LDLIBS) -o $@ -lcap -I$(khdr_dir)