[PATCH 2/2] ARM64: setup_c: abi safe link register storage

[Stefan Kerkmann <s.kerkmann@pengutronix.de>]

The ARM64 setup_c function saved the link register (x30) in the caller
save register (x15). This is fragile as a constructor might use x15,
thus save it on the stack just like ARM32 and RISC-V.

Fixes: bb07ef11d6 ("ARM/ARM64/RISC-V: pbl: add constructor support")
Signed-off-by: Stefan Kerkmann <s.kerkmann@pengutronix.de>
---
 arch/arm/cpu/setupc_64.S | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/arm/cpu/setupc_64.S b/arch/arm/cpu/setupc_64.S
index e3c6149e27..b1cfea47b1 100644
--- a/arch/arm/cpu/setupc_64.S
+++ b/arch/arm/cpu/setupc_64.S
@@ -10,10 +10,10 @@
  * setup_c: clear bss if not yet done
  */
 ENTRY(setup_c)
+	str x30, [sp, #-16]!
 	adr_l	x0, bss_cleared
 	ldr	w1, [x0]
 	cbnz	w1, 1f			/* skip if already done */
-	mov	x15, x30
 	adr_l	x0, __bss_start
 	mov	x1, #0
 	adr_l	x2, __bss_stop
@@ -25,8 +25,9 @@ ENTRY(setup_c)
 #ifdef __PBL__
 	bl	pbl_do_ctors
 #endif
-	mov	x30, x15
-1:	ret
+1:
+	ldr x30, [sp], #16
+	ret
 ENDPROC(setup_c)
 
 .section .data.bss_cleared

-- 
2.47.3