MPROTECT

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#include <sys/mman.h>

int mprotect(const void *addr, size_t len, int prot);

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prot ¤Ï°Ê²¼¤ÎÃÍ¤Î¥Ó¥Ã¥È OR ¤Ç¤¢¤ë:

PROT_NONE

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PROT_READ

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PROT_WRITE

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PROT_EXEC

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EINVAL

addr ¤¬Í­¸ú¤Ê¥Ý¥¤¥ó¥¿¡¼¤Ç¤Ê¤¤¤«¡¢PAGESIZE ¤ÎÇÜ¿ô¤Ç¤Ê¤¤¡£

EFAULT

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EACCES

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ENOMEM

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

#include <limits.h>    /* for PAGESIZE */
#ifndef PAGESIZE
#define PAGESIZE 4096
#endif

int
main(void)
{
    char *p;
    char c;

    /* Allocate a buffer; it will have the default
       protection of PROT_READ|PROT_WRITE. */
    p = malloc(1024+PAGESIZE-1);
    if (!p) {
        perror("Couldn't malloc(1024)");
        exit(errno);
    }

    /* Align to a multiple of PAGESIZE, assumed to be a power of two */
    p = (char *)(((int) p + PAGESIZE-1) & ~(PAGESIZE-1));

    c = p[666];         /* Read; ok */
    p[666] = 42;        /* Write; ok */

    /* Mark the buffer read-only. */
    if (mprotect(p, 1024, PROT_READ)) {
        perror("Couldn't mprotect");
        exit(errno);
    }

    c = p[666];         /* Read; ok */
    p[666] = 42;        /* Write; program dies on SIGSEGV */

    exit(0);
}

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