From c63f340d90800895f007de64b7d2d14624263331 Mon Sep 17 00:00:00 2001
From: nthnluu <nate1299@me.com>
Date: Sun, 28 Jan 2024 21:20:27 -0500
Subject: Created student weenix repository

---
 user/sbin/init.c | 115 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 user/sbin/init.c

(limited to 'user/sbin/init.c')

diff --git a/user/sbin/init.c b/user/sbin/init.c
new file mode 100644
index 0000000..6bfe6ae
--- /dev/null
+++ b/user/sbin/init.c
@@ -0,0 +1,115 @@
+/*
+ * Forks a shell for each terminal and waits for them.
+ * This is the final thing you should be executing
+ * (with kernel_execve) in kernel-land once everything works.
+ */
+
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+char *empty[] = {NULL};
+
+const char *hi = "init: starting shell on ";
+const char *sh = "/bin/sh";
+const char *ttystr = "tty";
+const char *home = "/";
+const char *alldone = "init: no remaining processes\n";
+
+static int open_tty(char *tty)
+{
+    if (-1 == open(tty, O_RDONLY, 0))
+    {
+        return -1;
+    }
+    else if (-1 == open(tty, O_WRONLY, 0))
+    {
+        return -1;
+    }
+    else if (2 != dup(1))
+    {
+        return -1;
+    }
+    else
+    {
+        return 0;
+    }
+}
+
+static int canary = 0x12345678;
+
+static void spawn_shell_on(char *tty)
+{
+    if (!fork())
+    {
+        close(0);
+        close(1);
+        close(2);
+        if (-1 == open_tty(tty))
+        {
+            exit(1);
+        }
+
+        chdir(home);
+
+        printf("%s%s\n", hi, tty);
+
+        execve(sh, empty, empty);
+        fprintf(stderr, "exec failed!\n");
+    }
+}
+
+int main(int argc, char **argv, char **envp)
+{
+    int devdir, ii;
+    dirent_t d;
+    int status;
+
+    for (ii = 0; ii < NFILES; ii++)
+    {
+        close(ii);
+    }
+    ii = ii;
+
+    if (-1 == open_tty("/dev/tty0"))
+    {
+        exit(1);
+    }
+
+    chdir("/dev");
+
+    devdir = open("/dev", O_RDONLY, 0);
+    while (getdents(devdir, &d, sizeof(d)) > 0)
+    {
+        if (0 == strncmp(d.d_name, ttystr, strlen(ttystr)))
+        {
+            spawn_shell_on(d.d_name);
+        }
+    }
+    close(devdir);
+
+    int pid;
+    while (0 <= (pid = wait(&status)))
+    {
+        if (EFAULT == status)
+        {
+            printf("process %i faulted\n", pid);
+        }
+    }
+
+    if (ECHILD != errno)
+    {
+        printf("error: wait: %s\n", strerror(errno));
+        return 1;
+    }
+    else
+    {
+        printf("%s", alldone);
+        return 0;
+    }
+}
-- 
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