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powerpc/64: indirect function call use bctrl rather than blrl in ret_from_kernel_thread

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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: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200611121119.1015740-1-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2020-06-11 22:11:19 +10:00 committed by Michael Ellerman
parent 48778464bb
commit 89bbe4c798
1 changed files with 2 additions and 2 deletions
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arch/powerpc/kernel/entry_64.S
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@ -233,12 +233,12 @@ _GLOBAL(ret_from_fork)
_GLOBAL(ret_from_kernel_thread) _GLOBAL(ret_from_kernel_thread)
bl schedule_tail bl schedule_tail
REST_NVGPRS(r1) REST_NVGPRS(r1)
mtlr r14 mtctr r14
mr r3,r15 mr r3,r15
#ifdef PPC64_ELF_ABI_v2 #ifdef PPC64_ELF_ABI_v2
mr r12,r14 mr r12,r14
#endif #endif
blrl bctrl
li r3,0 li r3,0
b .Lsyscall_exit b .Lsyscall_exit