usr/src/lib/libc/port/gen/getauxv.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 (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 #pragma ident   "%Z%%M% %I%     %E% SMI"
  28
  29 #include "lint.h"
  30 #include <libc.h>
  31 #include <fcntl.h>
  32 #include <stdlib.h>
  33 #include <unistd.h>
  34 #include <sys/types.h>
  35 #include <sys/stat.h>
  36 #include <sys/auxv.h>
  37 #include <mtlib.h>
  38 #include <thread.h>
  39 #include <synch.h>
  40 #include <atomic.h>
  41
  42 static mutex_t auxlock = DEFAULTMUTEX;
  43
  44 /*
  45  * Get auxiliary entry.
  46  * Returns pointer to entry, or 0 if entry does not exist.
  47  */
  48 static auxv_t *
  49 _getaux(int type)
  50 {
  51         static auxv_t *auxb = NULL;
  52         static size_t nauxv = 0;
  53         ssize_t i;
  54
  55         /*
  56          * The first time through, read the initial aux vector that was
  57          * passed to the process at exec(2).  Only do this once.
  58          */
  59         if (auxb == NULL) {
  60                 lmutex_lock(&auxlock);
  61                 if (auxb == NULL) {
  62                         struct stat statb;
  63                         auxv_t *buf = NULL;
  64                         int fd;
  65
  66                         if ((fd = open("/proc/self/auxv", O_RDONLY)) != -1 &&
  67                             fstat(fd, &statb) != -1)
  68                                 buf = libc_malloc(
  69                                     statb.st_size + sizeof (auxv_t));
  70
  71                         if (buf != NULL) {
  72                                 i = read(fd, buf, statb.st_size);
  73                                 if (i != -1) {
  74                                         nauxv = i / sizeof (auxv_t);
  75                                         buf[nauxv].a_type = AT_NULL;
  76                                 } else {
  77                                         libc_free(buf);
  78                                         buf = NULL;
  79                                 }
  80                         }
  81
  82                         if (fd != -1)
  83                                 (void) close(fd);
  84
  85                         membar_producer();
  86                         auxb = buf;
  87                 }
  88                 lmutex_unlock(&auxlock);
  89         }
  90         membar_consumer();
  91
  92         /*
  93          * Scan the auxiliary entries looking for the required type.
  94          */
  95         for (i = 0; i < nauxv; i++)
  96                 if (auxb[i].a_type == type)
  97                         return (&auxb[i]);
  98
  99         /*
 100          * No auxiliary array (static executable) or entry not found.
 101          */
 102         return ((auxv_t *)0);
 103 }
 104
 105 /*
 106  * These two routines are utilities exported to the rest of libc.
 107  */
 108
 109 long
 110 ___getauxval(int type)
 111 {
 112         auxv_t *auxp;
 113
 114         if ((auxp = _getaux(type)) != (auxv_t *)0)
 115                 return (auxp->a_un.a_val);
 116         return (0);
 117 }
 118
 119 void *
 120 ___getauxptr(int type)
 121 {
 122         auxv_t *auxp;
 123
 124         if ((auxp = _getaux(type)) != (auxv_t *)0)
 125                 return (auxp->a_un.a_ptr);
 126         return (0);
 127 }