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_asm.h" 18 #include "sanitizer_common/sanitizer_internal_defs.h" 19 20 #if !SANITIZER_LINUX && !SANITIZER_FREEBSD && !SANITIZER_APPLE && \ 21 !SANITIZER_NETBSD && !SANITIZER_WINDOWS && !SANITIZER_FUCHSIA && \ 22 !SANITIZER_SOLARIS 23 # error "Interception doesn't work on this operating system." 24 #endif 25 26 // These typedefs should be used only in the interceptor definitions to replace 27 // the standard system types (e.g. SSIZE_T instead of ssize_t) 28 // On Windows the system headers (basetsd.h) provide a conflicting definition 29 // of SIZE_T/SSIZE_T that do not match the real size_t/ssize_t for 32-bit 30 // systems (using long instead of the expected int). Work around the typedef 31 // redefinition by #defining SIZE_T instead of using a typedef. 32 // TODO: We should be using __sanitizer::usize (and a new ssize) instead of 33 // these new macros as long as we ensure they match the real system definitions. 34 #if SANITIZER_WINDOWS 35 // Ensure that (S)SIZE_T were already defined as we are about to override them. 36 # include <basetsd.h> 37 #endif 38 39 #define SIZE_T __sanitizer::usize 40 #define SSIZE_T __sanitizer::ssize 41 typedef __sanitizer::sptr PTRDIFF_T; 42 typedef __sanitizer::s64 INTMAX_T; 43 typedef __sanitizer::u64 UINTMAX_T; 44 typedef __sanitizer::OFF_T OFF_T; 45 typedef __sanitizer::OFF64_T OFF64_T; 46 47 // How to add an interceptor: 48 // Suppose you need to wrap/replace system function (generally, from libc): 49 // int foo(const char *bar, double baz); 50 // You'll need to: 51 // 1) define INTERCEPTOR(int, foo, const char *bar, double baz) { ... } in 52 // your source file. See the notes below for cases when 53 // INTERCEPTOR_WITH_SUFFIX(...) should be used instead. 54 // 2) Call "INTERCEPT_FUNCTION(foo)" prior to the first call of "foo". 55 // INTERCEPT_FUNCTION(foo) evaluates to "true" iff the function was 56 // intercepted successfully. 57 // You can access original function by calling REAL(foo)(bar, baz). 58 // By default, REAL(foo) will be visible only inside your interceptor, and if 59 // you want to use it in other parts of RTL, you'll need to: 60 // 3a) add DECLARE_REAL(int, foo, const char*, double) to a 61 // header file. 62 // However, if the call "INTERCEPT_FUNCTION(foo)" and definition for 63 // INTERCEPTOR(..., foo, ...) are in different files, you'll instead need to: 64 // 3b) add DECLARE_REAL_AND_INTERCEPTOR(int, foo, const char*, double) 65 // to a header file. 66 67 // Notes: 1. Things may not work properly if macro INTERCEPTOR(...) {...} or 68 // DECLARE_REAL(...) are located inside namespaces. 69 // 2. On Mac you can also use: "OVERRIDE_FUNCTION(foo, zoo)" to 70 // effectively redirect calls from "foo" to "zoo". In this case 71 // you aren't required to implement 72 // INTERCEPTOR(int, foo, const char *bar, double baz) {...} 73 // but instead you'll have to add 74 // DECLARE_REAL(int, foo, const char *bar, double baz) in your 75 // source file (to define a pointer to overriden function). 76 // 3. Some Mac functions have symbol variants discriminated by 77 // additional suffixes, e.g. _$UNIX2003 (see 78 // https://developer.apple.com/library/mac/#releasenotes/Darwin/SymbolVariantsRelNotes/index.html 79 // for more details). To intercept such functions you need to use the 80 // INTERCEPTOR_WITH_SUFFIX(...) macro. 81 82 // How it works on Linux 83 // --------------------- 84 // 85 // To replace system functions on Linux we just need to declare functions with 86 // the same names in our library and then obtain the real function pointers 87 // using dlsym(). 88 // 89 // There is one complication: a user may also intercept some of the functions we 90 // intercept. To allow for up to 3 interceptors (including ours) of a given 91 // function "func", the interceptor implementation is in ___interceptor_func, 92 // which is aliased by a weak function __interceptor_func, which in turn is 93 // aliased (via a trampoline) by weak wrapper function "func". 94 // 95 // Most user interceptors should define a foreign interceptor as follows: 96 // 97 // - provide a non-weak function "func" that performs interception; 98 // - if __interceptor_func exists, call it to perform the real functionality; 99 // - if it does not exist, figure out the real function and call it instead. 100 // 101 // In rare cases, a foreign interceptor (of another dynamic analysis runtime) 102 // may be defined as follows (on supported architectures): 103 // 104 // - provide a non-weak function __interceptor_func that performs interception; 105 // - if ___interceptor_func exists, call it to perform the real functionality; 106 // - if it does not exist, figure out the real function and call it instead; 107 // - provide a weak function "func" that is an alias to __interceptor_func. 108 // 109 // With this protocol, sanitizer interceptors, foreign user interceptors, and 110 // foreign interceptors of other dynamic analysis runtimes, or any combination 111 // thereof, may co-exist simultaneously. 112 // 113 // How it works on Mac OS 114 // ---------------------- 115 // 116 // This is not so on Mac OS, where the two-level namespace makes our replacement 117 // functions invisible to other libraries. This may be overcomed using the 118 // DYLD_FORCE_FLAT_NAMESPACE, but some errors loading the shared libraries in 119 // Chromium were noticed when doing so. 120 // 121 // Instead we create a dylib containing a __DATA,__interpose section that 122 // associates library functions with their wrappers. When this dylib is 123 // preloaded before an executable using DYLD_INSERT_LIBRARIES, it routes all the 124 // calls to interposed functions done through stubs to the wrapper functions. 125 // 126 // As it's decided at compile time which functions are to be intercepted on Mac, 127 // INTERCEPT_FUNCTION() is effectively a no-op on this system. 128 129 #if SANITIZER_APPLE 130 #include <sys/cdefs.h> // For __DARWIN_ALIAS_C(). 131 132 // Just a pair of pointers. 133 struct interpose_substitution { 134 const __sanitizer::uptr replacement; 135 const __sanitizer::uptr original; 136 }; 137 138 // For a function foo() create a global pair of pointers { wrap_foo, foo } in 139 // the __DATA,__interpose section. 140 // As a result all the calls to foo() will be routed to wrap_foo() at runtime. 141 #define INTERPOSER(func_name) __attribute__((used)) \ 142 const interpose_substitution substitution_##func_name[] \ 143 __attribute__((section("__DATA, __interpose"))) = { \ 144 { reinterpret_cast<const uptr>(WRAP(func_name)), \ 145 reinterpret_cast<const uptr>(func_name) } \ 146 } 147 148 // For a function foo() and a wrapper function bar() create a global pair 149 // of pointers { bar, foo } in the __DATA,__interpose section. 150 // As a result all the calls to foo() will be routed to bar() at runtime. 151 #define INTERPOSER_2(func_name, wrapper_name) __attribute__((used)) \ 152 const interpose_substitution substitution_##func_name[] \ 153 __attribute__((section("__DATA, __interpose"))) = { \ 154 { reinterpret_cast<const uptr>(wrapper_name), \ 155 reinterpret_cast<const uptr>(func_name) } \ 156 } 157 158 # define WRAP(x) wrap_##x 159 # define TRAMPOLINE(x) WRAP(x) 160 # define INTERCEPTOR_ATTRIBUTE 161 # define DECLARE_WRAPPER(ret_type, func, ...) 162 163 #elif SANITIZER_WINDOWS 164 # define WRAP(x) __asan_wrap_##x 165 # define TRAMPOLINE(x) WRAP(x) 166 # define INTERCEPTOR_ATTRIBUTE __declspec(dllexport) 167 # define DECLARE_WRAPPER(ret_type, func, ...) \ 168 extern "C" ret_type func(__VA_ARGS__); 169 # define DECLARE_WRAPPER_WINAPI(ret_type, func, ...) \ 170 extern "C" __declspec(dllimport) ret_type __stdcall func(__VA_ARGS__); 171 #elif !SANITIZER_FUCHSIA // LINUX, FREEBSD, NETBSD, SOLARIS 172 # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default"))) 173 # if ASM_INTERCEPTOR_TRAMPOLINE_SUPPORT 174 // Weak aliases of weak aliases do not work, therefore we need to set up a 175 // trampoline function. The function "func" is a weak alias to the trampoline 176 // (so that we may check if "func" was overridden), which calls the weak 177 // function __interceptor_func, which in turn aliases the actual interceptor 178 // implementation ___interceptor_func: 179 // 180 // [wrapper "func": weak] --(alias)--> [TRAMPOLINE(func)] 181 // | 182 // +--------(tail call)-------+ 183 // | 184 // v 185 // [__interceptor_func: weak] --(alias)--> [WRAP(func)] 186 // 187 // We use inline assembly to define most of this, because not all compilers 188 // support functions with the "naked" attribute with every architecture. 189 # define WRAP(x) ___interceptor_ ## x 190 # define TRAMPOLINE(x) __interceptor_trampoline_ ## x 191 # if SANITIZER_FREEBSD || SANITIZER_NETBSD 192 // FreeBSD's dynamic linker (incompliantly) gives non-weak symbols higher 193 // priority than weak ones so weak aliases won't work for indirect calls 194 // in position-independent (-fPIC / -fPIE) mode. 195 # define __ASM_WEAK_WRAPPER(func) ".globl " #func "\n" 196 # else 197 # define __ASM_WEAK_WRAPPER(func) ".weak " #func "\n" 198 # endif // SANITIZER_FREEBSD || SANITIZER_NETBSD 199 # if defined(__arm__) || defined(__aarch64__) 200 # define ASM_TYPE_FUNCTION_STR "%function" 201 # else 202 # define ASM_TYPE_FUNCTION_STR "@function" 203 # endif 204 // Keep trampoline implementation in sync with sanitizer_common/sanitizer_asm.h 205 # define DECLARE_WRAPPER(ret_type, func, ...) \ 206 extern "C" ret_type func(__VA_ARGS__); \ 207 extern "C" ret_type TRAMPOLINE(func)(__VA_ARGS__); \ 208 extern "C" ret_type __interceptor_##func(__VA_ARGS__) \ 209 INTERCEPTOR_ATTRIBUTE __attribute__((weak)) ALIAS(WRAP(func)); \ 210 asm( \ 211 ".text\n" \ 212 __ASM_WEAK_WRAPPER(func) \ 213 ".set " #func ", " SANITIZER_STRINGIFY(TRAMPOLINE(func)) "\n" \ 214 ".globl " SANITIZER_STRINGIFY(TRAMPOLINE(func)) "\n" \ 215 ".type " SANITIZER_STRINGIFY(TRAMPOLINE(func)) ", " \ 216 ASM_TYPE_FUNCTION_STR "\n" \ 217 SANITIZER_STRINGIFY(TRAMPOLINE(func)) ":\n" \ 218 C_ASM_STARTPROC "\n" \ 219 C_ASM_TAIL_CALL(SANITIZER_STRINGIFY(TRAMPOLINE(func)), \ 220 "__interceptor_" \ 221 SANITIZER_STRINGIFY(ASM_PREEMPTIBLE_SYM(func))) "\n" \ 222 C_ASM_ENDPROC "\n" \ 223 ".size " SANITIZER_STRINGIFY(TRAMPOLINE(func)) ", " \ 224 ".-" SANITIZER_STRINGIFY(TRAMPOLINE(func)) "\n" \ 225 ); 226 # else // ASM_INTERCEPTOR_TRAMPOLINE_SUPPORT 227 // Some architectures cannot implement efficient interceptor trampolines with 228 // just a plain jump due to complexities of resolving a preemptible symbol. In 229 // those cases, revert to just this scheme: 230 // 231 // [wrapper "func": weak] --(alias)--> [WRAP(func)] 232 // 233 # define WRAP(x) __interceptor_ ## x 234 # define TRAMPOLINE(x) WRAP(x) 235 # if SANITIZER_FREEBSD || SANITIZER_NETBSD 236 # define __ATTRIBUTE_WEAK_WRAPPER 237 # else 238 # define __ATTRIBUTE_WEAK_WRAPPER __attribute__((weak)) 239 # endif // SANITIZER_FREEBSD || SANITIZER_NETBSD 240 # define DECLARE_WRAPPER(ret_type, func, ...) \ 241 extern "C" ret_type func(__VA_ARGS__) \ 242 INTERCEPTOR_ATTRIBUTE __ATTRIBUTE_WEAK_WRAPPER ALIAS(WRAP(func)); 243 # endif // ASM_INTERCEPTOR_TRAMPOLINE_SUPPORT 244 #endif 245 246 #if SANITIZER_FUCHSIA 247 // There is no general interception at all on Fuchsia. 248 // Sanitizer runtimes just define functions directly to preempt them, 249 // and have bespoke ways to access the underlying libc functions. 250 # include <zircon/sanitizer.h> 251 # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default"))) 252 # define REAL(x) __unsanitized_##x 253 # define DECLARE_REAL(ret_type, func, ...) 254 #elif !SANITIZER_APPLE 255 # define PTR_TO_REAL(x) real_##x 256 # define REAL(x) __interception::PTR_TO_REAL(x) 257 # define FUNC_TYPE(x) x##_type 258 259 # define DECLARE_REAL(ret_type, func, ...) \ 260 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ 261 namespace __interception { \ 262 extern FUNC_TYPE(func) PTR_TO_REAL(func); \ 263 } 264 # define ASSIGN_REAL(dst, src) REAL(dst) = REAL(src) 265 #else // SANITIZER_APPLE 266 # define REAL(x) x 267 # define DECLARE_REAL(ret_type, func, ...) \ 268 extern "C" ret_type func(__VA_ARGS__); 269 # define ASSIGN_REAL(x, y) 270 #endif // SANITIZER_APPLE 271 272 #if !SANITIZER_FUCHSIA 273 # define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) \ 274 DECLARE_REAL(ret_type, func, __VA_ARGS__) \ 275 extern "C" ret_type TRAMPOLINE(func)(__VA_ARGS__); \ 276 extern "C" ret_type WRAP(func)(__VA_ARGS__); 277 // Declare an interceptor and its wrapper defined in a different translation 278 // unit (ex. asm). 279 # define DECLARE_EXTERN_INTERCEPTOR_AND_WRAPPER(ret_type, func, ...) \ 280 extern "C" ret_type TRAMPOLINE(func)(__VA_ARGS__); \ 281 extern "C" ret_type WRAP(func)(__VA_ARGS__); \ 282 extern "C" ret_type func(__VA_ARGS__); 283 #else 284 # define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) 285 # define DECLARE_EXTERN_INTERCEPTOR_AND_WRAPPER(ret_type, func, ...) 286 #endif 287 288 // Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR 289 // macros does its job. In exceptional cases you may need to call REAL(foo) 290 // without defining INTERCEPTOR(..., foo, ...). For example, if you override 291 // foo with an interceptor for other function. 292 #if !SANITIZER_APPLE && !SANITIZER_FUCHSIA 293 # define DEFINE_REAL(ret_type, func, ...) \ 294 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \ 295 namespace __interception { \ 296 FUNC_TYPE(func) PTR_TO_REAL(func); \ 297 } 298 #else 299 # define DEFINE_REAL(ret_type, func, ...) 300 #endif 301 302 #if SANITIZER_FUCHSIA 303 304 // We need to define the __interceptor_func name just to get 305 // sanitizer_common/scripts/gen_dynamic_list.py to export func. 306 // But we don't need to export __interceptor_func to get that. 307 #define INTERCEPTOR(ret_type, func, ...) \ 308 extern "C"[[ gnu::alias(#func), gnu::visibility("hidden") ]] ret_type \ 309 __interceptor_##func(__VA_ARGS__); \ 310 extern "C" INTERCEPTOR_ATTRIBUTE ret_type func(__VA_ARGS__) 311 312 #elif !SANITIZER_APPLE 313 314 #define INTERCEPTOR(ret_type, func, ...) \ 315 DEFINE_REAL(ret_type, func, __VA_ARGS__) \ 316 DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \ 317 extern "C" INTERCEPTOR_ATTRIBUTE ret_type WRAP(func)(__VA_ARGS__) 318 319 // We don't need INTERCEPTOR_WITH_SUFFIX on non-Darwin for now. 320 #define INTERCEPTOR_WITH_SUFFIX(ret_type, func, ...) \ 321 INTERCEPTOR(ret_type, func, __VA_ARGS__) 322 323 #else // SANITIZER_APPLE 324 325 #define INTERCEPTOR_ZZZ(suffix, ret_type, func, ...) \ 326 extern "C" ret_type func(__VA_ARGS__) suffix; \ 327 extern "C" ret_type WRAP(func)(__VA_ARGS__); \ 328 INTERPOSER(func); \ 329 extern "C" INTERCEPTOR_ATTRIBUTE ret_type WRAP(func)(__VA_ARGS__) 330 331 #define INTERCEPTOR(ret_type, func, ...) \ 332 INTERCEPTOR_ZZZ(/*no symbol variants*/, ret_type, func, __VA_ARGS__) 333 334 #define INTERCEPTOR_WITH_SUFFIX(ret_type, func, ...) \ 335 INTERCEPTOR_ZZZ(__DARWIN_ALIAS_C(func), ret_type, func, __VA_ARGS__) 336 337 // Override |overridee| with |overrider|. 338 #define OVERRIDE_FUNCTION(overridee, overrider) \ 339 INTERPOSER_2(overridee, WRAP(overrider)) 340 #endif 341 342 #if SANITIZER_WINDOWS 343 # define INTERCEPTOR_WINAPI(ret_type, func, ...) \ 344 typedef ret_type (__stdcall *FUNC_TYPE(func))(__VA_ARGS__); \ 345 namespace __interception { \ 346 FUNC_TYPE(func) PTR_TO_REAL(func); \ 347 } \ 348 extern "C" INTERCEPTOR_ATTRIBUTE ret_type __stdcall WRAP(func)(__VA_ARGS__) 349 #endif 350 351 // ISO C++ forbids casting between pointer-to-function and pointer-to-object, 352 // so we use casts via uintptr_t (the local __sanitizer::uptr equivalent). 353 namespace __interception { 354 355 #if defined(__ELF__) && !SANITIZER_FUCHSIA 356 // The use of interceptors makes many sanitizers unusable for static linking. 357 // Define a function, if called, will cause a linker error (undefined _DYNAMIC). 358 // However, -static-pie (which is not common) cannot be detected at link time. 359 extern uptr kDynamic[] asm("_DYNAMIC"); 360 inline void DoesNotSupportStaticLinking() { 361 [[maybe_unused]] volatile auto x = &kDynamic; 362 } 363 #else 364 inline void DoesNotSupportStaticLinking() {} 365 #endif 366 } // namespace __interception 367 368 #define INCLUDED_FROM_INTERCEPTION_LIB 369 370 #if SANITIZER_LINUX || SANITIZER_FREEBSD || SANITIZER_NETBSD || \ 371 SANITIZER_SOLARIS 372 373 # include "interception_linux.h" 374 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_LINUX_OR_FREEBSD(func) 375 # define INTERCEPT_FUNCTION_VER(func, symver) \ 376 INTERCEPT_FUNCTION_VER_LINUX_OR_FREEBSD(func, symver) 377 #elif SANITIZER_APPLE 378 # include "interception_mac.h" 379 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_MAC(func) 380 # define INTERCEPT_FUNCTION_VER(func, symver) \ 381 INTERCEPT_FUNCTION_VER_MAC(func, symver) 382 #elif SANITIZER_WINDOWS 383 # include "interception_win.h" 384 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_WIN(func) 385 # define INTERCEPT_FUNCTION_VER(func, symver) \ 386 INTERCEPT_FUNCTION_VER_WIN(func, symver) 387 #endif 388 389 #undef INCLUDED_FROM_INTERCEPTION_LIB 390 391 #endif // INTERCEPTION_H 392