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
28 .\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 $
37 .\" $FreeBSD: src/share/man/man9/malloc.9,v 1.42 2005/02/22 17:20:20 brueffer Exp $
48 .Nd kernel memory management routines
53 .Fn kmalloc "unsigned long size" "struct malloc_type *type" "int flags"
55 .Fn kfree "void *addr" "struct malloc_type *type"
57 .Fn krealloc "void *addr" "unsigned long size" "struct malloc_type *type" "int flags"
58 .Fn MALLOC_DECLARE type
62 .Fn MALLOC_DEFINE type shortdesc longdesc
66 function allocates uninitialized memory in kernel address space for an
67 object whose size is specified by
72 function releases memory at address
74 that was previously allocated by
77 The memory is not zeroed.
78 The kernel implementation of
87 function changes the size of the previously allocated memory referenced by
92 The contents of the memory are unchanged up to the lesser of the new and
94 Note that the returned value may differ from
96 If the requested memory cannot be allocated,
98 is returned and the memory referenced by
100 is valid and unchanged.
107 function behaves identically to
109 for the specified size.
111 Unlike its standard C library counterpart
113 the kernel version takes two more arguments.
116 argument further qualifies
118 operational characteristics as follows:
119 .Bl -tag -width indent
121 Causes the allocated memory to be set to all zeros.
129 if the request cannot be immediately fulfilled due to resource shortage.
132 is required when running in an interrupt context.
134 Indicates that it is OK to wait for resources.
135 If the request cannot be immediately fulfilled, the current process is put
136 to sleep to wait for resources to be released by other processes.
141 functions cannot return
149 to dig into the system's reserved free pages looking for enough room to
150 perform the allocation.
151 This is typically used in interrupts where you cannot afford
155 Indicates that the system can dig into its reserve in order to obtain the
157 This option used to be called
159 but has been renamed to something more obvious.
160 This option has been deprecated and is slowly being removed from the kernel,
161 and so should not be used with any new code.
164 Exactly one of either
172 argument is used to perform statistics on memory usage, and for
174 It can be used to identify multiple allocations.
175 The statistics can be examined by
187 .Bd -literal -offset indent
188 /* sys/something/foo_extern.h */
190 MALLOC_DECLARE(M_FOOBUF);
192 /* sys/something/foo_main.c */
194 MALLOC_DEFINE(M_FOOBUF, "foobuffers", "Buffers to foo data into the ether");
196 /* sys/something/foo_subr.c */
199 buf = kmalloc(sizeof *buf, M_FOOBUF, M_NOWAIT);
202 .Sh IMPLEMENTATION NOTES
203 The memory allocator allocates memory in chunks that have size a power
204 of two for requests up to the size of a page of memory.
205 For larger requests, one or more pages is allocated.
206 While it should not be relied upon, this information may be useful for
207 optimizing the efficiency of memory use.
213 functions return a kernel virtual address that is suitably aligned for
214 storage of any type of object, or
216 if the request could not be satisfied (implying that
220 A kernel compiled with the
222 configuration option attempts to detect memory corruption caused by
223 such things as writing outside the allocated area and imbalanced calls to the
228 Failing consistency checks will cause a panic or a system console