powerpc: Fix emulation of mfocrf in emulate_step()

From POWER4 onwards, mfocrf() only places the specified CR field into
the destination GPR, and the rest of it is set to 0. The PowerPC AS
from version 3.0 now requires this behaviour.

The emulation code currently puts the entire CR into the destination GPR.
Fix it.

Fixes: 6888199f7fe5 ("[POWERPC] Emulate more instructions in software")
Cc: stable@vger.kernel.org # v2.6.22+
Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 13 insertions, 0 deletions

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index fb84f51b1f0b..ee33327686ae 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -966,6 +966,19 @@ int analyse_instr(struct instruction_op *op, struct pt_regs *regs,
 #endif
 
                 case 19:        /* mfcr */
+                        if ((instr >> 20) & 1) {
+                                imm = 0xf0000000UL;
+                                for (sh = 0; sh < 8; ++sh) {
+                                        if (instr & (0x80000 >> sh)) {
+                                                regs->gpr[rd] = regs->ccr & imm;
+                                                break;
+                                        }
+                                        imm >>= 4;
+                                }
+
+                                goto instr_done;
+                        }
+
                         regs->gpr[rd] = regs->ccr;
                         regs->gpr[rd] &= 0xffffffffUL;
                         goto instr_done;