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Don't print the oldest line in the message buffer if the buffer is

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full, since that line is almost always incomplete. Make the parsing
of <%d> lines more strict.

Also simplify the logic a little:
 - Start off by making the buffer linear so that we don't have to
   deal with it wrapping around (suggested by bde).
 - Process line by line rather than byte at a time.
This commit is contained in:
Ian Dowse 2004-02-05 21:07:50 +00:00
parent 4c3558aa82
commit 59f256ec35
1 changed files with 56 additions and 53 deletions
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109
sbin/dmesg/dmesg.c
View File

@ -56,6 +56,7 @@ __FBSDID("$FreeBSD$");
#include <nlist.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <vis.h>
#include <sys/syslog.h>
@ -74,16 +75,14 @@ void usage(void) __dead2;
int
main(int argc, char *argv[])
{
int ch, newl, skip;
char *p, *ep;
struct msgbuf *bufp, cur;
char *bp, *memf, *nlistf;
char *bp, *ep, *memf, *nextp, *nlistf, *p, *q;
kvm_t *kd;
char buf[5];
int all = 0;
int pri;
size_t buflen, bufpos;
int all, ch, pri;
char buf[5];
all = 0;
(void) setlocale(LC_CTYPE, "");
memf = nlistf = NULL;
while ((ch = getopt(argc, argv, "aM:N:")) != -1)
@ -105,15 +104,13 @@ main(int argc, char *argv[])
argv += optind;
if (memf == NULL && nlistf == NULL) {
/* Running kernel. Use sysctl. */
/* Running kernel. Use sysctl to get an unwrapped buffer. */
if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1)
err(1, "sysctl kern.msgbuf");
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;
} else {
/* Read in kernel message buffer, do sanity checks. */
kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg");
@ -132,58 +129,64 @@ main(int argc, char *argv[])
bp = malloc(cur.msg_size);
if (!bp)
errx(1, "malloc failed");
if (kvm_read(kd, (long)cur.msg_ptr, bp, cur.msg_size) !=
cur.msg_size)
/* Unwrap the circular buffer to start from the oldest data. */
bufpos = MSGBUF_SEQ_TO_POS(&cur, cur.msg_wseq);
if (kvm_read(kd, (long)&cur.msg_ptr[bufpos], bp,
cur.msg_size - bufpos) != cur.msg_size - bufpos)
errx(1, "kvm_read: %s", kvm_geterr(kd));
if (bufpos != 0 && kvm_read(kd, (long)cur.msg_ptr,
&bp[cur.msg_size - bufpos], bufpos) != bufpos)
errx(1, "kvm_read: %s", kvm_geterr(kd));
kvm_close(kd);
buflen = cur.msg_size;
bufpos = MSGBUF_SEQ_TO_POS(&cur, cur.msg_wseq);
}
/*
* 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.
* The message buffer is circular, but has been unwrapped so that
* the oldest data comes first. The data will be preceded by \0's
* if the message buffer was not full.
*/
p = bp + bufpos;
ep = (bufpos == 0 ? bp + buflen : p);
newl = skip = 0;
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 || all)
newl = skip = 0;
} else if (ch >= '0' && ch <= '9') {
pri *= 10;
pri += ch - '0';
}
continue;
}
if (newl && ch == '<') {
pri = 0;
skip = 1;
continue;
}
if (ch == '\0')
continue;
newl = ch == '\n';
(void)vis(buf, ch, 0, 0);
if (buf[1] == 0)
(void)putchar(buf[0]);
p = bp;
ep = &bp[buflen];
if (*p == '\0') {
/* Strip leading \0's */
while (p != ep && *p == '\0')
p++;
} else if (!all) {
/* Skip the first line, since it is probably incomplete. */
p = memchr(p, '\n', ep - p);
if (p == NULL)
p = ep;
else
(void)printf("%s", buf);
} while (++p != ep);
if (!newl)
(void)putchar('\n');
p++;
}
for (; p != ep; p = nextp) {
nextp = memchr(p, '\n', ep - p);
if (nextp == NULL)
nextp = ep;
else
nextp++;
/* Skip ^<[0-9]+> syslog sequences. */
if (*p == '<') {
pri = 0;
for (q = p + 1; q != ep && *q >= '0' && *q <= '9'; q++)
pri = pri * 10 + (*q - '0');
if (q != ep && *q == '>' && q != p + 1) {
if (LOG_FAC(pri) != LOG_KERN && !all)
continue;
p = q + 1;
}
}
for (; p != nextp; p++) {
(void)vis(buf, *p, 0, 0);
if (buf[1] == 0)
(void)putchar(buf[0]);
else
(void)printf("%s", buf);
}
if (nextp == ep && ep[-1] != '\n')
(void)putchar('\n');
}
exit(0);
}