.\" -*- nroff -*-
.\" Copyright (C) 2007 Michael Kerrisk <mtk.manpages@gmail.com>
.\" and Copyright (C) 1995 Michael Shields <shields@tembel.org>.
.\"
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.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and author of this work.
.\"
.\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 1997-05-31 by Andries Brouwer <aeb@cwi.nl>
.\" Modified 2003-08-24 by Andries Brouwer <aeb@cwi.nl>
.\" Modified 2004-08-16 by Andi Kleen <ak@muc.de>
.\" 2007-06-02, mtk: Fairly substantial rewrites and additions, and
.\" a much improved example program.
.\"
.\" Japanese Version Copyright (c) 1997 HANATAKA Shinya
.\"         all rights reserved.
.\" Translated 1997-06-01, HANATAKA Shinya <hanataka@abyss.rim.or.jp>
.\" Updated and revised 2003-10-24, Suzuki Takashi.
.\" Updated & Modified 2005-02-08, Yuichi SATO <ysato444@yahoo.co.jp>
.\" Updated & Modified 2005-10-15, Yuichi SATO
.\" Updated 2007-06-11, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>, LDP v2.54
.\"
.\"WORD: bitwise-or             ӥåȤȤ
.\"WORD: protection             ݸ
.\"WORD: read-only              ɤ߼
.\"
.TH MPROTECT 2 2007-06-02 "Linux" "Linux Programmer's Manual"
.SH ̾
mprotect \- ΰݸꤹ
.SH 
.nf
.B #include <sys/mman.h>
.sp
.BI "int mprotect(const void *" addr ", size_t *" len ", int " prot );
.fi
.SH 
.BR mprotect ()
ϡ [\fIaddr\fP,\ \fIaddr\fP+\fIlen\fP\-1] Υɥ쥹ϰϤޤ
ƤӽФΥץΥڡΥݸѹ롣
.I addr
ϥڡ˰פƤʤФʤʤ

ƤӽФΥץݸ˰ȿ褦ʥꥢ
ԤȤȡͥϥʥ
.B SIGSEGV
򤽤ΥץФ롣
.PP
.I prot
ˤϡ
.B PROT_NONE
ʲΥꥹȤ
.B PROT_NONE
ʳͤӥå (bitwize-or) ǻꤹ:
.TP 1.1i
.B PROT_NONE
ΥˤǤʤ
.TP
.B PROT_READ
Υɤ߼뤳ȤǤ롣
.TP
.B PROT_WRITE
ΥѹǤ롣
.TP
.B PROT_EXEC
Υϼ¹ԲǽǤ롣
.\" FIXME
.\" Document PROT_GROWSUP and PROT_GROWSDOWN
.SH ֤
硢
.BR mprotect ()
 0 ֤顼ξ \-1 ֤ꡢ
.I errno
Ŭڤꤵ롣
.SH 顼
.TP
.B EACCES
ꤵ줿ꤹ뤳ȤǤʤ
ϡ㤨
եɤ߼Ѥ
.BR mmap (2)
ƤꡢΰФ
.BR mprotect ()
ƤӽФ
.B PROT_WRITE
ꤷ褦Ȥȯ롣
.TP
.B EFAULT
꤬ǽǤʤ
.TP
.B EINVAL
\fIaddr\fP ͭʥݥ󥿤Ǥʤ
ƥΥڡܿǤʤ
.\" Or: both PROT_GROWSUP and PROT_GROWSDOWN were specified in 'prot'.
.TP
.B ENOMEM
ͥι¤ΤƤ뤳ȤǤʤä
⤷ϡ
.RI [ addr ,
.IR addr + len ]
ȤϰϤΥɥ쥹ץΥɥ쥹֤ȤǤ뤫
ϰϤΥɥ쥹ޥåפƤʤ 1 İʾΥڡؤ
.SH 
SVr4, POSIX.1-2001.
.\" SVr4 Ǥ¾˥顼 EAGAIN Ƥ롣
.\" SVr4 Υ顼 Linux ΤΤˤбʤ
POSIX Ǥϡ
.BR mmap (2)
ͳdzƤʤΰФ
.BR mprotect ()
Ԥä
.BR mprotect ()
ư̤ǤȤƤ롣
.SH 
Linux Ǥϡ(ͥ vsyscall ΰʳ)
ǤդΥץɥ쥹֤Ф
.BR mprotect ()
ƤӽФȤ˵Ƥ롣
ä˴¸Υɥޥåԥ󥰤񤭹߲ǽˤ뤿˻Ȥ롣

.B PROT_EXEC

.B PROT_READ
ȰۤʤƶĤݤϡƥȥͥΥС˰¸롣
(i386 ʤɤ) ĤΥƥǤϡ
.B PROT_WRITE
򥻥åȤȡۤΤ
.B PROT_READ
åȤ롣

POSIX.1-2001 Ǥϡ
.I prot
ǻꤵƤʤĤǧƤ롣
¡
.B PROT_WRITE
åȤƤˤΤ߽񤭹ߥĤ졢
.B PROT_NONE
åȤƤˤϥϵĤʤ
ɬפ롣
.SH 
.\" sigaction.2 refers to this example
.PP
ʲΥץϡڡ 4ijݤΤ 3ܤΥڡ
ɤ߹Ѥꤹ롣θǡݤΰΥɥ쥹ξ
礭˸äƽ֤˥Хͤѹ롼פ¹Ԥ롣

ץ¹Ԥΰʲ˼

.in +4n
.nf
$ ./a.out
Start of region:        0x804c000
Got SIGSEGV at address: 0x804e000
.fi
.in
.nf

#include <unistd.h>
#include <signal.h>
#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/mman.h>

#define handle_error(msg) \\
    do { perror(msg); exit(EXIT_FAILURE); } while (0)

char *buffer;

static void
handler(int sig, siginfo_t *si, void *unused)
{
    printf("Got SIGSEGV at address: 0x%lx\\n",
            (long) si\->si_addr);
    exit(EXIT_FAILURE);
}

int
main(void)
{
    char *p;
    int pagesize;
    struct sigaction sa;

    sa.sa_flags = SA_SIGINFO;
    sigemptyset(&sa.sa_mask);
    sa.sa_sigaction = handler;
    if (sigaction(SIGSEGV, &sa, NULL) == \-1)
        handle_error("sigaction");

    pagesize = sysconf(_SC_PAGE_SIZE);
    if (pagesize == \-1)
        handle_error("sysconf");

    /* Allocate a buffer aligned on a page boundary;
       initial protection is PROT_READ | PROT_WRITE */

    buffer = memalign(pagesize, 4 * pagesize);
    if (buffer == NULL)
        handle_error("memalign");

    printf("Start of region:        0x%lx\\n", (long) buffer);

    if (mprotect(buffer + pagesize * 2, pagesize,
                PROT_NONE) == \-1)
        handle_error("mprotect");

    for (p = buffer ; ; )
        *(p++) = 'a';

    printf("Loop completed\\n");     /* Should never happen */
    exit(EXIT_SUCCESS);
}
.fi
.SH Ϣ
.BR mmap (2),
.BR sysconf (3)