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Subject: Re: 1352 NUL bytes at the end of a page?
From: Steven Cole <scole@lanl.gov>
To: viro@parcelfarce.linux.theplanet.co.uk
Cc: hugh@veritas.com, linux-kernel@vger.kernel.org, support@bitmover.com,
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Date: Mon, 17 May 2004 11:39:58 -0600
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On Mon, 2004-05-17 at 11:40, viro@parcelfarce.linux.theplanet.co.uk
wrote:
> On Mon, May 17, 2004 at 11:30:36AM -0600, Steven Cole wrote:
>  
> > mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 
> > 0) = 0x40018000
> 
> rw anonymous - that has nothing to do with any IO.
> 
> > old_mmap(NULL, 19184, PROT_READ, MAP_PRIVATE, 3, 0) = 0x40018000
> 
> read-only, whatever file that was.
> 
> Was there anything with PROT_WRITE and without MAP_ANONYMOUS?

Yes, seven of the 52 references to mmap in the strace output met
the above criteria: 

  old_mmap(0x4015f000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x142000) = 0x4015f000
  old_mmap(0x40170000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x9000) = 0x40170000
  old_mmap(0x40180000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 4, 0x9000) = 0x40180000
  old_mmap(0x40191000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 4, 0x10000) = 0x40191000
  old_mmap(0x4019c000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 4, 0x7000) = 0x4019c000
  old_mmap(0x401a0000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 4, 0x3000) = 0x401a0000
  old_mmap(0x401af000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 4, 0xe000) = 0x401af000


Steven