interception.h revision 5b29018cf422e7711fb760b733c32127397a43fc 
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(__APPLE__) && !defined(_WIN32)
19# error "Interception doesn't work on this operating system."
20#endif
21
22// How to use this library:
23//      1) Include this header to define your own interceptors
24//         (see details below).
25//      2) Build all *.cc files and link against them.
26// On Mac you will also need to:
27//      3) Provide your own implementation for the following functions:
28//           mach_error_t __interception::allocate_island(void **ptr,
29//                                                      size_t size,
30//                                                      void *hint);
31//           mach_error_t __interception::deallocate_island(void *ptr);
32//         See "interception_mac.h" for more details.
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.
40//      2) Call "INTERCEPT_FUNCTION(foo)" prior to the first call of "foo".
41//         INTERCEPT_FUNCTION(foo) evaluates to "true" iff the function was
42//         intercepted successfully.
43// You can access original function by calling REAL(foo)(bar, baz).
44// By default, REAL(foo) will be visible only inside your interceptor, and if
45// you want to use it in other parts of RTL, you'll need to:
46//      3a) add DECLARE_REAL(int, foo, const char*, double); to a
47//          header file.
48// However, if the call "INTERCEPT_FUNCTION(foo)" and definition for
49// INTERCEPTOR(..., foo, ...) are in different files, you'll instead need to:
50//      3b) add DECLARE_REAL_AND_INTERCEPTOR(int, foo, const char*, double);
51//          to a header file.
52
53// Notes: 1. Things may not work properly if macro INTERCEPT(...) {...} or
54//           DECLARE_REAL(...); are located inside namespaces.
55//        2. On Mac you can also use: "OVERRIDE_FUNCTION(foo, zoo);" to
56//           effectively redirect calls from "foo" to "zoo". In this case
57//           you aren't required to implement
58//           INTERCEPTOR(int, foo, const char *bar, double baz);
59//           but instead you'll have to add
60//           DEFINE_REAL(int, foo, const char *bar, double baz); in your
61//           source file (to define a pointer to overriden function).
62
63// How it works:
64// To replace weak system functions on Linux we just need to declare functions
65// with same names in our library and then obtain the real function pointers
66// using dlsym(). This is not so on Mac OS, where the two-level namespace makes
67// our replacement functions invisible to other libraries. This may be overcomed
68// using the DYLD_FORCE_FLAT_NAMESPACE, but some errors loading the shared
69// libraries in Chromium were noticed when doing so.
70// Instead we use mach_override, a handy framework for patching functions at
71// runtime. To avoid possible name clashes, our replacement functions have
72// the "wrap_" prefix on Mac.
73
74#if defined(__APPLE__)
75# define WRAP(x) wrap_##x
76# define WRAPPER_NAME(x) "wrap_"#x
77# define INTERCEPTOR_ATTRIBUTE
78#elif defined(_WIN32)
79// TODO(timurrrr): we're likely to use something else later on Windows.
80# define WRAP(x) wrap_##x
81# define WRAPPER_NAME(x) #x
82# define INTERCEPTOR_ATTRIBUTE
83#else
84# define WRAP(x) x
85# define WRAPPER_NAME(x) #x
86# define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default")))
87#endif
88
89#define PTR_TO_REAL(x) real_##x
90#define REAL(x) __interception::PTR_TO_REAL(x)
91#define FUNC_TYPE(x) x##_f
92
93#define DECLARE_REAL(ret_type, func, ...); \
94  typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \
95  namespace __interception { \
96    extern FUNC_TYPE(func) PTR_TO_REAL(func); \
97  }
98
99#define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...); \
100  DECLARE_REAL(ret_type, func, ##__VA_ARGS__); \
101  extern "C" ret_type WRAP(func)(__VA_ARGS__);
102
103// Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR
104// macros does its job. In exceptional cases you may need to call REAL(foo)
105// without defining INTERCEPTOR(..., foo, ...). For example, if you override
106// foo with an interceptor for other function.
107#define DEFINE_REAL(ret_type, func, ...); \
108  typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \
109  namespace __interception { \
110    FUNC_TYPE(func) PTR_TO_REAL(func); \
111  }
112
113#define INTERCEPTOR(ret_type, func, ...) \
114  DEFINE_REAL(ret_type, func, __VA_ARGS__); \
115  extern "C" \
116  INTERCEPTOR_ATTRIBUTE \
117  ret_type WRAP(func)(__VA_ARGS__)
118
119#define INCLUDED_FROM_INTERCEPTION_LIB
120
121#if defined(__linux__)
122# include "interception_linux.h"
123# define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_LINUX(func)
124#elif defined(__APPLE__)
125# include "interception_mac.h"
126# define OVERRIDE_FUNCTION(old_func, new_func) \
127    OVERRIDE_FUNCTION_MAC(old_func, new_func)
128# define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_MAC(func)
129#else  // defined(_WIN32)
130  // FIXME: deal with interception on Win.
131# define INTERCEPT_FUNCTON(func) true
132#endif
133
134#undef INCLUDED_FROM_INTERCEPTION_LIB
135
136#endif  // INTERCEPTION_H
137