1  /*
  2   * Copyright (c) 1987, 1993
  3   *	The Regents of the University of California.  All rights reserved.
  4   *
  5   * Redistribution and use in source and binary forms, with or without
  6   * modification, are permitted provided that the following conditions
  7   * are met:
  8   * 1. Redistributions of source code must retain the above copyright
  9   *    notice, this list of conditions and the following disclaimer.
 10   * 2. Redistributions in binary form must reproduce the above copyright
 11   *    notice, this list of conditions and the following disclaimer in the
 12   *    documentation and/or other materials provided with the distribution.
 13   * 4. Neither the name of the University nor the names of its contributors
 14   *    may be used to endorse or promote products derived from this software
 15   *    without specific prior written permission.
 16   *
 17   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 18   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 19   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 20   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 21   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 22   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 23   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 24   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 25   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 26   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 27   * SUCH DAMAGE.
 28   */
 29  
 30  #if defined(LIBC_SCCS) && !defined(lint)
 31  static char sccsid[] = "@(#)getenv.c	8.1 (Berkeley) 6/4/93";
 32  #endif /* LIBC_SCCS and not lint */
 33  #include <sys/cdefs.h>
 34  __FBSDID("$FreeBSD: src/lib/libc/stdlib/getenv.c,v 1.8 2007/05/01 16:02:41 ache Exp $");
 35  
 36  #include <os/lock_private.h>
 37  #include <stdlib.h>
 38  #include <stddef.h>
 39  #include <string.h>
 40  #include <crt_externs.h>
 41  
 42  __private_extern__ char *__findenv_locked(const char *, int *, char **);
 43  __private_extern__ void __environ_lock(void);
 44  __private_extern__ void __environ_unlock(void);
 45  
 46  /*
 47   * __findenv_locked --
 48   *	Returns pointer to value associated with name, if any, else NULL.
 49   *	Sets offset to be the offset of the name/value combination in the
 50   *	environmental array, for use by setenv(3) and unsetenv(3).
 51   *	Explicitly removes '=' in argument name.
 52   *
 53   *	This routine *should* be a static; don't use it.
 54   */
 55  __private_extern__ char *
 56  __findenv_locked(name, offset, environ)
 57  	const char *name;
 58  	int *offset;
 59  	char **environ;
 60  {
 61  	int len, i;
 62  	const char *np;
 63  	char **p, *cp;
 64  
 65  	if (name == NULL || environ == NULL)
 66  		return (NULL);
 67  	for (np = name; *np && *np != '='; ++np)
 68  		continue;
 69  	len = np - name;
 70  	for (p = environ; (cp = *p) != NULL; ++p) {
 71  		for (np = name, i = len; i && *cp; i--)
 72  			if (*cp++ != *np++)
 73  				break;
 74  		if (i == 0 && *cp++ == '=') {
 75  			*offset = p - environ;
 76  			return (cp);
 77  		}
 78  	}
 79  	return (NULL);
 80  }
 81  
 82  static os_unfair_lock __environ_lock_obj = OS_UNFAIR_LOCK_INIT;
 83  __private_extern__ void
 84  __environ_lock(void)
 85  {
 86  	os_unfair_lock_lock_with_options(
 87  			&__environ_lock_obj, OS_UNFAIR_LOCK_DATA_SYNCHRONIZATION);
 88  }
 89  __private_extern__ void
 90  __environ_unlock(void)
 91  {
 92  	os_unfair_lock_unlock(&__environ_lock_obj);
 93  }
 94  __private_extern__ void
 95  __environ_lock_fork_child(void)
 96  {
 97  	__environ_lock_obj = OS_UNFAIR_LOCK_INIT;
 98  }
 99  
100  /*
101   * _getenvp -- SPI using an arbitrary pointer to string array (the array must
102   * have been created with malloc) and an env state, created by _allocenvstate().
103   *	Returns ptr to value associated with name, if any, else NULL.
104   */
105  char *
106  _getenvp(const char *name, char ***envp, void *state __unused)
107  {
108  	// envp is passed as an argument, so the lock is not protecting everything
109  	int offset;
110  	__environ_lock();
111  	char *result = (__findenv_locked(name, &offset, *envp));
112  	__environ_unlock();
113  	return result;
114  }
115  
116  /*
117   * getenv --
118   *	Returns ptr to value associated with name, if any, else NULL.
119   */
120  char *
121  getenv(name)
122  	const char *name;
123  {
124  	int offset;
125  	__environ_lock();
126  	char *result = __findenv_locked(name, &offset, *_NSGetEnviron());
127  	__environ_unlock();
128  	return result;
129  }