/*      $OpenBSD: mmio.h,v 1.2 2024/07/09 09:31:37 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>

/* 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_ */