LXR linux/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 */
  33struct completion;
  34struct ctl_table;
  35struct nsproxy;
  36struct ctl_table_root;
  37struct ctl_table_header;
  38struct ctl_dir;
  39
  40typedef int proc_handler (struct ctl_table *ctl, int write,
  41                          void __user *buffer, size_t *lenp, loff_t *ppos);
  42
  43extern int proc_dostring(struct ctl_table *, int,
  44                         void __user *, size_t *, loff_t *);
  45extern int proc_dointvec(struct ctl_table *, int,
  46                         void __user *, size_t *, loff_t *);
  47extern int proc_douintvec(struct ctl_table *, int,
  48                         void __user *, size_t *, loff_t *);
  49extern int proc_dointvec_minmax(struct ctl_table *, int,
  50                                void __user *, size_t *, loff_t *);
  51extern int proc_douintvec_minmax(struct ctl_table *table, int write,
  52                                 void __user *buffer, size_t *lenp,
  53                                 loff_t *ppos);
  54extern int proc_dointvec_jiffies(struct ctl_table *, int,
  55                                 void __user *, size_t *, loff_t *);
  56extern int proc_dointvec_userhz_jiffies(struct ctl_table *, int,
  57                                        void __user *, size_t *, loff_t *);
  58extern int proc_dointvec_ms_jiffies(struct ctl_table *, int,
  59                                    void __user *, size_t *, loff_t *);
  60extern int proc_doulongvec_minmax(struct ctl_table *, int,
  61                                  void __user *, size_t *, loff_t *);
  62extern int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int,
  63                                      void __user *, size_t *, loff_t *);
  64extern int proc_do_large_bitmap(struct ctl_table *, int,
  65                                void __user *, size_t *, loff_t *);
  66extern int proc_do_static_key(struct ctl_table *table, int write,
  67                              void __user *buffer, size_t *lenp,
  68                              loff_t *ppos);
  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 */
  98struct ctl_table_poll {
  99        atomic_t event;
 100        wait_queue_head_t wait;
 101};
 102
 103static 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: */
 116struct 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
 129struct 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. */
 136struct 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
 156struct 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
 162struct ctl_table_set {
 163        int (*is_seen)(struct ctl_table_set *);
 164        struct ctl_dir dir;
 165};
 166
 167struct 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 */
 177struct ctl_path {
 178        const char *procname;
 179};
 180
 181#ifdef CONFIG_SYSCTL
 182
 183void proc_sys_poll_notify(struct ctl_table_poll *poll);
 184
 185extern void setup_sysctl_set(struct ctl_table_set *p,
 186        struct ctl_table_root *root,
 187        int (*is_seen)(struct ctl_table_set *));
 188extern void retire_sysctl_set(struct ctl_table_set *set);
 189
 190struct ctl_table_header *__register_sysctl_table(
 191        struct ctl_table_set *set,
 192        const char *path, struct ctl_table *table);
 193struct ctl_table_header *__register_sysctl_paths(
 194        struct ctl_table_set *set,
 195        const struct ctl_path *path, struct ctl_table *table);
 196struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table);
 197struct ctl_table_header *register_sysctl_table(struct ctl_table * table);
 198struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
 199                                                struct ctl_table *table);
 200
 201void unregister_sysctl_table(struct ctl_table_header * table);
 202
 203extern int sysctl_init(void);
 204
 205extern struct ctl_table sysctl_mount_point[];
 206
 207#else /* CONFIG_SYSCTL */
 208static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
 209{
 210        return NULL;
 211}
 212
 213static inline struct ctl_table_header *register_sysctl_paths(
 214                        const struct ctl_path *path, struct ctl_table *table)
 215{
 216        return NULL;
 217}
 218
 219static inline struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
 220{
 221        return NULL;
 222}
 223
 224static inline void unregister_sysctl_table(struct ctl_table_header * table)
 225{
 226}
 227
 228static 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
 236int 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 */
 240