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
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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
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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 .Fn malloc_domainset "size_t size" "struct malloc_type *type" "struct domainset *ds" "int flags"
66 .Fn free_domain "void *addr" "struct malloc_type *type"
70 function allocates uninitialized memory in kernel address space for an
71 object whose size is specified by
76 variant allocates memory from a specific
78 domain using the specified domain selection policy.
81 for some example policies.
82 Memory allocated with this function should be returned with
87 function allocates uninitialized memory in kernel address space for an
90 entries whose size is specified by
95 function releases memory at address
97 that was previously allocated by
100 The memory is not zeroed.
111 function changes the size of the previously allocated memory referenced by
116 The contents of the memory are unchanged up to the lesser of the new and
118 Note that the returned value may differ from
120 If the requested memory cannot be allocated,
122 is returned and the memory referenced by
124 is valid and unchanged.
131 function behaves identically to
133 for the specified size.
137 function is identical to
140 will free the passed pointer when the requested memory cannot be allocated.
142 Unlike its standard C library counterpart
144 the kernel version takes two more arguments.
147 argument further qualifies
149 operational characteristics as follows:
150 .Bl -tag -width indent
152 Causes the allocated memory to be set to all zeros.
154 For allocations greater than page size, causes the allocated
155 memory to be excluded from kernel core dumps.
164 if the request cannot be immediately fulfilled due to resource shortage.
167 is required when running in an interrupt context.
169 Indicates that it is OK to wait for resources.
170 If the request cannot be immediately fulfilled, the current process is put
171 to sleep to wait for resources to be released by other processes.
178 functions cannot return
183 If the multiplication of
187 would cause an integer overflow, the
189 function induces a panic.
191 Indicates that the system can use its reserve of memory to satisfy the
193 This option should only be used in combination with
195 when an allocation failure cannot be tolerated by the caller without
196 catastrophic effects on the system.
198 Indicates that the system should allocate executable memory.
199 If this flag is not set, the system will not allocate executable memory.
200 Not all platforms enforce a distinction between executable and
201 non-executable memory.
204 Exactly one of either
212 argument is used to perform statistics on memory usage, and for
214 It can be used to identify multiple allocations.
215 The statistics can be examined by
221 .Vt "struct malloc_type"
227 .Bd -literal -offset indent
228 /* sys/something/foo_extern.h */
230 MALLOC_DECLARE(M_FOOBUF);
232 /* sys/something/foo_main.c */
234 MALLOC_DEFINE(M_FOOBUF, "foobuffers", "Buffers to foo data into the ether");
236 /* sys/something/foo_subr.c */
239 buf = malloc(sizeof(*buf), M_FOOBUF, M_NOWAIT);
256 may not be called from fast interrupts handlers.
257 When called from threaded interrupts,
266 may sleep when called with
276 may not be called in a critical section or while holding a spin lock.
286 interlock, will cause a LOR (Lock Order Reversal) due to the
287 intertwining of VM Objects and Vnodes.
288 .Sh IMPLEMENTATION NOTES
289 The memory allocator allocates memory in chunks that have size a power
290 of two for requests up to the size of a page of memory.
291 For larger requests, one or more pages is allocated.
292 While it should not be relied upon, this information may be useful for
293 optimizing the efficiency of memory use.
300 functions return a kernel virtual address that is suitably aligned for
301 storage of any type of object, or
303 if the request could not be satisfied (implying that
307 A kernel compiled with the
309 configuration option attempts to detect memory corruption caused by
310 such things as writing outside the allocated area and imbalanced calls to the
315 Failing consistency checks will cause a panic or a system console