[PATCH 1/2] powerpc: Fix emulation of mcrf in emulate_step()

[Anton Blanchard]

From: Anton Blanchard <anton at samba.org>

The mcrf emulation code was looking at the CR fields in the reverse
order. It also relied on reserved fields being zero which is somewhat
fragile, so fix that too.

Cc: stable at vger.kernel.org
Signed-off-by: Anton Blanchard <anton at samba.org>
---
 arch/powerpc/lib/sstep.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index 33117f8a0882..fb84f51b1f0b 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -683,8 +683,10 @@ int analyse_instr(struct instruction_op *op, struct pt_regs *regs,
 	case 19:
 		switch ((instr >> 1) & 0x3ff) {
 		case 0:		/* mcrf */
-			rd = (instr >> 21) & 0x1c;
-			ra = (instr >> 16) & 0x1c;
+			rd = 7 - ((instr >> 23) & 0x7);
+			ra = 7 - ((instr >> 18) & 0x7);
+			rd *= 4;
+			ra *= 4;
 			val = (regs->ccr >> ra) & 0xf;
 			regs->ccr = (regs->ccr & ~(0xfUL << rd)) | (val << rd);
 			goto instr_done;
-- 
2.11.0