linux-kernel - [PATCH 3.10 033/139] powerpc: Fix emulation of mfocrf in emulate

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Message-Id: <1509571159-4405-34-git-send-email-w@1wt.eu>
Date:   Wed,  1 Nov 2017 22:17:33 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Anton Blanchard <anton@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 033/139] powerpc: Fix emulation of mfocrf in emulate_step()

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

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")
Cc: stable@...r.kernel.org 
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: Willy Tarreau <w@....eu>
---
 arch/powerpc/lib/sstep.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index 08490ec..23da15f 100644
--- 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;
-- 
2.8.0.rc2.1.gbe9624a