#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/pid_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/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 pid namespace switching via setns. Based on a patch by Eric Biederman.");
MODULE_LICENSE("GPL");
MODULE_VERSION(VERSION_STR);

struct proc_dir_entry *proc_entry;

/*
 * Pid namespaces
 *
 * Authors:
 *    (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
 *    (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
 *     Many thanks to Oleg Nesterov for comments and help
 *
 */

#define BITS_PER_PAGE       (PAGE_SIZE*8)

void (*free_nsproxy2)(struct nsproxy *ns);
struct nsproxy * (*create_new_namespaces)(unsigned long flags,
			struct task_struct *tsk, struct fs_struct *new_fs);

void (*switch_task_namespaces2)(struct task_struct *p, struct nsproxy *new);
void (*free_pid_ns2)(struct kref *kref);


struct pid_cache {
    int nr_ids;
    char name[16];
    struct kmem_cache *cachep;
    struct list_head list;
};

static LIST_HEAD(pid_caches_lh);
static DEFINE_MUTEX(pid_caches_mutex);

static void *pidns_get(struct task_struct *task)
{
    struct pid_namespace *ns;

    rcu_read_lock();
    ns = get_pid_ns(task_active_pid_ns(task));
    rcu_read_unlock();

    return ns;
}

static void pidns_put(void *ns)
{
    struct pid_namespace *pidns = ns;
    if (pidns != &init_pid_ns)
        kref_put(&pidns->kref, free_pid_ns2);
}

static int pidns_install(struct nsproxy *nsproxy, void *ns)
{
    //printk(KERN_CRIT "Entering pid ns");
    pidns_put(nsproxy->pid_ns);
    nsproxy->pid_ns = get_pid_ns(ns);
    return 0;
}

const struct proc_ns_operations pidns_operations = {
    .name       = "pid",
    .type       = CLONE_NEWPID,
    .get        = pidns_get,
    .put        = pidns_put,
    .install    = pidns_install,
};

static int setns(struct task_struct *reftask) {
        const struct proc_ns_operations *ops;
        struct task_struct *tsk = current;
        struct nsproxy *new_nsproxy;
        int err;

        if (!capable(CAP_SYS_ADMIN))
            return -EPERM;

        err = -EINVAL;
        ops = &pidns_operations;

        new_nsproxy = (*create_new_namespaces)(0, tsk, tsk->fs);
        if (IS_ERR(new_nsproxy)) {
            err = PTR_ERR(new_nsproxy);
            goto out;
        }

        err = ops->install(new_nsproxy, reftask->nsproxy->pid_ns);
        if (err) {
            (*free_nsproxy2)(new_nsproxy);
            goto out;
        }
        (*switch_task_namespaces2)(tsk, new_nsproxy);
        return 0;
out:
        return err;

}

static void __exit pidsu_exit(void)
{
	remove_proc_entry("pidsu",NULL);
	printk("Procprotect: Stopped pidsu.\n");
}

int pidsu_write(struct file *file, const char *buffer, unsigned long count, void *data) {
	char pidname[80];
    int pid;
    struct pid *p;
    char **s;
    struct task_struct *task;

	if (current->nsproxy->pid_ns!=init_task.nsproxy->pid_ns)
		return -EPERM;

	if (copy_from_user(pidname, buffer, count)) {
		return -EFAULT;
	}
	if (count && (pidname[count-1]==10 || pidname[count-1]==13)) {
		pidname[count-1]='\0';
	}
	else
		pidname[count]='\0';

    pid = simple_strtol(pidname,s,10);
    p = find_vpid(pid);
    task = get_pid_task(p,PIDTYPE_PID);
    if (task) {
        setns(task);
    }
    else {
        printk(KERN_CRIT "Task %d not found",pid);
    }

	return count;
}

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

        free_pid_ns2 = kallsyms_lookup_name("free_pid_ns");
        printk(KERN_CRIT "free_pid_ns = %x",free_pid_ns2);

        free_nsproxy2 = kallsyms_lookup_name("free_nsproxy");
        printk(KERN_CRIT "free_nsproxy = %x",(unsigned int) free_nsproxy2);

        switch_task_namespaces2 = kallsyms_lookup_name("switch_task_namespaces");
        printk(KERN_CRIT "switch_task_namespaces = %x",(unsigned int) switch_task_namespaces2);

        create_new_namespaces = kallsyms_lookup_name("create_new_namespaces");
        printk(KERN_CRIT "create_new_namespaces = %x",(unsigned int) create_new_namespaces);

        /*put_pid_ns2 = kallsyms_lookup_name("put_pid_ns");
        printk(KERN_CRIT "Put pid ns = %x",put_pid_ns2);*/

        proc_entry = create_proc_entry("pidsu", 0644, NULL);
	    proc_entry->write_proc = pidsu_write;
        return ret;
}

module_init(pidsu_init);
module_exit(pidsu_exit);