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 */
33 struct completion;
34 struct ctl_table;
35 struct nsproxy;
36 struct ctl_table_root;
37 struct ctl_table_header;
38 struct ctl_dir;
39 
40 typedef int proc_handler (struct ctl_table *ctl, int write,
41 			  void __user *buffer, size_t *lenp, loff_t *ppos);
42 
43 extern int proc_dostring(struct ctl_table *, int,
44 			 void __user *, size_t *, loff_t *);
45 extern int proc_dointvec(struct ctl_table *, int,
46 			 void __user *, size_t *, loff_t *);
47 extern int proc_douintvec(struct ctl_table *, int,
48 			 void __user *, size_t *, loff_t *);
49 extern int proc_dointvec_minmax(struct ctl_table *, int,
50 				void __user *, size_t *, loff_t *);
51 extern int proc_douintvec_minmax(struct ctl_table *table, int write,
52 				 void __user *buffer, size_t *lenp,
53 				 loff_t *ppos);
54 extern int proc_dointvec_jiffies(struct ctl_table *, int,
55 				 void __user *, size_t *, loff_t *);
56 extern int proc_dointvec_userhz_jiffies(struct ctl_table *, int,
57 					void __user *, size_t *, loff_t *);
58 extern int proc_dointvec_ms_jiffies(struct ctl_table *, int,
59 				    void __user *, size_t *, loff_t *);
60 extern int proc_doulongvec_minmax(struct ctl_table *, int,
61 				  void __user *, size_t *, loff_t *);
62 extern int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int,
63 				      void __user *, size_t *, loff_t *);
64 extern 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 */
95 struct ctl_table_poll {
96 	atomic_t event;
97 	wait_queue_head_t wait;
98 };
99 
proc_sys_poll_event(struct ctl_table_poll * poll)100 static 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: */
113 struct 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 
126 struct 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. */
133 struct 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 
153 struct 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 
159 struct ctl_table_set {
160 	int (*is_seen)(struct ctl_table_set *);
161 	struct ctl_dir dir;
162 };
163 
164 struct 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 */
174 struct ctl_path {
175 	const char *procname;
176 };
177 
178 #ifdef CONFIG_SYSCTL
179 
180 void proc_sys_poll_notify(struct ctl_table_poll *poll);
181 
182 extern void setup_sysctl_set(struct ctl_table_set *p,
183 	struct ctl_table_root *root,
184 	int (*is_seen)(struct ctl_table_set *));
185 extern void retire_sysctl_set(struct ctl_table_set *set);
186 
187 struct ctl_table_header *__register_sysctl_table(
188 	struct ctl_table_set *set,
189 	const char *path, struct ctl_table *table);
190 struct ctl_table_header *__register_sysctl_paths(
191 	struct ctl_table_set *set,
192 	const struct ctl_path *path, struct ctl_table *table);
193 struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table);
194 struct ctl_table_header *register_sysctl_table(struct ctl_table * table);
195 struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
196 						struct ctl_table *table);
197 
198 void unregister_sysctl_table(struct ctl_table_header * table);
199 
200 extern int sysctl_init(void);
201 extern void __register_sysctl_init(const char *path, struct ctl_table *table,
202 				 const char *table_name);
203 #define register_sysctl_init(path, table) __register_sysctl_init(path, table, #table)
204 
205 extern struct ctl_table sysctl_mount_point[];
206 
207 #else /* CONFIG_SYSCTL */
register_sysctl_table(struct ctl_table * table)208 static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
209 {
210 	return NULL;
211 }
212 
register_sysctl_paths(const struct ctl_path * path,struct ctl_table * table)213 static inline struct ctl_table_header *register_sysctl_paths(
214 			const struct ctl_path *path, struct ctl_table *table)
215 {
216 	return NULL;
217 }
218 
register_sysctl(const char * path,struct ctl_table * table)219 static inline struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
220 {
221 	return NULL;
222 }
223 
unregister_sysctl_table(struct ctl_table_header * table)224 static inline void unregister_sysctl_table(struct ctl_table_header * table)
225 {
226 }
227 
setup_sysctl_set(struct ctl_table_set * p,struct ctl_table_root * root,int (* is_seen)(struct ctl_table_set *))228 static inline void setup_sysctl_set(struct ctl_table_set *p,
229 	struct ctl_table_root *root,
230 	int (*is_seen)(struct ctl_table_set *))
231 {
232 }
233 
234 #endif /* CONFIG_SYSCTL */
235 
236 int sysctl_max_threads(struct ctl_table *table, int write,
237 		       void __user *buffer, size_t *lenp, loff_t *ppos);
238 
239 #endif /* _LINUX_SYSCTL_H */
240