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From: David Howells <dhowells@redhat.com>
In-Reply-To: <1260921350-6539-1-git-send-email-vapier@gentoo.org>
References: <1260921350-6539-1-git-send-email-vapier@gentoo.org>
To: Mike Frysinger <vapier@gentoo.org>
Cc: dhowells@redhat.com, uclinux-dev@uclinux.org,
       David McCullough <davidm@snapgear.com>, Greg Ungerer <gerg@uclinux.org>,
       Paul Mundt <lethal@linux-sh.org>,
       uclinux-dist-devel@blackfin.uclinux.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] NOMMU: add [stack] label to per-process maps output
Date: Wed, 16 Dec 2009 08:54:22 +0000
Message-ID: <22709.1260953662@redhat.com>
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Mike Frysinger <vapier@gentoo.org> wrote:

> it'd be cool if the global /proc/maps could display something like
> [stack/<pid>], but i can't quite divine how to get a mm_struct out
> of a vm_region without having to walk the entire process list.

Tricky.  vm_regions can be shared between multiple mm_structs, although in the
case of the stack, they're probably not.  Furthermore, there's no interface to
mmap() to say the region you're allocating belongs to a particular PID (and
with userspace created threads, you have to create the stack _before_ calling
clone()).

That said, you could add a 'creator pid' to the vm_region.  This could be set
firstly by mmap() to current->pid, and then overridden by clone() for the
stack VMA.  It would be approximate, but probably a good approximation.  You
probably don't actually need a back pointer, just an integer PID.

David
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