powerpc: Fix emulation of mfocrf in emulate_step()

commit 64e756c55aa46fc18fd53e8f3598b73b528d8637 upstream.

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")
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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index 9a52349..6ca7fe0 100644 (file)
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -863,6 +863,19 @@ int __kprobes emulate_step(struct pt_regs *regs, unsigned int instr)
                        goto instr_done;
 #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;