powerpc/64: Convert fast_exception_return to use RFI_TO_USER/KERNEL

commit a08f828cf47e6c605af21d2cdec68f84e799c318 upstream.

Similar to the syscall return path, in fast_exception_return 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>

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 150c402728d128d5a419fcb4a6ba230136d8ebf3..8a8a6d7ddcc6e65211dcea2d39ce8cfda847bb4a 100644 (file)
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -892,7 +892,7 @@ BEGIN_FTR_SECTION
 END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
        ACCOUNT_CPU_USER_EXIT(r13, r2, r4)
        REST_GPR(13, r1)
-1:
+
        mtspr   SPRN_SRR1,r3
 
        ld      r2,_CCR(r1)
@@ -905,8 +905,22 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
        ld      r3,GPR3(r1)
        ld      r4,GPR4(r1)
        ld      r1,GPR1(r1)
+       RFI_TO_USER
+       b       .       /* prevent speculative execution */
+
+1:     mtspr   SPRN_SRR1,r3
+
+       ld      r2,_CCR(r1)
+       mtcrf   0xFF,r2
+       ld      r2,_NIP(r1)
+       mtspr   SPRN_SRR0,r2
 
-       rfid
+       ld      r0,GPR0(r1)
+       ld      r2,GPR2(r1)
+       ld      r3,GPR3(r1)
+       ld      r4,GPR4(r1)
+       ld      r1,GPR1(r1)
+       RFI_TO_KERNEL
        b       .       /* prevent speculative execution */
 
 #endif /* CONFIG_PPC_BOOK3E */