powerpc: Fix emulation of mfocrf in emulate_step()

commit 64e756c 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: 6888199 ("[POWERPC] Emulate more instructions in software")
Signed-off-by: Anton Blanchard <[email protected]>
Acked-by: Naveen N. Rao <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: antonblanchard

arch/powerpc/lib/sstep.c

@@ -969,6 +969,19 @@ 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;