linux-kernel - Re: Ambigiuous thread stack annotation in /proc/pid/[s]maps

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Date:	Wed, 26 Jun 2013 22:05:41 +0530
From:	Siddhesh Poyarekar <siddhesh.poyarekar@...il.com>
To:	Jan Glauber <jan.glauber@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Ambigiuous thread stack annotation in /proc/pid/[s]maps

On 26 June 2013 17:13, Jan Glauber <jan.glauber@...il.com> wrote:
> Any ideas how that can be fixed? The only solution that comes to my mind
> is to prevent merging vma's that are used for thread stacks. There is already a
> flag (MAP_STACK) which is set by the libc for mmap'ing thread stacks but the
> kernel currently does not care. If the kernel gets an mmap request with
> MAP_STACK set we could mark the VMA and avoid merging it with others.
>
> Unfortunately there seems to be no bit left in the vm_flags to store the
> MAP_STACK information...

The annotations essentially point out that the vma contains the stack
and not that the vma *is* the stack.  We'd get similar output with
makecontext/getcontext, where the stack may just be a portion of
memory in another vma.  I don't remember if I had explicitly mentioned
that during the original discussion.

Siddhesh
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http://siddhesh.in
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