/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */
/*
 * Copyright (c) 2018, Joyent, Inc.  All rights reserved.
 * Copyright 2014 Nexenta Systems, Inc.  All rights reserved.
 * Copyright 2025 Oxide Computer Company
 */

#include <sys/types.h>
#include <sys/types32.h>
#include <sys/reg.h>
#include <sys/privregs.h>
#include <sys/stack.h>
#include <sys/frame.h>

#include <mdb/mdb_isautil.h>
#include <mdb/mdb_ia32util.h>
#include <mdb/mdb_target_impl.h>
#include <mdb/mdb_kreg_impl.h>
#include <mdb/mdb_stack.h>
#include <mdb/mdb_debug.h>
#include <mdb/mdb_modapi.h>
#include <mdb/mdb_err.h>
#include <mdb/mdb.h>

#ifndef __amd64
/*
 * We also define an array of register names and their corresponding
 * array indices.  This is used by the getareg and putareg entry points,
 * and also by our register variable discipline.
 *
 * When built into an amd64 mdb this won't be used as it's only a subset of
 * mdb_amd64_kregs, hence the #ifdef.
 */
const mdb_tgt_regdesc_t mdb_ia32_kregs[] = {
        { "savfp", KREG_SAVFP, MDB_TGT_R_EXPORT },
        { "savpc", KREG_SAVPC, MDB_TGT_R_EXPORT },
        { "eax", KREG_EAX, MDB_TGT_R_EXPORT },
        { "ax", KREG_EAX, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
        { "ah", KREG_EAX, MDB_TGT_R_EXPORT | MDB_TGT_R_8H },
        { "al", KREG_EAX, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
        { "ebx", KREG_EBX, MDB_TGT_R_EXPORT },
        { "bx", KREG_EBX, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
        { "bh", KREG_EBX, MDB_TGT_R_EXPORT | MDB_TGT_R_8H },
        { "bl", KREG_EBX, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
        { "ecx", KREG_ECX, MDB_TGT_R_EXPORT },
        { "cx", KREG_ECX, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
        { "ch", KREG_ECX, MDB_TGT_R_EXPORT | MDB_TGT_R_8H },
        { "cl", KREG_ECX, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
        { "edx", KREG_EDX, MDB_TGT_R_EXPORT },
        { "dx", KREG_EDX, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
        { "dh", KREG_EDX, MDB_TGT_R_EXPORT | MDB_TGT_R_8H },
        { "dl", KREG_EDX, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
        { "esi", KREG_ESI, MDB_TGT_R_EXPORT },
        { "si", KREG_ESI, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
        { "edi", KREG_EDI, MDB_TGT_R_EXPORT },
        { "di", EDI, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
        { "ebp", KREG_EBP, MDB_TGT_R_EXPORT },
        { "bp", KREG_EBP, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
        { "esp", KREG_ESP, MDB_TGT_R_EXPORT },
        { "sp", KREG_ESP, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
        { "cs", KREG_CS, MDB_TGT_R_EXPORT },
        { "ds", KREG_DS, MDB_TGT_R_EXPORT },
        { "ss", KREG_SS, MDB_TGT_R_EXPORT },
        { "es", KREG_ES, MDB_TGT_R_EXPORT },
        { "fs", KREG_FS, MDB_TGT_R_EXPORT },
        { "gs", KREG_GS, MDB_TGT_R_EXPORT },
        { "eflags", KREG_EFLAGS, MDB_TGT_R_EXPORT },
        { "eip", KREG_EIP, MDB_TGT_R_EXPORT },
        { "uesp", KREG_UESP, MDB_TGT_R_EXPORT | MDB_TGT_R_PRIV },
        { "usp", KREG_UESP, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
        { "trapno", KREG_TRAPNO, MDB_TGT_R_EXPORT | MDB_TGT_R_PRIV },
        { "err", KREG_ERR, MDB_TGT_R_EXPORT | MDB_TGT_R_PRIV },
        { NULL, 0, 0 }
};
#endif

void
mdb_ia32_printregs(const mdb_tgt_gregset_t *gregs)
{
        const kreg_t *kregs = &gregs->kregs[0];
        kreg_t eflags = kregs[KREG_EFLAGS];

        mdb_printf("%%cs = 0x%04x\t\t%%eax = 0x%08p %A\n",
            kregs[KREG_CS], kregs[KREG_EAX], kregs[KREG_EAX]);

        mdb_printf("%%ds = 0x%04x\t\t%%ebx = 0x%08p %A\n",
            kregs[KREG_DS], kregs[KREG_EBX], kregs[KREG_EBX]);

        mdb_printf("%%ss = 0x%04x\t\t%%ecx = 0x%08p %A\n",
            kregs[KREG_SS], kregs[KREG_ECX], kregs[KREG_ECX]);

        mdb_printf("%%es = 0x%04x\t\t%%edx = 0x%08p %A\n",
            kregs[KREG_ES], kregs[KREG_EDX], kregs[KREG_EDX]);

        mdb_printf("%%fs = 0x%04x\t\t%%esi = 0x%08p %A\n",
            kregs[KREG_FS], kregs[KREG_ESI], kregs[KREG_ESI]);

        mdb_printf("%%gs = 0x%04x\t\t%%edi = 0x%08p %A\n\n",
            kregs[KREG_GS], kregs[KREG_EDI], kregs[KREG_EDI]);

        mdb_printf("%%eip = 0x%08p %A\n", kregs[KREG_EIP], kregs[KREG_EIP]);
        mdb_printf("%%ebp = 0x%08p\n", kregs[KREG_EBP]);
        mdb_printf("%%esp = 0x%08p\n\n", kregs[KREG_ESP]);
        mdb_printf("%%eflags = 0x%08x\n", eflags);

        mdb_printf("  id=%u vip=%u vif=%u ac=%u vm=%u rf=%u nt=%u iopl=0x%x\n",
            (eflags & KREG_EFLAGS_ID_MASK) >> KREG_EFLAGS_ID_SHIFT,
            (eflags & KREG_EFLAGS_VIP_MASK) >> KREG_EFLAGS_VIP_SHIFT,
            (eflags & KREG_EFLAGS_VIF_MASK) >> KREG_EFLAGS_VIF_SHIFT,
            (eflags & KREG_EFLAGS_AC_MASK) >> KREG_EFLAGS_AC_SHIFT,
            (eflags & KREG_EFLAGS_VM_MASK) >> KREG_EFLAGS_VM_SHIFT,
            (eflags & KREG_EFLAGS_RF_MASK) >> KREG_EFLAGS_RF_SHIFT,
            (eflags & KREG_EFLAGS_NT_MASK) >> KREG_EFLAGS_NT_SHIFT,
            (eflags & KREG_EFLAGS_IOPL_MASK) >> KREG_EFLAGS_IOPL_SHIFT);

        mdb_printf("  status=<%s,%s,%s,%s,%s,%s,%s,%s,%s>\n\n",
            (eflags & KREG_EFLAGS_OF_MASK) ? "OF" : "of",
            (eflags & KREG_EFLAGS_DF_MASK) ? "DF" : "df",
            (eflags & KREG_EFLAGS_IF_MASK) ? "IF" : "if",
            (eflags & KREG_EFLAGS_TF_MASK) ? "TF" : "tf",
            (eflags & KREG_EFLAGS_SF_MASK) ? "SF" : "sf",
            (eflags & KREG_EFLAGS_ZF_MASK) ? "ZF" : "zf",
            (eflags & KREG_EFLAGS_AF_MASK) ? "AF" : "af",
            (eflags & KREG_EFLAGS_PF_MASK) ? "PF" : "pf",
            (eflags & KREG_EFLAGS_CF_MASK) ? "CF" : "cf");

#if !defined(__amd64) && !defined(_KMDB)
        mdb_printf("  %%uesp = 0x%08x\n", kregs[KREG_UESP]);
#endif
        mdb_printf("%%trapno = 0x%x\n", kregs[KREG_TRAPNO]);
        mdb_printf("   %%err = 0x%x\n", kregs[KREG_ERR]);
}

/*
 * Given a return address (%eip), determine the likely number of arguments
 * that were pushed on the stack prior to its execution.  We do this by
 * expecting that a typical call sequence consists of pushing arguments on
 * the stack, executing a call instruction, and then performing an add
 * on %esp to restore it to the value prior to pushing the arguments for
 * the call.  We attempt to detect such an add, and divide the addend
 * by the size of a word to determine the number of pushed arguments.
 */
static uint_t
kvm_argcount(mdb_tgt_t *t, uintptr_t eip, ssize_t size)
{
        uint8_t ins[6];
        ulong_t n;

        enum {
                M_MODRM_ESP = 0xc4,     /* Mod/RM byte indicates %esp */
                M_ADD_IMM32 = 0x81,     /* ADD imm32 to r/m32 */
                M_ADD_IMM8  = 0x83      /* ADD imm8 to r/m32 */
        };

        if (mdb_tgt_aread(t, MDB_TGT_AS_VIRT_I, ins, sizeof (ins), eip) !=
            sizeof (ins))
                return (0);

        if (ins[1] != M_MODRM_ESP)
                return (0);

        switch (ins[0]) {
        case M_ADD_IMM32:
                n = ins[2] + (ins[3] << 8) + (ins[4] << 16) + (ins[5] << 24);
                break;

        case M_ADD_IMM8:
                n = ins[2];
                break;

        default:
                n = 0;
        }

        return (MIN((ssize_t)n, size) / sizeof (uint32_t));
}

int
mdb_ia32_kvm_stack_iter(mdb_tgt_t *t, const mdb_tgt_gregset_t *gsp,
    mdb_tgt_stack_f *func, void *arg)
{
        mdb_tgt_gregset_t gregs;
        kreg_t *kregs = &gregs.kregs[0];
        int got_pc = (gsp->kregs[KREG_EIP] != 0);
        int err;

        struct fr {
                uintptr32_t fr_savfp;
                uintptr32_t fr_savpc;
                uint32_t fr_argv[32];
        } fr;

        uintptr_t fp = gsp->kregs[KREG_EBP];
        uintptr_t pc = gsp->kregs[KREG_EIP];
        uintptr_t lastfp = 0;

        ssize_t size;
        uint_t argc;
        int detect_exception_frames = 0;
        int advance_tortoise = 1;
        uintptr_t tortoise_fp = 0;
#ifndef _KMDB
        int xp;

        if ((mdb_readsym(&xp, sizeof (xp), "xpv_panicking") != -1) && (xp > 0))
                detect_exception_frames = 1;
#endif

        bcopy(gsp, &gregs, sizeof (gregs));

        while (fp != 0) {
                if (fp & (STACK_ALIGN - 1)) {
                        err = EMDB_STKALIGN;
                        goto badfp;
                }
                if ((size = mdb_tgt_aread(t, MDB_TGT_AS_VIRT_S, &fr,
                    sizeof (fr), fp)) >= (ssize_t)(2 * sizeof (uintptr32_t))) {
                        size -= (ssize_t)(2 * sizeof (uintptr32_t));
                        argc = kvm_argcount(t, fr.fr_savpc, size);
                } else {
                        err = EMDB_NOMAP;
                        goto badfp;
                }

                if (tortoise_fp == 0) {
                        tortoise_fp = fp;
                } else {
                        /*
                         * Advance tortoise_fp every other frame, so we detect
                         * cycles with Floyd's tortoise/hare.
                         */
                        if (advance_tortoise != 0) {
                                struct fr tfr;

                                if (mdb_tgt_aread(t, MDB_TGT_AS_VIRT_S, &tfr,
                                    sizeof (tfr), tortoise_fp) !=
                                    sizeof (tfr)) {
                                        err = EMDB_NOMAP;
                                        goto badfp;
                                }

                                tortoise_fp = tfr.fr_savfp;
                        }

                        if (fp == tortoise_fp) {
                                err = EMDB_STKFRAME;
                                goto badfp;
                        }
                }

                advance_tortoise = !advance_tortoise;

                if (got_pc &&
                    func(arg, pc, argc, (const long *)fr.fr_argv, &gregs) != 0)
                        break;

                kregs[KREG_ESP] = kregs[KREG_EBP];

                lastfp = fp;
                fp = fr.fr_savfp;
                /*
                 * The Xen hypervisor marks a stack frame as belonging to
                 * an exception by inverting the bits of the pointer to
                 * that frame.  We attempt to identify these frames by
                 * inverting the pointer and seeing if it is within 0xfff
                 * bytes of the last frame.
                 */
                if (detect_exception_frames)
                        if ((fp != 0) && (fp < lastfp) &&
                            ((lastfp ^ ~fp) < 0xfff))
                                fp = ~fp;

                kregs[KREG_EBP] = fp;
                kregs[KREG_EIP] = pc = fr.fr_savpc;

                got_pc = (pc != 0);
        }

        return (0);

badfp:
        mdb_printf("%p [%s]", fp, mdb_strerror(err));
        return (set_errno(err));
}

#ifndef __amd64
/*
 * The functions mdb_ia32_step_out and mdb_ia32_next haven't yet been adapted
 * to work when built for an amd64 mdb. They are unused by the amd64-only bhyve
 * target, hence the #ifdef.
 */
/*
 * Determine the return address for the current frame.  Typically this is the
 * fr_savpc value from the current frame, but we also perform some special
 * handling to see if we are stopped on one of the first two instructions of a
 * typical function prologue, in which case %ebp will not be set up yet.
 */
int
mdb_ia32_step_out(mdb_tgt_t *t, uintptr_t *p, kreg_t pc, kreg_t fp, kreg_t sp,
    mdb_instr_t curinstr)
{
        struct frame fr;
        GElf_Sym s;
        char buf[1];

        enum {
                M_PUSHL_EBP     = 0x55, /* pushl %ebp */
                M_MOVL_EBP      = 0x8b  /* movl %esp, %ebp */
        };

        if (mdb_tgt_lookup_by_addr(t, pc, MDB_TGT_SYM_FUZZY,
            buf, 0, &s, NULL) == 0) {
                if (pc == s.st_value && curinstr == M_PUSHL_EBP)
                        fp = sp - 4;
                else if (pc == s.st_value + 1 && curinstr == M_MOVL_EBP)
                        fp = sp;
        }

        if (mdb_tgt_aread(t, MDB_TGT_AS_VIRT_S, &fr, sizeof (fr), fp) ==
            sizeof (fr)) {
                *p = fr.fr_savpc;
                return (0);
        }

        return (-1); /* errno is set for us */
}

/*
 * Return the address of the next instruction following a call, or return -1
 * and set errno to EAGAIN if the target should just single-step.  We perform
 * a bit of disassembly on the current instruction in order to determine if it
 * is a call and how many bytes should be skipped, depending on the exact form
 * of the call instruction that is being used.
 */
int
mdb_ia32_next(mdb_tgt_t *t, uintptr_t *p, kreg_t pc, mdb_instr_t curinstr)
{
        uint8_t m;

        enum {
                M_CALL_REL = 0xe8, /* call near with relative displacement */
                M_CALL_REG = 0xff, /* call near indirect or call far register */

                M_MODRM_MD = 0xc0, /* mask for Mod/RM byte Mod field */
                M_MODRM_OP = 0x38, /* mask for Mod/RM byte opcode field */
                M_MODRM_RM = 0x07, /* mask for Mod/RM byte R/M field */

                M_MD_IND   = 0x00, /* Mod code for [REG] */
                M_MD_DSP8  = 0x40, /* Mod code for disp8[REG] */
                M_MD_DSP32 = 0x80, /* Mod code for disp32[REG] */
                M_MD_REG   = 0xc0, /* Mod code for REG */

                M_OP_IND   = 0x10, /* Opcode for call near indirect */
                M_RM_DSP32 = 0x05  /* R/M code for disp32 */
        };

        /*
         * If the opcode is a near call with relative displacement, assume the
         * displacement is a rel32 from the next instruction.
         */
        if (curinstr == M_CALL_REL) {
                *p = pc + sizeof (mdb_instr_t) + sizeof (uint32_t);
                return (0);
        }

        /*
         * If the opcode is a call near indirect or call far register opcode,
         * read the subsequent Mod/RM byte to perform additional decoding.
         */
        if (curinstr == M_CALL_REG) {
                if (mdb_tgt_aread(t, MDB_TGT_AS_VIRT_I, &m, sizeof (m), pc + 1)
                    != sizeof (m))
                        return (-1); /* errno is set for us */

                /*
                 * If the Mod/RM opcode extension indicates a near indirect
                 * call, then skip the appropriate number of additional
                 * bytes depending on the addressing form that is used.
                 */
                if ((m & M_MODRM_OP) == M_OP_IND) {
                        switch (m & M_MODRM_MD) {
                        case M_MD_DSP8:
                                *p = pc + 3; /* skip pr_instr, m, disp8 */
                                break;
                        case M_MD_DSP32:
                                *p = pc + 6; /* skip pr_instr, m, disp32 */
                                break;
                        case M_MD_IND:
                                if ((m & M_MODRM_RM) == M_RM_DSP32) {
                                        *p = pc + 6;
                                        break; /* skip pr_instr, m, disp32 */
                                }
                                /* FALLTHRU */
                        case M_MD_REG:
                                *p = pc + 2; /* skip pr_instr, m */
                                break;
                        }
                        return (0);
                }
        }

        return (set_errno(EAGAIN));
}
#endif

int
mdb_ia32_kvm_frame(void *argp, uintptr_t pc, uint_t argc, const long *argv,
    const mdb_tgt_gregset_t *gregs)
{
        mdb_stack_frame_hdl_t *hdl = argp;
        uint64_t bp;

        bp = gregs->kregs[KREG_EBP];
        mdb_stack_frame(hdl, pc, bp, argc, argv);
        return (0);
}

/*
 * Check if the instruction immediately before the given program counter (pcp)
 * is a CALL instruction in IA-32 (x86 32-bit) mode. Since x86 instructions are
 * variable-length, we read the 8 bytes preceding the PC and look for specific
 * call encodings at known offsets that would align with common call
 * instruction lengths. Although x86 instructions can be up to 15 bytes long,
 * for a CALL to reach that length would require a long sequence of prefixes.
 * Of those, only the address-size prefix would affect where we need to look
 * for the instruction, and such prefixes are extremely rare in real-world
 * code.
 */
boolean_t
mdb_ia32_prev_callcheck(uintptr_t pcp)
{
        uint8_t buf[8];

        /*
         * Ensure we can read 8 bytes before the PC. This accommodates the
         * largest call encoding we care about (far calls).
         */
        if (pcp < 8 || mdb_vread(buf, sizeof (buf), pcp - 8) != sizeof (buf))
                return (B_FALSE);

        /*
         * Direct near call: CALL rel32
         * Opcode: E8, followed by 4-byte PC-relative offset.
         */
        if (buf[3] == 0xe8)
                return (B_TRUE);

        /*
         * Indirect near call: CALL r/m32
         * Opcode: FF /2 (i.e., reg field of ModR/M is 010).
         *
         * We're expecting the instruction to be exactly 2 bytes: FF 14,
         * with opcode at buf[5] and ModR/M at buf[6].
         *
         * buf[6] == 0x14 means:
         *  - mod = 00 (no displacement)
         *  - reg = 010 (CALL)
         *  - r/m = 100 (SIB follows — typically [esp])
         *
         * This form is common in PLT stubs like: CALL DWORD PTR [ESP]
         *
         * Other encodings of FF /2 are less plausible here:
         *  - mod = 01 - 8-bit displacement - unlikely for noreturn functions
         *  - mod = 10 - 32-bit displacement - would overlap with PC; invalid
         *  - mod = 00 with r/m != 100 - e.g., CALL EAX - would return to
         *    buf[7], not pcp
         */
        if (buf[5] == 0xff && buf[6] == 0x14)
                return (B_TRUE);

        /*
         * Indirect absolute call: CALL DWORD PTR [disp32]
         * Encoding: FF 15 xx xx xx xx
         * Instruction is 6 bytes long; opcode at buf[2], ModR/M at buf[3].
         * Used to call through global function pointers.
         */
        if (buf[2] == 0xff && buf[3] == 0x15)
                return (B_TRUE);

        /*
         * Far call (segment-based): CALL FAR ptr16:32
         * Opcode: 9A, followed by 6-byte far pointer.
         * Instruction is 7 bytes; opcode at buf[0].
         */
        if (buf[0] == 0x9a)
                return (B_TRUE);

        return (B_FALSE);
}