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Code Issues Releases Activity

Use the kern.msgbuf sysctl to get the message buffer on a running

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kernel, and remove setgid kmem, which is not needed any more.
This commit is contained in:
Thomas Moestl 2001-07-03 19:49:31 +00:00
parent 948d3d9484
commit 676adc045c
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=79154
2 changed files with 44 additions and 32 deletions
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2
sbin/dmesg/Makefile
View File

@ -3,8 +3,6 @@
PROG= dmesg
MAN= dmesg.8
BINGRP= kmem
BINMODE=2555
LDADD= -lkvm
DPADD= ${LIBKVM}

74
sbin/dmesg/dmesg.c
View File

@ -45,7 +45,9 @@ static const char rcsid[] =
"$FreeBSD$";
#endif /* not lint */
#include <sys/types.h>
#include <sys/msgbuf.h>
#include <sys/sysctl.h>
#include <err.h>
#include <fcntl.h>
@ -81,6 +83,8 @@ main(argc, argv)
char buf[5];
int all = 0;
int pri;
size_t buflen;
int bufpos;
(void) setlocale(LC_CTYPE, "");
memf = nlistf = NULL;
@ -102,33 +106,43 @@ main(argc, argv)
argc -= optind;
argv += optind;
/*
* Discard setgid privileges if not the running kernel so that bad
* guys can't print interesting stuff from kernel memory.
*/
if (memf != NULL || nlistf != NULL)
setgid(getgid());
/* Read in kernel message buffer, do sanity checks. */
if ((kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg")) == 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");
if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur))
errx(1, "kvm_read: %s", kvm_geterr(kd));
if (cur.msg_magic != MSG_MAGIC)
errx(1, "kernel message buffer has different magic number");
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)
errx(1, "kvm_read: %s", kvm_geterr(kd));
if (cur.msg_bufx >= cur.msg_size)
cur.msg_bufx = 0;
kvm_close(kd);
if (memf == NULL && nlistf == NULL) {
/* Running kernel. Use sysctl. */
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");
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");
if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur))
errx(1, "kvm_read: %s", kvm_geterr(kd));
if (cur.msg_magic != MSG_MAGIC)
errx(1, "kernel message buffer has different magic "
"number");
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)
errx(1, "kvm_read: %s", kvm_geterr(kd));
kvm_close(kd);
buflen = cur.msg_size;
bufpos = cur.msg_bufx;
if (bufpos >= buflen)
bufpos = 0;
}
/*
* The message buffer is circular. If the buffer has wrapped, the
@ -137,11 +151,11 @@ main(argc, argv)
* buffer starting at the write pointer and ignore nulls so that
* we effectively start at the oldest data.
*/
p = bp + cur.msg_bufx;
ep = (cur.msg_bufx == 0 ? bp + cur.msg_size : p);
p = bp + bufpos;
ep = (bufpos == 0 ? bp + buflen : p);
newl = skip = 0;
do {
if (p == bp + cur.msg_size)
if (p == bp + buflen)
p = bp;
ch = *p;
/* Skip "\n<.*>" syslog sequences. */