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Greg Kroah-Hartmanb2441312017-11-01 15:07:57 +01001/* SPDX-License-Identifier: GPL-2.0 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07002#ifndef _LINUX_PID_H
3#define _LINUX_PID_H
4
Ingo Molnarb2d09102017-02-04 01:27:20 +01005#include <linux/rculist.h>
Eric W. Biederman92476d72006-03-31 02:31:42 -08006
Linus Torvalds1da177e2005-04-16 15:20:36 -07007enum pid_type
8{
9 PIDTYPE_PID,
Linus Torvalds1da177e2005-04-16 15:20:36 -070010 PIDTYPE_PGID,
11 PIDTYPE_SID,
Oleg Nesterovdd1c1f22017-08-21 17:35:02 +020012 PIDTYPE_MAX,
13 /* only valid to __task_pid_nr_ns() */
14 __PIDTYPE_TGID
Linus Torvalds1da177e2005-04-16 15:20:36 -070015};
16
Eric W. Biederman92476d72006-03-31 02:31:42 -080017/*
18 * What is struct pid?
19 *
20 * A struct pid is the kernel's internal notion of a process identifier.
21 * It refers to individual tasks, process groups, and sessions. While
22 * there are processes attached to it the struct pid lives in a hash
23 * table, so it and then the processes that it refers to can be found
24 * quickly from the numeric pid value. The attached processes may be
25 * quickly accessed by following pointers from struct pid.
26 *
Lucas De Marchi25985ed2011-03-30 22:57:33 -030027 * Storing pid_t values in the kernel and referring to them later has a
Eric W. Biederman92476d72006-03-31 02:31:42 -080028 * problem. The process originally with that pid may have exited and the
29 * pid allocator wrapped, and another process could have come along
30 * and been assigned that pid.
31 *
32 * Referring to user space processes by holding a reference to struct
33 * task_struct has a problem. When the user space process exits
34 * the now useless task_struct is still kept. A task_struct plus a
35 * stack consumes around 10K of low kernel memory. More precisely
36 * this is THREAD_SIZE + sizeof(struct task_struct). By comparison
37 * a struct pid is about 64 bytes.
38 *
39 * Holding a reference to struct pid solves both of these problems.
40 * It is small so holding a reference does not consume a lot of
Sukadev Bhattiprolu84d73782006-12-08 02:38:01 -080041 * resources, and since a new struct pid is allocated when the numeric pid
42 * value is reused (when pids wrap around) we don't mistakenly refer to new
43 * processes.
Eric W. Biederman92476d72006-03-31 02:31:42 -080044 */
45
Sukadev Bhattiprolu4c3f2ea2007-10-18 23:40:03 -070046
47/*
48 * struct upid is used to get the id of the struct pid, as it is
49 * seen in particular namespace. Later the struct pid is found with
50 * find_pid_ns() using the int nr and struct pid_namespace *ns.
51 */
52
53struct upid {
Pavel Emelyanove49859e2008-07-25 01:48:36 -070054 /* Try to keep pid_chain in the same cacheline as nr for find_vpid */
Sukadev Bhattiprolu4c3f2ea2007-10-18 23:40:03 -070055 int nr;
56 struct pid_namespace *ns;
57 struct hlist_node pid_chain;
58};
59
Linus Torvalds1da177e2005-04-16 15:20:36 -070060struct pid
61{
Eric W. Biederman92476d72006-03-31 02:31:42 -080062 atomic_t count;
Richard Kennedy33166b12008-07-25 01:48:35 -070063 unsigned int level;
Eric W. Biederman92476d72006-03-31 02:31:42 -080064 /* lists of tasks that use this pid */
65 struct hlist_head tasks[PIDTYPE_MAX];
66 struct rcu_head rcu;
Sukadev Bhattiprolu4c3f2ea2007-10-18 23:40:03 -070067 struct upid numbers[1];
Linus Torvalds1da177e2005-04-16 15:20:36 -070068};
69
Sukadev Bhattiprolu820e45d2007-05-10 22:23:00 -070070extern struct pid init_struct_pid;
71
Eric W. Biederman92476d72006-03-31 02:31:42 -080072struct pid_link
73{
74 struct hlist_node node;
75 struct pid *pid;
76};
77
78static inline struct pid *get_pid(struct pid *pid)
79{
80 if (pid)
81 atomic_inc(&pid->count);
82 return pid;
83}
84
Harvey Harrisonb3c97522008-02-13 15:03:15 -080085extern void put_pid(struct pid *pid);
86extern struct task_struct *pid_task(struct pid *pid, enum pid_type);
87extern struct task_struct *get_pid_task(struct pid *pid, enum pid_type);
Linus Torvalds1da177e2005-04-16 15:20:36 -070088
Oleg Nesterov1a657f782006-10-02 02:18:59 -070089extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type);
90
Linus Torvalds1da177e2005-04-16 15:20:36 -070091/*
Oleg Nesterov81907732013-07-03 15:08:31 -070092 * these helpers must be called with the tasklist_lock write-held.
Linus Torvalds1da177e2005-04-16 15:20:36 -070093 */
Oleg Nesterov81907732013-07-03 15:08:31 -070094extern void attach_pid(struct task_struct *task, enum pid_type);
Harvey Harrisonb3c97522008-02-13 15:03:15 -080095extern void detach_pid(struct task_struct *task, enum pid_type);
Oleg Nesterov24336ea2008-04-30 00:54:26 -070096extern void change_pid(struct task_struct *task, enum pid_type,
97 struct pid *pid);
Harvey Harrisonb3c97522008-02-13 15:03:15 -080098extern void transfer_pid(struct task_struct *old, struct task_struct *new,
99 enum pid_type);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100
Pavel Emelyanov198fe212007-10-18 23:40:06 -0700101struct pid_namespace;
102extern struct pid_namespace init_pid_ns;
103
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104/*
105 * look up a PID in the hash table. Must be called with the tasklist_lock
Eric W. Biederman92476d72006-03-31 02:31:42 -0800106 * or rcu_read_lock() held.
Pavel Emelyanov198fe212007-10-18 23:40:06 -0700107 *
108 * find_pid_ns() finds the pid in the namespace specified
Sisir Koppaka26498e82011-05-26 16:25:57 -0700109 * find_vpid() finds the pid by its virtual id, i.e. in the current namespace
Pavel Emelyanov198fe212007-10-18 23:40:06 -0700110 *
Pavel Emelyanovdbda0de2008-07-25 01:48:37 -0700111 * see also find_task_by_vpid() set in include/linux/sched.h
Linus Torvalds1da177e2005-04-16 15:20:36 -0700112 */
Harvey Harrisonb3c97522008-02-13 15:03:15 -0800113extern struct pid *find_pid_ns(int nr, struct pid_namespace *ns);
Pavel Emelyanov89905712007-10-18 23:40:19 -0700114extern struct pid *find_vpid(int nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115
Eric W. Biederman92476d72006-03-31 02:31:42 -0800116/*
117 * Lookup a PID in the hash table, and return with it's count elevated.
118 */
119extern struct pid *find_get_pid(int nr);
Pavel Emelyanov198fe212007-10-18 23:40:06 -0700120extern struct pid *find_ge_pid(int nr, struct pid_namespace *);
Linus Torvaldsc78193e2011-04-18 10:35:30 -0700121int next_pidmap(struct pid_namespace *pid_ns, unsigned int last);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700122
Pavel Emelyanov8ef047a2007-10-18 23:40:05 -0700123extern struct pid *alloc_pid(struct pid_namespace *ns);
Harvey Harrisonb3c97522008-02-13 15:03:15 -0800124extern void free_pid(struct pid *pid);
Eric W. Biedermanc876ad762012-12-21 20:27:12 -0800125extern void disable_pid_allocation(struct pid_namespace *ns);
Eric W. Biederman92476d72006-03-31 02:31:42 -0800126
Pavel Emelyanov7af57292007-10-18 23:40:06 -0700127/*
Eric W. Biedermanf9fb8602009-01-07 18:08:46 -0800128 * ns_of_pid() returns the pid namespace in which the specified pid was
129 * allocated.
130 *
131 * NOTE:
132 * ns_of_pid() is expected to be called for a process (task) that has
133 * an attached 'struct pid' (see attach_pid(), detach_pid()) i.e @pid
134 * is expected to be non-NULL. If @pid is NULL, caller should handle
135 * the resulting NULL pid-ns.
136 */
137static inline struct pid_namespace *ns_of_pid(struct pid *pid)
138{
139 struct pid_namespace *ns = NULL;
140 if (pid)
141 ns = pid->numbers[pid->level].ns;
142 return ns;
143}
144
145/*
Eric W. Biederman45a68622011-03-23 16:43:12 -0700146 * is_child_reaper returns true if the pid is the init process
147 * of the current namespace. As this one could be checked before
148 * pid_ns->child_reaper is assigned in copy_process, we check
149 * with the pid number.
150 */
151static inline bool is_child_reaper(struct pid *pid)
152{
153 return pid->numbers[pid->level].nr == 1;
154}
155
156/*
Pavel Emelyanov7af57292007-10-18 23:40:06 -0700157 * the helpers to get the pid's id seen from different namespaces
158 *
159 * pid_nr() : global id, i.e. the id seen from the init namespace;
Eric W. Biederman44c4e1b2008-02-08 04:19:15 -0800160 * pid_vnr() : virtual id, i.e. the id seen from the pid namespace of
161 * current.
Pavel Emelyanov7af57292007-10-18 23:40:06 -0700162 * pid_nr_ns() : id seen from the ns specified.
163 *
164 * see also task_xid_nr() etc in include/linux/sched.h
165 */
166
Eric W. Biederman5feb8f52006-10-02 02:17:12 -0700167static inline pid_t pid_nr(struct pid *pid)
168{
169 pid_t nr = 0;
170 if (pid)
Pavel Emelyanov7af57292007-10-18 23:40:06 -0700171 nr = pid->numbers[0].nr;
172 return nr;
173}
174
175pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns);
Eric W. Biederman44c4e1b2008-02-08 04:19:15 -0800176pid_t pid_vnr(struct pid *pid);
Eric W. Biederman5feb8f52006-10-02 02:17:12 -0700177
Andrew Morton1d328492006-10-03 01:13:45 -0700178#define do_each_pid_task(pid, type, task) \
179 do { \
Steven Rostedt5ef64762008-12-04 00:26:39 -0500180 if ((pid) != NULL) \
Sasha Levinb67bfe02013-02-27 17:06:00 -0800181 hlist_for_each_entry_rcu((task), \
Steven Rostedt5ef64762008-12-04 00:26:39 -0500182 &(pid)->tasks[type], pids[type].node) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183
Oleg Nesterov46f382d2008-02-08 04:19:19 -0800184 /*
185 * Both old and new leaders may be attached to
186 * the same pid in the middle of de_thread().
187 */
Andrew Morton1d328492006-10-03 01:13:45 -0700188#define while_each_pid_task(pid, type, task) \
Oleg Nesterov46f382d2008-02-08 04:19:19 -0800189 if (type == PIDTYPE_PID) \
190 break; \
Andrew Morton1d328492006-10-03 01:13:45 -0700191 } \
Oleg Nesterovd387cae2006-10-02 02:17:22 -0700192 } while (0)
Eric W. Biederman558cb322006-10-02 02:17:09 -0700193
Ken Chen2d70b682008-08-20 14:09:17 -0700194#define do_each_pid_thread(pid, type, task) \
195 do_each_pid_task(pid, type, task) { \
196 struct task_struct *tg___ = task; \
Tetsuo Handae3b5a342017-02-27 14:27:37 -0800197 for_each_thread(tg___, task) {
Ken Chen2d70b682008-08-20 14:09:17 -0700198
199#define while_each_pid_thread(pid, type, task) \
Tetsuo Handae3b5a342017-02-27 14:27:37 -0800200 } \
Ken Chen2d70b682008-08-20 14:09:17 -0700201 task = tg___; \
202 } while_each_pid_task(pid, type, task)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700203#endif /* _LINUX_PID_H */