[PATCH 4.14 8/8] ARM: 8702/1: head-common.S: Clear lr before jumping to start_kernel()

From: Greg Kroah-Hartman
Date: Wed Aug 05 2020 - 16:06:54 EST

From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>

commit 59b6359dd92d18f5dc04b14a4c926fa08ab66f7c upstream.

If CONFIG_DEBUG_LOCK_ALLOC=y, the kernel log is spammed with a few
hundred identical messages:

unwind: Unknown symbol address c0800300
unwind: Index not found c0800300

c0800300 is the return address from the last subroutine call (to
__memzero()) in __mmap_switched(). Apparently having this address in
the link register confuses the unwinder.

To fix this, reset the link register to zero before jumping to

Fixes: 9520b1a1b5f7a348 ("ARM: head-common.S: speed up startup code")
Suggested-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Acked-by: Nicolas Pitre <nico@xxxxxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>

arch/arm/kernel/head-common.S | 1 +
1 file changed, 1 insertion(+)

--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -101,6 +101,7 @@ __mmap_switched:
str r2, [r6] @ Save atags pointer
cmp r7, #0
strne r0, [r7] @ Save control register values
+ mov lr, #0
b start_kernel