Re: Crash while mapping memory in pagetable_init() (Was: Re: .config)

Chris Wright
2007-04-14T00:10:53Z

* Jeremy Fitzhardinge (jeremy@goop.org) wrote:
> Subject: i386: map enough initial memory to create lowmem mappings
>
> head.S creates the very initial pagetable for the kernel. This just
> maps enough space for the kernel itself, and an allocation bitmap.
> The amount of mapped memory is rounded up to 4Mbytes, and so this
> typically ends up mapping 8Mbytes of memory.
>
> When booting, pagetable_init() needs to create mappings for all
> lowmem, and the pagetables for these mappings are allocated from the
> free pages around the kernel in low memory. If the number of
> pagetable pages + kernel size exceeds head.S's initial mapping, it
> will end up faulting on an unmapped page. This will only happen with
> specific combinations of kernel size and memory size.
>
> This patch makes sure that head.S also maps enough space to fit the
> kernel pagetables as well as the kernel itself. It ends up using an
> additional two pages of unreclaimable memory.

Yup, fixes it up here, nice catch.

Acked-by: Chris Wright <chrisw@sous-sol.org>