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
  40/* Keep the same order as in fs/proc/proc_sysctl.c */
  41#define SYSCTL_ZERO     ((void *)&sysctl_vals[0])
  42#define SYSCTL_ONE      ((void *)&sysctl_vals[1])
  43#define SYSCTL_INT_MAX  ((void *)&sysctl_vals[2])
  44
  45extern const int sysctl_vals[];
  46
  47typedef int proc_handler(struct ctl_table *ctl, int write, void *buffer,
  48                size_t *lenp, loff_t *ppos);
  49
  50int proc_dostring(struct ctl_table *, int, void *, size_t *, loff_t *);
  51int proc_dointvec(struct ctl_table *, int, void *, size_t *, loff_t *);
  52int proc_douintvec(struct ctl_table *, int, void *, size_t *, loff_t *);
  53int proc_dointvec_minmax(struct ctl_table *, int, void *, size_t *, loff_t *);
  54int proc_douintvec_minmax(struct ctl_table *table, int write, void *buffer,
  55                size_t *lenp, loff_t *ppos);
  56int proc_dou8vec_minmax(struct ctl_table *table, int write, void *buffer,
  57                        size_t *lenp, loff_t *ppos);
  58int proc_dointvec_jiffies(struct ctl_table *, int, void *, size_t *, loff_t *);
  59int proc_dointvec_userhz_jiffies(struct ctl_table *, int, void *, size_t *,
  60                loff_t *);
  61int proc_dointvec_ms_jiffies(struct ctl_table *, int, void *, size_t *,
  62                loff_t *);
  63int proc_doulongvec_minmax(struct ctl_table *, int, void *, size_t *, loff_t *);
  64int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int, void *,
  65                size_t *, loff_t *);
  66int proc_do_large_bitmap(struct ctl_table *, int, void *, size_t *, loff_t *);
  67int proc_do_static_key(struct ctl_table *table, int write, void *buffer,
  68                size_t *lenp, 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 for proc-fs access.
  80 *
  81 * Leaf nodes in the sysctl tree will be represented by a single file
  82 * under /proc; non-leaf nodes will be represented by directories.  A
  83 * null procname disables /proc mirroring at this node.
  84 *
  85 * The data and maxlen fields of the ctl_table
  86 * struct enable minimal validation of the values being written to be
  87 * performed, and the mode field allows minimal authentication.
  88 * 
  89 * There must be a proc_handler routine for any terminal nodes
  90 * mirrored under /proc/sys (non-terminals are handled by a built-in
  91 * directory handler).  Several default handlers are available to
  92 * cover common cases.
  93 */
  94
  95/* Support for userspace poll() to watch for changes */
  96struct ctl_table_poll {
  97        atomic_t event;
  98        wait_queue_head_t wait;
  99};
 100
 101static inline void *proc_sys_poll_event(struct ctl_table_poll *poll)
 102{
 103        return (void *)(unsigned long)atomic_read(&poll->event);
 104}
 105
 106#define __CTL_TABLE_POLL_INITIALIZER(name) {                            \
 107        .event = ATOMIC_INIT(0),                                        \
 108        .wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.wait) }
 109
 110#define DEFINE_CTL_TABLE_POLL(name)                                     \
 111        struct ctl_table_poll name = __CTL_TABLE_POLL_INITIALIZER(name)
 112
 113/* A sysctl table is an array of struct ctl_table: */
 114struct ctl_table {
 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        union {
 135                struct {
 136                        struct ctl_table *ctl_table;
 137                        int used;
 138                        int count;
 139                        int nreg;
 140                };
 141                struct rcu_head rcu;
 142        };
 143        struct completion *unregistering;
 144        struct ctl_table *ctl_table_arg;
 145        struct ctl_table_root *root;
 146        struct ctl_table_set *set;
 147        struct ctl_dir *parent;
 148        struct ctl_node *node;
 149        struct hlist_head inodes; /* head for proc_inode->sysctl_inodes */
 150};
 151
 152struct ctl_dir {
 153        /* Header must be at the start of ctl_dir */
 154        struct ctl_table_header header;
 155        struct rb_root root;
 156};
 157
 158struct ctl_table_set {
 159        int (*is_seen)(struct ctl_table_set *);
 160        struct ctl_dir dir;
 161};
 162
 163struct ctl_table_root {
 164        struct ctl_table_set default_set;
 165        struct ctl_table_set *(*lookup)(struct ctl_table_root *root);
 166        void (*set_ownership)(struct ctl_table_header *head,
 167                              struct ctl_table *table,
 168                              kuid_t *uid, kgid_t *gid);
 169        int (*permissions)(struct ctl_table_header *head, struct ctl_table *table);
 170};
 171
 172/* struct ctl_path describes where in the hierarchy a table is added */
 173struct ctl_path {
 174        const char *procname;
 175};
 176
 177#ifdef CONFIG_SYSCTL
 178
 179void proc_sys_poll_notify(struct ctl_table_poll *poll);
 180
 181extern void setup_sysctl_set(struct ctl_table_set *p,
 182        struct ctl_table_root *root,
 183        int (*is_seen)(struct ctl_table_set *));
 184extern void retire_sysctl_set(struct ctl_table_set *set);
 185
 186struct ctl_table_header *__register_sysctl_table(
 187        struct ctl_table_set *set,
 188        const char *path, struct ctl_table *table);
 189struct ctl_table_header *__register_sysctl_paths(
 190        struct ctl_table_set *set,
 191        const struct ctl_path *path, struct ctl_table *table);
 192struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table);
 193struct ctl_table_header *register_sysctl_table(struct ctl_table * table);
 194struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
 195                                                struct ctl_table *table);
 196
 197void unregister_sysctl_table(struct ctl_table_header * table);
 198
 199extern int sysctl_init(void);
 200void do_sysctl_args(void);
 201
 202extern int pwrsw_enabled;
 203extern int unaligned_enabled;
 204extern int unaligned_dump_stack;
 205extern int no_unaligned_warning;
 206
 207extern struct ctl_table sysctl_mount_point[];
 208extern struct ctl_table random_table[];
 209extern struct ctl_table firmware_config_table[];
 210extern struct ctl_table epoll_table[];
 211
 212#else /* CONFIG_SYSCTL */
 213static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
 214{
 215        return NULL;
 216}
 217
 218static inline struct ctl_table_header *register_sysctl_paths(
 219                        const struct ctl_path *path, struct ctl_table *table)
 220{
 221        return NULL;
 222}
 223
 224static inline struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
 225{
 226        return NULL;
 227}
 228
 229static inline void unregister_sysctl_table(struct ctl_table_header * table)
 230{
 231}
 232
 233static inline void setup_sysctl_set(struct ctl_table_set *p,
 234        struct ctl_table_root *root,
 235        int (*is_seen)(struct ctl_table_set *))
 236{
 237}
 238
 239static inline void do_sysctl_args(void)
 240{
 241}
 242#endif /* CONFIG_SYSCTL */
 243
 244int sysctl_max_threads(struct ctl_table *table, int write, void *buffer,
 245                size_t *lenp, loff_t *ppos);
 246
 247#endif /* _LINUX_SYSCTL_H */
 248