ARM: Thumb-2: Fix exception return sequence to restore stack correctly
The implementation of svc_exit didn't take into account any stack hole
created by svc_entry; as happens with the undef handler when kprobes are
configured. The fix is to read the saved value of SP rather than trying
to calculate it.
Signed-off-by: Jon Medhurst <tixy@yxit.co.uk>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S
index 051166c..83e29ad 100644
--- a/arch/arm/kernel/entry-header.S
+++ b/arch/arm/kernel/entry-header.S
@@ -121,15 +121,13 @@
.endm
#else /* CONFIG_THUMB2_KERNEL */
.macro svc_exit, rpsr
+ ldr lr, [sp, #S_SP] @ top of the stack
+ ldrd r0, r1, [sp, #S_LR] @ calling lr and pc
clrex @ clear the exclusive monitor
- ldr r0, [sp, #S_SP] @ top of the stack
- ldr r1, [sp, #S_PC] @ return address
- tst r0, #4 @ orig stack 8-byte aligned?
- stmdb r0, {r1, \rpsr} @ rfe context
+ stmdb lr!, {r0, r1, \rpsr} @ calling lr and rfe context
ldmia sp, {r0 - r12}
- ldr lr, [sp, #S_LR]
- addeq sp, sp, #S_FRAME_SIZE - 8 @ aligned
- addne sp, sp, #S_FRAME_SIZE - 4 @ not aligned
+ mov sp, lr
+ ldr lr, [sp], #4
rfeia sp!
.endm