LXR linux/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
   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