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authorPeter Korsgaard <jacmet@sunsite.dk>2013-01-05 23:07:19 (GMT)
committer Mike Frysinger <vapier@gentoo.org>2013-01-06 18:30:50 (GMT)
commitcd776cf96735760311560495f3f0078ae72e98a0 (patch)
tree21aa8361ce965d00921923430f4773fcc060e6cd
parentd189b598b449f3a258354133180e7b770c04526c (diff)
downloadbusybox-cd776cf96735760311560495f3f0078ae72e98a0.tar.gz
busybox-cd776cf96735760311560495f3f0078ae72e98a0.tar.bz2
syslogd: add option to log to Linux kernel printk buffer
Why invent our own shared memory circular buffer when the kernel has a perfectly fine one already? This can be used as a smaller/simpler alternative to the syslogd IPC support (as IPC shmem/klogd/logread aren't needed), while also allowing centralised logging of everything (kernel messages, userspace bootup and syslog) when used together with ttyprintk. Notice that kernel 3.5+ is needed to store syslog facility in printk buffer, otherwise only the priority is stored. bloat-o-meter compared to IPC+klogd+logread: function old new delta get_linux_version_code - 84 +84 lbb_prepare 25 90 +65 applet_nameofs 6 - -6 static.stdout@@GLIBC_2 8 - -8 applet_names 23 9 -14 bb_msg_standard_output 16 - -16 init_sem 18 - -18 xatoull_range 19 - -19 overlapping_strcpy 21 - -21 init_data 56 32 -24 applet_main 24 - -24 main 124 99 -25 full_write2_str 26 - -26 error_exit 26 - -26 bb_basename 30 - -30 sem_up 32 - -32 interrupted 35 - -35 fflush_stdout_and_exit 38 - -38 bb_banner 46 - -46 find_applet_by_name 59 - -59 bb_signals_recursive_norestart 90 - -90 run_applet_no_and_exit 104 - -104 timestamp_and_log 651 523 -128 syslogd_main 798 581 -217 xstrtoull_range_sfx 267 - -267 run_applet_and_exit 432 - -432 klogd_main 490 - -490 logread_main 508 - -508 .rodata 1870 937 -933 bb_common_bufsiz1 8193 - -8193 ------------------------------------------------------------------------------ (add/remove: 2/26 grow/shrink: 1/6 up/down: 149/-11829) Total: -11680 bytes Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
-rw-r--r--sysklogd/Config.src16
-rw-r--r--sysklogd/syslogd.c61
2 files changed, 76 insertions, 1 deletions
diff --git a/sysklogd/Config.src b/sysklogd/Config.src
index b7a494e..fcf9930 100644
--- a/sysklogd/Config.src
+++ b/sysklogd/Config.src
@@ -113,6 +113,19 @@ config FEATURE_LOGREAD_REDUCED_LOCKING
from circular buffer, minimizing semaphore
contention at some minor memory expense.
+config FEATURE_KMSG_SYSLOG
+ bool "Linux kernel printk buffer support"
+ default y
+ depends on SYSLOGD
+ select PLATFORM_LINUX
+ help
+ When you enable this feature, the syslogd utility will
+ write system log message to the Linux kernel's printk buffer.
+ This can be used as a smaller alternative to the syslogd IPC
+ support, as klogd and logread aren't needed.
+
+ NOTICE: Syslog facilities in log entries needs kernel 3.5+.
+
config KLOGD
bool "klogd"
default y
@@ -123,6 +136,9 @@ config KLOGD
you wish to record the messages produced by the kernel,
you should enable this option.
+comment "klogd should not be used together with syslog to kernel printk buffer"
+ depends on KLOGD && FEATURE_KMSG_SYSLOG
+
config FEATURE_KLOGD_KLOGCTL
bool "Use the klogctl() interface"
default y
diff --git a/sysklogd/syslogd.c b/sysklogd/syslogd.c
index 5854bcd..ad54e22 100644
--- a/sysklogd/syslogd.c
+++ b/sysklogd/syslogd.c
@@ -43,6 +43,9 @@
//usage: "\n -f FILE Use FILE as config (default:/etc/syslog.conf)"
//usage: )
/* //usage: "\n -m MIN Minutes between MARK lines (default:20, 0=off)" */
+//usage: IF_FEATURE_KMSG_SYSLOG(
+//usage: "\n -K Log to kernel printk buffer (use dmesg to read it)"
+//usage: )
//usage:
//usage:#define syslogd_example_usage
//usage: "$ syslogd -R masterlog:514\n"
@@ -140,6 +143,10 @@ IF_FEATURE_IPC_SYSLOG( \
) \
IF_FEATURE_SYSLOGD_CFG( \
logRule_t *log_rules; \
+) \
+IF_FEATURE_KMSG_SYSLOG( \
+ int kmsgfd; \
+ int primask; \
)
struct init_globals {
@@ -212,6 +219,7 @@ enum {
IF_FEATURE_IPC_SYSLOG( OPTBIT_circularlog,) // -C
IF_FEATURE_SYSLOGD_DUP( OPTBIT_dup ,) // -D
IF_FEATURE_SYSLOGD_CFG( OPTBIT_cfg ,) // -f
+ IF_FEATURE_KMSG_SYSLOG( OPTBIT_kmsg ,) // -K
OPT_mark = 1 << OPTBIT_mark ,
OPT_nofork = 1 << OPTBIT_nofork ,
@@ -225,6 +233,8 @@ enum {
OPT_circularlog = IF_FEATURE_IPC_SYSLOG( (1 << OPTBIT_circularlog)) + 0,
OPT_dup = IF_FEATURE_SYSLOGD_DUP( (1 << OPTBIT_dup )) + 0,
OPT_cfg = IF_FEATURE_SYSLOGD_CFG( (1 << OPTBIT_cfg )) + 0,
+ OPT_kmsg = IF_FEATURE_KMSG_SYSLOG( (1 << OPTBIT_kmsg )) + 0,
+
};
#define OPTION_STR "m:nO:l:S" \
IF_FEATURE_ROTATE_LOGFILE("s:" ) \
@@ -233,7 +243,8 @@ enum {
IF_FEATURE_REMOTE_LOG( "L" ) \
IF_FEATURE_IPC_SYSLOG( "C::") \
IF_FEATURE_SYSLOGD_DUP( "D" ) \
- IF_FEATURE_SYSLOGD_CFG( "f:" )
+ IF_FEATURE_SYSLOGD_CFG( "f:" ) \
+ IF_FEATURE_KMSG_SYSLOG( "K" )
#define OPTION_DECL *opt_m, *opt_l \
IF_FEATURE_ROTATE_LOGFILE(,*opt_s) \
IF_FEATURE_ROTATE_LOGFILE(,*opt_b) \
@@ -523,6 +534,44 @@ void ipcsyslog_init(void);
void log_to_shmem(const char *msg);
#endif /* FEATURE_IPC_SYSLOG */
+#if ENABLE_FEATURE_KMSG_SYSLOG
+static void kmsg_init(void)
+{
+ G.kmsgfd = xopen("/dev/kmsg", O_WRONLY);
+
+ /*
+ * kernel < 3.5 expects single char printk KERN_* priority prefix,
+ * from 3.5 onwards the full syslog facility/priority format is supported
+ */
+ if (get_linux_version_code() < KERNEL_VERSION(3,5,0))
+ G.primask = LOG_PRIMASK;
+ else
+ G.primask = -1;
+}
+
+static void kmsg_cleanup(void)
+{
+ if (ENABLE_FEATURE_CLEAN_UP)
+ close(G.kmsgfd);
+}
+
+/* Write message to /dev/kmsg */
+static void log_to_kmsg(int pri, const char *msg)
+{
+ /*
+ * kernel < 3.5 expects single char printk KERN_* priority prefix,
+ * from 3.5 onwards the full syslog facility/priority format is supported
+ */
+ pri &= G.primask;
+
+ write(G.kmsgfd, G.printbuf, sprintf(G.printbuf, "<%d>%s\n", pri, msg));
+}
+#else
+void kmsg_init(void);
+void kmsg_cleanup(void);
+void log_to_kmsg(int pri, const char *msg);
+#endif /* FEATURE_KMSG_SYSLOG */
+
/* Print a message to the log file. */
static void log_locally(time_t now, char *msg, logFile_t *log_file)
{
@@ -657,6 +706,11 @@ static void timestamp_and_log(int pri, char *msg, int len)
}
timestamp[15] = '\0';
+ if (ENABLE_FEATURE_KMSG_SYSLOG && (option_mask32 & OPT_kmsg)) {
+ log_to_kmsg(pri, msg);
+ return;
+ }
+
if (option_mask32 & OPT_small)
sprintf(G.printbuf, "%s %s\n", timestamp, msg);
else {
@@ -831,6 +885,9 @@ static void do_syslogd(void)
ipcsyslog_init();
}
+ if (ENABLE_FEATURE_KMSG_SYSLOG && (option_mask32 & OPT_kmsg))
+ kmsg_init();
+
timestamp_and_log_internal("syslogd started: BusyBox v" BB_VER);
while (!bb_got_signal) {
@@ -919,6 +976,8 @@ static void do_syslogd(void)
remove_pidfile(CONFIG_PID_FILE_PATH "/syslogd.pid");
if (ENABLE_FEATURE_IPC_SYSLOG)
ipcsyslog_cleanup();
+ if (ENABLE_FEATURE_KMSG_SYSLOG && (option_mask32 & OPT_kmsg))
+ kmsg_cleanup();
kill_myself_with_sig(bb_got_signal);
#undef recvbuf
}