/*
   * 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
   *
   */
  
  #include <linux/pid.h>
  #include <linux/pid_namespace.h>
  #include <linux/syscalls.h>
  #include <linux/err.h>

  #include <linux/acct.h>

  #include <linux/slab.h>

  #include <linux/proc_fs.h>

  
  #define BITS_PER_PAGE		(PAGE_SIZE*8)
  
  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 struct kmem_cache *pid_ns_cachep;
  
  /*
   * creates the kmem cache to allocate pids from.
   * @nr_ids: the number of numerical ids this pid will have to carry
   */
  
  static struct kmem_cache *create_pid_cachep(int nr_ids)
  {
  	struct pid_cache *pcache;
  	struct kmem_cache *cachep;
  
  	mutex_lock(&pid_caches_mutex);
  	list_for_each_entry(pcache, &pid_caches_lh, list)
  		if (pcache->nr_ids == nr_ids)
  			goto out;
  
  	pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
  	if (pcache == NULL)
  		goto err_alloc;
  
  	snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
  	cachep = kmem_cache_create(pcache->name,
  			sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
  			0, SLAB_HWCACHE_ALIGN, NULL);
  	if (cachep == NULL)
  		goto err_cachep;
  
  	pcache->nr_ids = nr_ids;
  	pcache->cachep = cachep;
  	list_add(&pcache->list, &pid_caches_lh);
  out:
  	mutex_unlock(&pid_caches_mutex);
  	return pcache->cachep;
  
  err_cachep:
  	kfree(pcache);
  err_alloc:
  	mutex_unlock(&pid_caches_mutex);
  	return NULL;
  }

  static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_pid_ns)

  {
  	struct pid_namespace *ns;

  	unsigned int level = parent_pid_ns->level + 1;

  	int i, err = -ENOMEM;

  	ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);

  	if (ns == NULL)
  		goto out;
  
  	ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
  	if (!ns->pidmap[0].page)
  		goto out_free;
  
  	ns->pid_cachep = create_pid_cachep(level + 1);
  	if (ns->pid_cachep == NULL)
  		goto out_free_map;
  
  	kref_init(&ns->kref);

  	ns->level = level;

  	ns->parent = get_pid_ns(parent_pid_ns);

  
  	set_bit(0, ns->pidmap[0].page);
  	atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);

  	for (i = 1; i < PIDMAP_ENTRIES; i++)

  		atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);

  	err = pid_ns_prepare_proc(ns);
  	if (err)
  		goto out_put_parent_pid_ns;

  	return ns;

  out_put_parent_pid_ns:
  	put_pid_ns(parent_pid_ns);

  out_free_map:
  	kfree(ns->pidmap[0].page);
  out_free:
  	kmem_cache_free(pid_ns_cachep, ns);
  out:

  	return ERR_PTR(err);

  }
  
  static void destroy_pid_namespace(struct pid_namespace *ns)
  {
  	int i;
  
  	for (i = 0; i < PIDMAP_ENTRIES; i++)
  		kfree(ns->pidmap[i].page);
  	kmem_cache_free(pid_ns_cachep, ns);
  }
  
  struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
  {

  	if (!(flags & CLONE_NEWPID))

  		return get_pid_ns(old_ns);

  	if (flags & (CLONE_THREAD|CLONE_PARENT))

  		return ERR_PTR(-EINVAL);
  	return create_pid_namespace(old_ns);

  }
  
  void free_pid_ns(struct kref *kref)
  {
  	struct pid_namespace *ns, *parent;
  
  	ns = container_of(kref, struct pid_namespace, kref);
  
  	parent = ns->parent;
  	destroy_pid_namespace(ns);
  
  	if (parent != NULL)
  		put_pid_ns(parent);
  }
  
  void zap_pid_ns_processes(struct pid_namespace *pid_ns)
  {
  	int nr;
  	int rc;

  	struct task_struct *task;

  
  	/*
  	 * The last thread in the cgroup-init thread group is terminating.
  	 * Find remaining pid_ts in the namespace, signal and wait for them
  	 * to exit.
  	 *
  	 * Note:  This signals each threads in the namespace - even those that
  	 * 	  belong to the same thread group, To avoid this, we would have
  	 * 	  to walk the entire tasklist looking a processes in this
  	 * 	  namespace, but that could be unnecessarily expensive if the
  	 * 	  pid namespace has just a few processes. Or we need to
  	 * 	  maintain a tasklist for each pid namespace.
  	 *
  	 */
  	read_lock(&tasklist_lock);
  	nr = next_pidmap(pid_ns, 1);
  	while (nr > 0) {

  		rcu_read_lock();
  
  		/*

  		 * Any nested-container's init processes won't ignore the
  		 * SEND_SIG_NOINFO signal, see send_signal()->si_fromuser().

  		 */
  		task = pid_task(find_vpid(nr), PIDTYPE_PID);
  		if (task)

  			send_sig_info(SIGKILL, SEND_SIG_NOINFO, task);

  
  		rcu_read_unlock();

  		nr = next_pidmap(pid_ns, nr);
  	}
  	read_unlock(&tasklist_lock);
  
  	do {
  		clear_thread_flag(TIF_SIGPENDING);
  		rc = sys_wait4(-1, NULL, __WALL, NULL);
  	} while (rc != -ECHILD);

  	acct_exit_ns(pid_ns);

  	return;
  }

  static int pid_ns_ctl_handler(struct ctl_table *table, int write,
  		void __user *buffer, size_t *lenp, loff_t *ppos)
  {
  	struct ctl_table tmp = *table;
  
  	if (write && !capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	/*
  	 * Writing directly to ns' last_pid field is OK, since this field
  	 * is volatile in a living namespace anyway and a code writing to
  	 * it should synchronize its usage with external means.
  	 */
  
  	tmp.data = &current->nsproxy->pid_ns->last_pid;
  	return proc_dointvec(&tmp, write, buffer, lenp, ppos);
  }
  
  static struct ctl_table pid_ns_ctl_table[] = {
  	{
  		.procname = "ns_last_pid",
  		.maxlen = sizeof(int),
  		.mode = 0666, /* permissions are checked in the handler */
  		.proc_handler = pid_ns_ctl_handler,
  	},
  	{ }
  };
  
  static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };

  static __init int pid_namespaces_init(void)
  {
  	pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);

  	register_sysctl_paths(kern_path, pid_ns_ctl_table);

  	return 0;
  }
  
  __initcall(pid_namespaces_init);