1 //===-- interception.h ------------------------------------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file is a part of AddressSanitizer, an address sanity checker.
11 //
12 // Machinery for providing replacements/wrappers for system functions.
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef INTERCEPTION_H
16 #define INTERCEPTION_H
17 
18 #if !defined(__linux__) && !defined(__FreeBSD__) && \
19   !defined(__APPLE__) && !defined(_WIN32)
20 # error "Interception doesn't work on this operating system."
21 #endif
22 
23 #include "sanitizer_common/sanitizer_internal_defs.h"
24 
25 // These typedefs should be used only in the interceptor definitions to replace
26 // the standard system types (e.g. SSIZE_T instead of ssize_t)
27 typedef __sanitizer::uptr    SIZE_T;
28 typedef __sanitizer::sptr    SSIZE_T;
29 typedef __sanitizer::sptr    PTRDIFF_T;
30 typedef __sanitizer::s64     INTMAX_T;
31 typedef __sanitizer::OFF_T   OFF_T;
32 typedef __sanitizer::OFF64_T OFF64_T;
33 
34 // How to add an interceptor:
35 // Suppose you need to wrap/replace system function (generally, from libc):
36 //      int foo(const char *bar, double baz);
37 // You'll need to:
38 //      1) define INTERCEPTOR(int, foo, const char *bar, double baz) { ... } in
39 //         your source file. See the notes below for cases when
40 //         INTERCEPTOR_WITH_SUFFIX(...) should be used instead.
41 //      2) Call "INTERCEPT_FUNCTION(foo)" prior to the first call of "foo".
42 //         INTERCEPT_FUNCTION(foo) evaluates to "true" iff the function was
43 //         intercepted successfully.
44 // You can access original function by calling REAL(foo)(bar, baz).
45 // By default, REAL(foo) will be visible only inside your interceptor, and if
46 // you want to use it in other parts of RTL, you'll need to:
47 //      3a) add DECLARE_REAL(int, foo, const char*, double) to a
48 //          header file.
49 // However, if the call "INTERCEPT_FUNCTION(foo)" and definition for
50 // INTERCEPTOR(..., foo, ...) are in different files, you'll instead need to:
51 //      3b) add DECLARE_REAL_AND_INTERCEPTOR(int, foo, const char*, double)
52 //          to a header file.
53 
54 // Notes: 1. Things may not work properly if macro INTERCEPTOR(...) {...} or
55 //           DECLARE_REAL(...) are located inside namespaces.
56 //        2. On Mac you can also use: "OVERRIDE_FUNCTION(foo, zoo)" to
57 //           effectively redirect calls from "foo" to "zoo". In this case
58 //           you aren't required to implement
59 //           INTERCEPTOR(int, foo, const char *bar, double baz) {...}
60 //           but instead you'll have to add
61 //           DECLARE_REAL(int, foo, const char *bar, double baz) in your
62 //           source file (to define a pointer to overriden function).
63 //        3. Some Mac functions have symbol variants discriminated by
64 //           additional suffixes, e.g. _$UNIX2003 (see
65 //           https://developer.apple.com/library/mac/#releasenotes/Darwin/SymbolVariantsRelNotes/index.html
66 //           for more details). To intercept such functions you need to use the
67 //           INTERCEPTOR_WITH_SUFFIX(...) macro.
68 
69 // How it works:
70 // To replace system functions on Linux we just need to declare functions
71 // with same names in our library and then obtain the real function pointers
72 // using dlsym().
73 // There is one complication. A user may also intercept some of the functions
74 // we intercept. To resolve this we declare our interceptors with __interceptor_
75 // prefix, and then make actual interceptors weak aliases to __interceptor_
76 // functions.
77 //
78 // This is not so on Mac OS, where the two-level namespace makes
79 // our replacement functions invisible to other libraries. This may be overcomed
80 // using the DYLD_FORCE_FLAT_NAMESPACE, but some errors loading the shared
81 // libraries in Chromium were noticed when doing so.
82 // Instead we create a dylib containing a __DATA,__interpose section that
83 // associates library functions with their wrappers. When this dylib is
84 // preloaded before an executable using DYLD_INSERT_LIBRARIES, it routes all
85 // the calls to interposed functions done through stubs to the wrapper
86 // functions.
87 // As it's decided at compile time which functions are to be intercepted on Mac,
88 // INTERCEPT_FUNCTION() is effectively a no-op on this system.
89 
90 #if defined(__APPLE__)
91 #include <sys/cdefs.h>  // For __DARWIN_ALIAS_C().
92 
93 // Just a pair of pointers.
94 struct interpose_substitution {
95   const uptr replacement;
96   const uptr original;
97 };
98 
99 // For a function foo() create a global pair of pointers { wrap_foo, foo } in
100 // the __DATA,__interpose section.
101 // As a result all the calls to foo() will be routed to wrap_foo() at runtime.
102 #define INTERPOSER(func_name) __attribute__((used)) \
103 const interpose_substitution substitution_##func_name[] \
104     __attribute__((section("__DATA, __interpose"))) = { \
105     { reinterpret_cast<const uptr>(WRAP(func_name)), \
106       reinterpret_cast<const uptr>(func_name) } \
107 }
108 
109 // For a function foo() and a wrapper function bar() create a global pair
110 // of pointers { bar, foo } in the __DATA,__interpose section.
111 // As a result all the calls to foo() will be routed to bar() at runtime.
112 #define INTERPOSER_2(func_name, wrapper_name) __attribute__((used)) \
113 const interpose_substitution substitution_##func_name[] \
114     __attribute__((section("__DATA, __interpose"))) = { \
115     { reinterpret_cast<const uptr>(wrapper_name), \
116       reinterpret_cast<const uptr>(func_name) } \
117 }
118 
119 # define WRAP(x) wrap_##x
120 # define WRAPPER_NAME(x) "wrap_"#x
121 # define INTERCEPTOR_ATTRIBUTE
122 # define DECLARE_WRAPPER(ret_type, func, ...)
123 
124 #elif defined(_WIN32)
125 # define WRAP(x) __asan_wrap_##x
126 # define WRAPPER_NAME(x) "__asan_wrap_"#x
127 # define INTERCEPTOR_ATTRIBUTE __declspec(dllexport)
128 # define DECLARE_WRAPPER(ret_type, func, ...) \
129     extern "C" ret_type func(__VA_ARGS__);
130 # define DECLARE_WRAPPER_WINAPI(ret_type, func, ...) \
131     extern "C" __declspec(dllimport) ret_type __stdcall func(__VA_ARGS__);
132 #elif defined(__FreeBSD__)
133 # define WRAP(x) __interceptor_ ## x
134 # define WRAPPER_NAME(x) "__interceptor_" #x
135 # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default")))
136 // FreeBSD's dynamic linker (incompliantly) gives non-weak symbols higher
137 // priority than weak ones so weak aliases won't work for indirect calls
138 // in position-independent (-fPIC / -fPIE) mode.
139 # define DECLARE_WRAPPER(ret_type, func, ...) \
140      extern "C" ret_type func(__VA_ARGS__) \
141      __attribute__((alias("__interceptor_" #func), visibility("default")));
142 #else
143 # define WRAP(x) __interceptor_ ## x
144 # define WRAPPER_NAME(x) "__interceptor_" #x
145 # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default")))
146 # define DECLARE_WRAPPER(ret_type, func, ...) \
147     extern "C" ret_type func(__VA_ARGS__) \
148     __attribute__((weak, alias("__interceptor_" #func), visibility("default")));
149 #endif
150 
151 #if !defined(__APPLE__)
152 # define PTR_TO_REAL(x) real_##x
153 # define REAL(x) __interception::PTR_TO_REAL(x)
154 # define FUNC_TYPE(x) x##_f
155 
156 # define DECLARE_REAL(ret_type, func, ...) \
157     typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \
158     namespace __interception { \
159       extern FUNC_TYPE(func) PTR_TO_REAL(func); \
160     }
161 #else  // __APPLE__
162 # define REAL(x) x
163 # define DECLARE_REAL(ret_type, func, ...) \
164     extern "C" ret_type func(__VA_ARGS__);
165 #endif  // __APPLE__
166 
167 #define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) \
168   DECLARE_REAL(ret_type, func, __VA_ARGS__) \
169   extern "C" ret_type WRAP(func)(__VA_ARGS__);
170 
171 // Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR
172 // macros does its job. In exceptional cases you may need to call REAL(foo)
173 // without defining INTERCEPTOR(..., foo, ...). For example, if you override
174 // foo with an interceptor for other function.
175 #if !defined(__APPLE__)
176 # define DEFINE_REAL(ret_type, func, ...) \
177     typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \
178     namespace __interception { \
179       FUNC_TYPE(func) PTR_TO_REAL(func); \
180     }
181 #else
182 # define DEFINE_REAL(ret_type, func, ...)
183 #endif
184 
185 #if !defined(__APPLE__)
186 #define INTERCEPTOR(ret_type, func, ...) \
187   DEFINE_REAL(ret_type, func, __VA_ARGS__) \
188   DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \
189   extern "C" \
190   INTERCEPTOR_ATTRIBUTE \
191   ret_type WRAP(func)(__VA_ARGS__)
192 
193 // We don't need INTERCEPTOR_WITH_SUFFIX on non-Darwin for now.
194 #define INTERCEPTOR_WITH_SUFFIX(ret_type, func, ...) \
195   INTERCEPTOR(ret_type, func, __VA_ARGS__)
196 
197 #else  // __APPLE__
198 
199 #define INTERCEPTOR_ZZZ(suffix, ret_type, func, ...) \
200   extern "C" ret_type func(__VA_ARGS__) suffix; \
201   extern "C" ret_type WRAP(func)(__VA_ARGS__); \
202   INTERPOSER(func); \
203   extern "C" INTERCEPTOR_ATTRIBUTE ret_type WRAP(func)(__VA_ARGS__)
204 
205 #define INTERCEPTOR(ret_type, func, ...) \
206   INTERCEPTOR_ZZZ(/*no symbol variants*/, ret_type, func, __VA_ARGS__)
207 
208 #define INTERCEPTOR_WITH_SUFFIX(ret_type, func, ...) \
209   INTERCEPTOR_ZZZ(__DARWIN_ALIAS_C(func), ret_type, func, __VA_ARGS__)
210 
211 // Override |overridee| with |overrider|.
212 #define OVERRIDE_FUNCTION(overridee, overrider) \
213   INTERPOSER_2(overridee, WRAP(overrider))
214 #endif
215 
216 #if defined(_WIN32)
217 # define INTERCEPTOR_WINAPI(ret_type, func, ...) \
218     typedef ret_type (__stdcall *FUNC_TYPE(func))(__VA_ARGS__); \
219     namespace __interception { \
220       FUNC_TYPE(func) PTR_TO_REAL(func); \
221     } \
222     extern "C" \
223     INTERCEPTOR_ATTRIBUTE \
224     ret_type __stdcall WRAP(func)(__VA_ARGS__)
225 #endif
226 
227 // ISO C++ forbids casting between pointer-to-function and pointer-to-object,
228 // so we use casting via an integral type __interception::uptr,
229 // assuming that system is POSIX-compliant. Using other hacks seem
230 // challenging, as we don't even pass function type to
231 // INTERCEPT_FUNCTION macro, only its name.
232 namespace __interception {
233 #if defined(_WIN64)
234 typedef unsigned long long uptr;  // NOLINT
235 #else
236 typedef unsigned long uptr;  // NOLINT
237 #endif  // _WIN64
238 }  // namespace __interception
239 
240 #define INCLUDED_FROM_INTERCEPTION_LIB
241 
242 #if defined(__linux__) || defined(__FreeBSD__)
243 # include "interception_linux.h"
244 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_LINUX_OR_FREEBSD(func)
245 # define INTERCEPT_FUNCTION_VER(func, symver) \
246     INTERCEPT_FUNCTION_VER_LINUX_OR_FREEBSD(func, symver)
247 #elif defined(__APPLE__)
248 # include "interception_mac.h"
249 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_MAC(func)
250 # define INTERCEPT_FUNCTION_VER(func, symver) \
251     INTERCEPT_FUNCTION_VER_MAC(func, symver)
252 #else  // defined(_WIN32)
253 # include "interception_win.h"
254 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_WIN(func)
255 # define INTERCEPT_FUNCTION_VER(func, symver) \
256     INTERCEPT_FUNCTION_VER_WIN(func, symver)
257 #endif
258 
259 #undef INCLUDED_FROM_INTERCEPTION_LIB
260 
261 #endif  // INTERCEPTION_H
262