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Message-ID: <ed5aea430602211955k225698c9w35ac02eae071a0c5@mail.gmail.com>
Date: Tue, 21 Feb 2006 20:55:15 -0700
From: David Mosberger-Tang <David.Mosberger@acm.org>
To: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Subject: Re: IA64 non-contiguous memory space bugs
Cc: David Gibson <david@gibson.dropbear.id.au>, linux-ia64@vger.kernel.org,
       linux-kernel@vger.kernel.org
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I'm only following this superficially, but keep in mind that a vm-area
MUST NEVER cross a hole.

  --david

On 2/21/06, Chen, Kenneth W <kenneth.w.chen@intel.com> wrote:
> David Gibson wrote on Tuesday, February 21, 2006 4:14 PM
> > First bug (confirmed many months ago by Chris Wedgwood) - you can get
> > weird effects if you attempt to mmap() something into one of the
> > address space gaps.  The ia64 outer wrapper for mmap2() tries to
> > prevent it, but doesn't do a good enough job, it's still possible
> > indirectly with shmat() and maybe mremap().  Basic trouble is that
> > most of the checks applied by the generic code assume that everything
> > between 0 and TASK_SIZE is valid.
>
> Ha ha ha.
>
> On ia64, the low level tlb fault handler (vhpt_miss and nested_dtlb_miss)
> checks that all unused address bits (between REGION_NUMBER and PGDIR_SHIFT)
> should be all zero.  If they are not zero, it will fall into page fault
> handler and in there, ia64 should just send SEGV instead of happily hand
> over a page.  Buggy buggy....
>
> - Ken
>
> -
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--
Mosberger Consulting LLC, http://www.mosberger-consulting.com/
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