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 * 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 */ 29 struct 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 }; 37 extern 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 44 * 45 * 2. when accessing (i.e. reading) current task's namespaces - no 46 * precautions should be taken - just dereference the pointers 47 * 48 * 3. the access to other task namespaces is performed like this 49 * rcu_read_lock(); 50 * nsproxy = task_nsproxy(tsk); 51 * if (nsproxy != NULL) { 52 * / * 53 * * work with the namespaces here 54 * * e.g. get the reference on one of them 55 * * / 56 * } / * 57 * * NULL task_nsproxy() means that this task is 58 * * almost dead (zombie) 59 * * / 60 * rcu_read_unlock(); 61 * 62 */ 63 64 static inline struct nsproxy *task_nsproxy(struct task_struct *tsk) 65 { 66 return rcu_dereference(tsk->nsproxy); 67 } 68 69 int copy_namespaces(unsigned long flags, struct task_struct *tsk); 70 void exit_task_namespaces(struct task_struct *tsk); 71 void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new); 72 void free_nsproxy(struct nsproxy *ns); 73 int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **, 74 struct cred *, struct fs_struct *); 75 int __init nsproxy_cache_init(void); 76 77 static inline void put_nsproxy(struct nsproxy *ns) 78 { 79 if (atomic_dec_and_test(&ns->count)) { 80 free_nsproxy(ns); 81 } 82 } 83 84 static inline void get_nsproxy(struct nsproxy *ns) 85 { 86 atomic_inc(&ns->count); 87 } 88 89 #endif 90