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 79 #if defined(__APPLE__) 80 # define WRAP(x) wrap_##x 81 # define WRAPPER_NAME(x) "wrap_"#x 82 # define INTERCEPTOR_ATTRIBUTE 83 # define DECLARE_WRAPPER(ret_type, convention, func, ...) 84 #elif defined(_WIN32) 85 # if defined(_DLL) // DLL CRT 86 # define WRAP(x) x 87 # define WRAPPER_NAME(x) #x 88 # define INTERCEPTOR_ATTRIBUTE 89 # else // Static CRT 90 # define WRAP(x) wrap_##x 91 # define WRAPPER_NAME(x) "wrap_"#x 92 # define INTERCEPTOR_ATTRIBUTE 93 # endif 94 # define DECLARE_WRAPPER(ret_type, convention, func, ...) 95 #else 96 # define WRAP(x) __interceptor_ ## x 97 # define WRAPPER_NAME(x) "__interceptor_" #x 98 # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default"))) 99 # define DECLARE_WRAPPER(ret_type, convention, func, ...) \ 100 extern "C" ret_type convention func(__VA_ARGS__) \ 101 __attribute__((weak, alias("__interceptor_" #func), visibility("default"))); 102 #endif 103 104 #define PTR_TO_REAL(x) real_##x 105 #define REAL(x) __interception::PTR_TO_REAL(x) 106 #define FUNC_TYPE(x) x##_f 107 108 #define DECLARE_REAL(ret_type, func, ...) \ 109 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ 110 namespace __interception { \ 111 extern FUNC_TYPE(func) PTR_TO_REAL(func); \ 112 } 113 114 #define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) \ 115 DECLARE_REAL(ret_type, func, ##__VA_ARGS__) \ 116 extern "C" ret_type WRAP(func)(__VA_ARGS__); 117 118 // FIXME(timurrrr): We might need to add DECLARE_REAL_EX etc to support 119 // different calling conventions later. 120 121 #define DEFINE_REAL_EX(ret_type, convention, func, ...) \ 122 typedef ret_type (convention *FUNC_TYPE(func))(__VA_ARGS__); \ 123 namespace __interception { \ 124 FUNC_TYPE(func) PTR_TO_REAL(func); \ 125 } 126 127 // Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR 128 // macros does its job. In exceptional cases you may need to call REAL(foo) 129 // without defining INTERCEPTOR(..., foo, ...). For example, if you override 130 // foo with an interceptor for other function. 131 #define DEFAULT_CONVENTION 132 133 #define DEFINE_REAL(ret_type, func, ...) \ 134 DEFINE_REAL_EX(ret_type, DEFAULT_CONVENTION, func, __VA_ARGS__) 135 136 #define INTERCEPTOR_EX(ret_type, convention, func, ...) \ 137 DEFINE_REAL_EX(ret_type, convention, func, __VA_ARGS__) \ 138 DECLARE_WRAPPER(ret_type, convention, func, __VA_ARGS__) \ 139 extern "C" \ 140 INTERCEPTOR_ATTRIBUTE \ 141 ret_type convention WRAP(func)(__VA_ARGS__) 142 143 #define INTERCEPTOR(ret_type, func, ...) \ 144 INTERCEPTOR_EX(ret_type, DEFAULT_CONVENTION, func, __VA_ARGS__) 145 146 #if defined(_WIN32) 147 # define INTERCEPTOR_WINAPI(ret_type, func, ...) \ 148 INTERCEPTOR_EX(ret_type, __stdcall, func, __VA_ARGS__) 149 #endif 150 151 // ISO C++ forbids casting between pointer-to-function and pointer-to-object, 152 // so we use casting via an integral type __interception::uptr, 153 // assuming that system is POSIX-compliant. Using other hacks seem 154 // challenging, as we don't even pass function type to 155 // INTERCEPT_FUNCTION macro, only its name. 156 namespace __interception { 157 typedef unsigned long uptr; // NOLINT 158 } // namespace __interception 159 160 #define INCLUDED_FROM_INTERCEPTION_LIB 161 162 #if defined(__linux__) 163 # include "interception_linux.h" 164 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_LINUX(func) 165 #elif defined(__APPLE__) 166 # include "interception_mac.h" 167 # define OVERRIDE_FUNCTION(old_func, new_func) \ 168 OVERRIDE_FUNCTION_MAC(old_func, new_func) 169 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_MAC(func) 170 #else // defined(_WIN32) 171 # include "interception_win.h" 172 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_WIN(func) 173 #endif 174 175 #undef INCLUDED_FROM_INTERCEPTION_LIB 176 177 #endif // INTERCEPTION_H 178