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.\"	$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
.\" $FreeBSD: src/lib/libc/sys/mprotect.2,v 1.18 2007/01/09 00:28:15 imp Exp $
.\"
.Dd October 16, 2008
.Dt MPROTECT 2
.Os
.Sh NAME
.Nm mprotect
.Nd control the protection of pages
.Sh SYNOPSIS
.Fd #include <sys/mman.h>
.Ft int
.Fo mprotect
.Fa "void *addr"
.Fa "size_t len"
.Fa "int prot"
.Fc
.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 but Mac OS X's
current implementation does.
.Pp
When a program violates the protections of a page, it gets a SIGBUS or SIGSEGV signal. 
.Pp
Currently
.Fa prot
can be one or more of the following:
.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
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 ERRORS
.Fn mprotect
will fail if:
.Bl -tag -width Er
.\" ===========
.It Bq Er EACCES
The requested protection conflicts with
the access permissions of the process
on the specified address range.
.\" ===========
.\" .It Bq Er EAGAIN
.\" Insufficient memory resources exist to allow locking a private page
.\" under PROT_WRITE.
.\" ===========
.It Bq Er EINVAL
.Fa addr
is not a multiple of the page size (i.e.
.Fa addr
is not page-aligned).
.\" ===========
.\" .It Bq Er ENOMEM
.\" The specified address range is outside of the address range
.\" of the process or includes an unmapped page.
.\" ===========
.It Bq Er ENOTSUP
The combination of accesses requested in
.Fa prot
is not supported.
.El
.Sh LEGACY SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/mman.h>
.Pp
The include file
.In sys/types.h
is necessary.
.Pp
.Ft int
.br
.Fo mprotect
.Fa "caddr_t addr"
.Fa "size_t len"
.Fa "int prot"
.Fc ;
.Pp
The type of
.Fa addr
has changed.
.Sh SEE ALSO
.Xr madvise 2 , 
.Xr mincore 2 , 
.Xr msync 2 ,
.Xr munmap 2 ,
.Xr compat 5
.Sh HISTORY
The
.Fn mprotect
function first appeared in 4.4BSD.