[PATCH] x86 emulator: Add Src2 decode set

[Guillaume Thouvenin <guillaume.thouvenin@ext.bull.net>]

Instruction like shld has three operands, so we need to add a Src2
decode set. We start with Src2None, Src2CL, and Src2Imm8 to support
shld and we will expand it later.

Signed-off-by: Guillaume Thouvenin <guillaume.thouvenin@ext.bull.net>
---
 arch/x86/kvm/x86_emulate.c        |   47 ++++++++++++++++++++++++++++----------
 include/asm-x86/kvm_x86_emulate.h |    1 
 2 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index a391e21..c9ef2da 100644
--- a/arch/x86/kvm/x86_emulate.c
+++ b/arch/x86/kvm/x86_emulate.c
@@ -59,16 +59,21 @@
 #define SrcImm      (5<<4)	/* Immediate operand. */
 #define SrcImmByte  (6<<4)	/* 8-bit sign-extended immediate operand. */
 #define SrcMask     (7<<4)
+/* Source 2 operand type */
+#define Src2None    (0<<7)
+#define Src2CL      (1<<7)
+#define Src2Imm8    (2<<7)
+#define Src2Mask    (7<<7)
 /* Generic ModRM decode. */
-#define ModRM       (1<<7)
+#define ModRM       (1<<24)
 /* Destination is only written; never read. */
-#define Mov         (1<<8)
-#define BitOp       (1<<9)
-#define MemAbs      (1<<10)      /* Memory operand is absolute displacement */
-#define String      (1<<12)     /* String instruction (rep capable) */
-#define Stack       (1<<13)     /* Stack instruction (push/pop) */
-#define Group       (1<<14)     /* Bits 3:5 of modrm byte extend opcode */
-#define GroupDual   (1<<15)     /* Alternate decoding of mod == 3 */
+#define Mov         (1<<25)
+#define BitOp       (1<<26)
+#define MemAbs      (1<<27)     /* Memory operand is absolute displacement */
+#define String      (1<<28)     /* String instruction (rep capable) */
+#define Stack       (1<<29)     /* Stack instruction (push/pop) */
+#define Group       (1<<30)     /* Bits 3:5 of modrm byte extend opcode */
+#define GroupDual   (1<<31)     /* Alternate decoding of mod == 3 */
 #define GroupMask   0xff        /* Group number stored in bits 0:7 */
 
 enum {
@@ -76,7 +81,7 @@ enum {
 	Group1A, Group3_Byte, Group3, Group4, Group5, Group7,
 };
 
-static u16 opcode_table[256] = {
+static u32 opcode_table[256] = {
 	/* 0x00 - 0x07 */
 	ByteOp | DstMem | SrcReg | ModRM, DstMem | SrcReg | ModRM,
 	ByteOp | DstReg | SrcMem | ModRM, DstReg | SrcMem | ModRM,
@@ -195,7 +200,7 @@ static u16 opcode_table[256] = {
 	ImplicitOps, ImplicitOps, Group | Group4, Group | Group5,
 };
 
-static u16 twobyte_table[256] = {
+static u32 twobyte_table[256] = {
 	/* 0x00 - 0x0F */
 	0, Group | GroupDual | Group7, 0, 0, 0, 0, ImplicitOps, 0,
 	ImplicitOps, ImplicitOps, 0, 0, 0, ImplicitOps | ModRM, 0, 0,
@@ -253,7 +258,7 @@ static u16 twobyte_table[256] = {
 	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
 };
 
-static u16 group_table[] = {
+static u32 group_table[] = {
 	[Group1_80*8] =
 	ByteOp | DstMem | SrcImm | ModRM, ByteOp | DstMem | SrcImm | ModRM,
 	ByteOp | DstMem | SrcImm | ModRM, ByteOp | DstMem | SrcImm | ModRM,
@@ -297,7 +302,7 @@ static u16 group_table[] = {
 	SrcMem16 | ModRM | Mov, SrcMem | ModRM | ByteOp,
 };
 
-static u16 group2_table[] = {
+static u32 group2_table[] = {
 	[Group7*8] =
 	SrcNone | ModRM, 0, 0, 0,
 	SrcNone | ModRM | DstMem | Mov, 0,
@@ -1043,6 +1048,24 @@ done_prefixes:
 		break;
 	}
 
+	/*
+	 * Decode and fetch the second source operand: register, memory
+	 * or immediate.
+	 */
+	switch (c->d & Src2Mask) {
+	case Src2None:
+		break;
+	case Src2CL:
+		c->src2.val = c->regs[VCPU_REGS_RCX];
+		break;
+	case Src2Imm8:
+		c->src2.type = OP_IMM;
+		c->src2.ptr = (unsigned long *)c->eip;
+		c->src2.bytes = 1;
+		c->src2.val = insn_fetch(u8, 1, c->eip);
+		break;
+	}
+
 	/* Decode and fetch the destination operand: register or memory. */
 	switch (c->d & DstMask) {
 	case ImplicitOps:
diff --git a/include/asm-x86/kvm_x86_emulate.h b/include/asm-x86/kvm_x86_emulate.h
index 4e8c1e4..00de896 100644
--- a/include/asm-x86/kvm_x86_emulate.h
+++ b/include/asm-x86/kvm_x86_emulate.h
@@ -123,6 +123,7 @@ struct decode_cache {
 	u8 ad_bytes;
 	u8 rex_prefix;
 	struct operand src;
+	struct operand src2;
 	struct operand dst;
 	bool has_seg_override;
 	u8 seg_override;