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4784a46912
with a new implementation that has a mostly reentrant "addchar" routine, supports multiple message buffers in the kernel, and hides the implementation details from callers. The new code uses a kind of sequence number to represend the current read and write positions in the buffer. This approach (suggested mainly by bde) permits the read and write pointers to be maintained separately, which reduces the number of atomic operations that are required. The "mostly reentrant" above refers to the way that while it is now always safe to have any number of concurrent writers, readers could see the message buffer after a writer has advanced the pointers but before it has witten the new character. Discussed on: freebsd-arch
196 lines
5.4 KiB
C
196 lines
5.4 KiB
C
/*-
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* Copyright (c) 1991, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if 0
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#ifndef lint
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static const char copyright[] =
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"@(#) Copyright (c) 1991, 1993\n\
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The Regents of the University of California. All rights reserved.\n";
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#endif /* not lint */
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#ifndef lint
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static const char sccsid[] = "@(#)dmesg.c 8.1 (Berkeley) 6/5/93";
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#endif /* not lint */
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#endif
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/types.h>
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#include <sys/msgbuf.h>
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#include <sys/sysctl.h>
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#include <err.h>
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#include <fcntl.h>
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#include <kvm.h>
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#include <locale.h>
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#include <nlist.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <vis.h>
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#include <sys/syslog.h>
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struct nlist nl[] = {
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#define X_MSGBUF 0
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{ "_msgbufp" },
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{ NULL },
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};
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void usage(void) __dead2;
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#define KREAD(addr, var) \
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kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var)
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int
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main(int argc, char *argv[])
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{
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int ch, newl, skip;
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char *p, *ep;
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struct msgbuf *bufp, cur;
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char *bp, *memf, *nlistf;
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kvm_t *kd;
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char buf[5];
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int all = 0;
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int pri;
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size_t buflen, bufpos;
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(void) setlocale(LC_CTYPE, "");
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memf = nlistf = NULL;
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while ((ch = getopt(argc, argv, "aM:N:")) != -1)
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switch(ch) {
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case 'a':
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all++;
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break;
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case 'M':
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memf = optarg;
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break;
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case 'N':
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nlistf = optarg;
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break;
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case '?':
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default:
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usage();
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}
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argc -= optind;
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argv += optind;
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if (memf == NULL && nlistf == NULL) {
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/* Running kernel. Use sysctl. */
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if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1)
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err(1, "sysctl kern.msgbuf");
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if ((bp = malloc(buflen)) == NULL)
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errx(1, "malloc failed");
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if (sysctlbyname("kern.msgbuf", bp, &buflen, NULL, 0) == -1)
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err(1, "sysctl kern.msgbuf");
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/* We get a dewrapped buffer using sysctl. */
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bufpos = 0;
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} else {
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/* Read in kernel message buffer, do sanity checks. */
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kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg");
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if (kd == NULL)
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exit (1);
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if (kvm_nlist(kd, nl) == -1)
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errx(1, "kvm_nlist: %s", kvm_geterr(kd));
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if (nl[X_MSGBUF].n_type == 0)
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errx(1, "%s: msgbufp not found",
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nlistf ? nlistf : "namelist");
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if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur))
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errx(1, "kvm_read: %s", kvm_geterr(kd));
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if (cur.msg_magic != MSG_MAGIC)
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errx(1, "kernel message buffer has different magic "
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"number");
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bp = malloc(cur.msg_size);
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if (!bp)
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errx(1, "malloc failed");
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if (kvm_read(kd, (long)cur.msg_ptr, bp, cur.msg_size) !=
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cur.msg_size)
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errx(1, "kvm_read: %s", kvm_geterr(kd));
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kvm_close(kd);
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buflen = cur.msg_size;
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bufpos = MSGBUF_SEQ_TO_POS(&cur, cur.msg_wseq);
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}
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/*
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* The message buffer is circular. If the buffer has wrapped, the
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* write pointer points to the oldest data. Otherwise, the write
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* pointer points to \0's following the data. Read the entire
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* buffer starting at the write pointer and ignore nulls so that
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* we effectively start at the oldest data.
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*/
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p = bp + bufpos;
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ep = (bufpos == 0 ? bp + buflen : p);
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newl = skip = 0;
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do {
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if (p == bp + buflen)
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p = bp;
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ch = *p;
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/* Skip "\n<.*>" syslog sequences. */
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if (skip) {
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if (ch == '\n') {
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skip = 0;
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newl = 1;
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} if (ch == '>') {
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if (LOG_FAC(pri) == LOG_KERN || all)
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newl = skip = 0;
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} else if (ch >= '0' && ch <= '9') {
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pri *= 10;
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pri += ch - '0';
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}
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continue;
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}
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if (newl && ch == '<') {
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pri = 0;
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skip = 1;
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continue;
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}
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if (ch == '\0')
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continue;
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newl = ch == '\n';
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(void)vis(buf, ch, 0, 0);
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if (buf[1] == 0)
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(void)putchar(buf[0]);
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else
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(void)printf("%s", buf);
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} while (++p != ep);
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if (!newl)
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(void)putchar('\n');
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exit(0);
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}
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void
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usage(void)
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{
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(void)fprintf(stderr, "usage: dmesg [-a] [-M core] [-N system]\n");
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exit(1);
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}
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