diff options
| -rw-r--r-- | sysklogd/Config.src | 17 | ||||
| -rw-r--r-- | sysklogd/klogd.c | 128 |
2 files changed, 126 insertions, 19 deletions
diff --git a/sysklogd/Config.src b/sysklogd/Config.src index 41c0d28..1e59872 100644 --- a/sysklogd/Config.src +++ b/sysklogd/Config.src @@ -109,7 +109,6 @@ config FEATURE_LOGREAD_REDUCED_LOCKING config KLOGD bool "klogd" default y - depends on PLATFORM_LINUX help klogd is a utility which intercepts and logs all messages from the Linux kernel and sends the messages @@ -117,6 +116,22 @@ config KLOGD you wish to record the messages produced by the kernel, you should enable this option. +config FEATURE_KLOGD_KLOGCTL + bool "Use the klogctl() interface" + default y + depends on KLOGD && PLATFORM_LINUX + help + The klogd applet supports two interfaces for reading + kernel messages. Linux provides the klogctl() interface + which allows reading messages from the kernel ring buffer + independently from the file system. + + If you answer 'N' here, klogd will use the more portable + approach of reading them from /proc or a device node. + However, this method requires the file to be available. + + If in doubt, say 'Y'. + config LOGGER bool "logger" default y diff --git a/sysklogd/klogd.c b/sysklogd/klogd.c index c54e80a..3468656 100644 --- a/sysklogd/klogd.c +++ b/sysklogd/klogd.c @@ -4,7 +4,7 @@ * * 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> * @@ -19,18 +19,93 @@ #include "libbb.h" #include <syslog.h> -#include <sys/klog.h> -static void klogd_signal(int sig) + +/* 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) +{ + /* "Open the log. Currently a NOP" */ + klogctl(1, NULL, 0); +} + +static void klogd_setloglevel(int lvl) +{ + /* "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); +} + +static int klogd_read(char *bufp, int len) +{ + return klogctl(2, bufp, len); +} +# define READ_ERROR "klogctl(2) error" + +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" */ - syslog(LOG_NOTICE, "klogd: exiting"); - kill_myself_with_sig(sig); } +#else + +# include <paths.h> +# 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" + +enum { klogfd = 3 }; + +static void klogd_open(void) +{ + int fd = xopen(_PATH_KLOG, O_RDONLY); + xmove_fd(fd, klogfd); +} + +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); + } +} + +static int klogd_read(char *bufp, int len) +{ + return read(klogfd, bufp, len); +} +# define READ_ERROR "read error" + +static void klogd_close(void) +{ + klogd_setloglevel(7); + if (ENABLE_FEATURE_CLEAN_UP) + close(klogfd); +} + +#endif + #define log_buffer bb_common_bufsiz1 enum { KLOGD_LOGBUF_SIZE = sizeof(log_buffer), @@ -38,6 +113,19 @@ enum { 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) { @@ -55,34 +143,34 @@ int klogd_main(int argc UNUSED_PARAM, char **argv) bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv); } - openlog("kernel", 0, LOG_KERN); - - bb_signals(BB_FATAL_SIGS, klogd_signal); - signal(SIGHUP, SIG_IGN); + logmode = LOGMODE_SYSLOG; - /* "Open the log. Currently a NOP" */ - klogctl(1, NULL, 0); + /* 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); - /* "printk() prints a message on the console only if it has a loglevel - * less than console_loglevel". Here we set console_loglevel = i. */ if (i) - klogctl(8, NULL, i); + klogd_setloglevel(i); + + bb_signals(BB_FATAL_SIGS, record_signo); + signal(SIGHUP, SIG_IGN); syslog(LOG_NOTICE, "klogd started: %s", bb_banner); - while (1) { + while (!bb_got_signal) { int n; int priority; char *start; /* "2 -- Read from the log." */ start = log_buffer + used; - n = klogctl(2, start, KLOGD_LOGBUF_SIZE-1 - used); + n = klogd_read(start, KLOGD_LOGBUF_SIZE-1 - used); if (n < 0) { if (errno == EINTR) continue; - syslog(LOG_ERR, "klogd: error %d in klogctl(2): %m", - errno); + bb_perror_msg(READ_ERROR); break; } start[n] = '\0'; @@ -131,5 +219,9 @@ int klogd_main(int argc UNUSED_PARAM, char **argv) } } + klogd_close(); + syslog(LOG_NOTICE, "klogd: exiting"); + if (bb_got_signal) + kill_myself_with_sig(bb_got_signal); return EXIT_FAILURE; } |