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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index b6e4eca..776c1a1 100644 (file)
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -970,6 +970,19 @@ int __kprobes 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;