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powerpc/64: Convert the syscall exit path to use RFI_TO_USER/KERNEL

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commit b8e90cb7bc04a509e821e82ab6ed7a8ef11ba333 upstream.

In the syscall exit path we may be returning to user or kernel
context. We already have a test for that, because we conditionally
restore r13. So use that existing test and branch, and bifurcate the
return based on that.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nicholas Piggin 2018-01-10 03:07:15 +11:00 committed by Greg Kroah-Hartman
parent 9bfecafe84
commit 8dd311f1ec
1 changed files with 11 additions and 1 deletions
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12
arch/powerpc/kernel/entry_64.S
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@ -230,13 +230,23 @@ END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
ACCOUNT_CPU_USER_EXIT(r11, r12)
HMT_MEDIUM_LOW_HAS_PPR
ld r13,GPR13(r1) /* only restore r13 if returning to usermode */
ld r2,GPR2(r1)
ld r1,GPR1(r1)
mtlr r4
mtcr r5
mtspr SPRN_SRR0,r7
mtspr SPRN_SRR1,r8
RFI_TO_USER
b . /* prevent speculative execution */
/* exit to kernel */
1: ld r2,GPR2(r1)
ld r1,GPR1(r1)
mtlr r4
mtcr r5
mtspr SPRN_SRR0,r7
mtspr SPRN_SRR1,r8
RFI
RFI_TO_KERNEL
b . /* prevent speculative execution */
syscall_error: