sysctl.h

  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
 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
 56extern 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#define SYSCTL_CONV_IDENTITY(val) (val)
 63/**
 64 *
 65 * "dir" originates from read_iter (dir = 0) or write_iter (dir = 1)
 66 * in the file_operations struct at proc/proc_sysctl.c. Its value means
 67 * one of two things for sysctl:
 68 * 1. SYSCTL_USER_TO_KERN(dir) Writing to an internal kernel variable from user
 69 *                             space (dir > 0)
 70 * 2. SYSCTL_KERN_TO_USER(dir) Writing to a user space buffer from a kernel
 71 *                             variable (dir == 0).
 72 */
 73#define SYSCTL_USER_TO_KERN(dir) (!!(dir))
 74#define SYSCTL_KERN_TO_USER(dir) (!dir)
 75
 76#define SYSCTL_USER_TO_KERN_INT_CONV(name, u_ptr_op)		\
 77int sysctl_user_to_kern_int_conv##name(const bool *negp,	\
 78				       const unsigned long *u_ptr,\
 79				       int *k_ptr)		\
 80{								\
 81	unsigned long u = u_ptr_op(*u_ptr);			\
 82	if (*negp) {						\
 83		if (u > (unsigned long) INT_MAX + 1)		\
 84			return -EINVAL;				\
 85		WRITE_ONCE(*k_ptr, -u);				\
 86	} else {						\
 87		if (u > (unsigned long) INT_MAX)		\
 88			return -EINVAL;				\
 89		WRITE_ONCE(*k_ptr, u);				\
 90	}							\
 91	return 0;						\
 92}
 93
 94#define SYSCTL_KERN_TO_USER_INT_CONV(name, k_ptr_op)		\
 95int sysctl_kern_to_user_int_conv##name(bool *negp,		\
 96				       unsigned long *u_ptr,	\
 97				       const int *k_ptr)	\
 98{								\
 99	int val = READ_ONCE(*k_ptr);				\
100	if (val < 0) {						\
101		*negp = true;					\
102		*u_ptr = -k_ptr_op((unsigned long)val);		\
103	} else {						\
104		*negp = false;					\
105		*u_ptr = k_ptr_op((unsigned long)val);		\
106	}							\
107	return 0;						\
108}
109
110/**
111 * To range check on a converted value, use a temp k_ptr
112 * When checking range, value should be within (tbl->extra1, tbl->extra2)
113 */
114#define SYSCTL_INT_CONV_CUSTOM(name, user_to_kern, kern_to_user,	\
115			       k_ptr_range_check)			\
116int do_proc_int_conv##name(bool *negp, unsigned long *u_ptr, int *k_ptr,\
117			   int dir, const struct ctl_table *tbl)	\
118{									\
119	if (SYSCTL_KERN_TO_USER(dir))					\
120		return kern_to_user(negp, u_ptr, k_ptr);		\
121									\
122	if (k_ptr_range_check) {					\
123		int tmp_k, ret;						\
124		if (!tbl)						\
125			return -EINVAL;					\
126		ret = user_to_kern(negp, u_ptr, &tmp_k);		\
127		if (ret)						\
128			return ret;					\
129		if ((tbl->extra1 && *(int *)tbl->extra1 > tmp_k) ||	\
130		    (tbl->extra2 && *(int *)tbl->extra2 < tmp_k))	\
131			return -EINVAL;					\
132		WRITE_ONCE(*k_ptr, tmp_k);				\
133	} else								\
134		return user_to_kern(negp, u_ptr, k_ptr);		\
135	return 0;							\
136}
137
138#define SYSCTL_USER_TO_KERN_UINT_CONV(name, u_ptr_op)		\
139int sysctl_user_to_kern_uint_conv##name(const unsigned long *u_ptr,\
140					unsigned int *k_ptr)	\
141{								\
142	unsigned long u = u_ptr_op(*u_ptr);			\
143	if (u > UINT_MAX)					\
144		return -EINVAL;					\
145	WRITE_ONCE(*k_ptr, u);					\
146	return 0;						\
147}
148
149#define SYSCTL_UINT_CONV_CUSTOM(name, user_to_kern, kern_to_user,	\
150				k_ptr_range_check)			\
151int do_proc_uint_conv##name(unsigned long *u_ptr, unsigned int *k_ptr,	\
152			   int dir, const struct ctl_table *tbl)	\
153{									\
154	if (SYSCTL_KERN_TO_USER(dir))					\
155		return kern_to_user(u_ptr, k_ptr);			\
156									\
157	if (k_ptr_range_check) {					\
158		unsigned int tmp_k;					\
159		int ret;						\
160		if (!tbl)						\
161			return -EINVAL;					\
162		ret = user_to_kern(u_ptr, &tmp_k);			\
163		if (ret)						\
164			return ret;					\
165		if ((tbl->extra1 &&					\
166		     *(unsigned int *)tbl->extra1 > tmp_k) ||		\
167		    (tbl->extra2 &&					\
168		     *(unsigned int *)tbl->extra2 < tmp_k))		\
169			return -ERANGE;					\
170		WRITE_ONCE(*k_ptr, tmp_k);				\
171	} else								\
172		return user_to_kern(u_ptr, k_ptr);			\
173	return 0;							\
174}
175
176
177extern const unsigned long sysctl_long_vals[];
178
179typedef int proc_handler(const struct ctl_table *ctl, int write, void *buffer,
180		size_t *lenp, loff_t *ppos);
181
182int proc_dostring(const struct ctl_table *, int, void *, size_t *, loff_t *);
183int proc_dobool(const struct ctl_table *table, int write, void *buffer,
184		size_t *lenp, loff_t *ppos);
185int proc_dointvec(const struct ctl_table *, int, void *, size_t *, loff_t *);
186int proc_dointvec_minmax(const struct ctl_table *table, int dir, void *buffer,
187			 size_t *lenp, loff_t *ppos);
188int proc_dointvec_conv(const struct ctl_table *table, int dir, void *buffer,
189		       size_t *lenp, loff_t *ppos,
190		       int (*conv)(bool *negp, unsigned long *u_ptr, int *k_ptr,
191				   int dir, const struct ctl_table *table));
192int proc_douintvec(const struct ctl_table *, int, void *, size_t *, loff_t *);
193int proc_douintvec_minmax(const struct ctl_table *table, int write, void *buffer,
194		size_t *lenp, loff_t *ppos);
195int proc_douintvec_conv(const struct ctl_table *table, int write, void *buffer,
196			size_t *lenp, loff_t *ppos,
197			int (*conv)(unsigned long *lvalp, unsigned int *valp,
198				    int write, const struct ctl_table *table));
199
200int proc_dou8vec_minmax(const struct ctl_table *table, int write, void *buffer,
201			size_t *lenp, loff_t *ppos);
202int proc_doulongvec_minmax(const struct ctl_table *, int, void *, size_t *, loff_t *);
203int proc_doulongvec_minmax_conv(const struct ctl_table *table, int dir,
204				void *buffer, size_t *lenp, loff_t *ppos,
205				unsigned long convmul, unsigned long convdiv);
206int proc_do_large_bitmap(const struct ctl_table *, int, void *, size_t *, loff_t *);
207int proc_do_static_key(const struct ctl_table *table, int write, void *buffer,
208		size_t *lenp, loff_t *ppos);
209int sysctl_kern_to_user_uint_conv(unsigned long *u_ptr, const unsigned int *k_ptr);
210
211/*
212 * Register a set of sysctl names by calling register_sysctl
213 * with an initialised array of struct ctl_table's.
214 *
215 * sysctl names can be mirrored automatically under /proc/sys.  The
216 * procname supplied controls /proc naming.
217 *
218 * The table's mode will be honoured for proc-fs access.
219 *
220 * Leaf nodes in the sysctl tree will be represented by a single file
221 * under /proc; non-leaf nodes will be represented by directories.  A
222 * null procname disables /proc mirroring at this node.
223 *
224 * The data and maxlen fields of the ctl_table
225 * struct enable minimal validation of the values being written to be
226 * performed, and the mode field allows minimal authentication.
227 * 
228 * There must be a proc_handler routine for any terminal nodes
229 * mirrored under /proc/sys (non-terminals are handled by a built-in
230 * directory handler).  Several default handlers are available to
231 * cover common cases.
232 */
233
234/* Support for userspace poll() to watch for changes */
235struct ctl_table_poll {
236	atomic_t event;
237	wait_queue_head_t wait;
238};
239
240static inline void *proc_sys_poll_event(struct ctl_table_poll *poll)
241{
242	return (void *)(unsigned long)atomic_read(&poll->event);
243}
244
245#define __CTL_TABLE_POLL_INITIALIZER(name) {				\
246	.event = ATOMIC_INIT(0),					\
247	.wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.wait) }
248
249#define DEFINE_CTL_TABLE_POLL(name)					\
250	struct ctl_table_poll name = __CTL_TABLE_POLL_INITIALIZER(name)
251
252/* A sysctl table is an array of struct ctl_table: */
253struct ctl_table {
254	const char *procname;		/* Text ID for /proc/sys */
255	void *data;
256	int maxlen;
257	umode_t mode;
258	proc_handler *proc_handler;	/* Callback for text formatting */
259	struct ctl_table_poll *poll;
260	void *extra1;
261	void *extra2;
262} __randomize_layout;
263
264struct ctl_node {
265	struct rb_node node;
266	struct ctl_table_header *header;
267};
268
269/**
270 * struct ctl_table_header - maintains dynamic lists of struct ctl_table trees
271 * @ctl_table: pointer to the first element in ctl_table array
272 * @ctl_table_size: number of elements pointed by @ctl_table
273 * @used: The entry will never be touched when equal to 0.
274 * @count: Upped every time something is added to @inodes and downed every time
275 *         something is removed from inodes
276 * @nreg: When nreg drops to 0 the ctl_table_header will be unregistered.
277 * @rcu: Delays the freeing of the inode. Introduced with "unfuck proc_sysctl ->d_compare()"
278 *
279 * @type: Enumeration to differentiate between ctl target types
280 * @type.SYSCTL_TABLE_TYPE_DEFAULT: ctl target with no special considerations
281 * @type.SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY: Identifies a permanently empty dir
282 *                                            target to serve as a mount point
283 */
284struct ctl_table_header {
285	union {
286		struct {
287			const struct ctl_table *ctl_table;
288			int ctl_table_size;
289			int used;
290			int count;
291			int nreg;
292		};
293		struct rcu_head rcu;
294	};
295	struct completion *unregistering;
296	const struct ctl_table *ctl_table_arg;
297	struct ctl_table_root *root;
298	struct ctl_table_set *set;
299	struct ctl_dir *parent;
300	struct ctl_node *node;
301	struct hlist_head inodes; /* head for proc_inode->sysctl_inodes */
302	enum {
303		SYSCTL_TABLE_TYPE_DEFAULT,
304		SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY,
305	} type;
306};
307
308struct ctl_dir {
309	/* Header must be at the start of ctl_dir */
310	struct ctl_table_header header;
311	struct rb_root root;
312};
313
314struct ctl_table_set {
315	int (*is_seen)(struct ctl_table_set *);
316	struct ctl_dir dir;
317};
318
319struct ctl_table_root {
320	struct ctl_table_set default_set;
321	struct ctl_table_set *(*lookup)(struct ctl_table_root *root);
322	void (*set_ownership)(struct ctl_table_header *head,
323			      kuid_t *uid, kgid_t *gid);
324	int (*permissions)(struct ctl_table_header *head, const struct ctl_table *table);
325};
326
327#define register_sysctl(path, table)	\
328	register_sysctl_sz(path, table, ARRAY_SIZE(table))
329
330#ifdef CONFIG_SYSCTL
331
332void proc_sys_poll_notify(struct ctl_table_poll *poll);
333
334extern void setup_sysctl_set(struct ctl_table_set *p,
335	struct ctl_table_root *root,
336	int (*is_seen)(struct ctl_table_set *));
337extern void retire_sysctl_set(struct ctl_table_set *set);
338
339struct ctl_table_header *__register_sysctl_table(
340	struct ctl_table_set *set,
341	const char *path, const struct ctl_table *table, size_t table_size);
342struct ctl_table_header *register_sysctl_sz(const char *path, const struct ctl_table *table,
343					    size_t table_size);
344void unregister_sysctl_table(struct ctl_table_header * table);
345
346extern int sysctl_init_bases(void);
347extern void __register_sysctl_init(const char *path, const struct ctl_table *table,
348				 const char *table_name, size_t table_size);
349#define register_sysctl_init(path, table)	\
350	__register_sysctl_init(path, table, #table, ARRAY_SIZE(table))
351extern struct ctl_table_header *register_sysctl_mount_point(const char *path);
352
353void do_sysctl_args(void);
354bool sysctl_is_alias(char *param);
355
356extern int unaligned_enabled;
357extern int no_unaligned_warning;
358
359#else /* CONFIG_SYSCTL */
360
361static inline void register_sysctl_init(const char *path, const struct ctl_table *table)
362{
363}
364
365static inline struct ctl_table_header *register_sysctl_mount_point(const char *path)
366{
367	return NULL;
368}
369
370static inline struct ctl_table_header *register_sysctl_sz(const char *path,
371							  const struct ctl_table *table,
372							  size_t table_size)
373{
374	return NULL;
375}
376
377static inline void unregister_sysctl_table(struct ctl_table_header * table)
378{
379}
380
381static inline void setup_sysctl_set(struct ctl_table_set *p,
382	struct ctl_table_root *root,
383	int (*is_seen)(struct ctl_table_set *))
384{
385}
386
387static inline void do_sysctl_args(void)
388{
389}
390
391static inline bool sysctl_is_alias(char *param)
392{
393	return false;
394}
395#endif /* CONFIG_SYSCTL */
396
397#endif /* _LINUX_SYSCTL_H */