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(__FreeBSD__) && \ 19 !defined(__APPLE__) && !defined(_WIN32) 20# error "Interception doesn't work on this operating system." 21#endif 22 23#include "sanitizer_common/sanitizer_internal_defs.h" 24 25// These typedefs should be used only in the interceptor definitions to replace 26// the standard system types (e.g. SSIZE_T instead of ssize_t) 27typedef __sanitizer::uptr SIZE_T; 28typedef __sanitizer::sptr SSIZE_T; 29typedef __sanitizer::sptr PTRDIFF_T; 30typedef __sanitizer::s64 INTMAX_T; 31typedef __sanitizer::OFF_T OFF_T; 32typedef __sanitizer::OFF64_T OFF64_T; 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. See the notes below for cases when 40// INTERCEPTOR_WITH_SUFFIX(...) should be used instead. 41// 2) Call "INTERCEPT_FUNCTION(foo)" prior to the first call of "foo". 42// INTERCEPT_FUNCTION(foo) evaluates to "true" iff the function was 43// intercepted successfully. 44// You can access original function by calling REAL(foo)(bar, baz). 45// By default, REAL(foo) will be visible only inside your interceptor, and if 46// you want to use it in other parts of RTL, you'll need to: 47// 3a) add DECLARE_REAL(int, foo, const char*, double) to a 48// header file. 49// However, if the call "INTERCEPT_FUNCTION(foo)" and definition for 50// INTERCEPTOR(..., foo, ...) are in different files, you'll instead need to: 51// 3b) add DECLARE_REAL_AND_INTERCEPTOR(int, foo, const char*, double) 52// to a header file. 53 54// Notes: 1. Things may not work properly if macro INTERCEPTOR(...) {...} or 55// DECLARE_REAL(...) are located inside namespaces. 56// 2. On Mac you can also use: "OVERRIDE_FUNCTION(foo, zoo)" to 57// effectively redirect calls from "foo" to "zoo". In this case 58// you aren't required to implement 59// INTERCEPTOR(int, foo, const char *bar, double baz) {...} 60// but instead you'll have to add 61// DECLARE_REAL(int, foo, const char *bar, double baz) in your 62// source file (to define a pointer to overriden function). 63// 3. Some Mac functions have symbol variants discriminated by 64// additional suffixes, e.g. _$UNIX2003 (see 65// https://developer.apple.com/library/mac/#releasenotes/Darwin/SymbolVariantsRelNotes/index.html 66// for more details). To intercept such functions you need to use the 67// INTERCEPTOR_WITH_SUFFIX(...) macro. 68 69// How it works: 70// To replace system functions on Linux we just need to declare functions 71// with same names in our library and then obtain the real function pointers 72// using dlsym(). 73// There is one complication. A user may also intercept some of the functions 74// we intercept. To resolve this we declare our interceptors with __interceptor_ 75// prefix, and then make actual interceptors weak aliases to __interceptor_ 76// functions. 77// 78// This is not so on Mac OS, where the two-level namespace makes 79// our replacement functions invisible to other libraries. This may be overcomed 80// using the DYLD_FORCE_FLAT_NAMESPACE, but some errors loading the shared 81// libraries in Chromium were noticed when doing so. 82// Instead we create a dylib containing a __DATA,__interpose section that 83// associates library functions with their wrappers. When this dylib is 84// preloaded before an executable using DYLD_INSERT_LIBRARIES, it routes all 85// the calls to interposed functions done through stubs to the wrapper 86// functions. 87// As it's decided at compile time which functions are to be intercepted on Mac, 88// INTERCEPT_FUNCTION() is effectively a no-op on this system. 89 90#if defined(__APPLE__) 91#include <sys/cdefs.h> // For __DARWIN_ALIAS_C(). 92 93// Just a pair of pointers. 94struct interpose_substitution { 95 const uptr replacement; 96 const uptr original; 97}; 98 99// For a function foo() create a global pair of pointers { wrap_foo, foo } in 100// the __DATA,__interpose section. 101// As a result all the calls to foo() will be routed to wrap_foo() at runtime. 102#define INTERPOSER(func_name) __attribute__((used)) \ 103const interpose_substitution substitution_##func_name[] \ 104 __attribute__((section("__DATA, __interpose"))) = { \ 105 { reinterpret_cast<const uptr>(WRAP(func_name)), \ 106 reinterpret_cast<const uptr>(func_name) } \ 107} 108 109// For a function foo() and a wrapper function bar() create a global pair 110// of pointers { bar, foo } in the __DATA,__interpose section. 111// As a result all the calls to foo() will be routed to bar() at runtime. 112#define INTERPOSER_2(func_name, wrapper_name) __attribute__((used)) \ 113const interpose_substitution substitution_##func_name[] \ 114 __attribute__((section("__DATA, __interpose"))) = { \ 115 { reinterpret_cast<const uptr>(wrapper_name), \ 116 reinterpret_cast<const uptr>(func_name) } \ 117} 118 119# define WRAP(x) wrap_##x 120# define WRAPPER_NAME(x) "wrap_"#x 121# define INTERCEPTOR_ATTRIBUTE 122# define DECLARE_WRAPPER(ret_type, func, ...) 123 124#elif defined(_WIN32) 125# if defined(_DLL) // DLL CRT 126# define WRAP(x) x 127# define WRAPPER_NAME(x) #x 128# define INTERCEPTOR_ATTRIBUTE 129# else // Static CRT 130# define WRAP(x) __asan_wrap_##x 131# define WRAPPER_NAME(x) "__asan_wrap_"#x 132# define INTERCEPTOR_ATTRIBUTE __declspec(dllexport) 133# endif 134# define DECLARE_WRAPPER(ret_type, func, ...) \ 135 extern "C" ret_type func(__VA_ARGS__); 136# define DECLARE_WRAPPER_WINAPI(ret_type, func, ...) \ 137 extern "C" __declspec(dllimport) ret_type __stdcall func(__VA_ARGS__); 138#elif defined(__FreeBSD__) 139# define WRAP(x) __interceptor_ ## x 140# define WRAPPER_NAME(x) "__interceptor_" #x 141# define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default"))) 142// FreeBSD's dynamic linker (incompliantly) gives non-weak symbols higher 143// priority than weak ones so weak aliases won't work for indirect calls 144// in position-independent (-fPIC / -fPIE) mode. 145# define DECLARE_WRAPPER(ret_type, func, ...) \ 146 extern "C" ret_type func(__VA_ARGS__) \ 147 __attribute__((alias("__interceptor_" #func), visibility("default"))); 148#else 149# define WRAP(x) __interceptor_ ## x 150# define WRAPPER_NAME(x) "__interceptor_" #x 151# define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default"))) 152# define DECLARE_WRAPPER(ret_type, func, ...) \ 153 extern "C" ret_type func(__VA_ARGS__) \ 154 __attribute__((weak, alias("__interceptor_" #func), visibility("default"))); 155#endif 156 157#if !defined(__APPLE__) 158# define PTR_TO_REAL(x) real_##x 159# define REAL(x) __interception::PTR_TO_REAL(x) 160# define FUNC_TYPE(x) x##_f 161 162# define DECLARE_REAL(ret_type, func, ...) \ 163 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ 164 namespace __interception { \ 165 extern FUNC_TYPE(func) PTR_TO_REAL(func); \ 166 } 167#else // __APPLE__ 168# define REAL(x) x 169# define DECLARE_REAL(ret_type, func, ...) \ 170 extern "C" ret_type func(__VA_ARGS__); 171#endif // __APPLE__ 172 173#define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) \ 174 DECLARE_REAL(ret_type, func, __VA_ARGS__) \ 175 extern "C" ret_type WRAP(func)(__VA_ARGS__); 176 177// Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR 178// macros does its job. In exceptional cases you may need to call REAL(foo) 179// without defining INTERCEPTOR(..., foo, ...). For example, if you override 180// foo with an interceptor for other function. 181#if !defined(__APPLE__) 182# define DEFINE_REAL(ret_type, func, ...) \ 183 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ 184 namespace __interception { \ 185 FUNC_TYPE(func) PTR_TO_REAL(func); \ 186 } 187#else 188# define DEFINE_REAL(ret_type, func, ...) 189#endif 190 191#if !defined(__APPLE__) 192#define INTERCEPTOR(ret_type, func, ...) \ 193 DEFINE_REAL(ret_type, func, __VA_ARGS__) \ 194 DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \ 195 extern "C" \ 196 INTERCEPTOR_ATTRIBUTE \ 197 ret_type WRAP(func)(__VA_ARGS__) 198 199// We don't need INTERCEPTOR_WITH_SUFFIX on non-Darwin for now. 200#define INTERCEPTOR_WITH_SUFFIX(ret_type, func, ...) \ 201 INTERCEPTOR(ret_type, func, __VA_ARGS__) 202 203#else // __APPLE__ 204 205#define INTERCEPTOR_ZZZ(suffix, ret_type, func, ...) \ 206 extern "C" ret_type func(__VA_ARGS__) suffix; \ 207 extern "C" ret_type WRAP(func)(__VA_ARGS__); \ 208 INTERPOSER(func); \ 209 extern "C" INTERCEPTOR_ATTRIBUTE ret_type WRAP(func)(__VA_ARGS__) 210 211#define INTERCEPTOR(ret_type, func, ...) \ 212 INTERCEPTOR_ZZZ(/*no symbol variants*/, ret_type, func, __VA_ARGS__) 213 214#define INTERCEPTOR_WITH_SUFFIX(ret_type, func, ...) \ 215 INTERCEPTOR_ZZZ(__DARWIN_ALIAS_C(func), ret_type, func, __VA_ARGS__) 216 217// Override |overridee| with |overrider|. 218#define OVERRIDE_FUNCTION(overridee, overrider) \ 219 INTERPOSER_2(overridee, WRAP(overrider)) 220#endif 221 222#if defined(_WIN32) 223# define INTERCEPTOR_WINAPI(ret_type, func, ...) \ 224 typedef ret_type (__stdcall *FUNC_TYPE(func))(__VA_ARGS__); \ 225 namespace __interception { \ 226 FUNC_TYPE(func) PTR_TO_REAL(func); \ 227 } \ 228 DECLARE_WRAPPER_WINAPI(ret_type, func, __VA_ARGS__) \ 229 extern "C" \ 230 INTERCEPTOR_ATTRIBUTE \ 231 ret_type __stdcall WRAP(func)(__VA_ARGS__) 232#endif 233 234// ISO C++ forbids casting between pointer-to-function and pointer-to-object, 235// so we use casting via an integral type __interception::uptr, 236// assuming that system is POSIX-compliant. Using other hacks seem 237// challenging, as we don't even pass function type to 238// INTERCEPT_FUNCTION macro, only its name. 239namespace __interception { 240#if defined(_WIN64) 241typedef unsigned long long uptr; // NOLINT 242#else 243typedef unsigned long uptr; // NOLINT 244#endif // _WIN64 245} // namespace __interception 246 247#define INCLUDED_FROM_INTERCEPTION_LIB 248 249#if defined(__linux__) || defined(__FreeBSD__) 250# include "interception_linux.h" 251# define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_LINUX_OR_FREEBSD(func) 252# define INTERCEPT_FUNCTION_VER(func, symver) \ 253 INTERCEPT_FUNCTION_VER_LINUX_OR_FREEBSD(func, symver) 254#elif defined(__APPLE__) 255# include "interception_mac.h" 256# define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_MAC(func) 257# define INTERCEPT_FUNCTION_VER(func, symver) \ 258 INTERCEPT_FUNCTION_VER_MAC(func, symver) 259#else // defined(_WIN32) 260# include "interception_win.h" 261# define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_WIN(func) 262# define INTERCEPT_FUNCTION_VER(func, symver) \ 263 INTERCEPT_FUNCTION_VER_WIN(func, symver) 264#endif 265 266#undef INCLUDED_FROM_INTERCEPTION_LIB 267 268#endif // INTERCEPTION_H 269