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 */
  33 struct completion;
  34 struct ctl_table;
  35 struct nsproxy;
  36 struct ctl_table_root;
  37 struct ctl_table_header;
  38 struct 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_TWO                      ((void *)&sysctl_vals[2])
  44 #define SYSCTL_THREE                    ((void *)&sysctl_vals[3])
  45 #define SYSCTL_FOUR                     ((void *)&sysctl_vals[4])
  46 #define SYSCTL_ONE_HUNDRED              ((void *)&sysctl_vals[5])
  47 #define SYSCTL_TWO_HUNDRED              ((void *)&sysctl_vals[6])
  48 #define SYSCTL_ONE_THOUSAND             ((void *)&sysctl_vals[7])
  49 #define SYSCTL_THREE_THOUSAND           ((void *)&sysctl_vals[8])
  50 #define SYSCTL_INT_MAX                  ((void *)&sysctl_vals[9])
  51
  52 /* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
  53 #define SYSCTL_MAXOLDUID                ((void *)&sysctl_vals[10])
  54 #define SYSCTL_NEG_ONE                  ((void *)&sysctl_vals[11])
  55
  56 extern const int sysctl_vals[];
  57
  58 #define SYSCTL_LONG_ZERO        ((void *)&sysctl_long_vals[0])
  59 #define SYSCTL_LONG_ONE         ((void *)&sysctl_long_vals[1])
  60 #define SYSCTL_LONG_MAX         ((void *)&sysctl_long_vals[2])
  61
  62 extern const unsigned long sysctl_long_vals[];
  63
  64 typedef int proc_handler(const struct ctl_table *ctl, int write, void *buffer,
  65                 size_t *lenp, loff_t *ppos);
  66
  67 int proc_dostring(const struct ctl_table *, int, void *, size_t *, loff_t *);
  68 int proc_dobool(const struct ctl_table *table, int write, void *buffer,
  69                 size_t *lenp, loff_t *ppos);
  70 int proc_dointvec(const struct ctl_table *, int, void *, size_t *, loff_t *);
  71 int proc_douintvec(const struct ctl_table *, int, void *, size_t *, loff_t *);
  72 int proc_dointvec_minmax(const struct ctl_table *, int, void *, size_t *, loff_t *);
  73 int proc_douintvec_minmax(const struct ctl_table *table, int write, void *buffer,
  74                 size_t *lenp, loff_t *ppos);
  75 int proc_dou8vec_minmax(const struct ctl_table *table, int write, void *buffer,
  76                         size_t *lenp, loff_t *ppos);
  77 int proc_dointvec_jiffies(const struct ctl_table *, int, void *, size_t *, loff_t *);
  78 int proc_dointvec_ms_jiffies_minmax(const struct ctl_table *table, int write,
  79                 void *buffer, size_t *lenp, loff_t *ppos);
  80 int proc_dointvec_userhz_jiffies(const struct ctl_table *, int, void *, size_t *,
  81                 loff_t *);
  82 int proc_dointvec_ms_jiffies(const struct ctl_table *, int, void *, size_t *,
  83                 loff_t *);
  84 int proc_doulongvec_minmax(const struct ctl_table *, int, void *, size_t *, loff_t *);
  85 int proc_doulongvec_ms_jiffies_minmax(const struct ctl_table *table, int, void *,
  86                 size_t *, loff_t *);
  87 int proc_do_large_bitmap(const struct ctl_table *, int, void *, size_t *, loff_t *);
  88 int proc_do_static_key(const struct ctl_table *table, int write, void *buffer,
  89                 size_t *lenp, loff_t *ppos);
  90
  91 /*
  92  * Register a set of sysctl names by calling register_sysctl
  93  * with an initialised array of struct ctl_table's.  An entry with
  94  * NULL procname terminates the table.  table->de will be
  95  * set up by the registration and need not be initialised in advance.
  96  *
  97  * sysctl names can be mirrored automatically under /proc/sys.  The
  98  * procname supplied controls /proc naming.
  99  *
 100  * The table's mode will be honoured for proc-fs access.
 101  *
 102  * Leaf nodes in the sysctl tree will be represented by a single file
 103  * under /proc; non-leaf nodes will be represented by directories.  A
 104  * null procname disables /proc mirroring at this node.
 105  *
 106  * The data and maxlen fields of the ctl_table
 107  * struct enable minimal validation of the values being written to be
 108  * performed, and the mode field allows minimal authentication.
 109  *
 110  * There must be a proc_handler routine for any terminal nodes
 111  * mirrored under /proc/sys (non-terminals are handled by a built-in
 112  * directory handler).  Several default handlers are available to
 113  * cover common cases.
 114  */
 115
 116 /* Support for userspace poll() to watch for changes */
 117 struct ctl_table_poll {
 118         atomic_t event;
 119         wait_queue_head_t wait;
 120 };
 121
 122 static inline void *proc_sys_poll_event(struct ctl_table_poll *poll)
 123 {
 124         return (void *)(unsigned long)atomic_read(&poll->event);
 125 }
 126
 127 #define __CTL_TABLE_POLL_INITIALIZER(name) {                            \
 128         .event = ATOMIC_INIT(0),                                        \
 129         .wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.wait) }
 130
 131 #define DEFINE_CTL_TABLE_POLL(name)                                     \
 132         struct ctl_table_poll name = __CTL_TABLE_POLL_INITIALIZER(name)
 133
 134 /* A sysctl table is an array of struct ctl_table: */
 135 struct ctl_table {
 136         const char *procname;           /* Text ID for /proc/sys, or zero */
 137         void *data;
 138         int maxlen;
 139         umode_t mode;
 140         proc_handler *proc_handler;     /* Callback for text formatting */
 141         struct ctl_table_poll *poll;
 142         void *extra1;
 143         void *extra2;
 144 } __randomize_layout;
 145
 146 struct ctl_node {
 147         struct rb_node node;
 148         struct ctl_table_header *header;
 149 };
 150
 151 /**
 152  * struct ctl_table_header - maintains dynamic lists of struct ctl_table trees
 153  * @ctl_table: pointer to the first element in ctl_table array
 154  * @ctl_table_size: number of elements pointed by @ctl_table
 155  * @used: The entry will never be touched when equal to 0.
 156  * @count: Upped every time something is added to @inodes and downed every time
 157  *         something is removed from inodes
 158  * @nreg: When nreg drops to 0 the ctl_table_header will be unregistered.
 159  * @rcu: Delays the freeing of the inode. Introduced with "unfuck proc_sysctl ->d_compare()"
 160  *
 161  */
 162 struct ctl_table_header {
 163         union {
 164                 struct {
 165                         struct ctl_table *ctl_table;
 166                         int ctl_table_size;
 167                         int used;
 168                         int count;
 169                         int nreg;
 170                 };
 171                 struct rcu_head rcu;
 172         };
 173         struct completion *unregistering;
 174         const struct ctl_table *ctl_table_arg;
 175         struct ctl_table_root *root;
 176         struct ctl_table_set *set;
 177         struct ctl_dir *parent;
 178         struct ctl_node *node;
 179         struct hlist_head inodes; /* head for proc_inode->sysctl_inodes */
 180         /**
 181          * enum type - Enumeration to differentiate between ctl target types
 182          * @SYSCTL_TABLE_TYPE_DEFAULT: ctl target with no special considerations
 183          * @SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY: Used to identify a permanently
 184          *                                       empty directory target to serve
 185          *                                       as mount point.
 186          */
 187         enum {
 188                 SYSCTL_TABLE_TYPE_DEFAULT,
 189                 SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY,
 190         } type;
 191 };
 192
 193 struct ctl_dir {
 194         /* Header must be at the start of ctl_dir */
 195         struct ctl_table_header header;
 196         struct rb_root root;
 197 };
 198
 199 struct ctl_table_set {
 200         int (*is_seen)(struct ctl_table_set *);
 201         struct ctl_dir dir;
 202 };
 203
 204 struct ctl_table_root {
 205         struct ctl_table_set default_set;
 206         struct ctl_table_set *(*lookup)(struct ctl_table_root *root);
 207         void (*set_ownership)(struct ctl_table_header *head,
 208                               kuid_t *uid, kgid_t *gid);
 209         int (*permissions)(struct ctl_table_header *head, const struct ctl_table *table);
 210 };
 211
 212 #define register_sysctl(path, table)    \
 213         register_sysctl_sz(path, table, ARRAY_SIZE(table))
 214
 215 #ifdef CONFIG_SYSCTL
 216
 217 void proc_sys_poll_notify(struct ctl_table_poll *poll);
 218
 219 extern void setup_sysctl_set(struct ctl_table_set *p,
 220         struct ctl_table_root *root,
 221         int (*is_seen)(struct ctl_table_set *));
 222 extern void retire_sysctl_set(struct ctl_table_set *set);
 223
 224 struct ctl_table_header *__register_sysctl_table(
 225         struct ctl_table_set *set,
 226         const char *path, struct ctl_table *table, size_t table_size);
 227 struct ctl_table_header *register_sysctl_sz(const char *path, struct ctl_table *table,
 228                                             size_t table_size);
 229 void unregister_sysctl_table(struct ctl_table_header * table);
 230
 231 extern int sysctl_init_bases(void);
 232 extern void __register_sysctl_init(const char *path, struct ctl_table *table,
 233                                  const char *table_name, size_t table_size);
 234 #define register_sysctl_init(path, table)       \
 235         __register_sysctl_init(path, table, #table, ARRAY_SIZE(table))
 236 extern struct ctl_table_header *register_sysctl_mount_point(const char *path);
 237
 238 void do_sysctl_args(void);
 239 bool sysctl_is_alias(char *param);
 240 int do_proc_douintvec(const struct ctl_table *table, int write,
 241                       void *buffer, size_t *lenp, loff_t *ppos,
 242                       int (*conv)(unsigned long *lvalp,
 243                                   unsigned int *valp,
 244                                   int write, void *data),
 245                       void *data);
 246
 247 extern int pwrsw_enabled;
 248 extern int unaligned_enabled;
 249 extern int unaligned_dump_stack;
 250 extern int no_unaligned_warning;
 251
 252 #else /* CONFIG_SYSCTL */
 253
 254 static inline void register_sysctl_init(const char *path, struct ctl_table *table)
 255 {
 256 }
 257
 258 static inline struct ctl_table_header *register_sysctl_mount_point(const char *path)
 259 {
 260         return NULL;
 261 }
 262
 263 static inline struct ctl_table_header *register_sysctl_sz(const char *path,
 264                                                           struct ctl_table *table,
 265                                                           size_t table_size)
 266 {
 267         return NULL;
 268 }
 269
 270 static inline void unregister_sysctl_table(struct ctl_table_header * table)
 271 {
 272 }
 273
 274 static inline void setup_sysctl_set(struct ctl_table_set *p,
 275         struct ctl_table_root *root,
 276         int (*is_seen)(struct ctl_table_set *))
 277 {
 278 }
 279
 280 static inline void do_sysctl_args(void)
 281 {
 282 }
 283
 284 static inline bool sysctl_is_alias(char *param)
 285 {
 286         return false;
 287 }
 288 #endif /* CONFIG_SYSCTL */
 289
 290 int sysctl_max_threads(const struct ctl_table *table, int write, void *buffer,
 291                 size_t *lenp, loff_t *ppos);
 292
 293 #endif /* _LINUX_SYSCTL_H */