+ 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 = COMMON_BUFSIZE,
+ OPT_LEVEL = (1 << 0),
+ 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)
+{
+ int i = 0;
+ char *opt_c;
+ int opt;
+ int used;
+
+ setup_common_bufsiz();
+
+ opt = getopt32(argv, "c:n", &opt_c);
+ if (opt & OPT_LEVEL) {
+ /* Valid levels are between 1 and 8 */
+ i = xatou_range(opt_c, 1, 8);
+ }
+ if (!(opt & OPT_FOREGROUND)) {
+ bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);
+ }
+
+ logmode = LOGMODE_SYSLOG;
+
+ /* 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);
+ /*
+ * glibc problem: for some reason, glibc changes LOG_KERN to LOG_USER
+ * above. The logic behind this is that standard
+ * http://pubs.opengroup.org/onlinepubs/9699919799/functions/syslog.html
+ * says the following about openlog and syslog:
+ * "LOG_USER
+ * Messages generated by arbitrary processes.
+ * This is the default facility identifier if none is specified."
+ *
+ * I believe glibc misinterpreted this text as "if openlog's
+ * third parameter is 0 (=LOG_KERN), treat it as LOG_USER".
+ * Whereas it was meant to say "if *syslog* is called with facility
+ * 0 in its 1st parameter without prior call to openlog, then perform
+ * implicit openlog(LOG_USER)".
+ *
+ * As a result of this, eh, feature, standard klogd was forced
+ * to open-code its own openlog and syslog implementation (!).
+ *
+ * Note that prohibiting openlog(LOG_KERN) on libc level does not
+ * add any security: any process can open a socket to "/dev/log"
+ * and write a string "<0>Voila, a LOG_KERN + LOG_EMERG message"
+ *
+ * Google code search tells me there is no widespread use of
+ * openlog("foo", 0, 0), thus fixing glibc won't break userspace.
+ *
+ * The bug against glibc was filed:
+ * bugzilla.redhat.com/show_bug.cgi?id=547000
+ */
+
+ if (i)
+ klogd_setloglevel(i);
+