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Date: Fri, 7 Nov 2008 01:16:59 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Alexey Dobriyan <adobriyan@gmail.com>, Ken Chen <kenchen@google.com>,
       linux-kernel@vger.kernel.org, Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [patch] add /proc/pid/stack to dump task's stack trace
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On Fri, 7 Nov 2008 10:03:04 +0100 Ingo Molnar <mingo@elte.hu> wrote:

> task running on this CPU:
> 
>  # cat /proc/self/stack
>  [<ffffffff80216f79>] save_stack_trace_tsk+0x26/0x44
>  [<ffffffff802f59a5>] proc_pid_stack+0x6e/0xd3
>  [<ffffffff802f6da3>] proc_info_read+0x68/0xba
>  [<ffffffff802b2f17>] vfs_read+0xa9/0xe3
>  [<ffffffff802b301f>] sys_read+0x4c/0x73
>  [<ffffffff8020c23b>] system_call_fastpath+0x16/0x1b
>  [<ffffffffffffffff>] 0xffffffffffffffff

So we provide a means by which process A can sample process B's
instruction pointer?  Even if it's in random.c or crypto code?  There's
a little project for someone.

I guess the 0400 mode on that file will suffice...

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