blob: 432ded1530be3054bf1f3ee9130d025a803833ee
1 | /* vi: set sw=4 ts=4: */ |
2 | /* |
3 | * Mini klogd implementation for busybox |
4 | * |
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. |
8 | * |
9 | * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org> |
10 | * |
11 | * Copyright (C) 2000 by Karl M. Hegbloom <karlheg@debian.org> |
12 | * |
13 | * "circular buffer" Copyright (C) 2000 by Gennady Feldman <gfeldman@gena01.com> |
14 | * |
15 | * Maintainer: Gennady Feldman <gfeldman@gena01.com> as of Mar 12, 2001 |
16 | * |
17 | * Licensed under GPLv2 or later, see file LICENSE in this source tree. |
18 | */ |
19 | |
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" |
26 | |
27 | #include "libbb.h" |
28 | #include <syslog.h> |
29 | |
30 | |
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. */ |
34 | |
35 | #if ENABLE_FEATURE_KLOGD_KLOGCTL |
36 | |
37 | # include <sys/klog.h> |
38 | |
39 | static void klogd_open(void) |
40 | { |
41 | /* "Open the log. Currently a NOP" */ |
42 | klogctl(1, NULL, 0); |
43 | } |
44 | |
45 | static void klogd_setloglevel(int lvl) |
46 | { |
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); |
50 | } |
51 | |
52 | static int klogd_read(char *bufp, int len) |
53 | { |
54 | return klogctl(2, bufp, len); |
55 | } |
56 | # define READ_ERROR "klogctl(2) error" |
57 | |
58 | static void klogd_close(void) |
59 | { |
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" */ |
64 | } |
65 | |
66 | #else |
67 | |
68 | # include <paths.h> |
69 | # ifndef _PATH_KLOG |
70 | # ifdef __GNU__ |
71 | # define _PATH_KLOG "/dev/klog" |
72 | # else |
73 | # error "your system's _PATH_KLOG is unknown" |
74 | # endif |
75 | # endif |
76 | # define PATH_PRINTK "/proc/sys/kernel/printk" |
77 | |
78 | enum { klogfd = 3 }; |
79 | |
80 | static void klogd_open(void) |
81 | { |
82 | int fd = xopen(_PATH_KLOG, O_RDONLY); |
83 | xmove_fd(fd, klogfd); |
84 | } |
85 | |
86 | static void klogd_setloglevel(int lvl) |
87 | { |
88 | FILE *fp = fopen_or_warn(PATH_PRINTK, "w"); |
89 | if (fp) { |
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. |
95 | */ |
96 | fprintf(fp, "%u\n", lvl); |
97 | fclose(fp); |
98 | } |
99 | } |
100 | |
101 | static int klogd_read(char *bufp, int len) |
102 | { |
103 | return read(klogfd, bufp, len); |
104 | } |
105 | # define READ_ERROR "read error" |
106 | |
107 | static void klogd_close(void) |
108 | { |
109 | klogd_setloglevel(7); |
110 | if (ENABLE_FEATURE_CLEAN_UP) |
111 | close(klogfd); |
112 | } |
113 | |
114 | #endif |
115 | |
116 | #define log_buffer bb_common_bufsiz1 |
117 | enum { |
118 | KLOGD_LOGBUF_SIZE = sizeof(log_buffer), |
119 | OPT_LEVEL = (1 << 0), |
120 | OPT_FOREGROUND = (1 << 1), |
121 | }; |
122 | |
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: |
126 | * LOG_USER (default) |
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, |
131 | * use default". |
132 | * Convincing glibc maintainers otherwise is, as usual, nearly impossible. |
133 | * Should we open-code syslog() here to use correct facility? |
134 | */ |
135 | |
136 | int klogd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
137 | int klogd_main(int argc UNUSED_PARAM, char **argv) |
138 | { |
139 | int i = 0; |
140 | char *opt_c; |
141 | int opt; |
142 | int used; |
143 | |
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); |
148 | } |
149 | if (!(opt & OPT_FOREGROUND)) { |
150 | bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv); |
151 | } |
152 | |
153 | logmode = LOGMODE_SYSLOG; |
154 | |
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: |
157 | */ |
158 | klogd_open(); |
159 | openlog("kernel", 0, LOG_KERN); |
160 | /* |
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: |
165 | * "LOG_USER |
166 | * Messages generated by arbitrary processes. |
167 | * This is the default facility identifier if none is specified." |
168 | * |
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)". |
174 | * |
175 | * As a result of this, eh, feature, standard klogd was forced |
176 | * to open-code its own openlog and syslog implementation (!). |
177 | * |
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" |
181 | * |
182 | * Google code search tells me there is no widespread use of |
183 | * openlog("foo", 0, 0), thus fixing glibc won't break userspace. |
184 | * |
185 | * The bug against glibc was filed: |
186 | * bugzilla.redhat.com/show_bug.cgi?id=547000 |
187 | */ |
188 | |
189 | if (i) |
190 | klogd_setloglevel(i); |
191 | |
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); |
195 | |
196 | syslog(LOG_NOTICE, "klogd started: %s", bb_banner); |
197 | |
198 | write_pidfile(CONFIG_PID_FILE_PATH "/klogd.pid"); |
199 | |
200 | used = 0; |
201 | while (!bb_got_signal) { |
202 | int n; |
203 | int priority; |
204 | char *start; |
205 | |
206 | /* "2 -- Read from the log." */ |
207 | start = log_buffer + used; |
208 | n = klogd_read(start, KLOGD_LOGBUF_SIZE-1 - used); |
209 | if (n < 0) { |
210 | if (errno == EINTR) |
211 | continue; |
212 | bb_perror_msg(READ_ERROR); |
213 | break; |
214 | } |
215 | start[n] = '\0'; |
216 | |
217 | /* Process each newline-terminated line in the buffer */ |
218 | start = log_buffer; |
219 | while (1) { |
220 | char *newline = strchrnul(start, '\n'); |
221 | |
222 | if (*newline == '\0') { |
223 | /* This line is incomplete */ |
224 | |
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 */ |
230 | break; |
231 | } |
232 | /* buffer is full, log it anyway */ |
233 | used = 0; |
234 | newline = NULL; |
235 | } else { |
236 | *newline++ = '\0'; |
237 | } |
238 | |
239 | /* Extract the priority */ |
240 | priority = LOG_INFO; |
241 | if (*start == '<') { |
242 | start++; |
243 | if (*start) |
244 | priority = strtoul(start, &start, 10); |
245 | if (*start == '>') |
246 | start++; |
247 | } |
248 | /* Log (only non-empty lines) */ |
249 | if (*start) |
250 | syslog(priority, "%s", start); |
251 | |
252 | if (!newline) |
253 | break; |
254 | start = newline; |
255 | } |
256 | } |
257 | |
258 | klogd_close(); |
259 | syslog(LOG_NOTICE, "klogd: exiting"); |
260 | remove_pidfile(CONFIG_PID_FILE_PATH "/klogd.pid"); |
261 | if (bb_got_signal) |
262 | kill_myself_with_sig(bb_got_signal); |
263 | return EXIT_FAILURE; |
264 | } |
265 |