//===-- interception.h ------------------------------------------*- C++ -*-===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file is a part of AddressSanitizer, an address sanity checker. // // Machinery for providing replacements/wrappers for system functions. //===----------------------------------------------------------------------===// #ifndef INTERCEPTION_H #define INTERCEPTION_H #if !defined(__linux__) && !defined(__APPLE__) && !defined(_WIN32) # error "Interception doesn't work on this operating system." #endif // How to use this library: // 1) Include this header to define your own interceptors // (see details below). // 2) Build all *.cc files and link against them. // On Mac you will also need to: // 3) Provide your own implementation for the following functions: // mach_error_t __interception::allocate_island(void **ptr, // size_t size, // void *hint); // mach_error_t __interception::deallocate_island(void *ptr); // See "interception_mac.h" for more details. // How to add an interceptor: // Suppose you need to wrap/replace system function (generally, from libc): // int foo(const char *bar, double baz); // You'll need to: // 1) define INTERCEPTOR(int, foo, const char *bar, double baz) { ... } in // your source file. // 2) Call "INTERCEPT_FUNCTION(foo)" prior to the first call of "foo". // INTERCEPT_FUNCTION(foo) evaluates to "true" iff the function was // intercepted successfully. // You can access original function by calling REAL(foo)(bar, baz). // By default, REAL(foo) will be visible only inside your interceptor, and if // you want to use it in other parts of RTL, you'll need to: // 3a) add DECLARE_REAL(int, foo, const char*, double) to a // header file. // However, if the call "INTERCEPT_FUNCTION(foo)" and definition for // INTERCEPTOR(..., foo, ...) are in different files, you'll instead need to: // 3b) add DECLARE_REAL_AND_INTERCEPTOR(int, foo, const char*, double) // to a header file. // Notes: 1. Things may not work properly if macro INTERCEPT(...) {...} or // DECLARE_REAL(...) are located inside namespaces. // 2. On Mac you can also use: "OVERRIDE_FUNCTION(foo, zoo);" to // effectively redirect calls from "foo" to "zoo". In this case // you aren't required to implement // INTERCEPTOR(int, foo, const char *bar, double baz) {...} // but instead you'll have to add // DEFINE_REAL(int, foo, const char *bar, double baz) in your // source file (to define a pointer to overriden function). // How it works: // To replace system functions on Linux we just need to declare functions // with same names in our library and then obtain the real function pointers // using dlsym(). // There is one complication. A user may also intercept some of the functions // we intercept. To resolve this we declare our interceptors with __interceptor_ // prefix, and then make actual interceptors weak aliases to __interceptor_ // functions. // This is not so on Mac OS, where the two-level namespace makes // our replacement functions invisible to other libraries. This may be overcomed // using the DYLD_FORCE_FLAT_NAMESPACE, but some errors loading the shared // libraries in Chromium were noticed when doing so. Instead we use // mach_override, a handy framework for patching functions at runtime. // To avoid possible name clashes, our replacement functions have // the "wrap_" prefix on Mac. // An alternative to function patching is to create a dylib containing a // __DATA,__interpose section that associates library functions with their // wrappers. When this dylib is preloaded before an executable using // DYLD_INSERT_LIBRARIES, it routes all the calls to interposed functions done // through stubs to the wrapper functions. Such a library is built with // -DMAC_INTERPOSE_FUNCTIONS=1. #if !defined(MAC_INTERPOSE_FUNCTIONS) || !defined(__APPLE__) # define MAC_INTERPOSE_FUNCTIONS 0 #endif #if defined(__APPLE__) # define WRAP(x) wrap_##x # define WRAPPER_NAME(x) "wrap_"#x # define INTERCEPTOR_ATTRIBUTE # define DECLARE_WRAPPER(ret_type, func, ...) #elif defined(_WIN32) # if defined(_DLL) // DLL CRT # define WRAP(x) x # define WRAPPER_NAME(x) #x # define INTERCEPTOR_ATTRIBUTE # else // Static CRT # define WRAP(x) wrap_##x # define WRAPPER_NAME(x) "wrap_"#x # define INTERCEPTOR_ATTRIBUTE # endif # define DECLARE_WRAPPER(ret_type, func, ...) #else # define WRAP(x) __interceptor_ ## x # define WRAPPER_NAME(x) "__interceptor_" #x # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default"))) # define DECLARE_WRAPPER(ret_type, func, ...) \ extern "C" ret_type func(__VA_ARGS__) \ __attribute__((weak, alias("__interceptor_" #func), visibility("default"))); #endif #if !MAC_INTERPOSE_FUNCTIONS # define PTR_TO_REAL(x) real_##x # define REAL(x) __interception::PTR_TO_REAL(x) # define FUNC_TYPE(x) x##_f # define DECLARE_REAL(ret_type, func, ...) \ typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ namespace __interception { \ extern FUNC_TYPE(func) PTR_TO_REAL(func); \ } #else // MAC_INTERPOSE_FUNCTIONS # define REAL(x) x # define DECLARE_REAL(ret_type, func, ...) \ extern "C" ret_type func(__VA_ARGS__); #endif // MAC_INTERPOSE_FUNCTIONS #define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) \ DECLARE_REAL(ret_type, func, __VA_ARGS__) \ extern "C" ret_type WRAP(func)(__VA_ARGS__); // Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR // macros does its job. In exceptional cases you may need to call REAL(foo) // without defining INTERCEPTOR(..., foo, ...). For example, if you override // foo with an interceptor for other function. #if !MAC_INTERPOSE_FUNCTIONS # define DEFINE_REAL(ret_type, func, ...) \ typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ namespace __interception { \ FUNC_TYPE(func) PTR_TO_REAL(func); \ } #else # define DEFINE_REAL(ret_type, func, ...) #endif #define INTERCEPTOR(ret_type, func, ...) \ DEFINE_REAL(ret_type, func, __VA_ARGS__) \ DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \ extern "C" \ INTERCEPTOR_ATTRIBUTE \ ret_type WRAP(func)(__VA_ARGS__) #if defined(_WIN32) # define INTERCEPTOR_WINAPI(ret_type, func, ...) \ typedef ret_type (__stdcall *FUNC_TYPE(func))(__VA_ARGS__); \ namespace __interception { \ FUNC_TYPE(func) PTR_TO_REAL(func); \ } \ DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \ extern "C" \ INTERCEPTOR_ATTRIBUTE \ ret_type __stdcall WRAP(func)(__VA_ARGS__) #endif // ISO C++ forbids casting between pointer-to-function and pointer-to-object, // so we use casting via an integral type __interception::uptr, // assuming that system is POSIX-compliant. Using other hacks seem // challenging, as we don't even pass function type to // INTERCEPT_FUNCTION macro, only its name. namespace __interception { #if defined(_WIN64) typedef unsigned long long uptr; // NOLINT #else typedef unsigned long uptr; // NOLINT #endif // _WIN64 } // namespace __interception #define INCLUDED_FROM_INTERCEPTION_LIB #if defined(__linux__) # include "interception_linux.h" # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_LINUX(func) #elif defined(__APPLE__) # include "interception_mac.h" # define OVERRIDE_FUNCTION(old_func, new_func) \ OVERRIDE_FUNCTION_MAC(old_func, new_func) # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_MAC(func) #else // defined(_WIN32) # include "interception_win.h" # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_WIN(func) #endif #undef INCLUDED_FROM_INTERCEPTION_LIB #endif // INTERCEPTION_H