xref: /openbmc/linux/include/linux/sysctl.h (revision f3539c12d8196ce0a1993364d30b3a18908470d1)
1 /*
2  * sysctl.h: General linux system control interface
3  *
4  * Begun 24 March 1995, Stephen Tweedie
5  *
6  ****************************************************************
7  ****************************************************************
8  **
9  **  WARNING:
10  **  The values in this file are exported to user space via
11  **  the sysctl() binary interface.  Do *NOT* change the
12  **  numbering of any existing values here, and do not change
13  **  any numbers within any one set of values.  If you have to
14  **  redefine an existing interface, use a new number for it.
15  **  The kernel will then return -ENOTDIR to any application using
16  **  the old binary interface.
17  **
18  ****************************************************************
19  ****************************************************************
20  */
21 #ifndef _LINUX_SYSCTL_H
22 #define _LINUX_SYSCTL_H
23 
24 #include <linux/list.h>
25 #include <linux/rcupdate.h>
26 #include <linux/wait.h>
27 #include <linux/rbtree.h>
28 #include <uapi/linux/sysctl.h>
29 
30 /* For the /proc/sys support */
31 struct completion;
32 struct ctl_table;
33 struct nsproxy;
34 struct ctl_table_root;
35 struct ctl_table_header;
36 struct ctl_dir;
37 
38 typedef int proc_handler (struct ctl_table *ctl, int write,
39 			  void __user *buffer, size_t *lenp, loff_t *ppos);
40 
41 extern int proc_dostring(struct ctl_table *, int,
42 			 void __user *, size_t *, loff_t *);
43 extern int proc_dointvec(struct ctl_table *, int,
44 			 void __user *, size_t *, loff_t *);
45 extern int proc_douintvec(struct ctl_table *, int,
46 			 void __user *, size_t *, loff_t *);
47 extern int proc_dointvec_minmax(struct ctl_table *, int,
48 				void __user *, size_t *, loff_t *);
49 extern int proc_dointvec_jiffies(struct ctl_table *, int,
50 				 void __user *, size_t *, loff_t *);
51 extern int proc_dointvec_userhz_jiffies(struct ctl_table *, int,
52 					void __user *, size_t *, loff_t *);
53 extern int proc_dointvec_ms_jiffies(struct ctl_table *, int,
54 				    void __user *, size_t *, loff_t *);
55 extern int proc_doulongvec_minmax(struct ctl_table *, int,
56 				  void __user *, size_t *, loff_t *);
57 extern int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int,
58 				      void __user *, size_t *, loff_t *);
59 extern int proc_do_large_bitmap(struct ctl_table *, int,
60 				void __user *, size_t *, loff_t *);
61 
62 /*
63  * Register a set of sysctl names by calling register_sysctl_table
64  * with an initialised array of struct ctl_table's.  An entry with
65  * NULL procname terminates the table.  table->de will be
66  * set up by the registration and need not be initialised in advance.
67  *
68  * sysctl names can be mirrored automatically under /proc/sys.  The
69  * procname supplied controls /proc naming.
70  *
71  * The table's mode will be honoured both for sys_sysctl(2) and
72  * proc-fs access.
73  *
74  * Leaf nodes in the sysctl tree will be represented by a single file
75  * under /proc; non-leaf nodes will be represented by directories.  A
76  * null procname disables /proc mirroring at this node.
77  *
78  * sysctl(2) can automatically manage read and write requests through
79  * the sysctl table.  The data and maxlen fields of the ctl_table
80  * struct enable minimal validation of the values being written to be
81  * performed, and the mode field allows minimal authentication.
82  *
83  * There must be a proc_handler routine for any terminal nodes
84  * mirrored under /proc/sys (non-terminals are handled by a built-in
85  * directory handler).  Several default handlers are available to
86  * cover common cases.
87  */
88 
89 /* Support for userspace poll() to watch for changes */
90 struct ctl_table_poll {
91 	atomic_t event;
92 	wait_queue_head_t wait;
93 };
94 
95 static inline void *proc_sys_poll_event(struct ctl_table_poll *poll)
96 {
97 	return (void *)(unsigned long)atomic_read(&poll->event);
98 }
99 
100 #define __CTL_TABLE_POLL_INITIALIZER(name) {				\
101 	.event = ATOMIC_INIT(0),					\
102 	.wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.wait) }
103 
104 #define DEFINE_CTL_TABLE_POLL(name)					\
105 	struct ctl_table_poll name = __CTL_TABLE_POLL_INITIALIZER(name)
106 
107 /* A sysctl table is an array of struct ctl_table: */
108 struct ctl_table
109 {
110 	const char *procname;		/* Text ID for /proc/sys, or zero */
111 	void *data;
112 	int maxlen;
113 	umode_t mode;
114 	struct ctl_table *child;	/* Deprecated */
115 	proc_handler *proc_handler;	/* Callback for text formatting */
116 	struct ctl_table_poll *poll;
117 	void *extra1;
118 	void *extra2;
119 };
120 
121 struct ctl_node {
122 	struct rb_node node;
123 	struct ctl_table_header *header;
124 };
125 
126 /* struct ctl_table_header is used to maintain dynamic lists of
127    struct ctl_table trees. */
128 struct ctl_table_header
129 {
130 	union {
131 		struct {
132 			struct ctl_table *ctl_table;
133 			int used;
134 			int count;
135 			int nreg;
136 		};
137 		struct rcu_head rcu;
138 	};
139 	struct completion *unregistering;
140 	struct ctl_table *ctl_table_arg;
141 	struct ctl_table_root *root;
142 	struct ctl_table_set *set;
143 	struct ctl_dir *parent;
144 	struct ctl_node *node;
145 };
146 
147 struct ctl_dir {
148 	/* Header must be at the start of ctl_dir */
149 	struct ctl_table_header header;
150 	struct rb_root root;
151 };
152 
153 struct ctl_table_set {
154 	int (*is_seen)(struct ctl_table_set *);
155 	struct ctl_dir dir;
156 };
157 
158 struct ctl_table_root {
159 	struct ctl_table_set default_set;
160 	struct ctl_table_set *(*lookup)(struct ctl_table_root *root,
161 					   struct nsproxy *namespaces);
162 	int (*permissions)(struct ctl_table_header *head, struct ctl_table *table);
163 };
164 
165 /* struct ctl_path describes where in the hierarchy a table is added */
166 struct ctl_path {
167 	const char *procname;
168 };
169 
170 #ifdef CONFIG_SYSCTL
171 
172 void proc_sys_poll_notify(struct ctl_table_poll *poll);
173 
174 extern void setup_sysctl_set(struct ctl_table_set *p,
175 	struct ctl_table_root *root,
176 	int (*is_seen)(struct ctl_table_set *));
177 extern void retire_sysctl_set(struct ctl_table_set *set);
178 
179 void register_sysctl_root(struct ctl_table_root *root);
180 struct ctl_table_header *__register_sysctl_table(
181 	struct ctl_table_set *set,
182 	const char *path, struct ctl_table *table);
183 struct ctl_table_header *__register_sysctl_paths(
184 	struct ctl_table_set *set,
185 	const struct ctl_path *path, struct ctl_table *table);
186 struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table);
187 struct ctl_table_header *register_sysctl_table(struct ctl_table * table);
188 struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
189 						struct ctl_table *table);
190 
191 void unregister_sysctl_table(struct ctl_table_header * table);
192 
193 extern int sysctl_init(void);
194 
195 extern struct ctl_table sysctl_mount_point[];
196 
197 #else /* CONFIG_SYSCTL */
198 static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
199 {
200 	return NULL;
201 }
202 
203 static inline struct ctl_table_header *register_sysctl_paths(
204 			const struct ctl_path *path, struct ctl_table *table)
205 {
206 	return NULL;
207 }
208 
209 static inline void unregister_sysctl_table(struct ctl_table_header * table)
210 {
211 }
212 
213 static inline void setup_sysctl_set(struct ctl_table_set *p,
214 	struct ctl_table_root *root,
215 	int (*is_seen)(struct ctl_table_set *))
216 {
217 }
218 
219 #endif /* CONFIG_SYSCTL */
220 
221 int sysctl_max_threads(struct ctl_table *table, int write,
222 		       void __user *buffer, size_t *lenp, loff_t *ppos);
223 
224 #endif /* _LINUX_SYSCTL_H */
225