117 lines
3.1 KiB
Groff
117 lines
3.1 KiB
Groff
.\" Copyright (c) 2005 Christian Brueffer
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd February 22, 2005
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.Dt MEMGUARD 9
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.Os
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.Sh NAME
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.Nm MemGuard
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.Nd "memory allocator for debugging purposes"
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.Sh SYNOPSIS
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.Cd "options DEBUG_MEMGUARD"
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.Sh DESCRIPTION
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.Nm
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is a simple and small replacement memory allocator designed
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to help detect tamper-after-free scenarios.
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These problems are more and more common and likely with
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multithreaded kernels where race conditions are more prevalent.
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.Pp
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Currently,
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.Nm
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can only take over
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.Fn malloc ,
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.Fn realloc
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and
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.Fn free
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for a particular malloc type.
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.Nm
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takes over
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.Dv M_SUBPROC
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allocations by default.
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.Sh FILES
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.Bl -tag -width ".Pa src/sys/kern/kern_malloc.c" -compact
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.It Pa src/sys/kern/kern_malloc.c
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File to replace the malloc type in
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.El
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.Sh EXAMPLES
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The following steps are necessary to use
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.Nm :
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.Bl -enum
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.It
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Put the
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.Dv DEBUG_MEMGUARD
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option into your kernel config.
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.It
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Open
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.Pa src/sys/kern/kern_malloc.c
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in your favourite editor.
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Look for lines containing
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.Dq Li "XXX CHANGEME!"
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and replace
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.Dv M_SUBPROC
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with the appropriate malloc type.
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This might require additional but small/simple
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code modifications
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(e.g., if the malloc type is declared out of scope).
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.It
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Build and install your kernel.
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Tune the
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.Va vm.memguard_divisor
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boot-time tunable, which is used to scale how much of
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.Va kmem_map
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you want to allot for
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.Nm .
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The default is 10, so
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.Va kmem_size Ns /10
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bytes will be used.
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The
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.Va kmem_size
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value can be obtained via the
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.Va vm.kmem_size
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.Xr sysctl 8
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variable.
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.El
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.Sh SEE ALSO
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.Xr sysctl 8 ,
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.Xr vmstat 8 ,
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.Xr contigmalloc 9 ,
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.Xr malloc 9
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.Sh HISTORY
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.Nm
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first appeared in
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.Fx 6.0 .
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.Sh AUTHORS
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.An -nosplit
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.Nm
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was written by
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.An Bosko Milekic Aq bmilekic@FreeBSD.org .
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This manual page was written by
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.An Christian Brueffer Aq brueffer@FreeBSD.org .
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.Sh BUGS
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Currently, it is not possible to override UMA
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.Xr zone 9
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allocations.
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