what's zero_pages for in paging_int

[Russell King - ARM Linux]

On Fri, Oct 30, 2009 at 11:18:13AM +0800, 胡杨树 wrote:
>      In paging_int, after setting up bootmem allocator, why zero page
> is needed? i cannot see any things usefull resides on that page,
> something i missing obviously?

Please don't post extracts of code which are part of mainline kernels.
Just provide a reference to where they are.  Most people who will reply
to you already have a copy of the kernel source.

The zero page is a page full of zeros, and is used to provide userspace
with a write-protected initial BSS segment.  When userspace first writes
to the BSS segments, a page fault happens, and a replacement writable
zero page will be given to the program.