1 /* vi: set sw=4 ts=4: */
3 * Mini klogd implementation for busybox
5 * Copyright (C) 2001 by Gennady Feldman <gfeldman@gena01.com>.
6 * Changes: Made this a standalone busybox module which uses standalone
7 * syslog() client interface.
9 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
11 * Copyright (C) 2000 by Karl M. Hegbloom <karlheg@debian.org>
13 * "circular buffer" Copyright (C) 2000 by Gennady Feldman <gfeldman@gena01.com>
15 * Maintainer: Gennady Feldman <gfeldman@gena01.com> as of Mar 12, 2001
17 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
20 //usage:#define klogd_trivial_usage
21 //usage: "[-c N] [-n]"
22 //usage:#define klogd_full_usage "\n\n"
23 //usage: "Kernel logger\n"
24 //usage: "\n -c N Print to console messages more urgent than prio N (1-8)"
25 //usage: "\n -n Run in foreground"
31 /* The Linux-specific klogctl(3) interface does not rely on the filesystem and
32 * allows us to change the console loglevel. Alternatively, we read the
33 * messages from _PATH_KLOG. */
35 #if ENABLE_FEATURE_KLOGD_KLOGCTL
37 # include <sys/klog.h>
39 static void klogd_open(void)
41 /* "Open the log. Currently a NOP" */
45 static void klogd_setloglevel(int lvl)
47 /* "printk() prints a message on the console only if it has a loglevel
48 * less than console_loglevel". Here we set console_loglevel = lvl. */
49 klogctl(8, NULL, lvl);
52 static int klogd_read(char *bufp, int len)
54 return klogctl(2, bufp, len);
56 # define READ_ERROR "klogctl(2) error"
58 static void klogd_close(void)
60 /* FYI: cmd 7 is equivalent to setting console_loglevel to 7
61 * via klogctl(8, NULL, 7). */
62 klogctl(7, NULL, 0); /* "7 -- Enable printk's to console" */
63 klogctl(0, NULL, 0); /* "0 -- Close the log. Currently a NOP" */
71 # define _PATH_KLOG "/dev/klog"
73 # error "your system's _PATH_KLOG is unknown"
76 # define PATH_PRINTK "/proc/sys/kernel/printk"
80 static void klogd_open(void)
82 int fd = xopen(_PATH_KLOG, O_RDONLY);
86 static void klogd_setloglevel(int lvl)
88 FILE *fp = fopen_or_warn(PATH_PRINTK, "w");
90 /* This changes only first value:
91 * "messages with a higher priority than this
92 * [that is, with numerically lower value]
93 * will be printed to the console".
94 * The other three values in this pseudo-file aren't changed.
96 fprintf(fp, "%u\n", lvl);
101 static int klogd_read(char *bufp, int len)
103 return read(klogfd, bufp, len);
105 # define READ_ERROR "read error"
107 static void klogd_close(void)
109 klogd_setloglevel(7);
110 if (ENABLE_FEATURE_CLEAN_UP)
116 #define log_buffer bb_common_bufsiz1
118 KLOGD_LOGBUF_SIZE = sizeof(log_buffer),
119 OPT_LEVEL = (1 << 0),
120 OPT_FOREGROUND = (1 << 1),
123 /* TODO: glibc openlog(LOG_KERN) reverts to LOG_USER instead,
124 * because that's how they interpret word "default"
125 * in the openlog() manpage:
127 * generic user-level messages
128 * and the fact that LOG_KERN is a constant 0.
129 * glibc interprets it as "0 in openlog() call means 'use default'".
130 * I think it means "if openlog wasn't called before syslog() is called,
132 * Convincing glibc maintainers otherwise is, as usual, nearly impossible.
133 * Should we open-code syslog() here to use correct facility?
136 int klogd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
137 int klogd_main(int argc UNUSED_PARAM, char **argv)
144 opt = getopt32(argv, "c:n", &opt_c);
145 if (opt & OPT_LEVEL) {
146 /* Valid levels are between 1 and 8 */
147 i = xatou_range(opt_c, 1, 8);
149 if (!(opt & OPT_FOREGROUND)) {
150 bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);
153 logmode = LOGMODE_SYSLOG;
155 /* klogd_open() before openlog(), since it might use fixed fd 3,
156 * and openlog() also may use the same fd 3 if we swap them:
159 openlog("kernel", 0, LOG_KERN);
161 * glibc problem: for some reason, glibc changes LOG_KERN to LOG_USER
162 * above. The logic behind this is that standard
163 * http://pubs.opengroup.org/onlinepubs/9699919799/functions/syslog.html
164 * says the following about openlog and syslog:
166 * Messages generated by arbitrary processes.
167 * This is the default facility identifier if none is specified."
169 * I believe glibc misinterpreted this text as "if openlog's
170 * third parameter is 0 (=LOG_KERN), treat it as LOG_USER".
171 * Whereas it was meant to say "if *syslog* is called with facility
172 * 0 in its 1st parameter without prior call to openlog, then perform
173 * implicit openlog(LOG_USER)".
175 * As a result of this, eh, feature, standard klogd was forced
176 * to open-code its own openlog and syslog implementation (!).
178 * Note that prohibiting openlog(LOG_KERN) on libc level does not
179 * add any security: any process can open a socket to "/dev/log"
180 * and write a string "<0>Voila, a LOG_KERN + LOG_EMERG message"
182 * Google code search tells me there is no widespread use of
183 * openlog("foo", 0, 0), thus fixing glibc won't break userspace.
185 * The bug against glibc was filed:
186 * bugzilla.redhat.com/show_bug.cgi?id=547000
190 klogd_setloglevel(i);
192 signal(SIGHUP, SIG_IGN);
193 /* We want klogd_read to not be restarted, thus _norestart: */
194 bb_signals_recursive_norestart(BB_FATAL_SIGS, record_signo);
196 syslog(LOG_NOTICE, "klogd started: %s", bb_banner);
198 write_pidfile(CONFIG_PID_FILE_PATH "/klogd.pid");
201 while (!bb_got_signal) {
206 /* "2 -- Read from the log." */
207 start = log_buffer + used;
208 n = klogd_read(start, KLOGD_LOGBUF_SIZE-1 - used);
212 bb_perror_msg(READ_ERROR);
217 /* Process each newline-terminated line in the buffer */
220 char *newline = strchrnul(start, '\n');
222 if (*newline == '\0') {
223 /* This line is incomplete */
225 /* move it to the front of the buffer */
226 overlapping_strcpy(log_buffer, start);
227 used = newline - start;
228 if (used < KLOGD_LOGBUF_SIZE-1) {
229 /* buffer isn't full */
232 /* buffer is full, log it anyway */
239 /* Extract the priority */
244 priority = strtoul(start, &start, 10);
248 /* Log (only non-empty lines) */
250 syslog(priority, "%s", start);
259 syslog(LOG_NOTICE, "klogd: exiting");
260 remove_pidfile(CONFIG_PID_FILE_PATH "/klogd.pid");
262 kill_myself_with_sig(bb_got_signal);