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

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Date:	Sun, 22 May 2016 08:43:53 +0300
From:	Dmitry Safonov <0x7f454c46@...il.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Dmitry Safonov <dsafonov@...tuozzo.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Shuah Khan <shuahkh@....samsung.com>,
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCHv9 2/2] selftest/x86: add mremap vdso test

2016-05-21 23:27 GMT+03:00 Ingo Molnar <mingo@...nel.org>:
>
> * Andy Lutomirski <luto@...capital.net> wrote:
>
>> On Thu, May 19, 2016 at 11:48 PM, Ingo Molnar <mingo@...nel.org> wrote:
>> >
>> > * Dmitry Safonov <dsafonov@...tuozzo.com> wrote:
>> >
>> >> Should print on success:
>> >> [root@...alhost ~]# ./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@...alhost ~]# ./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.
>
> Indeed, you are right - I somehow mis-read it as potentially segfaulting on fixed
> kernels as well...
>
> Will look at applying this after the merge window.

Great! Thanks, Ingo - maybe I should have wrote test's patch description better.
Thanks again, Andy.