common/mdb/mdb_kvm.c

/*
 * 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 (c) 1999, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*
 * Copyright (c) 2013, Joyent, Inc.  All rights reserved.
 */

/*
 * Libkvm Kernel Target
 *
 * The libkvm kernel target provides access to both crash dumps and live
 * kernels through /dev/ksyms and /dev/kmem, using the facilities provided by
 * the libkvm.so library.  The target-specific data structures are shared
 * between this file (common code) and the ISA-dependent parts of the target,
 * and so they are defined in the mdb_kvm.h header.  The target processes an
 * "executable" (/dev/ksyms or the unix.X file) which contains a primary
 * .symtab and .dynsym, and then also iterates over the krtld module chain in
 * the kernel in order to obtain a list of loaded modules and per-module symbol
 * tables.  To improve startup performance, the per-module symbol tables are
 * instantiated on-the-fly whenever an address lookup falls within the text
 * section of a given module.  The target also relies on services from the
 * mdb_ks (kernel support) module, which contains pieces of the implementation
 * that must be compiled against the kernel implementation.
 */

#include <sys/modctl.h>
#include <sys/kobj.h>
#include <sys/kobj_impl.h>
#include <sys/utsname.h>
#include <sys/panic.h>
#include <sys/dumphdr.h>
#include <sys/dumpadm.h>

#include <dlfcn.h>
#include <libctf.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>

#include <mdb/mdb_target_impl.h>
#include <mdb/mdb_err.h>
#include <mdb/mdb_debug.h>
#include <mdb/mdb_string.h>
#include <mdb/mdb_modapi.h>
#include <mdb/mdb_io_impl.h>
#include <mdb/mdb_ctf.h>
#include <mdb/mdb_kvm.h>
#include <mdb/mdb_module.h>
#include <mdb/mdb_kb.h>
#include <mdb/mdb.h>

#define KT_RELOC_BUF(buf, obase, nbase) \
    ((uintptr_t)(buf) - (uintptr_t)(obase) + (uintptr_t)(nbase))

#define KT_BAD_BUF(buf, base, size) \
    ((uintptr_t)(buf) < (uintptr_t)(base) || \
    ((uintptr_t)(buf) >= (uintptr_t)(base) + (uintptr_t)(size)))

typedef struct kt_symarg {
    mdb_tgt_sym_f *sym_cb;      /* Caller's callback function */
    void *sym_data;         /* Callback function argument */
    uint_t sym_type;        /* Symbol type/binding filter */
    mdb_syminfo_t sym_info;     /* Symbol id and table id */
    const char *sym_obj;        /* Containing object */
} kt_symarg_t;

typedef struct kt_maparg {
    mdb_tgt_t *map_target;      /* Target used for mapping iter */
    mdb_tgt_map_f *map_cb;      /* Caller's callback function */
    void *map_data;         /* Callback function argument */
} kt_maparg_t;

static const char KT_MODULE[] = "mdb_ks";
static const char KT_CTFPARENT[] = "genunix";

static void
kt_load_module(kt_data_t *kt, mdb_tgt_t *t, kt_module_t *km)
{
    km->km_data = mdb_alloc(km->km_datasz, UM_SLEEP);

    (void) mdb_tgt_vread(t, km->km_data, km->km_datasz, km->km_symspace_va);

    km->km_symbuf = (void *)
        KT_RELOC_BUF(km->km_symtab_va, km->km_symspace_va, km->km_data);

    km->km_strtab = (char *)
        KT_RELOC_BUF(km->km_strtab_va, km->km_symspace_va, km->km_data);

    km->km_symtab = mdb_gelf_symtab_create_raw(&kt->k_file->gf_ehdr,
        &km->km_symtab_hdr, km->km_symbuf,
        &km->km_strtab_hdr, km->km_strtab, MDB_TGT_SYMTAB);
}

static void
kt_load_modules(kt_data_t *kt, mdb_tgt_t *t)
{
    char name[MAXNAMELEN];
    uintptr_t addr, head;

    struct module kmod;
    struct modctl ctl;
    Shdr symhdr, strhdr;
    GElf_Sym sym;

    kt_module_t *km;

    if (mdb_tgt_lookup_by_name(t, MDB_TGT_OBJ_EXEC,
        "modules", &sym, NULL) == -1) {
        warn("failed to get 'modules' symbol");
        return;
    }

    if (mdb_tgt_readsym(t, MDB_TGT_AS_VIRT, &ctl, sizeof (ctl),
        MDB_TGT_OBJ_EXEC, "modules") != sizeof (ctl)) {
        warn("failed to read 'modules' struct");
        return;
    }

    addr = head = (uintptr_t)sym.st_value;

    do {
        if (addr == NULL)
            break; /* Avoid spurious NULL pointers in list */

        if (mdb_tgt_vread(t, &ctl, sizeof (ctl), addr) == -1) {
            warn("failed to read modctl at %p", (void *)addr);
            return;
        }

        if (ctl.mod_mp == NULL)
            continue; /* No associated krtld structure */

        if (mdb_tgt_readstr(t, MDB_TGT_AS_VIRT, name, MAXNAMELEN,
            (uintptr_t)ctl.mod_modname) <= 0) {
            warn("failed to read module name at %p",
                (void *)ctl.mod_modname);
            continue;
        }

        mdb_dprintf(MDB_DBG_KMOD, "reading mod %s (%p)\n",
            name, (void *)addr);

        if (mdb_nv_lookup(&kt->k_modules, name) != NULL) {
            warn("skipping duplicate module '%s', id=%d\n",
                name, ctl.mod_id);
            continue;
        }

        if (mdb_tgt_vread(t, &kmod, sizeof (kmod),
            (uintptr_t)ctl.mod_mp) == -1) {
            warn("failed to read module at %p\n",
                (void *)ctl.mod_mp);
            continue;
        }

        if (kmod.symspace == NULL || kmod.symhdr == NULL ||
            kmod.strhdr == NULL) {
            /*
             * If no buffer for the symbols has been allocated,
             * or the shdrs for .symtab and .strtab are missing,
             * then we're out of luck.
             */
            continue;
        }

        if (mdb_tgt_vread(t, &symhdr, sizeof (Shdr),
            (uintptr_t)kmod.symhdr) == -1) {
            warn("failed to read .symtab header for '%s', id=%d",
                name, ctl.mod_id);
            continue;
        }

        if (mdb_tgt_vread(t, &strhdr, sizeof (Shdr),
            (uintptr_t)kmod.strhdr) == -1) {
            warn("failed to read .strtab header for '%s', id=%d",
                name, ctl.mod_id);
            continue;
        }

        /*
         * Now get clever: f(*^ing krtld didn't used to bother updating
         * its own kmod.symsize value.  We know that prior to this bug
         * being fixed, symspace was a contiguous buffer containing
         * .symtab, .strtab, and the symbol hash table in that order.
         * So if symsize is zero, recompute it as the size of .symtab
         * plus the size of .strtab.  We don't need to load the hash
         * table anyway since we re-hash all the symbols internally.
         */
        if (kmod.symsize == 0)
            kmod.symsize = symhdr.sh_size + strhdr.sh_size;

        /*
         * Similar logic can be used to make educated guesses
         * at the values of kmod.symtbl and kmod.strings.
         */
        if (kmod.symtbl == NULL)
            kmod.symtbl = kmod.symspace;
        if (kmod.strings == NULL)
            kmod.strings = kmod.symspace + symhdr.sh_size;

        /*
         * Make sure things seem reasonable before we proceed
         * to actually read and decipher the symspace.
         */
        if (KT_BAD_BUF(kmod.symtbl, kmod.symspace, kmod.symsize) ||
            KT_BAD_BUF(kmod.strings, kmod.symspace, kmod.symsize)) {
            warn("skipping module '%s', id=%d (corrupt symspace)\n",
                name, ctl.mod_id);
            continue;
        }

        km = mdb_zalloc(sizeof (kt_module_t), UM_SLEEP);
        km->km_name = strdup(name);

        (void) mdb_nv_insert(&kt->k_modules, km->km_name, NULL,
            (uintptr_t)km, MDB_NV_EXTNAME);

        km->km_datasz = kmod.symsize;
        km->km_symspace_va = (uintptr_t)kmod.symspace;
        km->km_symtab_va = (uintptr_t)kmod.symtbl;
        km->km_strtab_va = (uintptr_t)kmod.strings;
        km->km_symtab_hdr = symhdr;
        km->km_strtab_hdr = strhdr;
        km->km_text_va = (uintptr_t)kmod.text;
        km->km_text_size = kmod.text_size;
        km->km_data_va = (uintptr_t)kmod.data;
        km->km_data_size = kmod.data_size;
        km->km_bss_va = (uintptr_t)kmod.bss;
        km->km_bss_size = kmod.bss_size;

        if (kt->k_ctfvalid) {
            km->km_ctf_va = (uintptr_t)kmod.ctfdata;
            km->km_ctf_size = kmod.ctfsize;
        }

        /*
         * Add the module to the end of the list of modules in load-
         * dependency order.  This is needed to load the corresponding
         * debugger modules in the same order for layering purposes.
         */
        mdb_list_append(&kt->k_modlist, km);

        if (t->t_flags & MDB_TGT_F_PRELOAD) {
            mdb_iob_printf(mdb.m_out, " %s", name);
            mdb_iob_flush(mdb.m_out);
            kt_load_module(kt, t, km);
        }

    } while ((addr = (uintptr_t)ctl.mod_next) != head);
}

int
kt_setflags(mdb_tgt_t *t, int flags)
{
    int iochg = ((flags ^ t->t_flags) & MDB_TGT_F_ALLOWIO) &&
        !mdb_prop_postmortem;
    int rwchg = (flags ^ t->t_flags) & MDB_TGT_F_RDWR;
    kt_data_t *kt = t->t_data;
    const char *kvmfile;
    void *cookie;
    int mode;

    if (!iochg && !rwchg)
        return (0);

    if (kt->k_xpv_domu) {
        warn("read-only target");
        return (-1);
    }

    if (iochg) {
        kvmfile = (flags & MDB_TGT_F_ALLOWIO) ? "/dev/allkmem" :
            "/dev/kmem";
    } else {
        kvmfile = kt->k_kvmfile;
    }

    mode = (flags & MDB_TGT_F_RDWR) ? O_RDWR : O_RDONLY;

    if ((cookie = kt->k_kb_ops->kb_open(kt->k_symfile, kvmfile, NULL, mode,
        mdb.m_pname)) == NULL) {
        /* We failed to re-open, so don't change t_flags */
        warn("failed to re-open target");
        return (-1);
    }

    /*
     * We successfully reopened the target, so update k_kvmfile.  Also set
     * the RDWR and ALLOWIO bits in t_flags to match those in flags.
     */
    (void) kt->k_kb_ops->kb_close(kt->k_cookie);
    kt->k_cookie = cookie;

    if (kvmfile != kt->k_kvmfile) {
        strfree(kt->k_kvmfile);
        kt->k_kvmfile = strdup(kvmfile);
    }

    t->t_flags = (t->t_flags & ~(MDB_TGT_F_RDWR | MDB_TGT_F_ALLOWIO)) |
        (flags & (MDB_TGT_F_RDWR | MDB_TGT_F_ALLOWIO));

    return (0);
}

/*
 * Determine which PIDs (if any) have their pages saved in the dump.  We
 * do this by looking for content flags in dump_flags in the header.  These
 * flags, which won't be set in older dumps, tell us whether a single process
 * has had its pages included in the dump.  If a single process has been
 * included, we need to get the PID for that process from the dump_pids
 * array in the dump.
 */
static int
kt_find_dump_contents(kt_data_t *kt)
{
    dumphdr_t *dh = kt->k_dumphdr;
    pid_t pid = -1;

    if (dh->dump_flags & DF_ALL)
        return (KT_DUMPCONTENT_ALL);

    if (dh->dump_flags & DF_CURPROC) {
        if ((pid = kt->k_dump_find_curproc()) == -1)
            return (KT_DUMPCONTENT_INVALID);
        else
            return (pid);
    } else {
        return (KT_DUMPCONTENT_KERNEL);
    }
}

static int
kt_dump_contains_proc(mdb_tgt_t *t, void *context)
{
    kt_data_t *kt = t->t_data;
    pid_t (*f_pid)(uintptr_t);
    pid_t reqpid;

    switch (kt->k_dumpcontent) {
    case KT_DUMPCONTENT_KERNEL:
        return (0);
    case KT_DUMPCONTENT_ALL:
        return (1);
    case KT_DUMPCONTENT_INVALID:
        goto procnotfound;
    default:
        f_pid = (pid_t (*)()) dlsym(RTLD_NEXT, "mdb_kproc_pid");
        if (f_pid == NULL)
            goto procnotfound;

        reqpid = f_pid((uintptr_t)context);
        if (reqpid == -1)
            goto procnotfound;

        return (kt->k_dumpcontent == reqpid);
    }

procnotfound:
    warn("unable to determine whether dump contains proc %p\n", context);
    return (1);
}

int
kt_setcontext(mdb_tgt_t *t, void *context)
{
    if (context != NULL) {
        const char *argv[2];
        int argc = 0;
        mdb_tgt_t *ct;
        kt_data_t *kt = t->t_data;

        argv[argc++] = (const char *)context;
        argv[argc] = NULL;

        if (kt->k_dumphdr != NULL &&
            !kt_dump_contains_proc(t, context)) {
            warn("dump does not contain pages for proc %p\n",
                context);
            return (-1);
        }

        if ((ct = mdb_tgt_create(mdb_kproc_tgt_create,
            t->t_flags, argc, argv)) == NULL)
            return (-1);

        mdb_printf("debugger context set to proc %p\n", context);
        mdb_tgt_activate(ct);
    } else
        mdb_printf("debugger context set to kernel\n");

    return (0);
}

static int
kt_stack(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
    kt_data_t *kt = mdb.m_target->t_data;
    return (kt->k_dcmd_stack(addr, flags, argc, argv));
}

static int
kt_stackv(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
    kt_data_t *kt = mdb.m_target->t_data;
    return (kt->k_dcmd_stackv(addr, flags, argc, argv));
}

static int
kt_stackr(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
    kt_data_t *kt = mdb.m_target->t_data;
    return (kt->k_dcmd_stackr(addr, flags, argc, argv));
}

static int
kt_regs(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
    kt_data_t *kt = mdb.m_target->t_data;

    if (argc != 0 || (flags & DCMD_ADDRSPEC))
        return (DCMD_USAGE);

    addr = (uintptr_t)kt->k_regs;

    return (kt->k_dcmd_regs(addr, flags, argc, argv));
}

#ifdef __x86
static int
kt_cpustack(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
    kt_data_t *kt = mdb.m_target->t_data;
    return (kt->k_dcmd_cpustack(addr, flags, argc, argv));
}

static int
kt_cpuregs(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
    kt_data_t *kt = mdb.m_target->t_data;
    return (kt->k_dcmd_cpuregs(addr, flags, argc, argv));
}
#endif /* __x86 */

/*ARGSUSED*/
static int
kt_status_dcmd(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
    kt_data_t *kt = mdb.m_target->t_data;
    struct utsname uts;

    bzero(&uts, sizeof (uts));
    (void) strcpy(uts.nodename, "unknown machine");
    (void) kt_uname(mdb.m_target, &uts);

    if (mdb_prop_postmortem) {
        mdb_printf("debugging %scrash dump %s (%d-bit) from %s\n",
            kt->k_xpv_domu ? "domain " : "", kt->k_kvmfile,
            (int)(sizeof (void *) * NBBY), uts.nodename);
    } else {
        mdb_printf("debugging live kernel (%d-bit) on %s\n",
            (int)(sizeof (void *) * NBBY), uts.nodename);
    }

    mdb_printf("operating system: %s %s (%s)\n",
        uts.release, uts.version, uts.machine);

    if (kt->k_dumphdr) {
        dumphdr_t *dh = kt->k_dumphdr;

        mdb_printf("image uuid: %s\n", dh->dump_uuid[0] != '\0' ?
            dh->dump_uuid : "(not set)");
        mdb_printf("panic message: %s\n", dh->dump_panicstring);

        kt->k_dump_print_content(dh, kt->k_dumpcontent);
    } else {
        char uuid[37];

        if (mdb_readsym(uuid, 37, "dump_osimage_uuid") == 37 &&
            uuid[36] == '\0') {
            mdb_printf("image uuid: %s\n", uuid);
        }
    }

    return (DCMD_OK);
}

static const mdb_dcmd_t kt_dcmds[] = {
    { "$c", "?[cnt]", "print stack backtrace", kt_stack },
    { "$C", "?[cnt]", "print stack backtrace", kt_stackv },
    { "$r", NULL, "print general-purpose registers", kt_regs },
    { "$?", NULL, "print status and registers", kt_regs },
    { "regs", NULL, "print general-purpose registers", kt_regs },
    { "stack", "?[cnt]", "print stack backtrace", kt_stack },
    { "stackregs", "?", "print stack backtrace and registers", kt_stackr },
#ifdef __x86
    { "cpustack", "?[-v] [-c cpuid] [cnt]", "print stack backtrace for a "
        "specific CPU", kt_cpustack },
    { "cpuregs", "?[-c cpuid]", "print general-purpose registers for a "
        "specific CPU", kt_cpuregs },
#endif
    { "status", NULL, "print summary of current target", kt_status_dcmd },
    { NULL }
};

static uintmax_t
reg_disc_get(const mdb_var_t *v)
{
    mdb_tgt_t *t = MDB_NV_COOKIE(v);
    kt_data_t *kt = t->t_data;
    mdb_tgt_reg_t r = 0;

    (void) mdb_tgt_getareg(t, kt->k_tid, mdb_nv_get_name(v), &r);
    return (r);
}

static kt_module_t *
kt_module_by_name(kt_data_t *kt, const char *name)
{
    kt_module_t *km;

    for (km = mdb_list_next(&kt->k_modlist); km; km = mdb_list_next(km)) {
        if (strcmp(name, km->km_name) == 0)
            return (km);
    }

    return (NULL);
}

void
kt_activate(mdb_tgt_t *t)
{
    static const mdb_nv_disc_t reg_disc = { NULL, reg_disc_get };
    kt_data_t *kt = t->t_data;
    void *sym;

    int oflag;

    mdb_prop_postmortem = kt->k_xpv_domu || (kt->k_dumphdr != NULL);
    mdb_prop_kernel = TRUE;
    mdb_prop_datamodel = MDB_TGT_MODEL_NATIVE;

    if (kt->k_activated == FALSE) {
        struct utsname u1, u2;
        /*
         * If we're examining a crash dump, root is /, and uname(2)
         * does not match the utsname in the dump, issue a warning.
         * Note that we are assuming that the modules and macros in
         * /usr/lib are compiled against the kernel from uname -rv.
         */
        if (mdb_prop_postmortem && strcmp(mdb.m_root, "/") == 0 &&
            uname(&u1) >= 0 && kt_uname(t, &u2) >= 0 &&
            (strcmp(u1.release, u2.release) ||
            strcmp(u1.version, u2.version))) {
            mdb_warn("warning: dump is from %s %s %s; dcmds and "
                "macros may not match kernel implementation\n",
                u2.sysname, u2.release, u2.version);
        }

        if (mdb_module_load(KT_MODULE, MDB_MOD_GLOBAL) < 0) {
            warn("failed to load kernel support module -- "
                "some modules may not load\n");
        }

        if (mdb_prop_postmortem && kt->k_dumphdr != NULL) {
            sym = dlsym(RTLD_NEXT, "mdb_dump_print_content");
            if (sym != NULL)
                kt->k_dump_print_content = (void (*)())sym;

            sym = dlsym(RTLD_NEXT, "mdb_dump_find_curproc");
            if (sym != NULL)
                kt->k_dump_find_curproc = (int (*)())sym;

            kt->k_dumpcontent = kt_find_dump_contents(kt);
        }

        if (t->t_flags & MDB_TGT_F_PRELOAD) {
            oflag = mdb_iob_getflags(mdb.m_out) & MDB_IOB_PGENABLE;

            mdb_iob_clrflags(mdb.m_out, oflag);
            mdb_iob_puts(mdb.m_out, "Preloading module symbols: [");
            mdb_iob_flush(mdb.m_out);
        }

        if (!(t->t_flags & MDB_TGT_F_NOLOAD)) {
            kt_load_modules(kt, t);

            /*
             * Determine where the CTF data for krtld is. If krtld
             * is rolled into unix, force load the MDB krtld
             * module.
             */
            kt->k_rtld_name = "krtld";

            if (kt_module_by_name(kt, "krtld") == NULL) {
                (void) mdb_module_load("krtld", MDB_MOD_SILENT);
                kt->k_rtld_name = "unix";
            }
        }


        if (t->t_flags & MDB_TGT_F_PRELOAD) {
            mdb_iob_puts(mdb.m_out, " ]\n");
            mdb_iob_setflags(mdb.m_out, oflag);
        }

        kt->k_activated = TRUE;
    }

    (void) mdb_tgt_register_dcmds(t, &kt_dcmds[0], MDB_MOD_FORCE);

    /* Export some of our registers as named variables */
    mdb_tgt_register_regvars(t, kt->k_rds, &reg_disc, MDB_NV_RDONLY);

    mdb_tgt_elf_export(kt->k_file);
}

void
kt_deactivate(mdb_tgt_t *t)
{
    kt_data_t *kt = t->t_data;

    const mdb_tgt_regdesc_t *rdp;
    const mdb_dcmd_t *dcp;

    for (rdp = kt->k_rds; rdp->rd_name != NULL; rdp++) {
        mdb_var_t *v;

        if (!(rdp->rd_flags & MDB_TGT_R_EXPORT))
            continue; /* Didn't export register as a variable */

        if ((v = mdb_nv_lookup(&mdb.m_nv, rdp->rd_name)) != NULL) {
            v->v_flags &= ~MDB_NV_PERSIST;
            mdb_nv_remove(&mdb.m_nv, v);
        }
    }

    for (dcp = &kt_dcmds[0]; dcp->dc_name != NULL; dcp++) {
        if (mdb_module_remove_dcmd(t->t_module, dcp->dc_name) == -1)
            warn("failed to remove dcmd %s", dcp->dc_name);
    }

    mdb_prop_postmortem = FALSE;
    mdb_prop_kernel = FALSE;
    mdb_prop_datamodel = MDB_TGT_MODEL_UNKNOWN;
}

/*ARGSUSED*/
const char *
kt_name(mdb_tgt_t *t)
{
    return ("kvm");
}

const char *
kt_platform(mdb_tgt_t *t)
{
    kt_data_t *kt = t->t_data;
    return (kt->k_platform);
}

int
kt_uname(mdb_tgt_t *t, struct utsname *utsp)
{
    return (mdb_tgt_readsym(t, MDB_TGT_AS_VIRT, utsp,
        sizeof (struct utsname), MDB_TGT_OBJ_EXEC, "utsname"));
}

/*ARGSUSED*/
int
kt_dmodel(mdb_tgt_t *t)
{
    return (MDB_TGT_MODEL_NATIVE);
}

ssize_t
kt_aread(mdb_tgt_t *t, mdb_tgt_as_t as, void *buf,
    size_t nbytes, mdb_tgt_addr_t addr)
{
    kt_data_t *kt = t->t_data;
    ssize_t rval;

    if ((rval = kt->k_kb_ops->kb_aread(kt->k_cookie, addr, buf,
        nbytes, as)) == -1)
        return (set_errno(EMDB_NOMAP));

    return (rval);
}

ssize_t
kt_awrite(mdb_tgt_t *t, mdb_tgt_as_t as, const void *buf,
    size_t nbytes, mdb_tgt_addr_t addr)
{
    kt_data_t *kt = t->t_data;
    ssize_t rval;

    if ((rval = kt->k_kb_ops->kb_awrite(kt->k_cookie, addr, buf,
        nbytes, as)) == -1)
        return (set_errno(EMDB_NOMAP));

    return (rval);
}

ssize_t
kt_vread(mdb_tgt_t *t, void *buf, size_t nbytes, uintptr_t addr)
{
    kt_data_t *kt = t->t_data;
    ssize_t rval;

    if ((rval = kt->k_kb_ops->kb_kread(kt->k_cookie, addr, buf,
        nbytes)) == -1)
        return (set_errno(EMDB_NOMAP));

    return (rval);
}

ssize_t
kt_vwrite(mdb_tgt_t *t, const void *buf, size_t nbytes, uintptr_t addr)
{
    kt_data_t *kt = t->t_data;
    ssize_t rval;

    if ((rval = kt->k_kb_ops->kb_kwrite(kt->k_cookie, addr, buf,
        nbytes)) == -1)
        return (set_errno(EMDB_NOMAP));

    return (rval);
}

ssize_t
kt_fread(mdb_tgt_t *t, void *buf, size_t nbytes, uintptr_t addr)
{
    return (kt_vread(t, buf, nbytes, addr));
}

ssize_t
kt_fwrite(mdb_tgt_t *t, const void *buf, size_t nbytes, uintptr_t addr)
{
    return (kt_vwrite(t, buf, nbytes, addr));
}

ssize_t
kt_pread(mdb_tgt_t *t, void *buf, size_t nbytes, physaddr_t addr)
{
    kt_data_t *kt = t->t_data;
    ssize_t rval;

    if ((rval = kt->k_kb_ops->kb_pread(kt->k_cookie, addr, buf,
        nbytes)) == -1)
        return (set_errno(EMDB_NOMAP));

    return (rval);
}

ssize_t
kt_pwrite(mdb_tgt_t *t, const void *buf, size_t nbytes, physaddr_t addr)
{
    kt_data_t *kt = t->t_data;
    ssize_t rval;

    if ((rval = kt->k_kb_ops->kb_pwrite(kt->k_cookie, addr, buf,
        nbytes)) == -1)
        return (set_errno(EMDB_NOMAP));

    return (rval);
}

int
kt_vtop(mdb_tgt_t *t, mdb_tgt_as_t as, uintptr_t va, physaddr_t *pap)
{
    kt_data_t *kt = t->t_data;

    struct as *asp;
    physaddr_t pa;
    mdb_module_t *mod;
    mdb_var_t *v;
    int (*fptr)(uintptr_t, struct as *, physaddr_t *);

    switch ((uintptr_t)as) {
    case (uintptr_t)MDB_TGT_AS_PHYS:
    case (uintptr_t)MDB_TGT_AS_FILE:
    case (uintptr_t)MDB_TGT_AS_IO:
        return (set_errno(EINVAL));
    case (uintptr_t)MDB_TGT_AS_VIRT:
        asp = kt->k_as;
        break;
    default:
        asp = (struct as *)as;
    }

    if ((pa = kt->k_kb_ops->kb_vtop(kt->k_cookie, asp, va)) != -1ULL) {
        *pap = pa;
        return (0);
    }

    if ((v = mdb_nv_lookup(&mdb.m_modules, "unix")) != NULL &&
        (mod = mdb_nv_get_cookie(v)) != NULL) {

        fptr = (int (*)(uintptr_t, struct as *, physaddr_t *))
            dlsym(mod->mod_hdl, "platform_vtop");

        if ((fptr != NULL) && ((*fptr)(va, asp, pap) == 0))
            return (0);
    }

    return (set_errno(EMDB_NOMAP));
}

int
kt_lookup_by_name(mdb_tgt_t *t, const char *obj, const char *name,
    GElf_Sym *symp, mdb_syminfo_t *sip)
{
    kt_data_t *kt = t->t_data;
    kt_module_t *km, kmod;
    mdb_var_t *v;
    int n;

    /*
     * To simplify the implementation, we create a fake module on the stack
     * which is "prepended" to k_modlist and whose symtab is kt->k_symtab.
     */
    kmod.km_symtab = kt->k_symtab;
    kmod.km_list.ml_next = mdb_list_next(&kt->k_modlist);

    switch ((uintptr_t)obj) {
    case (uintptr_t)MDB_TGT_OBJ_EXEC:
        km = &kmod;
        n = 1;
        break;

    case (uintptr_t)MDB_TGT_OBJ_EVERY:
        km = &kmod;
        n = mdb_nv_size(&kt->k_modules) + 1;
        break;

    case (uintptr_t)MDB_TGT_OBJ_RTLD:
        obj = kt->k_rtld_name;
        /*FALLTHRU*/

    default:
        if ((v = mdb_nv_lookup(&kt->k_modules, obj)) == NULL)
            return (set_errno(EMDB_NOOBJ));

        km = mdb_nv_get_cookie(v);
        n = 1;

        if (km->km_symtab == NULL)
            kt_load_module(kt, t, km);
    }

    for (; n > 0; n--, km = mdb_list_next(km)) {
        if (mdb_gelf_symtab_lookup_by_name(km->km_symtab, name,
            symp, &sip->sym_id) == 0) {
            sip->sym_table = MDB_TGT_SYMTAB;
            return (0);
        }
    }

    return (set_errno(EMDB_NOSYM));
}

int
kt_lookup_by_addr(mdb_tgt_t *t, uintptr_t addr, uint_t flags,
    char *buf, size_t nbytes, GElf_Sym *symp, mdb_syminfo_t *sip)
{
    kt_data_t *kt = t->t_data;
    kt_module_t kmods[3], *kmods_begin = &kmods[0], *kmods_end;
    const char *name;

    kt_module_t *km = &kmods[0];    /* Point km at first fake module */
    kt_module_t *sym_km = NULL; /* Module associated with best sym */
    GElf_Sym sym;           /* Best symbol found so far if !exact */
    uint_t symid;           /* ID of best symbol found so far */

    /*
     * To simplify the implementation, we create fake modules on the stack
     * that are "prepended" to k_modlist and whose symtab is set to
     * each of three special symbol tables, in order of precedence.
     */
    km->km_symtab = mdb.m_prsym;

    if (kt->k_symtab != NULL) {
        km->km_list.ml_next = (mdb_list_t *)(km + 1);
        km = mdb_list_next(km);
        km->km_symtab = kt->k_symtab;
    }

    if (kt->k_dynsym != NULL) {
        km->km_list.ml_next = (mdb_list_t *)(km + 1);
        km = mdb_list_next(km);
        km->km_symtab = kt->k_dynsym;
    }

    km->km_list.ml_next = mdb_list_next(&kt->k_modlist);
    kmods_end = km;

    /*
     * Now iterate over the list of fake and real modules.  If the module
     * has no symbol table and the address is in the text section,
     * instantiate the module's symbol table.  In exact mode, we can
     * jump to 'found' immediately if we match.  Otherwise we continue
     * looking and improve our choice if we find a closer symbol.
     */
    for (km = &kmods[0]; km != NULL; km = mdb_list_next(km)) {
        if (km->km_symtab == NULL && addr >= km->km_text_va &&
            addr < km->km_text_va + km->km_text_size)
            kt_load_module(kt, t, km);

        if (mdb_gelf_symtab_lookup_by_addr(km->km_symtab, addr,
            flags, buf, nbytes, symp, &sip->sym_id) != 0 ||
            symp->st_value == 0)
            continue;

        if (flags & MDB_TGT_SYM_EXACT) {
            sym_km = km;
            goto found;
        }

        if (sym_km == NULL || mdb_gelf_sym_closer(symp, &sym, addr)) {
            sym_km = km;
            sym = *symp;
            symid = sip->sym_id;
        }
    }

    if (sym_km == NULL)
        return (set_errno(EMDB_NOSYMADDR));

    *symp = sym; /* Copy our best symbol into the caller's symbol */
    sip->sym_id = symid;
found:
    /*
     * Once we've found something, copy the final name into the caller's
     * buffer and prefix it with the load object name if appropriate.
     */
    if (sym_km != NULL) {
        name = mdb_gelf_sym_name(sym_km->km_symtab, symp);

        if (sym_km < kmods_begin || sym_km > kmods_end) {
            (void) mdb_snprintf(buf, nbytes, "%s`%s",
                sym_km->km_name, name);
        } else if (nbytes > 0) {
            (void) strncpy(buf, name, nbytes);
            buf[nbytes - 1] = '\0';
        }

        if (sym_km->km_symtab == mdb.m_prsym)
            sip->sym_table = MDB_TGT_PRVSYM;
        else
            sip->sym_table = MDB_TGT_SYMTAB;
    } else {
        sip->sym_table = MDB_TGT_SYMTAB;
    }

    return (0);
}

static int
kt_symtab_func(void *data, const GElf_Sym *sym, const char *name, uint_t id)
{
    kt_symarg_t *argp = data;

    if (mdb_tgt_sym_match(sym, argp->sym_type)) {
        argp->sym_info.sym_id = id;

        return (argp->sym_cb(argp->sym_data, sym, name,
            &argp->sym_info, argp->sym_obj));
    }

    return (0);
}

static void
kt_symtab_iter(mdb_gelf_symtab_t *gst, uint_t type, const char *obj,
    mdb_tgt_sym_f *cb, void *p)
{
    kt_symarg_t arg;

    arg.sym_cb = cb;
    arg.sym_data = p;
    arg.sym_type = type;
    arg.sym_info.sym_table = gst->gst_tabid;
    arg.sym_obj = obj;

    mdb_gelf_symtab_iter(gst, kt_symtab_func, &arg);
}

int
kt_symbol_iter(mdb_tgt_t *t, const char *obj, uint_t which, uint_t type,
    mdb_tgt_sym_f *cb, void *data)
{
    kt_data_t *kt = t->t_data;
    kt_module_t *km;

    mdb_gelf_symtab_t *symtab = NULL;
    mdb_var_t *v;

    switch ((uintptr_t)obj) {
    case (uintptr_t)MDB_TGT_OBJ_EXEC:
        if (which == MDB_TGT_SYMTAB)
            symtab = kt->k_symtab;
        else
            symtab = kt->k_dynsym;
        break;

    case (uintptr_t)MDB_TGT_OBJ_EVERY:
        if (which == MDB_TGT_DYNSYM) {
            symtab = kt->k_dynsym;
            obj = MDB_TGT_OBJ_EXEC;
            break;
        }

        mdb_nv_rewind(&kt->k_modules);
        while ((v = mdb_nv_advance(&kt->k_modules)) != NULL) {
            km = mdb_nv_get_cookie(v);

            if (km->km_symtab == NULL)
                kt_load_module(kt, t, km);

            if (km->km_symtab != NULL)
                kt_symtab_iter(km->km_symtab, type,
                    km->km_name, cb, data);
        }
        break;

    case (uintptr_t)MDB_TGT_OBJ_RTLD:
        obj = kt->k_rtld_name;
        /*FALLTHRU*/

    default:
        v = mdb_nv_lookup(&kt->k_modules, obj);

        if (v == NULL)
            return (set_errno(EMDB_NOOBJ));

        km = mdb_nv_get_cookie(v);

        if (km->km_symtab == NULL)
            kt_load_module(kt, t, km);

        symtab = km->km_symtab;
    }

    if (symtab)
        kt_symtab_iter(symtab, type, obj, cb, data);

    return (0);
}

static int
kt_mapping_walk(uintptr_t addr, const void *data, kt_maparg_t *marg)
{
    /*
     * This is a bit sketchy but avoids problematic compilation of this
     * target against the current VM implementation.  Now that we have
     * vmem, we can make this less broken and more informative by changing
     * this code to invoke the vmem walker in the near future.
     */
    const struct kt_seg {
        caddr_t s_base;
        size_t s_size;
    } *segp = (const struct kt_seg *)data;

    mdb_map_t map;
    GElf_Sym sym;
    mdb_syminfo_t info;

    map.map_base = (uintptr_t)segp->s_base;
    map.map_size = segp->s_size;
    map.map_flags = MDB_TGT_MAP_R | MDB_TGT_MAP_W | MDB_TGT_MAP_X;

    if (kt_lookup_by_addr(marg->map_target, addr, MDB_TGT_SYM_EXACT,
        map.map_name, MDB_TGT_MAPSZ, &sym, &info) == -1) {

        (void) mdb_iob_snprintf(map.map_name, MDB_TGT_MAPSZ,
            "%lr", addr);
    }

    return (marg->map_cb(marg->map_data, &map, map.map_name));
}

int
kt_mapping_iter(mdb_tgt_t *t, mdb_tgt_map_f *func, void *private)
{
    kt_data_t *kt = t->t_data;
    kt_maparg_t m;

    m.map_target = t;
    m.map_cb = func;
    m.map_data = private;

    return (mdb_pwalk("seg", (mdb_walk_cb_t)kt_mapping_walk, &m,
        (uintptr_t)kt->k_as));
}

static const mdb_map_t *
kt_module_to_map(kt_module_t *km, mdb_map_t *map)
{
    (void) strncpy(map->map_name, km->km_name, MDB_TGT_MAPSZ);
    map->map_name[MDB_TGT_MAPSZ - 1] = '\0';
    map->map_base = km->km_text_va;
    map->map_size = km->km_text_size;
    map->map_flags = MDB_TGT_MAP_R | MDB_TGT_MAP_W | MDB_TGT_MAP_X;

    return (map);
}

int
kt_object_iter(mdb_tgt_t *t, mdb_tgt_map_f *func, void *private)
{
    kt_data_t *kt = t->t_data;
    kt_module_t *km;
    mdb_map_t m;

    for (km = mdb_list_next(&kt->k_modlist); km; km = mdb_list_next(km)) {
        if (func(private, kt_module_to_map(km, &m), km->km_name) == -1)
            break;
    }

    return (0);
}

const mdb_map_t *
kt_addr_to_map(mdb_tgt_t *t, uintptr_t addr)
{
    kt_data_t *kt = t->t_data;
    kt_module_t *km;

    for (km = mdb_list_next(&kt->k_modlist); km; km = mdb_list_next(km)) {
        if (addr - km->km_text_va < km->km_text_size ||
            addr - km->km_data_va < km->km_data_size ||
            addr - km->km_bss_va < km->km_bss_size)
            return (kt_module_to_map(km, &kt->k_map));
    }

    (void) set_errno(EMDB_NOMAP);
    return (NULL);
}

const mdb_map_t *
kt_name_to_map(mdb_tgt_t *t, const char *name)
{
    kt_data_t *kt = t->t_data;
    kt_module_t *km;
    mdb_map_t m;

    /*
     * If name is MDB_TGT_OBJ_EXEC, return the first module on the list,
     * which will be unix since we keep k_modlist in load order.
     */
    if (name == MDB_TGT_OBJ_EXEC)
        return (kt_module_to_map(mdb_list_next(&kt->k_modlist), &m));

    if (name == MDB_TGT_OBJ_RTLD)
        name = kt->k_rtld_name;

    if ((km = kt_module_by_name(kt, name)) != NULL)
        return (kt_module_to_map(km, &m));

    (void) set_errno(EMDB_NOOBJ);
    return (NULL);
}

static ctf_file_t *
kt_load_ctfdata(mdb_tgt_t *t, kt_module_t *km)
{
    kt_data_t *kt = t->t_data;
    int err;

    if (km->km_ctfp != NULL)
        return (km->km_ctfp);

    if (km->km_ctf_va == NULL) {
        (void) set_errno(EMDB_NOCTF);
        return (NULL);
    }

    if (km->km_symtab == NULL)
        kt_load_module(t->t_data, t, km);

    if ((km->km_ctf_buf = mdb_alloc(km->km_ctf_size, UM_NOSLEEP)) == NULL) {
        warn("failed to allocate memory to load %s debugging "
            "information", km->km_name);
        return (NULL);
    }

    if (mdb_tgt_vread(t, km->km_ctf_buf, km->km_ctf_size,
        km->km_ctf_va) != km->km_ctf_size) {
        warn("failed to read %lu bytes of debug data for %s at %p",
            (ulong_t)km->km_ctf_size, km->km_name,
            (void *)km->km_ctf_va);
        mdb_free(km->km_ctf_buf, km->km_ctf_size);
        km->km_ctf_buf = NULL;
        return (NULL);
    }

    if ((km->km_ctfp = mdb_ctf_bufopen((const void *)km->km_ctf_buf,
        km->km_ctf_size, km->km_symbuf, &km->km_symtab_hdr,
        km->km_strtab, &km->km_strtab_hdr, &err)) == NULL) {
        mdb_free(km->km_ctf_buf, km->km_ctf_size);
        km->km_ctf_buf = NULL;
        (void) set_errno(ctf_to_errno(err));
        return (NULL);
    }

    mdb_dprintf(MDB_DBG_KMOD, "loaded %lu bytes of CTF data for %s\n",
        (ulong_t)km->km_ctf_size, km->km_name);

    if (ctf_parent_name(km->km_ctfp) != NULL) {
        mdb_var_t *v;

        if ((v = mdb_nv_lookup(&kt->k_modules,
            ctf_parent_name(km->km_ctfp))) == NULL) {
            warn("failed to load CTF data for %s - parent %s not "
                "loaded\n", km->km_name,
                ctf_parent_name(km->km_ctfp));
        }

        if (v != NULL) {
            kt_module_t *pm = mdb_nv_get_cookie(v);

            if (pm->km_ctfp == NULL)
                (void) kt_load_ctfdata(t, pm);

            if (pm->km_ctfp != NULL && ctf_import(km->km_ctfp,
                pm->km_ctfp) == CTF_ERR) {
                warn("failed to import parent types into "
                    "%s: %s\n", km->km_name,
                    ctf_errmsg(ctf_errno(km->km_ctfp)));
            }
        }
    }

    return (km->km_ctfp);
}

ctf_file_t *
kt_addr_to_ctf(mdb_tgt_t *t, uintptr_t addr)
{
    kt_data_t *kt = t->t_data;
    kt_module_t *km;

    for (km = mdb_list_next(&kt->k_modlist); km; km = mdb_list_next(km)) {
        if (addr - km->km_text_va < km->km_text_size ||
            addr - km->km_data_va < km->km_data_size ||
            addr - km->km_bss_va < km->km_bss_size)
            return (kt_load_ctfdata(t, km));
    }

    (void) set_errno(EMDB_NOMAP);
    return (NULL);
}

ctf_file_t *
kt_name_to_ctf(mdb_tgt_t *t, const char *name)
{
    kt_data_t *kt = t->t_data;
    kt_module_t *km;

    if (name == MDB_TGT_OBJ_EXEC)
        name = KT_CTFPARENT;
    else if (name == MDB_TGT_OBJ_RTLD)
        name = kt->k_rtld_name;

    if ((km = kt_module_by_name(kt, name)) != NULL)
        return (kt_load_ctfdata(t, km));

    (void) set_errno(EMDB_NOOBJ);
    return (NULL);
}

/*ARGSUSED*/
int
kt_status(mdb_tgt_t *t, mdb_tgt_status_t *tsp)
{
    kt_data_t *kt = t->t_data;
    bzero(tsp, sizeof (mdb_tgt_status_t));
    tsp->st_state = (kt->k_xpv_domu || (kt->k_dumphdr != NULL)) ?
        MDB_TGT_DEAD : MDB_TGT_RUNNING;
    return (0);
}

static ssize_t
kt_xd_dumphdr(mdb_tgt_t *t, void *buf, size_t nbytes)
{
    kt_data_t *kt = t->t_data;

    if (buf == NULL && nbytes == 0)
        return (sizeof (dumphdr_t));

    if (kt->k_dumphdr == NULL)
        return (set_errno(ENODATA));

    nbytes = MIN(nbytes, sizeof (dumphdr_t));
    bcopy(kt->k_dumphdr, buf, nbytes);

    return (nbytes);
}

void
kt_destroy(mdb_tgt_t *t)
{
    kt_data_t *kt = t->t_data;
    kt_module_t *km, *nkm;

    (void) mdb_module_unload(KT_MODULE, 0);

    if (kt->k_regs != NULL)
        mdb_free(kt->k_regs, kt->k_regsize);

    if (kt->k_symtab != NULL)
        mdb_gelf_symtab_destroy(kt->k_symtab);

    if (kt->k_dynsym != NULL)
        mdb_gelf_symtab_destroy(kt->k_dynsym);

    if (kt->k_dumphdr != NULL)
        mdb_free(kt->k_dumphdr, sizeof (dumphdr_t));

    mdb_gelf_destroy(kt->k_file);

    (void) kt->k_kb_ops->kb_close(kt->k_cookie);

    for (km = mdb_list_next(&kt->k_modlist); km; km = nkm) {
        if (km->km_symtab)
            mdb_gelf_symtab_destroy(km->km_symtab);

        if (km->km_data)
            mdb_free(km->km_data, km->km_datasz);

        if (km->km_ctfp)
            ctf_close(km->km_ctfp);

        if (km->km_ctf_buf != NULL)
            mdb_free(km->km_ctf_buf, km->km_ctf_size);

        nkm = mdb_list_next(km);
        strfree(km->km_name);
        mdb_free(km, sizeof (kt_module_t));
    }

    mdb_nv_destroy(&kt->k_modules);

    strfree(kt->k_kvmfile);
    if (kt->k_symfile != NULL)
        strfree(kt->k_symfile);

    mdb_free(kt, sizeof (kt_data_t));
}

static int
kt_data_stub(void)
{
    return (-1);
}

int
mdb_kvm_tgt_create(mdb_tgt_t *t, int argc, const char *argv[])
{
    kt_data_t *kt = mdb_zalloc(sizeof (kt_data_t), UM_SLEEP);
    mdb_kb_ops_t *kvm_kb_ops = libkvm_kb_ops();
    int oflag = (t->t_flags & MDB_TGT_F_RDWR) ? O_RDWR : O_RDONLY;
    struct utsname uts;
    GElf_Sym sym;
    pgcnt_t pmem;


    if (argc == 2) {
        kt->k_symfile = strdup(argv[0]);
        kt->k_kvmfile = strdup(argv[1]);

        kt->k_cookie = kvm_kb_ops->kb_open(kt->k_symfile,
            kt->k_kvmfile, NULL, oflag, (char *)mdb.m_pname);

        if (kt->k_cookie == NULL)
            goto err;

        kt->k_xpv_domu = 0;
        kt->k_kb_ops = kvm_kb_ops;
    } else {
#ifndef __x86
        return (set_errno(EINVAL));
#else
        mdb_kb_ops_t *(*getops)(void);

        kt->k_symfile = NULL;
        kt->k_kvmfile = strdup(argv[0]);

        getops = (mdb_kb_ops_t *(*)())dlsym(RTLD_NEXT, "mdb_kb_ops");

        /*
         * Load mdb_kb if it's not already loaded during
         * identification.
         */
        if (getops == NULL) {
            (void) mdb_module_load("mdb_kb",
                MDB_MOD_GLOBAL | MDB_MOD_SILENT);
            getops = (mdb_kb_ops_t *(*)())
                dlsym(RTLD_NEXT, "mdb_kb_ops");
        }

        if (getops == NULL || (kt->k_kb_ops = getops()) == NULL) {
            warn("failed to load KVM backend ops\n");
            goto err;
        }

        kt->k_cookie = kt->k_kb_ops->kb_open(NULL, kt->k_kvmfile, NULL,
            oflag, (char *)mdb.m_pname);

        if (kt->k_cookie == NULL)
            goto err;

        kt->k_xpv_domu = 1;
#endif
    }

    if ((kt->k_fio = kt->k_kb_ops->kb_sym_io(kt->k_cookie,
        kt->k_symfile)) == NULL)
        goto err;

    if ((kt->k_file = mdb_gelf_create(kt->k_fio,
        ET_EXEC, GF_FILE)) == NULL) {
        mdb_io_destroy(kt->k_fio);
        goto err;
    }

    kt->k_symtab =
        mdb_gelf_symtab_create_file(kt->k_file, SHT_SYMTAB, MDB_TGT_SYMTAB);

    kt->k_dynsym =
        mdb_gelf_symtab_create_file(kt->k_file, SHT_DYNSYM, MDB_TGT_DYNSYM);

    if (mdb_gelf_symtab_lookup_by_name(kt->k_symtab, "kas",
        &sym, NULL) == -1) {
        warn("'kas' symbol is missing from kernel\n");
        goto err;
    }

    kt->k_as = (struct as *)(uintptr_t)sym.st_value;

    if (mdb_gelf_symtab_lookup_by_name(kt->k_symtab, "platform",
        &sym, NULL) == -1) {
        warn("'platform' symbol is missing from kernel\n");
        goto err;
    }

    if (kt->k_kb_ops->kb_kread(kt->k_cookie, sym.st_value,
        kt->k_platform, MAXNAMELEN) <= 0) {
        warn("failed to read 'platform' string from kernel");
        goto err;
    }

    if (mdb_gelf_symtab_lookup_by_name(kt->k_symtab, "utsname",
        &sym, NULL) == -1) {
        warn("'utsname' symbol is missing from kernel\n");
        goto err;
    }

    if (kt->k_kb_ops->kb_kread(kt->k_cookie, sym.st_value, &uts,
        sizeof (uts)) <= 0) {
        warn("failed to read 'utsname' struct from kernel");
        goto err;
    }

    kt->k_dump_print_content = (void (*)())kt_data_stub;
    kt->k_dump_find_curproc = kt_data_stub;

    /*
     * We set k_ctfvalid based on the presence of the CTF vmem arena
     * symbol.  The CTF members were added to the end of struct module at
     * the same time, so this allows us to know whether we can use them.
     */
    if (mdb_gelf_symtab_lookup_by_name(kt->k_symtab, "ctf_arena", &sym,
        NULL) == 0 && !(mdb.m_flags & MDB_FL_NOCTF))
        kt->k_ctfvalid = 1;

    (void) mdb_nv_create(&kt->k_modules, UM_SLEEP);
    t->t_pshandle = kt->k_cookie;
    t->t_data = kt;

#if defined(__sparc)
#if defined(__sparcv9)
    kt_sparcv9_init(t);
#else
    kt_sparcv7_init(t);
#endif
#elif defined(__amd64)
    kt_amd64_init(t);
#elif defined(__i386)
    kt_ia32_init(t);
#else
#error  "unknown ISA"
#endif

    /*
     * We read our representative thread ID (address) from the kernel's
     * global panic_thread.  It will remain 0 if this is a live kernel.
     */
    (void) mdb_tgt_readsym(t, MDB_TGT_AS_VIRT, &kt->k_tid, sizeof (void *),
        MDB_TGT_OBJ_EXEC, "panic_thread");

    if ((mdb.m_flags & MDB_FL_ADB) && mdb_tgt_readsym(t, MDB_TGT_AS_VIRT,
        &pmem, sizeof (pmem), MDB_TGT_OBJ_EXEC, "physmem") == sizeof (pmem))
        mdb_printf("physmem %lx\n", (ulong_t)pmem);

    /*
     * If this is not a live kernel or a hypervisor dump, read the dump
     * header.  We don't have to sanity-check the header, as the open would
     * not have succeeded otherwise.
     */
    if (!kt->k_xpv_domu && strcmp(kt->k_symfile, "/dev/ksyms") != 0) {
        mdb_io_t *vmcore;

        kt->k_dumphdr = mdb_alloc(sizeof (dumphdr_t), UM_SLEEP);

        if ((vmcore = mdb_fdio_create_path(NULL, kt->k_kvmfile,
            O_RDONLY, 0)) == NULL) {
            mdb_warn("failed to open %s", kt->k_kvmfile);
            goto err;
        }

        if (IOP_READ(vmcore, kt->k_dumphdr, sizeof (dumphdr_t)) !=
            sizeof (dumphdr_t)) {
            mdb_warn("failed to read dump header");
            mdb_io_destroy(vmcore);
            goto err;
        }

        mdb_io_destroy(vmcore);

        (void) mdb_tgt_xdata_insert(t, "dumphdr",
            "dump header structure", kt_xd_dumphdr);
    }

    return (0);

err:
    if (kt->k_dumphdr != NULL)
        mdb_free(kt->k_dumphdr, sizeof (dumphdr_t));

    if (kt->k_symtab != NULL)
        mdb_gelf_symtab_destroy(kt->k_symtab);

    if (kt->k_dynsym != NULL)
        mdb_gelf_symtab_destroy(kt->k_dynsym);

    if (kt->k_file != NULL)
        mdb_gelf_destroy(kt->k_file);

    if (kt->k_cookie != NULL)
        (void) kt->k_kb_ops->kb_close(kt->k_cookie);

    mdb_free(kt, sizeof (kt_data_t));
    return (-1);
}

int
mdb_kvm_is_dump(mdb_io_t *io)
{
    dumphdr_t h;

    (void) IOP_SEEK(io, (off64_t)0L, SEEK_SET);

    return (IOP_READ(io, &h, sizeof (dumphdr_t)) == sizeof (dumphdr_t) &&
        h.dump_magic == DUMP_MAGIC);
}

int
mdb_kvm_is_compressed_dump(mdb_io_t *io)
{
    dumphdr_t h;

    (void) IOP_SEEK(io, (off64_t)0L, SEEK_SET);

    return (IOP_READ(io, &h, sizeof (dumphdr_t)) == sizeof (dumphdr_t) &&
        h.dump_magic == DUMP_MAGIC &&
        (h.dump_flags & DF_COMPRESSED) != 0);
}