linux-kernel - [PATCH 3.2 42/74] powerpc: Fix emulation of mfocrf in emulate

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Date:   Mon, 09 Oct 2017 13:30:34 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Michael Ellerman" <mpe@...erman.id.au>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        "Anton Blanchard" <anton@...ba.org>
Subject: [PATCH 3.2 42/74] powerpc: Fix emulation of mfocrf in emulate_step()

3.2.94-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Anton Blanchard <anton@...ba.org>

commit 64e756c55aa46fc18fd53e8f3598b73b528d8637 upstream.

=46romPOWER4 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@...ba.org>
Acked-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/powerpc/lib/sstep.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -863,6 +863,19 @@ int __kprobes emulate_step(struct pt_reg
 			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;