1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 * 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 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 /* This file contains dummy references to libgcc.a functions to force the
30 * dynamic linker to copy their definition into the final libc.so binary.
31 *
32 * They are required to ensure backwards binary compatibility with
33 * Android 1.5, 1.6 and even 3.0 system images. Some applications built
34 * using the NDK require them to be here.
35 *
36 * Now, for a more elaborate description of the issue:
37 *
38 * libgcc.a is a compiler-specific library containing various helper
39 * functions used to implement certain operations that are not necessarily
40 * supported by the target CPU. For example, integer division doesn't have a
41 * corresponding CPU instruction on ARMv5, and is instead implemented in the
42 * compiler-generated machine code as a call to an __idiv helper function.
43 *
44 * Normally, one has to place libgcc.a in the link command used to generate
45 * target binaries (shared libraries and executables) after all objects and
46 * static libraries, but before dependent shared libraries, i.e. something
47 * like:
48 * gcc <options> -o libfoo.so foo.a libgcc.a -lc -lm
49 *
50 * This ensures that any helper function needed by the code in foo.a is copied
51 * into the final libfoo.so. Unfortunately, the Android build system has been
52 * using this instead:
53 *
54 * gcc <options> -o libfoo.so foo.a -lc -lm libgcc.a
55 *
56 * The problem with this is that if one helper function needed by foo.a has
57 * already been copied into libc.so or libm.so, then nothing will be copied
58 * into libfoo.so. Instead, a symbol import definition will be added to it
59 * so libfoo.so can directly call the one in libc.so at runtime.
60 *
61 * When changing toolchains for 2.0, the set of helper functions copied to
62 * libc.so changed, which resulted in some native shared libraries generated
63 * with the NDK to fail to load properly.
64 *
65 * The NDK has been fixed after 1.6_r1 to use the correct link command, so
66 * any native shared library generated with it should now be safe from that
67 * problem. On the other hand, existing shared libraries distributed with
68 * applications that were generated with a previous version of the NDK
69 * still need all 1.5/1.6 helper functions in libc.so and libn.so
70 *
71 * After 3.2, the toolchain was updated again, adding __aeabi_f2uiz to the
72 * list of requirements. Technically, this is due to mis-linked NDK libraries
73 * but it is easier to add a single function here than asking several app
74 * developers to fix their build.
75 *
76 * Final note: some of the functions below should really be in libm.so to
77 * completely reflect the state of 1.5/1.6 system images. However,
78 * since libm.so depends on libc.so, it's easier to put all of
79 * these in libc.so instead, since the dynamic linker will always
80 * search in libc.so before libm.so for dependencies.
81 */
82
83 #define COMPAT_FUNCTIONS_LIST \
84 XX(__adddf3) \
85 XX(__addsf3) \
86 XX(__aeabi_cdcmpeq) \
87 XX(__aeabi_cdcmple) \
88 XX(__aeabi_cdrcmple) \
89 XX(__aeabi_d2f) \
90 XX(__aeabi_d2iz) \
91 XX(__aeabi_dadd) \
92 XX(__aeabi_dcmpeq) \
93 XX(__aeabi_dcmpge) \
94 XX(__aeabi_dcmpgt) \
95 XX(__aeabi_dcmple) \
96 XX(__aeabi_dcmplt) \
97 XX(__aeabi_dcmpun) \
98 XX(__aeabi_ddiv) \
99 XX(__aeabi_dmul) \
100 XX(__aeabi_drsub) \
101 XX(__aeabi_dsub) \
102 XX(__aeabi_f2d) \
103 XX(__aeabi_f2iz) \
104 XX(__aeabi_f2uiz) \
105 XX(__aeabi_fadd) \
106 XX(__aeabi_fcmpun) \
107 XX(__aeabi_fdiv) \
108 XX(__aeabi_fmul) \
109 XX(__aeabi_frsub) \
110 XX(__aeabi_fsub) \
111 XX(__aeabi_i2d) \
112 XX(__aeabi_i2f) \
113 XX(__aeabi_l2d) \
114 XX(__aeabi_l2f) \
115 XX(__aeabi_lmul) \
116 XX(__aeabi_ui2d) \
117 XX(__aeabi_ui2f) \
118 XX(__aeabi_ul2d) \
119 XX(__aeabi_ul2f) \
120 XX(__cmpdf2) \
121 XX(__divdf3) \
122 XX(__divsf3) \
123 XX(__eqdf2) \
124 XX(__extendsfdf2) \
125 XX(__fixdfsi) \
126 XX(__fixsfsi) \
127 XX(__floatdidf) \
128 XX(__floatdisf) \
129 XX(__floatsidf) \
130 XX(__floatsisf) \
131 XX(__floatundidf) \
132 XX(__floatundisf) \
133 XX(__floatunsidf) \
134 XX(__floatunsisf) \
135 XX(__gedf2) \
136 XX(__gtdf2) \
137 XX(__ledf2) \
138 XX(__ltdf2) \
139 XX(__muldf3) \
140 XX(__muldi3) \
141 XX(__mulsf3) \
142 XX(__nedf2) \
143 XX(__subdf3) \
144 XX(__subsf3) \
145 XX(__truncdfsf2) \
146 XX(__unorddf2) \
147 XX(__unordsf2) \
148
149 #define XX(f) extern void f(void);
150 COMPAT_FUNCTIONS_LIST
151 #undef XX
152
__bionic_libgcc_compat_hooks(void)153 void __bionic_libgcc_compat_hooks(void)
154 {
155 #define XX(f) f();
156 COMPAT_FUNCTIONS_LIST
157 #undef XX
158 }
159