/*      $OpenBSD: dmesg.c,v 1.33 2022/12/04 23:50:46 cheloha Exp $      */
/*      $NetBSD: dmesg.c,v 1.8 1995/03/18 14:54:49 cgd Exp $    */

/*-
 * 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.
 */

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

#include <err.h>
#include <fcntl.h>
#include <kvm.h>
#include <limits.h>
#include <nlist.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <vis.h>

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

void usage(void);

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

int
main(int argc, char *argv[])
{
        int ch, newl, skip, i;
        char *p;
        struct msgbuf cur;
        char *memf, *nlistf, *bufdata = NULL;
        char *allocated = NULL;
        int startupmsgs = 0;
        char buf[5];

        memf = nlistf = NULL;
        while ((ch = getopt(argc, argv, "sM:N:")) != -1)
                switch(ch) {
                case 's':
                        startupmsgs = 1;
                        break;
                case 'M':
                        memf = optarg;
                        break;
                case 'N':
                        nlistf = optarg;
                        break;
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;

        if (argc != 0)
                usage();

        if (memf == NULL && nlistf == NULL) {
                int mib[2], msgbufsize;
                size_t len;

                mib[0] = CTL_KERN;
                mib[1] = startupmsgs ? KERN_CONSBUFSIZE : KERN_MSGBUFSIZE;
                len = sizeof(msgbufsize);
                if (sysctl(mib, 2, &msgbufsize, &len, NULL, 0))
                        err(1, "sysctl: %s", startupmsgs ? "KERN_CONSBUFSIZE" :
                            "KERN_MSGBUFSIZE");

                msgbufsize += offsetof(struct msgbuf, msg_bufc);
                allocated = bufdata = calloc(1, msgbufsize);
                if (bufdata == NULL)
                        errx(1, "couldn't allocate space for buffer data");

                mib[1] = startupmsgs ? KERN_CONSBUF : KERN_MSGBUF;
                len = msgbufsize;
                if (sysctl(mib, 2, bufdata, &len, NULL, 0))
                        err(1, "sysctl: %s",
                            startupmsgs ? "KERN_CONSBUF" : "KERN_MSGBUF");

                if (pledge("stdio", NULL) == -1)
                        err(1, "pledge");

                memcpy(&cur, bufdata, sizeof(cur));
                bufdata = ((struct msgbuf *)bufdata)->msg_bufc;
        } else {
#ifndef NOKVM
                struct msgbuf *bufp;
                kvm_t *kd;

                /* Read in kernel message buffer, do sanity checks. */
                if ((kd = kvm_open(nlistf, memf, NULL, O_RDONLY,
                    "dmesg")) == NULL)
                        return (1);

                if (pledge("stdio", NULL) == -1)
                        err(1, "pledge");

                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");
                if (KREAD(nl[X_MSGBUF].n_value, bufp))
                        errx(1, "kvm_read: %s: (0x%lx)", kvm_geterr(kd),
                            nl[X_MSGBUF].n_value);
                if (KREAD((long)bufp, cur))
                        errx(1, "kvm_read: %s (%0lx)", kvm_geterr(kd),
                            (unsigned long)bufp);
                if (cur.msg_magic != MSG_MAGIC)
                        errx(1, "magic number incorrect");
                allocated = bufdata = malloc(cur.msg_bufs);
                if (bufdata == NULL)
                        errx(1, "couldn't allocate space for buffer data");
                if (kvm_read(kd, (long)&bufp->msg_bufc, bufdata,
                    cur.msg_bufs) != cur.msg_bufs)
                        errx(1, "kvm_read: %s", kvm_geterr(kd));
                kvm_close(kd);
#endif
        }

        if (cur.msg_bufx >= cur.msg_bufs)
                cur.msg_bufx = 0;
        /*
         * The message buffer is circular; start at the read pointer, and
         * go to the write pointer - 1.
         */
        for (newl = skip = i = 0, p = bufdata + cur.msg_bufx;
            i < cur.msg_bufs; i++, p++) {
                if (p == bufdata + cur.msg_bufs)
                        p = bufdata;
                ch = *p;
                /* Skip "\n<.*>" syslog sequences. */
                if (skip) {
                        if (ch == '>')
                                newl = skip = 0;
                        continue;
                }
                if (newl && ch == '<') {
                        skip = 1;
                        continue;
                }
                if (ch == '\0')
                        continue;
                newl = ch == '\n';
                vis(buf, ch, 0, 0);
                if (buf[1] == 0)
                        putchar(buf[0]);
                else
                        printf("%s", buf);
        }
        if (!newl)
                putchar('\n');
        free(allocated);
        return (0);
}

void
usage(void)
{
        extern char *__progname;

        fprintf(stderr, "usage: %s [-s] [-M core] [-N system]\n", __progname);
        exit(1);
}