Re: [PATCH] powerpc/64: indirect function call use bctrl rather than blrl in ret_from_kernel_thread
From: Christophe Leroy <hidden>
Date: 2020-06-11 12:29:26
Le 11/06/2020 à 14:11, Nicholas Piggin a écrit :
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.
There's exactly the same in entry_32.S Should it be changed there too ... for consistency :) ? ppc32 also uses blrl for calling syscall handler, should it be changed as well ? Christophe
quoted hunk ↗ jump to hunk
Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/kernel/entry_64.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 223c4f008e63..f59a17471d4d 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S@@ -400,12 +400,12 @@ _GLOBAL(ret_from_fork) _GLOBAL(ret_from_kernel_thread) bl schedule_tail REST_NVGPRS(r1) - mtlr r14 + mtctr r14 mr r3,r15 #ifdef PPC64_ELF_ABI_v2 mr r12,r14 #endif - blrl + bctrl li r3,0 b .Lsyscall_exit