[PATCH v5 20/33] arm64: entry: Annotate unwind_hint for entry

[Chen Zhongjin]

When taking an exception/interrupt, add UNWIND_HINT_REGS to indicate
from which point the pt_regs is on stack.

Whether returning to userland or creating a new task, sp is
pointing to a pt_regs frame, add UNWIND_HINT_REGS after that.

Signed-off-by: Julien Thierry <jthierry@xxxxxxxxxx>
Signed-off-by: Chen Zhongjin <chenzhongjin@xxxxxxxxxx>
---
 arch/arm64/kernel/entry.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 3bd11101e79d..bbc440379304 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -120,6 +120,7 @@
 alternative_cb	spectre_v4_patch_fw_mitigation_enable
 	b	.L__asm_ssbd_skip\@		// Patched to NOP
 alternative_cb_end
+	UNWIND_HINT_REGS
 	ldr_this_cpu	\tmp2, arm64_ssbd_callback_required, \tmp1
 	cbz	\tmp2,	.L__asm_ssbd_skip\@
 	ldr	\tmp2, [tsk, #TSK_TI_FLAGS]
@@ -218,6 +219,7 @@ alternative_cb_end
 	stp	x24, x25, [sp, #16 * 12]
 	stp	x26, x27, [sp, #16 * 13]
 	stp	x28, x29, [sp, #16 * 14]
+	UNWIND_HINT_REGS
 
 	.if	\el == 0
 	clear_gp_regs
@@ -601,6 +603,7 @@ SYM_CODE_START_LOCAL(ret_to_kernel)
 SYM_CODE_END(ret_to_kernel)
 
 SYM_CODE_START_LOCAL(ret_to_user)
+	UNWIND_HINT_REGS
 	ldr	x19, [tsk, #TSK_TI_FLAGS]	// re-check for single-step
 	enable_step_tsk x19, x2
 #ifdef CONFIG_GCC_PLUGIN_STACKLEAK
@@ -872,6 +875,7 @@ NOKPROBE(cpu_switch_to)
  * This is how we return from a fork.
  */
 SYM_CODE_START(ret_from_fork)
+	UNWIND_HINT_REGS
 	bl	schedule_tail
 	cbz	x19, 1f				// not a kernel thread
 	mov	x0, x20
-- 
2.17.1