[PATCH v2 2/2] ARM: memory: define TASK_UNMAPPED_BASE in terms of TASK_SIZE

[Nicolas Pitre]

On Thu, 31 Jan 2013, Will Deacon wrote:

> TASK_UNMAPPED_BASE is defined directly in terms of PAGE_OFFSET, which is
> confusing given that the modules area sits between here and TASK_SIZE
> and is not available for user allocations.
> 
> This patch defines TASK_UNMAPPED_BASE in terms of TASK_SIZE instead and
> fixes a bug introduced by 394ef6403abc ("mm: use vm_unmapped_area() on
> arm architecture") whereby TASK_UNMAPPED_BASE is no longer page-aligned
> for bottom-up mmap, causing get_unmapped_area to choke on misaligned
> addresses.
> 
> Reported-by: Christoffer Dall <cdall at cs.columbia.edu>
> Signed-off-by: Will Deacon <will.deacon at arm.com>

Acked-by: Nicolas Pitre <nico at linaro.org>


> ---
>  arch/arm/include/asm/memory.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
> index 924320f..64c770d 100644
> --- a/arch/arm/include/asm/memory.h
> +++ b/arch/arm/include/asm/memory.h
> @@ -37,7 +37,7 @@
>   */
>  #define PAGE_OFFSET		UL(CONFIG_PAGE_OFFSET)
>  #define TASK_SIZE		(UL(CONFIG_PAGE_OFFSET) - UL(SZ_16M))
> -#define TASK_UNMAPPED_BASE	(UL(CONFIG_PAGE_OFFSET) / 3)
> +#define TASK_UNMAPPED_BASE	ALIGN(TASK_SIZE / 3, SZ_16M)
>  
>  /*
>   * The maximum size of a 26-bit user space task.
> -- 
> 1.8.0
>