Minix2.0/src/tools/init.c
/* This process is the father (mother) of all Minix user processes. When
* Minix comes up, this is process number 2, and has a pid of 1. It
* executes the /etc/rc shell file, and then reads the /etc/ttytab file to
* determine which terminals need a login process.
*
* If the files /usr/adm/wtmp and /etc/utmp exist and are writable, init
* (with help from login) will maintain login accounting. Sending a
* signal 1 (SIGHUP) to init will cause it to rescan /etc/ttytab and start
* up new shell processes if necessary. It will not, however, kill off
* login processes for lines that have been turned off; do this manually.
* Signal 15 (SIGTERM) makes init stop spawning new processes, this is
* used by shutdown and friends when they are about to close the system
* down.
*/
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <ttyent.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <signal.h>
#include <string.h>
#include <time.h>
#include <stdlib.h>
#include <unistd.h>
#include <utmp.h>
/* Command to execute as a response to the three finger salute. */
char *REBOOT_CMD[] = { "shutdown", "now", "CTRL-ALT-DEL", NULL };
/* Associated fake ttytab entry. */
struct ttyent TT_REBOOT = { "console", "-", REBOOT_CMD, NULL };
char PATH_UTMP[] = "/etc/utmp"; /* current logins */
char PATH_WTMP[] = "/usr/adm/wtmp"; /* login/logout history */
#define PIDSLOTS 32 /* first this many ttys can be on */
struct slotent {
int errct; /* error count */
pid_t pid; /* pid of login process for this tty line */
};
#define ERRCT_DISABLE 10 /* disable after this many errors */
#define NO_PID 0 /* pid value indicating no process */
struct slotent slots[PIDSLOTS]; /* init table of ttys and pids */
int gothup = 0; /* flag, showing signal 1 was received */
int gotabrt = 0; /* flag, showing signal 6 was received */
int spawn = 1; /* flag, spawn processes only when set */
void tell(int fd, char *s);
void report(int fd, char *label);
void wtmp(int type, int linenr, char *line, pid_t pid);
void startup(int linenr, struct ttyent *ttyp);
int execute(char **cmd);
void onhup(int sig);
void onterm(int sig);
void onabrt(int sig);
int main(void)
{
pid_t pid; /* pid of child process */
int fd; /* generally useful */
int linenr; /* loop variable */
int check; /* check if a new process must be spawned */
struct slotent *slotp; /* slots[] pointer */
struct ttyent *ttyp; /* ttytab entry */
struct sigaction sa;
struct stat stb;
if (fstat(0, &stb) < 0) {
/* Open standard input, output & error. */
(void) open("/dev/null", O_RDONLY);
(void) open("/dev/log", O_WRONLY);
dup(1);
}
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
/* Hangup: Reexamine /etc/ttytab for newly enabled terminal lines. */
sa.sa_handler = onhup;
sigaction(SIGHUP, &sa, NULL);
/* Terminate: Stop spawning login processes, shutdown is near. */
sa.sa_handler = onterm;
sigaction(SIGTERM, &sa, NULL);
/* Abort: Sent by the kernel on CTRL-ALT-DEL; shut the system down. */
sa.sa_handler = onabrt;
sigaction(SIGABRT, &sa, NULL);
/* Execute the /etc/rc file. */
if ((pid = fork()) != 0) {
/* Parent just waits. */
while (wait(NULL) != pid) {
if (gotabrt) reboot(RBT_HALT);
}
} else {
static char *rc_command[] = { "sh", "/etc/rc", NULL, NULL };
#if __minix_vmd
/* Minix-vmd: Get the boot options from the boot environment. */
rc_command[2] = getenv("bootopts");
#else
/* Minix: Input from the console. */
close(0);
(void) open("/dev/console", O_RDONLY);
#endif
execute(rc_command);
report(2, "sh /etc/rc");
_exit(1); /* impossible, we hope */
}
/* Clear /etc/utmp if it exists. */
if ((fd = open(PATH_UTMP, O_WRONLY | O_TRUNC)) >= 0) close(fd);
/* Log system reboot. */
wtmp(BOOT_TIME, 0, NULL, 0);
/* Main loop. If login processes have already been started up, wait for one
* to terminate, or for a HUP signal to arrive. Start up new login processes
* for all ttys which don't have them. Note that wait() also returns when
* somebody's orphan dies, in which case ignore it. If the TERM signal is
* sent then stop spawning processes, shutdown time is near.
*/
check = 1;
while (1) {
while ((pid = waitpid(-1, NULL, check ? WNOHANG : 0)) > 0) {
/* Search to see which line terminated. */
for (linenr = 0; linenr < PIDSLOTS; linenr++) {
slotp = &slots[linenr];
if (slotp->pid == pid) {
/* Record process exiting. */
wtmp(DEAD_PROCESS, linenr, NULL, pid);
slotp->pid = NO_PID;
check = 1;
}
}
}
/* If a signal 1 (SIGHUP) is received, simply reset error counts. */
if (gothup) {
gothup = 0;
for (linenr = 0; linenr < PIDSLOTS; linenr++) {
slots[linenr].errct = 0;
}
check = 1;
}
/* Shut down on signal 6 (SIGABRT). */
if (gotabrt) {
gotabrt = 0;
startup(0, &TT_REBOOT);
}
if (spawn && check) {
/* See which lines need a login process started up. */
for (linenr = 0; linenr < PIDSLOTS; linenr++) {
slotp = &slots[linenr];
if ((ttyp = getttyent()) == NULL) break;
if (ttyp->ty_getty != NULL
&& ttyp->ty_getty[0] != NULL
&& slotp->pid == NO_PID
&& slotp->errct < ERRCT_DISABLE)
{
startup(linenr, ttyp);
}
}
endttyent();
}
check = 0;
}
}
void onhup(int sig)
{
gothup = 1;
spawn = 1;
}
void onterm(int sig)
{
spawn = 0;
}
void onabrt(int sig)
{
static int count;
if (++count == 2) reboot(RBT_HALT);
gotabrt = 1;
}
void startup(int linenr, struct ttyent *ttyp)
{
/* Fork off a process for the indicated line. */
struct slotent *slotp; /* pointer to ttyslot */
pid_t pid; /* new pid */
int err[2]; /* error reporting pipe */
char line[32]; /* tty device name */
int status;
slotp = &slots[linenr];
/* Error channel for between fork and exec. */
if (pipe(err) < 0) err[0] = err[1] = -1;
if ((pid = fork()) == -1 ) {
report(2, "fork()");
sleep(10);
return;
}
if (pid == 0) {
/* Child */
close(err[0]);
fcntl(err[1], F_SETFD, fcntl(err[1], F_GETFD) | FD_CLOEXEC);
/* A new session. */
setsid();
/* Construct device name. */
strcpy(line, "/dev/");
strncat(line, ttyp->ty_name, sizeof(line) - 6);
/* Open the line for standard input and output. */
close(0);
close(1);
if (open(line, O_RDWR) < 0 || dup(0) < 0) {
write(err[1], &errno, sizeof(errno));
_exit(1);
}
if (ttyp->ty_init != NULL && ttyp->ty_init[0] != NULL) {
/* Execute a command to initialize the terminal line. */
if ((pid = fork()) == -1) {
report(2, "fork()");
errno= 0;
write(err[1], &errno, sizeof(errno));
_exit(1);
}
if (pid == 0) {
alarm(10);
execute(ttyp->ty_init);
report(2, ttyp->ty_init[0]);
_exit(1);
}
while (waitpid(pid, &status, 0) != pid) {}
if (status != 0) {
tell(2, "init: ");
tell(2, ttyp->ty_name);
tell(2, ": ");
tell(2, ttyp->ty_init[0]);
tell(2, ": bad exit status\n");
errno = 0;
write(err[1], &errno, sizeof(errno));
_exit(1);
}
}
/* Redirect standard error too. */
dup2(0, 2);
/* Execute the getty process. */
execute(ttyp->ty_getty);
/* Oops, disaster strikes. */
fcntl(2, F_SETFL, fcntl(2, F_GETFL) | O_NONBLOCK);
if (linenr != 0) report(2, ttyp->ty_getty[0]);
write(err[1], &errno, sizeof(errno));
_exit(1);
}
/* Parent */
if (ttyp != &TT_REBOOT) slotp->pid = pid;
close(err[1]);
if (read(err[0], &errno, sizeof(errno)) != 0) {
/* If an errno value goes down the error pipe: Problems. */
switch (errno) {
case ENOENT:
case ENODEV:
case ENXIO:
/* Device nonexistent, no driver, or no minor device. */
slotp->errct = ERRCT_DISABLE;
close(err[0]);
return;
case 0:
/* Error already reported. */
break;
default:
/* Any other error on the line. */
report(2, ttyp->ty_name);
}
close(err[0]);
if (++slotp->errct >= ERRCT_DISABLE) {
tell(2, "init: ");
tell(2, ttyp->ty_name);
tell(2, ": excessive errors, shutting down\n");
} else {
sleep(5);
}
return;
}
close(err[0]);
if (ttyp != &TT_REBOOT) wtmp(LOGIN_PROCESS, linenr, ttyp->ty_name, pid);
slotp->errct = 0;
}
int execute(char **cmd)
{
/* Execute a command with a path search along /sbin:/bin:/usr/sbin:/usr/bin.
*/
static char *nullenv[] = { NULL };
char command[128];
char *path[] = { "/sbin", "/bin", "/usr/sbin", "/usr/bin" };
int i;
if (cmd[0][0] == '/') {
/* A full path. */
return execve(cmd[0], cmd, nullenv);
}
/* Path search. */
for (i = 0; i < 4; i++) {
if (strlen(path[i]) + 1 + strlen(cmd[0]) + 1 > sizeof(command)) {
errno= ENAMETOOLONG;
return -1;
}
strcpy(command, path[i]);
strcat(command, "/");
strcat(command, cmd[0]);
execve(command, cmd, nullenv);
if (errno != ENOENT) break;
}
return -1;
}
void wtmp(type, linenr, line, pid)
int type; /* type of entry */
int linenr; /* line number in ttytab */
char *line; /* tty name (only good on login) */
pid_t pid; /* pid of process */
{
/* Log an event into the UTMP and WTMP files. */
struct utmp utmp; /* UTMP/WTMP User Accounting */
int fd;
/* Clear the utmp record. */
memset((void *) &utmp, 0, sizeof(utmp));
/* Fill in utmp. */
switch (type) {
case BOOT_TIME:
/* Make a special reboot record. */
strcpy(utmp.ut_name, "reboot");
strcpy(utmp.ut_line, "~");
break;
case LOGIN_PROCESS:
/* A new login, fill in line name. */
strncpy(utmp.ut_line, line, sizeof(utmp.ut_line));
break;
case DEAD_PROCESS:
/* A logout. Use the current utmp entry, but make sure it is a
* user process exiting, and not getty or login giving up.
*/
if ((fd = open(PATH_UTMP, O_RDONLY)) < 0) {
if (errno != ENOENT) report(2, PATH_UTMP);
return;
}
if (lseek(fd, (off_t) (linenr+1) * sizeof(utmp), SEEK_SET) == -1
|| read(fd, &utmp, sizeof(utmp)) == -1
) {
report(2, PATH_UTMP);
close(fd);
return;
}
close(fd);
if (utmp.ut_type != USER_PROCESS) return;
strncpy(utmp.ut_name, "", sizeof(utmp.ut_name));
break;
}
/* Finish new utmp entry. */
utmp.ut_pid = pid;
utmp.ut_type = type;
utmp.ut_time = time((time_t *) 0);
switch (type) {
case LOGIN_PROCESS:
case DEAD_PROCESS:
/* Write new entry to utmp. */
if ((fd = open(PATH_UTMP, O_WRONLY)) < 0
|| lseek(fd, (off_t) (linenr+1) * sizeof(utmp), SEEK_SET) == -1
|| write(fd, &utmp, sizeof(utmp)) == -1
) {
if (errno != ENOENT) report(2, PATH_UTMP);
}
if (fd != -1) close(fd);
break;
}
switch (type) {
case BOOT_TIME:
case DEAD_PROCESS:
/* Add new wtmp entry. */
if ((fd = open(PATH_WTMP, O_WRONLY | O_APPEND)) < 0
|| write(fd, &utmp, sizeof(utmp)) == -1
) {
if (errno != ENOENT) report(2, PATH_WTMP);
}
if (fd != -1) close(fd);
break;
}
}
void tell(fd, s)
int fd;
char *s;
{
write(fd, s, strlen(s));
}
void report(fd, label)
int fd;
char *label;
{
int err = errno;
tell(fd, "init: ");
tell(fd, label);
tell(fd, ": ");
tell(fd, strerror(err));
tell(fd, "\n");
errno= err;
}