#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs_struct.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/reboot.h>
#include <linux/delay.h>
#include <linux/proc_fs.h>
#include <asm/uaccess.h>
#include <linux/sysrq.h>
#include <linux/timer.h>
#include <linux/time.h>
#include <linux/lglock.h>
#include <linux/init.h>
#include <linux/idr.h>
#include <linux/namei.h>
#include <linux/bitops.h>
#include <linux/mnt_namespace.h>
#include <linux/path.h>
#include <linux/dcache.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/kprobes.h>
#include <linux/kallsyms.h>
#include <linux/nsproxy.h>
#include "mount.h"

#define VERSION_STR "0.0.1"

#ifndef CONFIG_X86_64
#error "This code does not support your architecture"
#endif

MODULE_AUTHOR("Sapan Bhatia <sapanb@cs.princeton.edu>");
MODULE_DESCRIPTION("Hack to enable mount namespace switching via setns. Based on a patch by Eric Biederman.");
MODULE_LICENSE("GPL");
MODULE_VERSION(VERSION_STR);

static int setns_entry(struct kretprobe_instance *ri, struct pt_regs *regs) {
	int nstype = regs->si;
    printk(KERN_CRIT "nstype: %d",nstype);

    if (nstype==666) regs->si = 0;
	return 0;
}

static int setns_ret(struct kretprobe_instance *ri, struct pt_regs *regs)
{
    int nstype = regs->si;
    printk(KERN_CRIT "nstype 2: %d",nstype);
	
	return 0;
}

static struct kretprobe setns_probe = {
	.entry_handler = (kprobe_opcode_t *) setns_entry,
        .handler = (kprobe_opcode_t *) setns_ret,
	.maxactive = 20,
	.data_size = 0
};

static void __exit mntsu_exit(void)
{
	unregister_kretprobe(&setns_probe);
	printk("Procprotect: Stopped mntsu.\n");
}

static int __init mntsu_init(void)
{
		int ret=0;
printk("Mntsu: starting mntsu version %s.\n",
	       VERSION_STR);

          setns_probe.kp.addr = 
                  (kprobe_opcode_t *) kallsyms_lookup_name("sys_setns");
          if (!setns_probe.kp.addr) {
                  printk("Couldn't find %s to plant kretprobe\n", "do_execve");
                  return -1;
          }
  
          if ((ret = register_kretprobe(&setns_probe)) <0) {
                  printk("register_kretprobe failed, returned %d\n", ret);
                  return -1;
          }
          printk("Planted kretprobe at %p, handler addr %p\n",
                 setns_probe.kp.addr, setns_probe.handler);

        return ret;
}

static void *mntns_get(struct task_struct *task)
{
       struct mnt_namespace *ns;
       rcu_read_lock();
       ns = task->nsproxy->mnt_ns;
       atomic_inc(&ns->count);
       rcu_read_unlock();
       return ns;
}

static void mntns_put(void *ns)
{
       put_mnt_ns(ns);
}

static int mntns_install(struct nsproxy *nsproxy, void *ns)
{
       struct fs_struct *fs = current->fs;
       struct mnt_namespace *mnt_ns = ns;
       struct path root;

       if (fs->users != 1)
               return -EINVAL;

       atomic_inc(&mnt_ns->count);
       put_mnt_ns(nsproxy->mnt_ns);
       nsproxy->mnt_ns = mnt_ns;

       /* Find the root */
       root.mnt    = mnt_ns->root;
       root.dentry = mnt_ns->root->mnt.mnt_root;
       path_get(&root);
       while(d_mountpoint(root.dentry) && follow_down(&root))
               ;

       /* Update the pwd and root */
       path_get(&root);
       path_get(&root);
       path_put(&fs->root);
       path_put(&fs->pwd);
       fs->root = root;
       fs->pwd  = root;
       path_put(&root);

       return 0;
}

const struct proc_ns_operations mntns_operations = {
       .name           = "mnt_ns",
       .get            = mntns_get,
       .put            = mntns_put,
       .install        = mntns_install,
};

module_init(mntsu_init);
module_exit(mntsu_exit);