[v2,05/29] ARM: head-common.S: use PC-relative insn sequence for idmap creation
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Message ID 20170903120757.14968-6-ard.biesheuvel@linaro.org
State New
Headers show

Commit Message

Ard Biesheuvel Sept. 3, 2017, 12:07 p.m. UTC
Replace the open coded PC relative offset calculations involving
__turn_mmu_on and __turn_mmu_on_end with a pair of adr_l invocations.
This ensures these quantities are invariant under runtime relocation.

Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 arch/arm/kernel/head.S | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

Comments

Nicolas Pitre Sept. 4, 2017, 4:08 p.m. UTC | #1
On Sun, 3 Sep 2017, Ard Biesheuvel wrote:

> Replace the open coded PC relative offset calculations involving
> __turn_mmu_on and __turn_mmu_on_end with a pair of adr_l invocations.
> This ensures these quantities are invariant under runtime relocation.
> 
> Cc: Russell King <linux@armlinux.org.uk>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

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

> ---
>  arch/arm/kernel/head.S | 12 ++----------
>  1 file changed, 2 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
> index 04286fd9e09c..0a98aec0e39d 100644
> --- a/arch/arm/kernel/head.S
> +++ b/arch/arm/kernel/head.S
> @@ -227,11 +227,8 @@ __create_page_tables:
>  	 * Create identity mapping to cater for __enable_mmu.
>  	 * This identity mapping will be removed by paging_init().
>  	 */
> -	adr	r0, __turn_mmu_on_loc
> -	ldmia	r0, {r3, r5, r6}
> -	sub	r0, r0, r3			@ virt->phys offset
> -	add	r5, r5, r0			@ phys __turn_mmu_on
> -	add	r6, r6, r0			@ phys __turn_mmu_on_end
> +	adr_l	r5, __turn_mmu_on		@ _pa(__turn_mmu_on)
> +	adr_l	r6, __turn_mmu_on_end		@ _pa(__turn_mmu_on_end)
>  	mov	r5, r5, lsr #SECTION_SHIFT
>  	mov	r6, r6, lsr #SECTION_SHIFT
>  
> @@ -354,11 +351,6 @@ __create_page_tables:
>  	ret	lr
>  ENDPROC(__create_page_tables)
>  	.ltorg
> -	.align
> -__turn_mmu_on_loc:
> -	.long	.
> -	.long	__turn_mmu_on
> -	.long	__turn_mmu_on_end
>  
>  #if defined(CONFIG_SMP)
>  	.text
> -- 
> 2.11.0
> 
>

Patch
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diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 04286fd9e09c..0a98aec0e39d 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -227,11 +227,8 @@  __create_page_tables:
 	 * Create identity mapping to cater for __enable_mmu.
 	 * This identity mapping will be removed by paging_init().
 	 */
-	adr	r0, __turn_mmu_on_loc
-	ldmia	r0, {r3, r5, r6}
-	sub	r0, r0, r3			@ virt->phys offset
-	add	r5, r5, r0			@ phys __turn_mmu_on
-	add	r6, r6, r0			@ phys __turn_mmu_on_end
+	adr_l	r5, __turn_mmu_on		@ _pa(__turn_mmu_on)
+	adr_l	r6, __turn_mmu_on_end		@ _pa(__turn_mmu_on_end)
 	mov	r5, r5, lsr #SECTION_SHIFT
 	mov	r6, r6, lsr #SECTION_SHIFT
 
@@ -354,11 +351,6 @@  __create_page_tables:
 	ret	lr
 ENDPROC(__create_page_tables)
 	.ltorg
-	.align
-__turn_mmu_on_loc:
-	.long	.
-	.long	__turn_mmu_on
-	.long	__turn_mmu_on_end
 
 #if defined(CONFIG_SMP)
 	.text