1 //===-- interception.h ------------------------------------------*- C++ -*-===// 2 // 3 // This file is distributed under the University of Illinois Open Source 4 // License. See LICENSE.TXT for details. 5 // 6 //===----------------------------------------------------------------------===// 7 // 8 // This file is a part of AddressSanitizer, an address sanity checker. 9 // 10 // Machinery for providing replacements/wrappers for system functions. 11 //===----------------------------------------------------------------------===// 12 13 #ifndef INTERCEPTION_H 14 #define INTERCEPTION_H 15 16 #if !defined(__linux__) && !defined(__APPLE__) && !defined(_WIN32) 17 # error "Interception doesn't work on this operating system." 18 #endif 19 20 #include "sanitizer_common/sanitizer_internal_defs.h" 21 22 // These typedefs should be used only in the interceptor definitions to replace 23 // the standard system types (e.g. SSIZE_T instead of ssize_t) 24 typedef __sanitizer::uptr SIZE_T; 25 typedef __sanitizer::sptr SSIZE_T; 26 typedef __sanitizer::sptr PTRDIFF_T; 27 typedef __sanitizer::s64 INTMAX_T; 28 // WARNING: OFF_T may be different from OS type off_t, depending on the value of 29 // _FILE_OFFSET_BITS. This definition of OFF_T matches the ABI of system calls 30 // like pread and mmap, as opposed to pread64 and mmap64. 31 // Mac and Linux/x86-64 are special. 32 #if defined(__APPLE__) || (defined(__linux__) && defined(__x86_64__)) 33 typedef __sanitizer::u64 OFF_T; 34 #else 35 typedef __sanitizer::uptr OFF_T; 36 #endif 37 typedef __sanitizer::u64 OFF64_T; 38 39 // How to add an interceptor: 40 // Suppose you need to wrap/replace system function (generally, from libc): 41 // int foo(const char *bar, double baz); 42 // You'll need to: 43 // 1) define INTERCEPTOR(int, foo, const char *bar, double baz) { ... } in 44 // your source file. 45 // 2) Call "INTERCEPT_FUNCTION(foo)" prior to the first call of "foo". 46 // INTERCEPT_FUNCTION(foo) evaluates to "true" iff the function was 47 // intercepted successfully. 48 // You can access original function by calling REAL(foo)(bar, baz). 49 // By default, REAL(foo) will be visible only inside your interceptor, and if 50 // you want to use it in other parts of RTL, you'll need to: 51 // 3a) add DECLARE_REAL(int, foo, const char*, double) to a 52 // header file. 53 // However, if the call "INTERCEPT_FUNCTION(foo)" and definition for 54 // INTERCEPTOR(..., foo, ...) are in different files, you'll instead need to: 55 // 3b) add DECLARE_REAL_AND_INTERCEPTOR(int, foo, const char*, double) 56 // to a header file. 57 58 // Notes: 1. Things may not work properly if macro INTERCEPT(...) {...} or 59 // DECLARE_REAL(...) are located inside namespaces. 60 // 2. On Mac you can also use: "OVERRIDE_FUNCTION(foo, zoo);" to 61 // effectively redirect calls from "foo" to "zoo". In this case 62 // you aren't required to implement 63 // INTERCEPTOR(int, foo, const char *bar, double baz) {...} 64 // but instead you'll have to add 65 // DEFINE_REAL(int, foo, const char *bar, double baz) in your 66 // source file (to define a pointer to overriden function). 67 68 // How it works: 69 // To replace system functions on Linux we just need to declare functions 70 // with same names in our library and then obtain the real function pointers 71 // using dlsym(). 72 // There is one complication. A user may also intercept some of the functions 73 // we intercept. To resolve this we declare our interceptors with __interceptor_ 74 // prefix, and then make actual interceptors weak aliases to __interceptor_ 75 // functions. 76 // This is not so on Mac OS, where the two-level namespace makes 77 // our replacement functions invisible to other libraries. This may be overcomed 78 // using the DYLD_FORCE_FLAT_NAMESPACE, but some errors loading the shared 79 // libraries in Chromium were noticed when doing so. 80 // Instead we create a dylib containing a __DATA,__interpose section that 81 // associates library functions with their wrappers. When this dylib is 82 // preloaded before an executable using DYLD_INSERT_LIBRARIES, it routes all 83 // the calls to interposed functions done through stubs to the wrapper 84 // functions. 85 86 #if defined(__APPLE__) 87 # define WRAP(x) wrap_##x 88 # define WRAPPER_NAME(x) "wrap_"#x 89 # define INTERCEPTOR_ATTRIBUTE 90 # define DECLARE_WRAPPER(ret_type, func, ...) 91 #elif defined(_WIN32) 92 # if defined(_DLL) // DLL CRT 93 # define WRAP(x) x 94 # define WRAPPER_NAME(x) #x 95 # define INTERCEPTOR_ATTRIBUTE 96 # else // Static CRT 97 # define WRAP(x) wrap_##x 98 # define WRAPPER_NAME(x) "wrap_"#x 99 # define INTERCEPTOR_ATTRIBUTE 100 # endif 101 # define DECLARE_WRAPPER(ret_type, func, ...) 102 #else 103 # define WRAP(x) __interceptor_ ## x 104 # define WRAPPER_NAME(x) "__interceptor_" #x 105 # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default"))) 106 # define DECLARE_WRAPPER(ret_type, func, ...) \ 107 extern "C" ret_type func(__VA_ARGS__) \ 108 __attribute__((weak, alias("__interceptor_" #func), visibility("default"))); 109 #endif 110 111 #if !defined(__APPLE__) 112 # define PTR_TO_REAL(x) real_##x 113 # define REAL(x) __interception::PTR_TO_REAL(x) 114 # define FUNC_TYPE(x) x##_f 115 116 # define DECLARE_REAL(ret_type, func, ...) \ 117 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ 118 namespace __interception { \ 119 extern FUNC_TYPE(func) PTR_TO_REAL(func); \ 120 } 121 #else // __APPLE__ 122 # define REAL(x) x 123 # define DECLARE_REAL(ret_type, func, ...) \ 124 extern "C" ret_type func(__VA_ARGS__); 125 #endif // __APPLE__ 126 127 #define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) \ 128 DECLARE_REAL(ret_type, func, __VA_ARGS__) \ 129 extern "C" ret_type WRAP(func)(__VA_ARGS__); 130 131 // Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR 132 // macros does its job. In exceptional cases you may need to call REAL(foo) 133 // without defining INTERCEPTOR(..., foo, ...). For example, if you override 134 // foo with an interceptor for other function. 135 #if !defined(__APPLE__) 136 # define DEFINE_REAL(ret_type, func, ...) \ 137 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ 138 namespace __interception { \ 139 FUNC_TYPE(func) PTR_TO_REAL(func); \ 140 } 141 #else 142 # define DEFINE_REAL(ret_type, func, ...) 143 #endif 144 145 #define INTERCEPTOR(ret_type, func, ...) \ 146 DEFINE_REAL(ret_type, func, __VA_ARGS__) \ 147 DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \ 148 extern "C" \ 149 INTERCEPTOR_ATTRIBUTE \ 150 ret_type WRAP(func)(__VA_ARGS__) 151 152 #if defined(_WIN32) 153 # define INTERCEPTOR_WINAPI(ret_type, func, ...) \ 154 typedef ret_type (__stdcall *FUNC_TYPE(func))(__VA_ARGS__); \ 155 namespace __interception { \ 156 FUNC_TYPE(func) PTR_TO_REAL(func); \ 157 } \ 158 DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \ 159 extern "C" \ 160 INTERCEPTOR_ATTRIBUTE \ 161 ret_type __stdcall WRAP(func)(__VA_ARGS__) 162 #endif 163 164 // ISO C++ forbids casting between pointer-to-function and pointer-to-object, 165 // so we use casting via an integral type __interception::uptr, 166 // assuming that system is POSIX-compliant. Using other hacks seem 167 // challenging, as we don't even pass function type to 168 // INTERCEPT_FUNCTION macro, only its name. 169 namespace __interception { 170 #if defined(_WIN64) 171 typedef unsigned long long uptr; // NOLINT 172 #else 173 typedef unsigned long uptr; // NOLINT 174 #endif // _WIN64 175 } // namespace __interception 176 177 #define INCLUDED_FROM_INTERCEPTION_LIB 178 179 #if defined(__linux__) 180 # include "interception_linux.h" 181 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_LINUX(func) 182 #elif defined(__APPLE__) 183 # include "interception_mac.h" 184 # define OVERRIDE_FUNCTION(old_func, new_func) \ 185 OVERRIDE_FUNCTION_MAC(old_func, new_func) 186 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_MAC(func) 187 #else // defined(_WIN32) 188 # include "interception_win.h" 189 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_WIN(func) 190 #endif 191 192 #undef INCLUDED_FROM_INTERCEPTION_LIB 193 194 #endif // INTERCEPTION_H 195