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SubjectRe: [PATCH] ARM: head-common.S: Clear lr before jumping to start_kernel()
On Tue, 3 Oct 2017, Geert Uytterhoeven wrote:

> 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>

Good! This fixes another similar case I had but I didn't come around to
look at closely yet.

Acked-by: Nicolas Pitre <nico@linaro.org>

Please send it to RMK's patch system.


> ---
> 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
>
>

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