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
12 /*
13 * A structure to contain pointers to all per-process
14 * namespaces - fs (mount), uts, network, sysvipc, etc.
15 *
16 * 'count' is the number of tasks holding a reference.
17 * The count for each namespace, then, will be the number
18 * of nsproxies pointing to it, not the number of tasks.
19 *
20 * The nsproxy is shared by tasks which share all namespaces.
21 * As soon as a single namespace is cloned or unshared, the
22 * nsproxy is copied.
23 */
24 struct nsproxy {
25 atomic_t count;
26 struct uts_namespace *uts_ns;
27 struct ipc_namespace *ipc_ns;
28 struct mnt_namespace *mnt_ns;
29 struct pid_namespace *pid_ns;
30 struct net *net_ns;
31 };
32 extern struct nsproxy init_nsproxy;
33
34 /*
35 * the namespaces access rules are:
36 *
37 * 1. only current task is allowed to change tsk->nsproxy pointer or
38 * any pointer on the nsproxy itself
39 *
40 * 2. when accessing (i.e. reading) current task's namespaces - no
41 * precautions should be taken - just dereference the pointers
42 *
43 * 3. the access to other task namespaces is performed like this
44 * rcu_read_lock();
45 * nsproxy = task_nsproxy(tsk);
46 * if (nsproxy != NULL) {
47 * / *
48 * * work with the namespaces here
49 * * e.g. get the reference on one of them
50 * * /
51 * } / *
52 * * NULL task_nsproxy() means that this task is
53 * * almost dead (zombie)
54 * * /
55 * rcu_read_unlock();
56 *
57 */
58
task_nsproxy(struct task_struct * tsk)59 static inline struct nsproxy *task_nsproxy(struct task_struct *tsk)
60 {
61 return rcu_dereference(tsk->nsproxy);
62 }
63
64 int copy_namespaces(unsigned long flags, struct task_struct *tsk);
65 void exit_task_namespaces(struct task_struct *tsk);
66 void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
67 void free_nsproxy(struct nsproxy *ns);
68 int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
69 struct fs_struct *);
70
put_nsproxy(struct nsproxy * ns)71 static inline void put_nsproxy(struct nsproxy *ns)
72 {
73 if (atomic_dec_and_test(&ns->count)) {
74 free_nsproxy(ns);
75 }
76 }
77
get_nsproxy(struct nsproxy * ns)78 static inline void get_nsproxy(struct nsproxy *ns)
79 {
80 atomic_inc(&ns->count);
81 }
82
83 #ifdef CONFIG_CGROUP_NS
84 int ns_cgroup_clone(struct task_struct *tsk, struct pid *pid);
85 #else
ns_cgroup_clone(struct task_struct * tsk,struct pid * pid)86 static inline int ns_cgroup_clone(struct task_struct *tsk, struct pid *pid)
87 {
88 return 0;
89 }
90 #endif
91
92 #endif
93