libsanitizer/interception/interception.h

   1 //===-- interception.h ------------------------------------------*- C++ -*-===//
   2 //
   3 // This file is distributed under the University of Illinois Open Source
   4 // License. See LICENSE.TXT for details.
   5 //
   6 //===----------------------------------------------------------------------===//
   7 //
   8 // This file is a part of AddressSanitizer, an address sanity checker.
   9 //
  10 // Machinery for providing replacements/wrappers for system functions.
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef INTERCEPTION_H
  14 #define INTERCEPTION_H
  15
  16 #if !defined(__linux__) && !defined(__APPLE__) && !defined(_WIN32)
  17 # error "Interception doesn't work on this operating system."
  18 #endif
  19
  20 // How to use this library:
  21 //      1) Include this header to define your own interceptors
  22 //         (see details below).
  23 //      2) Build all *.cc files and link against them.
  24 // On Mac you will also need to:
  25 //      3) Provide your own implementation for the following functions:
  26 //           mach_error_t __interception::allocate_island(void **ptr,
  27 //                                                      size_t size,
  28 //                                                      void *hint);
  29 //           mach_error_t __interception::deallocate_island(void *ptr);
  30 //         See "interception_mac.h" for more details.
  31
  32 // How to add an interceptor:
  33 // Suppose you need to wrap/replace system function (generally, from libc):
  34 //      int foo(const char *bar, double baz);
  35 // You'll need to:
  36 //      1) define INTERCEPTOR(int, foo, const char *bar, double baz) { ... } in
  37 //         your source file.
  38 //      2) Call "INTERCEPT_FUNCTION(foo)" prior to the first call of "foo".
  39 //         INTERCEPT_FUNCTION(foo) evaluates to "true" iff the function was
  40 //         intercepted successfully.
  41 // You can access original function by calling REAL(foo)(bar, baz).
  42 // By default, REAL(foo) will be visible only inside your interceptor, and if
  43 // you want to use it in other parts of RTL, you'll need to:
  44 //      3a) add DECLARE_REAL(int, foo, const char*, double) to a
  45 //          header file.
  46 // However, if the call "INTERCEPT_FUNCTION(foo)" and definition for
  47 // INTERCEPTOR(..., foo, ...) are in different files, you'll instead need to:
  48 //      3b) add DECLARE_REAL_AND_INTERCEPTOR(int, foo, const char*, double)
  49 //          to a header file.
  50
  51 // Notes: 1. Things may not work properly if macro INTERCEPT(...) {...} or
  52 //           DECLARE_REAL(...) are located inside namespaces.
  53 //        2. On Mac you can also use: "OVERRIDE_FUNCTION(foo, zoo);" to
  54 //           effectively redirect calls from "foo" to "zoo". In this case
  55 //           you aren't required to implement
  56 //           INTERCEPTOR(int, foo, const char *bar, double baz) {...}
  57 //           but instead you'll have to add
  58 //           DEFINE_REAL(int, foo, const char *bar, double baz) in your
  59 //           source file (to define a pointer to overriden function).
  60
  61 // How it works:
  62 // To replace system functions on Linux we just need to declare functions
  63 // with same names in our library and then obtain the real function pointers
  64 // using dlsym().
  65 // There is one complication. A user may also intercept some of the functions
  66 // we intercept. To resolve this we declare our interceptors with __interceptor_
  67 // prefix, and then make actual interceptors weak aliases to __interceptor_
  68 // functions.
  69 // This is not so on Mac OS, where the two-level namespace makes
  70 // our replacement functions invisible to other libraries. This may be overcomed
  71 // using the DYLD_FORCE_FLAT_NAMESPACE, but some errors loading the shared
  72 // libraries in Chromium were noticed when doing so. Instead we use
  73 // mach_override, a handy framework for patching functions at runtime.
  74 // To avoid possible name clashes, our replacement functions have
  75 // the "wrap_" prefix on Mac.
  76 // An alternative to function patching is to create a dylib containing a
  77 // __DATA,__interpose section that associates library functions with their
  78 // wrappers. When this dylib is preloaded before an executable using
  79 // DYLD_INSERT_LIBRARIES, it routes all the calls to interposed functions done
  80 // through stubs to the wrapper functions. Such a library is built with
  81 // -DMAC_INTERPOSE_FUNCTIONS=1.
  82
  83 #if !defined(MAC_INTERPOSE_FUNCTIONS) || !defined(__APPLE__)
  84 # define MAC_INTERPOSE_FUNCTIONS 0
  85 #endif
  86
  87 #if defined(__APPLE__)
  88 # define WRAP(x) wrap_##x
  89 # define WRAPPER_NAME(x) "wrap_"#x
  90 # define INTERCEPTOR_ATTRIBUTE
  91 # define DECLARE_WRAPPER(ret_type, func, ...)
  92 #elif defined(_WIN32)
  93 # if defined(_DLL)  // DLL CRT
  94 #  define WRAP(x) x
  95 #  define WRAPPER_NAME(x) #x
  96 #  define INTERCEPTOR_ATTRIBUTE
  97 # else  // Static CRT
  98 #  define WRAP(x) wrap_##x
  99 #  define WRAPPER_NAME(x) "wrap_"#x
 100 #  define INTERCEPTOR_ATTRIBUTE
 101 # endif
 102 # define DECLARE_WRAPPER(ret_type, func, ...)
 103 #else
 104 # define WRAP(x) __interceptor_ ## x
 105 # define WRAPPER_NAME(x) "__interceptor_" #x
 106 # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default")))
 107 # define DECLARE_WRAPPER(ret_type, func, ...) \
 108     extern "C" ret_type func(__VA_ARGS__) \
 109     __attribute__((weak, alias("__interceptor_" #func), visibility("default")));
 110 #endif
 111
 112 #if !MAC_INTERPOSE_FUNCTIONS
 113 # define PTR_TO_REAL(x) real_##x
 114 # define REAL(x) __interception::PTR_TO_REAL(x)
 115 # define FUNC_TYPE(x) x##_f
 116
 117 # define DECLARE_REAL(ret_type, func, ...) \
 118     typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \
 119     namespace __interception { \
 120       extern FUNC_TYPE(func) PTR_TO_REAL(func); \
 121     }
 122 #else  // MAC_INTERPOSE_FUNCTIONS
 123 # define REAL(x) x
 124 # define DECLARE_REAL(ret_type, func, ...) \
 125     extern "C" ret_type func(__VA_ARGS__);
 126 #endif  // MAC_INTERPOSE_FUNCTIONS
 127
 128 #define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) \
 129   DECLARE_REAL(ret_type, func, __VA_ARGS__) \
 130   extern "C" ret_type WRAP(func)(__VA_ARGS__);
 131
 132 // Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR
 133 // macros does its job. In exceptional cases you may need to call REAL(foo)
 134 // without defining INTERCEPTOR(..., foo, ...). For example, if you override
 135 // foo with an interceptor for other function.
 136 #if !MAC_INTERPOSE_FUNCTIONS
 137 # define DEFINE_REAL(ret_type, func, ...) \
 138     typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \
 139     namespace __interception { \
 140       FUNC_TYPE(func) PTR_TO_REAL(func); \
 141     }
 142 #else
 143 # define DEFINE_REAL(ret_type, func, ...)
 144 #endif
 145
 146 #define INTERCEPTOR(ret_type, func, ...) \
 147   DEFINE_REAL(ret_type, func, __VA_ARGS__) \
 148   DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \
 149   extern "C" \
 150   INTERCEPTOR_ATTRIBUTE \
 151   ret_type WRAP(func)(__VA_ARGS__)
 152
 153 #if defined(_WIN32)
 154 # define INTERCEPTOR_WINAPI(ret_type, func, ...) \
 155     typedef ret_type (__stdcall *FUNC_TYPE(func))(__VA_ARGS__); \
 156     namespace __interception { \
 157       FUNC_TYPE(func) PTR_TO_REAL(func); \
 158     } \
 159     DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \
 160     extern "C" \
 161     INTERCEPTOR_ATTRIBUTE \
 162     ret_type __stdcall WRAP(func)(__VA_ARGS__)
 163 #endif
 164
 165 // ISO C++ forbids casting between pointer-to-function and pointer-to-object,
 166 // so we use casting via an integral type __interception::uptr,
 167 // assuming that system is POSIX-compliant. Using other hacks seem
 168 // challenging, as we don't even pass function type to
 169 // INTERCEPT_FUNCTION macro, only its name.
 170 namespace __interception {
 171 #if defined(_WIN64)
 172 typedef unsigned long long uptr;  // NOLINT
 173 #else
 174 typedef unsigned long uptr;  // NOLINT
 175 #endif  // _WIN64
 176 }  // namespace __interception
 177
 178 #define INCLUDED_FROM_INTERCEPTION_LIB
 179
 180 #if defined(__linux__)
 181 # include "interception_linux.h"
 182 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_LINUX(func)
 183 #elif defined(__APPLE__)
 184 # include "interception_mac.h"
 185 # define OVERRIDE_FUNCTION(old_func, new_func) \
 186     OVERRIDE_FUNCTION_MAC(old_func, new_func)
 187 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_MAC(func)
 188 #else  // defined(_WIN32)
 189 # include "interception_win.h"
 190 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_WIN(func)
 191 #endif
 192
 193 #undef INCLUDED_FROM_INTERCEPTION_LIB
 194
 195 #endif  // INTERCEPTION_H