2 .\" Copyright (c) 1996 The NetBSD Foundation, Inc.
3 .\" All rights reserved.
5 .\" This code is derived from software contributed to The NetBSD Foundation
6 .\" by Paul Kranenburg.
8 .\" Redistribution and use in source and binary forms, with or without
9 .\" modification, are permitted provided that the following conditions
11 .\" 1. Redistributions of source code must retain the above copyright
12 .\" notice, this list of conditions and the following disclaimer.
13 .\" 2. Redistributions in binary form must reproduce the above copyright
14 .\" notice, this list of conditions and the following disclaimer in the
15 .\" documentation and/or other materials provided with the distribution.
17 .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
18 .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
19 .\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
20 .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
21 .\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
22 .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
23 .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
24 .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
25 .\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
26 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
27 .\" POSSIBILITY OF SUCH DAMAGE.
29 .\" $NetBSD: malloc.9,v 1.3 1996/11/11 00:05:11 lukem Exp $
42 .Nd kernel memory management routines
47 .Fn malloc "size_t size" "struct malloc_type *type" "int flags"
49 .Fn mallocarray "size_t nmemb" "size_t size" "struct malloc_type *type" "int flags"
51 .Fn free "void *addr" "struct malloc_type *type"
53 .Fn zfree "void *addr" "struct malloc_type *type"
55 .Fn realloc "void *addr" "size_t size" "struct malloc_type *type" "int flags"
57 .Fn reallocf "void *addr" "size_t size" "struct malloc_type *type" "int flags"
58 .Fn MALLOC_DECLARE type
62 .Fn MALLOC_DEFINE type shortdesc longdesc
66 .Fn malloc_domainset "size_t size" "struct malloc_type *type" "struct domainset *ds" "int flags"
68 .Fn free_domain "void *addr" "struct malloc_type *type"
72 function allocates uninitialized memory in kernel address space for an
73 object whose size is specified by
78 variant allocates memory from a specific
80 domain using the specified domain selection policy.
83 for some example policies.
84 Memory allocated with this function should be returned with
89 function allocates uninitialized memory in kernel address space for an
92 entries whose size is specified by
97 function releases memory at address
99 that was previously allocated by
102 The memory is not zeroed.
115 function releases memory at address
117 that was previously allocated by
122 will zero the memory before it is released.
126 function changes the size of the previously allocated memory referenced by
131 The contents of the memory are unchanged up to the lesser of the new and
133 Note that the returned value may differ from
135 If the requested memory cannot be allocated,
137 is returned and the memory referenced by
139 is valid and unchanged.
146 function behaves identically to
148 for the specified size.
152 function is identical to
155 will free the passed pointer when the requested memory cannot be allocated.
157 Unlike its standard C library counterpart
159 the kernel version takes two more arguments.
162 argument further qualifies
164 operational characteristics as follows:
165 .Bl -tag -width indent
167 Causes the allocated memory to be set to all zeros.
169 For allocations greater than page size, causes the allocated
170 memory to be excluded from kernel core dumps.
179 if the request cannot be immediately fulfilled due to resource shortage.
182 is required when running in an interrupt context.
184 Indicates that it is OK to wait for resources.
185 If the request cannot be immediately fulfilled, the current process is put
186 to sleep to wait for resources to be released by other processes.
193 functions cannot return
198 If the multiplication of
202 would cause an integer overflow, the
204 function induces a panic.
206 Indicates that the system can use its reserve of memory to satisfy the
208 This option should only be used in combination with
210 when an allocation failure cannot be tolerated by the caller without
211 catastrophic effects on the system.
213 Indicates that the system should allocate executable memory.
214 If this flag is not set, the system will not allocate executable memory.
215 Not all platforms enforce a distinction between executable and
216 non-executable memory.
219 Exactly one of either
227 argument is used to perform statistics on memory usage, and for
229 It can be used to identify multiple allocations.
230 The statistics can be examined by
236 .Vt "struct malloc_type"
242 .Bd -literal -offset indent
243 /* sys/something/foo_extern.h */
245 MALLOC_DECLARE(M_FOOBUF);
247 /* sys/something/foo_main.c */
249 MALLOC_DEFINE(M_FOOBUF, "foobuffers", "Buffers to foo data into the ether");
251 /* sys/something/foo_subr.c */
254 buf = malloc(sizeof(*buf), M_FOOBUF, M_NOWAIT);
271 may not be called from fast interrupts handlers.
272 When called from threaded interrupts,
281 may sleep when called with
291 may not be called in a critical section or while holding a spin lock.
301 interlock, will cause a LOR (Lock Order Reversal) due to the
302 intertwining of VM Objects and Vnodes.
303 .Sh IMPLEMENTATION NOTES
304 The memory allocator allocates memory in chunks that have size a power
305 of two for requests up to the size of a page of memory.
306 For larger requests, one or more pages is allocated.
307 While it should not be relied upon, this information may be useful for
308 optimizing the efficiency of memory use.
315 functions return a kernel virtual address that is suitably aligned for
316 storage of any type of object, or
318 if the request could not be satisfied (implying that
322 A kernel compiled with the
324 configuration option attempts to detect memory corruption caused by
325 such things as writing outside the allocated area and imbalanced calls to the
330 Failing consistency checks will cause a panic or a system console