powerpc: Split out instruction analysis part of emulate_step()

This splits out the instruction analysis part of emulate_step() into
a separate analyse_instr() function, which decodes the instruction,
but doesn't execute any load or store instructions.  It does execute
integer instructions and branches which can be executed purely by
updating register values in the pt_regs struct.  For other instructions,
it returns the instruction type and other details in a new
instruction_op struct.  emulate_step() then uses that information
to execute loads, stores, cache operations, mfmsr, mtmsr[d], and
(on 64-bit) sc instructions.

The reason for doing this is so that the KVM code can use it instead
of having its own separate instruction emulation code.  Possibly the
alignment interrupt handler could also use this.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/sstep.h

@@ -25,3 +25,64 @@ struct pt_regs;
 
 /* Emulate instructions that cause a transfer of control. */
 extern int emulate_step(struct pt_regs *regs, unsigned int instr);
+
+enum instruction_type {
+	COMPUTE,		/* arith/logical/CR op, etc. */
+	LOAD,
+	LOAD_MULTI,
+	LOAD_FP,
+	LOAD_VMX,
+	LOAD_VSX,
+	STORE,
+	STORE_MULTI,
+	STORE_FP,
+	STORE_VMX,
+	STORE_VSX,
+	LARX,
+	STCX,
+	BRANCH,
+	MFSPR,
+	MTSPR,
+	CACHEOP,
+	BARRIER,
+	SYSCALL,
+	MFMSR,
+	MTMSR,
+	RFI,
+	INTERRUPT,
+	UNKNOWN
+};
+
+#define INSTR_TYPE_MASK	0x1f
+
+/* Load/store flags, ORed in with type */
+#define SIGNEXT		0x20
+#define UPDATE		0x40	/* matches bit in opcode 31 instructions */
+#define BYTEREV		0x80
+
+/* Cacheop values, ORed in with type */
+#define CACHEOP_MASK	0x700
+#define DCBST		0
+#define DCBF		0x100
+#define DCBTST		0x200
+#define DCBT		0x300
+
+/* Size field in type word */
+#define SIZE(n)		((n) << 8)
+#define GETSIZE(w)	((w) >> 8)
+
+#define MKOP(t, f, s)	((t) | (f) | SIZE(s))
+
+struct instruction_op {
+	int type;
+	int reg;
+	unsigned long val;
+	/* For LOAD/STORE/LARX/STCX */
+	unsigned long ea;
+	int update_reg;
+	/* For MFSPR */
+	int spr;
+};
+
+extern int analyse_instr(struct instruction_op *op, struct pt_regs *regs,
+			 unsigned int instr);