*
* Copyright (C) 2001 by Gennady Feldman <gfeldman@gena01.com>.
* Changes: Made this a standalone busybox module which uses standalone
- * syslog() client interface.
+ * syslog() client interface.
*
* Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
*
*
* Maintainer: Gennady Feldman <gfeldman@gena01.com> as of Mar 12, 2001
*
- * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
+//config:config KLOGD
+//config: bool "klogd (5.7 kb)"
+//config: default y
+//config: help
+//config: klogd is a utility which intercepts and logs all
+//config: messages from the Linux kernel and sends the messages
+//config: out to the 'syslogd' utility so they can be logged. If
+//config: you wish to record the messages produced by the kernel,
+//config: you should enable this option.
+//config:
+//config:comment "klogd should not be used together with syslog to kernel printk buffer"
+//config: depends on KLOGD && FEATURE_KMSG_SYSLOG
+//config:
+//config:config FEATURE_KLOGD_KLOGCTL
+//config: bool "Use the klogctl() interface"
+//config: default y
+//config: depends on KLOGD
+//config: select PLATFORM_LINUX
+//config: help
+//config: The klogd applet supports two interfaces for reading
+//config: kernel messages. Linux provides the klogctl() interface
+//config: which allows reading messages from the kernel ring buffer
+//config: independently from the file system.
+//config:
+//config: If you answer 'N' here, klogd will use the more portable
+//config: approach of reading them from /proc or a device node.
+//config: However, this method requires the file to be available.
+//config:
+//config: If in doubt, say 'Y'.
-#include <stdio.h>
-#include <stdlib.h>
-#include <signal.h> /* for our signal() handlers */
-#include <string.h> /* strncpy() */
-#include <errno.h> /* errno and friends */
-#include <unistd.h>
-#include <ctype.h>
-#include <sys/syslog.h>
-#include <sys/klog.h>
+//applet:IF_KLOGD(APPLET(klogd, BB_DIR_SBIN, BB_SUID_DROP))
-#include "busybox.h"
+//kbuild:lib-$(CONFIG_KLOGD) += klogd.o
-static void klogd_signal(int sig)
+//usage:#define klogd_trivial_usage
+//usage: "[-c N] [-n]"
+//usage:#define klogd_full_usage "\n\n"
+//usage: "Log kernel messages to syslog\n"
+//usage: "\n -c N Print to console messages more urgent than prio N (1-8)"
+//usage: "\n -n Run in foreground"
+
+#include "libbb.h"
+#include "common_bufsiz.h"
+#include <syslog.h>
+
+
+/* The Linux-specific klogctl(3) interface does not rely on the filesystem and
+ * allows us to change the console loglevel. Alternatively, we read the
+ * messages from _PATH_KLOG. */
+
+#if ENABLE_FEATURE_KLOGD_KLOGCTL
+
+# include <sys/klog.h>
+
+static void klogd_open(void)
{
- klogctl(7, NULL, 0);
- klogctl(0, 0, 0);
- /* logMessage(0, "Kernel log daemon exiting."); */
- syslog(LOG_NOTICE, "Kernel log daemon exiting.");
- exit(EXIT_SUCCESS);
+ /* "Open the log. Currently a NOP" */
+ klogctl(1, NULL, 0);
}
-static void doKlogd(const int console_log_level) ATTRIBUTE_NORETURN;
-static void doKlogd(const int console_log_level)
+static void klogd_setloglevel(int lvl)
{
- int priority = LOG_INFO;
- char log_buffer[4096];
- int i, n, lastc;
- char *start;
+ /* "printk() prints a message on the console only if it has a loglevel
+ * less than console_loglevel". Here we set console_loglevel = lvl. */
+ klogctl(8, NULL, lvl);
+}
- openlog("kernel", 0, LOG_KERN);
+static int klogd_read(char *bufp, int len)
+{
+ /* "2 -- Read from the log." */
+ return klogctl(2, bufp, len);
+}
+# define READ_ERROR "klogctl(2) error"
- /* Set up sig handlers */
- signal(SIGINT, klogd_signal);
- signal(SIGKILL, klogd_signal);
- signal(SIGTERM, klogd_signal);
- signal(SIGHUP, SIG_IGN);
+static void klogd_close(void)
+{
+ /* FYI: cmd 7 is equivalent to setting console_loglevel to 7
+ * via klogctl(8, NULL, 7). */
+ klogctl(7, NULL, 0); /* "7 -- Enable printk's to console" */
+ klogctl(0, NULL, 0); /* "0 -- Close the log. Currently a NOP" */
+}
- /* "Open the log. Currently a NOP." */
- klogctl(1, NULL, 0);
+#else
- /* Set level of kernel console messaging.. */
- if (console_log_level != -1)
- klogctl(8, NULL, console_log_level);
+# ifndef _PATH_KLOG
+# ifdef __GNU__
+# define _PATH_KLOG "/dev/klog"
+# else
+# error "your system's _PATH_KLOG is unknown"
+# endif
+# endif
+# define PATH_PRINTK "/proc/sys/kernel/printk"
- syslog(LOG_NOTICE, "klogd started: %s", BB_BANNER);
+enum { klogfd = 3 };
- while (1) {
- /* Use kernel syscalls */
- memset(log_buffer, '\0', sizeof(log_buffer));
- n = klogctl(2, log_buffer, sizeof(log_buffer));
- if (n < 0) {
- if (errno == EINTR)
- continue;
- syslog(LOG_ERR, "klogd: Error return from sys_sycall: %d - %m.\n", errno);
- exit(EXIT_FAILURE);
- }
+static void klogd_open(void)
+{
+ int fd = xopen(_PATH_KLOG, O_RDONLY);
+ xmove_fd(fd, klogfd);
+}
- /* klogctl buffer parsing modelled after code in dmesg.c */
- start = &log_buffer[0];
- lastc = '\0';
- for (i = 0; i < n; i++) {
- if (lastc == '\0' && log_buffer[i] == '<') {
- priority = 0;
- i++;
- while (isdigit(log_buffer[i])) {
- priority = priority * 10 + (log_buffer[i] - '0');
- i++;
- }
- if (log_buffer[i] == '>')
- i++;
- start = &log_buffer[i];
- }
- if (log_buffer[i] == '\n') {
- log_buffer[i] = '\0'; /* zero terminate this message */
- syslog(priority, "%s", start);
- start = &log_buffer[i + 1];
- priority = LOG_INFO;
- }
- lastc = log_buffer[i];
- }
+static void klogd_setloglevel(int lvl)
+{
+ FILE *fp = fopen_or_warn(PATH_PRINTK, "w");
+ if (fp) {
+ /* This changes only first value:
+ * "messages with a higher priority than this
+ * [that is, with numerically lower value]
+ * will be printed to the console".
+ * The other three values in this pseudo-file aren't changed.
+ */
+ fprintf(fp, "%u\n", lvl);
+ fclose(fp);
}
}
-#define OPT_LEVEL 1
-#define OPT_FOREGROUND 2
+static int klogd_read(char *bufp, int len)
+{
+ return read(klogfd, bufp, len);
+}
+# define READ_ERROR "read error"
-extern int klogd_main(int argc, char **argv)
+static void klogd_close(void)
{
- unsigned long opt;
- char *c_arg;
- int console_log_level = -1;
+ klogd_setloglevel(7);
+ if (ENABLE_FEATURE_CLEAN_UP)
+ close(klogfd);
+}
+
+#endif
- /* do normal option parsing */
- opt = bb_getopt_ulflags (argc, argv, "c:n", &c_arg);
+#define log_buffer bb_common_bufsiz1
+enum {
+ KLOGD_LOGBUF_SIZE = COMMON_BUFSIZE,
+ OPT_LEVEL = (1 << 0),
+ OPT_FOREGROUND = (1 << 1),
+};
+
+/* TODO: glibc openlog(LOG_KERN) reverts to LOG_USER instead,
+ * because that's how they interpret word "default"
+ * in the openlog() manpage:
+ * LOG_USER (default)
+ * generic user-level messages
+ * and the fact that LOG_KERN is a constant 0.
+ * glibc interprets it as "0 in openlog() call means 'use default'".
+ * I think it means "if openlog wasn't called before syslog() is called,
+ * use default".
+ * Convincing glibc maintainers otherwise is, as usual, nearly impossible.
+ * Should we open-code syslog() here to use correct facility?
+ */
+int klogd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int klogd_main(int argc UNUSED_PARAM, char **argv)
+{
+ int i = 0;
+ char *opt_c;
+ int opt;
+ int used;
+
+ setup_common_bufsiz();
+
+ opt = getopt32(argv, "c:n", &opt_c);
if (opt & OPT_LEVEL) {
/* Valid levels are between 1 and 8 */
- console_log_level = bb_xgetlarg(c_arg, 10, 1, 8);
+ i = xatou_range(opt_c, 1, 8);
}
-
if (!(opt & OPT_FOREGROUND)) {
-#if defined(__uClinux__)
- vfork_daemon_rexec(0, 1, argc, argv, "-n");
-#else /* __uClinux__ */
- if (daemon(0, 1) < 0)
- bb_perror_msg_and_die("daemon");
-#endif /* __uClinux__ */
+ bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);
}
- doKlogd(console_log_level);
- return EXIT_SUCCESS;
-}
+ logmode = LOGMODE_SYSLOG;
-/*
-Local Variables
-c-file-style: "linux"
-c-basic-offset: 4
-tab-width: 4
-End:
-*/
+ /* klogd_open() before openlog(), since it might use fixed fd 3,
+ * and openlog() also may use the same fd 3 if we swap them:
+ */
+ klogd_open();
+ openlog("kernel", 0, LOG_KERN);
+ /*
+ * glibc problem: for some reason, glibc changes LOG_KERN to LOG_USER
+ * above. The logic behind this is that standard
+ * http://pubs.opengroup.org/onlinepubs/9699919799/functions/syslog.html
+ * says the following about openlog and syslog:
+ * "LOG_USER
+ * Messages generated by arbitrary processes.
+ * This is the default facility identifier if none is specified."
+ *
+ * I believe glibc misinterpreted this text as "if openlog's
+ * third parameter is 0 (=LOG_KERN), treat it as LOG_USER".
+ * Whereas it was meant to say "if *syslog* is called with facility
+ * 0 in its 1st parameter without prior call to openlog, then perform
+ * implicit openlog(LOG_USER)".
+ *
+ * As a result of this, eh, feature, standard klogd was forced
+ * to open-code its own openlog and syslog implementation (!).
+ *
+ * Note that prohibiting openlog(LOG_KERN) on libc level does not
+ * add any security: any process can open a socket to "/dev/log"
+ * and write a string "<0>Voila, a LOG_KERN + LOG_EMERG message"
+ *
+ * Google code search tells me there is no widespread use of
+ * openlog("foo", 0, 0), thus fixing glibc won't break userspace.
+ *
+ * The bug against glibc was filed:
+ * bugzilla.redhat.com/show_bug.cgi?id=547000
+ */
+
+ if (i)
+ klogd_setloglevel(i);
+
+ signal(SIGHUP, SIG_IGN);
+ /* We want klogd_read to not be restarted, thus _norestart: */
+ bb_signals_recursive_norestart(BB_FATAL_SIGS, record_signo);
+
+ syslog(LOG_NOTICE, "klogd started: %s", bb_banner);
+
+ write_pidfile_std_path_and_ext("klogd");
+
+ used = 0;
+ while (!bb_got_signal) {
+ int n;
+ int priority;
+ char *start;
+
+ start = log_buffer + used;
+ n = klogd_read(start, KLOGD_LOGBUF_SIZE-1 - used);
+ if (n < 0) {
+ if (errno == EINTR)
+ continue;
+ bb_perror_msg(READ_ERROR);
+ break;
+ }
+ start[n] = '\0';
+
+ /* Process each newline-terminated line in the buffer */
+ start = log_buffer;
+ while (1) {
+ char *newline = strchrnul(start, '\n');
+
+ if (*newline == '\0') {
+ /* This line is incomplete */
+
+ /* move it to the front of the buffer */
+ overlapping_strcpy(log_buffer, start);
+ used = newline - start;
+ if (used < KLOGD_LOGBUF_SIZE-1) {
+ /* buffer isn't full */
+ break;
+ }
+ /* buffer is full, log it anyway */
+ used = 0;
+ newline = NULL;
+ } else {
+ *newline++ = '\0';
+ }
+
+ /* Extract the priority */
+ priority = LOG_INFO;
+ if (*start == '<') {
+ start++;
+ if (*start) {
+ char *end;
+ priority = strtoul(start, &end, 10);
+ if (*end == '>')
+ end++;
+ start = end;
+ }
+ }
+ /* Log (only non-empty lines) */
+ if (*start)
+ syslog(priority, "%s", start);
+
+ if (!newline)
+ break;
+ start = newline;
+ }
+ }
+
+ klogd_close();
+ syslog(LOG_NOTICE, "klogd: exiting");
+ remove_pidfile_std_path_and_ext("klogd");
+ if (bb_got_signal)
+ kill_myself_with_sig(bb_got_signal);
+ return EXIT_FAILURE;
+}
projects / oweals / busybox.git / blobdiff