Re: [PATCH: x86] Add dma_mmap_coherent()

[Russell King <rmk@arm.linux.org.uk>]

On Sun, Mar 28, 2004 at 11:22:16AM +0100, Russell King wrote:
> This has only been compile tested.  There are two changes here:
> 
> 1. ensure that we zero the whole page - otherwise we may expose leak
>    kernel data to userspace in the remainder of the last page.
> 2. add dma_mmap_coherent().  I've added checks for the offset and
>    size to ensure that we don't do anything silly (like mapping more
>    memory than the original coherent allocation covered.)  Maybe this
>    is something that remap_page_range() should be doing anyway?

Actually, there is a problem with this patch as it stands - get_free_pages
returns kernel pages, and remap_page_range() won't touch them without
the pages being marked reserved.  I'm also led to believe that splitting
a struct page up into is constituent struct pages is no longer valid, so
exactly how we do that is open to question.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 PCMCIA      - http://pcmcia.arm.linux.org.uk/
                 2.6 Serial core