1.\" 2.\" Copyright (c) 2000, Andrzej Bialecki <abial@FreeBSD.org> 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.\" 3. The name of the author may not be used to endorse or promote products 14.\" derived from this software without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" $FreeBSD$ 29.\" 30.Dd September 12, 2013 31.Dt SYSCTL_ADD_OID 9 32.Os 33.Sh NAME 34.Nm sysctl_add_oid , 35.Nm sysctl_move_oid , 36.Nm sysctl_remove_oid 37.Nd runtime sysctl tree manipulation 38.Sh SYNOPSIS 39.In sys/types.h 40.In sys/sysctl.h 41.Ft struct sysctl_oid * 42.Fo sysctl_add_oid 43.Fa "struct sysctl_ctx_list *ctx" 44.Fa "struct sysctl_oid_list *parent" 45.Fa "int number" 46.Fa "const char *name" 47.Fa "int kind" 48.Fa "void *arg1" 49.Fa "int arg2" 50.Fa "int (*handler) (SYSCTL_HANDLER_ARGS)" 51.Fa "const char *format" 52.Fa "const char *descr" 53.Fc 54.Ft int 55.Fo sysctl_move_oid 56.Fa "struct sysctl_oid *oidp" 57.Fa "struct sysctl_oid_list *parent" 58.Fc 59.Ft int 60.Fo sysctl_remove_oid 61.Fa "struct sysctl_oid *oidp" 62.Fa "int del" 63.Fa "int recurse" 64.Fc 65.Ft struct sysctl_oid_list * 66.Fo SYSCTL_CHILDREN 67.Fa "struct sysctl_oid *oidp" 68.Fc 69.Ft struct sysctl_oid_list * 70.Fo SYSCTL_STATIC_CHILDREN 71.Fa "struct sysctl_oid_list OID_NAME" 72.Fc 73.Ft struct sysctl_oid * 74.Fo SYSCTL_ADD_OID 75.Fa "struct sysctl_ctx_list *ctx" 76.Fa "struct sysctl_oid_list *parent" 77.Fa "int number" 78.Fa "const char *name" 79.Fa "int kind" 80.Fa "void *arg1" 81.Fa "int arg2" 82.Fa "int (*handler) (SYSCTL_HANDLER_ARGS)" 83.Fa "const char *format" 84.Fa "const char *descr" 85.Fc 86.Ft struct sysctl_oid * 87.Fo SYSCTL_ADD_NODE 88.Fa "struct sysctl_ctx_list *ctx" 89.Fa "struct sysctl_oid_list *parent" 90.Fa "int number" 91.Fa "const char *name" 92.Fa "int access" 93.Fa "int (*handler) (SYSCTL_HANDLER_ARGS)" 94.Fa "const char *descr" 95.Fc 96.Ft struct sysctl_oid * 97.Fo SYSCTL_ADD_STRING 98.Fa "struct sysctl_ctx_list *ctx" 99.Fa "struct sysctl_oid_list *parent" 100.Fa "int number" 101.Fa "const char *name" 102.Fa "int access" 103.Fa "char *arg" 104.Fa "int len" 105.Fa "const char *descr" 106.Fc 107.Ft struct sysctl_oid * 108.Fo SYSCTL_ADD_INT 109.Fa "struct sysctl_ctx_list *ctx" 110.Fa "struct sysctl_oid_list *parent" 111.Fa "int number" 112.Fa "const char *name" 113.Fa "int access" 114.Fa "int *arg" 115.Fa "int len" 116.Fa "const char *descr" 117.Fc 118.Ft struct sysctl_oid * 119.Fo SYSCTL_ADD_UINT 120.Fa "struct sysctl_ctx_list *ctx" 121.Fa "struct sysctl_oid_list *parent" 122.Fa "int number" 123.Fa "const char *name" 124.Fa "int access" 125.Fa "unsigned int *arg" 126.Fa "int len" 127.Fa "const char *descr" 128.Fc 129.Ft struct sysctl_oid * 130.Fo SYSCTL_ADD_LONG 131.Fa "struct sysctl_ctx_list *ctx" 132.Fa "struct sysctl_oid_list *parent" 133.Fa "int number" 134.Fa "const char *name" 135.Fa "int access" 136.Fa "long *arg" 137.Fa "const char *descr" 138.Fc 139.Ft struct sysctl_oid * 140.Fo SYSCTL_ADD_ULONG 141.Fa "struct sysctl_ctx_list *ctx" 142.Fa "struct sysctl_oid_list *parent" 143.Fa "int number" 144.Fa "const char *name" 145.Fa "int access" 146.Fa "unsigned long *arg" 147.Fa "const char *descr" 148.Fc 149.Ft struct sysctl_oid * 150.Fo SYSCTL_ADD_QUAD 151.Fa "struct sysctl_ctx_list *ctx" 152.Fa "struct sysctl_oid_list *parent" 153.Fa "int number" 154.Fa "const char *name" 155.Fa "int access" 156.Fa "int64_t *arg" 157.Fa "const char *descr" 158.Fc 159.Ft struct sysctl_oid * 160.Fo SYSCTL_ADD_UQUAD 161.Fa "struct sysctl_ctx_list *ctx" 162.Fa "struct sysctl_oid_list *parent" 163.Fa "int number" 164.Fa "const char *name" 165.Fa "int access" 166.Fa "uint64_t *arg" 167.Fa "const char *descr" 168.Fc 169.Ft struct sysctl_oid * 170.Fo SYSCTL_ADD_OPAQUE 171.Fa "struct sysctl_ctx_list *ctx" 172.Fa "struct sysctl_oid_list *parent" 173.Fa "int number" 174.Fa "const char *name" 175.Fa "int access" 176.Fa "void *arg" 177.Fa "int len" 178.Fa "const char *format" 179.Fa "const char *descr" 180.Fc 181.Ft struct sysctl_oid * 182.Fo SYSCTL_ADD_STRUCT 183.Fa "struct sysctl_ctx_list *ctx" 184.Fa "struct sysctl_oid_list *parent" 185.Fa "int number" 186.Fa "const char *name" 187.Fa "int access" 188.Fa "void *arg" 189.Fa STRUCT_NAME 190.Fa "const char *descr" 191.Fc 192.Ft struct sysctl_oid * 193.Fo SYSCTL_ADD_PROC 194.Fa "struct sysctl_ctx_list *ctx" 195.Fa "struct sysctl_oid_list *parent" 196.Fa "int number" 197.Fa "const char *name" 198.Fa "int access" 199.Fa "void *arg1" 200.Fa "int arg2" 201.Fa "int (*handler) (SYSCTL_HANDLER_ARGS)" 202.Fa "const char *format" 203.Fa "const char *descr" 204.Fc 205.Sh DESCRIPTION 206These functions and macros provide an interface 207for creating and deleting sysctl oids at runtime 208(e.g.\& during lifetime of a module). 209The alternative method, 210based on linker sets (see 211.In sys/linker_set.h 212and 213.\" XXX Manual pages should avoid referencing source files 214.Pa src/sys/kern/kern_sysctl.c 215for details), only allows creation and deletion 216on module load and unload respectively. 217.Pp 218Dynamic oids of type 219.Dv CTLTYPE_NODE 220are reusable 221so that several code sections can create and delete them, 222but in reality they are allocated and freed 223based on their reference count. 224As a consequence, 225it is possible for two or more code sections 226to create partially overlapping trees that they both can use. 227It is not possible to create overlapping leaves, 228nor to create different child types with the same name and parent. 229.Pp 230Newly created oids are connected to their parent nodes. 231In all these functions and macros 232(with the exception of 233.Fn sysctl_remove_oid ) , 234one of the required parameters is 235.Fa parent , 236which points to the head of the parent's list of children. 237.Pp 238Most top level categories are created statically. 239When connecting to existing static oids, 240this pointer can be obtained with the 241.Fn SYSCTL_STATIC_CHILDREN 242macro, where the 243.Fa OID_NAME 244argument is name of the parent oid of type 245.Dv CTLTYPE_NODE 246(i.e., the name displayed by 247.Xr sysctl 8 , 248preceded by underscore, and with all dots replaced with underscores). 249.Pp 250When connecting to an existing dynamic oid, this pointer 251can be obtained with the 252.Fn SYSCTL_CHILDREN 253macro, where the 254.Fa oidp 255argument points to the parent oid of type 256.Dv CTLTYPE_NODE . 257.Pp 258The 259.Fn sysctl_add_oid 260function creates raw oids of any type. 261If the oid is successfully created, 262the function returns a pointer to it; 263otherwise it returns 264.Dv NULL . 265Many of the arguments for 266.Fn sysctl_add_oid 267are common to the macros. 268The arguments are as follows: 269.Bl -tag -width handler 270.It Fa ctx 271A pointer to an optional sysctl context, or 272.Dv NULL . 273See 274.Xr sysctl_ctx_init 9 275for details. 276Programmers are strongly advised to use contexts 277to organize the dynamic oids which they create, 278unless special creation and deletion sequences are required. 279If 280.Fa ctx 281is not 282.Dv NULL , 283the newly created oid will be added to this context 284as its first entry. 285.It Fa parent 286A pointer to a 287.Li struct sysctl_oid_list , 288which is the head of the parent's list of children. 289.It Fa number 290The oid number that will be assigned to this oid. 291In almost all cases this should be set to 292.Dv OID_AUTO , 293which will result in the assignment of the next available oid number. 294.It Fa name 295The name of the oid. 296The newly created oid will contain a copy of the name. 297.It Fa kind 298The kind of oid, 299specified as a bit mask of the type and access values defined in the 300.In sys/sysctl.h 301header file. 302Oids created dynamically always have the 303.Dv CTLFLAG_DYN 304flag set. 305Access flags specify whether this oid is read-only or read-write, 306and whether it may be modified by all users 307or by the superuser only. 308.It Fa arg1 309A pointer to any data that the oid should reference, or 310.Dv NULL . 311.It Fa arg2 312The size of 313.Fa arg1 , 314or 0 if 315.Fa arg1 316is 317.Dv NULL . 318.It Fa handler 319A pointer to the function 320that is responsible for handling read and write requests 321to this oid. 322There are several standard handlers 323that support operations on nodes, 324integers, strings and opaque objects. 325It is possible also to define new handlers using the 326.Fn SYSCTL_ADD_PROC 327macro. 328.It Fa format 329A pointer to a string 330which specifies the format of the oid symbolically. 331This format is used as a hint by 332.Xr sysctl 8 333to apply proper data formatting for display purposes. 334Currently used format names are: 335.Dq N 336for node, 337.Dq A 338for 339.Li "char *" , 340.Dq I 341for 342.Li "int" , 343.Dq IU 344for 345.Li "unsigned int" , 346.Dq L 347for 348.Li "long" , 349.Dq LU 350for 351.Li "unsigned long" 352and 353.Dq S,TYPE 354for 355.Li "struct TYPE" 356structures. 357.It Fa descr 358A pointer to a textual description of the oid. 359.El 360.Pp 361The 362.Fn sysctl_move_oid 363function reparents an existing oid. 364The oid is assigned a new number as if it had been created with 365.Fa number 366set to 367.Dv OID_AUTO . 368.Pp 369The 370.Fn sysctl_remove_oid 371function removes a dynamically created oid from the tree, 372optionally freeing its resources. 373It takes the following arguments: 374.Bl -tag -width recurse 375.It Fa oidp 376A pointer to the dynamic oid to be removed. 377If the oid is not dynamic, or the pointer is 378.Dv NULL , 379the function returns 380.Er EINVAL . 381.It Fa del 382If non-zero, 383.Fn sysctl_remove_oid 384will try to free the oid's resources 385when the reference count of the oid becomes zero. 386However, if 387.Fa del 388is set to 0, 389the routine will only deregister the oid from the tree, 390without freeing its resources. 391This behaviour is useful when the caller expects to rollback 392(possibly partially failed) 393deletion of many oids later. 394.It Fa recurse 395If non-zero, attempt to remove the node and all its children. 396If 397.Pa recurse 398is set to 0, 399any attempt to remove a node that contains any children 400will result in a 401.Er ENOTEMPTY 402error. 403.Em WARNING : "use recursive deletion with extreme caution" ! 404Normally it should not be needed if contexts are used. 405Contexts take care of tracking inter-dependencies 406between users of the tree. 407However, in some extreme cases it might be necessary 408to remove part of the subtree no matter how it was created, 409in order to free some other resources. 410Be aware, though, that this may result in a system 411.Xr panic 9 412if other code sections continue to use removed subtrees. 413.El 414.Pp 415.\" XXX sheldonh finished up to here 416Again, in most cases the programmer should use contexts, 417as described in 418.Xr sysctl_ctx_init 9 , 419to keep track of created oids, 420and to delete them later in orderly fashion. 421.Pp 422There is a set of macros defined 423that helps to create oids of given type. 424They are as follows: 425.Bl -tag -width SYSCTL_ADD_STRINGXX 426.It Fn SYSCTL_ADD_OID 427creates a raw oid. 428This macro is functionally equivalent to the 429.Fn sysctl_add_oid 430function. 431.It Fn SYSCTL_ADD_NODE 432creates an oid of type 433.Dv CTLTYPE_NODE , 434to which child oids may be added. 435.It Fn SYSCTL_ADD_STRING 436creates an oid that handles a zero-terminated character string. 437.It Fn SYSCTL_ADD_INT 438creates an oid that handles an 439.Li int 440variable. 441.It Fn SYSCTL_ADD_UINT 442creates an oid that handles an 443.Li unsigned int 444variable. 445.It Fn SYSCTL_ADD_LONG 446creates an oid that handles a 447.Li long 448variable. 449.It Fn SYSCTL_ADD_ULONG 450creates an oid that handles an 451.Li unsigned long 452variable. 453.It Fn SYSCTL_ADD_QUAD 454creates an oid that handles an 455.Li int64_t 456variable. 457.It Fn SYSCTL_ADD_OPAQUE 458creates an oid that handles any chunk of opaque data 459of the size specified by the 460.Fa len 461argument, 462which is a pointer to a 463.Li "size_t *" . 464.It Fn SYSCTL_ADD_STRUCT 465creates an oid that handles a 466.Li "struct TYPE" 467structure. 468The 469.Fa format 470parameter will be set to 471.Dq S,TYPE 472to provide proper hints to the 473.Xr sysctl 8 474utility. 475.It Fn SYSCTL_ADD_PROC 476creates an oid with the specified 477.Pa handler 478function. 479The handler is responsible for handling read and write requests 480to the oid. 481This oid type is especially useful 482if the kernel data is not easily accessible, 483or needs to be processed before exporting. 484.El 485.Sh EXAMPLES 486The following is an example of 487how to create a new top-level category 488and how to hook up another subtree to an existing static node. 489This example does not use contexts, 490which results in tedious management of all intermediate oids, 491as they need to be freed later on: 492.Bd -literal 493#include <sys/sysctl.h> 494 ... 495/* Need to preserve pointers to newly created subtrees, to be able 496 * to free them later. 497 */ 498struct sysctl_oid *root1, *root2, *oidp; 499int a_int; 500char *string = "dynamic sysctl"; 501 ... 502 503root1 = SYSCTL_ADD_NODE( NULL, SYSCTL_STATIC_CHILDREN(/* tree top */), 504 OID_AUTO, "newtree", CTLFLAG_RW, 0, "new top level tree"); 505oidp = SYSCTL_ADD_INT( NULL, SYSCTL_CHILDREN(root1), 506 OID_AUTO, "newint", CTLFLAG_RW, &a_int, 0, "new int leaf"); 507 ... 508root2 = SYSCTL_ADD_NODE( NULL, SYSCTL_STATIC_CHILDREN(_debug), 509 OID_AUTO, "newtree", CTLFLAG_RW, 0, "new tree under debug"); 510oidp = SYSCTL_ADD_STRING( NULL, SYSCTL_CHILDREN(root2), 511 OID_AUTO, "newstring", CTLFLAG_RD, string, 0, "new string leaf"); 512.Ed 513.Pp 514This example creates the following subtrees: 515.Bd -literal -offset indent 516debug.newtree.newstring 517newtree.newint 518.Ed 519.Pp 520.Em "Care should be taken to free all oids once they are no longer needed!" 521.Sh SEE ALSO 522.Xr sysctl 8 , 523.Xr sysctl 9 , 524.Xr sysctl_ctx_free 9 , 525.Xr sysctl_ctx_init 9 526.Sh HISTORY 527These functions first appeared in 528.Fx 4.2 . 529.Sh AUTHORS 530.An Andrzej Bialecki Aq abial@FreeBSD.org 531.Sh BUGS 532Sharing nodes between many code sections 533causes interdependencies that sometimes may lock the resources. 534For example, 535if module A hooks up a subtree to an oid created by module B, 536module B will be unable to delete that oid. 537These issues are handled properly by sysctl contexts. 538.Pp 539Many operations on the tree involve traversing linked lists. 540For this reason, oid creation and removal is relatively costly. 541