linux-kernel - Re: [tip:sched/core 7/28] rseq.c:139:37: error: 'AT_RSEQ_ALIGN' undeclared; did you mean 'R_SH

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Message-ID: <37625f31-6ac2-1f90-d864-e4644820bba3@efficios.com>
Date:   Tue, 17 Jan 2023 12:44:17 -0500
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Ingo Molnar <mingo@...nel.org>,
        Shuah Khan <skhan@...uxfoundation.org>
Cc:     kernel test robot <lkp@...el.com>, Shuah Khan <shuah@...nel.org>,
        oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
        x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        linux-kselftest@...r.kernel.org
Subject: Re: [tip:sched/core 7/28] rseq.c:139:37: error: 'AT_RSEQ_ALIGN'
 undeclared; did you mean 'R_SH_ALIGN'?

On 2023-01-17 04:06, Ingo Molnar wrote:
> 
> * Shuah Khan <skhan@...uxfoundation.org> wrote:
> 
>> On 1/16/23 13:18, Mathieu Desnoyers wrote:
>>> On 2023-01-16 14:40, kernel test robot wrote:
>>>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched/core
>>>> head:   79ba1e607d68178db7d3fe4f6a4aa38f06805e7b
>>>> commit: 03f5c0272d1b59343144e199becc911dae52c37e [7/28] selftests/rseq: Use ELF auxiliary vector for extensible rseq
>>>> compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
>>>> reproduce:
>>>>           # https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=03f5c0272d1b59343144e199becc911dae52c37e
>>>>           git remote add tip https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
>>>>           git fetch --no-tags tip sched/core
>>>>           git checkout 03f5c0272d1b59343144e199becc911dae52c37e
>>>>           make O=/tmp/kselftest headers
>>>>           make O=/tmp/kselftest -C tools/testing/selftests
>>>>
>>>> If you fix the issue, kindly add following tag where applicable
>>>> | Reported-by: kernel test robot <lkp@...el.com>
>>>
>>> In order to fix this, I need to change -I../../../../usr/include/ for $(KHDR_INCLUDES) in tools/testing/selftests/rseq/Makefile
>>>
>>> I can find 25 odd uses of the same pattern in the kernel selftests. Should I fix them all in one go ?
>>
>> kselftest build depends on headers installed in the root directory.

By "root directory", do you mean kernel sources root directory or build 
output root directory ?

>> The main makefile enforces this dependency.

How ? I figure that tools/testing/selftests/lib.mk overrides 
KHDR_INCLUDES if it is not defined yet:

ifeq ($(KHDR_INCLUDES),)
KHDR_INCLUDES := -isystem $(top_srcdir)/usr/include
endif

and selftests makefiles include ../lib.mk.

This KHDR_INCLUDES can be modified by O=... when built from the kernel 
top level, thus using tools/testing/selftests/Makefile:

ifneq ($(KBUILD_OUTPUT),)
[...]
   KHDR_INCLUDES := -isystem ${abs_objtree}/usr/include
else
[...]
   KHDR_INCLUDES := -isystem ${abs_srctree}/usr/include
endif

But it's up to the individual selftests to actually use 
$(KHDR_INCLUDES). In many cases, they hardcode 
-I../../../../usr/include/ which is bogus when the build root (O=...) 
differs from the source root.

  If this test is being
>> built without installing headers by itself, I think the scripts that
>> build individual tests have to makes sure headers are installed first.

The headers were previously built by "make O=/tmp/kselftest headers", as 
it should, it's just that the selftest makefile uses a hardcoded path 
that is relative to the source directory, and it appears that this 
pattern is repeated all across the selftests.

> 
> Why isn't the Makefile saying anything about it & enforcing it? self-tests
> are usually self-sufficient to build in the individual directories.

In an ideal world, we'd have a way to _remove_ the build environment 
kernel headers from the include search paths, because this is a problem 
for reproducibility of the tests.

Thanks,

Mathieu

> 
> Thanks,
> 
> 	Ingo

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com