linux/include/linux/sysctl.h
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   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_dointvec_jiffies(struct ctl_table *, int, void *, size_t *, loff_t *);
  57int proc_dointvec_userhz_jiffies(struct ctl_table *, int, void *, size_t *,
  58                loff_t *);
  59int proc_dointvec_ms_jiffies(struct ctl_table *, int, void *, size_t *,
  60                loff_t *);
  61int proc_doulongvec_minmax(struct ctl_table *, int, void *, size_t *, loff_t *);
  62int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int, void *,
  63                size_t *, loff_t *);
  64int proc_do_large_bitmap(struct ctl_table *, int, void *, size_t *, loff_t *);
  65int proc_do_static_key(struct ctl_table *table, int write, void *buffer,
  66                size_t *lenp, loff_t *ppos);
  67
  68/*
  69 * Register a set of sysctl names by calling register_sysctl_table
  70 * with an initialised array of struct ctl_table's.  An entry with 
  71 * NULL procname terminates the table.  table->de will be
  72 * set up by the registration and need not be initialised in advance.
  73 *
  74 * sysctl names can be mirrored automatically under /proc/sys.  The
  75 * procname supplied controls /proc naming.
  76 *
  77 * The table's mode will be honoured for 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 * The data and maxlen fields of the ctl_table
  84 * struct enable minimal validation of the values being written to be
  85 * performed, and the mode field allows minimal authentication.
  86 * 
  87 * There must be a proc_handler routine for any terminal nodes
  88 * mirrored under /proc/sys (non-terminals are handled by a built-in
  89 * directory handler).  Several default handlers are available to
  90 * cover common cases.
  91 */
  92
  93/* Support for userspace poll() to watch for changes */
  94struct ctl_table_poll {
  95        atomic_t event;
  96        wait_queue_head_t wait;
  97};
  98
  99static inline void *proc_sys_poll_event(struct ctl_table_poll *poll)
 100{
 101        return (void *)(unsigned long)atomic_read(&poll->event);
 102}
 103
 104#define __CTL_TABLE_POLL_INITIALIZER(name) {                            \
 105        .event = ATOMIC_INIT(0),                                        \
 106        .wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.wait) }
 107
 108#define DEFINE_CTL_TABLE_POLL(name)                                     \
 109        struct ctl_table_poll name = __CTL_TABLE_POLL_INITIALIZER(name)
 110
 111/* A sysctl table is an array of struct ctl_table: */
 112struct ctl_table {
 113        const char *procname;           /* Text ID for /proc/sys, or zero */
 114        void *data;
 115        int maxlen;
 116        umode_t mode;
 117        struct ctl_table *child;        /* Deprecated */
 118        proc_handler *proc_handler;     /* Callback for text formatting */
 119        struct ctl_table_poll *poll;
 120        void *extra1;
 121        void *extra2;
 122} __randomize_layout;
 123
 124struct ctl_node {
 125        struct rb_node node;
 126        struct ctl_table_header *header;
 127};
 128
 129/* struct ctl_table_header is used to maintain dynamic lists of
 130   struct ctl_table trees. */
 131struct ctl_table_header {
 132        union {
 133                struct {
 134                        struct ctl_table *ctl_table;
 135                        int used;
 136                        int count;
 137                        int nreg;
 138                };
 139                struct rcu_head rcu;
 140        };
 141        struct completion *unregistering;
 142        struct ctl_table *ctl_table_arg;
 143        struct ctl_table_root *root;
 144        struct ctl_table_set *set;
 145        struct ctl_dir *parent;
 146        struct ctl_node *node;
 147        struct hlist_head inodes; /* head for proc_inode->sysctl_inodes */
 148};
 149
 150struct ctl_dir {
 151        /* Header must be at the start of ctl_dir */
 152        struct ctl_table_header header;
 153        struct rb_root root;
 154};
 155
 156struct ctl_table_set {
 157        int (*is_seen)(struct ctl_table_set *);
 158        struct ctl_dir dir;
 159};
 160
 161struct ctl_table_root {
 162        struct ctl_table_set default_set;
 163        struct ctl_table_set *(*lookup)(struct ctl_table_root *root);
 164        void (*set_ownership)(struct ctl_table_header *head,
 165                              struct ctl_table *table,
 166                              kuid_t *uid, kgid_t *gid);
 167        int (*permissions)(struct ctl_table_header *head, struct ctl_table *table);
 168};
 169
 170/* struct ctl_path describes where in the hierarchy a table is added */
 171struct ctl_path {
 172        const char *procname;
 173};
 174
 175#ifdef CONFIG_SYSCTL
 176
 177void proc_sys_poll_notify(struct ctl_table_poll *poll);
 178
 179extern void setup_sysctl_set(struct ctl_table_set *p,
 180        struct ctl_table_root *root,
 181        int (*is_seen)(struct ctl_table_set *));
 182extern void retire_sysctl_set(struct ctl_table_set *set);
 183
 184struct ctl_table_header *__register_sysctl_table(
 185        struct ctl_table_set *set,
 186        const char *path, struct ctl_table *table);
 187struct ctl_table_header *__register_sysctl_paths(
 188        struct ctl_table_set *set,
 189        const struct ctl_path *path, struct ctl_table *table);
 190struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table);
 191struct ctl_table_header *register_sysctl_table(struct ctl_table * table);
 192struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
 193                                                struct ctl_table *table);
 194
 195void unregister_sysctl_table(struct ctl_table_header * table);
 196
 197extern int sysctl_init(void);
 198void do_sysctl_args(void);
 199
 200extern int pwrsw_enabled;
 201extern int unaligned_enabled;
 202extern int unaligned_dump_stack;
 203extern int no_unaligned_warning;
 204
 205extern struct ctl_table sysctl_mount_point[];
 206extern struct ctl_table random_table[];
 207extern struct ctl_table firmware_config_table[];
 208extern struct ctl_table epoll_table[];
 209
 210#else /* CONFIG_SYSCTL */
 211static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
 212{
 213        return NULL;
 214}
 215
 216static inline struct ctl_table_header *register_sysctl_paths(
 217                        const struct ctl_path *path, struct ctl_table *table)
 218{
 219        return NULL;
 220}
 221
 222static inline struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
 223{
 224        return NULL;
 225}
 226
 227static inline void unregister_sysctl_table(struct ctl_table_header * table)
 228{
 229}
 230
 231static inline void setup_sysctl_set(struct ctl_table_set *p,
 232        struct ctl_table_root *root,
 233        int (*is_seen)(struct ctl_table_set *))
 234{
 235}
 236
 237static inline void do_sysctl_args(void)
 238{
 239}
 240#endif /* CONFIG_SYSCTL */
 241
 242int sysctl_max_threads(struct ctl_table *table, int write, void *buffer,
 243                size_t *lenp, loff_t *ppos);
 244
 245#endif /* _LINUX_SYSCTL_H */
 246