[PATCHv2 1/2] arm: Correct virt_addr_valid

[Will Deacon]

On Mon, Dec 16, 2013 at 07:01:44PM +0000, Laura Abbott wrote:
> The definition of virt_addr_valid is that virt_addr_valid should
> return true if and only if virt_to_page returns a valid pointer.
> The current definition of virt_addr_valid only checks against the
> virtual address range. There's no guarantee that just because a
> virtual address falls bewteen PAGE_OFFSET and high_memory the
> associated physical memory has a valid backing struct page. Follow
> the example of other architectures and convert to pfn_valid to
> verify that the virtual address is actually valid. The check for
> an address between PAGE_OFFSET and high_memory is still necessary
> as vmalloc/highmem addresses are not valid with virt_to_page.
> 
> Cc: Russell King <linux at arm.linux.org.uk>
> Cc: Will Deacon <will.deacon at arm.com>
> Cc: Nicolas Pitre <nico at linaro.org>
> Signed-off-by: Laura Abbott <lauraa at codeaurora.org>
> ---
>  arch/arm/include/asm/memory.h |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
> index 9ecccc8..6211df0 100644
> --- a/arch/arm/include/asm/memory.h
> +++ b/arch/arm/include/asm/memory.h
> @@ -350,7 +350,8 @@ static inline __deprecated void *bus_to_virt(unsigned long x)
>  #define ARCH_PFN_OFFSET		PHYS_PFN_OFFSET
>  
>  #define virt_to_page(kaddr)	pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
> -#define virt_addr_valid(kaddr)	((unsigned long)(kaddr) >= PAGE_OFFSET && (unsigned long)(kaddr) < (unsigned long)high_memory)
> +#define virt_addr_valid(kaddr)	(pfn_valid(__pa(kaddr) >> PAGE_SHIFT) && \
> +	((unsigned long)(kaddr) >= PAGE_OFFSET && (unsigned long)(kaddr) < (unsigned long)high_memory))

Can you change the order of the check please, so that we do the quicker
lowmem range checks before the pfn_valid check? I know I backed down on the
latter being slow, but it's still slower than what we had before and
changing the order of the conjunction is easy to do.

Cheers,

Will