.\"	$OpenBSD: mprotect.2,v 1.14 2007/05/31 19:19:33 jmc Exp $
.\"	$NetBSD: mprotect.2,v 1.6 1995/10/12 15:41:08 jtc Exp $
.\"
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.\"	@(#)mprotect.2	8.1 (Berkeley) 6/9/93
.\"
.Dd $Mdocdate: May 31 2007 $
.Dt MPROTECT 2
.Os
.Sh NAME
.Nm mprotect
.Nd control the protection of pages
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/mman.h>
.Ft int
.Fn mprotect "void *addr" "size_t len" "int prot"
.Sh DESCRIPTION
The
.Fn mprotect
system call sets the access protections for the pages that contain
the address range
.Fa addr
through
.Fa addr
\&+
.Fa len
\- 1
(inclusive).
If
.Fa len
is 0, then action will be taken on the page that contains
.Fa addr .
.Pp
Not all implementations will guarantee protection on a page basis;
the granularity of protection changes may be as large as an entire region.
Nor will all implementations guarantee to give exactly the requested
permissions; more permissions may be granted than requested by
.Fa prot .
.Pp
The protections (region accessibility) are specified in the
.Fa prot
argument by
.Tn OR Ns 'ing
the following values:
.Pp
.Bl -tag -width "PROT_WRITEXX" -offset indent -compact
.It Dv PROT_EXEC
Pages may be executed.
.It Dv PROT_READ
Pages may be read.
.It Dv PROT_WRITE
Pages may be written.
.It Dv PROT_NONE
No permissions.
.El
.Sh RETURN VALUES
Upon successful completion,
a value of 0 is returned.
Otherwise, a value of \-1 is returned and
.Va errno
is set to indicate the error.
.Sh SEE ALSO
.Xr madvise 2 ,
.Xr mincore 2 ,
.Xr msync 2 ,
.Xr munmap 2
.Sh HISTORY
The
.Fn mprotect
function first appeared in
.Bx 4.4 .
.Sh CAVEATS
The
.Ox
implementation of
.Fn mprotect
does not require
.Fa addr
to be page-aligned,
although other implementations may.