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.
  94  *
  95  * sysctl names can be mirrored automatically under /proc/sys.  The
  96  * procname supplied controls /proc naming.
  97  *
  98  * The table's mode will be honoured for proc-fs access.
  99  *
 100  * Leaf nodes in the sysctl tree will be represented by a single file
 101  * under /proc; non-leaf nodes will be represented by directories.  A
 102  * null procname disables /proc mirroring at this node.
 103  *
 104  * The data and maxlen fields of the ctl_table
 105  * struct enable minimal validation of the values being written to be
 106  * performed, and the mode field allows minimal authentication.
 107  *
 108  * There must be a proc_handler routine for any terminal nodes
 109  * mirrored under /proc/sys (non-terminals are handled by a built-in
 110  * directory handler).  Several default handlers are available to
 111  * cover common cases.
 112  */
 113
 114 /* Support for userspace poll() to watch for changes */
 115 struct ctl_table_poll {
 116         atomic_t event;
 117         wait_queue_head_t wait;
 118 };
 119
 120 static inline void *proc_sys_poll_event(struct ctl_table_poll *poll)
 121 {
 122         return (void *)(unsigned long)atomic_read(&poll->event);
 123 }
 124
 125 #define __CTL_TABLE_POLL_INITIALIZER(name) {                            \
 126         .event = ATOMIC_INIT(0),                                        \
 127         .wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.wait) }
 128
 129 #define DEFINE_CTL_TABLE_POLL(name)                                     \
 130         struct ctl_table_poll name = __CTL_TABLE_POLL_INITIALIZER(name)
 131
 132 /* A sysctl table is an array of struct ctl_table: */
 133 struct ctl_table {
 134         const char *procname;           /* Text ID for /proc/sys */
 135         void *data;
 136         int maxlen;
 137         umode_t mode;
 138         proc_handler *proc_handler;     /* Callback for text formatting */
 139         struct ctl_table_poll *poll;
 140         void *extra1;
 141         void *extra2;
 142 } __randomize_layout;
 143
 144 struct ctl_node {
 145         struct rb_node node;
 146         struct ctl_table_header *header;
 147 };
 148
 149 /**
 150  * struct ctl_table_header - maintains dynamic lists of struct ctl_table trees
 151  * @ctl_table: pointer to the first element in ctl_table array
 152  * @ctl_table_size: number of elements pointed by @ctl_table
 153  * @used: The entry will never be touched when equal to 0.
 154  * @count: Upped every time something is added to @inodes and downed every time
 155  *         something is removed from inodes
 156  * @nreg: When nreg drops to 0 the ctl_table_header will be unregistered.
 157  * @rcu: Delays the freeing of the inode. Introduced with "unfuck proc_sysctl ->d_compare()"
 158  *
 159  */
 160 struct ctl_table_header {
 161         union {
 162                 struct {
 163                         const struct ctl_table *ctl_table;
 164                         int ctl_table_size;
 165                         int used;
 166                         int count;
 167                         int nreg;
 168                 };
 169                 struct rcu_head rcu;
 170         };
 171         struct completion *unregistering;
 172         const struct ctl_table *ctl_table_arg;
 173         struct ctl_table_root *root;
 174         struct ctl_table_set *set;
 175         struct ctl_dir *parent;
 176         struct ctl_node *node;
 177         struct hlist_head inodes; /* head for proc_inode->sysctl_inodes */
 178         /**
 179          * enum type - Enumeration to differentiate between ctl target types
 180          * @SYSCTL_TABLE_TYPE_DEFAULT: ctl target with no special considerations
 181          * @SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY: Used to identify a permanently
 182          *                                       empty directory target to serve
 183          *                                       as mount point.
 184          */
 185         enum {
 186                 SYSCTL_TABLE_TYPE_DEFAULT,
 187                 SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY,
 188         } type;
 189 };
 190
 191 struct ctl_dir {
 192         /* Header must be at the start of ctl_dir */
 193         struct ctl_table_header header;
 194         struct rb_root root;
 195 };
 196
 197 struct ctl_table_set {
 198         int (*is_seen)(struct ctl_table_set *);
 199         struct ctl_dir dir;
 200 };
 201
 202 struct ctl_table_root {
 203         struct ctl_table_set default_set;
 204         struct ctl_table_set *(*lookup)(struct ctl_table_root *root);
 205         void (*set_ownership)(struct ctl_table_header *head,
 206                               kuid_t *uid, kgid_t *gid);
 207         int (*permissions)(struct ctl_table_header *head, const struct ctl_table *table);
 208 };
 209
 210 #define register_sysctl(path, table)    \
 211         register_sysctl_sz(path, table, ARRAY_SIZE(table))
 212
 213 #ifdef CONFIG_SYSCTL
 214
 215 void proc_sys_poll_notify(struct ctl_table_poll *poll);
 216
 217 extern void setup_sysctl_set(struct ctl_table_set *p,
 218         struct ctl_table_root *root,
 219         int (*is_seen)(struct ctl_table_set *));
 220 extern void retire_sysctl_set(struct ctl_table_set *set);
 221
 222 struct ctl_table_header *__register_sysctl_table(
 223         struct ctl_table_set *set,
 224         const char *path, const struct ctl_table *table, size_t table_size);
 225 struct ctl_table_header *register_sysctl_sz(const char *path, const struct ctl_table *table,
 226                                             size_t table_size);
 227 void unregister_sysctl_table(struct ctl_table_header * table);
 228
 229 extern int sysctl_init_bases(void);
 230 extern void __register_sysctl_init(const char *path, const struct ctl_table *table,
 231                                  const char *table_name, size_t table_size);
 232 #define register_sysctl_init(path, table)       \
 233         __register_sysctl_init(path, table, #table, ARRAY_SIZE(table))
 234 extern struct ctl_table_header *register_sysctl_mount_point(const char *path);
 235
 236 void do_sysctl_args(void);
 237 bool sysctl_is_alias(char *param);
 238 int do_proc_douintvec(const struct ctl_table *table, int write,
 239                       void *buffer, size_t *lenp, loff_t *ppos,
 240                       int (*conv)(unsigned long *lvalp,
 241                                   unsigned int *valp,
 242                                   int write, void *data),
 243                       void *data);
 244
 245 extern int pwrsw_enabled;
 246 extern int unaligned_enabled;
 247 extern int unaligned_dump_stack;
 248 extern int no_unaligned_warning;
 249
 250 #else /* CONFIG_SYSCTL */
 251
 252 static inline void register_sysctl_init(const char *path, const struct ctl_table *table)
 253 {
 254 }
 255
 256 static inline struct ctl_table_header *register_sysctl_mount_point(const char *path)
 257 {
 258         return NULL;
 259 }
 260
 261 static inline struct ctl_table_header *register_sysctl_sz(const char *path,
 262                                                           const struct ctl_table *table,
 263                                                           size_t table_size)
 264 {
 265         return NULL;
 266 }
 267
 268 static inline void unregister_sysctl_table(struct ctl_table_header * table)
 269 {
 270 }
 271
 272 static inline void setup_sysctl_set(struct ctl_table_set *p,
 273         struct ctl_table_root *root,
 274         int (*is_seen)(struct ctl_table_set *))
 275 {
 276 }
 277
 278 static inline void do_sysctl_args(void)
 279 {
 280 }
 281
 282 static inline bool sysctl_is_alias(char *param)
 283 {
 284         return false;
 285 }
 286 #endif /* CONFIG_SYSCTL */
 287
 288 int sysctl_max_threads(const struct ctl_table *table, int write, void *buffer,
 289                 size_t *lenp, loff_t *ppos);
 290
 291 #endif /* _LINUX_SYSCTL_H */