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Date: Wed, 07 Mar 2007 08:30:47 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: "Chen, Dongliang" <Chen.D@ems-t.com>
CC: Andreas Schwab <schwab@suse.de>, linux-kernel@vger.kernel.org
Subject: Re: return negative number for unsigned long function in kernel
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Chen, Dongliang wrote:
> Peter & Andreas,
> 
> Thank you very much for your help. 
> 
> I understood that the kernel error numbers are limited. The largest
> error number for i386 (kernel 2.6) is 131 so far.  Assume that the
> virtual address returned from do_mmap_pgoff will never exceed (unsigned
> long)(-1000L), which is in the address range one page below the maximum
> virtual address, then IS_ERR_VALUE() should work.
> 

The error value boundary is defined in <linux/err.h>, currently 4095.

	-hpa