usr/src/cmd/sgs/0@0/common/0@0.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  *      Copyright (c) 1996 by Sun Microsystems, Inc.
  24  *
  25  * Map in a read-only page of zeroes at location zero, for stupid
  26  * programs that think a null pointer is as good as a null string.
  27  *
  28  * Use:
  29  *      LD_PRELOAD=0@0.so.1 program args ...
  30  *
  31  */
  32 #pragma ident   "%Z%%M% %I%     %E% SMI"
  33
  34 /* LINTLIBRARY */
  35
  36 #include <sys/types.h>
  37 #include <sys/mman.h>
  38 #include <fcntl.h>
  39 #include <unistd.h>
  40
  41 #pragma init(__zero_at_zero)
  42
  43 void
  44 __zero_at_zero()
  45 {
  46         int fd;
  47
  48         if ((fd = open("/dev/zero", O_RDWR)) < 0)
  49                 return;
  50         (void) mmap(0, 1, PROT_READ, MAP_PRIVATE|MAP_FIXED, fd, 0);
  51         (void) close(fd);
  52 }