/*-
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * 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.
 *
 * @(#) Copyright (c) 1991, 1993 The Regents of the University of California.  All rights reserved.
 * @(#)dmesg.c  8.1 (Berkeley) 6/5/93
 * $FreeBSD: src/sbin/dmesg/dmesg.c,v 1.11.2.3 2001/08/08 22:32:15 obrien Exp $
 */

#include <sys/types.h>
#include <sys/msgbuf.h>
#include <sys/sysctl.h>
#include <sys/stat.h>

#include <err.h>
#include <fcntl.h>
#include <kvm.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <vis.h>
#include <sys/syslog.h>

static struct nlist nl[] = {
#define X_MSGBUF        0
        { "_msgbufp",   0, 0, 0, 0 },
        { NULL,         0, 0, 0, 0 },
};

static void dumpbuf(char *bp, size_t bufpos, size_t buflen,
                    int *newl, int *skip, int *pri);
static void usage(void) __dead2;

#define KREAD(addr, var) \
        kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var)

#define INCRBUFSIZE     65536

static int all_opt;

int
main(int argc, char **argv)
{
        int newl, skip;
        struct msgbuf *bufp, cur;
        char *bp, *memf, *nlistf;
        kvm_t *kd;
        int ch;
        int clear = 0;
        int pri = 0;
        int tailmode = 0;
        int kno;
        size_t buflen, bufpos;
        struct stat st;

        setlocale(LC_CTYPE, "");
        memf = nlistf = NULL;
        while ((ch = getopt(argc, argv, "acfM:N:n:")) != -1) {
                switch(ch) {
                case 'a':
                        all_opt++;
                        break;
                case 'c':
                        clear = 1;
                        break;
                case 'f':
                        ++tailmode;
                        break;
                case 'M':
                        memf = optarg;
                        break;
                case 'N':
                        nlistf = optarg;
                        break;
                case 'n':
                        kno = strtol(optarg, NULL, 0);
                        asprintf(&memf, "vmcore.%d", kno);
                        asprintf(&nlistf, "kern.%d", kno);
                        if (stat(memf, &st) || stat(nlistf, &st)) {
                                free(memf);
                                free(nlistf);
                                asprintf(&memf, "/var/crash/vmcore.%d", kno);
                                asprintf(&nlistf, "/var/crash/kern.%d", kno);
                        }
                        break;
                case '?':
                default:
                        usage();
                }
        }
        argc -= optind;
        argv += optind;

        newl = 1;
        skip = 0;
        pri = 0;

        if (memf == NULL && nlistf == NULL && tailmode == 0) {
                /* Running kernel. Use sysctl. */
                buflen = 0;
                if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1)
                        err(1, "sysctl kern.msgbuf");
                if (buflen == 0)        /* can happen if msgbuf was cleared */
                        buflen = 1;

                if ((bp = malloc(buflen)) == NULL)
                        errx(1, "malloc failed");
                if (sysctlbyname("kern.msgbuf", bp, &buflen, NULL, 0) == -1)
                        err(1, "sysctl kern.msgbuf");
                /* We get a dewrapped buffer using sysctl. */
                bufpos = 0;
                dumpbuf(bp, bufpos, buflen, &newl, &skip, &pri);
        } else {
                u_int rindex;
                u_int xindex;
                u_int ri;
                u_int xi;
                u_int n;

                /* Read in kernel message buffer, do sanity checks. */
                kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg");
                if (kd == NULL)
                        exit (1);
                if (kvm_nlist(kd, nl) == -1)
                        errx(1, "kvm_nlist: %s", kvm_geterr(kd));
                if (nl[X_MSGBUF].n_type == 0)
                        errx(1, "%s: msgbufp not found",
                            nlistf ? nlistf : "namelist");
                bp = malloc(INCRBUFSIZE);
                if (!bp)
                        errx(1, "malloc failed");
                if (KREAD(nl[X_MSGBUF].n_value, bufp))
                        errx(1, "kvm_read: %s", kvm_geterr(kd));
                if (KREAD((long)bufp, cur))
                        errx(1, "kvm_read: %s", kvm_geterr(kd));
                if (cur.msg_magic != MSG_MAGIC && cur.msg_magic != MSG_OMAGIC)
                        errx(1, "kernel message buffer has different magic "
                            "number");

                /*
                 * NOTE: current algorithm is compatible with both old and
                 *       new msgbuf structures.  The new structure doesn't
                 *       modulo the indexes (so we do), and adds a separate
                 *       log index which we don't access here.
                 */

                rindex = cur.msg_bufr;

                for (;;) {
                        /*
                         * Calculate index for dump and do sanity clipping.
                         */
                        xindex = cur.msg_bufx;
                        n = xindex - rindex;
                        if (n > cur.msg_size - 1024) {
                                rindex = xindex - cur.msg_size + 2048;
                                n = xindex - rindex;
                        }
                        ri = rindex % cur.msg_size;
                        xi = xindex % cur.msg_size;

                        if (ri < xi)
                                buflen = xi - ri;
                        else
                                buflen = cur.msg_size - ri;
                        if (buflen > n)
                                buflen = n;
                        if (buflen > INCRBUFSIZE)
                                buflen = INCRBUFSIZE;

                        if (kvm_read(kd, (long)cur.msg_ptr + ri,
                                     bp, buflen) != (ssize_t)buflen) {
                                errx(1, "kvm_read: %s", kvm_geterr(kd));
                        }
                        if (buflen)
                                dumpbuf(bp, 0, buflen, &newl, &skip, &pri);
                        ri = (ri + buflen) % cur.msg_size;
                        n = n - buflen;
                        rindex += buflen;
                        if ((int)n <= 0) {
                                if (tailmode == 0)
                                        break;
                                fflush(stdout);
                                if (tailmode == 1)
                                        sleep(1);
                        }
                        if (KREAD((long)bufp, cur))
                                errx(1, "kvm_read: %s", kvm_geterr(kd));
                }
                kvm_close(kd);
        }
        if (!newl)
                putchar('\n');
        if (clear) {
                if (sysctlbyname("kern.msgbuf_clear", NULL, NULL,
                                 &clear, sizeof(int)) != 0) {
                        err(1, "sysctl kern.msgbuf_clear");
                }
        }
        return(0);
}

static
void
dumpbuf(char *bp, size_t bufpos, size_t buflen,
        int *newl, int *skip, int *pri)
{
        int ch;
        char *p, *ep;
        char buf[5];

        /*
         * The message buffer is circular.  If the buffer has wrapped, the
         * write pointer points to the oldest data.  Otherwise, the write
         * pointer points to \0's following the data.  Read the entire
         * buffer starting at the write pointer and ignore nulls so that
         * we effectively start at the oldest data.
         */
        p = bp + bufpos;
        ep = (bufpos == 0 ? bp + buflen : p);
        do {
                if (p == bp + buflen)
                        p = bp;
                ch = *p;
                /* Skip "\n<.*>" syslog sequences. */
                if (*skip) {
                        if (ch == '\n') {
                                *skip = 0;
                                *newl = 1;
                        } if (ch == '>') {
                                if (LOG_FAC(*pri) == LOG_KERN)
                                        *newl = *skip = 0;
                        } else if (ch >= '0' && ch <= '9') {
                                *pri *= 10;
                                *pri += ch - '0';
                        }
                        continue;
                }
                if (*newl && ch == '<' && all_opt == 0) {
                        *pri = 0;
                        *skip = 1;
                        continue;
                }
                if (ch == '\0')
                        continue;
                *newl = (ch == '\n');
                vis(buf, ch, VIS_NOSLASH, 0);
                if (buf[1] == 0)
                        putchar(buf[0]);
                else
                        printf("%s", buf);
        } while (++p != ep);
}

static void
usage(void)
{
        fprintf(stderr, "usage: dmesg [-ac] [-M core] [-N system]\n");
        exit(1);
}