1 files changed, 115 insertions, 0 deletions
diff --git a/user/init.c b/user/init.c
new file mode 100644
index 0000000..51d8f92
--- /dev/null
+++ b/user/init.c
@@ -0,0 +1,115 @@
+#include <stdio.h>
+#include <unistd.h>
+
+#define MAX_ARGS 4
+
+static long running = 0;
+
+struct proc {
+	pid_t pid;
+	const char *filename;
+	const char *args[MAX_ARGS];
+};
+
+static struct proc spawn_table[] = {
+	// apple
+	{ 0, "bin/apple", { NULL } },
+	// end,
+	{ 0, NULL, { NULL } },
+};
+
+static int spawn(const char *filename, const char **args)
+{
+	int ret;
+
+	// fork init
+	if ((ret = fork()) != 0)
+		return ret;
+
+	// call exec
+	if ((ret = exec(filename, args)))
+		exit(ret);
+
+	// should not happen!
+	exit(1);
+}
+
+static void spawn_proc(struct proc *proc)
+{
+	int ret;
+
+	// update running on respawn
+	if (proc->pid)
+		running--;
+
+	// attempt to fork / exec
+	ret = spawn(proc->filename, proc->args);
+
+	// handle result
+	if (ret < 0) {
+		printf("init: cannot exec '%s': %d\n", proc->filename, ret);
+		proc->pid = 0;
+	} else {
+		running++;
+		proc->pid = ret;
+	}
+}
+
+static void spawn_proc_loop(struct proc *proc)
+{
+	while (proc->pid == 0)
+		spawn_proc(proc);
+}
+
+static void spawn_all(void)
+{
+	struct proc *proc;
+	for (proc = spawn_table; proc->filename != NULL; proc++) {
+		spawn_proc_loop(proc);
+	}
+}
+
+static struct proc *get_proc(pid_t pid)
+{
+	struct proc *proc;
+	for (proc = spawn_table; proc->filename != NULL; proc++) {
+		if (proc->pid == pid)
+			return proc;
+	}
+	return NULL;
+}
+
+int main(void)
+{
+	// spawn our processes
+	spawn_all();
+
+	// clean up dead on restart ours
+	while (1) {
+		struct proc *proc;
+		int pid, status;
+
+		// dont wait if nothing running
+		if (running) {
+			pid = waitpid(0, &status);
+			// ???
+			if (pid < 0)
+				continue;
+		} else {
+			spawn_all();
+			continue;
+		}
+
+		printf("init: pid %d exited with %d\n", pid, status);
+
+		// figure out if this is one of ours
+		proc = get_proc(pid);
+		if (proc == NULL)
+			continue;
+
+		spawn_proc_loop(proc);
+	}
+
+	// failed to launch anythingvery very bad!
+	return 1;
+}