2 .\" Copyright (c) 2000, Andrzej Bialecki <abial@FreeBSD.org>
3 .\" All rights reserved.
5 .\" Redistribution and use in source and binary forms, with or without
6 .\" modification, are permitted provided that the following conditions
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
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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.
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
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28 .\" $FreeBSD: src/share/man/man9/sysctl_add_oid.9,v 1.21 2006/04/28 10:45:27 rwatson Exp $
35 .Nm sysctl_remove_oid ,
37 .Nm SYSCTL_STATIC_CHILDREN ,
40 .Nm SYSCTL_ADD_STRING ,
45 .Nm SYSCTL_ADD_ULONG ,
47 .Nm SYSCTL_ADD_UQUAD ,
48 .Nm SYSCTL_ADD_OPAQUE ,
49 .Nm SYSCTL_ADD_STRUCT ,
51 .Nd runtime sysctl tree manipulation
54 .Ft struct sysctl_oid *
56 .Fa "struct sysctl_ctx_list *ctx"
57 .Fa "struct sysctl_oid_list *parent"
59 .Fa "const char *name"
63 .Fa "int (*handler) (SYSCTL_HANDLER_ARGS)"
64 .Fa "const char *format"
65 .Fa "const char *descr"
69 .Fa "struct sysctl_oid *oidp"
73 .Ft struct sysctl_oid_list *
75 .Fa "struct sysctl_oid *oidp"
77 .Ft struct sysctl_oid_list *
78 .Fo SYSCTL_STATIC_CHILDREN
79 .Fa "struct sysctl_oid_list oid_name"
81 .Ft struct sysctl_oid *
83 .Fa "struct sysctl_ctx_list *ctx"
84 .Fa "struct sysctl_oid_list *parent"
86 .Fa "const char *name"
90 .Fa "int (*handler) (SYSCTL_HANDLER_ARGS)"
91 .Fa "const char *format"
92 .Fa "const char *descr"
94 .Ft struct sysctl_oid *
96 .Fa "struct sysctl_ctx_list *ctx"
97 .Fa "struct sysctl_oid_list *parent"
99 .Fa "const char *name"
101 .Fa "int (*handler) (SYSCTL_HANDLER_ARGS)"
102 .Fa "const char *descr"
104 .Ft struct sysctl_oid *
105 .Fo SYSCTL_ADD_STRING
106 .Fa "struct sysctl_ctx_list *ctx"
107 .Fa "struct sysctl_oid_list *parent"
109 .Fa "const char *name"
113 .Fa "const char *descr"
115 .Ft struct sysctl_oid *
117 .Fa "struct sysctl_ctx_list *ctx"
118 .Fa "struct sysctl_oid_list *parent"
120 .Fa "const char *name"
124 .Fa "const char *descr"
126 .Ft struct sysctl_oid *
128 .Fa "struct sysctl_ctx_list *ctx"
129 .Fa "struct sysctl_oid_list *parent"
131 .Fa "const char *name"
134 .Fa "const char *descr"
136 .Ft struct sysctl_oid *
138 .Fa "struct sysctl_ctx_list *ctx"
139 .Fa "struct sysctl_oid_list *parent"
141 .Fa "const char *name"
143 .Fa "unsigned int *arg"
145 .Fa "const char *descr"
147 .Ft struct sysctl_oid *
149 .Fa "struct sysctl_ctx_list *ctx"
150 .Fa "struct sysctl_oid_list *parent"
152 .Fa "const char *name"
155 .Fa "const char *descr"
157 .Ft struct sysctl_oid *
159 .Fa "struct sysctl_ctx_list *ctx"
160 .Fa "struct sysctl_oid_list *parent"
162 .Fa "const char *name"
164 .Fa "unsigned long *arg"
165 .Fa "const char *descr"
167 .Ft struct sysctl_oid *
169 .Fa "struct sysctl_ctx_list *ctx"
170 .Fa "struct sysctl_oid_list *parent"
172 .Fa "const char *name"
176 .Fa "const char *descr"
178 .Ft struct sysctl_oid *
180 .Fa "struct sysctl_ctx_list *ctx"
181 .Fa "struct sysctl_oid_list *parent"
183 .Fa "const char *name"
187 .Fa "const char *descr"
189 .Ft struct sysctl_oid *
190 .Fo SYSCTL_ADD_OPAQUE
191 .Fa "struct sysctl_ctx_list *ctx"
192 .Fa "struct sysctl_oid_list *parent"
194 .Fa "const char *name"
198 .Fa "const char *format"
199 .Fa "const char *descr"
201 .Ft struct sysctl_oid *
202 .Fo SYSCTL_ADD_STRUCT
203 .Fa "struct sysctl_ctx_list *ctx"
204 .Fa "struct sysctl_oid_list *parent"
206 .Fa "const char *name"
210 .Fa "const char *descr"
212 .Ft struct sysctl_oid *
214 .Fa "struct sysctl_ctx_list *ctx"
215 .Fa "struct sysctl_oid_list *parent"
217 .Fa "const char *name"
221 .Fa "int (*handler) (SYSCTL_HANDLER_ARGS)"
222 .Fa "const char *format"
223 .Fa "const char *descr"
226 These functions and macros provide an interface
227 for creating and deleting sysctl oids at runtime
228 (e.g.\& during lifetime of a module).
229 The alternative method,
230 based on linker sets (see
233 .\" XXX Manual pages should avoid referencing source files
234 .Pa /sys/kern/kern_sysctl.c
235 for details), only allows creation and deletion
236 on module load and unload respectively.
241 so that several code sections can create and delete them,
242 but in reality they are allocated and freed
243 based on their reference count.
245 it is possible for two or more code sections
246 to create partially overlapping trees that they both can use.
247 It is not possible to create overlapping leaves,
248 nor to create different child types with the same name and parent.
250 Newly created oids are connected to their parent nodes.
251 In all these functions and macros
252 (with the exception of
253 .Fn sysctl_remove_oid ) ,
254 one of the required parameters is
256 which points to the head of the parent's list of children.
258 Most top level categories are created statically.
259 When connecting to existing static oids,
260 this pointer can be obtained with the
261 .Fn SYSCTL_STATIC_CHILDREN
264 argument is name of the parent oid of type
266 (i.e., the name displayed by
268 preceded by underscore, and with all dots replaced with underscores).
270 When connecting to an existing dynamic oid, this pointer
271 can be obtained with the
275 argument points to the parent oid of type
280 function creates raw oids of any type.
281 If the oid is successfully created,
282 the function returns a pointer to it;
285 Many of the arguments for
287 are common to the macros.
288 The arguments are as follows:
289 .Bl -tag -width handler
291 A pointer to an optional sysctl context, or
294 .Xr sysctl_ctx_init 9
296 Programmers are strongly advised to use contexts
297 to organize the dynamic oids which they create,
298 unless special creation and deletion sequences are required.
303 the newly created oid will be added to this context
307 .Li struct sysctl_oid_list ,
308 which is the head of the parent's list of children.
310 The oid number that will be assigned to this oid.
311 In almost all cases this should be set to
313 which will result in the assignment of the next available oid number.
316 The newly created oid will contain a copy of the name.
319 specified as a bit mask of the type and access values defined in the
322 Oids created dynamically always have the
325 Access flags specify whether this oid is read-only or read-write,
326 and whether it may be modified by all users
327 or by the superuser only.
329 A pointer to any data that the oid should reference, or
339 A pointer to the function
340 that is responsible for handling read and write requests
342 There are several standard handlers
343 that support operations on nodes,
344 integers, strings and opaque objects.
345 It is possible also to define new handlers using the
349 A pointer to a string
350 which specifies the format of the oid symbolically.
351 This format is used as a hint by
353 to apply proper data formatting for display purposes.
354 Currently used format names are:
367 for temperature in tenths of kelvins,
380 A pointer to a textual description of the oid.
384 .Fn sysctl_remove_oid
385 function removes a dynamically created oid from the tree,
386 optionally freeing its resources.
387 It takes the following arguments:
388 .Bl -tag -width recurse
390 A pointer to the dynamic oid to be removed.
391 If the oid is not dynamic, or the pointer is
397 .Fn sysctl_remove_oid
398 will try to free the oid's resources
399 when the reference count of the oid becomes zero.
403 the routine will only deregister the oid from the tree,
404 without freeing its resources.
405 This behaviour is useful when the caller expects to rollback
406 (possibly partially failed)
407 deletion of many oids later.
409 If non-zero, attempt to remove the node and all its children.
413 any attempt to remove a node that contains any children
417 .Em WARNING : "use recursive deletion with extreme caution" !
418 Normally it should not be needed if contexts are used.
419 Contexts take care of tracking inter-dependencies
420 between users of the tree.
421 However, in some extreme cases it might be necessary
422 to remove part of the subtree no matter how it was created,
423 in order to free some other resources.
424 Be aware, though, that this may result in a system
426 if other code sections continue to use removed subtrees.
429 .\" XXX sheldonh finished up to here
430 Again, in most cases the programmer should use contexts,
432 .Xr sysctl_ctx_init 9 ,
433 to keep track of created oids,
434 and to delete them later in orderly fashion.
436 There is a set of macros defined
437 that helps to create oids of given type.
440 .Bl -tag -width SYSCTL_ADD_STRINGXX
441 .It Fn SYSCTL_ADD_OID
443 This macro is functionally equivalent to the
446 .It Fn SYSCTL_ADD_NODE
447 creates an oid of type
449 to which child oids may be added.
450 .It Fn SYSCTL_ADD_STRING
451 creates an oid that handles a zero-terminated character string.
452 .It Fn SYSCTL_ADD_INT
453 creates an oid that handles an
456 .It Fn SYSCTL_ADD_U32
457 creates an oid that handles a
460 .It Fn SYSCTL_ADD_UINT
461 creates an oid that handles an
464 .It Fn SYSCTL_ADD_LONG
465 creates an oid that handles a
468 .It Fn SYSCTL_ADD_ULONG
469 creates an oid that handles an
472 .It Fn SYSCTL_ADD_QUAD
473 creates an oid that handles a 64-bit
476 .It Fn SYSCTL_ADD_UQUAD
477 creates an oid that handles a 64-bit
480 .It Fn SYSCTL_ADD_OPAQUE
481 creates an oid that handles any chunk of opaque data
482 of the size specified by the
485 which is a pointer to a
487 .It Fn SYSCTL_ADD_STRUCT
488 creates an oid that handles a
493 parameter will be set to
495 to provide proper hints to the
498 .It Fn SYSCTL_ADD_PROC
499 creates an oid with the specified
502 The handler is responsible for handling read and write requests
504 This oid type is especially useful
505 if the kernel data is not easily accessible,
506 or needs to be processed before exporting.
509 The following is an example of
510 how to create a new top-level category
511 and how to hook up another subtree to an existing static node.
512 This example does not use contexts,
513 which results in tedious management of all intermediate oids,
514 as they need to be freed later on:
516 #include <sys/sysctl.h>
518 /* Need to preserve pointers to newly created subtrees, to be able
519 * to free them later.
521 struct sysctl_oid *root1, *root2, *oidp;
523 char *string = "dynamic sysctl";
526 root1 = SYSCTL_ADD_NODE( NULL, SYSCTL_STATIC_CHILDREN(/* tree top */),
527 OID_AUTO, "newtree", CTLFLAG_RW, 0, "new top level tree");
528 oidp = SYSCTL_ADD_INT( NULL, SYSCTL_CHILDREN(root1),
529 OID_AUTO, "newint", CTLFLAG_RW, &a_int, 0, "new int leaf");
531 root2 = SYSCTL_ADD_NODE( NULL, SYSCTL_STATIC_CHILDREN(_debug),
532 OID_AUTO, "newtree", CTLFLAG_RW, 0, "new tree under debug");
533 oidp = SYSCTL_ADD_STRING( NULL, SYSCTL_CHILDREN(root2),
534 OID_AUTO, "newstring", CTLFLAG_RD, string, 0, "new string leaf");
537 This example creates the following subtrees:
538 .Bd -literal -offset indent
539 debug.newtree.newstring
543 .Em "Care should be taken to free all oids once they are no longer needed!"
547 .Xr sysctl_ctx_free 9 ,
548 .Xr sysctl_ctx_init 9
550 These functions first appeared in
553 .An Andrzej Bialecki Aq Mt abial@FreeBSD.org
555 Sharing nodes between many code sections
556 causes interdependencies that sometimes may lock the resources.
558 if module A hooks up a subtree to an oid created by module B,
559 module B will be unable to delete that oid.
560 These issues are handled properly by sysctl contexts.
562 Many operations on the tree involve traversing linked lists.
563 For this reason, oid creation and removal is relatively costly.