[v9,12/18] arm64: kexec: arm64_relocate_new_kernel don't use x0 as temp

Commit Message

Pasha Tatashin March 26, 2020, 3:24 a.m. UTC

x0 will contain the only argument to arm64_relocate_new_kernel; don't
use it as a temp. Reassigned registers to free-up x0.

Signed-off-by: Pavel Tatashin <[e-mail]>
---
 arch/arm64/kernel/relocate_kernel.S | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

Comments

James Morse May 7, 2020, 4:22 p.m. UTC | #1

Hi Pavel,

On 26/03/2020 03:24, Pavel Tatashin wrote:
> x0 will contain the only argument to arm64_relocate_new_kernel; don't
> use it as a temp. Reassigned registers to free-up x0.

The missing bit of motivation is _why_ you need x0 keep its value until the end of this code.

With that covered,
Reviewed-by: James Morse <[e-mail]>


Thanks,

James

Patch

diff --git a/arch/arm64/kernel/relocate_kernel.S b/arch/arm64/kernel/relocate_kernel.S
index e9c974ea4717..41f9c95fabe8 100644
--- a/arch/arm64/kernel/relocate_kernel.S
+++ b/arch/arm64/kernel/relocate_kernel.S
@@ -32,14 +32,14 @@  ENTRY(arm64_relocate_new_kernel)
 	mov	x14, xzr			/* x14 = entry ptr */
 	mov	x13, xzr			/* x13 = copy dest */
 	/* Clear the sctlr_el2 flags. */
-	mrs	x0, CurrentEL
-	cmp	x0, #CurrentEL_EL2
+	mrs	x2, CurrentEL
+	cmp	x2, #CurrentEL_EL2
 	b.ne	1f
-	mrs	x0, sctlr_el2
+	mrs	x2, sctlr_el2
 	ldr	x1, =SCTLR_ELx_FLAGS
-	bic	x0, x0, x1
+	bic	x2, x2, x1
 	pre_disable_mmu_workaround
-	msr	sctlr_el2, x0
+	msr	sctlr_el2, x2
 	isb
 1:	/* Check if the new image needs relocation. */
 	tbnz	x16, IND_DONE_BIT, .Ldone
@@ -51,17 +51,17 @@  ENTRY(arm64_relocate_new_kernel)
 	tbz	x16, IND_SOURCE_BIT, .Ltest_indirection
 
 	/* Invalidate dest page to PoC. */
-	mov     x0, x13
-	add     x20, x0, #PAGE_SIZE
+	mov     x2, x13
+	add     x20, x2, #PAGE_SIZE
 	sub     x1, x15, #1
-	bic     x0, x0, x1
-2:	dc      ivac, x0
-	add     x0, x0, x15
-	cmp     x0, x20
+	bic     x2, x2, x1
+2:	dc      ivac, x2
+	add     x2, x2, x15
+	cmp     x2, x20
 	b.lo    2b
 	dsb     sy
 
-	copy_page x13, x12, x0, x1, x2, x3, x4, x5, x6, x7
+	copy_page x13, x12, x1, x2, x3, x4, x5, x6, x7, x8
 	b	.Lnext
 .Ltest_indirection:
 	tbz	x16, IND_INDIRECTION_BIT, .Ltest_destination