1 //===-- interception.h ------------------------------------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file is a part of AddressSanitizer, an address sanity checker. 10 // 11 // Machinery for providing replacements/wrappers for system functions. 12 //===----------------------------------------------------------------------===// 13 14 #ifndef INTERCEPTION_H 15 #define INTERCEPTION_H 16 17 #include "sanitizer_common/sanitizer_internal_defs.h" 18 19 #if !SANITIZER_LINUX && !SANITIZER_FREEBSD && !SANITIZER_MAC && \ 20 !SANITIZER_NETBSD && !SANITIZER_WINDOWS && !SANITIZER_FUCHSIA && \ 21 !SANITIZER_SOLARIS 22 # error "Interception doesn't work on this operating system." 23 #endif 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) 27 typedef __sanitizer::uptr SIZE_T; 28 typedef __sanitizer::sptr SSIZE_T; 29 typedef __sanitizer::sptr PTRDIFF_T; 30 typedef __sanitizer::s64 INTMAX_T; 31 typedef __sanitizer::u64 UINTMAX_T; 32 typedef __sanitizer::OFF_T OFF_T; 33 typedef __sanitizer::OFF64_T OFF64_T; 34 35 // How to add an interceptor: 36 // Suppose you need to wrap/replace system function (generally, from libc): 37 // int foo(const char *bar, double baz); 38 // You'll need to: 39 // 1) define INTERCEPTOR(int, foo, const char *bar, double baz) { ... } in 40 // your source file. See the notes below for cases when 41 // INTERCEPTOR_WITH_SUFFIX(...) should be used instead. 42 // 2) Call "INTERCEPT_FUNCTION(foo)" prior to the first call of "foo". 43 // INTERCEPT_FUNCTION(foo) evaluates to "true" iff the function was 44 // intercepted successfully. 45 // You can access original function by calling REAL(foo)(bar, baz). 46 // By default, REAL(foo) will be visible only inside your interceptor, and if 47 // you want to use it in other parts of RTL, you'll need to: 48 // 3a) add DECLARE_REAL(int, foo, const char*, double) to a 49 // header file. 50 // However, if the call "INTERCEPT_FUNCTION(foo)" and definition for 51 // INTERCEPTOR(..., foo, ...) are in different files, you'll instead need to: 52 // 3b) add DECLARE_REAL_AND_INTERCEPTOR(int, foo, const char*, double) 53 // to a header file. 54 55 // Notes: 1. Things may not work properly if macro INTERCEPTOR(...) {...} or 56 // DECLARE_REAL(...) are located inside namespaces. 57 // 2. On Mac you can also use: "OVERRIDE_FUNCTION(foo, zoo)" to 58 // effectively redirect calls from "foo" to "zoo". In this case 59 // you aren't required to implement 60 // INTERCEPTOR(int, foo, const char *bar, double baz) {...} 61 // but instead you'll have to add 62 // DECLARE_REAL(int, foo, const char *bar, double baz) in your 63 // source file (to define a pointer to overriden function). 64 // 3. Some Mac functions have symbol variants discriminated by 65 // additional suffixes, e.g. _$UNIX2003 (see 66 // https://developer.apple.com/library/mac/#releasenotes/Darwin/SymbolVariantsRelNotes/index.html 67 // for more details). To intercept such functions you need to use the 68 // INTERCEPTOR_WITH_SUFFIX(...) macro. 69 70 // How it works: 71 // To replace system functions on Linux we just need to declare functions 72 // with same names in our library and then obtain the real function pointers 73 // using dlsym(). 74 // There is one complication. A user may also intercept some of the functions 75 // we intercept. To resolve this we declare our interceptors with __interceptor_ 76 // prefix, and then make actual interceptors weak aliases to __interceptor_ 77 // functions. 78 // 79 // This is not so on Mac OS, where the two-level namespace makes 80 // our replacement functions invisible to other libraries. This may be overcomed 81 // using the DYLD_FORCE_FLAT_NAMESPACE, but some errors loading the shared 82 // libraries in Chromium were noticed when doing so. 83 // Instead we create a dylib containing a __DATA,__interpose section that 84 // associates library functions with their wrappers. When this dylib is 85 // preloaded before an executable using DYLD_INSERT_LIBRARIES, it routes all 86 // the calls to interposed functions done through stubs to the wrapper 87 // functions. 88 // As it's decided at compile time which functions are to be intercepted on Mac, 89 // INTERCEPT_FUNCTION() is effectively a no-op on this system. 90 91 #if SANITIZER_MAC 92 #include <sys/cdefs.h> // For __DARWIN_ALIAS_C(). 93 94 // Just a pair of pointers. 95 struct interpose_substitution { 96 const __sanitizer::uptr replacement; 97 const __sanitizer::uptr original; 98 }; 99 100 // For a function foo() create a global pair of pointers { wrap_foo, foo } in 101 // the __DATA,__interpose section. 102 // As a result all the calls to foo() will be routed to wrap_foo() at runtime. 103 #define INTERPOSER(func_name) __attribute__((used)) \ 104 const interpose_substitution substitution_##func_name[] \ 105 __attribute__((section("__DATA, __interpose"))) = { \ 106 { reinterpret_cast<const uptr>(WRAP(func_name)), \ 107 reinterpret_cast<const uptr>(func_name) } \ 108 } 109 110 // For a function foo() and a wrapper function bar() create a global pair 111 // of pointers { bar, foo } in the __DATA,__interpose section. 112 // As a result all the calls to foo() will be routed to bar() at runtime. 113 #define INTERPOSER_2(func_name, wrapper_name) __attribute__((used)) \ 114 const interpose_substitution substitution_##func_name[] \ 115 __attribute__((section("__DATA, __interpose"))) = { \ 116 { reinterpret_cast<const uptr>(wrapper_name), \ 117 reinterpret_cast<const uptr>(func_name) } \ 118 } 119 120 # define WRAP(x) wrap_##x 121 # define WRAPPER_NAME(x) "wrap_"#x 122 # define INTERCEPTOR_ATTRIBUTE 123 # define DECLARE_WRAPPER(ret_type, func, ...) 124 125 #elif SANITIZER_WINDOWS 126 # define WRAP(x) __asan_wrap_##x 127 # define WRAPPER_NAME(x) "__asan_wrap_"#x 128 # define INTERCEPTOR_ATTRIBUTE __declspec(dllexport) 129 # define DECLARE_WRAPPER(ret_type, func, ...) \ 130 extern "C" ret_type func(__VA_ARGS__); 131 # define DECLARE_WRAPPER_WINAPI(ret_type, func, ...) \ 132 extern "C" __declspec(dllimport) ret_type __stdcall func(__VA_ARGS__); 133 #elif SANITIZER_FREEBSD || SANITIZER_NETBSD 134 # define WRAP(x) __interceptor_ ## x 135 # define WRAPPER_NAME(x) "__interceptor_" #x 136 # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default"))) 137 // FreeBSD's dynamic linker (incompliantly) gives non-weak symbols higher 138 // priority than weak ones so weak aliases won't work for indirect calls 139 // in position-independent (-fPIC / -fPIE) mode. 140 # define DECLARE_WRAPPER(ret_type, func, ...) \ 141 extern "C" ret_type func(__VA_ARGS__) \ 142 __attribute__((alias("__interceptor_" #func), visibility("default"))); 143 #elif !SANITIZER_FUCHSIA 144 # define WRAP(x) __interceptor_ ## x 145 # define WRAPPER_NAME(x) "__interceptor_" #x 146 # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default"))) 147 # define DECLARE_WRAPPER(ret_type, func, ...) \ 148 extern "C" ret_type func(__VA_ARGS__) \ 149 __attribute__((weak, alias("__interceptor_" #func), visibility("default"))); 150 #endif 151 152 #if SANITIZER_FUCHSIA 153 // There is no general interception at all on Fuchsia. 154 // Sanitizer runtimes just define functions directly to preempt them, 155 // and have bespoke ways to access the underlying libc functions. 156 # include <zircon/sanitizer.h> 157 # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default"))) 158 # define REAL(x) __unsanitized_##x 159 # define DECLARE_REAL(ret_type, func, ...) 160 #elif !SANITIZER_MAC 161 # define PTR_TO_REAL(x) real_##x 162 # define REAL(x) __interception::PTR_TO_REAL(x) 163 # define FUNC_TYPE(x) x##_type 164 165 # define DECLARE_REAL(ret_type, func, ...) \ 166 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ 167 namespace __interception { \ 168 extern FUNC_TYPE(func) PTR_TO_REAL(func); \ 169 } 170 # define ASSIGN_REAL(dst, src) REAL(dst) = REAL(src) 171 #else // SANITIZER_MAC 172 # define REAL(x) x 173 # define DECLARE_REAL(ret_type, func, ...) \ 174 extern "C" ret_type func(__VA_ARGS__); 175 # define ASSIGN_REAL(x, y) 176 #endif // SANITIZER_MAC 177 178 #if !SANITIZER_FUCHSIA 179 # define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) \ 180 DECLARE_REAL(ret_type, func, __VA_ARGS__) \ 181 extern "C" ret_type WRAP(func)(__VA_ARGS__); 182 // Declare an interceptor and its wrapper defined in a different translation 183 // unit (ex. asm). 184 # define DECLARE_EXTERN_INTERCEPTOR_AND_WRAPPER(ret_type, func, ...) \ 185 extern "C" ret_type WRAP(func)(__VA_ARGS__); \ 186 extern "C" ret_type func(__VA_ARGS__); 187 #else 188 # define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) 189 # define DECLARE_EXTERN_INTERCEPTOR_AND_WRAPPER(ret_type, func, ...) 190 #endif 191 192 // Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR 193 // macros does its job. In exceptional cases you may need to call REAL(foo) 194 // without defining INTERCEPTOR(..., foo, ...). For example, if you override 195 // foo with an interceptor for other function. 196 #if !SANITIZER_MAC && !SANITIZER_FUCHSIA 197 # define DEFINE_REAL(ret_type, func, ...) \ 198 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ 199 namespace __interception { \ 200 FUNC_TYPE(func) PTR_TO_REAL(func); \ 201 } 202 #else 203 # define DEFINE_REAL(ret_type, func, ...) 204 #endif 205 206 #if SANITIZER_FUCHSIA 207 208 // We need to define the __interceptor_func name just to get 209 // sanitizer_common/scripts/gen_dynamic_list.py to export func. 210 // But we don't need to export __interceptor_func to get that. 211 #define INTERCEPTOR(ret_type, func, ...) \ 212 extern "C"[[ gnu::alias(#func), gnu::visibility("hidden") ]] ret_type \ 213 __interceptor_##func(__VA_ARGS__); \ 214 extern "C" INTERCEPTOR_ATTRIBUTE ret_type func(__VA_ARGS__) 215 216 #elif !SANITIZER_MAC 217 218 #define INTERCEPTOR(ret_type, func, ...) \ 219 DEFINE_REAL(ret_type, func, __VA_ARGS__) \ 220 DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \ 221 extern "C" \ 222 INTERCEPTOR_ATTRIBUTE \ 223 ret_type WRAP(func)(__VA_ARGS__) 224 225 // We don't need INTERCEPTOR_WITH_SUFFIX on non-Darwin for now. 226 #define INTERCEPTOR_WITH_SUFFIX(ret_type, func, ...) \ 227 INTERCEPTOR(ret_type, func, __VA_ARGS__) 228 229 #else // SANITIZER_MAC 230 231 #define INTERCEPTOR_ZZZ(suffix, ret_type, func, ...) \ 232 extern "C" ret_type func(__VA_ARGS__) suffix; \ 233 extern "C" ret_type WRAP(func)(__VA_ARGS__); \ 234 INTERPOSER(func); \ 235 extern "C" INTERCEPTOR_ATTRIBUTE ret_type WRAP(func)(__VA_ARGS__) 236 237 #define INTERCEPTOR(ret_type, func, ...) \ 238 INTERCEPTOR_ZZZ(/*no symbol variants*/, ret_type, func, __VA_ARGS__) 239 240 #define INTERCEPTOR_WITH_SUFFIX(ret_type, func, ...) \ 241 INTERCEPTOR_ZZZ(__DARWIN_ALIAS_C(func), ret_type, func, __VA_ARGS__) 242 243 // Override |overridee| with |overrider|. 244 #define OVERRIDE_FUNCTION(overridee, overrider) \ 245 INTERPOSER_2(overridee, WRAP(overrider)) 246 #endif 247 248 #if SANITIZER_WINDOWS 249 # define INTERCEPTOR_WINAPI(ret_type, func, ...) \ 250 typedef ret_type (__stdcall *FUNC_TYPE(func))(__VA_ARGS__); \ 251 namespace __interception { \ 252 FUNC_TYPE(func) PTR_TO_REAL(func); \ 253 } \ 254 extern "C" \ 255 INTERCEPTOR_ATTRIBUTE \ 256 ret_type __stdcall WRAP(func)(__VA_ARGS__) 257 #endif 258 259 // ISO C++ forbids casting between pointer-to-function and pointer-to-object, 260 // so we use casting via an integral type __interception::uptr, 261 // assuming that system is POSIX-compliant. Using other hacks seem 262 // challenging, as we don't even pass function type to 263 // INTERCEPT_FUNCTION macro, only its name. 264 namespace __interception { 265 #if defined(_WIN64) 266 typedef unsigned long long uptr; 267 #else 268 typedef unsigned long uptr; 269 #endif // _WIN64 270 } // namespace __interception 271 272 #define INCLUDED_FROM_INTERCEPTION_LIB 273 274 #if SANITIZER_LINUX || SANITIZER_FREEBSD || SANITIZER_NETBSD || \ 275 SANITIZER_SOLARIS 276 277 # include "interception_linux.h" 278 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_LINUX_OR_FREEBSD(func) 279 # define INTERCEPT_FUNCTION_VER(func, symver) \ 280 INTERCEPT_FUNCTION_VER_LINUX_OR_FREEBSD(func, symver) 281 #elif SANITIZER_MAC 282 # include "interception_mac.h" 283 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_MAC(func) 284 # define INTERCEPT_FUNCTION_VER(func, symver) \ 285 INTERCEPT_FUNCTION_VER_MAC(func, symver) 286 #elif SANITIZER_WINDOWS 287 # include "interception_win.h" 288 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_WIN(func) 289 # define INTERCEPT_FUNCTION_VER(func, symver) \ 290 INTERCEPT_FUNCTION_VER_WIN(func, symver) 291 #endif 292 293 #undef INCLUDED_FROM_INTERCEPTION_LIB 294 295 #endif // INTERCEPTION_H 296