include/linux/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 */
  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
 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
 202 extern struct ctl_table sysctl_mount_point[];
 203
 204 #else /* CONFIG_SYSCTL */
 205 static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
 206 {
 207         return NULL;
 208 }
 209
 210 static inline struct ctl_table_header *register_sysctl_paths(
 211                         const struct ctl_path *path, struct ctl_table *table)
 212 {
 213         return NULL;
 214 }
 215
 216 static inline void unregister_sysctl_table(struct ctl_table_header * table)
 217 {
 218 }
 219
 220 static inline void setup_sysctl_set(struct ctl_table_set *p,
 221         struct ctl_table_root *root,
 222         int (*is_seen)(struct ctl_table_set *))
 223 {
 224 }
 225
 226 #endif /* CONFIG_SYSCTL */
 227
 228 int sysctl_max_threads(struct ctl_table *table, int write,
 229                        void __user *buffer, size_t *lenp, loff_t *ppos);
 230
 231 #endif /* _LINUX_SYSCTL_H */