1.\" $OpenBSD: mprotect.2,v 1.27 2022/10/07 15:21:04 deraadt Exp $ 2.\" $NetBSD: mprotect.2,v 1.6 1995/10/12 15:41:08 jtc Exp $ 3.\" 4.\" Copyright (c) 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)mprotect.2 8.1 (Berkeley) 6/9/93 32.\" 33.Dd $Mdocdate: October 7 2022 $ 34.Dt MPROTECT 2 35.Os 36.Sh NAME 37.Nm mprotect 38.Nd control the protection of pages 39.Sh SYNOPSIS 40.In sys/mman.h 41.Ft int 42.Fn mprotect "void *addr" "size_t len" "int prot" 43.Sh DESCRIPTION 44The 45.Fn mprotect 46system call sets the access protections for the pages that contain 47the address range 48.Fa addr 49through 50.Fa addr 51\&+ 52.Fa len 53\- 1 54(inclusive). 55If 56.Fa len 57is 0, no action is taken on the page that contains 58.Fa addr . 59.Pp 60The protections (region accessibility) are specified in the 61.Fa prot 62argument. 63It should either be 64.Dv PROT_NONE 65.Pq no permissions 66or the bitwise OR of one or more of the following values: 67.Pp 68.Bl -tag -width "PROT_WRITEXX" -offset indent -compact 69.It Dv PROT_EXEC 70Pages may be executed. 71.It Dv PROT_READ 72Pages may be read. 73.It Dv PROT_WRITE 74Pages may be written. 75.El 76.Pp 77Not all implementations will guarantee protection on a page basis; 78the granularity of protection changes may be as large as an entire region. 79Nor will all implementations guarantee to give exactly the requested 80permissions; more permissions may be granted than requested by 81.Fa prot . 82However, if 83.Dv PROT_WRITE 84was not specified then the page will not be writable. 85.Sh RETURN VALUES 86.Rv -std 87.Sh ERRORS 88.Fn mprotect 89will fail if: 90.Bl -tag -width Er 91.It Bq Er EACCES 92The process does not have sufficient access to the underlying memory 93object to provide the requested protection. 94.It Bq Er ENOMEM 95The process has locked future pages with 96.Fn mlockall MCL_FUTURE , 97a page being protected is not currently accessible, 98and making it accessible and locked would exceed process or system limits. 99.It Bq Er ENOTSUP 100The accesses requested in the 101.Fa prot 102argument are not allowed. 103In particular, 104.Dv PROT_WRITE | PROT_EXEC 105mappings are not permitted in most binaries (see 106.Dv kern.wxabort 107in 108.Xr sysctl 2 109for more information). 110.It Bq Er EINVAL 111The 112.Fa prot 113argument is invalid or the specified address range would wrap around. 114.It Bq Er EPERM 115The 116.Fa addr 117and 118.Fa len 119parameters 120specify a region which contains at least one page marked immutable. 121.El 122.Sh SEE ALSO 123.Xr madvise 2 , 124.Xr msync 2 , 125.Xr munmap 2 126.Sh STANDARDS 127The 128.Fn mprotect 129function conforms to 130.St -p1003.1-2008 . 131.Sh HISTORY 132The 133.Fn mprotect 134function has been available since 135.Bx 4.3 Net/2 . 136.Sh CAVEATS 137The 138.Ox 139implementation of 140.Fn mprotect 141does not require 142.Fa addr 143to be page-aligned, 144although other implementations may. 145