1.\" $NetBSD: malloc.9,v 1.3 1996/11/11 00:05:11 lukem Exp $ 2.\" 3.\" Copyright (c) 1996 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Paul Kranenburg. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. All advertising materials mentioning features or use of this software 18.\" must display the following acknowledgement: 19.\" This product includes software developed by the NetBSD 20.\" Foundation, Inc. and its contributors. 21.\" 4. Neither the name of The NetBSD Foundation nor the names of its 22.\" contributors may be used to endorse or promote products derived 23.\" from this software without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 26.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 27.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 28.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE 29.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 30.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 31.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 32.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 33.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 34.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 35.\" POSSIBILITY OF SUCH DAMAGE. 36.\" 37.Dd June 16, 1996 38.Dt MALLOC 9 39.Os FreeBSD 40.Sh NAME 41.Nm malloc , 42.Nm MALLOC , 43.Nm free , 44.Nm FREE 45.Nd kernel memory management routines 46.Sh SYNOPSIS 47.Fd #include <sys/types.h> 48.Fd #include <sys/malloc.h> 49.Ft void * 50.Fn malloc "unsigned long size" "struct malloc_type *type" "int flags" 51.Fn MALLOC "space" "cast" "unsigned long size" "struct malloc_type *type" "int flags" 52.Ft void 53.Fn free "void *addr" "struct malloc_type *type" 54.Fn FREE "void *addr" "struct malloc_type *type" 55.Sh DESCRIPTION 56The 57.Fn malloc 58function allocates uninitialized memory in kernel address space for an 59object whose size is specified by 60.Fa size . 61.Fn free 62releases memory at address 63.Fa addr 64that was previously allocated by 65.Fn malloc 66for re-use. 67The 68.Fn MALLOC 69macro variant is functionally equivalent to 70.Bd -literal -offset indent 71(space) = (cast)malloc((u_long)(size), type, flags) 72.Ed 73.Pp 74and the 75.Fn FREE 76macro variant is equivalent to 77.Bd -literal -offset indent 78free((addr), type) 79.Ed 80.Pp 81Unlike its standard C library counterpart 82.Pq Xr malloc 3 , 83the kernel version takes two more arguments. The 84.Fa flags 85argument further qualifies 86.Fn malloc No Ns 's 87operational characteristics as follows: 88.Bl -tag -offset indent 89.It Dv M_NOWAIT 90Causes 91.Fn malloc 92to return 93.Dv NULL 94if the request cannot be immediately fulfilled due to resource shortage. 95Otherwise, 96.Fn malloc 97may call sleep to wait for resources to be released by other processes. 98If this flag is not set, 99.Fn malloc 100will never return 101.Dv NULL . 102Note that 103.Dv M_WAITOK 104is conveniently defined to be 0, and hence may be or'ed into the 105.Fa flags 106argument to indicate that it's Ok to wait for resources. 107.El 108.Pp 109Currently, only one flag is defined. 110.Pp 111The 112.Fa type 113argument is used to perform statistics on memory usage, and for 114basic sanity checks. 115The statistics can be examined by 116.Sq vmstat -m . 117.Pp 118A 119.Fa type 120is defined using the 121.Va malloc_type_t 122typedef like this: 123.Bd -literal -offset indent 124/* sys/something/foo_extern.h */ 125 126extern malloc_type_t M_FOOBUF; 127 128/* sys/something/foo_main.c */ 129 130malloc_type_t M_FOOBUF = { 131 "Foo Buffers", 132 "Buffers for foo data in transit to the InfImpDrive" 133}; 134 135/* sys/something/foo_subr.c */ 136 137... 138MALLOC(buf, struct foo_buf *, sizeof *buf, M_FOOBUF, M_NOWAIT); 139 140.Be 141.Sh RETURN VALUES 142.Fn malloc 143returns a kernel virtual address that is suitably aligned for storage of 144any type of object. 145.Sh SEE ALSO 146.Xr vmstat 8 147.Sh DIAGNOSTICS 148A kernel compiled with the 149.Dv DIAGNOSTIC 150configuration option attempts to detect detect memory corruption caused by 151such things as writing outside the allocated area and imbalanced calls to the 152.Fn malloc 153and 154.Fn free 155functions. Failing consistency checks will cause a panic or a system console 156message: 157.Bl -bullet -offset indent -compact 158.Pp 159.It 160panic: 161.Dq malloc: bogus type 162.It 163panic: 164.Dq malloc: allocation too large 165.It 166panic: 167.Dq malloc: wrong bucket 168.It 169panic: 170.Dq malloc: lost data 171.It 172panic: 173.Dq free: address 0x%x out of range 174.It 175panic: 176.Dq free: type %d out of range 177.It 178panic: 179.Dq free: unaligned addr Aq description of object 180.It 181panic: 182.Dq free: item modified 183.It 184panic: 185.Dq free: multiple free[s] 186.It 187.Dq Data modified on freelist: Aq description of object 188.El 189