1994-05-27 05:00:24 +00:00
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.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. 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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2017-02-28 23:42:47 +00:00
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.\" 3. Neither the name of the University nor the names of its contributors
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1994-05-27 05:00:24 +00:00
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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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Implement address space guards.
Guard, requested by the MAP_GUARD mmap(2) flag, prevents the reuse of
the allocated address space, but does not allow instantiation of the
pages in the range. It is useful for more explicit support for usual
two-stage reserve then commit allocators, since it prevents accidental
instantiation of the mapping, e.g. by mprotect(2).
Use guards to reimplement stack grow code. Explicitely track stack
grow area with the guard, including the stack guard page. On stack
grow, trivial shift of the guard map entry and stack map entry limits
makes the stack expansion. Move the code to detect stack grow and
call vm_map_growstack(), from vm_fault() into vm_map_lookup().
As result, it is impossible to get random mapping to occur in the
stack grow area, or to overlap the stack guard page.
Enable stack guard page by default.
Reviewed by: alc, markj
Man page update reviewed by: alc, bjk, emaste, markj, pho
Tested by: pho, Qualys
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D11306 (man pages)
2017-06-24 17:01:11 +00:00
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.Dd June 22, 2017
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1994-05-27 05:00:24 +00:00
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.Dt MUNMAP 2
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.Os
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.Sh NAME
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.Nm munmap
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.Nd remove a mapping
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2000-04-21 09:42:15 +00:00
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.Sh LIBRARY
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.Lb libc
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1994-05-27 05:00:24 +00:00
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.Sh SYNOPSIS
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2001-10-01 16:09:29 +00:00
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.In sys/mman.h
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1997-01-11 23:33:18 +00:00
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.Ft int
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1997-12-31 01:22:01 +00:00
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.Fn munmap "void *addr" "size_t len"
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1994-05-27 05:00:24 +00:00
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.Sh DESCRIPTION
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The
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.Fn munmap
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system call
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Implement address space guards.
Guard, requested by the MAP_GUARD mmap(2) flag, prevents the reuse of
the allocated address space, but does not allow instantiation of the
pages in the range. It is useful for more explicit support for usual
two-stage reserve then commit allocators, since it prevents accidental
instantiation of the mapping, e.g. by mprotect(2).
Use guards to reimplement stack grow code. Explicitely track stack
grow area with the guard, including the stack guard page. On stack
grow, trivial shift of the guard map entry and stack map entry limits
makes the stack expansion. Move the code to detect stack grow and
call vm_map_growstack(), from vm_fault() into vm_map_lookup().
As result, it is impossible to get random mapping to occur in the
stack grow area, or to overlap the stack guard page.
Enable stack guard page by default.
Reviewed by: alc, markj
Man page update reviewed by: alc, bjk, emaste, markj, pho
Tested by: pho, Qualys
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D11306 (man pages)
2017-06-24 17:01:11 +00:00
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deletes the mappings and guards for the specified address range,
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1994-05-27 05:00:24 +00:00
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and causes further references to addresses within the range
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to generate invalid memory references.
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.Sh RETURN VALUES
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2001-08-09 13:32:13 +00:00
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.Rv -std munmap
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1994-05-27 05:00:24 +00:00
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.Sh ERRORS
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2002-12-18 09:22:32 +00:00
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The
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.Fn munmap
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system call
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1994-05-27 05:00:24 +00:00
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The
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.Fa addr
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2002-12-19 09:40:28 +00:00
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argument was not page aligned, the
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1994-05-27 05:00:24 +00:00
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.Fa len
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2003-11-10 08:02:05 +00:00
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argument was zero or negative, or
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1997-03-11 11:35:56 +00:00
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some part of the region being unmapped is outside the
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valid address range for a process.
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2000-12-29 14:08:20 +00:00
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.El
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1994-05-27 05:00:24 +00:00
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.Sh "SEE ALSO"
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.Xr madvise 2 ,
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1996-02-11 22:38:05 +00:00
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.Xr mincore 2 ,
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2002-01-07 06:12:25 +00:00
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.Xr mmap 2 ,
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1997-01-11 23:33:18 +00:00
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.Xr mprotect 2 ,
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1997-01-20 23:23:22 +00:00
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.Xr msync 2 ,
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1996-02-11 22:38:05 +00:00
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.Xr getpagesize 3
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1994-05-27 05:00:24 +00:00
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.Sh HISTORY
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The
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.Fn munmap
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2002-12-18 09:22:32 +00:00
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system call first appeared in
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1996-08-22 23:31:07 +00:00
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.Bx 4.4 .
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