/*      $OpenBSD: kvm.c,v 1.72 2022/02/22 17:35:01 deraadt Exp $ */
/*      $NetBSD: kvm.c,v 1.43 1996/05/05 04:31:59 gwr Exp $     */

/*-
 * Copyright (c) 1989, 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software developed by the Computer Systems
 * Engineering group at Lawrence Berkeley Laboratory under DARPA contract
 * BG 91-66 and contributed to Berkeley.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>  /* MID_MACHINE */
#include <sys/types.h>
#include <sys/signal.h>
#include <sys/proc.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/sysctl.h>

#include <sys/core.h>
#include <sys/exec.h>
#include <sys/kcore.h>

#include <stddef.h>
#include <errno.h>
#include <ctype.h>
#include <db.h>
#include <fcntl.h>
#include <libgen.h>
#include <limits.h>
#include <nlist.h>
#include <paths.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <kvm.h>
#include <stdarg.h>

#include "kvm_private.h"

extern int __fdnlist(int, struct nlist *);

static int      kvm_dbopen(kvm_t *, const char *);
static int      kvm_opennamelist(kvm_t *, const char *);
static int      _kvm_get_header(kvm_t *);
static kvm_t    *_kvm_open(kvm_t *, const char *, const char *, const char *,
                     int, char *);
static int      clear_gap(kvm_t *, FILE *, int);

char *
kvm_geterr(kvm_t *kd)
{
        return (kd->errbuf);
}

/*
 * Wrapper around pread.
 */
ssize_t
_kvm_pread(kvm_t *kd, int fd, void *buf, size_t nbytes, off_t offset)
{
        ssize_t rval;

        errno = 0;
        rval = pread(fd, buf, nbytes, offset);
        if (rval == -1 || errno != 0) {
                _kvm_syserr(kd, kd->program, "pread");
        }
        return (rval);
}

/*
 * Wrapper around pwrite.
 */
ssize_t
_kvm_pwrite(kvm_t *kd, int fd, const void *buf, size_t nbytes, off_t offset)
{
        ssize_t rval;

        errno = 0;
        rval = pwrite(fd, buf, nbytes, offset);
        if (rval == -1 || errno != 0) {
                _kvm_syserr(kd, kd->program, "pwrite");
        }
        return (rval);
}

/*
 * Report an error using printf style arguments.  "program" is kd->program
 * on hard errors, and 0 on soft errors, so that under sun error emulation,
 * only hard errors are printed out (otherwise, programs like gdb will
 * generate tons of error messages when trying to access bogus pointers).
 */
void
_kvm_err(kvm_t *kd, const char *program, const char *fmt, ...)
{
        va_list ap;

        va_start(ap, fmt);
        if (program != NULL) {
                (void)fprintf(stderr, "%s: ", program);
                (void)vfprintf(stderr, fmt, ap);
                (void)fputc('\n', stderr);
        } else
                (void)vsnprintf(kd->errbuf,
                    sizeof(kd->errbuf), fmt, ap);

        va_end(ap);
}

void
_kvm_syserr(kvm_t *kd, const char *program, const char *fmt, ...)
{
        va_list ap;
        size_t n;

        va_start(ap, fmt);
        if (program != NULL) {
                (void)fprintf(stderr, "%s: ", program);
                (void)vfprintf(stderr, fmt, ap);
                (void)fprintf(stderr, ": %s\n", strerror(errno));
        } else {
                char *cp = kd->errbuf;

                (void)vsnprintf(cp, sizeof(kd->errbuf), fmt, ap);
                n = strlen(cp);
                (void)snprintf(&cp[n], sizeof(kd->errbuf) - n, ": %s",
                    strerror(errno));
        }
        va_end(ap);
}

void *
_kvm_malloc(kvm_t *kd, size_t n)
{
        void *p;

        if ((p = malloc(n)) == NULL)
                _kvm_err(kd, kd->program, "%s", strerror(errno));
        return (p);
}

void *
_kvm_realloc(kvm_t *kd, void *p, size_t n)
{
        if ((p = realloc(p, n)) == NULL)
                _kvm_err(kd, kd->program, "%s", strerror(errno));
        return (p);
}

static kvm_t *
_kvm_open(kvm_t *kd, const char *uf, const char *mf, const char *sf,
    int flag, char *errout)
{
        struct stat st;

        kd->db = 0;
        kd->pmfd = -1;
        kd->vmfd = -1;
        kd->swfd = -1;
        kd->nlfd = -1;
        kd->alive = 0;
        kd->filebase = NULL;
        kd->procbase = NULL;
        kd->nbpg = getpagesize();
        kd->swapspc = 0;
        kd->argspc = 0;
        kd->argbuf = 0;
        kd->argv = 0;
        kd->envspc = 0;
        kd->envbuf = 0;
        kd->envp = 0;
        kd->vmst = NULL;
        kd->vm_page_buckets = 0;
        kd->kcore_hdr = 0;
        kd->cpu_dsize = 0;
        kd->cpu_data = 0;
        kd->dump_off = 0;

        if (flag & KVM_NO_FILES) {
                kd->alive = 1;
                return (kd);
        }

        if (uf && strlen(uf) >= PATH_MAX) {
                _kvm_err(kd, kd->program, "exec file name too long");
                goto failed;
        }
        if (flag != O_RDONLY && flag != O_WRONLY && flag != O_RDWR) {
                _kvm_err(kd, kd->program, "bad flags arg");
                goto failed;
        }
        flag |= O_CLOEXEC;

        if (mf == NULL)
                mf = _PATH_MEM;

        if ((kd->pmfd = open(mf, flag)) == -1) {
                _kvm_syserr(kd, kd->program, "%s", mf);
                goto failed;
        }
        if (fstat(kd->pmfd, &st) == -1) {
                _kvm_syserr(kd, kd->program, "%s", mf);
                goto failed;
        }
        if (S_ISCHR(st.st_mode)) {
                /*
                 * If this is a character special device, then check that
                 * it's /dev/mem.  If so, open kmem too.  (Maybe we should
                 * make it work for either /dev/mem or /dev/kmem -- in either
                 * case you're working with a live kernel.)
                 */
                if (strcmp(mf, _PATH_MEM) != 0) {       /* XXX */
                        _kvm_err(kd, kd->program,
                                 "%s: not physical memory device", mf);
                        goto failed;
                }
                if ((kd->vmfd = open(_PATH_KMEM, flag)) == -1) {
                        _kvm_syserr(kd, kd->program, "%s", _PATH_KMEM);
                        goto failed;
                }
                kd->alive = 1;
                if (sf != NULL && (kd->swfd = open(sf, flag)) == -1) {
                        _kvm_syserr(kd, kd->program, "%s", sf);
                        goto failed;
                }
                /*
                 * Open kvm nlist database.  We only try to use
                 * the pre-built database if the namelist file name
                 * pointer is NULL.  If the database cannot or should
                 * not be opened, open the namelist argument so we
                 * revert to slow nlist() calls.
                 * If no file is specified, try opening _PATH_KSYMS and
                 * fall back to _PATH_UNIX.
                 */
                if (kvm_dbopen(kd, uf ? uf : _PATH_UNIX) == -1 &&
                    kvm_opennamelist(kd, uf))
                        goto failed;
        } else {
                /*
                 * This is a crash dump.
                 * Initialize the virtual address translation machinery,
                 * but first setup the namelist fd.
                 * If no file is specified, try opening _PATH_KSYMS and
                 * fall back to _PATH_UNIX.
                 */
                if (kvm_opennamelist(kd, uf))
                        goto failed;

                /*
                 * If there is no valid core header, fail silently here.
                 * The address translations however will fail without
                 * header. Things can be made to run by calling
                 * kvm_dump_mkheader() before doing any translation.
                 */
                if (_kvm_get_header(kd) == 0) {
                        if (_kvm_initvtop(kd) < 0)
                                goto failed;
                }
        }
        return (kd);
failed:
        /*
         * Copy out the error if doing sane error semantics.
         */
        if (errout != 0)
                (void)strlcpy(errout, kd->errbuf, _POSIX2_LINE_MAX);
        (void)kvm_close(kd);
        return (0);
}

static int
kvm_opennamelist(kvm_t *kd, const char *uf)
{
        int fd;

        if (uf != NULL)
                fd = open(uf, O_RDONLY | O_CLOEXEC);
        else {
                fd = open(_PATH_KSYMS, O_RDONLY | O_CLOEXEC);
                uf = _PATH_UNIX;
                if (fd == -1)
                        fd = open(uf, O_RDONLY | O_CLOEXEC);
        }
        if (fd == -1) {
                _kvm_syserr(kd, kd->program, "%s", uf);
                return (-1);
        }

        kd->nlfd = fd;
        return (0);
}

/*
 * The kernel dump file (from savecore) contains:
 *    kcore_hdr_t kcore_hdr;
 *    kcore_seg_t cpu_hdr;
 *    (opaque)    cpu_data; (size is cpu_hdr.c_size)
 *    kcore_seg_t mem_hdr;
 *    (memory)    mem_data; (size is mem_hdr.c_size)
 *
 * Note: khdr is padded to khdr.c_hdrsize;
 * cpu_hdr and mem_hdr are padded to khdr.c_seghdrsize
 */
static int
_kvm_get_header(kvm_t *kd)
{
        kcore_hdr_t     kcore_hdr;
        kcore_seg_t     cpu_hdr;
        kcore_seg_t     mem_hdr;
        size_t          offset;
        ssize_t         sz;

        /*
         * Read the kcore_hdr_t
         */
        sz = _kvm_pread(kd, kd->pmfd, &kcore_hdr, sizeof(kcore_hdr), (off_t)0);
        if (sz != sizeof(kcore_hdr)) {
                return (-1);
        }

        /*
         * Currently, we only support dump-files made by the current
         * architecture...
         */
        if ((CORE_GETMAGIC(kcore_hdr) != KCORE_MAGIC) ||
            (CORE_GETMID(kcore_hdr) != MID_MACHINE))
                return (-1);

        /*
         * Currently, we only support exactly 2 segments: cpu-segment
         * and data-segment in exactly that order.
         */
        if (kcore_hdr.c_nseg != 2)
                return (-1);

        /*
         * Save away the kcore_hdr.  All errors after this
         * should do a to "goto fail" to deallocate things.
         */
        kd->kcore_hdr = _kvm_malloc(kd, sizeof(kcore_hdr));
        if (kd->kcore_hdr == NULL)
                goto fail;
        memcpy(kd->kcore_hdr, &kcore_hdr, sizeof(kcore_hdr));
        offset = kcore_hdr.c_hdrsize;

        /*
         * Read the CPU segment header
         */
        sz = _kvm_pread(kd, kd->pmfd, &cpu_hdr, sizeof(cpu_hdr), (off_t)offset);
        if (sz != sizeof(cpu_hdr)) {
                goto fail;
        }

        if ((CORE_GETMAGIC(cpu_hdr) != KCORESEG_MAGIC) ||
            (CORE_GETFLAG(cpu_hdr) != CORE_CPU))
                goto fail;
        offset += kcore_hdr.c_seghdrsize;

        /*
         * Read the CPU segment DATA.
         */
        kd->cpu_dsize = cpu_hdr.c_size;
        kd->cpu_data = _kvm_malloc(kd, (size_t)cpu_hdr.c_size);
        if (kd->cpu_data == NULL)
                goto fail;

        sz = _kvm_pread(kd, kd->pmfd, kd->cpu_data, (size_t)cpu_hdr.c_size,
            (off_t)offset);
        if (sz != (size_t)cpu_hdr.c_size) {
                goto fail;
        }

        offset += cpu_hdr.c_size;

        /*
         * Read the next segment header: data segment
         */
        sz = _kvm_pread(kd, kd->pmfd, &mem_hdr, sizeof(mem_hdr), (off_t)offset);
        if (sz != sizeof(mem_hdr)) {
                goto fail;
        }

        offset += kcore_hdr.c_seghdrsize;

        if ((CORE_GETMAGIC(mem_hdr) != KCORESEG_MAGIC) ||
            (CORE_GETFLAG(mem_hdr) != CORE_DATA))
                goto fail;

        kd->dump_off = offset;
        return (0);

fail:
        free(kd->kcore_hdr);
        kd->kcore_hdr = NULL;
        if (kd->cpu_data != NULL) {
                free(kd->cpu_data);
                kd->cpu_data = NULL;
                kd->cpu_dsize = 0;
        }

        return (-1);
}

/*
 * The format while on the dump device is: (new format)
 *    kcore_seg_t cpu_hdr;
 *    (opaque)    cpu_data; (size is cpu_hdr.c_size)
 *    kcore_seg_t mem_hdr;
 *    (memory)    mem_data; (size is mem_hdr.c_size)
 */
int
kvm_dump_mkheader(kvm_t *kd, off_t dump_off)
{
        kcore_seg_t     cpu_hdr;
        int     hdr_size;
        ssize_t sz;

        if (kd->kcore_hdr != NULL) {
            _kvm_err(kd, kd->program, "already has a dump header");
            return (-1);
        }
        if (ISALIVE(kd)) {
                _kvm_err(kd, kd->program, "don't use on live kernel");
                return (-1);
        }

        /*
         * Validate new format crash dump
         */
        sz = _kvm_pread(kd, kd->pmfd, &cpu_hdr, sizeof(cpu_hdr), (off_t)dump_off);
        if (sz != sizeof(cpu_hdr)) {
                return (-1);
        }
        if ((CORE_GETMAGIC(cpu_hdr) != KCORE_MAGIC)
                || (CORE_GETMID(cpu_hdr) != MID_MACHINE)) {
                _kvm_err(kd, 0, "invalid magic in cpu_hdr");
                return (-1);
        }
        hdr_size = _ALIGN(sizeof(cpu_hdr));

        /*
         * Read the CPU segment.
         */
        kd->cpu_dsize = cpu_hdr.c_size;
        kd->cpu_data = _kvm_malloc(kd, kd->cpu_dsize);
        if (kd->cpu_data == NULL)
                goto fail;

        sz = _kvm_pread(kd, kd->pmfd, kd->cpu_data, (size_t)cpu_hdr.c_size,
            (off_t)dump_off+hdr_size);
        if (sz != (ssize_t)cpu_hdr.c_size) {
                _kvm_err(kd, 0, "invalid size in cpu_hdr");
                goto fail;
        }
        hdr_size += kd->cpu_dsize;

        /*
         * Leave phys mem pointer at beginning of memory data
         */
        kd->dump_off = dump_off + hdr_size;
        errno = 0;
        if (lseek(kd->pmfd, kd->dump_off, SEEK_SET) != kd->dump_off && errno != 0) {
                _kvm_err(kd, 0, "invalid dump offset - lseek");
                goto fail;
        }

        /*
         * Create a kcore_hdr.
         */
        kd->kcore_hdr = _kvm_malloc(kd, sizeof(kcore_hdr_t));
        if (kd->kcore_hdr == NULL)
                goto fail;

        kd->kcore_hdr->c_hdrsize    = _ALIGN(sizeof(kcore_hdr_t));
        kd->kcore_hdr->c_seghdrsize = _ALIGN(sizeof(kcore_seg_t));
        kd->kcore_hdr->c_nseg       = 2;
        CORE_SETMAGIC(*(kd->kcore_hdr), KCORE_MAGIC, MID_MACHINE,0);

        /*
         * Now that we have a valid header, enable translations.
         */
        if (_kvm_initvtop(kd) == 0)
                /* Success */
                return (hdr_size);

fail:
        free(kd->kcore_hdr);
        kd->kcore_hdr = NULL;
        if (kd->cpu_data != NULL) {
                free(kd->cpu_data);
                kd->cpu_data = NULL;
                kd->cpu_dsize = 0;
        }
        return (-1);
}

static int
clear_gap(kvm_t *kd, FILE *fp, int size)
{
        if (size <= 0) /* XXX - < 0 should never happen */
                return (0);
        while (size-- > 0) {
                if (fputc(0, fp) == EOF) {
                        _kvm_syserr(kd, kd->program, "clear_gap");
                        return (-1);
                }
        }
        return (0);
}

/*
 * Write the dump header info to 'fp'. Note that we can't use fseek(3) here
 * because 'fp' might be a file pointer obtained by zopen().
 */
int
kvm_dump_wrtheader(kvm_t *kd, FILE *fp, int dumpsize)
{
        kcore_seg_t     seghdr;
        long            offset;
        int             gap;

        if (kd->kcore_hdr == NULL || kd->cpu_data == NULL) {
                _kvm_err(kd, kd->program, "no valid dump header(s)");
                return (-1);
        }

        /*
         * Write the generic header
         */
        offset = 0;
        if (fwrite(kd->kcore_hdr, sizeof(kcore_hdr_t), 1, fp) < 1) {
                _kvm_syserr(kd, kd->program, "kvm_dump_wrtheader");
                return (-1);
        }
        offset += kd->kcore_hdr->c_hdrsize;
        gap     = kd->kcore_hdr->c_hdrsize - sizeof(kcore_hdr_t);
        if (clear_gap(kd, fp, gap) == -1)
                return (-1);

        /*
         * Write the cpu header
         */
        CORE_SETMAGIC(seghdr, KCORESEG_MAGIC, 0, CORE_CPU);
        seghdr.c_size = (u_long)_ALIGN(kd->cpu_dsize);
        if (fwrite(&seghdr, sizeof(seghdr), 1, fp) < 1) {
                _kvm_syserr(kd, kd->program, "kvm_dump_wrtheader");
                return (-1);
        }
        offset += kd->kcore_hdr->c_seghdrsize;
        gap     = kd->kcore_hdr->c_seghdrsize - sizeof(seghdr);
        if (clear_gap(kd, fp, gap) == -1)
                return (-1);

        if (fwrite(kd->cpu_data, kd->cpu_dsize, 1, fp) < 1) {
                _kvm_syserr(kd, kd->program, "kvm_dump_wrtheader");
                return (-1);
        }
        offset += seghdr.c_size;
        gap     = seghdr.c_size - kd->cpu_dsize;
        if (clear_gap(kd, fp, gap) == -1)
                return (-1);

        /*
         * Write the actual dump data segment header
         */
        CORE_SETMAGIC(seghdr, KCORESEG_MAGIC, 0, CORE_DATA);
        seghdr.c_size = dumpsize;
        if (fwrite(&seghdr, sizeof(seghdr), 1, fp) < 1) {
                _kvm_syserr(kd, kd->program, "kvm_dump_wrtheader");
                return (-1);
        }
        offset += kd->kcore_hdr->c_seghdrsize;
        gap     = kd->kcore_hdr->c_seghdrsize - sizeof(seghdr);
        if (clear_gap(kd, fp, gap) == -1)
                return (-1);

        return (offset);
}

kvm_t *
kvm_openfiles(const char *uf, const char *mf, const char *sf,
    int flag, char *errout)
{
        kvm_t *kd;

        if ((kd = malloc(sizeof(*kd))) == NULL) {
                (void)strlcpy(errout, strerror(errno), _POSIX2_LINE_MAX);
                return (0);
        }
        kd->program = 0;
        return (_kvm_open(kd, uf, mf, sf, flag, errout));
}

kvm_t *
kvm_open(const char *uf, const char *mf, const char *sf, int flag,
    const char *program)
{
        kvm_t *kd;

        if ((kd = malloc(sizeof(*kd))) == NULL && program != NULL) {
                (void)fprintf(stderr, "%s: %s\n", program, strerror(errno));
                return (0);
        }
        kd->program = program;
        return (_kvm_open(kd, uf, mf, sf, flag, NULL));
}

int
kvm_close(kvm_t *kd)
{
        int error = 0;

        if (kd->pmfd >= 0)
                error |= close(kd->pmfd);
        if (kd->vmfd >= 0)
                error |= close(kd->vmfd);
        kd->alive = 0;
        if (kd->nlfd >= 0)
                error |= close(kd->nlfd);
        if (kd->swfd >= 0)
                error |= close(kd->swfd);
        if (kd->db != 0)
                error |= (kd->db->close)(kd->db);
        if (kd->vmst)
                _kvm_freevtop(kd);
        kd->cpu_dsize = 0;
        free(kd->cpu_data);
        free(kd->kcore_hdr);
        free(kd->filebase);
        free(kd->procbase);
        free(kd->swapspc);
        free(kd->argspc);
        free(kd->argbuf);
        free(kd->argv);
        free(kd->envspc);
        free(kd->envbuf);
        free(kd->envp);
        free(kd);

        return (error);
}
DEF(kvm_close);

/*
 * Set up state necessary to do queries on the kernel namelist
 * data base.  If the data base is out-of-data/incompatible with
 * given executable, set up things so we revert to standard nlist call.
 * Only called for live kernels.  Return 0 on success, -1 on failure.
 */
static int
kvm_dbopen(kvm_t *kd, const char *uf)
{
        char dbversion[_POSIX2_LINE_MAX], kversion[_POSIX2_LINE_MAX];
        char dbname[PATH_MAX], ufbuf[PATH_MAX];
        struct nlist nitem;
        size_t dbversionlen;
        DBT rec;

        strlcpy(ufbuf, uf, sizeof(ufbuf));
        uf = basename(ufbuf);

        (void)snprintf(dbname, sizeof(dbname), "%skvm_%s.db", _PATH_VARDB, uf);
        kd->db = dbopen(dbname, O_RDONLY, 0, DB_HASH, NULL);
        if (kd->db == NULL) {
                switch (errno) {
                case ENOENT:
                        /* No kvm_bsd.db, fall back to /bsd silently */
                        break;
                case EFTYPE:
                        _kvm_err(kd, kd->program,
                            "file %s is incorrectly formatted", dbname);
                        break;
                case EINVAL:
                        _kvm_err(kd, kd->program,
                            "invalid argument to dbopen()");
                        break;
                default:
                        _kvm_err(kd, kd->program, "unknown dbopen() error");
                        break;
                }
                return (-1);
        }

        /*
         * read version out of database
         */
        rec.data = VRS_KEY;
        rec.size = sizeof(VRS_KEY) - 1;
        if ((kd->db->get)(kd->db, (DBT *)&rec, (DBT *)&rec, 0))
                goto close;
        if (rec.data == 0 || rec.size > sizeof(dbversion))
                goto close;

        bcopy(rec.data, dbversion, rec.size);
        dbversionlen = rec.size;

        /*
         * Read version string from kernel memory.
         * Since we are dealing with a live kernel, we can call kvm_read()
         * at this point.
         */
        rec.data = VRS_SYM;
        rec.size = sizeof(VRS_SYM) - 1;
        if ((kd->db->get)(kd->db, (DBT *)&rec, (DBT *)&rec, 0))
                goto close;
        if (rec.data == 0 || rec.size != sizeof(struct nlist))
                goto close;
        bcopy(rec.data, &nitem, sizeof(nitem));
        if (kvm_read(kd, (u_long)nitem.n_value, kversion, dbversionlen) !=
            dbversionlen)
                goto close;
        /*
         * If they match, we win - otherwise clear out kd->db so
         * we revert to slow nlist().
         */
        if (bcmp(dbversion, kversion, dbversionlen) == 0)
                return (0);
close:
        (void)(kd->db->close)(kd->db);
        kd->db = 0;

        return (-1);
}

int
kvm_nlist(kvm_t *kd, struct nlist *nl)
{
        struct nlist *p;
        int nvalid, rv;

        /*
         * If we can't use the data base, revert to the
         * slow library call.
         */
        if (kd->db == 0) {
                rv = __fdnlist(kd->nlfd, nl);
                if (rv == -1)
                        _kvm_err(kd, 0, "bad namelist");
                return (rv);
        }

        /*
         * We can use the kvm data base.  Go through each nlist entry
         * and look it up with a db query.
         */
        nvalid = 0;
        for (p = nl; p->n_name && p->n_name[0]; ++p) {
                size_t len;
                DBT rec;

                if ((len = strlen(p->n_name)) > 4096) {
                        /* sanity */
                        _kvm_err(kd, kd->program, "symbol too large");
                        return (-1);
                }
                rec.data = p->n_name;
                rec.size = len;

                /*
                 * Make sure that n_value = 0 when the symbol isn't found
                 */
                p->n_value = 0;

                if ((kd->db->get)(kd->db, (DBT *)&rec, (DBT *)&rec, 0))
                        continue;
                if (rec.data == 0 || rec.size != sizeof(struct nlist))
                        continue;
                ++nvalid;
                /*
                 * Avoid alignment issues.
                 */
                bcopy((char *)rec.data + offsetof(struct nlist, n_type),
                    &p->n_type, sizeof(p->n_type));
                bcopy((char *)rec.data + offsetof(struct nlist, n_value),
                    &p->n_value, sizeof(p->n_value));
        }
        /*
         * Return the number of entries that weren't found.
         */
        return ((p - nl) - nvalid);
}
DEF(kvm_nlist);

int
kvm_dump_inval(kvm_t *kd)
{
        struct nlist    nl[2];
        u_long          x;
        paddr_t         pa;

        if (ISALIVE(kd)) {
                _kvm_err(kd, kd->program, "clearing dump on live kernel");
                return (-1);
        }
        nl[0].n_name = "_dumpmag";
        nl[1].n_name = NULL;

        if (kvm_nlist(kd, nl) == -1) {
                _kvm_err(kd, 0, "bad namelist");
                return (-1);
        }

        if (nl[0].n_value == 0) {
                _kvm_err(kd, nl[0].n_name, "not in name list");
                return (-1);
        }

        if (_kvm_kvatop(kd, (u_long)nl[0].n_value, &pa) == 0)
                return (-1);

        x = 0;
        if (_kvm_pwrite(kd, kd->pmfd, &x, sizeof(x),
            (off_t)_kvm_pa2off(kd, pa)) != sizeof(x)) {
                _kvm_err(kd, 0, "cannot invalidate dump");
                return (-1);
        }
        return (0);
}

ssize_t
kvm_read(kvm_t *kd, u_long kva, void *buf, size_t len)
{
        ssize_t cc;
        void *cp;

        if (ISALIVE(kd)) {
                /*
                 * We're using /dev/kmem.  Just read straight from the
                 * device and let the active kernel do the address translation.
                 */
                cc = _kvm_pread(kd, kd->vmfd, buf, len, (off_t)kva);
                if (cc == -1) {
                        _kvm_err(kd, 0, "invalid address (%lx)", kva);
                        return (-1);
                } else if (cc < len)
                        _kvm_err(kd, kd->program, "short read");
                return (cc);
        } else {
                if ((kd->kcore_hdr == NULL) || (kd->cpu_data == NULL)) {
                        _kvm_err(kd, kd->program, "no valid dump header");
                        return (-1);
                }
                cp = buf;
                while (len > 0) {
                        paddr_t pa;

                        /* In case of error, _kvm_kvatop sets the err string */
                        cc = _kvm_kvatop(kd, kva, &pa);
                        if (cc == 0)
                                return (-1);
                        if (cc > len)
                                cc = len;
                        cc = _kvm_pread(kd, kd->pmfd, cp, (size_t)cc,
                            (off_t)_kvm_pa2off(kd, pa));
                        if (cc == -1) {
                                _kvm_syserr(kd, 0, _PATH_MEM);
                                break;
                        }
                        /*
                         * If kvm_kvatop returns a bogus value or our core
                         * file is truncated, we might wind up seeking beyond
                         * the end of the core file in which case the read will
                         * return 0 (EOF).
                         */
                        if (cc == 0)
                                break;
                        cp = (char *)cp + cc;
                        kva += cc;
                        len -= cc;
                }
                return ((char *)cp - (char *)buf);
        }
        /* NOTREACHED */
}
DEF(kvm_read);

ssize_t
kvm_write(kvm_t *kd, u_long kva, const void *buf, size_t len)
{
        int cc;

        if (ISALIVE(kd)) {
                /*
                 * Just like kvm_read, only we write.
                 */
                cc = _kvm_pwrite(kd, kd->vmfd, buf, len, (off_t)kva);
                if (cc == -1) {
                        _kvm_err(kd, 0, "invalid address (%lx)", kva);
                        return (-1);
                } else if (cc < len)
                        _kvm_err(kd, kd->program, "short write");
                return (cc);
        } else {
                _kvm_err(kd, kd->program,
                    "kvm_write not implemented for dead kernels");
                return (-1);
        }
        /* NOTREACHED */
}