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_dopipe_max_size(struct ctl_table *table, int write,
  55                                 void __user *buffer, size_t *lenp,
  56                                 loff_t *ppos);
  57 extern int proc_dointvec_jiffies(struct ctl_table *, int,
  58                                  void __user *, size_t *, loff_t *);
  59 extern int proc_dointvec_userhz_jiffies(struct ctl_table *, int,
  60                                         void __user *, size_t *, loff_t *);
  61 extern int proc_dointvec_ms_jiffies(struct ctl_table *, int,
  62                                     void __user *, size_t *, loff_t *);
  63 extern int proc_doulongvec_minmax(struct ctl_table *, int,
  64                                   void __user *, size_t *, loff_t *);
  65 extern int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int,
  66                                       void __user *, size_t *, loff_t *);
  67 extern int proc_do_large_bitmap(struct ctl_table *, int,
  68                                 void __user *, size_t *, loff_t *);
  69
  70 /*
  71  * Register a set of sysctl names by calling register_sysctl_table
  72  * with an initialised array of struct ctl_table's.  An entry with
  73  * NULL procname terminates the table.  table->de will be
  74  * set up by the registration and need not be initialised in advance.
  75  *
  76  * sysctl names can be mirrored automatically under /proc/sys.  The
  77  * procname supplied controls /proc naming.
  78  *
  79  * The table's mode will be honoured both for sys_sysctl(2) and
  80  * proc-fs access.
  81  *
  82  * Leaf nodes in the sysctl tree will be represented by a single file
  83  * under /proc; non-leaf nodes will be represented by directories.  A
  84  * null procname disables /proc mirroring at this node.
  85  *
  86  * sysctl(2) can automatically manage read and write requests through
  87  * the sysctl table.  The data and maxlen fields of the ctl_table
  88  * struct enable minimal validation of the values being written to be
  89  * performed, and the mode field allows minimal authentication.
  90  *
  91  * There must be a proc_handler routine for any terminal nodes
  92  * mirrored under /proc/sys (non-terminals are handled by a built-in
  93  * directory handler).  Several default handlers are available to
  94  * cover common cases.
  95  */
  96
  97 /* Support for userspace poll() to watch for changes */
  98 struct ctl_table_poll {
  99         atomic_t event;
 100         wait_queue_head_t wait;
 101 };
 102
 103 static inline void *proc_sys_poll_event(struct ctl_table_poll *poll)
 104 {
 105         return (void *)(unsigned long)atomic_read(&poll->event);
 106 }
 107
 108 #define __CTL_TABLE_POLL_INITIALIZER(name) {                            \
 109         .event = ATOMIC_INIT(0),                                        \
 110         .wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.wait) }
 111
 112 #define DEFINE_CTL_TABLE_POLL(name)                                     \
 113         struct ctl_table_poll name = __CTL_TABLE_POLL_INITIALIZER(name)
 114
 115 /* A sysctl table is an array of struct ctl_table: */
 116 struct ctl_table
 117 {
 118         const char *procname;           /* Text ID for /proc/sys, or zero */
 119         void *data;
 120         int maxlen;
 121         umode_t mode;
 122         struct ctl_table *child;        /* Deprecated */
 123         proc_handler *proc_handler;     /* Callback for text formatting */
 124         struct ctl_table_poll *poll;
 125         void *extra1;
 126         void *extra2;
 127 } __randomize_layout;
 128
 129 struct ctl_node {
 130         struct rb_node node;
 131         struct ctl_table_header *header;
 132 };
 133
 134 /* struct ctl_table_header is used to maintain dynamic lists of
 135    struct ctl_table trees. */
 136 struct ctl_table_header
 137 {
 138         union {
 139                 struct {
 140                         struct ctl_table *ctl_table;
 141                         int used;
 142                         int count;
 143                         int nreg;
 144                 };
 145                 struct rcu_head rcu;
 146         };
 147         struct completion *unregistering;
 148         struct ctl_table *ctl_table_arg;
 149         struct ctl_table_root *root;
 150         struct ctl_table_set *set;
 151         struct ctl_dir *parent;
 152         struct ctl_node *node;
 153         struct hlist_head inodes; /* head for proc_inode->sysctl_inodes */
 154 };
 155
 156 struct ctl_dir {
 157         /* Header must be at the start of ctl_dir */
 158         struct ctl_table_header header;
 159         struct rb_root root;
 160 };
 161
 162 struct ctl_table_set {
 163         int (*is_seen)(struct ctl_table_set *);
 164         struct ctl_dir dir;
 165 };
 166
 167 struct ctl_table_root {
 168         struct ctl_table_set default_set;
 169         struct ctl_table_set *(*lookup)(struct ctl_table_root *root);
 170         void (*set_ownership)(struct ctl_table_header *head,
 171                               struct ctl_table *table,
 172                               kuid_t *uid, kgid_t *gid);
 173         int (*permissions)(struct ctl_table_header *head, struct ctl_table *table);
 174 };
 175
 176 /* struct ctl_path describes where in the hierarchy a table is added */
 177 struct ctl_path {
 178         const char *procname;
 179 };
 180
 181 #ifdef CONFIG_SYSCTL
 182
 183 void proc_sys_poll_notify(struct ctl_table_poll *poll);
 184
 185 extern void setup_sysctl_set(struct ctl_table_set *p,
 186         struct ctl_table_root *root,
 187         int (*is_seen)(struct ctl_table_set *));
 188 extern void retire_sysctl_set(struct ctl_table_set *set);
 189
 190 struct ctl_table_header *__register_sysctl_table(
 191         struct ctl_table_set *set,
 192         const char *path, struct ctl_table *table);
 193 struct ctl_table_header *__register_sysctl_paths(
 194         struct ctl_table_set *set,
 195         const struct ctl_path *path, struct ctl_table *table);
 196 struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table);
 197 struct ctl_table_header *register_sysctl_table(struct ctl_table * table);
 198 struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
 199                                                 struct ctl_table *table);
 200
 201 void unregister_sysctl_table(struct ctl_table_header * table);
 202
 203 extern int sysctl_init(void);
 204
 205 extern struct ctl_table sysctl_mount_point[];
 206
 207 #else /* CONFIG_SYSCTL */
 208 static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
 209 {
 210         return NULL;
 211 }
 212
 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
 219 static inline struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
 220 {
 221         return NULL;
 222 }
 223
 224 static inline void unregister_sysctl_table(struct ctl_table_header * table)
 225 {
 226 }
 227
 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 */