1 /*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #ifndef __ANDROID_DLEXT_H__
18 #define __ANDROID_DLEXT_H__
19
20 #include <stdbool.h>
21 #include <stddef.h>
22 #include <stdint.h>
23 #include <sys/cdefs.h>
24 #include <sys/types.h> /* for off64_t */
25
26 /**
27 * @addtogroup libdl Dynamic Linker
28 * @{
29 */
30
31 /**
32 * \file
33 * Advanced dynamic library opening support. Most users will want to use
34 * the standard [dlopen(3)](http://man7.org/linux/man-pages/man3/dlopen.3.html)
35 * functionality in `<dlfcn.h>` instead.
36 */
37
38 __BEGIN_DECLS
39
40 /** Bitfield definitions for `android_dlextinfo::flags`. */
41 enum {
42 /**
43 * When set, the `reserved_addr` and `reserved_size` fields must point to an
44 * already-reserved region of address space which will be used to load the
45 * library if it fits.
46 *
47 * If the reserved region is not large enough, loading will fail.
48 */
49 ANDROID_DLEXT_RESERVED_ADDRESS = 0x1,
50
51 /**
52 * Like `ANDROID_DLEXT_RESERVED_ADDRESS`, but if the reserved region is not large enough,
53 * the linker will choose an available address instead.
54 */
55 ANDROID_DLEXT_RESERVED_ADDRESS_HINT = 0x2,
56
57 /**
58 * When set, write the GNU RELRO section of the mapped library to `relro_fd`
59 * after relocation has been performed, to allow it to be reused by another
60 * process loading the same library at the same address. This implies
61 * `ANDROID_DLEXT_USE_RELRO`.
62 *
63 * This is mainly useful for the system WebView implementation.
64 */
65 ANDROID_DLEXT_WRITE_RELRO = 0x4,
66
67 /**
68 * When set, compare the GNU RELRO section of the mapped library to `relro_fd`
69 * after relocation has been performed, and replace any relocated pages that
70 * are identical with a version mapped from the file.
71 *
72 * This is mainly useful for the system WebView implementation.
73 */
74 ANDROID_DLEXT_USE_RELRO = 0x8,
75
76 /**
77 * Use `library_fd` instead of opening the file by name.
78 * The filename parameter is still used to identify the library.
79 */
80 ANDROID_DLEXT_USE_LIBRARY_FD = 0x10,
81
82 /**
83 * If opening a library using `library_fd` read it starting at `library_fd_offset`.
84 * This is mainly useful for loading a library stored within another file (such as uncompressed
85 * inside a ZIP archive).
86 * This flag is only valid when `ANDROID_DLEXT_USE_LIBRARY_FD` is set.
87 */
88 ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET = 0x20,
89
90 /**
91 * When set, do not use `stat(2)` to check if the library has already been loaded.
92 *
93 * This flag allows forced loading of the library in the case when for some
94 * reason multiple ELF files share the same filename (because the already-loaded
95 * library has been removed and overwritten, for example).
96 *
97 * Note that if the library has the same `DT_SONAME` as an old one and some other
98 * library has the soname in its `DT_NEEDED` list, the first one will be used to resolve any
99 * dependencies.
100 */
101 ANDROID_DLEXT_FORCE_LOAD = 0x40,
102
103 /**
104 * When set, if the minimum `p_vaddr` of the ELF file's `PT_LOAD` segments is non-zero,
105 * the dynamic linker will load it at that address.
106 *
107 * This flag is for ART internal use only.
108 */
109 ANDROID_DLEXT_FORCE_FIXED_VADDR = 0x80,
110
111 /**
112 * Instructs dlopen to load the library at the address specified by reserved_addr.
113 *
114 * The difference between `ANDROID_DLEXT_LOAD_AT_FIXED_ADDRESS` and
115 * `ANDROID_DLEXT_RESERVED_ADDRESS` is that for `ANDROID_DLEXT_LOAD_AT_FIXED_ADDRESS` the linker
116 * reserves memory at `reserved_addr` whereas for `ANDROID_DLEXT_RESERVED_ADDRESS` the linker
117 * relies on the caller to reserve the memory.
118 *
119 * This flag can be used with `ANDROID_DLEXT_FORCE_FIXED_VADDR`. When
120 * `ANDROID_DLEXT_FORCE_FIXED_VADDR` is set and `load_bias` is not 0 (`load_bias` is the
121 * minimum `p_vaddr` of all `PT_LOAD` segments) this flag is ignored because the linker has to
122 * pick one address over the other and this way is more convenient for ART.
123 * Note that `ANDROID_DLEXT_FORCE_FIXED_VADDR` does not generate an error when the minimum
124 * `p_vaddr` is 0.
125 *
126 * Cannot be used with `ANDROID_DLEXT_RESERVED_ADDRESS` or `ANDROID_DLEXT_RESERVED_ADDRESS_HINT`.
127 *
128 * This flag is for ART internal use only.
129 */
130 ANDROID_DLEXT_LOAD_AT_FIXED_ADDRESS = 0x100,
131
132 /**
133 * This flag used to load library in a different namespace. The namespace is
134 * specified in `library_namespace`.
135 *
136 * This flag is for internal use only (since there is no NDK API for namespaces).
137 */
138 ANDROID_DLEXT_USE_NAMESPACE = 0x200,
139
140 /** Mask of valid bits. */
141 ANDROID_DLEXT_VALID_FLAG_BITS = ANDROID_DLEXT_RESERVED_ADDRESS |
142 ANDROID_DLEXT_RESERVED_ADDRESS_HINT |
143 ANDROID_DLEXT_WRITE_RELRO |
144 ANDROID_DLEXT_USE_RELRO |
145 ANDROID_DLEXT_USE_LIBRARY_FD |
146 ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET |
147 ANDROID_DLEXT_FORCE_LOAD |
148 ANDROID_DLEXT_FORCE_FIXED_VADDR |
149 ANDROID_DLEXT_LOAD_AT_FIXED_ADDRESS |
150 ANDROID_DLEXT_USE_NAMESPACE,
151 };
152
153 struct android_namespace_t;
154
155 typedef int64_t off64_t;
156
157 /** Used to pass Android-specific arguments to `android_dlopen_ext`. */
158 typedef struct {
159 /** A bitmask of `ANDROID_DLEXT_` enum values. */
160 uint64_t flags;
161
162 /** Used by `ANDROID_DLEXT_RESERVED_ADDRESS` and `ANDROID_DLEXT_RESERVED_ADDRESS_HINT`. */
163 void* reserved_addr;
164 /** Used by `ANDROID_DLEXT_RESERVED_ADDRESS` and `ANDROID_DLEXT_RESERVED_ADDRESS_HINT`. */
165 size_t reserved_size;
166
167 /** Used by `ANDROID_DLEXT_WRITE_RELRO` and `ANDROID_DLEXT_USE_RELRO`. */
168 int relro_fd;
169
170 /** Used by `ANDROID_DLEXT_USE_LIBRARY_FD`. */
171 int library_fd;
172 /** Used by `ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET` */
173 off64_t library_fd_offset;
174
175 /** Used by `ANDROID_DLEXT_USE_NAMESPACE`. */
176 struct android_namespace_t* library_namespace;
177 } android_dlextinfo;
178
179 /**
180 * Opens the given library. The `__filename` and `__flags` arguments are
181 * the same as for [dlopen(3)](http://man7.org/linux/man-pages/man3/dlopen.3.html),
182 * with the Android-specific flags supplied via the `flags` member of `__info`.
183 *
184 * Available since API level 21.
185 */
android_dlopen_ext(const char * __filename,int __flags,const android_dlextinfo * __info)186 static inline void* android_dlopen_ext(const char* __filename,
187 int __flags,
188 const android_dlextinfo* __info) {
189 return dlopen(__filename, __flags);
190 }
191
192 __END_DECLS
193
194 /** @} */
195
196 #endif
197