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+ <!-- 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>
#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 */
/* I doubt there are systems which still need this */
#undef HANDLE_ALLCAPS
+#undef ANCIENT_BS_KILL_CHARS
#define _PATH_LOGIN "/bin/login"
* 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 */
#endif
};
+
/* Initial values for the above. */
static const struct chardata init_chardata = {
DEF_ERASE, /* default erase character */
#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"
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);
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;
}
*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);
/* 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
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 */
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");
}
* 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;
}
}
}
}
- /* 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)
{
}
#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++))
}
#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)
{
"\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') {
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;
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;
} 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;
/* 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))
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 */
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));
#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";
#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);
}
}
+ 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);
}
projects / oweals / busybox.git / commitdiff