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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
1da177e4 LT |
2 | #ifndef _LINUX_PID_H |
3 | #define _LINUX_PID_H | |
4 | ||
6d5e9d63 | 5 | #include <linux/pid_types.h> |
b2d09103 | 6 | #include <linux/rculist.h> |
f551103c | 7 | #include <linux/rcupdate.h> |
f57e515a | 8 | #include <linux/refcount.h> |
f551103c | 9 | #include <linux/sched.h> |
6d5e9d63 | 10 | #include <linux/wait.h> |
1da177e4 | 11 | |
92476d7f EB |
12 | /* |
13 | * What is struct pid? | |
14 | * | |
15 | * A struct pid is the kernel's internal notion of a process identifier. | |
16 | * It refers to individual tasks, process groups, and sessions. While | |
17 | * there are processes attached to it the struct pid lives in a hash | |
18 | * table, so it and then the processes that it refers to can be found | |
19 | * quickly from the numeric pid value. The attached processes may be | |
20 | * quickly accessed by following pointers from struct pid. | |
21 | * | |
25985edc | 22 | * Storing pid_t values in the kernel and referring to them later has a |
92476d7f EB |
23 | * problem. The process originally with that pid may have exited and the |
24 | * pid allocator wrapped, and another process could have come along | |
25 | * and been assigned that pid. | |
26 | * | |
27 | * Referring to user space processes by holding a reference to struct | |
28 | * task_struct has a problem. When the user space process exits | |
29 | * the now useless task_struct is still kept. A task_struct plus a | |
30 | * stack consumes around 10K of low kernel memory. More precisely | |
31 | * this is THREAD_SIZE + sizeof(struct task_struct). By comparison | |
32 | * a struct pid is about 64 bytes. | |
33 | * | |
34 | * Holding a reference to struct pid solves both of these problems. | |
35 | * It is small so holding a reference does not consume a lot of | |
84d73786 SB |
36 | * resources, and since a new struct pid is allocated when the numeric pid |
37 | * value is reused (when pids wrap around) we don't mistakenly refer to new | |
38 | * processes. | |
92476d7f EB |
39 | */ |
40 | ||
4c3f2ead SB |
41 | |
42 | /* | |
43 | * struct upid is used to get the id of the struct pid, as it is | |
44 | * seen in particular namespace. Later the struct pid is found with | |
45 | * find_pid_ns() using the int nr and struct pid_namespace *ns. | |
46 | */ | |
47 | ||
9d9539db CB |
48 | #define RESERVED_PIDS 300 |
49 | ||
4c3f2ead | 50 | struct upid { |
4c3f2ead SB |
51 | int nr; |
52 | struct pid_namespace *ns; | |
4c3f2ead SB |
53 | }; |
54 | ||
1da177e4 LT |
55 | struct pid |
56 | { | |
f57e515a | 57 | refcount_t count; |
33166b1f | 58 | unsigned int level; |
63f818f4 | 59 | spinlock_t lock; |
b28ddcc3 | 60 | struct dentry *stashed; |
9d9539db | 61 | u64 ino; |
92476d7f EB |
62 | /* lists of tasks that use this pid */ |
63 | struct hlist_head tasks[PIDTYPE_MAX]; | |
7bc3e6e5 | 64 | struct hlist_head inodes; |
b53b0b9d JFG |
65 | /* wait queue for pidfd notifications */ |
66 | wait_queue_head_t wait_pidfd; | |
92476d7f | 67 | struct rcu_head rcu; |
b69f0aeb | 68 | struct upid numbers[]; |
1da177e4 LT |
69 | }; |
70 | ||
820e45db SB |
71 | extern struct pid init_struct_pid; |
72 | ||
3695eae5 CB |
73 | struct file; |
74 | ||
64bef697 | 75 | struct pid *pidfd_pid(const struct file *file); |
1aa92cd3 | 76 | struct pid *pidfd_get_pid(unsigned int fd, unsigned int *flags); |
e9bdcdbf | 77 | struct task_struct *pidfd_get_task(int pidfd, unsigned int *flags); |
6ae930d9 | 78 | int pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret); |
64bef697 | 79 | void do_notify_pidfd(struct task_struct *task); |
3695eae5 | 80 | |
92476d7f EB |
81 | static inline struct pid *get_pid(struct pid *pid) |
82 | { | |
83 | if (pid) | |
f57e515a | 84 | refcount_inc(&pid->count); |
92476d7f EB |
85 | return pid; |
86 | } | |
87 | ||
b3c97528 HH |
88 | extern void put_pid(struct pid *pid); |
89 | extern struct task_struct *pid_task(struct pid *pid, enum pid_type); | |
3d6d8da4 CB |
90 | static inline bool pid_has_task(struct pid *pid, enum pid_type type) |
91 | { | |
92 | return !hlist_empty(&pid->tasks[type]); | |
93 | } | |
b3c97528 | 94 | extern struct task_struct *get_pid_task(struct pid *pid, enum pid_type); |
1da177e4 | 95 | |
1a657f78 ON |
96 | extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type); |
97 | ||
1da177e4 | 98 | /* |
81907739 | 99 | * these helpers must be called with the tasklist_lock write-held. |
1da177e4 | 100 | */ |
81907739 | 101 | extern void attach_pid(struct task_struct *task, enum pid_type); |
b3c97528 | 102 | extern void detach_pid(struct task_struct *task, enum pid_type); |
24336eae ON |
103 | extern void change_pid(struct task_struct *task, enum pid_type, |
104 | struct pid *pid); | |
6b03d130 | 105 | extern void exchange_tids(struct task_struct *task, struct task_struct *old); |
b3c97528 HH |
106 | extern void transfer_pid(struct task_struct *old, struct task_struct *new, |
107 | enum pid_type); | |
1da177e4 | 108 | |
2374c09b CH |
109 | extern int pid_max; |
110 | extern int pid_max_min, pid_max_max; | |
111 | ||
1da177e4 LT |
112 | /* |
113 | * look up a PID in the hash table. Must be called with the tasklist_lock | |
92476d7f | 114 | * or rcu_read_lock() held. |
198fe21b PE |
115 | * |
116 | * find_pid_ns() finds the pid in the namespace specified | |
26498e89 | 117 | * find_vpid() finds the pid by its virtual id, i.e. in the current namespace |
198fe21b | 118 | * |
dbda0de5 | 119 | * see also find_task_by_vpid() set in include/linux/sched.h |
92476d7f | 120 | */ |
b3c97528 | 121 | extern struct pid *find_pid_ns(int nr, struct pid_namespace *ns); |
8990571e | 122 | extern struct pid *find_vpid(int nr); |
92476d7f EB |
123 | |
124 | /* | |
125 | * Lookup a PID in the hash table, and return with it's count elevated. | |
1da177e4 | 126 | */ |
92476d7f | 127 | extern struct pid *find_get_pid(int nr); |
198fe21b | 128 | extern struct pid *find_ge_pid(int nr, struct pid_namespace *); |
1da177e4 | 129 | |
49cb2fc4 AR |
130 | extern struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid, |
131 | size_t set_tid_size); | |
b3c97528 | 132 | extern void free_pid(struct pid *pid); |
c876ad76 | 133 | extern void disable_pid_allocation(struct pid_namespace *ns); |
1da177e4 | 134 | |
f9fb860f EB |
135 | /* |
136 | * ns_of_pid() returns the pid namespace in which the specified pid was | |
137 | * allocated. | |
138 | * | |
139 | * NOTE: | |
140 | * ns_of_pid() is expected to be called for a process (task) that has | |
141 | * an attached 'struct pid' (see attach_pid(), detach_pid()) i.e @pid | |
142 | * is expected to be non-NULL. If @pid is NULL, caller should handle | |
143 | * the resulting NULL pid-ns. | |
144 | */ | |
145 | static inline struct pid_namespace *ns_of_pid(struct pid *pid) | |
146 | { | |
147 | struct pid_namespace *ns = NULL; | |
148 | if (pid) | |
149 | ns = pid->numbers[pid->level].ns; | |
150 | return ns; | |
151 | } | |
152 | ||
45a68628 EB |
153 | /* |
154 | * is_child_reaper returns true if the pid is the init process | |
155 | * of the current namespace. As this one could be checked before | |
156 | * pid_ns->child_reaper is assigned in copy_process, we check | |
157 | * with the pid number. | |
158 | */ | |
159 | static inline bool is_child_reaper(struct pid *pid) | |
160 | { | |
161 | return pid->numbers[pid->level].nr == 1; | |
162 | } | |
163 | ||
7af57294 PE |
164 | /* |
165 | * the helpers to get the pid's id seen from different namespaces | |
166 | * | |
167 | * pid_nr() : global id, i.e. the id seen from the init namespace; | |
44c4e1b2 EB |
168 | * pid_vnr() : virtual id, i.e. the id seen from the pid namespace of |
169 | * current. | |
7af57294 PE |
170 | * pid_nr_ns() : id seen from the ns specified. |
171 | * | |
172 | * see also task_xid_nr() etc in include/linux/sched.h | |
173 | */ | |
174 | ||
5feb8f5f EB |
175 | static inline pid_t pid_nr(struct pid *pid) |
176 | { | |
177 | pid_t nr = 0; | |
178 | if (pid) | |
7af57294 PE |
179 | nr = pid->numbers[0].nr; |
180 | return nr; | |
181 | } | |
182 | ||
183 | pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns); | |
44c4e1b2 | 184 | pid_t pid_vnr(struct pid *pid); |
5feb8f5f | 185 | |
1d32849b AM |
186 | #define do_each_pid_task(pid, type, task) \ |
187 | do { \ | |
5ef64761 | 188 | if ((pid) != NULL) \ |
b67bfe0d | 189 | hlist_for_each_entry_rcu((task), \ |
2c470475 | 190 | &(pid)->tasks[type], pid_links[type]) { |
d387cae0 | 191 | |
46f382d2 ON |
192 | /* |
193 | * Both old and new leaders may be attached to | |
194 | * the same pid in the middle of de_thread(). | |
195 | */ | |
1d32849b | 196 | #define while_each_pid_task(pid, type, task) \ |
46f382d2 ON |
197 | if (type == PIDTYPE_PID) \ |
198 | break; \ | |
1d32849b | 199 | } \ |
d387cae0 | 200 | } while (0) |
558cb325 | 201 | |
2d70b68d KC |
202 | #define do_each_pid_thread(pid, type, task) \ |
203 | do_each_pid_task(pid, type, task) { \ | |
204 | struct task_struct *tg___ = task; \ | |
e3b5a342 | 205 | for_each_thread(tg___, task) { |
2d70b68d KC |
206 | |
207 | #define while_each_pid_thread(pid, type, task) \ | |
e3b5a342 | 208 | } \ |
2d70b68d KC |
209 | task = tg___; \ |
210 | } while_each_pid_task(pid, type, task) | |
f551103c KO |
211 | |
212 | static inline struct pid *task_pid(struct task_struct *task) | |
213 | { | |
214 | return task->thread_pid; | |
215 | } | |
216 | ||
217 | /* | |
218 | * the helpers to get the task's different pids as they are seen | |
219 | * from various namespaces | |
220 | * | |
221 | * task_xid_nr() : global id, i.e. the id seen from the init namespace; | |
222 | * task_xid_vnr() : virtual id, i.e. the id seen from the pid namespace of | |
223 | * current. | |
224 | * task_xid_nr_ns() : id seen from the ns specified; | |
225 | * | |
226 | * see also pid_nr() etc in include/linux/pid.h | |
227 | */ | |
228 | pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type, struct pid_namespace *ns); | |
229 | ||
230 | static inline pid_t task_pid_nr(struct task_struct *tsk) | |
231 | { | |
232 | return tsk->pid; | |
233 | } | |
234 | ||
235 | static inline pid_t task_pid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns) | |
236 | { | |
237 | return __task_pid_nr_ns(tsk, PIDTYPE_PID, ns); | |
238 | } | |
239 | ||
240 | static inline pid_t task_pid_vnr(struct task_struct *tsk) | |
241 | { | |
242 | return __task_pid_nr_ns(tsk, PIDTYPE_PID, NULL); | |
243 | } | |
244 | ||
245 | ||
246 | static inline pid_t task_tgid_nr(struct task_struct *tsk) | |
247 | { | |
248 | return tsk->tgid; | |
249 | } | |
250 | ||
251 | /** | |
252 | * pid_alive - check that a task structure is not stale | |
253 | * @p: Task structure to be checked. | |
254 | * | |
255 | * Test if a process is not yet dead (at most zombie state) | |
256 | * If pid_alive fails, then pointers within the task structure | |
257 | * can be stale and must not be dereferenced. | |
258 | * | |
259 | * Return: 1 if the process is alive. 0 otherwise. | |
260 | */ | |
261 | static inline int pid_alive(const struct task_struct *p) | |
262 | { | |
263 | return p->thread_pid != NULL; | |
264 | } | |
265 | ||
266 | static inline pid_t task_pgrp_nr_ns(struct task_struct *tsk, struct pid_namespace *ns) | |
267 | { | |
268 | return __task_pid_nr_ns(tsk, PIDTYPE_PGID, ns); | |
269 | } | |
270 | ||
271 | static inline pid_t task_pgrp_vnr(struct task_struct *tsk) | |
272 | { | |
273 | return __task_pid_nr_ns(tsk, PIDTYPE_PGID, NULL); | |
274 | } | |
275 | ||
276 | ||
277 | static inline pid_t task_session_nr_ns(struct task_struct *tsk, struct pid_namespace *ns) | |
278 | { | |
279 | return __task_pid_nr_ns(tsk, PIDTYPE_SID, ns); | |
280 | } | |
281 | ||
282 | static inline pid_t task_session_vnr(struct task_struct *tsk) | |
283 | { | |
284 | return __task_pid_nr_ns(tsk, PIDTYPE_SID, NULL); | |
285 | } | |
286 | ||
287 | static inline pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns) | |
288 | { | |
289 | return __task_pid_nr_ns(tsk, PIDTYPE_TGID, ns); | |
290 | } | |
291 | ||
292 | static inline pid_t task_tgid_vnr(struct task_struct *tsk) | |
293 | { | |
294 | return __task_pid_nr_ns(tsk, PIDTYPE_TGID, NULL); | |
295 | } | |
296 | ||
297 | static inline pid_t task_ppid_nr_ns(const struct task_struct *tsk, struct pid_namespace *ns) | |
298 | { | |
299 | pid_t pid = 0; | |
300 | ||
301 | rcu_read_lock(); | |
302 | if (pid_alive(tsk)) | |
303 | pid = task_tgid_nr_ns(rcu_dereference(tsk->real_parent), ns); | |
304 | rcu_read_unlock(); | |
305 | ||
306 | return pid; | |
307 | } | |
308 | ||
309 | static inline pid_t task_ppid_nr(const struct task_struct *tsk) | |
310 | { | |
311 | return task_ppid_nr_ns(tsk, &init_pid_ns); | |
312 | } | |
313 | ||
314 | /* Obsolete, do not use: */ | |
315 | static inline pid_t task_pgrp_nr(struct task_struct *tsk) | |
316 | { | |
317 | return task_pgrp_nr_ns(tsk, &init_pid_ns); | |
318 | } | |
319 | ||
320 | /** | |
321 | * is_global_init - check if a task structure is init. Since init | |
322 | * is free to have sub-threads we need to check tgid. | |
323 | * @tsk: Task structure to be checked. | |
324 | * | |
325 | * Check if a task structure is the first user space task the kernel created. | |
326 | * | |
327 | * Return: 1 if the task structure is init. 0 otherwise. | |
328 | */ | |
329 | static inline int is_global_init(struct task_struct *tsk) | |
330 | { | |
331 | return task_tgid_nr(tsk) == 1; | |
332 | } | |
333 | ||
1da177e4 | 334 | #endif /* _LINUX_PID_H */ |