2 .\" Copyright (c) 2000, Andrzej Bialecki <abial@FreeBSD.org>
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28 .\" $FreeBSD: src/share/man/man9/sysctl_add_oid.9,v 1.3.2.10 2001/12/17 11:30:19 ru Exp $
36 .Nd runtime sysctl tree manipulation
39 .Ft struct sysctl_oid *
41 .Fa "struct sysctl_ctx_list *ctx"
42 .Fa "struct sysctl_oid_list *parent"
48 .Fa "int (*handler) (SYSCTL_HANDLER_ARGS)"
54 .Fa "struct sysctl_oid *oidp"
58 .Ft struct sysctl_oid_list *
60 .Fa "struct sysctl_oid *oidp"
62 .Ft struct sysctl_oid_list *
63 .Fo SYSCTL_STATIC_CHILDREN
66 .Ft struct sysctl_oid *
68 .Fa "struct sysctl_ctx_list *ctx"
69 .Fa "struct sysctl_oid_list *parent"
75 .Fa "int (*handler) (SYSCTL_HANDLER_ARGS)"
79 .Ft struct sysctl_oid *
81 .Fa "struct sysctl_ctx_list *ctx"
82 .Fa "struct sysctl_oid_list *parent"
86 .Fa "int (*handler) (SYSCTL_HANDLER_ARGS)"
89 .Ft struct sysctl_oid *
91 .Fa "struct sysctl_ctx_list *ctx"
92 .Fa "struct sysctl_oid_list *parent"
100 .Ft struct sysctl_oid *
102 .Fa "struct sysctl_ctx_list *ctx"
103 .Fa "struct sysctl_oid_list *parent"
111 .Ft struct sysctl_oid *
113 .Fa "struct sysctl_ctx_list *ctx"
114 .Fa "struct sysctl_oid_list *parent"
118 .Fa "unsigned int *arg"
122 .Ft struct sysctl_oid *
124 .Fa "struct sysctl_ctx_list *ctx"
125 .Fa "struct sysctl_oid_list *parent"
133 .Ft struct sysctl_oid *
135 .Fa "struct sysctl_ctx_list *ctx"
136 .Fa "struct sysctl_oid_list *parent"
140 .Fa "unsigned long *arg"
144 .Ft struct sysctl_oid *
145 .Fo SYSCTL_ADD_OPAQUE
146 .Fa "struct sysctl_ctx_list *ctx"
147 .Fa "struct sysctl_oid_list *parent"
155 .Ft struct sysctl_oid *
156 .Fo SYSCTL_ADD_STRUCT
157 .Fa "struct sysctl_ctx_list *ctx"
158 .Fa "struct sysctl_oid_list *parent"
162 .Fa "struct TYPE *arg"
166 .Ft struct sysctl_oid *
168 .Fa "struct sysctl_ctx_list *ctx"
169 .Fa "struct sysctl_oid_list *parent"
175 .Fa "int (*handler) (SYSCTL_HANDLER_ARGS)"
180 These functions and macros provide an interface
181 for creating and deleting sysctl oids at runtime
182 (e.g. during lifetime of a module).
183 The alternative method,
184 based on linker sets (see
187 .\" XXX Manual pages should avoid referencing source files
188 .Pa src/sys/kern/kern_sysctl.c
189 for details), only allows creation and deletion
190 on module load and unload respectively.
195 so that several code sections can create and delete them,
196 but in reality they are allocated and freed
197 based on their reference count.
199 it is possible for two or more code sections
200 to create partially overlapping trees that they both can use.
201 It is not possible to create overlapping leaves,
202 nor to create different child types with the same name and parent.
204 Newly created oids are connected to their parent nodes.
205 In all these functions and macros
206 (with the exception of
207 .Fn sysctl_remove_oid ) ,
208 one of the required parameters is
210 which points to the head of the parent's list of children.
212 Most top level categories are created statically.
213 When connecting to existing static oids,
214 this pointer can be obtained with the
215 .Fn SYSCTL_STATIC_CHILDREN
218 argumwent is name of the parent oid of type
220 (i.e. the name displayed by
222 preceded by underscore, and with all dots replaced with underscores).
224 When connecting to an existing dynamic oid, this pointer
225 can be obtained with the
229 argument points to the parent oid of type
234 function creates raw oids of any type.
235 If the oid is successfuly created,
236 the function returns a pointer to it;
239 Many of the arguments for
241 are common to the macros.
242 The arguments are as follows:
243 .Bl -tag -width handler
245 A pointer to an optional sysctl context, or
248 .Xr sysctl_ctx_init 9
250 Programmers are strongly advised to use contexts
251 to organize the dynamic oids which they create,
252 unless special creation and deletion sequences are required.
257 the newly created oid will be added to this context
261 .Li struct sysctl_oid_list ,
262 which is the head of the parent's list of children.
264 The oid number that will be assigned to this oid.
265 In almost all cases this should be set to
267 which will result in the assignment of the next available oid number.
270 The newly created oid will contain a copy of the name.
273 specified as a bitmask of the type and access values defined in the
276 Oids created dynamically always have the
279 Access flags specify whether this oid is read-only or read-write,
280 and whether it may be modified by all users
281 or by the supseruser only.
283 A pointer to any data that the oid should reference, or
293 A pointer to the function
294 that is responsible for handling read and write requests
296 There are several standard handlers
297 that support operations on nodes,
298 integers, strings and opaque objects.
299 It is possible also to define new handlers using the
303 A pointer to a string
304 which specifies the format of the oid symbolically.
305 This format is used as a hint by
307 to apply proper data formatting for display purposes.
308 Currently used format names are:
332 A pointer to a textual description of the oid.
336 .Fn sysctl_remove_oid
337 function removes a dynamically created oid from the tree,
338 optionally freeing its resources.
339 It takes the following arguments:
340 .Bl -tag -width recurse
342 A pointer to the dynamic oid to be removed.
343 If the oid is not dynamic, or the pointer is
349 .Fn sysctl_remove_oid
350 will try to free the oid's resources
351 when the reference count of the oid becomes zero.
355 the routine will only deregister the oid from the tree,
356 without freeing its resources.
357 This behaviour is useful when the caller expects to rollback
358 (possibly partially failed)
359 deletion of many oids later.
361 If non-zero, attempt to remove the node and all its children.
365 any attempt to remove a node that contains any children
369 .Em WARNING : "use recursive deletion with extreme caution" !
370 Normally it should not be needed if contexts are used.
371 Contexts take care of tracking inter-dependencies
372 between users of the tree.
373 However, in some extreme cases it might be necessary
374 to remove part of the subtree no matter how it was created,
375 in order to free some other resources.
376 Be aware, though, that this may result in a system
378 if other code sections continue to use removed subtrees.
381 .\" XXX sheldonh finished up to here
382 Again, in most cases the programmer should use contexts,
384 .Xr sysctl_ctx_init 9 ,
385 to keep track of created oids,
386 and to delete them later in orderly fashion.
388 There is a set of macros defined
389 that helps to create oids of given type.
390 .Bl -tag -width SYSCTL_ADD_STRINGXX
392 .It Fn SYSCTL_ADD_OID
394 This macro is functionally equivalent to the
397 .It Fn SYSCTL_ADD_NODE
398 creates an oid of type
400 to which child oids may be added.
401 .It Fn SYSCTL_ADD_STRING
402 creates an oid that handles a zero-terminated character string.
403 .It Fn SYSCTL_ADD_INT
404 creates an oid that handles an
407 .It Fn SYSCTL_ADD_UINT
408 creates an oid that handles an
411 .It Fn SYSCTL_ADD_LONG
412 creates an oid that handles a
415 .It Fn SYSCTL_ADD_ULONG
416 creates an oid that handles an
419 .It Fn SYSCTL_ADD_OPAQUE
420 creates an oid that handles any chunk of opaque data
421 of the size specified by the
424 which is a pointer to a
426 .It Fn SYSCTL_ADD_STRUCT
427 creates an oid that handles a
432 parameter will be set to
434 to provide proper hints to the
437 .It Fn SYSCTL_ADD_PROC
438 creates an oid with the specified
441 The handler is responsible for handling read and write requests
443 This oid type is especially useful
444 if the kernel data is not easily accessible,
445 or needs to be processed before exporting.
448 The following is an example of
449 how to create a new top-level category
450 and how to hook up another subtree to an existing static node.
451 This example does not use contexts,
452 which results in tedious management of all intermediate oids,
453 as they need to be freed later on:
455 #include <sys/sysctl.h>
457 /* Need to preserve pointers to newly created subtrees, to be able
458 * to free them later.
460 struct sysctl_oid *root1, *root2, *oidp;
462 char *string = "dynamic sysctl";
465 root1 = SYSCTL_ADD_NODE( NULL, SYSCTL_STATIC_CHILDREN(/* tree top */),
466 OID_AUTO, newtree, CTFLAG_RW, 0, "new top level tree");
467 oidp = SYSCTL_ADD_INT( NULL, SYSCTL_CHILDREN(root1),
468 OID_AUTO, newint, CTLFLAG_RW, &a_int, 0, "new int leaf");
470 root2 = SYSCTL_ADD_NODE( NULL, SYSCTL_STATIC_CHILDREN(_debug),
471 OID_AUTO, newtree, CTFLAG_RW, 0, "new tree under debug");
472 oidp = SYSCTL_ADD_STRING( NULL, SYSCTL_CHILDREN(root2),
473 OID_AUTO, newstring, CTLFLAG_R, string, 0, "new string leaf");
476 This example creates the following subtrees:
477 .Bd -literal -offset indent
478 debug.newtree.newstring
482 .Em "Care should be taken to free all oids once they are no longer needed!"
485 .Xr sysctl_ctx_free 9 ,
486 .Xr sysctl_ctx_init 9
488 These functions first appeared in
491 .An Andrzej Bialecki Aq abial@FreeBSD.org
493 Sharing nodes between many code sections
494 causes interdependencies that sometimes may lock the resources.
496 if module A hooks up a subtree to an oid created by module B,
497 module B will be unable to delete that oid.
498 These issues are handled properly by sysctl contexts.
500 Many operations on the tree involve traversing linked lists.
501 For this reason, oid creation and removal is relatively costly.