1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * sysctl.h: General linux system control interface
4 *
5 * Begun 24 March 1995, Stephen Tweedie
6 *
7 ****************************************************************
8 ****************************************************************
9 **
10 ** WARNING:
11 ** The values in this file are exported to user space via
12 ** the sysctl() binary interface. Do *NOT* change the
13 ** numbering of any existing values here, and do not change
14 ** any numbers within any one set of values. If you have to
15 ** redefine an existing interface, use a new number for it.
16 ** The kernel will then return -ENOTDIR to any application using
17 ** the old binary interface.
18 **
19 ****************************************************************
20 ****************************************************************
21 */
22#ifndef _LINUX_SYSCTL_H
23#define _LINUX_SYSCTL_H
24
25#include <linux/list.h>
26#include <linux/rcupdate.h>
27#include <linux/wait.h>
28#include <linux/rbtree.h>
29#include <linux/uidgid.h>
30#include <uapi/linux/sysctl.h>
31
32/* For the /proc/sys support */
33struct completion;
34struct ctl_table;
35struct nsproxy;
36struct ctl_table_root;
37struct ctl_table_header;
38struct ctl_dir;
39
40typedef int proc_handler (struct ctl_table *ctl, int write,
41 void __user *buffer, size_t *lenp, loff_t *ppos);
42
43extern int proc_dostring(struct ctl_table *, int,
44 void __user *, size_t *, loff_t *);
45extern int proc_dointvec(struct ctl_table *, int,
46 void __user *, size_t *, loff_t *);
47extern int proc_douintvec(struct ctl_table *, int,
48 void __user *, size_t *, loff_t *);
49extern int proc_dointvec_minmax(struct ctl_table *, int,
50 void __user *, size_t *, loff_t *);
51extern int proc_douintvec_minmax(struct ctl_table *table, int write,
52 void __user *buffer, size_t *lenp,
53 loff_t *ppos);
54extern int proc_dointvec_jiffies(struct ctl_table *, int,
55 void __user *, size_t *, loff_t *);
56extern int proc_dointvec_userhz_jiffies(struct ctl_table *, int,
57 void __user *, size_t *, loff_t *);
58extern int proc_dointvec_ms_jiffies(struct ctl_table *, int,
59 void __user *, size_t *, loff_t *);
60extern int proc_doulongvec_minmax(struct ctl_table *, int,
61 void __user *, size_t *, loff_t *);
62extern int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int,
63 void __user *, size_t *, loff_t *);
64extern int proc_do_large_bitmap(struct ctl_table *, int,
65 void __user *, size_t *, loff_t *);
66
67/*
68 * Register a set of sysctl names by calling register_sysctl_table
69 * with an initialised array of struct ctl_table's. An entry with
70 * NULL procname terminates the table. table->de will be
71 * set up by the registration and need not be initialised in advance.
72 *
73 * sysctl names can be mirrored automatically under /proc/sys. The
74 * procname supplied controls /proc naming.
75 *
76 * The table's mode will be honoured both for sys_sysctl(2) and
77 * proc-fs access.
78 *
79 * Leaf nodes in the sysctl tree will be represented by a single file
80 * under /proc; non-leaf nodes will be represented by directories. A
81 * null procname disables /proc mirroring at this node.
82 *
83 * sysctl(2) can automatically manage read and write requests through
84 * the sysctl table. The data and maxlen fields of the ctl_table
85 * struct enable minimal validation of the values being written to be
86 * performed, and the mode field allows minimal authentication.
87 *
88 * There must be a proc_handler routine for any terminal nodes
89 * mirrored under /proc/sys (non-terminals are handled by a built-in
90 * directory handler). Several default handlers are available to
91 * cover common cases.
92 */
93
94/* Support for userspace poll() to watch for changes */
95struct ctl_table_poll {
96 atomic_t event;
97 wait_queue_head_t wait;
98};
99
100static inline void *proc_sys_poll_event(struct ctl_table_poll *poll)
101{
102 return (void *)(unsigned long)atomic_read(&poll->event);
103}
104
105#define __CTL_TABLE_POLL_INITIALIZER(name) { \
106 .event = ATOMIC_INIT(0), \
107 .wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.wait) }
108
109#define DEFINE_CTL_TABLE_POLL(name) \
110 struct ctl_table_poll name = __CTL_TABLE_POLL_INITIALIZER(name)
111
112/* A sysctl table is an array of struct ctl_table: */
113struct ctl_table
114{
115 const char *procname; /* Text ID for /proc/sys, or zero */
116 void *data;
117 int maxlen;
118 umode_t mode;
119 struct ctl_table *child; /* Deprecated */
120 proc_handler *proc_handler; /* Callback for text formatting */
121 struct ctl_table_poll *poll;
122 void *extra1;
123 void *extra2;
124} __randomize_layout;
125
126struct ctl_node {
127 struct rb_node node;
128 struct ctl_table_header *header;
129};
130
131/* struct ctl_table_header is used to maintain dynamic lists of
132 struct ctl_table trees. */
133struct ctl_table_header
134{
135 union {
136 struct {
137 struct ctl_table *ctl_table;
138 int used;
139 int count;
140 int nreg;
141 };
142 struct rcu_head rcu;
143 };
144 struct completion *unregistering;
145 struct ctl_table *ctl_table_arg;
146 struct ctl_table_root *root;
147 struct ctl_table_set *set;
148 struct ctl_dir *parent;
149 struct ctl_node *node;
150 struct hlist_head inodes; /* head for proc_inode->sysctl_inodes */
151};
152
153struct ctl_dir {
154 /* Header must be at the start of ctl_dir */
155 struct ctl_table_header header;
156 struct rb_root root;
157};
158
159struct ctl_table_set {
160 int (*is_seen)(struct ctl_table_set *);
161 struct ctl_dir dir;
162};
163
164struct ctl_table_root {
165 struct ctl_table_set default_set;
166 struct ctl_table_set *(*lookup)(struct ctl_table_root *root);
167 void (*set_ownership)(struct ctl_table_header *head,
168 struct ctl_table *table,
169 kuid_t *uid, kgid_t *gid);
170 int (*permissions)(struct ctl_table_header *head, struct ctl_table *table);
171};
172
173/* struct ctl_path describes where in the hierarchy a table is added */
174struct ctl_path {
175 const char *procname;
176};
177
178#ifdef CONFIG_SYSCTL
179
180void proc_sys_poll_notify(struct ctl_table_poll *poll);
181
182extern void setup_sysctl_set(struct ctl_table_set *p,
183 struct ctl_table_root *root,
184 int (*is_seen)(struct ctl_table_set *));
185extern void retire_sysctl_set(struct ctl_table_set *set);
186
187struct ctl_table_header *__register_sysctl_table(
188 struct ctl_table_set *set,
189 const char *path, struct ctl_table *table);
190struct ctl_table_header *__register_sysctl_paths(
191 struct ctl_table_set *set,
192 const struct ctl_path *path, struct ctl_table *table);
193struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table);
194struct ctl_table_header *register_sysctl_table(struct ctl_table * table);
195struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
196 struct ctl_table *table);
197
198void unregister_sysctl_table(struct ctl_table_header * table);
199
200extern int sysctl_init(void);
201
202extern struct ctl_table sysctl_mount_point[];
203
204#else /* CONFIG_SYSCTL */
205static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
206{
207 return NULL;
208}
209
210static inline struct ctl_table_header *register_sysctl_paths(
211 const struct ctl_path *path, struct ctl_table *table)
212{
213 return NULL;
214}
215
216static inline struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
217{
218 return NULL;
219}
220
221static inline void unregister_sysctl_table(struct ctl_table_header * table)
222{
223}
224
225static inline void setup_sysctl_set(struct ctl_table_set *p,
226 struct ctl_table_root *root,
227 int (*is_seen)(struct ctl_table_set *))
228{
229}
230
231#endif /* CONFIG_SYSCTL */
232
233int sysctl_max_threads(struct ctl_table *table, int write,
234 void __user *buffer, size_t *lenp, loff_t *ppos);
235
236#endif /* _LINUX_SYSCTL_H */
237