1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 */
21
22 #include <apr_hash.h>
23
24 #include "svn_hash.h"
25 #include "svn_dso.h"
26 #include "svn_pools.h"
27 #include "svn_private_config.h"
28
29 #include "private/svn_mutex.h"
30 #include "private/svn_atomic.h"
31 #include "private/svn_subr_private.h"
32
33 /* A mutex to protect our global pool and cache. */
34 static svn_mutex__t *dso_mutex = NULL;
35
36 /* Global pool to allocate DSOs in. */
37 static apr_pool_t *dso_pool;
38
39 /* Global cache for storing DSO objects. */
40 static apr_hash_t *dso_cache;
41
42 /* Just an arbitrary location in memory... */
43 static int not_there_sentinel;
44
45 static volatile svn_atomic_t atomic_init_status = 0;
46
47 /* A specific value we store in the dso_cache to indicate that the
48 library wasn't found. This keeps us from allocating extra memory
49 from dso_pool when trying to find libraries we already know aren't
50 there. */
51 #define NOT_THERE ((void *) ¬_there_sentinel)
52
53 static svn_error_t *
atomic_init_func(void * baton,apr_pool_t * pool)54 atomic_init_func(void *baton,
55 apr_pool_t *pool)
56 {
57 dso_pool = svn_pool_create(NULL);
58
59 SVN_ERR(svn_mutex__init(&dso_mutex, TRUE, dso_pool));
60
61 dso_cache = apr_hash_make(dso_pool);
62 return SVN_NO_ERROR;
63 }
64
65 svn_error_t *
svn_dso_initialize2(void)66 svn_dso_initialize2(void)
67 {
68 SVN_ERR(svn_atomic__init_once(&atomic_init_status, atomic_init_func,
69 NULL, NULL));
70
71 return SVN_NO_ERROR;
72 }
73
74 #if APR_HAS_DSO
75 static svn_error_t *
svn_dso_load_internal(apr_dso_handle_t ** dso,const char * fname)76 svn_dso_load_internal(apr_dso_handle_t **dso, const char *fname)
77 {
78 *dso = svn_hash_gets(dso_cache, fname);
79
80 /* First check to see if we've been through this before... We do this
81 to avoid calling apr_dso_load multiple times for a given library,
82 which would result in wasting small amounts of memory each time. */
83 if (*dso == NOT_THERE)
84 {
85 *dso = NULL;
86 return SVN_NO_ERROR;
87 }
88
89 /* If we got nothing back from the cache, try and load the library. */
90 if (! *dso)
91 {
92 apr_status_t status = apr_dso_load(dso, fname, dso_pool);
93 if (status)
94 {
95 #ifdef SVN_DEBUG_DSO
96 char buf[1024];
97 fprintf(stderr,
98 "Dynamic loading of '%s' failed with the following error:\n%s\n",
99 fname,
100 apr_dso_error(*dso, buf, 1024));
101 #endif
102 *dso = NULL;
103
104 /* It wasn't found, so set the special "we didn't find it" value. */
105 svn_hash_sets(dso_cache, apr_pstrdup(dso_pool, fname), NOT_THERE);
106
107 return SVN_NO_ERROR;
108 }
109
110 /* Stash the dso so we can use it next time. */
111 svn_hash_sets(dso_cache, apr_pstrdup(dso_pool, fname), *dso);
112 }
113
114 return SVN_NO_ERROR;
115 }
116
117 svn_error_t *
svn_dso_load(apr_dso_handle_t ** dso,const char * fname)118 svn_dso_load(apr_dso_handle_t **dso, const char *fname)
119 {
120 SVN_ERR(svn_dso_initialize2());
121
122 SVN_MUTEX__WITH_LOCK(dso_mutex, svn_dso_load_internal(dso, fname));
123
124 return SVN_NO_ERROR;
125 }
126
127 apr_pool_t *
svn_dso__pool(void)128 svn_dso__pool(void)
129 {
130 return dso_pool;
131 }
132
133 #endif /* APR_HAS_DSO */
134