x86: Fix moffset decoding

Signed-off-by: Pekka Enberg <penberg@iki.fi>
libcpu · Jan 9, 2014 · ef0c4d0 · ef0c4d0
1 parent 477c70a
commit ef0c4d0
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Showing 2 changed files with 41 additions and 17 deletions.
diff --git a/arch/x86/x86_decode.cpp b/arch/x86/x86_decode.cpp
@@ -179,10 +179,10 @@ static const uint32_t decode_table[256] = {
 	/*[0x9D]*/	INSTR_POPF | ADDMODE_IMPLIED,
 	/*[0x9E]*/	INSTR_SAHF | ADDMODE_IMPLIED,
 	/*[0x9F]*/	INSTR_LAHF | ADDMODE_IMPLIED,
-	/*[0xA0]*/	INSTR_MOV | ADDMODE_MEM_ACC | WIDTH_BYTE, /* load */
-	/*[0xA1]*/	INSTR_MOV | ADDMODE_MEM_ACC | WIDTH_FULL, /* load */
-	/*[0xA2]*/	INSTR_MOV | ADDMODE_ACC_MEM | WIDTH_BYTE, /* store */
-	/*[0xA3]*/	INSTR_MOV | ADDMODE_ACC_MEM | WIDTH_FULL, /* store */
+	/*[0xA0]*/	INSTR_MOV | ADDMODE_MOFFSET_ACC | WIDTH_BYTE, /* load */
+	/*[0xA1]*/	INSTR_MOV | ADDMODE_MOFFSET_ACC | WIDTH_FULL, /* load */
+	/*[0xA2]*/	INSTR_MOV | ADDMODE_ACC_MOFFSET | WIDTH_BYTE, /* store */
+	/*[0xA3]*/	INSTR_MOV | ADDMODE_ACC_MOFFSET | WIDTH_FULL, /* store */
 	/*[0xA4]*/	INSTR_MOVSB | ADDMODE_IMPLIED | WIDTH_BYTE,
 	/*[0xA5]*/	INSTR_MOVSW | ADDMODE_IMPLIED | WIDTH_FULL,
 	/*[0xA6]*/	INSTR_CMPSB | ADDMODE_IMPLIED | WIDTH_BYTE,
@@ -318,6 +318,7 @@ decode_dst_operand(struct x86_instr *instr)
 		operand->type	= OP_REG;
 		operand->reg	= 0; /* AL/AX */
 		break;
+	case DST_MOFFSET:
 	case DST_MEM:
 		operand->type	= OP_MEM;
 		operand->disp	= instr->disp;
@@ -372,6 +373,7 @@ decode_src_operand(struct x86_instr *instr)
 		operand->type	= OP_REG;
 		operand->reg	= 0; /* AL/AX */
 		break;
+	case SRC_MOFFSET:
 	case SRC_MEM:
 		operand->type	= OP_MEM;
 		operand->disp	= instr->disp;
@@ -470,6 +472,21 @@ decode_rel(struct x86_instr *instr, uint8_t* RAM, addr_t *pc)
 	}
 }
 
+static void
+decode_moffset(struct x86_instr *instr, uint8_t* RAM, addr_t *pc)
+{
+	switch (instr->flags & WIDTH_MASK) {
+	case WIDTH_FULL:
+		instr->disp = read_u16(RAM, pc);
+		instr->nr_bytes += 2;
+		break;
+	case WIDTH_BYTE:
+		instr->disp = read_u8(RAM, pc);
+		instr->nr_bytes += 1;
+		break;
+	}
+}
+
 static void
 decode_disp(struct x86_instr *instr, uint8_t* RAM, addr_t *pc)
 {
@@ -588,6 +605,9 @@ arch_8086_decode_instr(struct x86_instr *instr, uint8_t* RAM, addr_t pc)
 	if (instr->flags & MEM_DISP_MASK)
 		decode_disp(instr, RAM, &pc);
 
+	if (instr->flags & MOFFSET_MASK)
+		decode_moffset(instr, RAM, &pc);
+
 	if (instr->flags & IMM_MASK)
 		decode_imm(instr, RAM, &pc);
 

diff --git a/arch/x86/x86_decode.h b/arch/x86/x86_decode.h
@@ -67,22 +67,26 @@ enum x86_instr_flags {
 	SRC_SEG_REG		= (1U << 17),
 	SRC_ACC			= (1U << 18),
 	SRC_MEM			= (1U << 19),
-	SRC_MEM_DISP_BYTE	= (1U << 20),
-	SRC_MEM_DISP_FULL	= (1U << 21),
-	SRC_MASK		= SRC_NONE|IMM_MASK|REL_MASK|SRC_REG|SRC_SEG_REG|SRC_ACC|SRC_MEM|SRC_MEM_DISP_BYTE|SRC_MEM_DISP_FULL,
+	SRC_MOFFSET		= (1U << 20),
+	SRC_MEM_DISP_BYTE	= (1U << 21),
+	SRC_MEM_DISP_FULL	= (1U << 22),
+	SRC_MASK		= SRC_NONE|IMM_MASK|REL_MASK|SRC_REG|SRC_SEG_REG|SRC_ACC|SRC_MEM|SRC_MOFFSET|SRC_MEM_DISP_BYTE|SRC_MEM_DISP_FULL,
 
 	/* Destination operand */
-	DST_NONE		= (1U << 22),
-	DST_REG			= (1U << 23),
-	DST_ACC			= (1U << 24),	/* AL/AX */
-	DST_MEM			= (1U << 25),
-	DST_MEM_DISP_BYTE	= (1U << 26),	/* 8 bits */
-	DST_MEM_DISP_FULL	= (1U << 27),	/* 16 bits or 32 bits */
-	DST_MASK		= DST_NONE|DST_REG|DST_ACC|DST_MEM|DST_MEM_DISP_BYTE|DST_MEM_DISP_FULL,
+	DST_NONE		= (1U << 23),
+	DST_REG			= (1U << 24),
+	DST_ACC			= (1U << 25),	/* AL/AX */
+	DST_MEM			= (1U << 26),
+	DST_MOFFSET		= (1U << 27),
+	DST_MEM_DISP_BYTE	= (1U << 28),	/* 8 bits */
+	DST_MEM_DISP_FULL	= (1U << 29),	/* 16 bits or 32 bits */
+	DST_MASK		= DST_NONE|DST_REG|DST_ACC|DST_MOFFSET|DST_MEM|DST_MEM_DISP_BYTE|DST_MEM_DISP_FULL,
 
 	MEM_DISP_MASK		= SRC_MEM|SRC_MEM_DISP_BYTE|SRC_MEM_DISP_FULL|DST_MEM|DST_MEM_DISP_BYTE|DST_MEM_DISP_FULL,
 
-	GROUP_2			= (1U << 28),
+	MOFFSET_MASK		= SRC_MOFFSET|DST_MOFFSET,
+
+	GROUP_2			= (1U << 30),
 
 	GROUP_MASK		= GROUP_2,
 };
@@ -91,14 +95,14 @@ enum x86_instr_flags {
  *	Addressing modes.
  */
 enum x86_addmode {
-	ADDMODE_ACC_MEM		= SRC_ACC|DST_MEM|DIR_REVERSED,	/* AL/AX -> memory */
+	ADDMODE_ACC_MOFFSET	= SRC_ACC|DST_MOFFSET,		/* AL/AX -> moffset */
 	ADDMODE_ACC_REG		= SRC_ACC|DST_REG,		/* AL/AX -> reg */
 	ADDMODE_IMM		= SRC_IMM|DST_NONE,		/* immediate operand */
 	ADDMODE_IMM8_RM		= SRC_IMM8|MOD_RM|DIR_REVERSED,	/* immediate -> register/memory */
 	ADDMODE_IMM_ACC		= SRC_IMM|DST_ACC,		/* immediate -> AL/AX */
 	ADDMODE_IMM_REG		= SRC_IMM|DST_REG,		/* immediate -> register */
 	ADDMODE_IMPLIED		= SRC_NONE|DST_NONE,		/* no operands */
-	ADDMODE_MEM_ACC		= SRC_ACC|DST_MEM,		/* memory -> AL/AX */
+	ADDMODE_MOFFSET_ACC	= SRC_MOFFSET|DST_ACC,		/* moffset -> AL/AX */
 	ADDMODE_REG		= SRC_REG|DST_NONE,		/* register */
 	ADDMODE_SEG_REG		= SRC_SEG_REG|DST_NONE,		/* segment register */
 	ADDMODE_REG_RM		= SRC_REG|MOD_RM|DIR_REVERSED,	/* register -> register/memory */