blob: d05052370748d3e99a8d125d6c74f313ebbbbd3f [file] [log] [blame]
//===-- interception.h ------------------------------------------*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file is a part of AddressSanitizer, an address sanity checker.
// Machinery for providing replacements/wrappers for system functions.
#if !defined(__linux__) && !defined(__APPLE__) && !defined(_WIN32)
# error "Interception doesn't work on this operating system."
// How to use this library:
// 1) Include this header to define your own interceptors
// (see details below).
// 2) Build all *.cc files and link against them.
// On Mac you will also need to:
// 3) Provide your own implementation for the following functions:
// mach_error_t __interception::allocate_island(void **ptr,
// size_t size,
// void *hint);
// mach_error_t __interception::deallocate_island(void *ptr);
// See "interception_mac.h" for more details.
// How to add an interceptor:
// Suppose you need to wrap/replace system function (generally, from libc):
// int foo(const char *bar, double baz);
// You'll need to:
// 1) define INTERCEPTOR(int, foo, const char *bar, double baz) { ... } in
// your source file.
// 2) Call "INTERCEPT_FUNCTION(foo)" prior to the first call of "foo".
// INTERCEPT_FUNCTION(foo) evaluates to "true" iff the function was
// intercepted successfully.
// You can access original function by calling REAL(foo)(bar, baz).
// By default, REAL(foo) will be visible only inside your interceptor, and if
// you want to use it in other parts of RTL, you'll need to:
// 3a) add DECLARE_REAL(int, foo, const char*, double) to a
// header file.
// However, if the call "INTERCEPT_FUNCTION(foo)" and definition for
// INTERCEPTOR(..., foo, ...) are in different files, you'll instead need to:
// 3b) add DECLARE_REAL_AND_INTERCEPTOR(int, foo, const char*, double)
// to a header file.
// Notes: 1. Things may not work properly if macro INTERCEPT(...) {...} or
// DECLARE_REAL(...) are located inside namespaces.
// 2. On Mac you can also use: "OVERRIDE_FUNCTION(foo, zoo);" to
// effectively redirect calls from "foo" to "zoo". In this case
// you aren't required to implement
// INTERCEPTOR(int, foo, const char *bar, double baz) {...}
// but instead you'll have to add
// DEFINE_REAL(int, foo, const char *bar, double baz) in your
// source file (to define a pointer to overriden function).
// How it works:
// To replace system functions on Linux we just need to declare functions
// with same names in our library and then obtain the real function pointers
// using dlsym().
// There is one complication. A user may also intercept some of the functions
// we intercept. To resolve this we declare our interceptors with __interceptor_
// prefix, and then make actual interceptors weak aliases to __interceptor_
// functions.
// This is not so on Mac OS, where the two-level namespace makes
// our replacement functions invisible to other libraries. This may be overcomed
// using the DYLD_FORCE_FLAT_NAMESPACE, but some errors loading the shared
// libraries in Chromium were noticed when doing so. Instead we use
// mach_override, a handy framework for patching functions at runtime.
// To avoid possible name clashes, our replacement functions have
// the "wrap_" prefix on Mac.
#if defined(__APPLE__)
# define WRAP(x) wrap_##x
# define WRAPPER_NAME(x) "wrap_"#x
# define DECLARE_WRAPPER(ret_type, convention, func, ...)
#elif defined(_WIN32)
# if defined(_DLL) // DLL CRT
# define WRAP(x) x
# define WRAPPER_NAME(x) #x
# else // Static CRT
# define WRAP(x) wrap_##x
# define WRAPPER_NAME(x) "wrap_"#x
# endif
# define DECLARE_WRAPPER(ret_type, convention, func, ...)
# define WRAP(x) __interceptor_ ## x
# define WRAPPER_NAME(x) "__interceptor_" #x
# define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default")))
# define DECLARE_WRAPPER(ret_type, convention, func, ...) \
extern "C" ret_type convention func(__VA_ARGS__) \
__attribute__((weak, alias("__interceptor_" #func), visibility("default")));
#define PTR_TO_REAL(x) real_##x
#define REAL(x) __interception::PTR_TO_REAL(x)
#define FUNC_TYPE(x) x##_f
#define DECLARE_REAL(ret_type, func, ...) \
typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \
namespace __interception { \
extern FUNC_TYPE(func) PTR_TO_REAL(func); \
#define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) \
DECLARE_REAL(ret_type, func, ##__VA_ARGS__) \
extern "C" ret_type WRAP(func)(__VA_ARGS__);
// FIXME(timurrrr): We might need to add DECLARE_REAL_EX etc to support
// different calling conventions later.
#define DEFINE_REAL_EX(ret_type, convention, func, ...) \
typedef ret_type (convention *FUNC_TYPE(func))(__VA_ARGS__); \
namespace __interception { \
FUNC_TYPE(func) PTR_TO_REAL(func); \
// Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR
// macros does its job. In exceptional cases you may need to call REAL(foo)
// without defining INTERCEPTOR(..., foo, ...). For example, if you override
// foo with an interceptor for other function.
#define DEFINE_REAL(ret_type, func, ...) \
#define INTERCEPTOR_EX(ret_type, convention, func, ...) \
DEFINE_REAL_EX(ret_type, convention, func, __VA_ARGS__) \
DECLARE_WRAPPER(ret_type, convention, func, __VA_ARGS__) \
extern "C" \
ret_type convention WRAP(func)(__VA_ARGS__)
#define INTERCEPTOR(ret_type, func, ...) \
#if defined(_WIN32)
# define INTERCEPTOR_WINAPI(ret_type, func, ...) \
INTERCEPTOR_EX(ret_type, __stdcall, func, __VA_ARGS__)
// ISO C++ forbids casting between pointer-to-function and pointer-to-object,
// so we use casting via an integral type __interception::uptr,
// assuming that system is POSIX-compliant. Using other hacks seem
// challenging, as we don't even pass function type to
// INTERCEPT_FUNCTION macro, only its name.
namespace __interception {
typedef unsigned long uptr; // NOLINT
} // namespace __interception
#if defined(__linux__)
# include "interception_linux.h"
#elif defined(__APPLE__)
# include "interception_mac.h"
# define OVERRIDE_FUNCTION(old_func, new_func) \
OVERRIDE_FUNCTION_MAC(old_func, new_func)
#else // defined(_WIN32)
# include "interception_win.h"