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 /* Keep the same order as in fs/proc/proc_sysctl.c */
41 #define SYSCTL_ZERO			((void *)&sysctl_vals[0])
42 #define SYSCTL_ONE			((void *)&sysctl_vals[1])
43 #define SYSCTL_TWO			((void *)&sysctl_vals[2])
44 #define SYSCTL_THREE			((void *)&sysctl_vals[3])
45 #define SYSCTL_FOUR			((void *)&sysctl_vals[4])
46 #define SYSCTL_ONE_HUNDRED		((void *)&sysctl_vals[5])
47 #define SYSCTL_TWO_HUNDRED		((void *)&sysctl_vals[6])
48 #define SYSCTL_ONE_THOUSAND		((void *)&sysctl_vals[7])
49 #define SYSCTL_THREE_THOUSAND		((void *)&sysctl_vals[8])
50 #define SYSCTL_INT_MAX			((void *)&sysctl_vals[9])
51 
52 /* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
53 #define SYSCTL_MAXOLDUID		((void *)&sysctl_vals[10])
54 #define SYSCTL_NEG_ONE			((void *)&sysctl_vals[11])
55 
56 extern const int sysctl_vals[];
57 
58 #define SYSCTL_LONG_ZERO	((void *)&sysctl_long_vals[0])
59 #define SYSCTL_LONG_ONE		((void *)&sysctl_long_vals[1])
60 #define SYSCTL_LONG_MAX		((void *)&sysctl_long_vals[2])
61 
62 extern const unsigned long sysctl_long_vals[];
63 
64 typedef int proc_handler(struct ctl_table *ctl, int write, void *buffer,
65 		size_t *lenp, loff_t *ppos);
66 
67 int proc_dostring(struct ctl_table *, int, void *, size_t *, loff_t *);
68 int proc_dobool(struct ctl_table *table, int write, void *buffer,
69 		size_t *lenp, loff_t *ppos);
70 int proc_dointvec(struct ctl_table *, int, void *, size_t *, loff_t *);
71 int proc_douintvec(struct ctl_table *, int, void *, size_t *, loff_t *);
72 int proc_dointvec_minmax(struct ctl_table *, int, void *, size_t *, loff_t *);
73 int proc_douintvec_minmax(struct ctl_table *table, int write, void *buffer,
74 		size_t *lenp, loff_t *ppos);
75 int proc_dou8vec_minmax(struct ctl_table *table, int write, void *buffer,
76 			size_t *lenp, loff_t *ppos);
77 int proc_dointvec_jiffies(struct ctl_table *, int, void *, size_t *, loff_t *);
78 int proc_dointvec_ms_jiffies_minmax(struct ctl_table *table, int write,
79 		void *buffer, size_t *lenp, loff_t *ppos);
80 int proc_dointvec_userhz_jiffies(struct ctl_table *, int, void *, size_t *,
81 		loff_t *);
82 int proc_dointvec_ms_jiffies(struct ctl_table *, int, void *, size_t *,
83 		loff_t *);
84 int proc_doulongvec_minmax(struct ctl_table *, int, void *, size_t *, loff_t *);
85 int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int, void *,
86 		size_t *, loff_t *);
87 int proc_do_large_bitmap(struct ctl_table *, int, void *, size_t *, loff_t *);
88 int proc_do_static_key(struct ctl_table *table, int write, void *buffer,
89 		size_t *lenp, loff_t *ppos);
90 
91 /*
92  * Register a set of sysctl names by calling register_sysctl
93  * with an initialised array of struct ctl_table's.  An entry with
94  * NULL procname terminates the table.  table->de will be
95  * set up by the registration and need not be initialised in advance.
96  *
97  * sysctl names can be mirrored automatically under /proc/sys.  The
98  * procname supplied controls /proc naming.
99  *
100  * The table's mode will be honoured for proc-fs access.
101  *
102  * Leaf nodes in the sysctl tree will be represented by a single file
103  * under /proc; non-leaf nodes will be represented by directories.  A
104  * null procname disables /proc mirroring at this node.
105  *
106  * The data and maxlen fields of the ctl_table
107  * struct enable minimal validation of the values being written to be
108  * performed, and the mode field allows minimal authentication.
109  *
110  * There must be a proc_handler routine for any terminal nodes
111  * mirrored under /proc/sys (non-terminals are handled by a built-in
112  * directory handler).  Several default handlers are available to
113  * cover common cases.
114  */
115 
116 /* Support for userspace poll() to watch for changes */
117 struct ctl_table_poll {
118 	atomic_t event;
119 	wait_queue_head_t wait;
120 };
121 
proc_sys_poll_event(struct ctl_table_poll * poll)122 static inline void *proc_sys_poll_event(struct ctl_table_poll *poll)
123 {
124 	return (void *)(unsigned long)atomic_read(&poll->event);
125 }
126 
127 #define __CTL_TABLE_POLL_INITIALIZER(name) {				\
128 	.event = ATOMIC_INIT(0),					\
129 	.wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.wait) }
130 
131 #define DEFINE_CTL_TABLE_POLL(name)					\
132 	struct ctl_table_poll name = __CTL_TABLE_POLL_INITIALIZER(name)
133 
134 /* A sysctl table is an array of struct ctl_table: */
135 struct ctl_table {
136 	const char *procname;		/* Text ID for /proc/sys, or zero */
137 	void *data;
138 	int maxlen;
139 	umode_t mode;
140 	/**
141 	 * enum type - Enumeration to differentiate between ctl target types
142 	 * @SYSCTL_TABLE_TYPE_DEFAULT: ctl target with no special considerations
143 	 * @SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY: Used to identify a permanently
144 	 *                                       empty directory target to serve
145 	 *                                       as mount point.
146 	 */
147 	enum {
148 		SYSCTL_TABLE_TYPE_DEFAULT,
149 		SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY
150 	} type;
151 	proc_handler *proc_handler;	/* Callback for text formatting */
152 	struct ctl_table_poll *poll;
153 	void *extra1;
154 	void *extra2;
155 } __randomize_layout;
156 
157 struct ctl_node {
158 	struct rb_node node;
159 	struct ctl_table_header *header;
160 };
161 
162 /**
163  * struct ctl_table_header - maintains dynamic lists of struct ctl_table trees
164  * @ctl_table: pointer to the first element in ctl_table array
165  * @ctl_table_size: number of elements pointed by @ctl_table
166  * @used: The entry will never be touched when equal to 0.
167  * @count: Upped every time something is added to @inodes and downed every time
168  *         something is removed from inodes
169  * @nreg: When nreg drops to 0 the ctl_table_header will be unregistered.
170  * @rcu: Delays the freeing of the inode. Introduced with "unfuck proc_sysctl ->d_compare()"
171  *
172  */
173 struct ctl_table_header {
174 	union {
175 		struct {
176 			struct ctl_table *ctl_table;
177 			int ctl_table_size;
178 			int used;
179 			int count;
180 			int nreg;
181 		};
182 		struct rcu_head rcu;
183 	};
184 	struct completion *unregistering;
185 	struct ctl_table *ctl_table_arg;
186 	struct ctl_table_root *root;
187 	struct ctl_table_set *set;
188 	struct ctl_dir *parent;
189 	struct ctl_node *node;
190 	struct hlist_head inodes; /* head for proc_inode->sysctl_inodes */
191 };
192 
193 struct ctl_dir {
194 	/* Header must be at the start of ctl_dir */
195 	struct ctl_table_header header;
196 	struct rb_root root;
197 };
198 
199 struct ctl_table_set {
200 	int (*is_seen)(struct ctl_table_set *);
201 	struct ctl_dir dir;
202 };
203 
204 struct ctl_table_root {
205 	struct ctl_table_set default_set;
206 	struct ctl_table_set *(*lookup)(struct ctl_table_root *root);
207 	void (*set_ownership)(struct ctl_table_header *head,
208 			      struct ctl_table *table,
209 			      kuid_t *uid, kgid_t *gid);
210 	int (*permissions)(struct ctl_table_header *head, struct ctl_table *table);
211 };
212 
213 /* struct ctl_path describes where in the hierarchy a table is added */
214 struct ctl_path {
215 	const char *procname;
216 };
217 
218 #define register_sysctl(path, table)	\
219 	register_sysctl_sz(path, table, ARRAY_SIZE(table))
220 
221 #ifdef CONFIG_SYSCTL
222 
223 void proc_sys_poll_notify(struct ctl_table_poll *poll);
224 
225 extern void setup_sysctl_set(struct ctl_table_set *p,
226 	struct ctl_table_root *root,
227 	int (*is_seen)(struct ctl_table_set *));
228 extern void retire_sysctl_set(struct ctl_table_set *set);
229 
230 struct ctl_table_header *__register_sysctl_table(
231 	struct ctl_table_set *set,
232 	const char *path, struct ctl_table *table, size_t table_size);
233 struct ctl_table_header *register_sysctl_sz(const char *path, struct ctl_table *table,
234 					    size_t table_size);
235 void unregister_sysctl_table(struct ctl_table_header * table);
236 
237 extern int sysctl_init_bases(void);
238 extern void __register_sysctl_init(const char *path, struct ctl_table *table,
239 				 const char *table_name, size_t table_size);
240 #define register_sysctl_init(path, table)	\
241 	__register_sysctl_init(path, table, #table, ARRAY_SIZE(table))
242 extern struct ctl_table_header *register_sysctl_mount_point(const char *path);
243 
244 void do_sysctl_args(void);
245 bool sysctl_is_alias(char *param);
246 int do_proc_douintvec(struct ctl_table *table, int write,
247 		      void *buffer, size_t *lenp, loff_t *ppos,
248 		      int (*conv)(unsigned long *lvalp,
249 				  unsigned int *valp,
250 				  int write, void *data),
251 		      void *data);
252 
253 extern int pwrsw_enabled;
254 extern int unaligned_enabled;
255 extern int unaligned_dump_stack;
256 extern int no_unaligned_warning;
257 
258 #define SYSCTL_PERM_EMPTY_DIR	(1 << 0)
259 
260 #else /* CONFIG_SYSCTL */
261 
register_sysctl_init(const char * path,struct ctl_table * table)262 static inline void register_sysctl_init(const char *path, struct ctl_table *table)
263 {
264 }
265 
register_sysctl_mount_point(const char * path)266 static inline struct ctl_table_header *register_sysctl_mount_point(const char *path)
267 {
268 	return NULL;
269 }
270 
register_sysctl_sz(const char * path,struct ctl_table * table,size_t table_size)271 static inline struct ctl_table_header *register_sysctl_sz(const char *path,
272 							  struct ctl_table *table,
273 							  size_t table_size)
274 {
275 	return NULL;
276 }
277 
unregister_sysctl_table(struct ctl_table_header * table)278 static inline void unregister_sysctl_table(struct ctl_table_header * table)
279 {
280 }
281 
setup_sysctl_set(struct ctl_table_set * p,struct ctl_table_root * root,int (* is_seen)(struct ctl_table_set *))282 static inline void setup_sysctl_set(struct ctl_table_set *p,
283 	struct ctl_table_root *root,
284 	int (*is_seen)(struct ctl_table_set *))
285 {
286 }
287 
do_sysctl_args(void)288 static inline void do_sysctl_args(void)
289 {
290 }
291 
sysctl_is_alias(char * param)292 static inline bool sysctl_is_alias(char *param)
293 {
294 	return false;
295 }
296 #endif /* CONFIG_SYSCTL */
297 
298 int sysctl_max_threads(struct ctl_table *table, int write, void *buffer,
299 		size_t *lenp, loff_t *ppos);
300 
301 #endif /* _LINUX_SYSCTL_H */
302