Message-Id: <200602220253.k1M2rWg10346@unix-os.sc.intel.com>
From: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
To: "'David Gibson'" <david@gibson.dropbear.id.au>,
       <linux-ia64@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: RE: IA64 non-contiguous memory space bugs
Date: Tue, 21 Feb 2006 18:53:32 -0800
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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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