Add oneit.

1 files changed, 45 insertions, 0 deletions

diff --git a/toys/oneit.c b/toys/oneit.c
new file mode 100644
index 00000000..1f87e5f2
--- /dev/null
+++ b/toys/oneit.c
@@ -0,0 +1,45 @@
+/* oneit.c, tiny one-process init replacement.
+ *
+ * Copyright 2005 by Rob Landley <rob@landley.net>.
+ */
+
+#include "toys.h"
+#include <sys/reboot.h>
+
+// 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.
+
+int 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();
+    reboot(toys.optflags ? RB_POWER_OFF : RB_AUTOBOOT);
+  }
+    
+  // Redirect stdio to /dev/tty0, with new session ID, so ctrl-c works.
+  setsid();
+  for (i=0; i<3; i++) {
+    close(i);
+    open("/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);
+}