1.\" Copyright (c) 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)mprotect.2 8.1 (Berkeley) 6/9/93 29.\" $FreeBSD$ 30.\" 31.Dd February 26, 2020 32.Dt MPROTECT 2 33.Os 34.Sh NAME 35.Nm mprotect 36.Nd control the protection of pages 37.Sh LIBRARY 38.Lb libc 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 47changes the specified pages to have protection 48.Fa prot . 49Not all implementations will guarantee protection on a page basis; 50the granularity of protection changes may be as large as an entire region. 51A region is the virtual address space defined by the start 52and end addresses of a 53.Vt "struct vm_map_entry" . 54.Pp 55Currently these protection bits are known, 56which can be combined, OR'd together: 57.Pp 58.Bl -tag -width ".Dv PROT_WRITE" -compact 59.It Dv PROT_NONE 60No permissions at all. 61.It Dv PROT_READ 62The pages can be read. 63.It Dv PROT_WRITE 64The pages can be written. 65.It Dv PROT_EXEC 66The pages can be executed. 67.El 68.Pp 69In addition to these protection flags, 70.Fx 71provides the ability to set the maximum protection of a region 72(which prevents 73.Nm 74from upgrading the permissions). 75This is accomplished by 76.Em or Ns 'ing 77one or more 78.Dv PROT_ 79values wrapped in the 80.Dv PROT_MAX() 81macro into the 82.Fa prot 83argument. 84.Sh RETURN VALUES 85.Rv -std mprotect 86.Sh ERRORS 87The 88.Fn mprotect 89system call will fail if: 90.Bl -tag -width Er 91.It Bq Er EACCES 92The calling process was not allowed to change 93the protection to the value specified by 94the 95.Fa prot 96argument. 97.It Bq Er EINVAL 98The virtual address range specified by the 99.Fa addr 100and 101.Fa len 102arguments is not valid. 103.It Bq Er EINVAL 104The 105.Fa prot 106argument contains unhandled bits. 107.It Bq Er ENOTSUP 108The 109.Fa prot 110argument contains permissions which are not a subset of the specified 111maximum permissions. 112.El 113.Sh SEE ALSO 114.Xr madvise 2 , 115.Xr mincore 2 , 116.Xr msync 2 , 117.Xr munmap 2 118.Sh HISTORY 119The 120.Fn mprotect 121system call was first documented in 122.Bx 4.2 123and first appeared in 124.Bx 4.4 . 125.Pp 126The 127.Dv PROT_MAX 128functionality was introduced in 129.Fx 13 . 130