[PATCH] arm64: entry: drop the unused tmp2 argument of mte_set_kernel_gcr()

[PATCH] arm64: entry: drop the unused tmp2 argument of mte_set_kernel_gcr()

[Bradley Morgan]

mte_set_kernel_gcr() takes a tmp2 argument the macro never uses. It
used to, the body passed \tmp and \tmp2 to mte_set_gcr, then
commit 82868247897b ("arm64: kasan: mte: use a constant kernel
GCR_EL1 value") swapped that for

    mov     \tmp, KERNEL_GCR_EL1

and tmp2 stayed in the declaration and in the one caller, which
passes x23 for it.

Drop it, both places.

Signed-off-by: Bradley Morgan <brads@mainlining.org>

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 0e1d9c3c6a93..2baefe7a82d3 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -171,7 +171,7 @@
 #endif
 	.endm

-	.macro mte_set_kernel_gcr, tmp, tmp2
+	.macro mte_set_kernel_gcr, tmp
 #ifdef CONFIG_KASAN_HW_TAGS
 alternative_cb	ARM64_ALWAYS_SYSTEM, kasan_hw_tags_enable
 	b	1f
@@ -258,7 +258,7 @@

 	apply_ssbd 1, x22, x23

-	mte_set_kernel_gcr x22, x23
+	mte_set_kernel_gcr x22

 	/*
 	 * Any non-self-synchronizing system register updates required for
---
 arch/arm64/kernel/entry.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index f63049ac32dc..c3106dee61e1 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -171,7 +171,7 @@ alternative_else_nop_endif
 #endif
 	.endm
 
-	.macro mte_set_kernel_gcr, tmp, tmp2
+	.macro mte_set_kernel_gcr, tmp
 #ifdef CONFIG_KASAN_HW_TAGS
 alternative_cb	ARM64_ALWAYS_SYSTEM, kasan_hw_tags_enable
 	b	1f
@@ -258,7 +258,7 @@ alternative_else_nop_endif
 
 	apply_ssbd 1, x22, x23
 
-	mte_set_kernel_gcr x22, x23
+	mte_set_kernel_gcr x22
 
 	/*
 	 * Any non-self-synchronizing system register updates required for
-- 
2.53.0

Re: [PATCH] arm64: entry: drop the unused tmp2 argument of mte_set_kernel_gcr()

[Bradley Morgan]

On 7 October 2026 18:45:01 BST, Bradley Morgan <brads@mainlining.org>
wrote:
>mte_set_kernel_gcr() takes a tmp2 argument the macro never uses. It
>used to, the body passed \tmp and \tmp2 to mte_set_gcr, then
>commit 82868247897b ("arm64: kasan: mte: use a constant kernel
>GCR_EL1 value") swapped that for
>
>    mov     \tmp, KERNEL_GCR_EL1
>
>and tmp2 stayed in the declaration and in the one caller, which
>passes x23 for it.
>
>Drop it, both places.
>
>Signed-off-by: Bradley Morgan <brads@mainlining.org>
>
>diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
>index 0e1d9c3c6a93..2baefe7a82d3 100644
>--- a/arch/arm64/kernel/entry.S
>+++ b/arch/arm64/kernel/entry.S
>@@ -171,7 +171,7 @@
> #endif
> 	.endm
>
>-	.macro mte_set_kernel_gcr, tmp, tmp2
>+	.macro mte_set_kernel_gcr, tmp
> #ifdef CONFIG_KASAN_HW_TAGS
> alternative_cb	ARM64_ALWAYS_SYSTEM, kasan_hw_tags_enable
> 	b	1f
>@@ -258,7 +258,7 @@
>
> 	apply_ssbd 1, x22, x23
>
>-	mte_set_kernel_gcr x22, x23
>+	mte_set_kernel_gcr x22
>
> 	/*
> 	 * Any non-self-synchronizing system register updates required for
>---

AHH. What happened here, ugh! Why was it sent twice, stupid me man. Let me
go resend it PROPERLY, god sake Bradley..

> arch/arm64/kernel/entry.S | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
>index f63049ac32dc..c3106dee61e1 100644
>--- a/arch/arm64/kernel/entry.S
>+++ b/arch/arm64/kernel/entry.S
>@@ -171,7 +171,7 @@ alternative_else_nop_endif
> #endif
> 	.endm
> 
>-	.macro mte_set_kernel_gcr, tmp, tmp2
>+	.macro mte_set_kernel_gcr, tmp
> #ifdef CONFIG_KASAN_HW_TAGS
> alternative_cb	ARM64_ALWAYS_SYSTEM, kasan_hw_tags_enable
> 	b	1f
>@@ -258,7 +258,7 @@ alternative_else_nop_endif
> 
> 	apply_ssbd 1, x22, x23
> 
>-	mte_set_kernel_gcr x22, x23
>+	mte_set_kernel_gcr x22
> 
> 	/*
> 	 * Any non-self-synchronizing system register updates required for
>

--- Thanks!
"I'm not a very positive person" - Linus torvalds