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(__APPLE__) && !defined(_WIN32) 19 # error "Interception doesn't work on this operating system." 20 #endif 21 22 #include "sanitizer/common_interface_defs.h" 23 24 // These typedefs should be used only in the interceptor definitions to replace 25 // the standard system types (e.g. SSIZE_T instead of ssize_t) 26 typedef __sanitizer::uptr SIZE_T; 27 typedef __sanitizer::sptr SSIZE_T; 28 typedef __sanitizer::u64 OFF_T; 29 typedef __sanitizer::u64 OFF64_T; 30 31 // How to use this library: 32 // 1) Include this header to define your own interceptors 33 // (see details below). 34 // 2) Build all *.cc files and link against them. 35 // On Mac you will also need to: 36 // 3) Provide your own implementation for the following functions: 37 // mach_error_t __interception::allocate_island(void **ptr, 38 // size_t size, 39 // void *hint); 40 // mach_error_t __interception::deallocate_island(void *ptr); 41 // See "interception_mac.h" for more details. 42 43 // How to add an interceptor: 44 // Suppose you need to wrap/replace system function (generally, from libc): 45 // int foo(const char *bar, double baz); 46 // You'll need to: 47 // 1) define INTERCEPTOR(int, foo, const char *bar, double baz) { ... } in 48 // your source file. 49 // 2) Call "INTERCEPT_FUNCTION(foo)" prior to the first call of "foo". 50 // INTERCEPT_FUNCTION(foo) evaluates to "true" iff the function was 51 // intercepted successfully. 52 // You can access original function by calling REAL(foo)(bar, baz). 53 // By default, REAL(foo) will be visible only inside your interceptor, and if 54 // you want to use it in other parts of RTL, you'll need to: 55 // 3a) add DECLARE_REAL(int, foo, const char*, double) to a 56 // header file. 57 // However, if the call "INTERCEPT_FUNCTION(foo)" and definition for 58 // INTERCEPTOR(..., foo, ...) are in different files, you'll instead need to: 59 // 3b) add DECLARE_REAL_AND_INTERCEPTOR(int, foo, const char*, double) 60 // to a header file. 61 62 // Notes: 1. Things may not work properly if macro INTERCEPT(...) {...} or 63 // DECLARE_REAL(...) are located inside namespaces. 64 // 2. On Mac you can also use: "OVERRIDE_FUNCTION(foo, zoo);" to 65 // effectively redirect calls from "foo" to "zoo". In this case 66 // you aren't required to implement 67 // INTERCEPTOR(int, foo, const char *bar, double baz) {...} 68 // but instead you'll have to add 69 // DEFINE_REAL(int, foo, const char *bar, double baz) in your 70 // source file (to define a pointer to overriden function). 71 72 // How it works: 73 // To replace system functions on Linux we just need to declare functions 74 // with same names in our library and then obtain the real function pointers 75 // using dlsym(). 76 // There is one complication. A user may also intercept some of the functions 77 // we intercept. To resolve this we declare our interceptors with __interceptor_ 78 // prefix, and then make actual interceptors weak aliases to __interceptor_ 79 // functions. 80 // This is not so on Mac OS, where the two-level namespace makes 81 // our replacement functions invisible to other libraries. This may be overcomed 82 // using the DYLD_FORCE_FLAT_NAMESPACE, but some errors loading the shared 83 // libraries in Chromium were noticed when doing so. Instead we use 84 // mach_override, a handy framework for patching functions at runtime. 85 // To avoid possible name clashes, our replacement functions have 86 // the "wrap_" prefix on Mac. 87 // An alternative to function patching is to create a dylib containing a 88 // __DATA,__interpose section that associates library functions with their 89 // wrappers. When this dylib is preloaded before an executable using 90 // DYLD_INSERT_LIBRARIES, it routes all the calls to interposed functions done 91 // through stubs to the wrapper functions. Such a library is built with 92 // -DMAC_INTERPOSE_FUNCTIONS=1. 93 94 #if !defined(MAC_INTERPOSE_FUNCTIONS) || !defined(__APPLE__) 95 # define MAC_INTERPOSE_FUNCTIONS 0 96 #endif 97 98 #if defined(__APPLE__) 99 # define WRAP(x) wrap_##x 100 # define WRAPPER_NAME(x) "wrap_"#x 101 # define INTERCEPTOR_ATTRIBUTE 102 # define DECLARE_WRAPPER(ret_type, func, ...) 103 #elif defined(_WIN32) 104 # if defined(_DLL) // DLL CRT 105 # define WRAP(x) x 106 # define WRAPPER_NAME(x) #x 107 # define INTERCEPTOR_ATTRIBUTE 108 # else // Static CRT 109 # define WRAP(x) wrap_##x 110 # define WRAPPER_NAME(x) "wrap_"#x 111 # define INTERCEPTOR_ATTRIBUTE 112 # endif 113 # define DECLARE_WRAPPER(ret_type, func, ...) 114 #else 115 # define WRAP(x) __interceptor_ ## x 116 # define WRAPPER_NAME(x) "__interceptor_" #x 117 # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default"))) 118 # define DECLARE_WRAPPER(ret_type, func, ...) \ 119 extern "C" ret_type func(__VA_ARGS__) \ 120 __attribute__((weak, alias("__interceptor_" #func), visibility("default"))); 121 #endif 122 123 #if !MAC_INTERPOSE_FUNCTIONS 124 # define PTR_TO_REAL(x) real_##x 125 # define REAL(x) __interception::PTR_TO_REAL(x) 126 # define FUNC_TYPE(x) x##_f 127 128 # define DECLARE_REAL(ret_type, func, ...) \ 129 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ 130 namespace __interception { \ 131 extern FUNC_TYPE(func) PTR_TO_REAL(func); \ 132 } 133 #else // MAC_INTERPOSE_FUNCTIONS 134 # define REAL(x) x 135 # define DECLARE_REAL(ret_type, func, ...) \ 136 extern "C" ret_type func(__VA_ARGS__); 137 #endif // MAC_INTERPOSE_FUNCTIONS 138 139 #define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) \ 140 DECLARE_REAL(ret_type, func, __VA_ARGS__) \ 141 extern "C" ret_type WRAP(func)(__VA_ARGS__); 142 143 // Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR 144 // macros does its job. In exceptional cases you may need to call REAL(foo) 145 // without defining INTERCEPTOR(..., foo, ...). For example, if you override 146 // foo with an interceptor for other function. 147 #if !MAC_INTERPOSE_FUNCTIONS 148 # define DEFINE_REAL(ret_type, func, ...) \ 149 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ 150 namespace __interception { \ 151 FUNC_TYPE(func) PTR_TO_REAL(func); \ 152 } 153 #else 154 # define DEFINE_REAL(ret_type, func, ...) 155 #endif 156 157 #define INTERCEPTOR(ret_type, func, ...) \ 158 DEFINE_REAL(ret_type, func, __VA_ARGS__) \ 159 DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \ 160 extern "C" \ 161 INTERCEPTOR_ATTRIBUTE \ 162 ret_type WRAP(func)(__VA_ARGS__) 163 164 #if defined(_WIN32) 165 # define INTERCEPTOR_WINAPI(ret_type, func, ...) \ 166 typedef ret_type (__stdcall *FUNC_TYPE(func))(__VA_ARGS__); \ 167 namespace __interception { \ 168 FUNC_TYPE(func) PTR_TO_REAL(func); \ 169 } \ 170 DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \ 171 extern "C" \ 172 INTERCEPTOR_ATTRIBUTE \ 173 ret_type __stdcall WRAP(func)(__VA_ARGS__) 174 #endif 175 176 // ISO C++ forbids casting between pointer-to-function and pointer-to-object, 177 // so we use casting via an integral type __interception::uptr, 178 // assuming that system is POSIX-compliant. Using other hacks seem 179 // challenging, as we don't even pass function type to 180 // INTERCEPT_FUNCTION macro, only its name. 181 namespace __interception { 182 #if defined(_WIN64) 183 typedef unsigned long long uptr; // NOLINT 184 #else 185 typedef unsigned long uptr; // NOLINT 186 #endif // _WIN64 187 } // namespace __interception 188 189 #define INCLUDED_FROM_INTERCEPTION_LIB 190 191 #if defined(__linux__) 192 # include "interception_linux.h" 193 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_LINUX(func) 194 #elif defined(__APPLE__) 195 # include "interception_mac.h" 196 # define OVERRIDE_FUNCTION(old_func, new_func) \ 197 OVERRIDE_FUNCTION_MAC(old_func, new_func) 198 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_MAC(func) 199 #else // defined(_WIN32) 200 # include "interception_win.h" 201 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_WIN(func) 202 #endif 203 204 #undef INCLUDED_FROM_INTERCEPTION_LIB 205 206 #endif // INTERCEPTION_H 207