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SubjectRe: [PATCH] powerpc/32: indirect function call use bctrl rather than blrl in ret_from_kernel_thread
Date
Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> 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.

Do we know if any 32-bit CPUs have a link stack predictor or similar?

cheers

> This is not a performance critical path but this should be fixed for
> consistency.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> 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 0273a1349006..61fdd53cdd9a 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -161,10 +161,10 @@ 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
>
> --
> 2.25.0

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