interception.h revision b46941a1d23012491a7a8a52718cacbde3c19ba1
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, 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, 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, func, ...) \ 110 extern "C" ret_type 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// Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR 135// macros does its job. In exceptional cases you may need to call REAL(foo) 136// without defining INTERCEPTOR(..., foo, ...). For example, if you override 137// foo with an interceptor for other function. 138#if !MAC_INTERPOSE_FUNCTIONS 139# define DEFINE_REAL(ret_type, func, ...) \ 140 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ 141 namespace __interception { \ 142 FUNC_TYPE(func) PTR_TO_REAL(func); \ 143 } 144#else 145# define DEFINE_REAL(ret_type, func, ...) 146#endif 147 148#define INTERCEPTOR(ret_type, func, ...) \ 149 DEFINE_REAL(ret_type, func, __VA_ARGS__) \ 150 DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \ 151 extern "C" \ 152 INTERCEPTOR_ATTRIBUTE \ 153 ret_type WRAP(func)(__VA_ARGS__) 154 155#if defined(_WIN32) 156# define INTERCEPTOR_WINAPI(ret_type, func, ...) \ 157 typedef ret_type (__stdcall *FUNC_TYPE(func))(__VA_ARGS__); \ 158 namespace __interception { \ 159 FUNC_TYPE(func) PTR_TO_REAL(func); \ 160 } \ 161 DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \ 162 extern "C" \ 163 INTERCEPTOR_ATTRIBUTE \ 164 ret_type __stdcall WRAP(func)(__VA_ARGS__) 165#endif 166 167// ISO C++ forbids casting between pointer-to-function and pointer-to-object, 168// so we use casting via an integral type __interception::uptr, 169// assuming that system is POSIX-compliant. Using other hacks seem 170// challenging, as we don't even pass function type to 171// INTERCEPT_FUNCTION macro, only its name. 172namespace __interception { 173#if defined(_WIN64) 174typedef unsigned long long uptr; // NOLINT 175#else 176typedef unsigned long uptr; // NOLINT 177#endif // _WIN64 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