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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 | ||
b2d09103 | 5 | #include <linux/rculist.h> |
92476d7f | 6 | |
1da177e4 LT |
7 | enum pid_type |
8 | { | |
9 | PIDTYPE_PID, | |
6883f81a | 10 | PIDTYPE_TGID, |
1da177e4 LT |
11 | PIDTYPE_PGID, |
12 | PIDTYPE_SID, | |
dd1c1f2f | 13 | PIDTYPE_MAX, |
1da177e4 LT |
14 | }; |
15 | ||
92476d7f EB |
16 | /* |
17 | * What is struct pid? | |
18 | * | |
19 | * A struct pid is the kernel's internal notion of a process identifier. | |
20 | * It refers to individual tasks, process groups, and sessions. While | |
21 | * there are processes attached to it the struct pid lives in a hash | |
22 | * table, so it and then the processes that it refers to can be found | |
23 | * quickly from the numeric pid value. The attached processes may be | |
24 | * quickly accessed by following pointers from struct pid. | |
25 | * | |
25985edc | 26 | * Storing pid_t values in the kernel and referring to them later has a |
92476d7f EB |
27 | * problem. The process originally with that pid may have exited and the |
28 | * pid allocator wrapped, and another process could have come along | |
29 | * and been assigned that pid. | |
30 | * | |
31 | * Referring to user space processes by holding a reference to struct | |
32 | * task_struct has a problem. When the user space process exits | |
33 | * the now useless task_struct is still kept. A task_struct plus a | |
34 | * stack consumes around 10K of low kernel memory. More precisely | |
35 | * this is THREAD_SIZE + sizeof(struct task_struct). By comparison | |
36 | * a struct pid is about 64 bytes. | |
37 | * | |
38 | * Holding a reference to struct pid solves both of these problems. | |
39 | * It is small so holding a reference does not consume a lot of | |
84d73786 SB |
40 | * resources, and since a new struct pid is allocated when the numeric pid |
41 | * value is reused (when pids wrap around) we don't mistakenly refer to new | |
42 | * processes. | |
92476d7f EB |
43 | */ |
44 | ||
4c3f2ead SB |
45 | |
46 | /* | |
47 | * struct upid is used to get the id of the struct pid, as it is | |
48 | * seen in particular namespace. Later the struct pid is found with | |
49 | * find_pid_ns() using the int nr and struct pid_namespace *ns. | |
50 | */ | |
51 | ||
52 | struct upid { | |
4c3f2ead SB |
53 | int nr; |
54 | struct pid_namespace *ns; | |
4c3f2ead SB |
55 | }; |
56 | ||
1da177e4 LT |
57 | struct pid |
58 | { | |
92476d7f | 59 | atomic_t count; |
33166b1f | 60 | unsigned int level; |
92476d7f EB |
61 | /* lists of tasks that use this pid */ |
62 | struct hlist_head tasks[PIDTYPE_MAX]; | |
63 | struct rcu_head rcu; | |
4c3f2ead | 64 | struct upid numbers[1]; |
1da177e4 LT |
65 | }; |
66 | ||
820e45db SB |
67 | extern struct pid init_struct_pid; |
68 | ||
92476d7f EB |
69 | static inline struct pid *get_pid(struct pid *pid) |
70 | { | |
71 | if (pid) | |
72 | atomic_inc(&pid->count); | |
73 | return pid; | |
74 | } | |
75 | ||
b3c97528 HH |
76 | extern void put_pid(struct pid *pid); |
77 | extern struct task_struct *pid_task(struct pid *pid, enum pid_type); | |
78 | extern struct task_struct *get_pid_task(struct pid *pid, enum pid_type); | |
1da177e4 | 79 | |
1a657f78 ON |
80 | extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type); |
81 | ||
1da177e4 | 82 | /* |
81907739 | 83 | * these helpers must be called with the tasklist_lock write-held. |
1da177e4 | 84 | */ |
81907739 | 85 | extern void attach_pid(struct task_struct *task, enum pid_type); |
b3c97528 | 86 | extern void detach_pid(struct task_struct *task, enum pid_type); |
24336eae ON |
87 | extern void change_pid(struct task_struct *task, enum pid_type, |
88 | struct pid *pid); | |
b3c97528 HH |
89 | extern void transfer_pid(struct task_struct *old, struct task_struct *new, |
90 | enum pid_type); | |
1da177e4 | 91 | |
198fe21b PE |
92 | struct pid_namespace; |
93 | extern struct pid_namespace init_pid_ns; | |
94 | ||
1da177e4 LT |
95 | /* |
96 | * look up a PID in the hash table. Must be called with the tasklist_lock | |
92476d7f | 97 | * or rcu_read_lock() held. |
198fe21b PE |
98 | * |
99 | * find_pid_ns() finds the pid in the namespace specified | |
26498e89 | 100 | * find_vpid() finds the pid by its virtual id, i.e. in the current namespace |
198fe21b | 101 | * |
dbda0de5 | 102 | * see also find_task_by_vpid() set in include/linux/sched.h |
92476d7f | 103 | */ |
b3c97528 | 104 | extern struct pid *find_pid_ns(int nr, struct pid_namespace *ns); |
8990571e | 105 | extern struct pid *find_vpid(int nr); |
92476d7f EB |
106 | |
107 | /* | |
108 | * Lookup a PID in the hash table, and return with it's count elevated. | |
1da177e4 | 109 | */ |
92476d7f | 110 | extern struct pid *find_get_pid(int nr); |
198fe21b | 111 | extern struct pid *find_ge_pid(int nr, struct pid_namespace *); |
c78193e9 | 112 | int next_pidmap(struct pid_namespace *pid_ns, unsigned int last); |
1da177e4 | 113 | |
8ef047aa | 114 | extern struct pid *alloc_pid(struct pid_namespace *ns); |
b3c97528 | 115 | extern void free_pid(struct pid *pid); |
c876ad76 | 116 | extern void disable_pid_allocation(struct pid_namespace *ns); |
1da177e4 | 117 | |
f9fb860f EB |
118 | /* |
119 | * ns_of_pid() returns the pid namespace in which the specified pid was | |
120 | * allocated. | |
121 | * | |
122 | * NOTE: | |
123 | * ns_of_pid() is expected to be called for a process (task) that has | |
124 | * an attached 'struct pid' (see attach_pid(), detach_pid()) i.e @pid | |
125 | * is expected to be non-NULL. If @pid is NULL, caller should handle | |
126 | * the resulting NULL pid-ns. | |
127 | */ | |
128 | static inline struct pid_namespace *ns_of_pid(struct pid *pid) | |
129 | { | |
130 | struct pid_namespace *ns = NULL; | |
131 | if (pid) | |
132 | ns = pid->numbers[pid->level].ns; | |
133 | return ns; | |
134 | } | |
135 | ||
45a68628 EB |
136 | /* |
137 | * is_child_reaper returns true if the pid is the init process | |
138 | * of the current namespace. As this one could be checked before | |
139 | * pid_ns->child_reaper is assigned in copy_process, we check | |
140 | * with the pid number. | |
141 | */ | |
142 | static inline bool is_child_reaper(struct pid *pid) | |
143 | { | |
144 | return pid->numbers[pid->level].nr == 1; | |
145 | } | |
146 | ||
7af57294 PE |
147 | /* |
148 | * the helpers to get the pid's id seen from different namespaces | |
149 | * | |
150 | * pid_nr() : global id, i.e. the id seen from the init namespace; | |
44c4e1b2 EB |
151 | * pid_vnr() : virtual id, i.e. the id seen from the pid namespace of |
152 | * current. | |
7af57294 PE |
153 | * pid_nr_ns() : id seen from the ns specified. |
154 | * | |
155 | * see also task_xid_nr() etc in include/linux/sched.h | |
156 | */ | |
157 | ||
5feb8f5f EB |
158 | static inline pid_t pid_nr(struct pid *pid) |
159 | { | |
160 | pid_t nr = 0; | |
161 | if (pid) | |
7af57294 PE |
162 | nr = pid->numbers[0].nr; |
163 | return nr; | |
164 | } | |
165 | ||
166 | pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns); | |
44c4e1b2 | 167 | pid_t pid_vnr(struct pid *pid); |
5feb8f5f | 168 | |
1d32849b AM |
169 | #define do_each_pid_task(pid, type, task) \ |
170 | do { \ | |
5ef64761 | 171 | if ((pid) != NULL) \ |
b67bfe0d | 172 | hlist_for_each_entry_rcu((task), \ |
2c470475 | 173 | &(pid)->tasks[type], pid_links[type]) { |
d387cae0 | 174 | |
46f382d2 ON |
175 | /* |
176 | * Both old and new leaders may be attached to | |
177 | * the same pid in the middle of de_thread(). | |
178 | */ | |
1d32849b | 179 | #define while_each_pid_task(pid, type, task) \ |
46f382d2 ON |
180 | if (type == PIDTYPE_PID) \ |
181 | break; \ | |
1d32849b | 182 | } \ |
d387cae0 | 183 | } while (0) |
558cb325 | 184 | |
2d70b68d KC |
185 | #define do_each_pid_thread(pid, type, task) \ |
186 | do_each_pid_task(pid, type, task) { \ | |
187 | struct task_struct *tg___ = task; \ | |
e3b5a342 | 188 | for_each_thread(tg___, task) { |
2d70b68d KC |
189 | |
190 | #define while_each_pid_thread(pid, type, task) \ | |
e3b5a342 | 191 | } \ |
2d70b68d KC |
192 | task = tg___; \ |
193 | } while_each_pid_task(pid, type, task) | |
1da177e4 | 194 | #endif /* _LINUX_PID_H */ |