[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
State New
Headers show
Series
  • arm64: VMAP_STACK support
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Commit Message

Mark Rutland Aug. 7, 2017, 6:36 p.m.
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(-)

-- 
1.9.1

Comments

Catalin Marinas Aug. 14, 2017, 5:13 p.m. | #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).

-- 
Catalin
Mark Rutland Aug. 14, 2017, 5:42 p.m. | #2
On Mon, Aug 14, 2017 at 06:13:39PM +0100, Catalin Marinas wrote:
> On Mon, Aug 07, 2017 at 07:36:01PM +0100, Mark Rutland wrote:


> >  	.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).


I've folded in the below, in keeping with the other MODULE fallbacks.

Thanks,
Mark.

---->8----diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 4775af5..50c5592 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -230,13 +230,18 @@
        .endm
 
        /*
-        * @dst: Result of per_cpu(sym, smp_processor_id())
+        * @dst: Result of per_cpu(sym, smp_processor_id()), can be SP for
+        *       non-module code
         * @sym: The name of the per-cpu variable
         * @tmp: scratch register
         */
        .macro adr_this_cpu, dst, sym, tmp
+#ifndef MODULE
        adrp    \tmp, \sym
        add     \dst, \tmp, #:lo12:\sym
+#else
+       adr_l   \tmp, \sym
+#endif
        mrs     \tmp, tpidr_el1
        add     \dst, \dst, \tmp
        .endm

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