Add tiny klogd implementation

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>

.gitignore

@@ -22,6 +22,7 @@ killall5
 runsvc
 syslog
 usyslogd
+klogd
 
 services/sigkill
 services/sigterm

Makefile.am

@@ -22,10 +22,7 @@ include cmd/Makemodule.am
 include initd/Makemodule.am
 include scripts/Makemodule.am
 include services/Makemodule.am
-
-if USYSLOGD
 include syslogd/Makemodule.am
-endif
 
 install-exec-hook:
 	(cd $(DESTDIR)$(sbindir); $(LN_S) shutdown reboot)
@@ -57,3 +54,6 @@ install-data-local:
 if USYSLOGD
 	$(LN_S) $(TEMPLATEDIR)/usyslogd $(DESTDIR)$(SVCDIR)/usyslogd
 endif
+if KLOGD
+	$(LN_S) $(TEMPLATEDIR)/klogd $(DESTDIR)$(SVCDIR)/klogd
+endif

configure.ac

@@ -46,6 +46,15 @@ AC_ARG_WITH([usyslogd],
 	esac],
 	[AM_CONDITIONAL([USYSLOGD], [true])])
 
+AC_ARG_WITH([klogd],
+	[AS_HELP_STRING([--without-klogd], [Build without kernel log daemon])],
+	[case "${withval}" in
+	yes) AM_CONDITIONAL([KLOGD], [true]) ;;
+	no) AM_CONDITIONAL([KLOGD], [false]) ;;
+	*) AC_MSG_ERROR([bad value ${withval} for --without-klogd]) ;;
+	esac],
+	[AM_CONDITIONAL([KLOGD], [true])])
+
 
 AC_CONFIG_HEADERS([lib/include/config.h])
 AC_DEFINE_DIR(SVCDIR, sysconfdir/init.d, [Startup service directory])

docs/defconfig.md

@@ -55,8 +55,10 @@ the `vfs` target and *before* the `sysinit` target:
 
  * hostname - reload hostname `/etc/hostname`
  * loopback - bring the loopback device up
- * usyslogd - if the `usyslogd` services is compiled with this package, this
+ * usyslogd - if the `usyslogd` service is compiled with this package, this
    service is enabled by default and starts `usyslogd`.
+ * klogd - if the `klogd` daemon is compiled with this package, this service
+   is enabled by default and starts after `usyslogd`.
  * modules - iterate over the file `/etc/modules` and try to load each module
    using modprobe.
  * sysctl - restore kernel parameters using `sysctl --system`. See `sysctl(8)`

docs/usyslogd.md

@@ -12,6 +12,15 @@ the log messages into files in the processes working directory (by default
 A simple log rotation scheme has been implemented.
 
 
+## Kernel Message Logging
+
+An additional small `klogd` daemon is provided that redirects kernel messages
+to the syslog daemon.
+
+It can be enabled or disabled independently of the `usyslogd` daemon and is
+designed to work with any other syslogd implementation.
+
+
 ## Security Considerations
 
 By default, the daemon switches its working directory to `/var/log`. The

services/Makemodule.am

@@ -14,8 +14,12 @@ if USYSLOGD
 init_DATA += services/usyslogd
 endif
 
+if USYSLOGD
+init_DATA += services/klogd
+endif
+
 EXTRA_DIST += services/sysinit services/vfs services/agetty services/hostname
-EXTRA_DIST += services/hwclock services/loopback
+EXTRA_DIST += services/hwclock services/loopback services/klogd
 EXTRA_DIST += services/sync services/sysctl services/tmpfs
 EXTRA_DIST += services/dhcpcd services/dhcpcdmaster services/unbound
 EXTRA_DIST += services/usyslogd services/dnsmasq services/network

services/klogd

@@ -0,0 +1,6 @@
+description "starting uklogd"
+exec klogd
+type respawn limit 5
+target boot
+after usyslogd
+before sysinit

syslogd/Makemodule.am

@@ -1,3 +1,4 @@
+if USYSLOGD
 usyslogd_SOURCES = syslogd/syslogd.c syslogd/syslogd.h
 usyslogd_SOURCES += syslogd/proto.c syslogd/logfile.c
 usyslogd_CPPFLAGS = $(AM_CPPFLAGS)
@@ -6,3 +7,13 @@ usyslogd_LDFLAGS = $(AM_LDFLAGS)
 usyslogd_LDADD = libinit.a
 
 sbin_PROGRAMS += usyslogd
+endif
+
+if KLOGD
+klogd_SOURCES = syslogd/klogd.c
+klogd_CPPFLAGS = $(AM_CPPFLAGS)
+klogd_CFLAGS = $(AM_CFLAGS)
+klogd_LDFLAGS = $(AM_LDFLAGS)
+
+sbin_PROGRAMS += klogd
+endif

syslogd/klogd.c

@@ -0,0 +1,191 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include <sys/klog.h>
+#include <syslog.h>
+#include <signal.h>
+#include <string.h>
+#include <stdlib.h>
+#include <getopt.h>
+#include <stdio.h>
+#include <errno.h>
+
+#include "config.h"
+
+enum {
+	KLOG_CLOSE = 0,
+	KLOG_OPEN = 1,
+	KLOG_READ = 2,
+	KLOG_CONSOLE_OFF = 6,
+	KLOG_CONSOLE_ON = 7,
+	KLOG_CONSOLE_LEVEL = 8,
+};
+
+static char log_buffer[4096];
+static sig_atomic_t running = 1;
+static int level = 0;
+
+static const struct option options[] = {
+	{ "help", no_argument, NULL, 'h' },
+	{ "version", no_argument, NULL, 'V' },
+	{ "level", required_argument, NULL, 'l' },
+	{ NULL, 0, NULL, 0 },
+};
+
+static const char *shortopt = "hVl:";
+
+static const char *versiontext =
+"klogd (Pygos init) "PACKAGE_VERSION"\n"
+"Copyright (C) 2018 David Oberhollenzer\n"
+"License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.\n"
+"This is free software: you are free to change and redistribute it.\n"
+"There is NO WARRANTY, to the extent permitted by law.\n";
+
+static const char *helptext =
+"Usage: klogd [OPTION]... \n\n"
+"Collect printk() messages from the kernel and forward them to syslogd.\n"
+"\n"
+"The following OPTIONSs can be used:\n"
+"  -l, --level <level>  Minimum log level that should be printed to console.\n"
+"                       If not set, logging to console is turned off.\n"
+"  -h, --help           Print this help text and exit\n"
+"  -V, --version        Print version information and exit\n\n";
+
+static void process_options(int argc, char **argv)
+{
+	int c;
+
+	for (;;) {
+		c = getopt_long(argc, argv, shortopt, options, NULL);
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'l':
+			level = strtoul(optarg, NULL, 10);
+			break;
+		case 'h':
+			fputs(helptext, stdout);
+			exit(EXIT_SUCCESS);
+		case 'V':
+			fputs(versiontext, stdout);
+			exit(EXIT_SUCCESS);
+		default:
+			fputs("Try `klogd --help' for more information\n",
+			      stderr);
+			exit(EXIT_FAILURE);
+		}
+	}
+}
+
+static void sighandler(int signo)
+{
+	if (signo == SIGTERM || signo == SIGINT)
+		running = 0;
+}
+
+static void sigsetup(void)
+{
+	struct sigaction act;
+	sigset_t mask;
+
+	memset(&act, 0, sizeof(act));
+	act.sa_handler = sighandler;
+	sigaction(SIGTERM, &act, NULL);
+	sigaction(SIGINT, &act, NULL);
+
+	sigfillset(&mask);
+	sigdelset(&mask, SIGTERM);
+	sigdelset(&mask, SIGINT);
+	sigprocmask(SIG_SETMASK, &mask, NULL);
+}
+
+static void log_open(void)
+{
+	klogctl(KLOG_OPEN, NULL, 0);
+
+	if (level) {
+		klogctl(KLOG_CONSOLE_LEVEL, NULL, level);
+	} else {
+		klogctl(KLOG_CONSOLE_OFF, NULL, 0);
+	}
+
+	openlog("kernel", 0, LOG_KERN);
+}
+
+static void log_close(void)
+{
+	klogctl(KLOG_CONSOLE_ON, NULL, 0);
+	klogctl(KLOG_CLOSE, NULL, 0);
+	syslog(LOG_NOTICE, "-- klogd terminating --");
+}
+
+int main(int argc, char **argv)
+{
+	int diff, count = 0, priority, ret = EXIT_SUCCESS;
+	char *ptr, *end;
+
+	process_options(argc, argv);
+	sigsetup();
+	log_open();
+
+	/* TODO: seccomp lockdown? */
+
+	while (running) {
+		diff = klogctl(KLOG_READ, log_buffer + count,
+			       sizeof(log_buffer) - 1 - count);
+
+		if (diff < 0) {
+			if (errno == EINTR)
+				continue;
+			syslog(LOG_CRIT, "klogctl read: %s", strerror(errno));
+			ret = EXIT_FAILURE;
+			break;
+		}
+
+		count += diff;
+		log_buffer[count] = '\0';
+		ptr = log_buffer;
+
+		for (;;) {
+			end = strchr(ptr, '\n');
+			if (end == NULL) {
+				count = strlen(ptr);
+				memmove(log_buffer, ptr, count);
+				break;
+			}
+
+			*(end++) = '\0';
+			priority = LOG_INFO;
+
+			if (*ptr == '<') {
+				++ptr;
+				if (*ptr)
+					priority = strtoul(ptr, &ptr, 10);
+				if (*ptr == '>')
+					++ptr;
+			}
+
+			if (*ptr)
+				syslog(priority, "%s", ptr);
+			ptr = end;
+		}
+	}
+
+	log_close();
+	return ret;
+}