Re: [PATCH v7 04/12] x86: relocate_kernel - Adapt assembly for PIE support

[Kees Cook]

On Mon, May 20, 2019 at 04:19:29PM -0700, Thomas Garnier wrote:
> From: Thomas Garnier <thgarnie@xxxxxxxxxx>
> 
> Change the assembly code to use only absolute references of symbols for the
> kernel to be PIE compatible.
> 
> Position Independent Executable (PIE) support will allow to extend the
> KASLR randomization range below 0xffffffff80000000.
> 
> Signed-off-by: Thomas Garnier <thgarnie@xxxxxxxxxx>

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees

> ---
>  arch/x86/kernel/relocate_kernel_64.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
> index 11eda21eb697..3320368b6ec9 100644
> --- a/arch/x86/kernel/relocate_kernel_64.S
> +++ b/arch/x86/kernel/relocate_kernel_64.S
> @@ -208,7 +208,7 @@ identity_mapped:
>  	movq	%rax, %cr3
>  	lea	PAGE_SIZE(%r8), %rsp
>  	call	swap_pages
> -	movq	$virtual_mapped, %rax
> +	movabsq	$virtual_mapped, %rax
>  	pushq	%rax
>  	ret
>  
> -- 
> 2.21.0.1020.gf2820cf01a-goog
> 

-- 
Kees Cook