// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * x86 instruction analysis
 *
 * Copyright (C) IBM Corporation, 2002, 2004, 2009
 */

#include <linux/kernel.h>
#ifdef __KERNEL__
#include <linux/string.h>
#else
#include <string.h>
#endif
#include <asm/inat.h> /*__ignore_sync_check__ */
#include <asm/insn.h> /* __ignore_sync_check__ */

#include <linux/errno.h>
#include <linux/kconfig.h>

#include <asm/emulate_prefix.h> /* __ignore_sync_check__ */

#define leXX_to_cpu(t, r)                                               \
({                                                                      \
        __typeof__(t) v;                                                \
        switch (sizeof(t)) {                                            \
        case 4: v = le32_to_cpu(r); break;                              \
        case 2: v = le16_to_cpu(r); break;                              \
        case 1: v = r; break;                                           \
        default:                                                        \
                BUILD_BUG(); break;                                     \
        }                                                               \
        v;                                                              \
})

/* Verify next sizeof(t) bytes can be on the same instruction */
#define validate_next(t, insn, n)       \
        ((insn)->next_byte + sizeof(t) + n <= (insn)->end_kaddr)

#define __get_next(t, insn)     \
        ({ t r; memcpy(&r, insn->next_byte, sizeof(t)); insn->next_byte += sizeof(t); leXX_to_cpu(t, r); })

#define __peek_nbyte_next(t, insn, n)   \
        ({ t r; memcpy(&r, (insn)->next_byte + n, sizeof(t)); leXX_to_cpu(t, r); })

#define get_next(t, insn)       \
        ({ if (unlikely(!validate_next(t, insn, 0))) goto err_out; __get_next(t, insn); })

#define peek_nbyte_next(t, insn, n)     \
        ({ if (unlikely(!validate_next(t, insn, n))) goto err_out; __peek_nbyte_next(t, insn, n); })

#define peek_next(t, insn)      peek_nbyte_next(t, insn, 0)

/**
 * insn_init() - initialize struct insn
 * @insn:       &struct insn to be initialized
 * @kaddr:      address (in kernel memory) of instruction (or copy thereof)
 * @buf_len:    length of the insn buffer at @kaddr
 * @x86_64:     !0 for 64-bit kernel or 64-bit app
 */
void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64)
{
        /*
         * Instructions longer than MAX_INSN_SIZE (15 bytes) are invalid
         * even if the input buffer is long enough to hold them.
         */
        if (buf_len > MAX_INSN_SIZE)
                buf_len = MAX_INSN_SIZE;

        memset(insn, 0, sizeof(*insn));
        insn->kaddr = kaddr;
        insn->end_kaddr = kaddr + buf_len;
        insn->next_byte = kaddr;
        insn->x86_64 = x86_64 ? 1 : 0;
        insn->opnd_bytes = 4;
        if (x86_64)
                insn->addr_bytes = 8;
        else
                insn->addr_bytes = 4;
}

static const insn_byte_t xen_prefix[] = { __XEN_EMULATE_PREFIX };
static const insn_byte_t kvm_prefix[] = { __KVM_EMULATE_PREFIX };

static int __insn_get_emulate_prefix(struct insn *insn,
                                     const insn_byte_t *prefix, size_t len)
{
        size_t i;

        for (i = 0; i < len; i++) {
                if (peek_nbyte_next(insn_byte_t, insn, i) != prefix[i])
                        goto err_out;
        }

        insn->emulate_prefix_size = len;
        insn->next_byte += len;

        return 1;

err_out:
        return 0;
}

static void insn_get_emulate_prefix(struct insn *insn)
{
        if (__insn_get_emulate_prefix(insn, xen_prefix, sizeof(xen_prefix)))
                return;

        __insn_get_emulate_prefix(insn, kvm_prefix, sizeof(kvm_prefix));
}

/**
 * insn_get_prefixes - scan x86 instruction prefix bytes
 * @insn:       &struct insn containing instruction
 *
 * Populates the @insn->prefixes bitmap, and updates @insn->next_byte
 * to point to the (first) opcode.  No effect if @insn->prefixes.got
 * is already set.
 *
 * * Returns:
 * 0:  on success
 * < 0: on error
 */
int insn_get_prefixes(struct insn *insn)
{
        struct insn_field *prefixes = &insn->prefixes;
        insn_attr_t attr;
        insn_byte_t b, lb;
        int i, nb;

        if (prefixes->got)
                return 0;

        insn_get_emulate_prefix(insn);

        nb = 0;
        lb = 0;
        b = peek_next(insn_byte_t, insn);
        attr = inat_get_opcode_attribute(b);
        while (inat_is_legacy_prefix(attr)) {
                /* Skip if same prefix */
                for (i = 0; i < nb; i++)
                        if (prefixes->bytes[i] == b)
                                goto found;
                if (nb == 4)
                        /* Invalid instruction */
                        break;
                prefixes->bytes[nb++] = b;
                if (inat_is_address_size_prefix(attr)) {
                        /* address size switches 2/4 or 4/8 */
                        if (insn->x86_64)
                                insn->addr_bytes ^= 12;
                        else
                                insn->addr_bytes ^= 6;
                } else if (inat_is_operand_size_prefix(attr)) {
                        /* oprand size switches 2/4 */
                        insn->opnd_bytes ^= 6;
                }
found:
                prefixes->nbytes++;
                insn->next_byte++;
                lb = b;
                b = peek_next(insn_byte_t, insn);
                attr = inat_get_opcode_attribute(b);
        }
        /* Set the last prefix */
        if (lb && lb != insn->prefixes.bytes[3]) {
                if (unlikely(insn->prefixes.bytes[3])) {
                        /* Swap the last prefix */
                        b = insn->prefixes.bytes[3];
                        for (i = 0; i < nb; i++)
                                if (prefixes->bytes[i] == lb)
                                        insn_set_byte(prefixes, i, b);
                }
                insn_set_byte(&insn->prefixes, 3, lb);
        }

        /* Decode REX prefix */
        if (insn->x86_64) {
                b = peek_next(insn_byte_t, insn);
                attr = inat_get_opcode_attribute(b);
                if (inat_is_rex_prefix(attr)) {
                        insn_field_set(&insn->rex_prefix, b, 1);
                        insn->next_byte++;
                        if (X86_REX_W(b))
                                /* REX.W overrides opnd_size */
                                insn->opnd_bytes = 8;
                }
        }
        insn->rex_prefix.got = 1;

        /* Decode VEX prefix */
        b = peek_next(insn_byte_t, insn);
        attr = inat_get_opcode_attribute(b);
        if (inat_is_vex_prefix(attr)) {
                insn_byte_t b2 = peek_nbyte_next(insn_byte_t, insn, 1);
                if (!insn->x86_64) {
                        /*
                         * In 32-bits mode, if the [7:6] bits (mod bits of
                         * ModRM) on the second byte are not 11b, it is
                         * LDS or LES or BOUND.
                         */
                        if (X86_MODRM_MOD(b2) != 3)
                                goto vex_end;
                }
                insn_set_byte(&insn->vex_prefix, 0, b);
                insn_set_byte(&insn->vex_prefix, 1, b2);
                if (inat_is_evex_prefix(attr)) {
                        b2 = peek_nbyte_next(insn_byte_t, insn, 2);
                        insn_set_byte(&insn->vex_prefix, 2, b2);
                        b2 = peek_nbyte_next(insn_byte_t, insn, 3);
                        insn_set_byte(&insn->vex_prefix, 3, b2);
                        insn->vex_prefix.nbytes = 4;
                        insn->next_byte += 4;
                        if (insn->x86_64 && X86_VEX_W(b2))
                                /* VEX.W overrides opnd_size */
                                insn->opnd_bytes = 8;
                } else if (inat_is_vex3_prefix(attr)) {
                        b2 = peek_nbyte_next(insn_byte_t, insn, 2);
                        insn_set_byte(&insn->vex_prefix, 2, b2);
                        insn->vex_prefix.nbytes = 3;
                        insn->next_byte += 3;
                        if (insn->x86_64 && X86_VEX_W(b2))
                                /* VEX.W overrides opnd_size */
                                insn->opnd_bytes = 8;
                } else {
                        /*
                         * For VEX2, fake VEX3-like byte#2.
                         * Makes it easier to decode vex.W, vex.vvvv,
                         * vex.L and vex.pp. Masking with 0x7f sets vex.W == 0.
                         */
                        insn_set_byte(&insn->vex_prefix, 2, b2 & 0x7f);
                        insn->vex_prefix.nbytes = 2;
                        insn->next_byte += 2;
                }
        }
vex_end:
        insn->vex_prefix.got = 1;

        prefixes->got = 1;

        return 0;

err_out:
        return -ENODATA;
}

/**
 * insn_get_opcode - collect opcode(s)
 * @insn:       &struct insn containing instruction
 *
 * Populates @insn->opcode, updates @insn->next_byte to point past the
 * opcode byte(s), and set @insn->attr (except for groups).
 * If necessary, first collects any preceding (prefix) bytes.
 * Sets @insn->opcode.value = opcode1.  No effect if @insn->opcode.got
 * is already 1.
 *
 * Returns:
 * 0:  on success
 * < 0: on error
 */
int insn_get_opcode(struct insn *insn)
{
        struct insn_field *opcode = &insn->opcode;
        int pfx_id, ret;
        insn_byte_t op;

        if (opcode->got)
                return 0;

        if (!insn->prefixes.got) {
                ret = insn_get_prefixes(insn);
                if (ret)
                        return ret;
        }

        /* Get first opcode */
        op = get_next(insn_byte_t, insn);
        insn_set_byte(opcode, 0, op);
        opcode->nbytes = 1;

        /* Check if there is VEX prefix or not */
        if (insn_is_avx(insn)) {
                insn_byte_t m, p;
                m = insn_vex_m_bits(insn);
                p = insn_vex_p_bits(insn);
                insn->attr = inat_get_avx_attribute(op, m, p);
                if ((inat_must_evex(insn->attr) && !insn_is_evex(insn)) ||
                    (!inat_accept_vex(insn->attr) &&
                     !inat_is_group(insn->attr))) {
                        /* This instruction is bad */
                        insn->attr = 0;
                        return -EINVAL;
                }
                /* VEX has only 1 byte for opcode */
                goto end;
        }

        insn->attr = inat_get_opcode_attribute(op);
        while (inat_is_escape(insn->attr)) {
                /* Get escaped opcode */
                op = get_next(insn_byte_t, insn);
                opcode->bytes[opcode->nbytes++] = op;
                pfx_id = insn_last_prefix_id(insn);
                insn->attr = inat_get_escape_attribute(op, pfx_id, insn->attr);
        }

        if (inat_must_vex(insn->attr)) {
                /* This instruction is bad */
                insn->attr = 0;
                return -EINVAL;
        }
end:
        opcode->got = 1;
        return 0;

err_out:
        return -ENODATA;
}

/**
 * insn_get_modrm - collect ModRM byte, if any
 * @insn:       &struct insn containing instruction
 *
 * Populates @insn->modrm and updates @insn->next_byte to point past the
 * ModRM byte, if any.  If necessary, first collects the preceding bytes
 * (prefixes and opcode(s)).  No effect if @insn->modrm.got is already 1.
 *
 * Returns:
 * 0:  on success
 * < 0: on error
 */
int insn_get_modrm(struct insn *insn)
{
        struct insn_field *modrm = &insn->modrm;
        insn_byte_t pfx_id, mod;
        int ret;

        if (modrm->got)
                return 0;

        if (!insn->opcode.got) {
                ret = insn_get_opcode(insn);
                if (ret)
                        return ret;
        }

        if (inat_has_modrm(insn->attr)) {
                mod = get_next(insn_byte_t, insn);
                insn_field_set(modrm, mod, 1);
                if (inat_is_group(insn->attr)) {
                        pfx_id = insn_last_prefix_id(insn);
                        insn->attr = inat_get_group_attribute(mod, pfx_id,
                                                              insn->attr);
                        if (insn_is_avx(insn) && !inat_accept_vex(insn->attr)) {
                                /* Bad insn */
                                insn->attr = 0;
                                return -EINVAL;
                        }
                }
        }

        if (insn->x86_64 && inat_is_force64(insn->attr))
                insn->opnd_bytes = 8;

        modrm->got = 1;
        return 0;

err_out:
        return -ENODATA;
}


/**
 * insn_rip_relative() - Does instruction use RIP-relative addressing mode?
 * @insn:       &struct insn containing instruction
 *
 * If necessary, first collects the instruction up to and including the
 * ModRM byte.  No effect if @insn->x86_64 is 0.
 */
int insn_rip_relative(struct insn *insn)
{
        struct insn_field *modrm = &insn->modrm;
        int ret;

        if (!insn->x86_64)
                return 0;

        if (!modrm->got) {
                ret = insn_get_modrm(insn);
                if (ret)
                        return 0;
        }
        /*
         * For rip-relative instructions, the mod field (top 2 bits)
         * is zero and the r/m field (bottom 3 bits) is 0x5.
         */
        return (modrm->nbytes && (modrm->bytes[0] & 0xc7) == 0x5);
}

/**
 * insn_get_sib() - Get the SIB byte of instruction
 * @insn:       &struct insn containing instruction
 *
 * If necessary, first collects the instruction up to and including the
 * ModRM byte.
 *
 * Returns:
 * 0: if decoding succeeded
 * < 0: otherwise.
 */
int insn_get_sib(struct insn *insn)
{
        insn_byte_t modrm;
        int ret;

        if (insn->sib.got)
                return 0;

        if (!insn->modrm.got) {
                ret = insn_get_modrm(insn);
                if (ret)
                        return ret;
        }

        if (insn->modrm.nbytes) {
                modrm = insn->modrm.bytes[0];
                if (insn->addr_bytes != 2 &&
                    X86_MODRM_MOD(modrm) != 3 && X86_MODRM_RM(modrm) == 4) {
                        insn_field_set(&insn->sib,
                                       get_next(insn_byte_t, insn), 1);
                }
        }
        insn->sib.got = 1;

        return 0;

err_out:
        return -ENODATA;
}


/**
 * insn_get_displacement() - Get the displacement of instruction
 * @insn:       &struct insn containing instruction
 *
 * If necessary, first collects the instruction up to and including the
 * SIB byte.
 * Displacement value is sign-expanded.
 *
 * * Returns:
 * 0: if decoding succeeded
 * < 0: otherwise.
 */
int insn_get_displacement(struct insn *insn)
{
        insn_byte_t mod, rm, base;
        int ret;

        if (insn->displacement.got)
                return 0;

        if (!insn->sib.got) {
                ret = insn_get_sib(insn);
                if (ret)
                        return ret;
        }

        if (insn->modrm.nbytes) {
                /*
                 * Interpreting the modrm byte:
                 * mod = 00 - no displacement fields (exceptions below)
                 * mod = 01 - 1-byte displacement field
                 * mod = 10 - displacement field is 4 bytes, or 2 bytes if
                 *      address size = 2 (0x67 prefix in 32-bit mode)
                 * mod = 11 - no memory operand
                 *
                 * If address size = 2...
                 * mod = 00, r/m = 110 - displacement field is 2 bytes
                 *
                 * If address size != 2...
                 * mod != 11, r/m = 100 - SIB byte exists
                 * mod = 00, SIB base = 101 - displacement field is 4 bytes
                 * mod = 00, r/m = 101 - rip-relative addressing, displacement
                 *      field is 4 bytes
                 */
                mod = X86_MODRM_MOD(insn->modrm.value);
                rm = X86_MODRM_RM(insn->modrm.value);
                base = X86_SIB_BASE(insn->sib.value);
                if (mod == 3)
                        goto out;
                if (mod == 1) {
                        insn_field_set(&insn->displacement,
                                       get_next(signed char, insn), 1);
                } else if (insn->addr_bytes == 2) {
                        if ((mod == 0 && rm == 6) || mod == 2) {
                                insn_field_set(&insn->displacement,
                                               get_next(short, insn), 2);
                        }
                } else {
                        if ((mod == 0 && rm == 5) || mod == 2 ||
                            (mod == 0 && base == 5)) {
                                insn_field_set(&insn->displacement,
                                               get_next(int, insn), 4);
                        }
                }
        }
out:
        insn->displacement.got = 1;
        return 0;

err_out:
        return -ENODATA;
}

/* Decode moffset16/32/64. Return 0 if failed */
static int __get_moffset(struct insn *insn)
{
        switch (insn->addr_bytes) {
        case 2:
                insn_field_set(&insn->moffset1, get_next(short, insn), 2);
                break;
        case 4:
                insn_field_set(&insn->moffset1, get_next(int, insn), 4);
                break;
        case 8:
                insn_field_set(&insn->moffset1, get_next(int, insn), 4);
                insn_field_set(&insn->moffset2, get_next(int, insn), 4);
                break;
        default:        /* opnd_bytes must be modified manually */
                goto err_out;
        }
        insn->moffset1.got = insn->moffset2.got = 1;

        return 1;

err_out:
        return 0;
}

/* Decode imm v32(Iz). Return 0 if failed */
static int __get_immv32(struct insn *insn)
{
        switch (insn->opnd_bytes) {
        case 2:
                insn_field_set(&insn->immediate, get_next(short, insn), 2);
                break;
        case 4:
        case 8:
                insn_field_set(&insn->immediate, get_next(int, insn), 4);
                break;
        default:        /* opnd_bytes must be modified manually */
                goto err_out;
        }

        return 1;

err_out:
        return 0;
}

/* Decode imm v64(Iv/Ov), Return 0 if failed */
static int __get_immv(struct insn *insn)
{
        switch (insn->opnd_bytes) {
        case 2:
                insn_field_set(&insn->immediate1, get_next(short, insn), 2);
                break;
        case 4:
                insn_field_set(&insn->immediate1, get_next(int, insn), 4);
                insn->immediate1.nbytes = 4;
                break;
        case 8:
                insn_field_set(&insn->immediate1, get_next(int, insn), 4);
                insn_field_set(&insn->immediate2, get_next(int, insn), 4);
                break;
        default:        /* opnd_bytes must be modified manually */
                goto err_out;
        }
        insn->immediate1.got = insn->immediate2.got = 1;

        return 1;
err_out:
        return 0;
}

/* Decode ptr16:16/32(Ap) */
static int __get_immptr(struct insn *insn)
{
        switch (insn->opnd_bytes) {
        case 2:
                insn_field_set(&insn->immediate1, get_next(short, insn), 2);
                break;
        case 4:
                insn_field_set(&insn->immediate1, get_next(int, insn), 4);
                break;
        case 8:
                /* ptr16:64 is not exist (no segment) */
                return 0;
        default:        /* opnd_bytes must be modified manually */
                goto err_out;
        }
        insn_field_set(&insn->immediate2, get_next(unsigned short, insn), 2);
        insn->immediate1.got = insn->immediate2.got = 1;

        return 1;
err_out:
        return 0;
}

/**
 * insn_get_immediate() - Get the immediate in an instruction
 * @insn:       &struct insn containing instruction
 *
 * If necessary, first collects the instruction up to and including the
 * displacement bytes.
 * Basically, most of immediates are sign-expanded. Unsigned-value can be
 * computed by bit masking with ((1 << (nbytes * 8)) - 1)
 *
 * Returns:
 * 0:  on success
 * < 0: on error
 */
int insn_get_immediate(struct insn *insn)
{
        int ret;

        if (insn->immediate.got)
                return 0;

        if (!insn->displacement.got) {
                ret = insn_get_displacement(insn);
                if (ret)
                        return ret;
        }

        if (inat_has_moffset(insn->attr)) {
                if (!__get_moffset(insn))
                        goto err_out;
                goto done;
        }

        if (!inat_has_immediate(insn->attr))
                /* no immediates */
                goto done;

        switch (inat_immediate_size(insn->attr)) {
        case INAT_IMM_BYTE:
                insn_field_set(&insn->immediate, get_next(signed char, insn), 1);
                break;
        case INAT_IMM_WORD:
                insn_field_set(&insn->immediate, get_next(short, insn), 2);
                break;
        case INAT_IMM_DWORD:
                insn_field_set(&insn->immediate, get_next(int, insn), 4);
                break;
        case INAT_IMM_QWORD:
                insn_field_set(&insn->immediate1, get_next(int, insn), 4);
                insn_field_set(&insn->immediate2, get_next(int, insn), 4);
                break;
        case INAT_IMM_PTR:
                if (!__get_immptr(insn))
                        goto err_out;
                break;
        case INAT_IMM_VWORD32:
                if (!__get_immv32(insn))
                        goto err_out;
                break;
        case INAT_IMM_VWORD:
                if (!__get_immv(insn))
                        goto err_out;
                break;
        default:
                /* Here, insn must have an immediate, but failed */
                goto err_out;
        }
        if (inat_has_second_immediate(insn->attr)) {
                insn_field_set(&insn->immediate2, get_next(signed char, insn), 1);
        }
done:
        insn->immediate.got = 1;
        return 0;

err_out:
        return -ENODATA;
}

/**
 * insn_get_length() - Get the length of instruction
 * @insn:       &struct insn containing instruction
 *
 * If necessary, first collects the instruction up to and including the
 * immediates bytes.
 *
 * Returns:
 *  - 0 on success
 *  - < 0 on error
*/
int insn_get_length(struct insn *insn)
{
        int ret;

        if (insn->length)
                return 0;

        if (!insn->immediate.got) {
                ret = insn_get_immediate(insn);
                if (ret)
                        return ret;
        }

        insn->length = (unsigned char)((unsigned long)insn->next_byte
                                     - (unsigned long)insn->kaddr);

        return 0;
}

/* Ensure this instruction is decoded completely */
static inline int insn_complete(struct insn *insn)
{
        return insn->opcode.got && insn->modrm.got && insn->sib.got &&
                insn->displacement.got && insn->immediate.got;
}

/**
 * insn_decode() - Decode an x86 instruction
 * @insn:       &struct insn to be initialized
 * @kaddr:      address (in kernel memory) of instruction (or copy thereof)
 * @buf_len:    length of the insn buffer at @kaddr
 * @m:          insn mode, see enum insn_mode
 *
 * Returns:
 * 0: if decoding succeeded
 * < 0: otherwise.
 */
int insn_decode(struct insn *insn, const void *kaddr, int buf_len, enum insn_mode m)
{
        int ret;

/* #define INSN_MODE_KERN       -1 __ignore_sync_check__ mode is only valid in the kernel */

        if (m == INSN_MODE_KERN)
                insn_init(insn, kaddr, buf_len, IS_ENABLED(CONFIG_X86_64));
        else
                insn_init(insn, kaddr, buf_len, m == INSN_MODE_64);

        ret = insn_get_length(insn);
        if (ret)
                return ret;

        if (insn_complete(insn))
                return 0;

        return -EINVAL;
}