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

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Date:	Fri, 20 May 2016 08:48:20 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Dmitry Safonov <dsafonov@...tuozzo.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...hat.com,
	luto@...capital.net, tglx@...utronix.de, hpa@...or.com,
	x86@...nel.org, akpm@...ux-foundation.org, linux-mm@...ck.org,
	0x7f454c46@...il.com, Shuah Khan <shuahkh@....samsung.com>,
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCHv9 2/2] selftest/x86: add mremap vdso test

* 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 ...

Thanks,

	Ingo