source: branches/3.2/mindi-busybox/sysklogd/klogd.c @ 3232

Last change on this file since 3232 was 3232, checked in by bruno, 5 years ago
  • Update mindi-busybox to 1.21.1
File size: 6.8 KB
Line 
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
39static void klogd_open(void)
40{
41    /* "Open the log. Currently a NOP" */
42    klogctl(1, NULL, 0);
43}
44
45static 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
52static int klogd_read(char *bufp, int len)
53{
54    return klogctl(2, bufp, len);
55}
56# define READ_ERROR "klogctl(2) error"
57
58static 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
78enum { klogfd = 3 };
79
80static void klogd_open(void)
81{
82    int fd = xopen(_PATH_KLOG, O_RDONLY);
83    xmove_fd(fd, klogfd);
84}
85
86static 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
101static int klogd_read(char *bufp, int len)
102{
103    return read(klogfd, bufp, len);
104}
105# define READ_ERROR "read error"
106
107static 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
117enum {
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
136int klogd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
137int 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}
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