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.\" Copyright (c) 1991, 1993
.\" The Regents of the University of California. 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.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
.\"
.\" @(#)mprotect.2 8.1 (Berkeley) 6/9/93
.\" $FreeBSD$
.\"
.Dd June 9, 1993
.Dt MPROTECT 2
.Os
.Sh NAME
.Nm mprotect
.Nd control the protection of pages
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/mman.h
.Ft int
.Fn mprotect "const void *addr" "size_t len" "int prot"
.Sh DESCRIPTION
The
.Fn mprotect
system call
changes the specified pages to have protection
.Fa prot .
Not all implementations will guarantee protection on a page basis;
the granularity of protection changes may be as large as an entire region.
A region is the virtual address space defined by the start
and end addresses of a
.Vt "struct vm_map_entry" .
.Pp
Currently these protection bits are known,
which can be combined, OR'd together:
.Pp
.Bl -tag -width ".Dv PROT_WRITE" -compact
.It Dv PROT_NONE
No permissions at all.
.It Dv PROT_READ
The pages can be read.
.It Dv PROT_WRITE
The pages can be written.
.It Dv PROT_EXEC
The pages can be executed.
.El
.Sh RETURN VALUES
.Rv -std mprotect
.Sh ERRORS
The
.Fn mprotect
system call will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The virtual address range specified by the
.Fa addr
and
.Fa len
arguments is not valid.
.It Bq Er EACCES
The calling process was not allowed to change
the protection to the value specified by
the
.Fa prot
argument.
.El
.Sh SEE ALSO
.Xr madvise 2 ,
.Xr mincore 2 ,
.Xr msync 2 ,
.Xr munmap 2
.Sh HISTORY
The
.Fn mprotect
system call first appeared in
.Bx 4.4 .
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