include/linux/sysctl.h

   1 /*
   2  * sysctl.h: General linux system control interface
   3  *
   4  * Begun 24 March 1995, Stephen Tweedie
   5  *
   6  ****************************************************************
   7  ****************************************************************
   8  **
   9  **  WARNING:
  10  **  The values in this file are exported to user space via
  11  **  the sysctl() binary interface.  Do *NOT* change the
  12  **  numbering of any existing values here, and do not change
  13  **  any numbers within any one set of values.  If you have to
  14  **  redefine an existing interface, use a new number for it.
  15  **  The kernel will then return -ENOTDIR to any application using
  16  **  the old binary interface.
  17  **
  18  ****************************************************************
  19  ****************************************************************
  20  */
  21 #ifndef _LINUX_SYSCTL_H
  22 #define _LINUX_SYSCTL_H
  23
  24 #include <linux/list.h>
  25 #include <linux/rcupdate.h>
  26 #include <linux/wait.h>
  27 #include <linux/rbtree.h>
  28 #include <uapi/linux/sysctl.h>
  29
  30 /* For the /proc/sys support */
  31 struct ctl_table;
  32 struct nsproxy;
  33 struct ctl_table_root;
  34 struct ctl_table_header;
  35 struct ctl_dir;
  36
  37 typedef int proc_handler (struct ctl_table *ctl, int write,
  38                           void __user *buffer, size_t *lenp, loff_t *ppos);
  39
  40 extern int proc_dostring(struct ctl_table *, int,
  41                          void __user *, size_t *, loff_t *);
  42 extern int proc_dointvec(struct ctl_table *, int,
  43                          void __user *, size_t *, loff_t *);
  44 extern int proc_dointvec_minmax(struct ctl_table *, int,
  45                                 void __user *, size_t *, loff_t *);
  46 extern int proc_dointvec_jiffies(struct ctl_table *, int,
  47                                  void __user *, size_t *, loff_t *);
  48 extern int proc_dointvec_userhz_jiffies(struct ctl_table *, int,
  49                                         void __user *, size_t *, loff_t *);
  50 extern int proc_dointvec_ms_jiffies(struct ctl_table *, int,
  51                                     void __user *, size_t *, loff_t *);
  52 extern int proc_doulongvec_minmax(struct ctl_table *, int,
  53                                   void __user *, size_t *, loff_t *);
  54 extern int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int,
  55                                       void __user *, size_t *, loff_t *);
  56 extern int proc_do_large_bitmap(struct ctl_table *, int,
  57                                 void __user *, size_t *, loff_t *);
  58
  59 /*
  60  * Register a set of sysctl names by calling register_sysctl_table
  61  * with an initialised array of struct ctl_table's.  An entry with
  62  * NULL procname terminates the table.  table->de will be
  63  * set up by the registration and need not be initialised in advance.
  64  *
  65  * sysctl names can be mirrored automatically under /proc/sys.  The
  66  * procname supplied controls /proc naming.
  67  *
  68  * The table's mode will be honoured both for sys_sysctl(2) and
  69  * proc-fs access.
  70  *
  71  * Leaf nodes in the sysctl tree will be represented by a single file
  72  * under /proc; non-leaf nodes will be represented by directories.  A
  73  * null procname disables /proc mirroring at this node.
  74  *
  75  * sysctl(2) can automatically manage read and write requests through
  76  * the sysctl table.  The data and maxlen fields of the ctl_table
  77  * struct enable minimal validation of the values being written to be
  78  * performed, and the mode field allows minimal authentication.
  79  *
  80  * There must be a proc_handler routine for any terminal nodes
  81  * mirrored under /proc/sys (non-terminals are handled by a built-in
  82  * directory handler).  Several default handlers are available to
  83  * cover common cases.
  84  */
  85
  86 /* Support for userspace poll() to watch for changes */
  87 struct ctl_table_poll {
  88         atomic_t event;
  89         wait_queue_head_t wait;
  90 };
  91
  92 static inline void *proc_sys_poll_event(struct ctl_table_poll *poll)
  93 {
  94         return (void *)(unsigned long)atomic_read(&poll->event);
  95 }
  96
  97 #define __CTL_TABLE_POLL_INITIALIZER(name) {                            \
  98         .event = ATOMIC_INIT(0),                                        \
  99         .wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.wait) }
 100
 101 #define DEFINE_CTL_TABLE_POLL(name)                                     \
 102         struct ctl_table_poll name = __CTL_TABLE_POLL_INITIALIZER(name)
 103
 104 /* A sysctl table is an array of struct ctl_table: */
 105 struct ctl_table
 106 {
 107         const char *procname;           /* Text ID for /proc/sys, or zero */
 108         void *data;
 109         int maxlen;
 110         umode_t mode;
 111         struct ctl_table *child;        /* Deprecated */
 112         proc_handler *proc_handler;     /* Callback for text formatting */
 113         struct ctl_table_poll *poll;
 114         void *extra1;
 115         void *extra2;
 116 };
 117
 118 struct ctl_node {
 119         struct rb_node node;
 120         struct ctl_table_header *header;
 121 };
 122
 123 /* struct ctl_table_header is used to maintain dynamic lists of
 124    struct ctl_table trees. */
 125 struct ctl_table_header
 126 {
 127         union {
 128                 struct {
 129                         struct ctl_table *ctl_table;
 130                         int used;
 131                         int count;
 132                         int nreg;
 133                 };
 134                 struct rcu_head rcu;
 135         };
 136         struct completion *unregistering;
 137         struct ctl_table *ctl_table_arg;
 138         struct ctl_table_root *root;
 139         struct ctl_table_set *set;
 140         struct ctl_dir *parent;
 141         struct ctl_node *node;
 142 };
 143
 144 struct ctl_dir {
 145         /* Header must be at the start of ctl_dir */
 146         struct ctl_table_header header;
 147         struct rb_root root;
 148 };
 149
 150 struct ctl_table_set {
 151         int (*is_seen)(struct ctl_table_set *);
 152         struct ctl_dir dir;
 153 };
 154
 155 struct ctl_table_root {
 156         struct ctl_table_set default_set;
 157         struct ctl_table_set *(*lookup)(struct ctl_table_root *root,
 158                                            struct nsproxy *namespaces);
 159         int (*permissions)(struct ctl_table_header *head, struct ctl_table *table);
 160 };
 161
 162 /* struct ctl_path describes where in the hierarchy a table is added */
 163 struct ctl_path {
 164         const char *procname;
 165 };
 166
 167 #ifdef CONFIG_SYSCTL
 168
 169 void proc_sys_poll_notify(struct ctl_table_poll *poll);
 170
 171 extern void setup_sysctl_set(struct ctl_table_set *p,
 172         struct ctl_table_root *root,
 173         int (*is_seen)(struct ctl_table_set *));
 174 extern void retire_sysctl_set(struct ctl_table_set *set);
 175
 176 void register_sysctl_root(struct ctl_table_root *root);
 177 struct ctl_table_header *__register_sysctl_table(
 178         struct ctl_table_set *set,
 179         const char *path, struct ctl_table *table);
 180 struct ctl_table_header *__register_sysctl_paths(
 181         struct ctl_table_set *set,
 182         const struct ctl_path *path, struct ctl_table *table);
 183 struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table);
 184 struct ctl_table_header *register_sysctl_table(struct ctl_table * table);
 185 struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
 186                                                 struct ctl_table *table);
 187
 188 void unregister_sysctl_table(struct ctl_table_header * table);
 189
 190 extern int sysctl_init(void);
 191
 192 extern struct ctl_table sysctl_mount_point[];
 193
 194 #else /* CONFIG_SYSCTL */
 195 static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
 196 {
 197         return NULL;
 198 }
 199
 200 static inline struct ctl_table_header *register_sysctl_paths(
 201                         const struct ctl_path *path, struct ctl_table *table)
 202 {
 203         return NULL;
 204 }
 205
 206 static inline void unregister_sysctl_table(struct ctl_table_header * table)
 207 {
 208 }
 209
 210 static inline void setup_sysctl_set(struct ctl_table_set *p,
 211         struct ctl_table_root *root,
 212         int (*is_seen)(struct ctl_table_set *))
 213 {
 214 }
 215
 216 #endif /* CONFIG_SYSCTL */
 217
 218 int sysctl_max_threads(struct ctl_table *table, int write,
 219                        void __user *buffer, size_t *lenp, loff_t *ppos);
 220
 221 #endif /* _LINUX_SYSCTL_H */