.\"	$NetBSD: mprotect.2,v 1.27 2019/06/19 20:28:36 uwe Exp $
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.\"	@(#)mprotect.2	8.1 (Berkeley) 6/9/93
.\"
.Dd April 27, 2017
.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 "void *addr" "size_t len" "int prot"
.Sh DESCRIPTION
The
.Nm
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.
.Pp
The protections (region accessibility) are specified in the
.Fa prot
argument by
.Tn OR Ns 'ing
the following values:
.Pp
.Bl -tag -width "Dv MAP_WRITE" -offset indent
.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
Placeholder when requesting no access permission.
.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
.Bl -tag -width Er
.It Bq Er EACCES
A memory protection violation occurred.
.Pp
The
.Dv PROT_EXEC
flag was attempted on pages which belong to a file system mounted with the
.Dv NOEXEC
flag.
.Pp
The new protection is less restrictive than the protection originally
set with
.Xr mmap 2 .
.Pp
PaX mprotect restrictions prohibit the requested protection.
.It Bq Er EINVAL
An invalid memory range, or invalid parameters were provided.
.It Bq Er ENOMEM
A resource shortage occurred while internally calling
.Xr uvm_map_protect 9 .
.El
.Sh SEE ALSO
.Xr madvise 2 ,
.Xr mincore 2 ,
.Xr msync 2 ,
.Xr munmap 2
.Sh HISTORY
The
.Nm
function first appeared in
.Bx 4.4 .