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.
16 .\" 3. All advertising materials mentioning features or use of this software
17 .\" must display the following acknowledgement:
18 .\" This product includes software developed by the NetBSD
19 .\" Foundation, Inc. and its contributors.
20 .\" 4. Neither the name of The NetBSD Foundation nor the names of its
21 .\" contributors may be used to endorse or promote products derived
22 .\" from this software without specific prior written permission.
24 .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
25 .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
26 .\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
27 .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
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29 .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
30 .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
31 .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
32 .\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
33 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
34 .\" POSSIBILITY OF SUCH DAMAGE.
36 .\" $NetBSD: malloc.9,v 1.3 1996/11/11 00:05:11 lukem Exp $
49 .Nd kernel memory management routines
54 .Fn malloc "unsigned long size" "struct malloc_type *type" "int flags"
56 .Fn free "void *addr" "struct malloc_type *type"
58 .Fn realloc "void *addr" "unsigned long size" "struct malloc_type *type" "int flags"
60 .Fn reallocf "void *addr" "unsigned long size" "struct malloc_type *type" "int flags"
61 .Fn MALLOC_DECLARE type
65 .Fn MALLOC_DEFINE type shortdesc longdesc
69 function allocates uninitialized memory in kernel address space for an
70 object whose size is specified by
75 function releases memory at address
77 that was previously allocated by
80 The memory is not zeroed.
91 function changes the size of the previously allocated memory referenced by
96 The contents of the memory are unchanged up to the lesser of the new and
98 Note that the returned value may differ from
100 If the requested memory cannot be allocated,
102 is returned and the memory referenced by
104 is valid and unchanged.
111 function behaves identically to
113 for the specified size.
117 function is identical to
120 will free the passed pointer when the requested memory cannot be allocated.
122 Unlike its standard C library counterpart
124 the kernel version takes two more arguments.
127 argument further qualifies
129 operational characteristics as follows:
130 .Bl -tag -width indent
132 Causes the allocated memory to be set to all zeros.
141 if the request cannot be immediately fulfilled due to resource shortage.
144 is required when running in an interrupt context.
146 Indicates that it is OK to wait for resources.
147 If the request cannot be immediately fulfilled, the current process is put
148 to sleep to wait for resources to be released by other processes.
154 functions cannot return
160 Indicates that the system can dig into its reserve in order to obtain the
162 This option used to be called
164 but has been renamed to something more obvious.
165 This option has been deprecated and is slowly being removed from the kernel,
166 and so should not be used with any new programming.
169 Exactly one of either
177 argument is used to perform statistics on memory usage, and for
179 It can be used to identify multiple allocations.
180 The statistics can be examined by
186 .Vt "struct malloc_type"
192 .Bd -literal -offset indent
193 /* sys/something/foo_extern.h */
195 MALLOC_DECLARE(M_FOOBUF);
197 /* sys/something/foo_main.c */
199 MALLOC_DEFINE(M_FOOBUF, "foobuffers", "Buffers to foo data into the ether");
201 /* sys/something/foo_subr.c */
204 buf = malloc(sizeof *buf, M_FOOBUF, M_NOWAIT);
216 .Sh IMPLEMENTATION NOTES
217 The memory allocator allocates memory in chunks that have size a power
218 of two for requests up to the size of a page of memory.
219 For larger requests, one or more pages is allocated.
220 While it should not be relied upon, this information may be useful for
221 optimizing the efficiency of memory use.
223 Programmers should be careful not to confuse the malloc flags
238 may not be called from fast interrupts handlers.
239 When called from threaded interrupts,
248 may sleep when called with
261 interlock, will cause a LOR (Lock Order Reversal) due to the
262 intertwining of VM Objects and Vnodes.
269 functions return a kernel virtual address that is suitably aligned for
270 storage of any type of object, or
272 if the request could not be satisfied (implying that
276 A kernel compiled with the
278 configuration option attempts to detect memory corruption caused by
279 such things as writing outside the allocated area and imbalanced calls to the
284 Failing consistency checks will cause a panic or a system console