[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <AANLkTilAeLC6SZVPpy4upQsyoeN0SpqbJ3lwrYPU00I5@mail.gmail.com>
Date: Fri, 4 Jun 2010 19:00:19 -0400
From: Mike Frysinger <vapier.adi@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: David Howells <dhowells@...hat.com>, uclinux-dev@...inux.org,
linux-kernel@...r.kernel.org,
uclinux-dist-devel@...ckfin.uclinux.org,
torvalds@...ux-foundation.org
Subject: Re: [Uclinux-dist-devel] [PATCH] NOMMU: Add '[stack]' label to
/proc/pid/maps output
On Fri, Jun 4, 2010 at 16:48, Andrew Morton wrote:
> On Tue, 01 Jun 2010 19:59:37 +0100 David Howells wrote:
>> From: Mike Frysinger <vapier@...too.org>
>>
>> Add support to the NOMMU /proc/pid/maps file to show which mapping is the stack
>> of the original thread after execve. This is largely based on the MMU code.
>> Subsidiary thread stacks are not indicated.
>>
>> For FDPIC, we now get:
>>
>> root:/> cat /proc/self/maps
>> 02064000-02067ccc rw-p 0004d000 00:01 22 /bin/busybox
>> 0206e000-0206f35c rw-p 00006000 00:01 295 /lib/ld-uClibc.so.0
>> 025f0000-025f6f0c r-xs 00000000 00:01 295 /lib/ld-uClibc.so.0
>> 02680000-026ba6b0 r-xs 00000000 00:01 297 /lib/libc.so.0
>> 02700000-0274d384 r-xs 00000000 00:01 22 /bin/busybox
>> 02816000-02817000 rw-p 00000000 00:00 0
>> 02848000-0284c0d8 rw-p 00000000 00:00 0
>> 02860000-02880000 rw-p 00000000 00:00 0 [stack]
>>
>> The semi-downside here is that for FLAT, we get:
>>
>> root:/> cat /proc/155/maps
>> 029f0000-029f9000 rwxp 00000000 00:00 0 [stack]
>>
>> The reason being that FLAT combines a whole lot of stuff into one map
>> (including the stack). But this isn't any worse than the current output (which
>> is nothing), so screw it.
>
> So it's a non-back-compatible change which can a) break nommu-only
> userspace and b) unbreak mmu-tested userspace which gets run on nommu.
i dont see how it breaks anything really. any code that parses the
maps file has to account for an optional label in the maps output.
i guess if someone wrote some code that does something special with
"[stack]", then behavior would change with FLAT files, but that's
pretty unlikely i would think. plus, FLAT is not ELF and as such, its
layout in memory is highly unlike any existing ELF layout. so someone
would already have to be writing a custom handler for FLAT files which
means they account for the "one blob is everything" layout.
-mike
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists