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freebsd-nq/share/man/man9/memguard.9

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First cut at a manpage for the MemGuard debugging allocator. most content from: bmilekic mdoc lessons by: ru
2005-02-22 17:18:27 +00:00
.\" Copyright (c) 2005 Christian Brueffer
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
Rework memguard(9) to reserve significantly more KVA to detect use-after-free over a longer time. Also release the backing pages of a guarded allocation at free(9) time to reduce the overhead of using memguard(9). Allow setting and varying the malloc type at run-time. Add knobs to allow: - randomly guarding memory - adding un-backed KVA guard pages to detect underflow and overflow - a lower limit on the size of allocations that are guarded Reviewed by: alc Reviewed by: brueffer, Ulrich Spörlein <uqs spoerlein net> (man page) Silence from: -arch Approved by: zml (mentor) MFC after: 1 month
2010-08-11 22:10:37 +00:00
.Dd August 2, 2010
First cut at a manpage for the MemGuard debugging allocator. most content from: bmilekic mdoc lessons by: ru
2005-02-22 17:18:27 +00:00
.Dt MEMGUARD 9
.Os
.Sh NAME
.Nm MemGuard
.Nd "memory allocator for debugging purposes"
.Sh SYNOPSIS
.Cd "options DEBUG_MEMGUARD"
.Sh DESCRIPTION
.Nm
is a simple and small replacement memory allocator designed
to help detect tamper-after-free scenarios.
These problems are more and more common and likely with
multithreaded kernels where race conditions are more prevalent.
.Pp
Currently,
.Nm
Rework memguard(9) to reserve significantly more KVA to detect use-after-free over a longer time. Also release the backing pages of a guarded allocation at free(9) time to reduce the overhead of using memguard(9). Allow setting and varying the malloc type at run-time. Add knobs to allow: - randomly guarding memory - adding un-backed KVA guard pages to detect underflow and overflow - a lower limit on the size of allocations that are guarded Reviewed by: alc Reviewed by: brueffer, Ulrich Spörlein <uqs spoerlein net> (man page) Silence from: -arch Approved by: zml (mentor) MFC after: 1 month
2010-08-11 22:10:37 +00:00
can take over
First cut at a manpage for the MemGuard debugging allocator. most content from: bmilekic mdoc lessons by: ru
2005-02-22 17:18:27 +00:00
.Fn malloc ,
.Fn realloc
and
.Fn free
Rework memguard(9) to reserve significantly more KVA to detect use-after-free over a longer time. Also release the backing pages of a guarded allocation at free(9) time to reduce the overhead of using memguard(9). Allow setting and varying the malloc type at run-time. Add knobs to allow: - randomly guarding memory - adding un-backed KVA guard pages to detect underflow and overflow - a lower limit on the size of allocations that are guarded Reviewed by: alc Reviewed by: brueffer, Ulrich Spörlein <uqs spoerlein net> (man page) Silence from: -arch Approved by: zml (mentor) MFC after: 1 month
2010-08-11 22:10:37 +00:00
for a single malloc type.
.Nm
can also guard all allocations larger than
.Dv PAGE_SIZE ,
and can guard a random fraction of all allocations.
There is also a knob to prevent allocations smaller than a specified
size from being guarded, to limit memory waste.
First cut at a manpage for the MemGuard debugging allocator. most content from: bmilekic mdoc lessons by: ru
2005-02-22 17:18:27 +00:00
.Sh EXAMPLES
Markup fixes.
2006-09-18 15:24:20 +00:00
To use
.Nm
Rework memguard(9) to reserve significantly more KVA to detect use-after-free over a longer time. Also release the backing pages of a guarded allocation at free(9) time to reduce the overhead of using memguard(9). Allow setting and varying the malloc type at run-time. Add knobs to allow: - randomly guarding memory - adding un-backed KVA guard pages to detect underflow and overflow - a lower limit on the size of allocations that are guarded Reviewed by: alc Reviewed by: brueffer, Ulrich Spörlein <uqs spoerlein net> (man page) Silence from: -arch Approved by: zml (mentor) MFC after: 1 month
2010-08-11 22:10:37 +00:00
for a memory type, either add an entry to
Update manual page after last memguard changes. Glanced at by: simon
2005-12-30 12:28:19 +00:00
.Pa /boot/loader.conf :
.Bd -literal -offset indent
vm.memguard.desc=<memory_type>
.Ed
.Pp
Rework memguard(9) to reserve significantly more KVA to detect use-after-free over a longer time. Also release the backing pages of a guarded allocation at free(9) time to reduce the overhead of using memguard(9). Allow setting and varying the malloc type at run-time. Add knobs to allow: - randomly guarding memory - adding un-backed KVA guard pages to detect underflow and overflow - a lower limit on the size of allocations that are guarded Reviewed by: alc Reviewed by: brueffer, Ulrich Spörlein <uqs spoerlein net> (man page) Silence from: -arch Approved by: zml (mentor) MFC after: 1 month
2010-08-11 22:10:37 +00:00
Or set the
Update manual page after last memguard changes. Glanced at by: simon
2005-12-30 12:28:19 +00:00
.Va vm.memguard.desc
.Xr sysctl 8
Rework memguard(9) to reserve significantly more KVA to detect use-after-free over a longer time. Also release the backing pages of a guarded allocation at free(9) time to reduce the overhead of using memguard(9). Allow setting and varying the malloc type at run-time. Add knobs to allow: - randomly guarding memory - adding un-backed KVA guard pages to detect underflow and overflow - a lower limit on the size of allocations that are guarded Reviewed by: alc Reviewed by: brueffer, Ulrich Spörlein <uqs spoerlein net> (man page) Silence from: -arch Approved by: zml (mentor) MFC after: 1 month
2010-08-11 22:10:37 +00:00
variable at run-time:
Update manual page after last memguard changes. Glanced at by: simon
2005-12-30 12:28:19 +00:00
.Bd -literal -offset indent
sysctl vm.memguard.desc=<memory_type>
.Ed
.Pp
Rework memguard(9) to reserve significantly more KVA to detect use-after-free over a longer time. Also release the backing pages of a guarded allocation at free(9) time to reduce the overhead of using memguard(9). Allow setting and varying the malloc type at run-time. Add knobs to allow: - randomly guarding memory - adding un-backed KVA guard pages to detect underflow and overflow - a lower limit on the size of allocations that are guarded Reviewed by: alc Reviewed by: brueffer, Ulrich Spörlein <uqs spoerlein net> (man page) Silence from: -arch Approved by: zml (mentor) MFC after: 1 month
2010-08-11 22:10:37 +00:00
Where
.Ar memory_type
is a short description of the memory type to monitor.
Only allocations from that
.Ar memory_type
made after
.Va vm.memguard.desc
is set will potentially be guarded.
If
.Va vm.memguard.desc
is modified at run-time then only allocations of the new
.Ar memory_type
will potentially be guarded once the
.Xr sysctl 8
is set.
Existing guarded allocations will still be properly released by
.Xr free 9 .
.Pp
The short description of a
.Xr malloc 9
type is the second argument to
.Xr MALLOC_DEFINE 9 ,
so one has to find it in the kernel source.
.Pp
Update manual page after last memguard changes. Glanced at by: simon
2005-12-30 12:28:19 +00:00
The
.Va vm.memguard.divisor
Rework memguard(9) to reserve significantly more KVA to detect use-after-free over a longer time. Also release the backing pages of a guarded allocation at free(9) time to reduce the overhead of using memguard(9). Allow setting and varying the malloc type at run-time. Add knobs to allow: - randomly guarding memory - adding un-backed KVA guard pages to detect underflow and overflow - a lower limit on the size of allocations that are guarded Reviewed by: alc Reviewed by: brueffer, Ulrich Spörlein <uqs spoerlein net> (man page) Silence from: -arch Approved by: zml (mentor) MFC after: 1 month
2010-08-11 22:10:37 +00:00
boot-time tunable is used to scale how much of the system's physical
memory
.Nm
is allowed to consume.
The default is 10, so up to
.Va cnt.v_page_count Ns /10
pages can be used.
.Nm
will reserve
.Va vm_kmem_max
/
.Va vm.memguard.divisor
bytes of virtual address space, limited by twice the physical memory
size.
The physical limit is reported as
.Va vm.memguard.phys_limit
and the virtual space reserved for
.Nm
is reported as
.Va vm.memguard.mapsize .
.Pp
.Nm
will not do page promotions for any allocation smaller than
.Va vm.memguard.minsize
bytes.
The default is 0, meaning all allocations can potentially be guarded.
.Nm
can guard sufficiently large allocations randomly, with average
frequency of every one in 100000 /
.Va vm.memguard.frequency
allocations.
The default is 0, meaning no allocations are randomly guarded.
.Pp
.Nm
can optionally add unmapped guard pages around each allocation to
detect overflow and underflow, if
.Va vm.memguard.options
has the 1 bit set.
This option is enabled by default.
.Nm
will optionally guard all allocations of
.Dv PAGE_SIZE
or larger if
.Va vm.memguard.options
has the 2 bit set.
This option is off by default.
First cut at a manpage for the MemGuard debugging allocator. most content from: bmilekic mdoc lessons by: ru
2005-02-22 17:18:27 +00:00
.Sh SEE ALSO
.Xr sysctl 8 ,
.Xr vmstat 8 ,
.Xr contigmalloc 9 ,
Xref redzone(9)
2006-01-31 17:29:27 +00:00
.Xr malloc 9 ,
.Xr redzone 9
First cut at a manpage for the MemGuard debugging allocator. most content from: bmilekic mdoc lessons by: ru
2005-02-22 17:18:27 +00:00
.Sh HISTORY
.Nm
first appeared in
.Fx 6.0 .
.Sh AUTHORS
.An -nosplit
.Nm
Rework memguard(9) to reserve significantly more KVA to detect use-after-free over a longer time. Also release the backing pages of a guarded allocation at free(9) time to reduce the overhead of using memguard(9). Allow setting and varying the malloc type at run-time. Add knobs to allow: - randomly guarding memory - adding un-backed KVA guard pages to detect underflow and overflow - a lower limit on the size of allocations that are guarded Reviewed by: alc Reviewed by: brueffer, Ulrich Spörlein <uqs spoerlein net> (man page) Silence from: -arch Approved by: zml (mentor) MFC after: 1 month
2010-08-11 22:10:37 +00:00
was originally written by
First cut at a manpage for the MemGuard debugging allocator. most content from: bmilekic mdoc lessons by: ru
2005-02-22 17:18:27 +00:00
.An Bosko Milekic Aq bmilekic@FreeBSD.org .
Rework memguard(9) to reserve significantly more KVA to detect use-after-free over a longer time. Also release the backing pages of a guarded allocation at free(9) time to reduce the overhead of using memguard(9). Allow setting and varying the malloc type at run-time. Add knobs to allow: - randomly guarding memory - adding un-backed KVA guard pages to detect underflow and overflow - a lower limit on the size of allocations that are guarded Reviewed by: alc Reviewed by: brueffer, Ulrich Spörlein <uqs spoerlein net> (man page) Silence from: -arch Approved by: zml (mentor) MFC after: 1 month
2010-08-11 22:10:37 +00:00
This manual page was originally written by
First cut at a manpage for the MemGuard debugging allocator. most content from: bmilekic mdoc lessons by: ru
2005-02-22 17:18:27 +00:00
.An Christian Brueffer Aq brueffer@FreeBSD.org .
Rework memguard(9) to reserve significantly more KVA to detect use-after-free over a longer time. Also release the backing pages of a guarded allocation at free(9) time to reduce the overhead of using memguard(9). Allow setting and varying the malloc type at run-time. Add knobs to allow: - randomly guarding memory - adding un-backed KVA guard pages to detect underflow and overflow - a lower limit on the size of allocations that are guarded Reviewed by: alc Reviewed by: brueffer, Ulrich Spörlein <uqs spoerlein net> (man page) Silence from: -arch Approved by: zml (mentor) MFC after: 1 month
2010-08-11 22:10:37 +00:00
Additions have been made by
.An Matthew Fleming Aq mdf@FreeBSD.org
to both the implementation and the documentation.
First cut at a manpage for the MemGuard debugging allocator. most content from: bmilekic mdoc lessons by: ru
2005-02-22 17:18:27 +00:00
.Sh BUGS
Currently, it is not possible to override UMA
.Xr zone 9
allocations.
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