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 February 22, 2005 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.Nm 51takes over 52.Dv M_SUBPROC 53allocations by default. 54.Sh FILES 55.Bl -tag -width ".Pa src/sys/kern/kern_malloc.c" -compact 56.It Pa src/sys/kern/kern_malloc.c 57File to replace the malloc type in 58.El 59.Sh EXAMPLES 60The following steps are necessary to use 61.Nm : 62.Bl -enum 63.It 64Put the 65.Dv DEBUG_MEMGUARD 66option into your kernel config. 67.It 68Open 69.Pa src/sys/kern/kern_malloc.c 70in your favourite editor. 71Look for lines containing 72.Dq Li "XXX CHANGEME!" 73and replace 74.Dv M_SUBPROC 75with the appropriate malloc type. 76This might require additional but small/simple 77code modifications 78(e.g., if the malloc type is declared out of scope). 79.It 80Build and install your kernel. 81Tune the 82.Va vm.memguard_divisor 83boot-time tunable, which is used to scale how much of 84.Va kmem_map 85you want to allot for 86.Nm . 87The default is 10, so 88.Va kmem_size Ns /10 89bytes will be used. 90The 91.Va kmem_size 92value can be obtained via the 93.Va vm.kmem_size 94.Xr sysctl 8 95variable. 96.El 97.Sh SEE ALSO 98.Xr sysctl 8 , 99.Xr vmstat 8 , 100.Xr contigmalloc 9 , 101.Xr malloc 9 102.Sh HISTORY 103.Nm 104first appeared in 105.Fx 6.0 . 106.Sh AUTHORS 107.An -nosplit 108.Nm 109was written by 110.An Bosko Milekic Aq bmilekic@FreeBSD.org . 111This manual page was written by 112.An Christian Brueffer Aq brueffer@FreeBSD.org . 113.Sh BUGS 114Currently, it is not possible to override UMA 115.Xr zone 9 116allocations. 117