Add tiny klogd implementation

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

1 files changed, 191 insertions, 0 deletions

diff --git a/syslogd/klogd.c b/syslogd/klogd.c
new file mode 100644
index 0000000..ca16e4e
--- /dev/null
+++ b/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;
+}