Commit | Line | Data |
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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> |
b53b0b9d | 6 | #include <linux/wait.h> |
f57e515a | 7 | #include <linux/refcount.h> |
92476d7f | 8 | |
1da177e4 LT |
9 | enum pid_type |
10 | { | |
11 | PIDTYPE_PID, | |
6883f81a | 12 | PIDTYPE_TGID, |
1da177e4 LT |
13 | PIDTYPE_PGID, |
14 | PIDTYPE_SID, | |
dd1c1f2f | 15 | PIDTYPE_MAX, |
1da177e4 LT |
16 | }; |
17 | ||
92476d7f EB |
18 | /* |
19 | * What is struct pid? | |
20 | * | |
21 | * A struct pid is the kernel's internal notion of a process identifier. | |
22 | * It refers to individual tasks, process groups, and sessions. While | |
23 | * there are processes attached to it the struct pid lives in a hash | |
24 | * table, so it and then the processes that it refers to can be found | |
25 | * quickly from the numeric pid value. The attached processes may be | |
26 | * quickly accessed by following pointers from struct pid. | |
27 | * | |
25985edc | 28 | * Storing pid_t values in the kernel and referring to them later has a |
92476d7f EB |
29 | * problem. The process originally with that pid may have exited and the |
30 | * pid allocator wrapped, and another process could have come along | |
31 | * and been assigned that pid. | |
32 | * | |
33 | * Referring to user space processes by holding a reference to struct | |
34 | * task_struct has a problem. When the user space process exits | |
35 | * the now useless task_struct is still kept. A task_struct plus a | |
36 | * stack consumes around 10K of low kernel memory. More precisely | |
37 | * this is THREAD_SIZE + sizeof(struct task_struct). By comparison | |
38 | * a struct pid is about 64 bytes. | |
39 | * | |
40 | * Holding a reference to struct pid solves both of these problems. | |
41 | * It is small so holding a reference does not consume a lot of | |
84d73786 SB |
42 | * resources, and since a new struct pid is allocated when the numeric pid |
43 | * value is reused (when pids wrap around) we don't mistakenly refer to new | |
44 | * processes. | |
92476d7f EB |
45 | */ |
46 | ||
4c3f2ead SB |
47 | |
48 | /* | |
49 | * struct upid is used to get the id of the struct pid, as it is | |
50 | * seen in particular namespace. Later the struct pid is found with | |
51 | * find_pid_ns() using the int nr and struct pid_namespace *ns. | |
52 | */ | |
53 | ||
54 | struct upid { | |
4c3f2ead SB |
55 | int nr; |
56 | struct pid_namespace *ns; | |
4c3f2ead SB |
57 | }; |
58 | ||
1da177e4 LT |
59 | struct pid |
60 | { | |
f57e515a | 61 | refcount_t count; |
33166b1f | 62 | unsigned int level; |
92476d7f EB |
63 | /* lists of tasks that use this pid */ |
64 | struct hlist_head tasks[PIDTYPE_MAX]; | |
7bc3e6e5 | 65 | struct hlist_head inodes; |
b53b0b9d JFG |
66 | /* wait queue for pidfd notifications */ |
67 | wait_queue_head_t wait_pidfd; | |
92476d7f | 68 | struct rcu_head rcu; |
4c3f2ead | 69 | struct upid numbers[1]; |
1da177e4 LT |
70 | }; |
71 | ||
820e45db SB |
72 | extern struct pid init_struct_pid; |
73 | ||
b3e58382 CB |
74 | extern const struct file_operations pidfd_fops; |
75 | ||
3695eae5 CB |
76 | struct file; |
77 | ||
78 | extern struct pid *pidfd_pid(const struct file *file); | |
79 | ||
92476d7f EB |
80 | static inline struct pid *get_pid(struct pid *pid) |
81 | { | |
82 | if (pid) | |
f57e515a | 83 | refcount_inc(&pid->count); |
92476d7f EB |
84 | return pid; |
85 | } | |
86 | ||
b3c97528 HH |
87 | extern void put_pid(struct pid *pid); |
88 | extern struct task_struct *pid_task(struct pid *pid, enum pid_type); | |
3d6d8da4 CB |
89 | static inline bool pid_has_task(struct pid *pid, enum pid_type type) |
90 | { | |
91 | return !hlist_empty(&pid->tasks[type]); | |
92 | } | |
b3c97528 | 93 | extern struct task_struct *get_pid_task(struct pid *pid, enum pid_type); |
1da177e4 | 94 | |
1a657f78 ON |
95 | extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type); |
96 | ||
1da177e4 | 97 | /* |
81907739 | 98 | * these helpers must be called with the tasklist_lock write-held. |
1da177e4 | 99 | */ |
81907739 | 100 | extern void attach_pid(struct task_struct *task, enum pid_type); |
b3c97528 | 101 | extern void detach_pid(struct task_struct *task, enum pid_type); |
24336eae ON |
102 | extern void change_pid(struct task_struct *task, enum pid_type, |
103 | struct pid *pid); | |
b3c97528 HH |
104 | extern void transfer_pid(struct task_struct *old, struct task_struct *new, |
105 | enum pid_type); | |
1da177e4 | 106 | |
198fe21b PE |
107 | struct pid_namespace; |
108 | extern struct pid_namespace init_pid_ns; | |
109 | ||
1da177e4 LT |
110 | /* |
111 | * look up a PID in the hash table. Must be called with the tasklist_lock | |
92476d7f | 112 | * or rcu_read_lock() held. |
198fe21b PE |
113 | * |
114 | * find_pid_ns() finds the pid in the namespace specified | |
26498e89 | 115 | * find_vpid() finds the pid by its virtual id, i.e. in the current namespace |
198fe21b | 116 | * |
dbda0de5 | 117 | * see also find_task_by_vpid() set in include/linux/sched.h |
92476d7f | 118 | */ |
b3c97528 | 119 | extern struct pid *find_pid_ns(int nr, struct pid_namespace *ns); |
8990571e | 120 | extern struct pid *find_vpid(int nr); |
92476d7f EB |
121 | |
122 | /* | |
123 | * Lookup a PID in the hash table, and return with it's count elevated. | |
1da177e4 | 124 | */ |
92476d7f | 125 | extern struct pid *find_get_pid(int nr); |
198fe21b | 126 | extern struct pid *find_ge_pid(int nr, struct pid_namespace *); |
1da177e4 | 127 | |
49cb2fc4 AR |
128 | extern struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid, |
129 | size_t set_tid_size); | |
b3c97528 | 130 | extern void free_pid(struct pid *pid); |
c876ad76 | 131 | extern void disable_pid_allocation(struct pid_namespace *ns); |
1da177e4 | 132 | |
f9fb860f EB |
133 | /* |
134 | * ns_of_pid() returns the pid namespace in which the specified pid was | |
135 | * allocated. | |
136 | * | |
137 | * NOTE: | |
138 | * ns_of_pid() is expected to be called for a process (task) that has | |
139 | * an attached 'struct pid' (see attach_pid(), detach_pid()) i.e @pid | |
140 | * is expected to be non-NULL. If @pid is NULL, caller should handle | |
141 | * the resulting NULL pid-ns. | |
142 | */ | |
143 | static inline struct pid_namespace *ns_of_pid(struct pid *pid) | |
144 | { | |
145 | struct pid_namespace *ns = NULL; | |
146 | if (pid) | |
147 | ns = pid->numbers[pid->level].ns; | |
148 | return ns; | |
149 | } | |
150 | ||
45a68628 EB |
151 | /* |
152 | * is_child_reaper returns true if the pid is the init process | |
153 | * of the current namespace. As this one could be checked before | |
154 | * pid_ns->child_reaper is assigned in copy_process, we check | |
155 | * with the pid number. | |
156 | */ | |
157 | static inline bool is_child_reaper(struct pid *pid) | |
158 | { | |
159 | return pid->numbers[pid->level].nr == 1; | |
160 | } | |
161 | ||
7af57294 PE |
162 | /* |
163 | * the helpers to get the pid's id seen from different namespaces | |
164 | * | |
165 | * pid_nr() : global id, i.e. the id seen from the init namespace; | |
44c4e1b2 EB |
166 | * pid_vnr() : virtual id, i.e. the id seen from the pid namespace of |
167 | * current. | |
7af57294 PE |
168 | * pid_nr_ns() : id seen from the ns specified. |
169 | * | |
170 | * see also task_xid_nr() etc in include/linux/sched.h | |
171 | */ | |
172 | ||
5feb8f5f EB |
173 | static inline pid_t pid_nr(struct pid *pid) |
174 | { | |
175 | pid_t nr = 0; | |
176 | if (pid) | |
7af57294 PE |
177 | nr = pid->numbers[0].nr; |
178 | return nr; | |
179 | } | |
180 | ||
181 | pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns); | |
44c4e1b2 | 182 | pid_t pid_vnr(struct pid *pid); |
5feb8f5f | 183 | |
1d32849b AM |
184 | #define do_each_pid_task(pid, type, task) \ |
185 | do { \ | |
5ef64761 | 186 | if ((pid) != NULL) \ |
b67bfe0d | 187 | hlist_for_each_entry_rcu((task), \ |
2c470475 | 188 | &(pid)->tasks[type], pid_links[type]) { |
d387cae0 | 189 | |
46f382d2 ON |
190 | /* |
191 | * Both old and new leaders may be attached to | |
192 | * the same pid in the middle of de_thread(). | |
193 | */ | |
1d32849b | 194 | #define while_each_pid_task(pid, type, task) \ |
46f382d2 ON |
195 | if (type == PIDTYPE_PID) \ |
196 | break; \ | |
1d32849b | 197 | } \ |
d387cae0 | 198 | } while (0) |
558cb325 | 199 | |
2d70b68d KC |
200 | #define do_each_pid_thread(pid, type, task) \ |
201 | do_each_pid_task(pid, type, task) { \ | |
202 | struct task_struct *tg___ = task; \ | |
e3b5a342 | 203 | for_each_thread(tg___, task) { |
2d70b68d KC |
204 | |
205 | #define while_each_pid_thread(pid, type, task) \ | |
e3b5a342 | 206 | } \ |
2d70b68d KC |
207 | task = tg___; \ |
208 | } while_each_pid_task(pid, type, task) | |
1da177e4 | 209 | #endif /* _LINUX_PID_H */ |