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    Subject[PATCH AUTOSEL 5.10 35/53] powerpc/32: indirect function call use bctrl rather than blrl in ret_from_kernel_thread
    Date
    From: Christophe Leroy <christophe.leroy@csgroup.eu>

    [ Upstream commit 113ec9ccc8049c3772f0eab46b62c5d6654c09f7 ]

    Copied from commit 89bbe4c798bc ("powerpc/64: indirect function call
    use bctrl rather than blrl in ret_from_kernel_thread")

    blrl is not recommended to use as an indirect function call, as it may
    corrupt the link stack predictor.

    This is not a performance critical path but this should be fixed for
    consistency.

    Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/91b1d242525307ceceec7ef6e832bfbacdd4501b.1629436472.git.christophe.leroy@csgroup.eu
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/kernel/entry_32.S | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
    index 459f5d00b990..a3db3748172c 100644
    --- a/arch/powerpc/kernel/entry_32.S
    +++ b/arch/powerpc/kernel/entry_32.S
    @@ -496,10 +496,10 @@ ret_from_fork:
    ret_from_kernel_thread:
    REST_NVGPRS(r1)
    bl schedule_tail
    - mtlr r14
    + mtctr r14
    mr r3,r15
    PPC440EP_ERR42
    - blrl
    + bctrl
    li r3,0
    b ret_from_syscall

    --
    2.30.2
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