1.\" Copyright (c) 2005 Christian Brueffer 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd January 31, 2006 28.Dt MEMGUARD 9 29.Os 30.Sh NAME 31.Nm MemGuard 32.Nd "memory allocator for debugging purposes" 33.Sh SYNOPSIS 34.Cd "options DEBUG_MEMGUARD" 35.Sh DESCRIPTION 36.Nm 37is a simple and small replacement memory allocator designed 38to help detect tamper-after-free scenarios. 39These problems are more and more common and likely with 40multithreaded kernels where race conditions are more prevalent. 41.Pp 42Currently, 43.Nm 44can only take over 45.Fn malloc , 46.Fn realloc 47and 48.Fn free 49for a particular malloc type. 50.Sh EXAMPLES 51To use 52.Nm 53for memory type compiled into the kernel, one has to add the 54following line to the 55.Pa /boot/loader.conf : 56.Bd -literal -offset indent 57vm.memguard.desc=<memory_type> 58.Ed 59.Pp 60Where 61.Ar memory_type 62is a short description of memory type to monitor. 63The short description of memory type is the second argument to 64.Xr MALLOC_DEFINE 9 , 65so one has to find it in the kernel source. 66.Pp 67To use 68.Nm 69for memory type defined in a kernel module, one has to set 70.Va vm.memguard.desc 71.Xr sysctl 8 72variable before loading the module: 73.Bd -literal -offset indent 74sysctl vm.memguard.desc=<memory_type> 75.Ed 76.Pp 77The 78.Va vm.memguard.divisor 79boot-time tunable is used to scale how much of 80.Va kmem_map 81one wants to allocate for 82.Nm . 83The default is 10, so 84.Va kmem_size Ns /10 85bytes will be used. 86The 87.Va kmem_size 88value can be obtained via the 89.Va vm.kmem_size 90.Xr sysctl 8 91variable. 92.Sh SEE ALSO 93.Xr sysctl 8 , 94.Xr vmstat 8 , 95.Xr contigmalloc 9 , 96.Xr malloc 9 , 97.Xr redzone 9 98.Sh HISTORY 99.Nm 100first appeared in 101.Fx 6.0 . 102.Sh AUTHORS 103.An -nosplit 104.Nm 105was written by 106.An Bosko Milekic Aq bmilekic@FreeBSD.org . 107This manual page was written by 108.An Christian Brueffer Aq brueffer@FreeBSD.org . 109.Sh BUGS 110Currently, it is not possible to override UMA 111.Xr zone 9 112allocations. 113