diff mbox series

[boot-wrapper,v2,7/9] pointer auth: Document CPU feature bit mask

Message ID 20211222181607.1203191-8-andre.przywara@arm.com (mailing list archive)
State New, archived
Headers show
Series Various (build system) fixes | expand

Commit Message

Andre Przywara Dec. 22, 2021, 6:16 p.m. UTC
When checking for the pointer authentication feature, we actually look
for *four* different CPUID feature sets.
Add a comment to make it more obvious that the 0xff is not a typo.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
 arch/aarch64/boot.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Mark Rutland Jan. 7, 2022, 2:15 p.m. UTC | #1
On Wed, Dec 22, 2021 at 06:16:05PM +0000, Andre Przywara wrote:
> When checking for the pointer authentication feature, we actually look
> for *four* different CPUID feature sets.
> Add a comment to make it more obvious that the 0xff is not a typo.
> 
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>

Thanks; applied.

Mark.

> ---
>  arch/aarch64/boot.S | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/aarch64/boot.S b/arch/aarch64/boot.S
> index bfbb6ec..27ba449 100644
> --- a/arch/aarch64/boot.S
> +++ b/arch/aarch64/boot.S
> @@ -38,7 +38,8 @@ ASM_FUNC(_start)
>  
>  	/* Enable pointer authentication if present */
>  	mrs	x1, id_aa64isar1_el1
> -	ldr	x2, =(((0xff) << 24) | (0xff << 4))
> +	/* We check for APA+API and GPA+GPI */
> +	ldr	x2, =((0xff << 24) | (0xff << 4))
>  	and	x1, x1, x2
>  	cbz	x1, 1f
>  
> -- 
> 2.25.1
>
diff mbox series

Patch

diff --git a/arch/aarch64/boot.S b/arch/aarch64/boot.S
index bfbb6ec..27ba449 100644
--- a/arch/aarch64/boot.S
+++ b/arch/aarch64/boot.S
@@ -38,7 +38,8 @@  ASM_FUNC(_start)
 
 	/* Enable pointer authentication if present */
 	mrs	x1, id_aa64isar1_el1
-	ldr	x2, =(((0xff) << 24) | (0xff << 4))
+	/* We check for APA+API and GPA+GPI */
+	ldr	x2, =((0xff << 24) | (0xff << 4))
 	and	x1, x1, x2
 	cbz	x1, 1f