Messages in this thread | | | Subject | RE: return negative number for unsigned long function in kernel | Date | Wed, 7 Mar 2007 08:31:09 -0500 | From | "Chen, Dongliang" <> |
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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.
Dongliang Chen
Staff Engineer EMS Technologies, Inc - Defense & Space Systems 660 Engineering Dr Norcross, GA 30092 Tel: 770-263-9200 x 4379
-----Original Message----- From: H. Peter Anvin [mailto:hpa@zytor.com] Sent: Tuesday, March 06, 2007 7:39 PM To: Chen, Dongliang Cc: linux-kernel@vger.kernel.org Subject: Re: return negative number for unsigned long function in kernel
H. Peter Anvin wrote: >If you want to test for errorness, you could use the macro >IS_ERR_VALUE(). Unfortunately the macro isn't all that safe, in that it >will give you the wrong answer if it's ever used on something that >*isn't* an unsigned long.
-----Original Message----- From: Andreas Schwab [mailto:schwab@suse.de] Sent: Tuesday, March 06, 2007 2:06 PM To: Chen, Dongliang Cc: linux-kernel@vger.kernel.org Subject: Re: return negative number for unsigned long function in kernel
Andreas Schwab wrote: >The return value is directly passed to user space (it's the guts of the >mmap syscall). The glibc wrapper transforms it appropriately so that errno >is set and -1 is returned if there is an error.
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