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ARM: 8702/1: head-common.S: Clear lr before jumping to start_kernel()
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commit 59b6359 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: 9520b1a ("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>
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Geert Uytterhoeven authored and Greg Kroah-Hartman committed Aug 7, 2020
1 parent baf191c commit e4efec8
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Original file line number Diff line number Diff line change
Expand Up @@ -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)

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