ARM: 8702/1: head-common.S: Clear lr before jumping to start_kernel()

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
start_kernel().

Fixes: 9520b1a1b5f7a348 ("ARM: head-common.S: speed up startup code")
Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index 7e662bdd5cb36e8422b6ac9ba10da8dde32cbcdf..932b2244e7093f2acf9f0311f341fd2c1fa6623d 100644 (file)
--- 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
 ENDPROC(__mmap_switched)