xref: /illumos-gate/usr/src/lib/libc/port/gen/getauxv.c (revision 1da57d551424de5a9d469760be7c4b4d4f10a755)
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 #include "lint.h"
28 #include <libc.h>
29 #include <fcntl.h>
30 #include <stdlib.h>
31 #include <unistd.h>
32 #include <sys/types.h>
33 #include <sys/stat.h>
34 #include <sys/auxv.h>
35 #include <mtlib.h>
36 #include <thread.h>
37 #include <synch.h>
38 #include <atomic.h>
39 
40 static mutex_t auxlock = DEFAULTMUTEX;
41 
42 /*
43  * Get auxiliary entry.
44  * Returns pointer to entry, or 0 if entry does not exist.
45  */
46 static auxv_t *
_getaux(int type)47 _getaux(int type)
48 {
49 	static auxv_t *auxb = NULL;
50 	static size_t nauxv = 0;
51 	ssize_t i;
52 
53 	/*
54 	 * The first time through, read the initial aux vector that was
55 	 * passed to the process at exec(2).  Only do this once.
56 	 */
57 	if (auxb == NULL) {
58 		lmutex_lock(&auxlock);
59 		if (auxb == NULL) {
60 			struct stat statb;
61 			auxv_t *buf = NULL;
62 			int fd;
63 
64 			if ((fd = open("/proc/self/auxv", O_RDONLY)) != -1 &&
65 			    fstat(fd, &statb) != -1)
66 				buf = libc_malloc(
67 				    statb.st_size + sizeof (auxv_t));
68 
69 			if (buf != NULL) {
70 				i = read(fd, buf, statb.st_size);
71 				if (i != -1) {
72 					nauxv = i / sizeof (auxv_t);
73 					buf[nauxv].a_type = AT_NULL;
74 				} else {
75 					libc_free(buf);
76 					buf = NULL;
77 				}
78 			}
79 
80 			if (fd != -1)
81 				(void) close(fd);
82 
83 			membar_producer();
84 			auxb = buf;
85 		}
86 		lmutex_unlock(&auxlock);
87 	}
88 	membar_consumer();
89 
90 	/*
91 	 * Scan the auxiliary entries looking for the required type.
92 	 */
93 	for (i = 0; i < nauxv; i++)
94 		if (auxb[i].a_type == type)
95 			return (&auxb[i]);
96 
97 	/*
98 	 * No auxiliary array (static executable) or entry not found.
99 	 */
100 	return ((auxv_t *)0);
101 }
102 
103 /*
104  * These two routines are utilities exported to the rest of libc.
105  */
106 
107 long
___getauxval(int type)108 ___getauxval(int type)
109 {
110 	auxv_t *auxp;
111 
112 	if ((auxp = _getaux(type)) != (auxv_t *)0)
113 		return (auxp->a_un.a_val);
114 	return (0);
115 }
116 
117 void *
___getauxptr(int type)118 ___getauxptr(int type)
119 {
120 	auxv_t *auxp;
121 
122 	if ((auxp = _getaux(type)) != (auxv_t *)0)
123 		return (auxp->a_un.a_ptr);
124 	return (0);
125 }
126