include/linux/nsproxy.h

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