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+/* vi: set sw=4 ts=4:
+ *
+ * oneit.c, tiny one-process init replacement.
+ *
+ * Copyright 2005, 2007 by Rob Landley <rob@landley.net>.
+ *
+ * Not in SUSv3.
+
+USE_ONEIT(NEWTOY(oneit, "^<1c:p", TOYFLAG_SBIN))
+
+config ONEIT
+ bool "oneit"
+ default y
+ help
+ usage: oneit [-p] [-c /dev/tty0] command [...]
+
+ A simple init program that runs a single supplied command line with a
+ controlling tty (so CTRL-C can kill it).
+
+ -p Power off instead of rebooting when command exits.
+ -c Which console device to use.
+
+ The oneit command runs the supplied command line as a child process
+ (because PID 1 has signals blocked), attached to /dev/tty0, in its
+ own session. Then oneit reaps zombies until the child exits, at
+ which point it reboots (or with -p, powers off) the system.
+*/
+
+#include "toys.h"
+#include <sys/reboot.h>
+
+DEFINE_GLOBALS(
+ char *console;
+)
+
+#define TT this.oneit
+
+// The minimum amount of work necessary to get ctrl-c and such to work is:
+//
+// - Fork a child (PID 1 is special: can't exit, has various signals blocked).
+// - Do a setsid() (so we have our own session).
+// - In the child, attach stdio to /dev/tty0 (/dev/console is special)
+// - Exec the rest of the command line.
+//
+// PID 1 then reaps zombies until the child process it spawned exits, at which
+// point it calls sync() and reboot(). I could stick a kill -1 in there.
+
+
+void oneit_main(void)
+{
+ int i;
+ pid_t pid;
+
+ // Create a new child process.
+ pid = vfork();
+ if (pid) {
+
+ // pid 1 just reaps zombies until it gets its child, then halts the system.
+ while (pid!=wait(&i));
+ sync();
+
+ // PID 1 can't call reboot() because it kills the task that calls it,
+ // which causes the kernel to panic before the actual reboot happens.
+ if (!vfork()) reboot((toys.optflags&1) ? RB_POWER_OFF : RB_AUTOBOOT);
+ sleep(5);
+ _exit(1);
+ }
+
+ // Redirect stdio to /dev/tty0, with new session ID, so ctrl-c works.
+ setsid();
+ for (i=0; i<3; i++) {
+ close(i);
+ xopen(TT.console ? TT.console : "/dev/tty0",O_RDWR);
+ }
+
+ // Can't xexec() here, because we vforked so we don't want to error_exit().
+ toy_exec(toys.optargs);
+ execvp(*toys.optargs, toys.optargs);
+ _exit(127);
+}