From: "Chris Friesen" <cfriesen@nortel•com>
To: Anton Blanchard <anton@samba•org>
Cc: linuxppc-dev@ozlabs•org
Subject: Re: what is ~1MB of memory allocated at fffea000-fffff000 on ppc64?
Date: Mon, 27 Aug 2007 16:05:18 -0600 [thread overview]
Message-ID: <46D34A9E.7010501@nortel.com> (raw)
In-Reply-To: <20070827203157.GD13612@kryten>
Anton Blanchard wrote:
> Hi,
>
>
>>I've got a ppc64 box running 2.6.14. 64-bit kernel, 32-bit userspace.
>>It has a ~86KB chunk of memory near the top of the process address
>>space, and I'm not sure who's setting it up and what the purpose is. In
>>/proc/<pid>/maps it looks like this:
>>
>>fffea000-fffff000 rw-p fffea000 00:00 0
>>
>>Can anyone enlighten me as to what this is for and who is allocating it?
>
>
> Looks like your process stack. BTW we leave the top page
> (0xfffff000 - 0xffffffff) unmapped mostly because of test cases that
> expect
>
> *(unsigned long *)-1UL
>
> to fail.
Doh. Of course, that's almost certainly it.
For some background, we're running an emulator that uses a null pointer
value of 0xffff0000 and we want any accesses to that address to trap.
Do you anticipate any issues with the following change?
-#define TASK_SIZE_USER32 (0x0000000100000000UL - (1*PAGE_SIZE))
+#define TASK_SIZE_USER32 (0x00000000FFFF0000UL - (1*PAGE_SIZE))
Thanks,
Chris
next prev parent reply other threads:[~2007-08-27 22:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-27 20:22 what is ~1MB of memory allocated at fffea000-fffff000 on ppc64? Chris Friesen
2007-08-27 20:31 ` Anton Blanchard
2007-08-27 22:05 ` Chris Friesen [this message]
2007-08-27 23:19 ` Anton Blanchard
2007-08-28 5:19 ` Paul Mackerras
2007-08-28 15:15 ` Chris Friesen
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