Re: [PATCHv9 2/2] selftest/x86: add mremap vdso test

From	Andy Lutomirski <luto@amacapital.net>
Newsgroups	linux.kernel
Subject	Re: [PATCHv9 2/2] selftest/x86: add mremap vdso test
Date	2016-05-20 17:40 +0200
Message-ID	<rAUGR-7fU-11@gated-at.bofh.it> (permalink)
References	<rzMs1-4zK-11@gated-at.bofh.it> <rzMs1-4zK-9@gated-at.bofh.it> <rAMpZ-25Y-45@gated-at.bofh.it>
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On Thu, May 19, 2016 at 11:48 PM, Ingo Molnar <mingo@kernel.org> wrote:
>
> * Dmitry Safonov <dsafonov@virtuozzo.com> wrote:
>
>> Should print on success:
>> [root@localhost ~]# ./test_mremap_vdso_32
>>       AT_SYSINFO_EHDR is 0xf773f000
>> [NOTE]        Moving vDSO: [f773f000, f7740000] -> [a000000, a001000]
>> [OK]
>> Or segfault if landing was bad (before patches):
>> [root@localhost ~]# ./test_mremap_vdso_32
>>       AT_SYSINFO_EHDR is 0xf774f000
>> [NOTE]        Moving vDSO: [f774f000, f7750000] -> [a000000, a001000]
>> Segmentation fault (core dumped)
>
> So I still think that generating potential segfaults is not a proper way to test a
> new feature. How are we supposed to tell the feature still works? I realize that
> glibc is a problem here - but that doesn't really change the QA equation: we are
> adding new kernel code to help essentially a single application out of tens of
> thousands of applications.
>
> At minimum we should have a robust testcase ...

I think it's robust enough.  It will print "[OK]" and exit with 0 on
success and it will crash on failure.  The latter should cause make
run_tests to fail reliably.

There are some test cases in there that can't avoid crashing on
failure unless they were to fork, fail in a child, and then print some
text in the parent.  That seems like it would be more work than it's
worth.

--Andy

Thread

[PATCHv9 2/2] selftest/x86: add mremap vdso test Dmitry Safonov <dsafonov@virtuozzo.com> - 2016-05-17 14:40 +0200
  Re: [PATCHv9 2/2] selftest/x86: add mremap vdso test Ingo Molnar <mingo@kernel.org> - 2016-05-20 08:50 +0200
    Re: [PATCHv9 2/2] selftest/x86: add mremap vdso test Andy Lutomirski <luto@amacapital.net> - 2016-05-20 17:40 +0200
      Re: [PATCHv9 2/2] selftest/x86: add mremap vdso test Ingo Molnar <mingo@kernel.org> - 2016-05-21 22:30 +0200
        Re: [PATCHv9 2/2] selftest/x86: add mremap vdso test Dmitry Safonov <0x7f454c46@gmail.com> - 2016-05-22 07:50 +0200

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