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From: Ingo Molnar <mingo@kernel.org>
To: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: linux-kernel@vger.kernel.org, mingo@redhat.com,
	luto@amacapital.net, tglx@linutronix.de, hpa@zytor.com,
	x86@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org,
	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
Date: Fri, 17 Jun 2016 10:03:46 +0200	[thread overview]
Message-ID: <20160617080346.GB30525@gmail.com> (raw)
In-Reply-To: <1463487232-4377-3-git-send-email-dsafonov@virtuozzo.com>


* 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)

Yeah, so I changed my mind again, I still don't like that the testcase faults on 
old kernels:

 triton:~/tip/tools/testing/selftests/x86> ./test_mremap_vdso_32 
         AT_SYSINFO_EHDR is 0xf7786000
 [NOTE]  Moving vDSO: [0xf7786000, 0xf7787000] -> [0xf7781000, 0xf7782000]
 Segmentation fault

How do I know that this testcase is special and that a segmentation fault in this 
case means that I'm running it on a too old kernel and that it's not some other 
unexpected failure in the test?

At minimum please run it behind fork() and catch the -SIGSEGV child exit:

  mremap(0xf7747000, 4096, 4096, MREMAP_MAYMOVE|MREMAP_FIXED, 0xf7742000) = 0xf7742000
  --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0xf7747be9} ---
  +++ killed by SIGSEGV +++

and print:

  [FAIL] mremap() of the vDSO does not work on this kernel!

or such.

Ok?

Thanks,

	Ingo

WARNING: multiple messages have this Message-ID (diff)
From: Ingo Molnar <mingo@kernel.org>
To: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: linux-kernel@vger.kernel.org, mingo@redhat.com,
	luto@amacapital.net, tglx@linutronix.de, hpa@zytor.com,
	x86@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org,
	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
Date: Fri, 17 Jun 2016 10:03:46 +0200	[thread overview]
Message-ID: <20160617080346.GB30525@gmail.com> (raw)
In-Reply-To: <1463487232-4377-3-git-send-email-dsafonov@virtuozzo.com>


* 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)

Yeah, so I changed my mind again, I still don't like that the testcase faults on 
old kernels:

 triton:~/tip/tools/testing/selftests/x86> ./test_mremap_vdso_32 
         AT_SYSINFO_EHDR is 0xf7786000
 [NOTE]  Moving vDSO: [0xf7786000, 0xf7787000] -> [0xf7781000, 0xf7782000]
 Segmentation fault

How do I know that this testcase is special and that a segmentation fault in this 
case means that I'm running it on a too old kernel and that it's not some other 
unexpected failure in the test?

At minimum please run it behind fork() and catch the -SIGSEGV child exit:

  mremap(0xf7747000, 4096, 4096, MREMAP_MAYMOVE|MREMAP_FIXED, 0xf7742000) = 0xf7742000
  --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0xf7747be9} ---
  +++ killed by SIGSEGV +++

and print:

  [FAIL] mremap() of the vDSO does not work on this kernel!

or such.

Ok?

Thanks,

	Ingo

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  parent reply	other threads:[~2016-06-17  8:03 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-17 12:13 [PATCHv9 0/2] mremap vDSO for 32-bit Dmitry Safonov
2016-05-17 12:13 ` Dmitry Safonov
2016-05-17 12:13 ` [PATCHv9 1/2] x86/vdso: add mremap hook to vm_special_mapping Dmitry Safonov
2016-05-17 12:13   ` Dmitry Safonov
2016-05-17 12:13 ` [PATCHv9 2/2] selftest/x86: add mremap vdso test Dmitry Safonov
2016-05-17 12:13   ` Dmitry Safonov
2016-05-20  6:48   ` Ingo Molnar
2016-05-20  6:48     ` Ingo Molnar
2016-05-20 15:33     ` Andy Lutomirski
2016-05-20 15:33       ` Andy Lutomirski
2016-05-21 20:27       ` Ingo Molnar
2016-05-21 20:27         ` Ingo Molnar
2016-05-22  5:43         ` Dmitry Safonov
2016-05-22  5:43           ` Dmitry Safonov
2016-06-08 11:41         ` Dmitry Safonov
2016-06-08 11:41           ` Dmitry Safonov
2016-06-17  8:03   ` Ingo Molnar [this message]
2016-06-17  8:03     ` Ingo Molnar
2016-06-17  9:24     ` Dmitry Safonov
2016-06-17  9:24       ` Dmitry Safonov
2016-05-19  9:50 ` [PATCHv9 0/2] mremap vDSO for 32-bit Dmitry Safonov
2016-05-19  9:50   ` Dmitry Safonov

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