powerpc: Don't emulate mr. instructions

Currently emulate_step() emulates mr. instructions without updating cr0
and this can be disastrous. Don't emulate mr.

This bug has been around for a while, but I am not sure if its a worthy
-stable candidate. I'll leave it to Ben do decide.

Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index 4aae0c387645..13b7d54f185b 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -172,6 +172,8 @@ int __kprobes emulate_step(struct pt_regs *regs, unsigned int instr)
                         }
                         break;
                 case 0x378:     /* orx */
+                        if (instr & 1)
+                                break;
                         rs = (instr >> 21) & 0x1f;
                         rb = (instr >> 11) & 0x1f;
                         if (rs == rb) {         /* mr */