d0bbbdcd6

Denis Vlasenko

2007-12-04

FAILED Duration: 12s

Subject

getty: don't accept ancient '#' and '@' as backspace/kill line, it only confuses people. (Alexander Griesser (LKH Villach)) various other cleanups.

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No binary (build failed)

Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

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Commit Diff GitHub →

docs/ctty.htm +474 -0 loginutils/getty.c +165 -227

docs/ctty.htm+474 -0

@@ -0,0 +1,474 @@
+	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
+	<html><head>
+	<!-- saved from http://www.win.tue.nl/~aeb/linux/lk/lk-10.html -->
+	<meta name="GENERATOR" content="SGML-Tools 1.0.9"><title>The Linux kernel: Processes</title>
+	</head>
+	<body>
+	<hr>
+	<h2><a name="s10">10. Processes</a></h2>
+
+	<p>Before looking at the Linux implementation, first a general Unix
+	description of threads, processes, process groups and sessions.
+	</p><p>A session contains a number of process groups, and a process group
+	contains a number of processes, and a process contains a number
+	of threads.
+	</p><p>A session can have a controlling tty.
+	At most one process group in a session can be a foreground process group.
+	An interrupt character typed on a tty ("Teletype", i.e., terminal)
+	causes a signal to be sent to all members of the foreground process group
+	in the session (if any) that has that tty as controlling tty.
+	</p><p>All these objects have numbers, and we have thread IDs, process IDs,
+	process group IDs and session IDs.
+	</p><p>
+	</p><h2><a name="ss10.1">10.1 Processes</a>
+	</h2>
+
+	<p>
+	</p><h3>Creation</h3>
+
+	<p>A new process is traditionally started using the <code>fork()</code>
+	system call:
+	</p><blockquote>
+	<pre>pid_t p;
+
+	p = fork();
+	if (p == (pid_t) -1)
+	/* ERROR */
+	else if (p == 0)
+	/* CHILD */
+	else
+	/* PARENT */
+	</pre>
+	</blockquote>
+	<p>This creates a child as a duplicate of its parent.
+	Parent and child are identical in almost all respects.
+	In the code they are distinguished by the fact that the parent
+	learns the process ID of its child, while <code>fork()</code>
+	returns 0 in the child. (It can find the process ID of its
+	parent using the <code>getppid()</code> system call.)
+	</p><p>
+	</p><h3>Termination</h3>
+
+	<p>Normal termination is when the process does
+	</p><blockquote>
+	<pre>exit(n);
+	</pre>
+	</blockquote>
+
+	or
+	<blockquote>
+	<pre>return n;
+	</pre>
+	</blockquote>
+
+	from its <code>main()</code> procedure. It returns the single byte <code>n</code>
+	to its parent.
+	<p>Abnormal termination is usually caused by a signal.
+	</p><p>
+	</p><h3>Collecting the exit code. Zombies</h3>
+
+	<p>The parent does
+	</p><blockquote>
+	<pre>pid_t p;
+	int status;
+
+	p = wait(&status);
+	</pre>
+	</blockquote>
+
+	and collects two bytes:
+	<p>
+	<figure>
+	<eps file="absent">
+	<img src="ctty_files/exit_status.png">
+	</eps>
+	</figure></p><p>A process that has terminated but has not yet been waited for
+	is a <i>zombie</i>. It need only store these two bytes:
+	exit code and reason for termination.
+	</p><p>On the other hand, if the parent dies first, <code>init</code> (process 1)
+	inherits the child and becomes its parent.
+	</p><p>
+	</p><h3>Signals</h3>
+
+	<p>
+	</p><h3>Stopping</h3>
+
+	<p>Some signals cause a process to stop:
+	<code>SIGSTOP</code> (stop!),
+	<code>SIGTSTP</code> (stop from tty: probably ^Z was typed),
+	<code>SIGTTIN</code> (tty input asked by background process),
+	<code>SIGTTOU</code> (tty output sent by background process, and this was
+	disallowed by <code>stty tostop</code>).
+	</p><p>Apart from ^Z there also is ^Y. The former stops the process
+	when it is typed, the latter stops it when it is read.
+	</p><p>Signals generated by typing the corresponding character on some tty
+	are sent to all processes that are in the foreground process group
+	of the session that has that tty as controlling tty. (Details below.)
+	</p><p>If a process is being traced, every signal will stop it.
+	</p><p>
+	</p><h3>Continuing</h3>
+
+	<p><code>SIGCONT</code>: continue a stopped process.
+	</p><p>
+	</p><h3>Terminating</h3>
+
+	<p><code>SIGKILL</code> (die! now!),
+	<code>SIGTERM</code> (please, go away),
+	<code>SIGHUP</code> (modem hangup),
+	<code>SIGINT</code> (^C),
+	<code>SIGQUIT</code> (^\), etc.
+	Many signals have as default action to kill the target.
+	(Sometimes with an additional core dump, when such is
+	allowed by rlimit.)
+	The signals <code>SIGCHLD</code> and <code>SIGWINCH</code>
+	are ignored by default.
+	All except <code>SIGKILL</code> and <code>SIGSTOP</code> can be
+	caught or ignored or blocked.
+	For details, see <code>signal(7)</code>.
+	</p><p>
+	</p><h2><a name="ss10.2">10.2 Process groups</a>
+	</h2>
+
+	<p>Every process is member of a unique <i>process group</i>,
+	identified by its <i>process group ID</i>.
+	(When the process is created, it becomes a member of the process group
+	of its parent.)
+	By convention, the process group ID of a process group
+	equals the process ID of the first member of the process group,
+	called the <i>process group leader</i>.
+	A process finds the ID of its process group using the system call
+	<code>getpgrp()</code>, or, equivalently, <code>getpgid(0)</code>.
+	One finds the process group ID of process <code>p</code> using
+	<code>getpgid(p)</code>.
+	</p><p>One may use the command <code>ps j</code> to see PPID (parent process ID),
+	PID (process ID), PGID (process group ID) and SID (session ID)
+	of processes. With a shell that does not know about job control,
+	like <code>ash</code>, each of its children will be in the same session
+	and have the same process group as the shell. With a shell that knows
+	about job control, like <code>bash</code>, the processes of one pipeline. like
+	</p><blockquote>
+	<pre>% cat paper \| ideal \| pic \| tbl \| eqn \| ditroff > out
+	</pre>
+	</blockquote>
+
+	form a single process group.
+	<p>
+	</p><h3>Creation</h3>
+
+	<p>A process <code>pid</code> is put into the process group <code>pgid</code> by
+	</p><blockquote>
+	<pre>setpgid(pid, pgid);
+	</pre>
+	</blockquote>
+
+	If <code>pgid == pid</code> or <code>pgid == 0</code> then this creates
+	a new process group with process group leader <code>pid</code>.
+	Otherwise, this puts <code>pid</code> into the already existing
+	process group <code>pgid</code>.
+	A zero <code>pid</code> refers to the current process.
+	The call <code>setpgrp()</code> is equivalent to <code>setpgid(0,0)</code>.
+	<p>
+	</p><h3>Restrictions on setpgid()</h3>
+
+	<p>The calling process must be <code>pid</code> itself, or its parent,
+	and the parent can only do this before <code>pid</code> has done
+	<code>exec()</code>, and only when both belong to the same session.
+	It is an error if process <code>pid</code> is a session leader
+	(and this call would change its <code>pgid</code>).
+	</p><p>
+	</p><h3>Typical sequence</h3>
+
+	<p>
+	</p><blockquote>
+	<pre>p = fork();
+	if (p == (pid_t) -1) {
+	/* ERROR */
+	} else if (p == 0) { /* CHILD */
+	setpgid(0, pgid);
+	...
+	} else { /* PARENT */
+	setpgid(p, pgid);
+	...
+	}
+	</pre>
+	</blockquote>
+
+	This ensures that regardless of whether parent or child is scheduled
+	first, the process group setting is as expected by both.
+	<p>
+	</p><h3>Signalling and waiting</h3>
+
+	<p>One can signal all members of a process group:
+	</p><blockquote>
+	<pre>killpg(pgrp, sig);
+	</pre>
+	</blockquote>
+	<p>One can wait for children in ones own process group:
+	</p><blockquote>
+	<pre>waitpid(0, &status, ...);
+	</pre>
+	</blockquote>
+
+	or in a specified process group:
+	<blockquote>
+	<pre>waitpid(-pgrp, &status, ...);
+	</pre>
+	</blockquote>
+	<p>
+	</p><h3>Foreground process group</h3>
+
+	<p>Among the process groups in a session at most one can be
+	the <i>foreground process group</i> of that session.
+	The tty input and tty signals (signals generated by ^C, ^Z, etc.)
+	go to processes in this foreground process group.
+	</p><p>A process can determine the foreground process group in its session
+	using <code>tcgetpgrp(fd)</code>, where <code>fd</code> refers to its
+	controlling tty. If there is none, this returns a random value
+	larger than 1 that is not a process group ID.
+	</p><p>A process can set the foreground process group in its session
+	using <code>tcsetpgrp(fd,pgrp)</code>, where <code>fd</code> refers to its
+	controlling tty, and <code>pgrp</code> is a process group in the
+	its session, and this session still is associated to the controlling
+	tty of the calling process.
+	</p><p>How does one get <code>fd</code>? By definition, <code>/dev/tty</code>
+	refers to the controlling tty, entirely independent of redirects
+	of standard input and output. (There is also the function
+	<code>ctermid()</code> to get the name of the controlling terminal.
+	On a POSIX standard system it will return <code>/dev/tty</code>.)
+	Opening the name of the
+	controlling tty gives a file descriptor <code>fd</code>.
+	</p><p>
+	</p><h3>Background process groups</h3>
+
+	<p>All process groups in a session that are not foreground
+	process group are <i>background process groups</i>.
+	Since the user at the keyboard is interacting with foreground
+	processes, background processes should stay away from it.
+	When a background process reads from the terminal it gets
+	a SIGTTIN signal. Normally, that will stop it, the job control shell
+	notices and tells the user, who can say <code>fg</code> to continue
+	this background process as a foreground process, and then this
+	process can read from the terminal. But if the background process
+	ignores or blocks the SIGTTIN signal, or if its process group
+	is orphaned (see below), then the read() returns an EIO error,
+	and no signal is sent. (Indeed, the idea is to tell the process
+	that reading from the terminal is not allowed right now.
+	If it wouldn't see the signal, then it will see the error return.)
+	</p><p>When a background process writes to the terminal, it may get
+	a SIGTTOU signal. May: namely, when the flag that this must happen
+	is set (it is off by default). One can set the flag by
+	</p><blockquote>
+	<pre>% stty tostop
+	</pre>
+	</blockquote>
+
+	and clear it again by
+	<blockquote>
+	<pre>% stty -tostop
+	</pre>
+	</blockquote>
+
+	and inspect it by
+	<blockquote>
+	<pre>% stty -a
+	</pre>
+	</blockquote>
+
+	Again, if TOSTOP is set but the background process ignores or blocks
+	the SIGTTOU signal, or if its process group is orphaned (see below),
+	then the write() returns an EIO error, and no signal is sent.
+	<p>
+	</p><h3>Orphaned process groups</h3>
+
+	<p>The process group leader is the first member of the process group.
+	It may terminate before the others, and then the process group is
+	without leader.
+	</p><p>A process group is called <i>orphaned</i> when <i>the
+	parent of every member is either in the process group
+	or outside the session</i>.
+	In particular, the process group of the session leader
+	is always orphaned.
+	</p><p>If termination of a process causes a process group to become
+	orphaned, and some member is stopped, then all are sent first SIGHUP
+	and then SIGCONT.
+	</p><p>The idea is that perhaps the parent of the process group leader
+	is a job control shell. (In the same session but a different
+	process group.) As long as this parent is alive, it can
+	handle the stopping and starting of members in the process group.
+	When it dies, there may be nobody to continue stopped processes.
+	Therefore, these stopped processes are sent SIGHUP, so that they
+	die unless they catch or ignore it, and then SIGCONT to continue them.
+	</p><p>Note that the process group of the session leader is already
+	orphaned, so no signals are sent when the session leader dies.
+	</p><p>Note also that a process group can become orphaned in two ways
+	by termination of a process: either it was a parent and not itself
+	in the process group, or it was the last element of the process group
+	with a parent outside but in the same session.
+	Furthermore, that a process group can become orphaned
+	other than by termination of a process, namely when some
+	member is moved to a different process group.
+	</p><p>
+	</p><h2><a name="ss10.3">10.3 Sessions</a>
+	</h2>
+
+	<p>Every process group is in a unique <i>session</i>.
+	(When the process is created, it becomes a member of the session
+	of its parent.)
+	By convention, the session ID of a session
+	equals the process ID of the first member of the session,
+	called the <i>session leader</i>.
+	A process finds the ID of its session using the system call
+	<code>getsid()</code>.
+	</p><p>Every session may have a <i>controlling tty</i>,
+	that then also is called the controlling tty of each of
+	its member processes.
+	A file descriptor for the controlling tty is obtained by
+	opening <code>/dev/tty</code>. (And when that fails, there was no
+	controlling tty.) Given a file descriptor for the controlling tty,
+	one may obtain the SID using <code>tcgetsid(fd)</code>.
+	</p><p>A session is often set up by a login process. The terminal
+	on which one is logged in then becomes the controlling tty
+	of the session. All processes that are descendants of the
+	login process will in general be members of the session.
+	</p><p>
+	</p><h3>Creation</h3>
+
+	<p>A new session is created by
+	</p><blockquote>
+	<pre>pid = setsid();
+	</pre>
+	</blockquote>
+
+	This is allowed only when the current process is not a process group leader.
+	In order to be sure of that we fork first:
+	<blockquote>
+	<pre>p = fork();
+	if (p) exit(0);
+	pid = setsid();
+	</pre>
+	</blockquote>
+
+	The result is that the current process (with process ID <code>pid</code>)
+	becomes session leader of a new session with session ID <code>pid</code>.
+	Moreover, it becomes process group leader of a new process group.
+	Both session and process group contain only the single process <code>pid</code>.
+	Furthermore, this process has no controlling tty.
+	<p>The restriction that the current process must not be a process group leader
+	is needed: otherwise its PID serves as PGID of some existing process group
+	and cannot be used as the PGID of a new process group.
+	</p><p>
+	</p><h3>Getting a controlling tty</h3>
+
+	<p>How does one get a controlling terminal? Nobody knows,
+	this is a great mystery.
+	</p><p>The System V approach is that the first tty opened by the process
+	becomes its controlling tty.
+	</p><p>The BSD approach is that one has to explicitly call
+	</p><blockquote>
+	<pre>ioctl(fd, TIOCSCTTY, ...);
+	</pre>
+	</blockquote>
+
+	to get a controlling tty.
+	<p>Linux tries to be compatible with both, as always, and this
+	results in a very obscure complex of conditions. Roughly:
+	</p><p>The <code>TIOCSCTTY</code> ioctl will give us a controlling tty,
+	provided that (i) the current process is a session leader,
+	and (ii) it does not yet have a controlling tty, and
+	(iii) maybe the tty should not already control some other session;
+	if it does it is an error if we aren't root, or we steal the tty
+	if we are all-powerful.
+	</p><p>Opening some terminal will give us a controlling tty,
+	provided that (i) the current process is a session leader, and
+	(ii) it does not yet have a controlling tty, and
+	(iii) the tty does not already control some other session, and
+	(iv) the open did not have the <code>O_NOCTTY</code> flag, and
+	(v) the tty is not the foreground VT, and
+	(vi) the tty is not the console, and
+	(vii) maybe the tty should not be master or slave pty.
+	</p><p>
+	</p><h3>Getting rid of a controlling tty</h3>
+
+	<p>If a process wants to continue as a daemon, it must detach itself
+	from its controlling tty. Above we saw that <code>setsid()</code>
+	will remove the controlling tty. Also the ioctl TIOCNOTTY does this.
+	Moreover, in order not to get a controlling tty again as soon as it
+	opens a tty, the process has to fork once more, to assure that it
+	is not a session leader. Typical code fragment:
+	</p><p>
+	</p><pre> if ((fork()) != 0)
+	exit(0);
+	setsid();
+	if ((fork()) != 0)
+	exit(0);
+	</pre>
+	<p>See also <code>daemon(3)</code>.
+	</p><p>
+	</p><h3>Disconnect</h3>
+
+	<p>If the terminal goes away by modem hangup, and the line was not local,
+	then a SIGHUP is sent to the session leader.
+	Any further reads from the gone terminal return EOF.
+	(Or possibly -1 with <code>errno</code> set to EIO.)
+	</p><p>If the terminal is the slave side of a pseudotty, and the master side
+	is closed (for the last time), then a SIGHUP is sent to the foreground
+	process group of the slave side.
+	</p><p>When the session leader dies, a SIGHUP is sent to all processes
+	in the foreground process group. Moreover, the terminal stops being
+	the controlling terminal of this session (so that it can become
+	the controlling terminal of another session).
+	</p><p>Thus, if the terminal goes away and the session leader is
+	a job control shell, then it can handle things for its descendants,
+	e.g. by sending them again a SIGHUP.
+	If on the other hand the session leader is an innocent process
+	that does not catch SIGHUP, it will die, and all foreground processes
+	get a SIGHUP.
+	</p><p>
+	</p><h2><a name="ss10.4">10.4 Threads</a>
+	</h2>
+
+	<p>A process can have several threads. New threads (with the same PID
+	as the parent thread) are started using the <code>clone</code> system
+	call using the <code>CLONE_THREAD</code> flag. Threads are distinguished
+	by a <i>thread ID</i> (TID). An ordinary process has a single thread
+	with TID equal to PID. The system call <code>gettid()</code> returns the
+	TID. The system call <code>tkill()</code> sends a signal to a single thread.
+	</p><p>Example: a process with two threads. Both only print PID and TID and exit.
+	(Linux 2.4.19 or later.)
+	</p><pre>% cat << EOF > gettid-demo.c
+	#include <unistd.h>
+	#include <sys/types.h>
+	#define CLONE_SIGHAND 0x00000800
+	#define CLONE_THREAD 0x00010000
+	#include <linux/unistd.h>
+	#include <errno.h>
+	_syscall0(pid_t,gettid)
+
+	int thread(void *p) {
+	printf("thread: %d %d\n", gettid(), getpid());
+	}
+
+	main() {
+	unsigned char stack[4096];
+	int i;
+
+	i = clone(thread, stack+2048, CLONE_THREAD \| CLONE_SIGHAND, NULL);
+	if (i == -1)
+	perror("clone");
+	else
+	printf("clone returns %d\n", i);
+	printf("parent: %d %d\n", gettid(), getpid());
+	}
+	EOF
+	% cc -o gettid-demo gettid-demo.c
+	% ./gettid-demo
+	clone returns 21826
+	parent: 21825 21825
+	thread: 21826 21825
+	%
+	</pre>
+	<p>
+	</p><p>
+	</p><hr>
+
+	</body></html>

loginutils/getty.c+165 -227

@@ -33,7 +33,6 @@
	#include <time.h>
	#if ENABLE_FEATURE_WTMP
	extern void updwtmp(const char filename, const struct utmp ut);
-	static void update_utmp(const char *line);
	#endif
	#endif /* LOGIN_PROCESS */

@@ -47,6 +46,7 @@ static void update_utmp(const char *line);

	/* I doubt there are systems which still need this */
	#undef HANDLE_ALLCAPS
+	#undef ANCIENT_BS_KILL_CHARS

	#define _PATH_LOGIN "/bin/login"

@@ -76,36 +76,20 @@ static void update_utmp(const char *line);
	* When multiple baud rates are specified on the command line, the first one
	* we will try is the first one specified.
	*/
-	#define FIRST_SPEED 0
-
-	/* Storage for command-line options. */
-
	#define MAX_SPEED 10 /* max. nr. of baud rates */

+	/* Storage for command-line options. */
	struct options {
	int flags; /* toggle switches, see below */
	unsigned timeout; /* time-out period */
-	const char login; / login program */
-	const char tty; / name of tty */
-	const char initstring; / modem init string */
-	const char issue; / alternative issue file */
+	const char login; / login program */
+	const char tty; / name of tty */
+	const char initstring; / modem init string */
+	const char issue; / alternative issue file */
	int numspeed; /* number of baud rates to try */
	int speeds[MAX_SPEED]; /* baud rates to be tried */
	};

-	static const char opt_string[] ALIGN1 = "I:LH:f:hil:mt:wn";
-	#define F_INITSTRING (1<<0) /* initstring is set */
-	#define F_LOCAL (1<<1) /* force local */
-	#define F_FAKEHOST (1<<2) /* force fakehost */
-	#define F_CUSTISSUE (1<<3) /* give alternative issue file */
-	#define F_RTSCTS (1<<4) /* enable RTS/CTS flow control */
-	#define F_ISSUE (1<<5) /* display /etc/issue */
-	#define F_LOGIN (1<<6) /* non-default login program */
-	#define F_PARSE (1<<7) /* process modem status messages */
-	#define F_TIMEOUT (1<<8) /* time out */
-	#define F_WAITCRLF (1<<9) /* wait for CR or LF */
-	#define F_NOPROMPT (1<<10) /* don't ask for login name! */
-
	/* Storage for things detected while the login name was read. */
	struct chardata {
	unsigned char erase; /* erase character */
@@ -117,6 +101,7 @@ struct chardata {
	#endif
	};

+
	/* Initial values for the above. */
	static const struct chardata init_chardata = {
	DEF_ERASE, /* default erase character */
@@ -128,12 +113,25 @@ static const struct chardata init_chardata = {
	#endif
	};

-	/* The following is used for understandable diagnostics. */
+	static const char opt_string[] ALIGN1 = "I:LH:f:hil:mt:wn";
+	#define F_INITSTRING (1 << 0) /* -I initstring is set */
+	#define F_LOCAL (1 << 1) /* -L force local */
+	#define F_FAKEHOST (1 << 2) /* -H force fakehost */
+	#define F_CUSTISSUE (1 << 3) /* -f give alternative issue file */
+	#define F_RTSCTS (1 << 4) /* -h enable RTS/CTS flow control */
+	#define F_ISSUE (1 << 5) /* -i display /etc/issue */
+	#define F_LOGIN (1 << 6) /* -l non-default login program */
+	#define F_PARSE (1 << 7) /* -m process modem status messages */
+	#define F_TIMEOUT (1 << 8) /* -t time out */
+	#define F_WAITCRLF (1 << 9) /* -w wait for CR or LF */
+	#define F_NOPROMPT (1 << 10) /* -n don't ask for login name! */
+

	/* Fake hostname for ut_host specified on command line. */
	static char *fakehost = NULL;
+	#define line_buf bb_common_bufsiz1

-	/* ... */
+	/* The following is used for understandable diagnostics. */
	#ifdef DEBUGGING
	#define debug(s) fprintf(dbf,s); fflush(dbf)
	#define DEBUGTERM "/dev/ttyp0"
@@ -158,14 +156,14 @@ static int bcode(const char *s)
	return 0;
	}

-
	/* parse_speeds - parse alternate baud rates */
	static void parse_speeds(struct options op, char arg)
	{
	char *cp;

+	/* NB: at least one iteration is always done */
	debug("entered parse_speeds\n");
-	for (cp = strtok(arg, ","); cp != 0; cp = strtok((char *) 0, ",")) {
+	while ((cp = strsep(&arg, ",")) != NULL) {
	op->speeds[op->numspeed] = bcode(cp);
	if (op->speeds[op->numspeed] <= 0)
	bb_error_msg_and_die("bad speed: %s", cp);
@@ -173,18 +171,19 @@ static void parse_speeds(struct options op, char arg)
	if (op->numspeed > MAX_SPEED)
	bb_error_msg_and_die("too many alternate speeds");
	}
-	debug("exiting parsespeeds\n");
+	debug("exiting parse_speeds\n");
	}

-
	/* parse_args - parse command-line arguments */
-	static void parse_args(int argc, char *argv, struct options op)
+	static void parse_args(char *argv, struct options op)
	{
	char *ts;

+	opt_complementary = "-2"; /* at least 2 args */
	op->flags = getopt32(argv, opt_string,
	&(op->initstring), &fakehost, &(op->issue),
	&(op->login), &ts);
+	argv += optind;
	if (op->flags & F_INITSTRING) {
	const char *p = op->initstring;
	char *q;
@@ -202,45 +201,40 @@ static void parse_args(int argc, char *argv, struct options op)
	}
	*q = '\0';
	}
-	op->flags ^= F_ISSUE; /* revert flag show /etc/issue */
+	op->flags ^= F_ISSUE; /* invert flag show /etc/issue */
	if (op->flags & F_TIMEOUT) {
-	op->timeout = xatoul_range(ts, 1, INT_MAX);
+	op->timeout = xatoi_u(ts);
	}
-	argv += optind;
-	argc -= optind;
-	debug("after getopt loop\n");
-	if (argc < 2) /* check parameter count */
-	bb_show_usage();
+	debug("after getopt\n");

	/* we loosen up a bit and accept both "baudrate tty" and "tty baudrate" */
+	op->tty = argv[0]; /* tty name */
+	ts = argv[1]; /* baud rate(s) */
	if (isdigit(argv[0][0])) {
	/* a number first, assume it's a speed (BSD style) */
-	parse_speeds(op, argv[0]); /* baud rate(s) */
-	op->tty = argv[1]; /* tty name */
-	} else {
-	op->tty = argv[0]; /* tty name */
-	parse_speeds(op, argv[1]); /* baud rate(s) */
+	op->tty = ts; /* tty name is in argv[1] */
+	ts = argv[0]; /* baud rate(s) */
	}
+	parse_speeds(op, ts);

	if (argv[2])
	setenv("TERM", argv[2], 1);

-	debug("exiting parseargs\n");
+	debug("exiting parse_args\n");
	}

	/* open_tty - set up tty as standard { input, output, error } */
-	static void open_tty(const char tty, struct termios tp, int local)
+	static void open_tty(const char *tty)
	{
-	int chdir_to_root = 0;
-
	/* Set up new standard input, unless we are given an already opened port. */
	if (NOT_LONE_DASH(tty)) {
	struct stat st;
+	int cur_dir_fd;
	int fd;

	/* Sanity checks... */
+	cur_dir_fd = xopen(".", O_DIRECTORY \| O_NONBLOCK);
	xchdir("/dev");
-	chdir_to_root = 1;
	xstat(tty, &st);
	if ((st.st_mode & S_IFMT) != S_IFCHR)
	bb_error_msg_and_die("%s: not a character device", tty);
@@ -248,9 +242,23 @@ static void open_tty(const char tty, struct termios tp, int local)
	/* Open the tty as standard input. */
	debug("open(2)\n");
	fd = xopen(tty, O_RDWR \| O_NONBLOCK);
+
+	/* Restore current directory */
+	fchdir(cur_dir_fd);
+
+	/* Open the tty as standard input, continued */
	xdup2(fd, 0);
+	/* fd is >= cur_dir_fd, and cur_dir_fd gets closed too here: */
	while (fd > 2)
	close(fd--);
+
+	/* Set proper protections and ownership. Mode 0622
+	* is suitable for SYSV < 4 because /bin/login does not change
+	* protections. SunOS 4 login will change the protections to 0620
+	* (write access for group tty) after the login has succeeded.
+	*/
+	fchown(0, 0, 0); /* 0:0 */
+	fchmod(0, 0622); /* crw--w--w- */
	} else {
	/*
	* Standard input should already be connected to an open port. Make
@@ -259,71 +267,6 @@ static void open_tty(const char tty, struct termios tp, int local)
	if ((fcntl(0, F_GETFL) & O_RDWR) != O_RDWR)
	bb_error_msg_and_die("stdin is not open for read/write");
	}
-
-	/* Replace current standard output/error fd's with new ones */
-	debug("duping\n");
-	xdup2(0, 1);
-	xdup2(0, 2);
-
-	/*
-	* The following ioctl will fail if stdin is not a tty, but also when
-	* there is noise on the modem control lines. In the latter case, the
-	* common course of action is (1) fix your cables (2) give the modem more
-	* time to properly reset after hanging up. SunOS users can achieve (2)
-	* by patching the SunOS kernel variable "zsadtrlow" to a larger value;
-	* 5 seconds seems to be a good value.
-	*/
-	ioctl_or_perror_and_die(0, TCGETS, tp, "%s: TCGETS", tty);
-
-	/*
-	* It seems to be a terminal. Set proper protections and ownership. Mode
-	* 0622 is suitable for SYSV <4 because /bin/login does not change
-	* protections. SunOS 4 login will change the protections to 0620 (write
-	* access for group tty) after the login has succeeded.
-	*/
-
-	#ifdef DEBIAN
-	#warning Debian /dev/vcs[a]NN hack is deprecated and will be removed
-	{
-	/* tty to root.dialout 660 */
-	struct group *gr;
-	int id;
-
-	gr = getgrnam("dialout");
-	id = gr ? gr->gr_gid : 0;
-	chown(tty, 0, id);
-	chmod(tty, 0660);
-
-	/* vcs,vcsa to root.sys 600 */
-	if (!strncmp(tty, "tty", 3) && isdigit(tty[3])) {
-	char vcs, vcsa;
-
-	vcs = xstrdup(tty);
-	vcsa = xmalloc(strlen(tty) + 2);
-	strcpy(vcs, "vcs");
-	strcpy(vcs + 3, tty + 3);
-	strcpy(vcsa, "vcsa");
-	strcpy(vcsa + 4, tty + 3);
-
-	gr = getgrnam("sys");
-	id = gr ? gr->gr_gid : 0;
-	chown(vcs, 0, id);
-	chmod(vcs, 0600);
-	chown(vcsa, 0, id);
-	chmod(vcs, 0600);
-
-	free(vcs);
-	free(vcsa);
-	}
-	}
-	#else
-	if (NOT_LONE_DASH(tty)) {
-	chown(tty, 0, 0); /* 0:0 */
-	chmod(tty, 0622); /* crw--w--w- */
-	}
-	#endif
-	if (chdir_to_root)
-	xchdir("/");
	}

	/* termios_init - initialize termios settings */
@@ -351,17 +294,13 @@ static void termios_init(struct termios tp, int speed, struct options op)
	tp->c_cc[VTIME] = 0;

	/* Optionally enable hardware flow control */
-
-	#ifdef CRTSCTS
+	#ifdef CRTSCTS
	if (op->flags & F_RTSCTS)
	tp->c_cflag \|= CRTSCTS;
	#endif

	ioctl(0, TCSETS, tp);

-	/* go to blocking input even in local mode */
-	ndelay_off(0);
-
	debug("term_io 2\n");
	}

@@ -393,26 +332,24 @@ static void auto_baud(char buf, unsigned size_buf, struct termios tp)
	* Use 7-bit characters, don't block if input queue is empty. Errors will
	* be dealt with later on.
	*/
-
	iflag = tp->c_iflag;
	tp->c_iflag \|= ISTRIP; /* enable 8th-bit stripping */
	vmin = tp->c_cc[VMIN];
-	tp->c_cc[VMIN] = 0; /* don't block if queue empty */
+	tp->c_cc[VMIN] = 0; /* don't block if queue empty */
	ioctl(0, TCSETS, tp);

	/*
	* Wait for a while, then read everything the modem has said so far and
	* try to extract the speed of the dial-in call.
	*/
-
	sleep(1);
-	nread = read(0, buf, size_buf - 1);
+	nread = safe_read(0, buf, size_buf - 1);
	if (nread > 0) {
	buf[nread] = '\0';
	for (bp = buf; bp < buf + nread; bp++) {
-	if (isascii(bp) && isdigit(bp)) {
+	if (isdigit(*bp)) {
	speed = bcode(bp);
-	if (speed) {
+	if (speed > 0) {
	tp->c_cflag &= ~CBAUD;
	tp->c_cflag \|= speed;
	}
@@ -420,25 +357,13 @@ static void auto_baud(char buf, unsigned size_buf, struct termios tp)
	}
	}
	}
-	/* Restore terminal settings. Errors will be dealt with later on. */

+	/* Restore terminal settings. Errors will be dealt with later on. */
	tp->c_iflag = iflag;
	tp->c_cc[VMIN] = vmin;
	ioctl(0, TCSETS, tp);
	}

-	/* next_speed - select next baud rate */
-	static void next_speed(struct termios tp, struct options op)
-	{
-	static int baud_index = FIRST_SPEED; /* current speed index */
-
-	baud_index = (baud_index + 1) % op->numspeed;
-	tp->c_cflag &= ~CBAUD;
-	tp->c_cflag \|= op->speeds[baud_index];
-	ioctl(0, TCSETS, tp);
-	}
-
-
	/* do_prompt - show login prompt, optionally preceded by /etc/issue contents */
	static void do_prompt(struct options op, struct termios tp)
	{
@@ -449,9 +374,9 @@ static void do_prompt(struct options op, struct termios tp)
	}

	#ifdef HANDLE_ALLCAPS
-	/* caps_lock - string contains upper case without lower case */
+	/* all_is_upcase - string contains upper case without lower case */
	/* returns 1 if true, 0 if false */
-	static int caps_lock(const char *s)
+	static int all_is_upcase(const char *s)
	{
	while (*s)
	if (islower(*s++))
@@ -460,8 +385,8 @@ static int caps_lock(const char *s)
	}
	#endif

-	/* get_logname - get user name, establish parity, speed, erase, kill, eol */
-	/* return NULL on failure, logname on success */
+	/* get_logname - get user name, establish parity, speed, erase, kill, eol;
+	* return NULL on BREAK, logname on success */
	static char get_logname(char logname, unsigned size_logname,
	struct options op, struct chardata cp, struct termios *tp)
	{
@@ -477,26 +402,19 @@ static char get_logname(char logname, unsigned size_logname,
	"\210\240\210", /* no parity */
	};

-	/* Initialize kill, erase, parity etc. (also after switching speeds). */
-
-	*cp = init_chardata;
+	/* NB: cp is pre-initialized with init_chardata /

	/* Flush pending input (esp. after parsing or switching the baud rate). */
-
	sleep(1);
	ioctl(0, TCFLSH, TCIFLUSH);

	/* Prompt for and read a login name. */
-
	logname[0] = '\0';
	while (!logname[0]) {
-
	/* Write issue file and prompt, with "parity" bit == 0. */
-
	do_prompt(op, tp);

	/* Read name, watch for break, parity, erase, kill, end-of-line. */
-
	bp = logname;
	cp->eol = '\0';
	while (cp->eol == '\0') {
@@ -508,7 +426,8 @@ static char get_logname(char logname, unsigned size_logname,
	bb_perror_msg_and_die("%s: read", op->tty);
	}

-	/* Do BREAK handling elsewhere. */
+	/* BREAK. If we have speeds to try,
+	* return NULL (will switch speeds and return here) */
	if (c == '\0' && op->numspeed > 1)
	return NULL;

@@ -535,18 +454,22 @@ static char get_logname(char logname, unsigned size_logname,
	break;
	case BS:
	case DEL:
+	#ifdef ANCIENT_BS_KILL_CHARS
	case '#':
+	#endif
	cp->erase = ascval; /* set erase character */
	if (bp > logname) {
-	write(1, erase[cp->parity], 3);
+	full_write(1, erase[cp->parity], 3);
	bp--;
	}
	break;
	case CTL('U'):
+	#ifdef ANCIENT_BS_KILL_CHARS
	case '@':
+	#endif
	cp->kill = ascval; /* set kill character */
	while (bp > logname) {
-	write(1, erase[cp->parity], 3);
+	full_write(1, erase[cp->parity], 3);
	bp--;
	}
	break;
@@ -558,7 +481,7 @@ static char get_logname(char logname, unsigned size_logname,
	} else if (bp - logname >= size_logname - 1) {
	bb_error_msg_and_die("%s: input overrun", op->tty);
	} else {
-	write(1, &c, 1); /* echo the character */
+	full_write(1, &c, 1); /* echo the character */
	bp++ = ascval; / and store it */
	}
	break;
@@ -568,7 +491,7 @@ static char get_logname(char logname, unsigned size_logname,
	/* Handle names with upper case and no lower case. */

	#ifdef HANDLE_ALLCAPS
-	cp->capslock = caps_lock(logname);
+	cp->capslock = all_is_upcase(logname);
	if (cp->capslock) {
	for (bp = logname; *bp; bp++)
	if (isupper(*bp))
@@ -641,7 +564,6 @@ static void termios_final(struct options op, struct termios tp, struct chardat
	ioctl_or_perror_and_die(0, TCSETS, tp, "%s: TCSETS", op->tty);
	}

-
	#ifdef SYSV_STYLE
	#if ENABLE_FEATURE_UTMP
	/* update_utmp - update our utmp entry */
@@ -666,17 +588,16 @@ static void update_utmp(const char *line)
	utmpname(_PATH_UTMP);
	setutent();
	while ((utp = getutent())
-	&& !(utp->ut_type == INIT_PROCESS && utp->ut_pid == mypid))
-	/* nothing */;
+	&& !(utp->ut_type == INIT_PROCESS && utp->ut_pid == mypid)
+	) {
+	continue;
+	}

-	if (utp) {
+	/* some inits don't initialize utmp... */
+	memset(&ut, 0, sizeof(ut));
+	safe_strncpy(ut.ut_id, line + 3, sizeof(ut.ut_id));
+	if (utp)
	memcpy(&ut, utp, sizeof(ut));
-	} else {
-	/* some inits don't initialize utmp... */
-	memset(&ut, 0, sizeof(ut));
-	safe_strncpy(ut.ut_id, line + 3, sizeof(ut.ut_id));
-	}
-	/* endutent(); */

	strcpy(ut.ut_user, "LOGIN");
	safe_strncpy(ut.ut_line, line, sizeof(ut.ut_line));
@@ -700,42 +621,43 @@ static void update_utmp(const char *line)
	#endif /* CONFIG_FEATURE_UTMP */
	#endif /* SYSV_STYLE */

-
	int getty_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
	int getty_main(int argc, char **argv)
	{
-	int nullfd;
-	char logname = NULL; / login name, given to /bin/login */
+	int n;
+	char logname; / login name, given to /bin/login */
	/* Merging these into "struct local" may _seem_ to reduce
	* parameter passing, but today's gcc will inline
	* statics which are called once anyway, so don't do that */
	struct chardata chardata; /* set by get_logname() */
-	struct termios termios; /* terminal mode bits */
-	struct options options = {
-	0, /* show /etc/issue (SYSV_STYLE) */
-	0, /* no timeout */
-	_PATH_LOGIN, /* default login program */
-	"tty1", /* default tty line */
-	"", /* modem init string */
+	struct termios termios; /* terminal mode bits */
+	struct options options;
+
+	memset(&options, 0, sizeof(options));
+	options.login = _PATH_LOGIN; /* default login program */
+	options.tty = "tty1"; /* default tty line */
+	options.initstring = ""; /* modem init string */
	#ifdef ISSUE
-	ISSUE, /* default issue file */
-	#else
-	NULL,
+	options.issue = ISSUE; /* default issue file */
	#endif
-	0, /* no baud rates known yet */
-	};

	/* Already too late because of theoretical
	* possibility of getty --help somehow triggered
	* inadvertently before we reach this. Oh well. */
	logmode = LOGMODE_NONE;
+
+	/* Create new session, lose controlling tty, if any */
+	/* docs/ctty.htm says:
+	* "This is allowed only when the current process
+	* is not a process group leader" - is this a problem? */
	setsid();
-	nullfd = xopen(bb_dev_null, O_RDWR);
-	/* dup2(nullfd, 0); - no, because of possible "getty - 9600" */
-	/* open_tty() will take care of fd# 0 anyway */
-	dup2(nullfd, 1);
-	dup2(nullfd, 2);
-	while (nullfd > 2) close(nullfd--);
+
+	n = xopen(bb_dev_null, O_RDWR);
+	/* dup2(n, 0); - no, because of possible "getty - 9600" */
+	dup2(n, 1);
+	dup2(n, 2);
+	while (n > 2)
+	close(n--);
	/* We want special flavor of error_msg_and_die */
	die_sleep = 10;
	msg_eol = "\r\n";
@@ -744,69 +666,74 @@ int getty_main(int argc, char **argv)

	#ifdef DEBUGGING
	dbf = xfopen(DEBUGTERM, "w");
-
-	{
-	int i;
-
-	for (i = 1; i < argc; i++) {
-	debug(argv[i]);
-	debug("\n");
-	}
+	for (n = 1; n < argc; n++) {
+	debug(argv[n]);
+	debug("\n");
	}
	#endif

	/* Parse command-line arguments. */
-	parse_args(argc, argv, &options);
+	parse_args(argv, &options);
+
+	debug("calling open_tty\n");
+	/* Open the tty as standard input, if it is not "-" */
+	open_tty(options.tty);
+
+	debug("duping\n");
+	ndelay_off(0);
+	xdup2(0, 1);
+	xdup2(0, 2);
+
+	/*
+	* The following ioctl will fail if stdin is not a tty, but also when
+	* there is noise on the modem control lines. In the latter case, the
+	* common course of action is (1) fix your cables (2) give the modem more
+	* time to properly reset after hanging up. SunOS users can achieve (2)
+	* by patching the SunOS kernel variable "zsadtrlow" to a larger value;
+	* 5 seconds seems to be a good value.
+	*/
+	ioctl_or_perror_and_die(0, TCGETS, &termios, "%s: TCGETS", options.tty);

	#ifdef SYSV_STYLE
	#if ENABLE_FEATURE_UTMP
-	/* Update the utmp file. */
+	/* Update the utmp file */
	update_utmp(options.tty);
	#endif
	#endif

-	debug("calling open_tty\n");
-	/* Open the tty as standard { input, output, error }. */
-	open_tty(options.tty, &termios, options.flags & F_LOCAL);
-
	#ifdef __linux__
-	{
-	int iv;
-
-	iv = getpid();
-	ioctl(0, TIOCSPGRP, &iv);
-	}
+	/* Make ourself a foreground process group within our session */
+	tcsetpgrp(0, getpid());
+	// /* Forcibly make fd 0 our controlling tty, even if another session
+	// * has it as a ctty. (Another session loses ctty). */
+	// ioctl(0, TIOCSCTTY, (void*)1);
	#endif
+
	/* Initialize the termios settings (raw mode, eight-bit, blocking i/o). */
	debug("calling termios_init\n");
-	termios_init(&termios, options.speeds[FIRST_SPEED], &options);
+	termios_init(&termios, options.speeds[0], &options);

-	/* write the modem init string and DON'T flush the buffers */
+	/* Write the modem init string and DON'T flush the buffers */
	if (options.flags & F_INITSTRING) {
	debug("writing init string\n");
-	write(1, options.initstring, strlen(options.initstring));
-	}
-
-	if (!(options.flags & F_LOCAL)) {
-	/* go to blocking write mode unless -L is specified */
-	ndelay_off(1);
+	full_write(1, options.initstring, strlen(options.initstring));
	}

-	/* Optionally detect the baud rate from the modem status message. */
+	/* Optionally detect the baud rate from the modem status message */
	debug("before autobaud\n");
	if (options.flags & F_PARSE)
-	auto_baud(bb_common_bufsiz1, sizeof(bb_common_bufsiz1), &termios);
+	auto_baud(line_buf, sizeof(line_buf), &termios);

-	/* Set the optional timer. */
+	/* Set the optional timer */
	if (options.timeout)
	alarm(options.timeout);

-	/* optionally wait for CR or LF before writing /etc/issue */
+	/* Optionally wait for CR or LF before writing /etc/issue */
	if (options.flags & F_WAITCRLF) {
	char ch;

	debug("waiting for cr-lf\n");
-	while (read(0, &ch, 1) == 1) {
+	while (safe_read(0, &ch, 1) == 1) {
	ch &= 0x7f; /* strip "parity bit" */
	#ifdef DEBUGGING
	fprintf(dbf, "read %c\n", ch);
@@ -816,31 +743,42 @@ int getty_main(int argc, char **argv)
	}
	}

+	logname = NULL;
	chardata = init_chardata;
	if (!(options.flags & F_NOPROMPT)) {
-	/* Read the login name. */
-	debug("reading login name\n");
-	logname = get_logname(bb_common_bufsiz1, sizeof(bb_common_bufsiz1),
+	/* NB:termios_init already set line speed
+	* to options.speeds[0] */
+	int baud_index = 0;
+
+	while (1) {
+	/* Read the login name. */
+	debug("reading login name\n");
+	logname = get_logname(line_buf, sizeof(line_buf),
	&options, &chardata, &termios);
-	while (logname == NULL)
-	next_speed(&termios, &options);
+	if (logname)
+	break;
+	/* we are here only if options.numspeed > 1 */
+	baud_index = (baud_index + 1) % options.numspeed;
+	termios.c_cflag &= ~CBAUD;
+	termios.c_cflag \|= options.speeds[baud_index];
+	ioctl(0, TCSETS, &termios);
+	}
	}

	/* Disable timer. */
-
	if (options.timeout)
	alarm(0);

	/* Finalize the termios settings. */
-
	termios_final(&options, &termios, &chardata);

	/* Now the newline character should be properly written. */
-
-	write(1, "\n", 1);
+	full_write(1, "\n", 1);

	/* Let the login program take care of password validation. */
-
-	execl(options.login, options.login, "--", logname, (char *) 0);
+	/* We use PATH because we trust that root doesn't set "bad" PATH,
+	* and getty is not suid-root applet. */
+	/* Hmm... with -n, logname == NULL! Is it ok? */
+	BB_EXECLP(options.login, options.login, "--", logname, NULL);
	bb_error_msg_and_die("%s: can't exec %s", options.tty, options.login);
	}