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>
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_SYSLOGD_CFG( \
logRule_t *log_rules; \
+) \
+IF_FEATURE_KMSG_SYSLOG( \
+ int kmsgfd; \
+ int primask; \
)
struct init_globals {
@@ -212,6 +219,7 @@
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 @@
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 @@
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 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 @@
}
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 @@
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 @@
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
}