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.
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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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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"
59 .Fn malloc_usable_size "const void *addr"
61 .Fn malloc_exec "size_t size" "struct malloc_type *type" "int flags"
62 .Fn MALLOC_DECLARE type
66 .Fn MALLOC_DEFINE type shortdesc longdesc
70 .Fn malloc_domainset "size_t size" "struct malloc_type *type" "struct domainset *ds" "int flags"
72 .Fn malloc_domainset_exec "size_t size" "struct malloc_type *type" "struct domainset *ds" "int flags"
76 function allocates uninitialized memory in kernel address space for an
77 object whose size is specified by
82 variant allocates memory from a specific
84 domain using the specified domain selection policy.
87 for some example policies.
92 .Fn malloc_domainset_exec
93 can be used to return executable memory.
94 Not all platforms enforce a distinction between executable and non-executable memory.
98 function allocates uninitialized memory in kernel address space for an
101 entries whose size is specified by
106 function releases memory at address
108 that was previously allocated by
111 The memory is not zeroed.
124 function releases memory at address
126 that was previously allocated by
131 will zero the memory before it is released.
135 function changes the size of the previously allocated memory referenced by
140 The contents of the memory are unchanged up to the lesser of the new and
142 Note that the returned value may differ from
144 If the requested memory cannot be allocated,
146 is returned and the memory referenced by
148 is valid and unchanged.
155 function behaves identically to
157 for the specified size.
161 function is identical to
164 will free the passed pointer when the requested memory cannot be allocated.
167 .Fn malloc_usable_size
168 function returns the usable size of the allocation pointed to by
170 The return value may be larger than the size that was requested during
173 Unlike its standard C library counterpart
175 the kernel version takes two more arguments.
178 argument further qualifies
180 operational characteristics as follows:
181 .Bl -tag -width indent
183 Causes the allocated memory to be set to all zeros.
185 For allocations greater than page size, causes the allocated
186 memory to be excluded from kernel core dumps.
195 if the request cannot be immediately fulfilled due to resource shortage.
198 is required when running in an interrupt context.
200 Indicates that it is OK to wait for resources.
201 If the request cannot be immediately fulfilled, the current process is put
202 to sleep to wait for resources to be released by other processes.
209 functions cannot return
214 If the multiplication of
218 would cause an integer overflow, the
220 function induces a panic.
222 Indicates that the system can use its reserve of memory to satisfy the
224 This option should only be used in combination with
226 when an allocation failure cannot be tolerated by the caller without
227 catastrophic effects on the system.
230 Exactly one of either
238 argument is used to perform statistics on memory usage, and for
240 It can be used to identify multiple allocations.
241 The statistics can be examined by
247 .Vt "struct malloc_type"
253 .Bd -literal -offset indent
254 /* sys/something/foo_extern.h */
256 MALLOC_DECLARE(M_FOOBUF);
258 /* sys/something/foo_main.c */
260 MALLOC_DEFINE(M_FOOBUF, "foobuffers", "Buffers to foo data into the ether");
262 /* sys/something/foo_subr.c */
265 buf = malloc(sizeof(*buf), M_FOOBUF, M_NOWAIT);
282 may not be called from fast interrupts handlers.
283 When called from threaded interrupts,
292 may sleep when called with
302 may not be called in a critical section or while holding a spin lock.
312 interlock, will cause a LOR (Lock Order Reversal) due to the
313 intertwining of VM Objects and Vnodes.
314 .Sh IMPLEMENTATION NOTES
315 The memory allocator allocates memory in chunks that have size a power
316 of two for requests up to the size of a page of memory.
317 For larger requests, one or more pages is allocated.
318 While it should not be relied upon, this information may be useful for
319 optimizing the efficiency of memory use.
326 functions return a kernel virtual address that is suitably aligned for
327 storage of any type of object, or
329 if the request could not be satisfied (implying that
333 A kernel compiled with the
335 configuration option attempts to detect memory corruption caused by
336 such things as writing outside the allocated area and imbalanced calls to the
341 Failing consistency checks will cause a panic or a system console