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Date: Sat, 21 May 2016 22:27:52 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
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        Andrew Morton <akpm@linux-foundation.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Dmitry Safonov <0x7f454c46@gmail.com>,
        Shuah Khan <shuahkh@osg.samsung.com>, linux-kselftest@vger.kernel.org
Subject: Re: [PATCHv9 2/2] selftest/x86: add mremap vdso test
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* Andy Lutomirski <luto@amacapital.net> wrote:

> 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.

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.

Thanks,

	Ingo