Enscript Output

extractedLnx/linux-2.6.24/drivers/kvm/x86_emulate.c_x86_emulate_memop.c

int
x86_emulate_memop(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
{
	unsigned d;
	u8 b, sib, twobyte = 0, rex_prefix = 0;
	u8 modrm, modrm_mod = 0, modrm_reg = 0, modrm_rm = 0;
	unsigned long *override_base = NULL;
	unsigned int op_bytes, ad_bytes, lock_prefix = 0, rep_prefix = 0, i;
	int rc = 0;
	struct operand src, dst;
	unsigned long cr2 = ctxt->cr2;
	int mode = ctxt->mode;
	unsigned long modrm_ea;
	int use_modrm_ea, index_reg = 0, base_reg = 0, scale, rip_relative = 0;
	int no_wb = 0;
	u64 msr_data;

	/* Shadow copy of register state. Committed on successful emulation. */
	unsigned long _regs[NR_VCPU_REGS];
	unsigned long _eip = ctxt->vcpu->rip, _eflags = ctxt->eflags;
	unsigned long modrm_val = 0;

	memcpy(_regs, ctxt->vcpu->regs, sizeof _regs);

	switch (mode) {
	case X86EMUL_MODE_REAL:
	case X86EMUL_MODE_PROT16:
		op_bytes = ad_bytes = 2;
		break;
	case X86EMUL_MODE_PROT32:
		op_bytes = ad_bytes = 4;
		break;
#ifdef CONFIG_X86_64
	case X86EMUL_MODE_PROT64:
		op_bytes = 4;
		ad_bytes = 8;
		break;
#endif
	default:
		return -1;
	}

	/* Legacy prefixes. */
	for (i = 0; i < 8; i++) {
		switch (b = insn_fetch(u8, 1, _eip)) {
		case 0x66:	/* operand-size override */
			op_bytes ^= 6;	/* switch between 2/4 bytes */
			break;
		case 0x67:	/* address-size override */
			if (mode == X86EMUL_MODE_PROT64)
				ad_bytes ^= 12;	/* switch between 4/8 bytes */
			else
				ad_bytes ^= 6;	/* switch between 2/4 bytes */
			break;
		case 0x2e:	/* CS override */
			override_base = &ctxt->cs_base;
			break;
		case 0x3e:	/* DS override */
			override_base = &ctxt->ds_base;
			break;
		case 0x26:	/* ES override */
			override_base = &ctxt->es_base;
			break;
		case 0x64:	/* FS override */
			override_base = &ctxt->fs_base;
			break;
		case 0x65:	/* GS override */
			override_base = &ctxt->gs_base;
			break;
		case 0x36:	/* SS override */
			override_base = &ctxt->ss_base;
			break;
		case 0xf0:	/* LOCK */
			lock_prefix = 1;
			break;
		case 0xf2:	/* REPNE/REPNZ */
		case 0xf3:	/* REP/REPE/REPZ */
			rep_prefix = 1;
			break;
		default:
			goto done_prefixes;
		}
	}

done_prefixes:

	/* REX prefix. */
	if ((mode == X86EMUL_MODE_PROT64) && ((b & 0xf0) == 0x40)) {
		rex_prefix = b;
		if (b & 8)
			op_bytes = 8;	/* REX.W */
		modrm_reg = (b & 4) << 1;	/* REX.R */
		index_reg = (b & 2) << 2; /* REX.X */
		modrm_rm = base_reg = (b & 1) << 3; /* REG.B */
		b = insn_fetch(u8, 1, _eip);
	}

	/* Opcode byte(s). */
	d = opcode_table[b];
	if (d == 0) {
		/* Two-byte opcode? */
		if (b == 0x0f) {
			twobyte = 1;
			b = insn_fetch(u8, 1, _eip);
			d = twobyte_table[b];
		}

		/* Unrecognised? */
		if (d == 0)
			goto cannot_emulate;
	}

	/* ModRM and SIB bytes. */
	if (d & ModRM) {
		modrm = insn_fetch(u8, 1, _eip);
		modrm_mod |= (modrm & 0xc0) >> 6;
		modrm_reg |= (modrm & 0x38) >> 3;
		modrm_rm |= (modrm & 0x07);
		modrm_ea = 0;
		use_modrm_ea = 1;

		if (modrm_mod == 3) {
			modrm_val = *(unsigned long *)
				decode_register(modrm_rm, _regs, d & ByteOp);
			goto modrm_done;
		}

		if (ad_bytes == 2) {
			unsigned bx = _regs[VCPU_REGS_RBX];
			unsigned bp = _regs[VCPU_REGS_RBP];
			unsigned si = _regs[VCPU_REGS_RSI];
			unsigned di = _regs[VCPU_REGS_RDI];

			/* 16-bit ModR/M decode. */
			switch (modrm_mod) {
			case 0:
				if (modrm_rm == 6)
					modrm_ea += insn_fetch(u16, 2, _eip);
				break;
			case 1:
				modrm_ea += insn_fetch(s8, 1, _eip);
				break;
			case 2:
				modrm_ea += insn_fetch(u16, 2, _eip);
				break;
			}
			switch (modrm_rm) {
			case 0:
				modrm_ea += bx + si;
				break;
			case 1:
				modrm_ea += bx + di;
				break;
			case 2:
				modrm_ea += bp + si;
				break;
			case 3:
				modrm_ea += bp + di;
				break;
			case 4:
				modrm_ea += si;
				break;
			case 5:
				modrm_ea += di;
				break;
			case 6:
				if (modrm_mod != 0)
					modrm_ea += bp;
				break;
			case 7:
				modrm_ea += bx;
				break;
			}
			if (modrm_rm == 2 || modrm_rm == 3 ||
			    (modrm_rm == 6 && modrm_mod != 0))
				if (!override_base)
					override_base = &ctxt->ss_base;
			modrm_ea = (u16)modrm_ea;
		} else {
			/* 32/64-bit ModR/M decode. */
			switch (modrm_rm) {
			case 4:
			case 12:
				sib = insn_fetch(u8, 1, _eip);
				index_reg |= (sib >> 3) & 7;
				base_reg |= sib & 7;
				scale = sib >> 6;

				switch (base_reg) {
				case 5:
					if (modrm_mod != 0)
						modrm_ea += _regs[base_reg];
					else
						modrm_ea += insn_fetch(s32, 4, _eip);
					break;
				default:
					modrm_ea += _regs[base_reg];
				}
				switch (index_reg) {
				case 4:
					break;
				default:
					modrm_ea += _regs[index_reg] << scale;

				}
				break;
			case 5:
				if (modrm_mod != 0)
					modrm_ea += _regs[modrm_rm];
				else if (mode == X86EMUL_MODE_PROT64)
					rip_relative = 1;
				break;
			default:
				modrm_ea += _regs[modrm_rm];
				break;
			}
			switch (modrm_mod) {
			case 0:
				if (modrm_rm == 5)
					modrm_ea += insn_fetch(s32, 4, _eip);
				break;
			case 1:
				modrm_ea += insn_fetch(s8, 1, _eip);
				break;
			case 2:
				modrm_ea += insn_fetch(s32, 4, _eip);
				break;
			}
		}
		if (!override_base)
			override_base = &ctxt->ds_base;
		if (mode == X86EMUL_MODE_PROT64 &&
		    override_base != &ctxt->fs_base &&
		    override_base != &ctxt->gs_base)
			override_base = NULL;

		if (override_base)
			modrm_ea += *override_base;

		if (rip_relative) {
			modrm_ea += _eip;
			switch (d & SrcMask) {
			case SrcImmByte:
				modrm_ea += 1;
				break;
			case SrcImm:
				if (d & ByteOp)
					modrm_ea += 1;
				else
					if (op_bytes == 8)
						modrm_ea += 4;
					else
						modrm_ea += op_bytes;
			}
		}
		if (ad_bytes != 8)
			modrm_ea = (u32)modrm_ea;
		cr2 = modrm_ea;
	modrm_done:
		;
	}

	/*
	 * Decode and fetch the source operand: register, memory
	 * or immediate.
	 */
	switch (d & SrcMask) {
	case SrcNone:
		break;
	case SrcReg:
		src.type = OP_REG;
		if (d & ByteOp) {
			src.ptr = decode_register(modrm_reg, _regs,
						  (rex_prefix == 0));
			src.val = src.orig_val = *(u8 *) src.ptr;
			src.bytes = 1;
		} else {
			src.ptr = decode_register(modrm_reg, _regs, 0);
			switch ((src.bytes = op_bytes)) {
			case 2:
				src.val = src.orig_val = *(u16 *) src.ptr;
				break;
			case 4:
				src.val = src.orig_val = *(u32 *) src.ptr;
				break;
			case 8:
				src.val = src.orig_val = *(u64 *) src.ptr;
				break;
			}
		}
		break;
	case SrcMem16:
		src.bytes = 2;
		goto srcmem_common;
	case SrcMem32:
		src.bytes = 4;
		goto srcmem_common;
	case SrcMem:
		src.bytes = (d & ByteOp) ? 1 : op_bytes;
		/* Don't fetch the address for invlpg: it could be unmapped. */
		if (twobyte && b == 0x01 && modrm_reg == 7)
			break;
	      srcmem_common:
		/*
		 * For instructions with a ModR/M byte, switch to register
		 * access if Mod = 3.
		 */
		if ((d & ModRM) && modrm_mod == 3) {
			src.type = OP_REG;
			break;
		}
		src.type = OP_MEM;
		src.ptr = (unsigned long *)cr2;
		src.val = 0;
		if ((rc = ops->read_emulated((unsigned long)src.ptr,
					     &src.val, src.bytes, ctxt->vcpu)) != 0)
			goto done;
		src.orig_val = src.val;
		break;
	case SrcImm:
		src.type = OP_IMM;
		src.ptr = (unsigned long *)_eip;
		src.bytes = (d & ByteOp) ? 1 : op_bytes;
		if (src.bytes == 8)
			src.bytes = 4;
		/* NB. Immediates are sign-extended as necessary. */
		switch (src.bytes) {
		case 1:
			src.val = insn_fetch(s8, 1, _eip);
			break;
		case 2:
			src.val = insn_fetch(s16, 2, _eip);
			break;
		case 4:
			src.val = insn_fetch(s32, 4, _eip);
			break;
		}
		break;
	case SrcImmByte:
		src.type = OP_IMM;
		src.ptr = (unsigned long *)_eip;
		src.bytes = 1;
		src.val = insn_fetch(s8, 1, _eip);
		break;
	}

	/* Decode and fetch the destination operand: register or memory. */
	switch (d & DstMask) {
	case ImplicitOps:
		/* Special instructions do their own operand decoding. */
		goto special_insn;
	case DstReg:
		dst.type = OP_REG;
		if ((d & ByteOp)
		    && !(twobyte && (b == 0xb6 || b == 0xb7))) {
			dst.ptr = decode_register(modrm_reg, _regs,
						  (rex_prefix == 0));
			dst.val = *(u8 *) dst.ptr;
			dst.bytes = 1;
		} else {
			dst.ptr = decode_register(modrm_reg, _regs, 0);
			switch ((dst.bytes = op_bytes)) {
			case 2:
				dst.val = *(u16 *)dst.ptr;
				break;
			case 4:
				dst.val = *(u32 *)dst.ptr;
				break;
			case 8:
				dst.val = *(u64 *)dst.ptr;
				break;
			}
		}
		break;
	case DstMem:
		dst.type = OP_MEM;
		dst.ptr = (unsigned long *)cr2;
		dst.bytes = (d & ByteOp) ? 1 : op_bytes;
		dst.val = 0;
		/*
		 * For instructions with a ModR/M byte, switch to register
		 * access if Mod = 3.
		 */
		if ((d & ModRM) && modrm_mod == 3) {
			dst.type = OP_REG;
			break;
		}
		if (d & BitOp) {
			unsigned long mask = ~(dst.bytes * 8 - 1);

			dst.ptr = (void *)dst.ptr + (src.val & mask) / 8;
		}
		if (!(d & Mov) && /* optimisation - avoid slow emulated read */
		    ((rc = ops->read_emulated((unsigned long)dst.ptr,
					      &dst.val, dst.bytes, ctxt->vcpu)) != 0))
			goto done;
		break;
	}
	dst.orig_val = dst.val;

	if (twobyte)
		goto twobyte_insn;

	switch (b) {
	case 0x00 ... 0x05:
	      add:		/* add */
		emulate_2op_SrcV("add", src, dst, _eflags);
		break;
	case 0x08 ... 0x0d:
	      or:		/* or */
		emulate_2op_SrcV("or", src, dst, _eflags);
		break;
	case 0x10 ... 0x15:
	      adc:		/* adc */
		emulate_2op_SrcV("adc", src, dst, _eflags);
		break;
	case 0x18 ... 0x1d:
	      sbb:		/* sbb */
		emulate_2op_SrcV("sbb", src, dst, _eflags);
		break;
	case 0x20 ... 0x23:
	      and:		/* and */
		emulate_2op_SrcV("and", src, dst, _eflags);
		break;
	case 0x24:              /* and al imm8 */
		dst.type = OP_REG;
		dst.ptr = &_regs[VCPU_REGS_RAX];
		dst.val = *(u8 *)dst.ptr;
		dst.bytes = 1;
		dst.orig_val = dst.val;
		goto and;
	case 0x25:              /* and ax imm16, or eax imm32 */
		dst.type = OP_REG;
		dst.bytes = op_bytes;
		dst.ptr = &_regs[VCPU_REGS_RAX];
		if (op_bytes == 2)
			dst.val = *(u16 *)dst.ptr;
		else
			dst.val = *(u32 *)dst.ptr;
		dst.orig_val = dst.val;
		goto and;
	case 0x28 ... 0x2d:
	      sub:		/* sub */
		emulate_2op_SrcV("sub", src, dst, _eflags);
		break;
	case 0x30 ... 0x35:
	      xor:		/* xor */
		emulate_2op_SrcV("xor", src, dst, _eflags);
		break;
	case 0x38 ... 0x3d:
	      cmp:		/* cmp */
		emulate_2op_SrcV("cmp", src, dst, _eflags);
		break;
	case 0x63:		/* movsxd */
		if (mode != X86EMUL_MODE_PROT64)
			goto cannot_emulate;
		dst.val = (s32) src.val;
		break;
	case 0x80 ... 0x83:	/* Grp1 */
		switch (modrm_reg) {
		case 0:
			goto add;
		case 1:
			goto or;
		case 2:
			goto adc;
		case 3:
			goto sbb;
		case 4:
			goto and;
		case 5:
			goto sub;
		case 6:
			goto xor;
		case 7:
			goto cmp;
		}
		break;
	case 0x84 ... 0x85:
	      test:		/* test */
		emulate_2op_SrcV("test", src, dst, _eflags);
		break;
	case 0x86 ... 0x87:	/* xchg */
		/* Write back the register source. */
		switch (dst.bytes) {
		case 1:
			*(u8 *) src.ptr = (u8) dst.val;
			break;
		case 2:
			*(u16 *) src.ptr = (u16) dst.val;
			break;
		case 4:
			*src.ptr = (u32) dst.val;
			break;	/* 64b reg: zero-extend */
		case 8:
			*src.ptr = dst.val;
			break;
		}
		/*
		 * Write back the memory destination with implicit LOCK
		 * prefix.
		 */
		dst.val = src.val;
		lock_prefix = 1;
		break;
	case 0x88 ... 0x8b:	/* mov */
		goto mov;
	case 0x8d: /* lea r16/r32, m */
		dst.val = modrm_val;
		break;
	case 0x8f:		/* pop (sole member of Grp1a) */
		/* 64-bit mode: POP always pops a 64-bit operand. */
		if (mode == X86EMUL_MODE_PROT64)
			dst.bytes = 8;
		if ((rc = ops->read_std(register_address(ctxt->ss_base,
							 _regs[VCPU_REGS_RSP]),
					&dst.val, dst.bytes, ctxt->vcpu)) != 0)
			goto done;
		register_address_increment(_regs[VCPU_REGS_RSP], dst.bytes);
		break;
	case 0xa0 ... 0xa1:	/* mov */
		dst.ptr = (unsigned long *)&_regs[VCPU_REGS_RAX];
		dst.val = src.val;
		_eip += ad_bytes;	/* skip src displacement */
		break;
	case 0xa2 ... 0xa3:	/* mov */
		dst.val = (unsigned long)_regs[VCPU_REGS_RAX];
		_eip += ad_bytes;	/* skip dst displacement */
		break;
	case 0xc0 ... 0xc1:
	      grp2:		/* Grp2 */
		switch (modrm_reg) {
		case 0:	/* rol */
			emulate_2op_SrcB("rol", src, dst, _eflags);
			break;
		case 1:	/* ror */
			emulate_2op_SrcB("ror", src, dst, _eflags);
			break;
		case 2:	/* rcl */
			emulate_2op_SrcB("rcl", src, dst, _eflags);
			break;
		case 3:	/* rcr */
			emulate_2op_SrcB("rcr", src, dst, _eflags);
			break;
		case 4:	/* sal/shl */
		case 6:	/* sal/shl */
			emulate_2op_SrcB("sal", src, dst, _eflags);
			break;
		case 5:	/* shr */
			emulate_2op_SrcB("shr", src, dst, _eflags);
			break;
		case 7:	/* sar */
			emulate_2op_SrcB("sar", src, dst, _eflags);
			break;
		}
		break;
	case 0xc6 ... 0xc7:	/* mov (sole member of Grp11) */
	mov:
		dst.val = src.val;
		break;
	case 0xd0 ... 0xd1:	/* Grp2 */
		src.val = 1;
		goto grp2;
	case 0xd2 ... 0xd3:	/* Grp2 */
		src.val = _regs[VCPU_REGS_RCX];
		goto grp2;
	case 0xf6 ... 0xf7:	/* Grp3 */
		switch (modrm_reg) {
		case 0 ... 1:	/* test */
			/*
			 * Special case in Grp3: test has an immediate
			 * source operand.
			 */
			src.type = OP_IMM;
			src.ptr = (unsigned long *)_eip;
			src.bytes = (d & ByteOp) ? 1 : op_bytes;
			if (src.bytes == 8)
				src.bytes = 4;
			switch (src.bytes) {
			case 1:
				src.val = insn_fetch(s8, 1, _eip);
				break;
			case 2:
				src.val = insn_fetch(s16, 2, _eip);
				break;
			case 4:
				src.val = insn_fetch(s32, 4, _eip);
				break;
			}
			goto test;
		case 2:	/* not */
			dst.val = ~dst.val;
			break;
		case 3:	/* neg */
			emulate_1op("neg", dst, _eflags);
			break;
		default:
			goto cannot_emulate;
		}
		break;
	case 0xfe ... 0xff:	/* Grp4/Grp5 */
		switch (modrm_reg) {
		case 0:	/* inc */
			emulate_1op("inc", dst, _eflags);
			break;
		case 1:	/* dec */
			emulate_1op("dec", dst, _eflags);
			break;
		case 4: /* jmp abs */
			if (b == 0xff)
				_eip = dst.val;
			else
				goto cannot_emulate;
			break;
		case 6:	/* push */
			/* 64-bit mode: PUSH always pushes a 64-bit operand. */
			if (mode == X86EMUL_MODE_PROT64) {
				dst.bytes = 8;
				if ((rc = ops->read_std((unsigned long)dst.ptr,
							&dst.val, 8,
							ctxt->vcpu)) != 0)
					goto done;
			}
			register_address_increment(_regs[VCPU_REGS_RSP],
						   -dst.bytes);
			if ((rc = ops->write_emulated(
				     register_address(ctxt->ss_base,
						      _regs[VCPU_REGS_RSP]),
				     &dst.val, dst.bytes, ctxt->vcpu)) != 0)
				goto done;
			no_wb = 1;
			break;
		default:
			goto cannot_emulate;
		}
		break;
	}

writeback:
	if (!no_wb) {
		switch (dst.type) {
		case OP_REG:
			/* The 4-byte case *is* correct: in 64-bit mode we zero-extend. */
			switch (dst.bytes) {
			case 1:
				*(u8 *)dst.ptr = (u8)dst.val;
				break;
			case 2:
				*(u16 *)dst.ptr = (u16)dst.val;
				break;
			case 4:
				*dst.ptr = (u32)dst.val;
				break;	/* 64b: zero-ext */
			case 8:
				*dst.ptr = dst.val;
				break;
			}
			break;
		case OP_MEM:
			if (lock_prefix)
				rc = ops->cmpxchg_emulated((unsigned long)dst.
							   ptr, &dst.orig_val,
							   &dst.val, dst.bytes,
							   ctxt->vcpu);
			else
				rc = ops->write_emulated((unsigned long)dst.ptr,
							 &dst.val, dst.bytes,
							 ctxt->vcpu);
			if (rc != 0)
				goto done;
		default:
			break;
		}
	}

	/* Commit shadow register state. */
	memcpy(ctxt->vcpu->regs, _regs, sizeof _regs);
	ctxt->eflags = _eflags;
	ctxt->vcpu->rip = _eip;

done:
	return (rc == X86EMUL_UNHANDLEABLE) ? -1 : 0;

special_insn:
	if (twobyte)
		goto twobyte_special_insn;
	switch(b) {
	case 0x50 ... 0x57:  /* push reg */
		if (op_bytes == 2)
			src.val = (u16) _regs[b & 0x7];
		else
			src.val = (u32) _regs[b & 0x7];
		dst.type  = OP_MEM;
		dst.bytes = op_bytes;
		dst.val = src.val;
		register_address_increment(_regs[VCPU_REGS_RSP], -op_bytes);
		dst.ptr = (void *) register_address(
			ctxt->ss_base, _regs[VCPU_REGS_RSP]);
		break;
	case 0x58 ... 0x5f: /* pop reg */
		dst.ptr = (unsigned long *)&_regs[b & 0x7];
	pop_instruction:
		if ((rc = ops->read_std(register_address(ctxt->ss_base,
			_regs[VCPU_REGS_RSP]), dst.ptr, op_bytes, ctxt->vcpu))
			!= 0)
			goto done;

		register_address_increment(_regs[VCPU_REGS_RSP], op_bytes);
		no_wb = 1; /* Disable writeback. */
		break;
	case 0x6a: /* push imm8 */
		src.val = 0L;
		src.val = insn_fetch(s8, 1, _eip);
	push:
		dst.type  = OP_MEM;
		dst.bytes = op_bytes;
		dst.val = src.val;
		register_address_increment(_regs[VCPU_REGS_RSP], -op_bytes);
		dst.ptr = (void *) register_address(ctxt->ss_base,
							_regs[VCPU_REGS_RSP]);
		break;
	case 0x6c:		/* insb */
	case 0x6d:		/* insw/insd */
		 if (kvm_emulate_pio_string(ctxt->vcpu, NULL,
				1, 					/* in */
				(d & ByteOp) ? 1 : op_bytes, 		/* size */
				rep_prefix ?
				address_mask(_regs[VCPU_REGS_RCX]) : 1,	/* count */
				(_eflags & EFLG_DF),			/* down */
				register_address(ctxt->es_base,
						 _regs[VCPU_REGS_RDI]),	/* address */
				rep_prefix,
				_regs[VCPU_REGS_RDX]			/* port */
				) == 0)
			return -1;
		return 0;
	case 0x6e:		/* outsb */
	case 0x6f:		/* outsw/outsd */
		if (kvm_emulate_pio_string(ctxt->vcpu, NULL,
				0, 					/* in */
				(d & ByteOp) ? 1 : op_bytes, 		/* size */
				rep_prefix ?
				address_mask(_regs[VCPU_REGS_RCX]) : 1,	/* count */
				(_eflags & EFLG_DF),			/* down */
				register_address(override_base ?
						 *override_base : ctxt->ds_base,
						 _regs[VCPU_REGS_RSI]),	/* address */
				rep_prefix,
				_regs[VCPU_REGS_RDX]			/* port */
				) == 0)
			return -1;
		return 0;
	case 0x70 ... 0x7f: /* jcc (short) */ {
		int rel = insn_fetch(s8, 1, _eip);

		if (test_cc(b, _eflags))
		JMP_REL(rel);
		break;
	}
	case 0x9c: /* pushf */
		src.val =  (unsigned long) _eflags;
		goto push;
	case 0x9d: /* popf */
		dst.ptr = (unsigned long *) &_eflags;
		goto pop_instruction;
	case 0xc3: /* ret */
		dst.ptr = &_eip;
		goto pop_instruction;
	case 0xf4:              /* hlt */
		ctxt->vcpu->halt_request = 1;
		goto done;
	}
	if (rep_prefix) {
		if (_regs[VCPU_REGS_RCX] == 0) {
			ctxt->vcpu->rip = _eip;
			goto done;
		}
		_regs[VCPU_REGS_RCX]--;
		_eip = ctxt->vcpu->rip;
	}
	switch (b) {
	case 0xa4 ... 0xa5:	/* movs */
		dst.type = OP_MEM;
		dst.bytes = (d & ByteOp) ? 1 : op_bytes;
		dst.ptr = (unsigned long *)register_address(ctxt->es_base,
							_regs[VCPU_REGS_RDI]);
		if ((rc = ops->read_emulated(register_address(
		      override_base ? *override_base : ctxt->ds_base,
		      _regs[VCPU_REGS_RSI]), &dst.val, dst.bytes, ctxt->vcpu)) != 0)
			goto done;
		register_address_increment(_regs[VCPU_REGS_RSI],
			     (_eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
		register_address_increment(_regs[VCPU_REGS_RDI],
			     (_eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
		break;
	case 0xa6 ... 0xa7:	/* cmps */
		DPRINTF("Urk! I don't handle CMPS.\n");
		goto cannot_emulate;
	case 0xaa ... 0xab:	/* stos */
		dst.type = OP_MEM;
		dst.bytes = (d & ByteOp) ? 1 : op_bytes;
		dst.ptr = (unsigned long *)cr2;
		dst.val = _regs[VCPU_REGS_RAX];
		register_address_increment(_regs[VCPU_REGS_RDI],
			     (_eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
		break;
	case 0xac ... 0xad:	/* lods */
		dst.type = OP_REG;
		dst.bytes = (d & ByteOp) ? 1 : op_bytes;
		dst.ptr = (unsigned long *)&_regs[VCPU_REGS_RAX];
		if ((rc = ops->read_emulated(cr2, &dst.val, dst.bytes,
					     ctxt->vcpu)) != 0)
			goto done;
		register_address_increment(_regs[VCPU_REGS_RSI],
			   (_eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
		break;
	case 0xae ... 0xaf:	/* scas */
		DPRINTF("Urk! I don't handle SCAS.\n");
		goto cannot_emulate;
	case 0xe8: /* call (near) */ {
		long int rel;
		switch (op_bytes) {
		case 2:
			rel = insn_fetch(s16, 2, _eip);
			break;
		case 4:
			rel = insn_fetch(s32, 4, _eip);
			break;
		case 8:
			rel = insn_fetch(s64, 8, _eip);
			break;
		default:
			DPRINTF("Call: Invalid op_bytes\n");
			goto cannot_emulate;
		}
		src.val = (unsigned long) _eip;
		JMP_REL(rel);
		op_bytes = ad_bytes;
		goto push;
	}
	case 0xe9: /* jmp rel */
	case 0xeb: /* jmp rel short */
		JMP_REL(src.val);
		no_wb = 1; /* Disable writeback. */
		break;


	}
	goto writeback;

twobyte_insn:
	switch (b) {
	case 0x01: /* lgdt, lidt, lmsw */
		/* Disable writeback. */
		no_wb = 1;
		switch (modrm_reg) {
			u16 size;
			unsigned long address;

		case 2: /* lgdt */
			rc = read_descriptor(ctxt, ops, src.ptr,
					     &size, &address, op_bytes);
			if (rc)
				goto done;
			realmode_lgdt(ctxt->vcpu, size, address);
			break;
		case 3: /* lidt */
			rc = read_descriptor(ctxt, ops, src.ptr,
					     &size, &address, op_bytes);
			if (rc)
				goto done;
			realmode_lidt(ctxt->vcpu, size, address);
			break;
		case 4: /* smsw */
			if (modrm_mod != 3)
				goto cannot_emulate;
			*(u16 *)&_regs[modrm_rm]
				= realmode_get_cr(ctxt->vcpu, 0);
			break;
		case 6: /* lmsw */
			if (modrm_mod != 3)
				goto cannot_emulate;
			realmode_lmsw(ctxt->vcpu, (u16)modrm_val, &_eflags);
			break;
		case 7: /* invlpg*/
			emulate_invlpg(ctxt->vcpu, cr2);
			break;
		default:
			goto cannot_emulate;
		}
		break;
	case 0x21: /* mov from dr to reg */
		no_wb = 1;
		if (modrm_mod != 3)
			goto cannot_emulate;
		rc = emulator_get_dr(ctxt, modrm_reg, &_regs[modrm_rm]);
		break;
	case 0x23: /* mov from reg to dr */
		no_wb = 1;
		if (modrm_mod != 3)
			goto cannot_emulate;
		rc = emulator_set_dr(ctxt, modrm_reg, _regs[modrm_rm]);
		break;
	case 0x40 ... 0x4f:	/* cmov */
		dst.val = dst.orig_val = src.val;
		no_wb = 1;
		/*
		 * First, assume we're decoding an even cmov opcode
		 * (lsb == 0).
		 */
		switch ((b & 15) >> 1) {
		case 0:	/* cmovo */
			no_wb = (_eflags & EFLG_OF) ? 0 : 1;
			break;
		case 1:	/* cmovb/cmovc/cmovnae */
			no_wb = (_eflags & EFLG_CF) ? 0 : 1;
			break;
		case 2:	/* cmovz/cmove */
			no_wb = (_eflags & EFLG_ZF) ? 0 : 1;
			break;
		case 3:	/* cmovbe/cmovna */
			no_wb = (_eflags & (EFLG_CF | EFLG_ZF)) ? 0 : 1;
			break;
		case 4:	/* cmovs */
			no_wb = (_eflags & EFLG_SF) ? 0 : 1;
			break;
		case 5:	/* cmovp/cmovpe */
			no_wb = (_eflags & EFLG_PF) ? 0 : 1;
			break;
		case 7:	/* cmovle/cmovng */
			no_wb = (_eflags & EFLG_ZF) ? 0 : 1;
			/* fall through */
		case 6:	/* cmovl/cmovnge */
			no_wb &= (!(_eflags & EFLG_SF) !=
			      !(_eflags & EFLG_OF)) ? 0 : 1;
			break;
		}
		/* Odd cmov opcodes (lsb == 1) have inverted sense. */
		no_wb ^= b & 1;
		break;
	case 0xa3:
	      bt:		/* bt */
		src.val &= (dst.bytes << 3) - 1; /* only subword offset */
		emulate_2op_SrcV_nobyte("bt", src, dst, _eflags);
		break;
	case 0xab:
	      bts:		/* bts */
		src.val &= (dst.bytes << 3) - 1; /* only subword offset */
		emulate_2op_SrcV_nobyte("bts", src, dst, _eflags);
		break;
	case 0xb0 ... 0xb1:	/* cmpxchg */
		/*
		 * Save real source value, then compare EAX against
		 * destination.
		 */
		src.orig_val = src.val;
		src.val = _regs[VCPU_REGS_RAX];
		emulate_2op_SrcV("cmp", src, dst, _eflags);
		if (_eflags & EFLG_ZF) {
			/* Success: write back to memory. */
			dst.val = src.orig_val;
		} else {
			/* Failure: write the value we saw to EAX. */
			dst.type = OP_REG;
			dst.ptr = (unsigned long *)&_regs[VCPU_REGS_RAX];
		}
		break;
	case 0xb3:
	      btr:		/* btr */
		src.val &= (dst.bytes << 3) - 1; /* only subword offset */
		emulate_2op_SrcV_nobyte("btr", src, dst, _eflags);
		break;
	case 0xb6 ... 0xb7:	/* movzx */
		dst.bytes = op_bytes;
		dst.val = (d & ByteOp) ? (u8) src.val : (u16) src.val;
		break;
	case 0xba:		/* Grp8 */
		switch (modrm_reg & 3) {
		case 0:
			goto bt;
		case 1:
			goto bts;
		case 2:
			goto btr;
		case 3:
			goto btc;
		}
		break;
	case 0xbb:
	      btc:		/* btc */
		src.val &= (dst.bytes << 3) - 1; /* only subword offset */
		emulate_2op_SrcV_nobyte("btc", src, dst, _eflags);
		break;
	case 0xbe ... 0xbf:	/* movsx */
		dst.bytes = op_bytes;
		dst.val = (d & ByteOp) ? (s8) src.val : (s16) src.val;
		break;
	case 0xc3:		/* movnti */
		dst.bytes = op_bytes;
		dst.val = (op_bytes == 4) ? (u32) src.val : (u64) src.val;
		break;
	}
	goto writeback;

twobyte_special_insn:
	/* Disable writeback. */
	no_wb = 1;
	switch (b) {
	case 0x06:
		emulate_clts(ctxt->vcpu);
		break;
	case 0x08:		/* invd */
		break;
	case 0x09:		/* wbinvd */
		break;
	case 0x0d:		/* GrpP (prefetch) */
	case 0x18:		/* Grp16 (prefetch/nop) */
		break;
	case 0x20: /* mov cr, reg */
		if (modrm_mod != 3)
			goto cannot_emulate;
		_regs[modrm_rm] = realmode_get_cr(ctxt->vcpu, modrm_reg);
		break;
	case 0x22: /* mov reg, cr */
		if (modrm_mod != 3)
			goto cannot_emulate;
		realmode_set_cr(ctxt->vcpu, modrm_reg, modrm_val, &_eflags);
		break;
	case 0x30:
		/* wrmsr */
		msr_data = (u32)_regs[VCPU_REGS_RAX]
			| ((u64)_regs[VCPU_REGS_RDX] << 32);
		rc = kvm_set_msr(ctxt->vcpu, _regs[VCPU_REGS_RCX], msr_data);
		if (rc) {
			kvm_x86_ops->inject_gp(ctxt->vcpu, 0);
			_eip = ctxt->vcpu->rip;
		}
		rc = X86EMUL_CONTINUE;
		break;
	case 0x32:
		/* rdmsr */
		rc = kvm_get_msr(ctxt->vcpu, _regs[VCPU_REGS_RCX], &msr_data);
		if (rc) {
			kvm_x86_ops->inject_gp(ctxt->vcpu, 0);
			_eip = ctxt->vcpu->rip;
		} else {
			_regs[VCPU_REGS_RAX] = (u32)msr_data;
			_regs[VCPU_REGS_RDX] = msr_data >> 32;
		}
		rc = X86EMUL_CONTINUE;
		break;
	case 0x80 ... 0x8f: /* jnz rel, etc*/ {
		long int rel;

		switch (op_bytes) {
		case 2:
			rel = insn_fetch(s16, 2, _eip);
			break;
		case 4:
			rel = insn_fetch(s32, 4, _eip);
			break;
		case 8:
			rel = insn_fetch(s64, 8, _eip);
			break;
		default:
			DPRINTF("jnz: Invalid op_bytes\n");
			goto cannot_emulate;
		}
		if (test_cc(b, _eflags))
			JMP_REL(rel);
		break;
	}
	case 0xc7:		/* Grp9 (cmpxchg8b) */
		{
			u64 old, new;
			if ((rc = ops->read_emulated(cr2, &old, 8, ctxt->vcpu))
									!= 0)
				goto done;
			if (((u32) (old >> 0) != (u32) _regs[VCPU_REGS_RAX]) ||
			    ((u32) (old >> 32) != (u32) _regs[VCPU_REGS_RDX])) {
				_regs[VCPU_REGS_RAX] = (u32) (old >> 0);
				_regs[VCPU_REGS_RDX] = (u32) (old >> 32);
				_eflags &= ~EFLG_ZF;
			} else {
				new = ((u64)_regs[VCPU_REGS_RCX] << 32)
					| (u32) _regs[VCPU_REGS_RBX];
				if ((rc = ops->cmpxchg_emulated(cr2, &old,
							  &new, 8, ctxt->vcpu)) != 0)
					goto done;
				_eflags |= EFLG_ZF;
			}
			break;
		}
	}
	goto writeback;

cannot_emulate:
	DPRINTF("Cannot emulate %02x\n", b);
	return -1;
}

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