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vmd(8): import mmio decode and emulation, disabled for now.

The initial mmio support for vmd adds support for only specific MOV
and MOVZX instructions. Plan is to begin iterating in-tree on other
missing pieces. All functionality is gated behind an #if for now.

Only change to vmm(4) is reordering register #define's in vmmvar.h.

ok mlarkin@

/*	$OpenBSD: mmio.h,v 1.1 2022/11/10 11:46:39 dv Exp $	*/

/*
 * Copyright (c) 2022 Dave Voutila <dv@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#ifndef _MMIO_H_
#define _MMIO_H_

#include <sys/types.h>
#include <machine/vmmvar.h>

/* Code segment bits  */
#define CS_L		(1 << 13)
#define CS_D		(1 << 14)

#define EFLAGS_VM	(1 << 17)	/* Virtual 8086 Mode enabled */

/* Instruction Prefixes (SDM Vol 2, 2.1.1) */
#define LEG_1_LOCK	0xF0
#define LEG_1_REPNE	0xF2
#define LEG_1_REP	0xF3
#define LEG_2_CS	0x2E
#define LEG_2_SS	0x36
#define LEG_2_DS	0x3E
#define LEG_2_ES	0x26
#define LEG_2_FS	0x64
#define LEG_2_GS	0x65
#define LEG_3_OPSZ	0x66		/* Operand size override */
#define LEG_4_ADDRSZ	0x67		/* Address size override */

/* REX prefix bit fields */
#define REX_B		0x01
#define REX_X		0x02
#define REX_R		0x04
#define REX_W		0x08
#define REX_BASE	0x40

#define REX_NONE	0x00

/* VEX prefixes (unsupported) */
#define VEX_2_BYTE	0xC5
#define VEX_3_BYTE	0xC4

#define ESCAPE		0x0F

struct x86_prefix {
	uint8_t		pfx_group1;	/* LOCK, REP, or REPNE */
	uint8_t		pfx_group2;	/* Segment overrides */
	uint8_t		pfx_group3;	/* Operand size override */
	uint8_t		pfx_group4;	/* Address size override */
	uint8_t		pfx_rex;	/* REX prefix for long mode */
};

enum x86_opcode_type {
	OP_UNKNOWN = 0,		/* Default value when undecoded. */
	OP_IN,
	OP_INS,
	OP_MOV,
	OP_MOVZX,
	OP_OUT,
	OP_OUTS,
	OP_TWO_BYTE,		/* Opcode is two bytes, not one. */
	OP_UNSUPPORTED,		/* Valid decode, but no current support. */
};

/* Instruction Operand Encoding as described in the SDM Vol 2, Ch 3-5. */
enum x86_operand_enc {
	OP_ENC_UNKNOWN = 0,
	OP_ENC_I,		/* Only immediate operand */
	OP_ENC_MI,		/* Immediate to ModRM */
	OP_ENC_MR,		/* Register to ModRM */
	OP_ENC_RM,		/* ModRm to Register */
	OP_ENC_FD,		/* Value @ segment offset to RAX */
	OP_ENC_TD,		/* RAX to segment offset */
	OP_ENC_OI,		/* Immediate to Register (no emul. needed!) */
	OP_ENC_ZO,		/* No ModRM byte. */
};

/* Displacement bytes */
enum x86_disp_type {
	DISP_NONE = 0,
	DISP_0,
	DISP_1,
	DISP_2,			/* Requires Legacy prefix LEG_4_ADDRSZ */
	DISP_4,
};

struct x86_opcode {
	uint8_t			op_bytes[2];		/* VEX unsupported */
	uint8_t			op_bytes_len;		/* Length of opcode */
	enum x86_opcode_type	op_type;		/* Type of opcode */
	enum x86_operand_enc	op_encoding;		/* Operand encoding */
};

struct x86_insn {
	uint8_t			insn_bytes[15];		/* Original payload */
	uint8_t			insn_bytes_len;		/* Size of payload */
	int			insn_cpu_mode;		/* CPU mode */

	struct x86_prefix 	insn_prefix;		/* Combined prefixes */
	struct x86_opcode	insn_opcode;

	uint8_t			insn_modrm;		/* ModR/M */
#define MODRM_MOD(x)		((x >> 6) & 0x3)
#define MODRM_REGOP(x)		((x >> 3) & 0x7)
#define MODRM_RM(x)		((x >> 0) & 0x7)
	uint8_t			insn_modrm_valid;	/* Is ModR/M set? */

	vaddr_t			insn_gva;		/* Guest Virtual Addr */
	int			insn_reg;		/* Register */

	uint8_t			insn_sib;		/* Scale-Index-Base */
	uint8_t			insn_sib_valid;		/* SIB byte set? */

	uint64_t		insn_disp;		/* Displacement */
	enum x86_disp_type	insn_disp_type;

	uint64_t		insn_immediate;		/* Immediate data */
	uint8_t			insn_immediate_len;
};

int	insn_decode(struct vm_exit *, struct x86_insn *);
int	insn_emulate(struct vm_exit *, struct x86_insn *);

#endif /* _MMIO_H_ */