source: branches/2.2.9/mindi-busybox/sysklogd/klogd.c @ 2859

Last change on this file since 2859 was 2859, checked in by bruno, 8 years ago
  • Update to upstream busybox 1.18.5
File size: 6.5 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#include "libbb.h"
21#include <syslog.h>
22
23
24/* The Linux-specific klogctl(3) interface does not rely on the filesystem and
25 * allows us to change the console loglevel. Alternatively, we read the
26 * messages from _PATH_KLOG. */
27
28#if ENABLE_FEATURE_KLOGD_KLOGCTL
29
30# include <sys/klog.h>
31
32static void klogd_open(void)
33{
34    /* "Open the log. Currently a NOP" */
35    klogctl(1, NULL, 0);
36}
37
38static void klogd_setloglevel(int lvl)
39{
40    /* "printk() prints a message on the console only if it has a loglevel
41     * less than console_loglevel". Here we set console_loglevel = lvl. */
42    klogctl(8, NULL, lvl);
43}
44
45static int klogd_read(char *bufp, int len)
46{
47    return klogctl(2, bufp, len);
48}
49# define READ_ERROR "klogctl(2) error"
50
51static void klogd_close(void)
52{
53    /* FYI: cmd 7 is equivalent to setting console_loglevel to 7
54     * via klogctl(8, NULL, 7). */
55    klogctl(7, NULL, 0); /* "7 -- Enable printk's to console" */
56    klogctl(0, NULL, 0); /* "0 -- Close the log. Currently a NOP" */
57}
58
59#else
60
61# include <paths.h>
62# ifndef _PATH_KLOG
63#  ifdef __GNU__
64#   define _PATH_KLOG "/dev/klog"
65#  else
66#   error "your system's _PATH_KLOG is unknown"
67#  endif
68# endif
69# define PATH_PRINTK "/proc/sys/kernel/printk"
70
71enum { klogfd = 3 };
72
73static void klogd_open(void)
74{
75    int fd = xopen(_PATH_KLOG, O_RDONLY);
76    xmove_fd(fd, klogfd);
77}
78
79static void klogd_setloglevel(int lvl)
80{
81    FILE *fp = fopen_or_warn(PATH_PRINTK, "w");
82    if (fp) {
83        /* This changes only first value:
84         * "messages with a higher priority than this
85         * [that is, with numerically lower value]
86         * will be printed to the console".
87         * The other three values in this pseudo-file aren't changed.
88         */
89        fprintf(fp, "%u\n", lvl);
90        fclose(fp);
91    }
92}
93
94static int klogd_read(char *bufp, int len)
95{
96    return read(klogfd, bufp, len);
97}
98# define READ_ERROR "read error"
99
100static void klogd_close(void)
101{
102    klogd_setloglevel(7);
103    if (ENABLE_FEATURE_CLEAN_UP)
104        close(klogfd);
105}
106
107#endif
108
109#define log_buffer bb_common_bufsiz1
110enum {
111    KLOGD_LOGBUF_SIZE = sizeof(log_buffer),
112    OPT_LEVEL      = (1 << 0),
113    OPT_FOREGROUND = (1 << 1),
114};
115
116/* TODO: glibc openlog(LOG_KERN) reverts to LOG_USER instead,
117 * because that's how they interpret word "default"
118 * in the openlog() manpage:
119 *      LOG_USER (default)
120 *              generic user-level messages
121 * and the fact that LOG_KERN is a constant 0.
122 * glibc interprets it as "0 in openlog() call means 'use default'".
123 * I think it means "if openlog wasn't called before syslog() is called,
124 * use default".
125 * Convincing glibc maintainers otherwise is, as usual, nearly impossible.
126 * Should we open-code syslog() here to use correct facility?
127 */
128
129int klogd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
130int klogd_main(int argc UNUSED_PARAM, char **argv)
131{
132    int i = 0;
133    char *opt_c;
134    int opt;
135    int used;
136
137    opt = getopt32(argv, "c:n", &opt_c);
138    if (opt & OPT_LEVEL) {
139        /* Valid levels are between 1 and 8 */
140        i = xatou_range(opt_c, 1, 8);
141    }
142    if (!(opt & OPT_FOREGROUND)) {
143        bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);
144    }
145
146    logmode = LOGMODE_SYSLOG;
147
148    /* klogd_open() before openlog(), since it might use fixed fd 3,
149     * and openlog() also may use the same fd 3 if we swap them:
150     */
151    klogd_open();
152    openlog("kernel", 0, LOG_KERN);
153    /*
154     * glibc problem: for some reason, glibc changes LOG_KERN to LOG_USER
155     * above. The logic behind this is that standard
156     * http://pubs.opengroup.org/onlinepubs/9699919799/functions/syslog.html
157     * says the following about openlog and syslog:
158     * "LOG_USER
159     *  Messages generated by arbitrary processes.
160     *  This is the default facility identifier if none is specified."
161     *
162     * I believe glibc misinterpreted this text as "if openlog's
163     * third parameter is 0 (=LOG_KERN), treat it as LOG_USER".
164     * Whereas it was meant to say "if *syslog* is called with facility
165     * 0 in its 1st parameter without prior call to openlog, then perform
166     * implicit openlog(LOG_USER)".
167     *
168     * As a result of this, eh, feature, standard klogd was forced
169     * to open-code its own openlog and syslog implementation (!).
170     *
171     * Note that prohibiting openlog(LOG_KERN) on libc level does not
172     * add any security: any process can open a socket to "/dev/log"
173     * and write a string "<0>Voila, a LOG_KERN + LOG_EMERG message"
174     *
175     * Google code search tells me there is no widespread use of
176     * openlog("foo", 0, 0), thus fixing glibc won't break userspace.
177     *
178     * The bug against glibc was filed:
179     * bugzilla.redhat.com/show_bug.cgi?id=547000
180     */
181
182    if (i)
183        klogd_setloglevel(i);
184
185    signal(SIGHUP, SIG_IGN);
186    /* We want klogd_read to not be restarted, thus _norestart: */
187    bb_signals_recursive_norestart(BB_FATAL_SIGS, record_signo);
188
189    syslog(LOG_NOTICE, "klogd started: %s", bb_banner);
190
191    used = 0;
192    while (!bb_got_signal) {
193        int n;
194        int priority;
195        char *start;
196
197        /* "2 -- Read from the log." */
198        start = log_buffer + used;
199        n = klogd_read(start, KLOGD_LOGBUF_SIZE-1 - used);
200        if (n < 0) {
201            if (errno == EINTR)
202                continue;
203            bb_perror_msg(READ_ERROR);
204            break;
205        }
206        start[n] = '\0';
207
208        /* Process each newline-terminated line in the buffer */
209        start = log_buffer;
210        while (1) {
211            char *newline = strchrnul(start, '\n');
212
213            if (*newline == '\0') {
214                /* This line is incomplete */
215
216                /* move it to the front of the buffer */
217                overlapping_strcpy(log_buffer, start);
218                used = newline - start;
219                if (used < KLOGD_LOGBUF_SIZE-1) {
220                    /* buffer isn't full */
221                    break;
222                }
223                /* buffer is full, log it anyway */
224                used = 0;
225                newline = NULL;
226            } else {
227                *newline++ = '\0';
228            }
229
230            /* Extract the priority */
231            priority = LOG_INFO;
232            if (*start == '<') {
233                start++;
234                if (*start) {
235                    /* kernel never generates multi-digit prios */
236                    priority = (*start - '0');
237                    start++;
238                }
239                if (*start == '>')
240                    start++;
241            }
242            /* Log (only non-empty lines) */
243            if (*start)
244                syslog(priority, "%s", start);
245
246            if (!newline)
247                break;
248            start = newline;
249        }
250    }
251
252    klogd_close();
253    syslog(LOG_NOTICE, "klogd: exiting");
254    if (bb_got_signal)
255        kill_myself_with_sig(bb_got_signal);
256    return EXIT_FAILURE;
257}
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