From 4c2c7b2c9461801cdc2b12fb342d39207e92c445 Mon Sep 17 00:00:00 2001
From: Ed Schouten <ed@FreeBSD.org>
Date: Wed, 14 Mar 2012 16:22:09 +0000
Subject: [PATCH] Make init(8) slightly more robust when /dev/console is
 missing.

If the environment doesn't offer a working /dev/console, the existing
version of init(8) will simply refuse running rc(8) scripts. This means
you'll only have a system running init(8) and nothing else.

Change the code to do the following:

- Open /dev/console like we used to do, but make it more robust to use
  O_NONBLOCK to prevent blocking on a carrier.
- If this fails, use /dev/null as stdin and /var/log/init.log as stdout
  and stderr.
- If even this fails, use /dev/null as stdin, stdout and stderr.

So why us this useful? Well, if you remove the `getpid() == 1' check in
main(), you can now use init(8) inside jails to properly execute rc(8).
It still requires some polishing, as existing tools assume init(8) has
PID 1.

Also it is now possible to use use init(8) on `headless' devices that
don't even have a serial boot console.
---
 etc/newsyslog.conf    |  1 +
 sbin/init/init.8      | 12 ++++++------
 sbin/init/init.c      | 38 +++++++++++++++++++++++++++-----------
 sbin/init/pathnames.h |  1 +
 4 files changed, 35 insertions(+), 17 deletions(-)

diff --git a/etc/newsyslog.conf b/etc/newsyslog.conf
index 67aa11726d6a..b750836e421c 100644
--- a/etc/newsyslog.conf
+++ b/etc/newsyslog.conf
@@ -24,6 +24,7 @@
 /var/log/cron				600  3	   100	*     JC
 /var/log/daily.log			640  7	   *	@T00  JN
 /var/log/debug.log			600  7     100  *     JC
+/var/log/init.log			644  3	   100	*     J
 /var/log/kerberos.log			600  7	   100	*     J
 /var/log/lpd-errs			644  7	   100	*     JC
 /var/log/maillog			640  7	   *	@T00  JC
diff --git a/sbin/init/init.8 b/sbin/init/init.8
index 1d7bc2e78403..fa9f7f0df8e4 100644
--- a/sbin/init/init.8
+++ b/sbin/init/init.8
@@ -31,7 +31,7 @@
 .\"     @(#)init.8	8.3 (Berkeley) 4/18/94
 .\" $FreeBSD$
 .\"
-.Dd February 11, 2012
+.Dd March 14, 2012
 .Dt INIT 8
 .Os
 .Sh NAME
@@ -293,22 +293,22 @@ as follows:
 file
 .El
 .Sh FILES
-.Bl -tag -width /etc/rc.shutdown -compact
+.Bl -tag -width /var/log/init.log -compact
 .It Pa /dev/console
 system console device
 .It Pa /dev/tty*
 terminal ports found in
 .Xr ttys 5
-.It Pa /var/run/utx.active
-record of current users on the system
-.It Pa /var/log/utx.log
-record of all logins and logouts
 .It Pa /etc/ttys
 the terminal initialization information file
 .It Pa /etc/rc
 system startup commands
 .It Pa /etc/rc.shutdown
 system shutdown commands
+.It Pa /var/log/init.log
+log of
+.Xr rc 8
+output if the system console device is not available
 .El
 .Sh DIAGNOSTICS
 .Bl -diag
diff --git a/sbin/init/init.c b/sbin/init/init.c
index 8ee7a8d51f7e..a24371cbc235 100644
--- a/sbin/init/init.c
+++ b/sbin/init/init.c
@@ -138,7 +138,7 @@ static void transition(state_t);
 static state_t requested_transition;
 static state_t current_state = death_single;
 
-static void setctty(const char *);
+static void open_console(void);
 static const char *get_shell(void);
 static void write_stderr(const char *message);
 
@@ -568,19 +568,35 @@ transition(state_t s)
  * Only called by children of init after forking.
  */
 static void
-setctty(const char *name)
+open_console(void)
 {
 	int fd;
 
-	revoke(name);
-	if ((fd = open(name, O_RDWR)) == -1) {
-		stall("can't open %s: %m", name);
+	/* Try to open /dev/console. */
+	revoke(_PATH_CONSOLE);
+	if ((fd = open(_PATH_CONSOLE, O_RDWR | O_NONBLOCK)) != -1) {
+		if (login_tty(fd) == 0)
+			return;
+		close(fd);
+	}
+
+	/* No luck.  Log output to file if possible. */
+	if ((fd = open(_PATH_DEVNULL, O_RDWR)) == -1) {
+		stall("cannot open null device.");
 		_exit(1);
 	}
-	if (login_tty(fd) == -1) {
-		stall("can't get %s for controlling terminal: %m", name);
-		_exit(1);
+	if (fd != STDIN_FILENO) {
+		dup2(fd, STDIN_FILENO);
+		close(fd);
 	}
+	fd = open(_PATH_INITLOG, O_WRONLY | O_APPEND | O_CREAT, 0644);
+	if (fd == -1)
+		dup2(STDIN_FILENO, STDOUT_FILENO);
+	else if (fd != STDOUT_FILENO) {
+		dup2(fd, STDOUT_FILENO);
+		close(fd);
+	}
+	dup2(STDOUT_FILENO, STDERR_FILENO);
 }
 
 static const char *
@@ -638,7 +654,7 @@ single_user(void)
 		/*
 		 * Start the single user session.
 		 */
-		setctty(_PATH_CONSOLE);
+		open_console();
 
 #ifdef SECURE
 		/*
@@ -798,7 +814,7 @@ run_script(const char *script)
 		sigaction(SIGTSTP, &sa, (struct sigaction *)0);
 		sigaction(SIGHUP, &sa, (struct sigaction *)0);
 
-		setctty(_PATH_CONSOLE);
+		open_console();
 
 		char _sh[]		= "sh";
 		char _autoboot[]	= "autoboot";
@@ -1572,7 +1588,7 @@ runshutdown(void)
 		sigaction(SIGTSTP, &sa, (struct sigaction *)0);
 		sigaction(SIGHUP, &sa, (struct sigaction *)0);
 
-		setctty(_PATH_CONSOLE);
+		open_console();
 
 		char _sh[]	= "sh";
 		char _reboot[]	= "reboot";
diff --git a/sbin/init/pathnames.h b/sbin/init/pathnames.h
index 335445bb0634..39eed4c868bb 100644
--- a/sbin/init/pathnames.h
+++ b/sbin/init/pathnames.h
@@ -35,6 +35,7 @@
 
 #include <paths.h>
 
+#define	_PATH_INITLOG	"/var/log/init.log"
 #define	_PATH_SLOGGER	"/sbin/session_logger"
 #define	_PATH_RUNCOM	"/etc/rc"
 #define _PATH_RUNDOWN   "/etc/rc.shutdown"