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