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[10/14] arm64: assembler: allow adr_this_cpu to use the stack pointer

Message ID 1502130965-18710-11-git-send-email-mark.rutland@arm.com (mailing list archive)
State New, archived
Headers show

Commit Message

Mark Rutland Aug. 7, 2017, 6:36 p.m. UTC
From: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Given that adr_this_cpu already requires a temp register in addition
to the destination register, tweak the instruction sequence so that sp
may be used as well.

This will simplify switching to per-cpu stacks in subsequent patches. While
this limits the range of adr_this_cpu, to +/-4GiB, we don't currently use
adr_this_cpu in modules, and this is not problematic for the main kernel image.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
[Mark: add more commit text]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/include/asm/assembler.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Catalin Marinas Aug. 14, 2017, 5:13 p.m. UTC | #1
On Mon, Aug 07, 2017 at 07:36:01PM +0100, Mark Rutland wrote:
> From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> 
> Given that adr_this_cpu already requires a temp register in addition
> to the destination register, tweak the instruction sequence so that sp
> may be used as well.
> 
> This will simplify switching to per-cpu stacks in subsequent patches. While
> this limits the range of adr_this_cpu, to +/-4GiB, we don't currently use
> adr_this_cpu in modules, and this is not problematic for the main kernel image.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> [Mark: add more commit text]
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: James Morse <james.morse@arm.com>
> Cc: Laura Abbott <labbott@redhat.com>
> Cc: Will Deacon <will.deacon@arm.com>
> ---
>  arch/arm64/include/asm/assembler.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
> index 610a420..4775af5 100644
> --- a/arch/arm64/include/asm/assembler.h
> +++ b/arch/arm64/include/asm/assembler.h
> @@ -235,7 +235,8 @@
>  	 * @tmp: scratch register
>  	 */
>  	.macro adr_this_cpu, dst, sym, tmp
> -	adr_l	\dst, \sym
> +	adrp	\tmp, \sym
> +	add	\dst, \tmp, #:lo12:\sym
>  	mrs	\tmp, tpidr_el1
>  	add	\dst, \dst, \tmp
>  	.endm

Nitpick: it may be worth adding an #ifndef MODULE around these macros,
together with a comment, just in case. There are other macros in this
file like adr_l which are used in modules (crypto).
diff mbox

Patch

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 610a420..4775af5 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -235,7 +235,8 @@ 
 	 * @tmp: scratch register
 	 */
 	.macro adr_this_cpu, dst, sym, tmp
-	adr_l	\dst, \sym
+	adrp	\tmp, \sym
+	add	\dst, \tmp, #:lo12:\sym
 	mrs	\tmp, tpidr_el1
 	add	\dst, \dst, \tmp
 	.endm