Re: [PATCH] powerpc/32: indirect function call use bctrl rather than blrl in ret_from_kernel_thread
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2021-08-20 12:15:19
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lkml
Christophe Leroy [off-list ref] 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
quoted hunk ↗ jump to hunk
This is not a performance critical path but this should be fixed for consistency. Signed-off-by: Christophe Leroy <redacted> --- 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