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 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"
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.
85 function allocates uninitialized memory in kernel address space for an
88 entries whose size is specified by
93 function releases memory at address
95 that was previously allocated by
98 The memory is not zeroed.
111 function releases memory at address
113 that was previously allocated by
118 will zero the memory before it is released.
122 function changes the size of the previously allocated memory referenced by
127 The contents of the memory are unchanged up to the lesser of the new and
129 Note that the returned value may differ from
131 If the requested memory cannot be allocated,
133 is returned and the memory referenced by
135 is valid and unchanged.
142 function behaves identically to
144 for the specified size.
148 function is identical to
151 will free the passed pointer when the requested memory cannot be allocated.
153 Unlike its standard C library counterpart
155 the kernel version takes two more arguments.
158 argument further qualifies
160 operational characteristics as follows:
161 .Bl -tag -width indent
163 Causes the allocated memory to be set to all zeros.
165 For allocations greater than page size, causes the allocated
166 memory to be excluded from kernel core dumps.
175 if the request cannot be immediately fulfilled due to resource shortage.
178 is required when running in an interrupt context.
180 Indicates that it is OK to wait for resources.
181 If the request cannot be immediately fulfilled, the current process is put
182 to sleep to wait for resources to be released by other processes.
189 functions cannot return
194 If the multiplication of
198 would cause an integer overflow, the
200 function induces a panic.
202 Indicates that the system can use its reserve of memory to satisfy the
204 This option should only be used in combination with
206 when an allocation failure cannot be tolerated by the caller without
207 catastrophic effects on the system.
209 Indicates that the system should allocate executable memory.
210 If this flag is not set, the system will not allocate executable memory.
211 Not all platforms enforce a distinction between executable and
212 non-executable memory.
215 Exactly one of either
223 argument is used to perform statistics on memory usage, and for
225 It can be used to identify multiple allocations.
226 The statistics can be examined by
232 .Vt "struct malloc_type"
238 .Bd -literal -offset indent
239 /* sys/something/foo_extern.h */
241 MALLOC_DECLARE(M_FOOBUF);
243 /* sys/something/foo_main.c */
245 MALLOC_DEFINE(M_FOOBUF, "foobuffers", "Buffers to foo data into the ether");
247 /* sys/something/foo_subr.c */
250 buf = malloc(sizeof(*buf), M_FOOBUF, M_NOWAIT);
267 may not be called from fast interrupts handlers.
268 When called from threaded interrupts,
277 may sleep when called with
287 may not be called in a critical section or while holding a spin lock.
297 interlock, will cause a LOR (Lock Order Reversal) due to the
298 intertwining of VM Objects and Vnodes.
299 .Sh IMPLEMENTATION NOTES
300 The memory allocator allocates memory in chunks that have size a power
301 of two for requests up to the size of a page of memory.
302 For larger requests, one or more pages is allocated.
303 While it should not be relied upon, this information may be useful for
304 optimizing the efficiency of memory use.
311 functions return a kernel virtual address that is suitably aligned for
312 storage of any type of object, or
314 if the request could not be satisfied (implying that
318 A kernel compiled with the
320 configuration option attempts to detect memory corruption caused by
321 such things as writing outside the allocated area and imbalanced calls to the
326 Failing consistency checks will cause a panic or a system console