1#ifndef _LINUX_NSPROXY_H
2#define _LINUX_NSPROXY_H
3
4#include <linux/spinlock.h>
5#include <linux/sched.h>
6
7struct mnt_namespace;
8struct uts_namespace;
9struct ipc_namespace;
10struct pid_namespace;
11struct fs_struct;
12
13/*
14 * A structure to contain pointers to all per-process
15 * namespaces - fs (mount), uts, network, sysvipc, etc.
16 *
17 * The pid namespace is an exception -- it's accessed using
18 * task_active_pid_ns.  The pid namespace here is the
19 * namespace that children will use.
20 *
21 * 'count' is the number of tasks holding a reference.
22 * The count for each namespace, then, will be the number
23 * of nsproxies pointing to it, not the number of tasks.
24 *
25 * The nsproxy is shared by tasks which share all namespaces.
26 * As soon as a single namespace is cloned or unshared, the
27 * nsproxy is copied.
28 */
29struct nsproxy {
30	atomic_t count;
31	struct uts_namespace *uts_ns;
32	struct ipc_namespace *ipc_ns;
33	struct mnt_namespace *mnt_ns;
34	struct pid_namespace *pid_ns_for_children;
35	struct net 	     *net_ns;
36};
37extern struct nsproxy init_nsproxy;
38
39/*
40 * the namespaces access rules are:
41 *
42 *  1. only current task is allowed to change tsk->nsproxy pointer or
43 *     any pointer on the nsproxy itself.  Current must hold the task_lock
44 *     when changing tsk->nsproxy.
45 *
46 *  2. when accessing (i.e. reading) current task's namespaces - no
47 *     precautions should be taken - just dereference the pointers
48 *
49 *  3. the access to other task namespaces is performed like this
50 *     task_lock(task);
51 *     nsproxy = task->nsproxy;
52 *     if (nsproxy != NULL) {
53 *             / *
54 *               * work with the namespaces here
55 *               * e.g. get the reference on one of them
56 *               * /
57 *     } / *
58 *         * NULL task->nsproxy means that this task is
59 *         * almost dead (zombie)
60 *         * /
61 *     task_unlock(task);
62 *
63 */
64
65int copy_namespaces(unsigned long flags, struct task_struct *tsk);
66void exit_task_namespaces(struct task_struct *tsk);
67void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
68void free_nsproxy(struct nsproxy *ns);
69int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
70	struct cred *, struct fs_struct *);
71int __init nsproxy_cache_init(void);
72
73static inline void put_nsproxy(struct nsproxy *ns)
74{
75	if (atomic_dec_and_test(&ns->count)) {
76		free_nsproxy(ns);
77	}
78}
79
80static inline void get_nsproxy(struct nsproxy *ns)
81{
82	atomic_inc(&ns->count);
83}
84
85#endif
86