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