1.\" 2.\" Copyright (c) 2006 Robert N. M. Watson 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" 27.Dd December 2, 2019 28.Dt SYSCTL 9 29.Os 30.Sh NAME 31.Nm SYSCTL_BIT32 , 32.Nm SYSCTL_BIT64 , 33.Nm SYSCTL_DECL , 34.Nm SYSCTL_INT , 35.Nm SYSCTL_LONG , 36.Nm SYSCTL_QUAD , 37.Nm SYSCTL_NODE , 38.Nm SYSCTL_OPAQUE , 39.Nm SYSCTL_PROC , 40.Nm SYSCTL_S8 , 41.Nm SYSCTL_S16 , 42.Nm SYSCTL_S32 , 43.Nm SYSCTL_S64 , 44.Nm SYSCTL_STRING , 45.Nm SYSCTL_STRUCT , 46.Nm SYSCTL_U8 , 47.Nm SYSCTL_U16 , 48.Nm SYSCTL_U32 , 49.Nm SYSCTL_U64 , 50.Nm SYSCTL_UINT , 51.Nm SYSCTL_ULONG , 52.Nm SYSCTL_UQUAD 53.Nd Static sysctl declaration functions 54.Sh SYNOPSIS 55.In sys/types.h 56.In sys/sysctl.h 57.Fo SYSCTL_BIT32 58.Fa "parent" 59.Fa "nbr" 60.Fa "name" 61.Fa "access" 62.Fa "ptr" 63.Fa "val" 64.Fa "bit" 65.Fa "descr" 66.Fc 67.Fo SYSCTL_BIT64 68.Fa "parent" 69.Fa "nbr" 70.Fa "name" 71.Fa "access" 72.Fa "ptr" 73.Fa "val" 74.Fa "bit" 75.Fa "descr" 76.Fc 77.Fo SYSCTL_DECL 78.Fa "name" 79.Fc 80.Fo SYSCTL_INT 81.Fa "parent" 82.Fa "nbr" 83.Fa "name" 84.Fa "access" 85.Fa "ptr" 86.Fa "val" 87.Fa "descr" 88.Fc 89.Fo SYSCTL_LONG 90.Fa "parent" 91.Fa "nbr" 92.Fa "name" 93.Fa "access" 94.Fa "ptr" 95.Fa "val" 96.Fa "descr" 97.Fc 98.Fo SYSCTL_NODE 99.Fa "parent" 100.Fa "nbr" 101.Fa "name" 102.Fa "access" 103.Fa "handler" 104.Fa "descr" 105.Fc 106.Fo SYSCTL_OPAQUE 107.Fa "parent" 108.Fa "nbr" 109.Fa "name" 110.Fa "access" 111.Fa "ptr" 112.Fa "len" 113.Fa "fmt" 114.Fa "descr" 115.Fc 116.Fo SYSCTL_PROC 117.Fa "parent" 118.Fa "nbr" 119.Fa "name" 120.Fa "access" 121.Fa "ptr" 122.Fa "arg" 123.Fa "handler" 124.Fa "fmt" 125.Fa "descr" 126.Fc 127.Fo SYSCTL_QUAD 128.Fa "parent" 129.Fa "nbr" 130.Fa "name" 131.Fa "access" 132.Fa "ptr" 133.Fa "val" 134.Fa "descr" 135.Fc 136.Fo SYSCTL_S8 137.Fa "parent" 138.Fa "number" 139.Fa "name" 140.Fa "access" 141.Fa "ptr" 142.Fa "val" 143.Fa "descr" 144.Fc 145.Fo SYSCTL_S16 146.Fa "parent" 147.Fa "number" 148.Fa "name" 149.Fa "access" 150.Fa "ptr" 151.Fa "val" 152.Fa "descr" 153.Fc 154.Fo SYSCTL_S32 155.Fa "parent" 156.Fa "number" 157.Fa "name" 158.Fa "access" 159.Fa "ptr" 160.Fa "val" 161.Fa "descr" 162.Fc 163.Fo SYSCTL_S64 164.Fa "parent" 165.Fa "number" 166.Fa "name" 167.Fa "access" 168.Fa "ptr" 169.Fa "val" 170.Fa "descr" 171.Fc 172.Fo SYSCTL_STRING 173.Fa "parent" 174.Fa "nbr" 175.Fa "name" 176.Fa "access" 177.Fa "arg" 178.Fa "len" 179.Fa "descr" 180.Fc 181.Fo SYSCTL_STRUCT 182.Fa "parent" 183.Fa "nbr" 184.Fa "name" 185.Fa "access" 186.Fa "ptr" 187.Fa "type" 188.Fa "descr" 189.Fc 190.Fo SYSCTL_U8 191.Fa "parent" 192.Fa "number" 193.Fa "name" 194.Fa "access" 195.Fa "ptr" 196.Fa "val" 197.Fa "descr" 198.Fc 199.Fo SYSCTL_U16 200.Fa "parent" 201.Fa "number" 202.Fa "name" 203.Fa "access" 204.Fa "ptr" 205.Fa "val" 206.Fa "descr" 207.Fc 208.Fo SYSCTL_U32 209.Fa "parent" 210.Fa "number" 211.Fa "name" 212.Fa "access" 213.Fa "ptr" 214.Fa "val" 215.Fa "descr" 216.Fc 217.Fo SYSCTL_U64 218.Fa "parent" 219.Fa "number" 220.Fa "name" 221.Fa "access" 222.Fa "ptr" 223.Fa "val" 224.Fa "descr" 225.Fc 226.Fo SYSCTL_UINT 227.Fa "parent" 228.Fa "nbr" 229.Fa "name" 230.Fa "access" 231.Fa "ptr" 232.Fa "val" 233.Fa "descr" 234.Fc 235.Fo SYSCTL_ULONG 236.Fa "parent" 237.Fa "nbr" 238.Fa "name" 239.Fa "access" 240.Fa "ptr" 241.Fa "val" 242.Fa "descr" 243.Fc 244.Fo SYSCTL_UQUAD 245.Fa "parent" 246.Fa "nbr" 247.Fa "name" 248.Fa "access" 249.Fa "ptr" 250.Fa "val" 251.Fa "descr" 252.Fc 253.Sh DESCRIPTION 254The 255.Nm 256kernel interfaces allow code to statically declare 257.Xr sysctl 8 258MIB entries, which will be initialized when the kernel module containing the 259declaration is initialized. 260When the module is unloaded, the sysctl will be automatically destroyed. 261.Pp 262Sysctl nodes are created in a hierarchical tree, with all static nodes being 263represented by named C data structures; in order to create a new node under 264an existing node in the tree, the structure representing the desired parent 265node must be declared in the current context using 266.Fn SYSCTL_DECL . 267.Pp 268New nodes are declared using one of 269.Nm SYSCTL_BIT32 , 270.Nm SYSCTL_BIT64 , 271.Nm SYSCTL_INT , 272.Nm SYSCTL_LONG , 273.Nm SYSCTL_QUAD , 274.Nm SYSCTL_NODE , 275.Nm SYSCTL_OPAQUE , 276.Nm SYSCTL_PROC , 277.Nm SYSCTL_S8 , 278.Nm SYSCTL_S16 , 279.Nm SYSCTL_S32 , 280.Nm SYSCTL_S64 , 281.Nm SYSCTL_STRING , 282.Nm SYSCTL_STRUCT , 283.Nm SYSCTL_U8 , 284.Nm SYSCTL_U16 , 285.Nm SYSCTL_U32 , 286.Nm SYSCTL_U64 , 287.Nm SYSCTL_UINT , 288.Nm SYSCTL_ULONG , 289and 290.Nm SYSCTL_UQUAD . 291Each macro accepts a parent name, as declared using 292.Nm SYSCTL_DECL , 293an OID number, typically 294.Dv OID_AUTO , 295a node name, a set of control and access flags, and a description. 296Depending on the macro, a pointer to a variable supporting the MIB entry, a 297size, a value, and a function pointer implementing the MIB entry may also be 298present. 299.Pp 300For most of the above macros, declaring a type as part of the access flags is 301not necessary -- however, when declaring a sysctl implemented by a function, 302including a type in the access mask is required: 303.Bl -tag -width ".Dv CTLTYPE_STRING" 304.It Dv CTLTYPE_NODE 305This is a node intended to be a parent for other nodes. 306.It Dv CTLTYPE_INT 307This is a signed integer. 308.It Dv CTLTYPE_S8 309This is an 8-bit signed integer. 310.It Dv CTLTYPE_S16 311This is a 16-bit signed integer. 312.It Dv CTLTYPE_S32 313This is a 32-bit signed integer. 314.It Dv CTLTYPE_S64 315This is a 64-bit signed integer. 316.It Dv CTLTYPE_STRING 317This is a nul-terminated string stored in a character array. 318.It Dv CTLTYPE_QUAD 319This is a 64-bit signed integer. 320.It Dv CTLTYPE_OPAQUE 321This is an opaque data structure. 322.It Dv CTLTYPE_STRUCT 323Alias for 324.Dv CTLTYPE_OPAQUE . 325.It Dv CTLTYPE_U8 326This is an 8-bit unsigned integer. 327.It Dv CTLTYPE_U16 328This is a 16-bit unsigned integer. 329.It Dv CTLTYPE_U32 330This is a 32-bit unsigned integer. 331.It Dv CTLTYPE_U64 332This is a 64-bit unsigned integer. 333.It Dv CTLTYPE_UINT 334This is an unsigned integer. 335.It Dv CTLTYPE_LONG 336This is a signed long. 337.It Dv CTLTYPE_ULONG 338This is an unsigned long. 339.It Dv CTLTYPE_UQUAD 340This is a 64-bit unsigned integer. 341.El 342.Pp 343All sysctl types except for new node declarations require one or more flags 344to be set indicating the read and write disposition of the sysctl: 345.Bl -tag -width ".Dv CTLFLAG_ANYBODY" 346.It Dv CTLFLAG_RD 347This is a read-only sysctl. 348.It Dv CTLFLAG_WR 349This is a writable sysctl. 350.It Dv CTLFLAG_RW 351This sysctl is readable and writable. 352.It Dv CTLFLAG_ANYBODY 353Any user or process can write to this sysctl. 354.It Dv CTLFLAG_SECURE 355This sysctl can be written to only if the effective securelevel of the 356process is <= 0. 357.It Dv CTLFLAG_PRISON 358This sysctl can be written to by processes in 359.Xr jail 2 . 360.\".It Dv CTLFLAG_SKIP 361.\"When iterating the sysctl name space, do not list this sysctl. 362.El 363.Pp 364When creating new sysctls, careful attention should be paid to the security 365implications of the monitoring or management interface being created. 366Most sysctls present in the kernel are read-only or writable only by the 367superuser. 368Sysctls exporting extensive information on system data structures and 369operation, especially those implemented using procedures, will wish to 370implement access control to limit the undesired exposure of information about 371other processes, network connections, etc. 372.Pp 373The following top level sysctl name spaces are commonly used: 374.Bl -tag -width ".Va machdep" 375.It Va compat 376Compatibility layer information. 377.It Va debug 378Debugging information. 379Various name spaces exist under 380.Va debug . 381.It Va hw 382Hardware and device driver information. 383.It Va lwkt 384Information about the LWKT subsystem. 385.It Va kern 386Kernel behavior tuning; generally deprecated in favor of more specific 387name spaces. 388.It Va machdep 389Machine-dependent configuration parameters. 390.It Va net 391Network subsystem. 392Various protocols have name spaces under 393.Va net . 394.It Va sysctl 395Reserved name space for the implementation of sysctl. 396.It Va user 397Configuration settings relating to user application behavior. 398Generally, configuring applications using kernel sysctls is discouraged. 399.It Va vfs 400Virtual file system configuration and information. 401.It Va vm 402Virtual memory subsystem configuration and information. 403.El 404.Sh EXAMPLES 405Sample use of 406.Nm SYSCTL_DECL 407to declare the "machdep" sysctl tree for use by new nodes: 408.Bd -literal -offset indent 409SYSCTL_DECL(_machdep); 410.Ed 411.Pp 412Examples of integer, opaque, string, and procedure sysctls follow: 413.Bd -literal -offset indent 414/* 415 * Example of a constant integer value. Notice that the control 416 * flags are CTLFLAG_RD, the variable pointer is NULL, and the 417 * value is declared. 418 */ 419SYSCTL_INT(_debug_sizeof, OID_AUTO, bio, CTLFLAG_RD, NULL, 420 sizeof(struct bio), "sizeof(struct bio)"); 421 422/* 423 * Example of a variable integer value. Notice that the control 424 * flags are CTLFLAG_RW, the variable pointer is set, and the 425 * value is 0. 426 */ 427static int doingcache = 1; /* 1 => enable the cache */ 428SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0, 429 "Enable name cache"); 430 431/* 432 * Example of a variable string value. Notice that the control 433 * flags are CTLFLAG_RW, that the variable pointer and string 434 * size are set. Unlike newer sysctls, this older sysctl uses a 435 * static oid number. 436 */ 437char kernelname[MAXPATHLEN] = "/boot/kernel"; /* XXX bloat */ 438SYSCTL_STRING(_kern, KERN_BOOTFILE, bootfile, CTLFLAG_RW, 439 kernelname, sizeof(kernelname), "Name of kernel file booted"); 440 441/* 442 * Example of an opaque data type exported by sysctl. Notice that 443 * the variable pointer and size are provided, as well as a format 444 * string for sysctl(8). 445 */ 446static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 447SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, 448 &pps_freq, sizeof(pps_freq), "I", ""); 449 450/* 451 * Example of a procedure based sysctl exporting string 452 * information. Notice that the data type is declared, the NULL 453 * variable pointer and 0 size, the function pointer, and the 454 * format string for sysctl(8). 455 */ 456SYSCTL_PROC(_kern, OID_AUTO, msgbuf, CTLTYPE_STRING | CTLFLAG_RD, 457 0, 0, sysctl_kern_msgbuf, "A", "Contents of kernel message buffer"); 458.Ed 459.Pp 460When adding, modifying, or removing sysctl names, it is important to be 461aware that these interfaces may be used by users, libraries, applications, 462or documentation (such as published books), and are implicitly published 463application interfaces. 464As with other application interfaces, caution must be taken not to break 465existing applications, and to think about future use of new name spaces so as 466to avoid the need to rename or remove interfaces that might be depended on in 467the future. 468.Sh SEE ALSO 469.Xr sysctl 8 , 470.Xr sysctl_add_oid 9 , 471.Xr sysctl_ctx_free 9 , 472.Xr sysctl_ctx_init 9 , 473.Xr sysctl_remove_oid 9 474.Sh HISTORY 475.Xr sysctl 8 476first appeared in 477.Bx 4.4 . 478.Sh AUTHORS 479.An -nosplit 480The sysctl implementation originally found in 481.Bx 482has been extensively rewritten by 483.An Poul-Henning Kamp 484in order to add support for name lookups, name space iteration, and dynamic 485addition of MIB nodes. 486.Pp 487This man page was written by 488.An Robert N. M. Watson . 489