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
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24 .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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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 realloc "void *addr" "size_t size" "struct malloc_type *type" "int flags"
55 .Fn reallocf "void *addr" "size_t size" "struct malloc_type *type" "int flags"
56 .Fn MALLOC_DECLARE type
60 .Fn MALLOC_DEFINE type shortdesc longdesc
64 function allocates uninitialized memory in kernel address space for an
65 object whose size is specified by
70 function allocates uninitialized memory in kernel address space for an
73 entries whose size is specified by
78 function releases memory at address
80 that was previously allocated by
83 The memory is not zeroed.
94 function changes the size of the previously allocated memory referenced by
99 The contents of the memory are unchanged up to the lesser of the new and
101 Note that the returned value may differ from
103 If the requested memory cannot be allocated,
105 is returned and the memory referenced by
107 is valid and unchanged.
114 function behaves identically to
116 for the specified size.
120 function is identical to
123 will free the passed pointer when the requested memory cannot be allocated.
125 Unlike its standard C library counterpart
127 the kernel version takes two more arguments.
130 argument further qualifies
132 operational characteristics as follows:
133 .Bl -tag -width indent
135 Causes the allocated memory to be set to all zeros.
137 For allocations greater than page size, causes the allocated
138 memory to be excluded from kernel core dumps.
147 if the request cannot be immediately fulfilled due to resource shortage.
150 is required when running in an interrupt context.
152 Indicates that it is OK to wait for resources.
153 If the request cannot be immediately fulfilled, the current process is put
154 to sleep to wait for resources to be released by other processes.
161 functions cannot return
166 If the multiplication of
170 would cause an integer overflow, the
172 function induces a panic.
174 Indicates that the system can use its reserve of memory to satisfy the
176 This option should only be used in combination with
178 when an allocation failure cannot be tolerated by the caller without
179 catastrophic effects on the system.
182 Exactly one of either
190 argument is used to perform statistics on memory usage, and for
192 It can be used to identify multiple allocations.
193 The statistics can be examined by
199 .Vt "struct malloc_type"
205 .Bd -literal -offset indent
206 /* sys/something/foo_extern.h */
208 MALLOC_DECLARE(M_FOOBUF);
210 /* sys/something/foo_main.c */
212 MALLOC_DEFINE(M_FOOBUF, "foobuffers", "Buffers to foo data into the ether");
214 /* sys/something/foo_subr.c */
217 buf = malloc(sizeof(*buf), M_FOOBUF, M_NOWAIT);
234 may not be called from fast interrupts handlers.
235 When called from threaded interrupts,
244 may sleep when called with
254 may not be called in a critical section or while holding a spin lock.
264 interlock, will cause a LOR (Lock Order Reversal) due to the
265 intertwining of VM Objects and Vnodes.
266 .Sh IMPLEMENTATION NOTES
267 The memory allocator allocates memory in chunks that have size a power
268 of two for requests up to the size of a page of memory.
269 For larger requests, one or more pages is allocated.
270 While it should not be relied upon, this information may be useful for
271 optimizing the efficiency of memory use.
278 functions return a kernel virtual address that is suitably aligned for
279 storage of any type of object, or
281 if the request could not be satisfied (implying that
285 A kernel compiled with the
287 configuration option attempts to detect memory corruption caused by
288 such things as writing outside the allocated area and imbalanced calls to the
293 Failing consistency checks will cause a panic or a system console