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* [PATCH] ARM: head-common.S: Clear lr before jumping to start_kernel()
@ 2017-10-03 15:23 Geert Uytterhoeven
  2017-10-03 15:37 ` Nicolas Pitre
  0 siblings, 1 reply; 15+ messages in thread
From: Geert Uytterhoeven @ 2017-10-03 15:23 UTC (permalink / raw)
  To: linux-arm-kernel

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>
---
Commit 9520b1a1b5f7a348 is in arm/for-next.

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

diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index a25027b87a6024b9..21dde771a7dd8d14 100644
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -114,6 +114,7 @@ __mmap_switched:
 	str	r8, [r2]			@ Save atags pointer
 	cmp	r3, #0
 	strne	r10, [r3]			@ Save control register values
+	mov	lr, #0
 	b	start_kernel
 ENDPROC(__mmap_switched)
 
-- 
2.7.4

^ permalink raw reply related	[flat|nested] 15+ messages in thread

end of thread, other threads:[~2017-10-16 12:29 UTC | newest]

Thread overview: 15+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2017-10-03 15:23 [PATCH] ARM: head-common.S: Clear lr before jumping to start_kernel() Geert Uytterhoeven
2017-10-03 15:37 ` Nicolas Pitre
2017-10-03 18:11   ` Geert Uytterhoeven
2017-10-03 18:15     ` Geert Uytterhoeven
2017-10-03 18:15       ` Geert Uytterhoeven
2017-10-10 20:33         ` Tony Lindgren
2017-10-12 10:23           ` Russell King - ARM Linux
2017-10-12 12:34             ` Geert Uytterhoeven
2017-10-12 15:25             ` Nicolas Pitre
2017-10-14 14:14               ` Russell King - ARM Linux
2017-10-14 14:17                 ` Russell King - ARM Linux
2017-10-14 15:49                   ` Nicolas Pitre
2017-10-14 18:20                     ` Russell King - ARM Linux
2017-10-15  8:04                 ` Geert Uytterhoeven
2017-10-16 12:29                   ` Russell King - ARM Linux

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