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

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>

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index e68faa4..724733b 100644 (file)
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -267,13 +267,23 @@ BEGIN_FTR_SECTION
 END_FTR_SECTION_IFSET(CPU_FTR_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 */
 
 .Lsyscall_error: