powerpc: Emulate sync instruction variants

Reserved fields of the sync instruction have been used for other
instructions (e.g. lwsync).  On processors that do not support variants
of the sync instruction, emulate it by executing a sync to subsume the
effect of the intended instruction.

Signed-off-by: James Yang <James.Yang@freescale.com>
[scottwood@freescale.com: whitespace and subject line fix]
Signed-off-by: Scott Wood <scottwood@freescale.com>

arch/powerpc/include/asm/ppc-opcode.h

@@ -143,6 +143,8 @@
 #define PPC_INST_LSWX			0x7c00042a
 #define PPC_INST_LWARX			0x7c000028
 #define PPC_INST_LWSYNC			0x7c2004ac
+#define PPC_INST_SYNC			0x7c0004ac
+#define PPC_INST_SYNC_MASK		0xfc0007fe
 #define PPC_INST_LXVD2X			0x7c000698
 #define PPC_INST_MCRXR			0x7c000400
 #define PPC_INST_MCRXR_MASK		0xfc0007fe

arch/powerpc/kernel/traps.c

@@ -1018,6 +1018,13 @@ static int emulate_instruction(struct pt_regs *regs)
 		return emulate_isel(regs, instword);
 	}
 
+	/* Emulate sync instruction variants */
+	if ((instword & PPC_INST_SYNC_MASK) == PPC_INST_SYNC) {
+		PPC_WARN_EMULATED(sync, regs);
+		asm volatile("sync");
+		return 0;
+	}
+
 #ifdef CONFIG_PPC64
 	/* Emulate the mfspr rD, DSCR. */
 	if ((((instword & PPC_INST_MFSPR_DSCR_USER_MASK) ==