Re: Question on IS_ERR

["jidong xiao" <jidong.xiao@gmail.com>]

On 8/9/07, H. Peter Anvin <hpa@zytor.com> wrote:
>
> No.  There is no requirement that the pointer is page-aligned.  The last
> page of the address space is (in the Linux kernel) invalid by
> definition, so there are in effect three kinds of pointers in the Linux
> kernel: valid pointers, NULL, and ERR_PTR()s.
>
>        -hpa
>

Regarding "The last page of the address space is invalid by definition",
I am wondering why do we define the last page as invalid.
The reason for defining this is just because we want to take use of
the error number handling?

Regards
Jason
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