linux-kernel - Re: [BUG] perf and kmemcheck : fatal combination

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Message-ID: <1303823384.3358.53.camel@edumazet-laptop>
Date:	Tue, 26 Apr 2011 15:09:44 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Pekka Enberg <penberg@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Paul Mackerras <paulus@...ba.org>,
	Vegard Nossum <vegardno@....uio.no>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [BUG] perf and kmemcheck : fatal combination

Le mardi 26 avril 2011 à 14:56 +0200, Eric Dumazet a écrit :
> Le mardi 26 avril 2011 à 14:33 +0200, Peter Zijlstra a écrit :
> > On Tue, 2011-04-26 at 14:27 +0200, Eric Dumazet wrote:
> > > Thats far from trivial, maybe because we dont have NOTRACK api for
> > > percpu allocations ? 
> > 
> > We can't use per-cpu allocations from NMI context because of the same
> > problem, per-cpu uses vmalloc and vmalloc needs faults. Hence that
> > shouldn't be a problem.
> > 
> > It looks like you covered most of it though, the buffer and the
> > callchain stuff, aside from that it should only use some static data.
> > 
> > Pekka, what does kmemcheck do for .data and .bss things?
> 
> Hmm, maybe I have a problem because of the WARN_ON in kmemcheck and my
> boot had "log_buf_len=32M", so kmemcheck was called again
> 
> 
> I am now trying to remve the line 634 from
> arch/x86/mm/kmemcheck/kmemcheck.c

Yes, its making some progress

[  328.696312] BUG: unable to handle kernel 
[  328.697078] kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
[  328.698284] BUG: unable to handle kernel paging request at ffff88011fc07b58
[  328.699569] IP: [<ffff88011fc07968>] 0xffff88011fc07967
[  328.700488] PGD 1a94063 PUD 11f6f9067 PMD 11f7f8067 PTE 800000011fc07163
[  328.702327] Oops: 0011 [#1] PREEMPT SMP 
[  328.703693] last sysfs file: /sys/devices/system/cpu/online
[  328.704361] CPU 0 
[  328.704777] Modules linked in: nfsd lockd auth_rpcgss sunrpc tg3 libphy sg [last unloaded: x_tables]
[  328.708693] 
[  328.709075] Pid: 4019, comm: perf Not tainted 2.6.39-rc4-00369-g23cf772-dirty #562 HP ProLiant BL460c G6
[  328.710581] RIP: 3c4c:[<ffff88011fc07968>]  [<ffff88011fc07968>] 0xffff88011fc07967
[  328.711692] RSP: 0000:ffff88011b3cbfd8  EFLAGS: ffff88011fc0793c
[  328.712388] RAX: ffff88011b3ca000 RBX: ffff88011fc07ff8 RCX: ffff88011fc07158
[  328.713180] RDX: ffff88011fc03fc0 RSI: ffff88011fc00000 RDI: ffff88011fc07158
[  328.713959] RBP: ffff88011fc07888 R08: ffffffff81601680 R09: ffff880114278400
[  328.714738] R10: ffffffff81004ed3 R11: ffff88011fc078d8 R12: ffffffff8105eb99
[  328.715516] R13: ffff88011fc07888 R14: 0000000000000018 R15: ffff880112638238
[  328.716294] FS:  0000000000000000(0000) GS:ffff88011fc00000(0063) knlGS:00000000f77176c0


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