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 *);
  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 */
  95struct ctl_table_poll {
  96        atomic_t event;
  97        wait_queue_head_t wait;
  98};
  99
 100static 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: */
 113struct 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
 126struct 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. */
 133struct 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
 153struct 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
 159struct ctl_table_set {
 160        int (*is_seen)(struct ctl_table_set *);
 161        struct ctl_dir dir;
 162};
 163
 164struct 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 */
 174struct ctl_path {
 175        const char *procname;
 176};
 177
 178#ifdef CONFIG_SYSCTL
 179
 180void proc_sys_poll_notify(struct ctl_table_poll *poll);
 181
 182extern void setup_sysctl_set(struct ctl_table_set *p,
 183        struct ctl_table_root *root,
 184        int (*is_seen)(struct ctl_table_set *));
 185extern void retire_sysctl_set(struct ctl_table_set *set);
 186
 187struct ctl_table_header *__register_sysctl_table(
 188        struct ctl_table_set *set,
 189        const char *path, struct ctl_table *table);
 190struct ctl_table_header *__register_sysctl_paths(
 191        struct ctl_table_set *set,
 192        const struct ctl_path *path, struct ctl_table *table);
 193struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table);
 194struct ctl_table_header *register_sysctl_table(struct ctl_table * table);
 195struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
 196                                                struct ctl_table *table);
 197
 198void unregister_sysctl_table(struct ctl_table_header * table);
 199
 200extern int sysctl_init(void);
 201
 202extern struct ctl_table sysctl_mount_point[];
 203
 204#else /* CONFIG_SYSCTL */
 205static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
 206{
 207        return NULL;
 208}
 209
 210static inline struct ctl_table_header *register_sysctl_paths(
 211                        const struct ctl_path *path, struct ctl_table *table)
 212{
 213        return NULL;
 214}
 215
 216static inline struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
 217{
 218        return NULL;
 219}
 220
 221static inline void unregister_sysctl_table(struct ctl_table_header * table)
 222{
 223}
 224
 225static inline void setup_sysctl_set(struct ctl_table_set *p,
 226        struct ctl_table_root *root,
 227        int (*is_seen)(struct ctl_table_set *))
 228{
 229}
 230
 231#endif /* CONFIG_SYSCTL */
 232
 233int sysctl_max_threads(struct ctl_table *table, int write,
 234                       void __user *buffer, size_t *lenp, loff_t *ppos);
 235
 236#endif /* _LINUX_SYSCTL_H */
 237