cmd/readmmap/readmmap.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * --------------------------------------------------------------
 *  BugId 5047993 : Getting bad read data.
 *
 *  Usage: readmmap <filename>
 *
 *  where:
 *      filename is an absolute path to the file name.
 *
 *  Return values:
 *      1 : error
 *      0 : no errors
 * --------------------------------------------------------------
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/mman.h>

int
main(int argc, char **argv)
{
    char *filename = "badfile";
    size_t size = 4395;
    size_t idx = 0;
    char *buf = NULL;
    char *map = NULL;
    int fd = -1, bytes, retval = 0;
    unsigned seed;

    if (argc < 2 || optind == argc) {
        (void) fprintf(stderr,
            "usage: %s <file name>\n", argv[0]);
        exit(1);
    }

    if ((buf = calloc(1, size)) == NULL) {
        perror("calloc");
        exit(1);
    }

    filename = argv[optind];

    (void) remove(filename);

    fd = open(filename, O_RDWR|O_CREAT|O_TRUNC, 0666);
    if (fd == -1) {
        perror("open to create");
        retval = 1;
        goto end;
    }

    bytes = write(fd, buf, size);
    if (bytes != size) {
        (void) printf("short write: %d != %ud\n", bytes, size);
        retval = 1;
        goto end;
    }

    map = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
    if (map == MAP_FAILED) {
        perror("mmap");
        retval = 1;
        goto end;
    }
    seed = time(NULL);
    srandom(seed);

    idx = random() % size;
    map[idx] = 1;

    if (msync(map, size, MS_SYNC) != 0) {
        perror("msync");
        retval = 1;
        goto end;
    }

    if (munmap(map, size) != 0) {
        perror("munmap");
        retval = 1;
        goto end;
    }

    bytes = pread(fd, buf, size, 0);
    if (bytes != size) {
        (void) printf("short read: %d != %ud\n", bytes, size);
        retval = 1;
        goto end;
    }

    if (buf[idx] != 1) {
        (void) printf(
            "bad data from read!  got buf[%ud]=%d, expected 1\n",
            idx, buf[idx]);
        retval = 1;
        goto end;
    }

    (void) printf("good data from read: buf[%ud]=1\n", idx);
end:
    if (fd != -1) {
        (void) close(fd);
    }
    if (buf != NULL) {
        free(buf);
    }

    return (retval);
}