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//===-- 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(__FreeBSD__) && \
!defined(__APPLE__) && !defined(_WIN32)
# error "Interception doesn't work on this operating system."
#include "sanitizer_common/sanitizer_internal_defs.h"
// These typedefs should be used only in the interceptor definitions to replace
// the standard system types (e.g. SSIZE_T instead of ssize_t)
typedef __sanitizer::uptr SIZE_T;
typedef __sanitizer::sptr SSIZE_T;
typedef __sanitizer::sptr PTRDIFF_T;
typedef __sanitizer::s64 INTMAX_T;
typedef __sanitizer::OFF_T OFF_T;
typedef __sanitizer::OFF64_T OFF64_T;
// 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. See the notes below for cases when
// INTERCEPTOR_WITH_SUFFIX(...) should be used instead.
// 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 INTERCEPTOR(...) {...} 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
// DECLARE_REAL(int, foo, const char *bar, double baz) in your
// source file (to define a pointer to overriden function).
// 3. Some Mac functions have symbol variants discriminated by
// additional suffixes, e.g. _$UNIX2003 (see
// for more details). To intercept such functions you need to use the
// 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 create a dylib containing a __DATA,__interpose section that
// associates library functions with their wrappers. When this dylib is
// preloaded before an executable using DYLD_INSERT_LIBRARIES, it routes all
// the calls to interposed functions done through stubs to the wrapper
// functions.
// As it's decided at compile time which functions are to be intercepted on Mac,
// INTERCEPT_FUNCTION() is effectively a no-op on this system.
#if defined(__APPLE__)
#include <sys/cdefs.h> // For __DARWIN_ALIAS_C().
// Just a pair of pointers.
struct interpose_substitution {
const uptr replacement;
const uptr original;
// For a function foo() create a global pair of pointers { wrap_foo, foo } in
// the __DATA,__interpose section.
// As a result all the calls to foo() will be routed to wrap_foo() at runtime.
#define INTERPOSER(func_name) __attribute__((used)) \
const interpose_substitution substitution_##func_name[] \
__attribute__((section("__DATA, __interpose"))) = { \
{ reinterpret_cast<const uptr>(WRAP(func_name)), \
reinterpret_cast<const uptr>(func_name) } \
// For a function foo() and a wrapper function bar() create a global pair
// of pointers { bar, foo } in the __DATA,__interpose section.
// As a result all the calls to foo() will be routed to bar() at runtime.
#define INTERPOSER_2(func_name, wrapper_name) __attribute__((used)) \
const interpose_substitution substitution_##func_name[] \
__attribute__((section("__DATA, __interpose"))) = { \
{ reinterpret_cast<const uptr>(wrapper_name), \
reinterpret_cast<const uptr>(func_name) } \
# define WRAP(x) wrap_##x
# define WRAPPER_NAME(x) "wrap_"#x
# define DECLARE_WRAPPER(ret_type, func, ...)
#elif defined(_WIN32)
# define WRAP(x) __asan_wrap_##x
# define WRAPPER_NAME(x) "__asan_wrap_"#x
# define INTERCEPTOR_ATTRIBUTE __declspec(dllexport)
# define DECLARE_WRAPPER(ret_type, func, ...) \
extern "C" ret_type func(__VA_ARGS__);
# define DECLARE_WRAPPER_WINAPI(ret_type, func, ...) \
extern "C" __declspec(dllimport) ret_type __stdcall func(__VA_ARGS__);
#elif defined(__FreeBSD__)
# define WRAP(x) __interceptor_ ## x
# define WRAPPER_NAME(x) "__interceptor_" #x
# define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default")))
// FreeBSD's dynamic linker (incompliantly) gives non-weak symbols higher
// priority than weak ones so weak aliases won't work for indirect calls
// in position-independent (-fPIC / -fPIE) mode.
# define DECLARE_WRAPPER(ret_type, func, ...) \
extern "C" ret_type func(__VA_ARGS__) \
__attribute__((alias("__interceptor_" #func), visibility("default")));
# define WRAP(x) __interceptor_ ## x
# define WRAPPER_NAME(x) "__interceptor_" #x
# define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default")))
# define DECLARE_WRAPPER(ret_type, func, ...) \
extern "C" ret_type func(__VA_ARGS__) \
__attribute__((weak, alias("__interceptor_" #func), visibility("default")));
#if !defined(__APPLE__)
# 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); \
#else // __APPLE__
# define REAL(x) x
# define DECLARE_REAL(ret_type, func, ...) \
extern "C" ret_type func(__VA_ARGS__);
#endif // __APPLE__
#define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) \
DECLARE_REAL(ret_type, func, __VA_ARGS__) \
extern "C" ret_type WRAP(func)(__VA_ARGS__);
// 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.
#if !defined(__APPLE__)
# define DEFINE_REAL(ret_type, func, ...) \
typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \
namespace __interception { \
FUNC_TYPE(func) PTR_TO_REAL(func); \
# define DEFINE_REAL(ret_type, func, ...)
#if !defined(__APPLE__)
#define INTERCEPTOR(ret_type, func, ...) \
DEFINE_REAL(ret_type, func, __VA_ARGS__) \
DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \
extern "C" \
ret_type WRAP(func)(__VA_ARGS__)
// We don't need INTERCEPTOR_WITH_SUFFIX on non-Darwin for now.
#define INTERCEPTOR_WITH_SUFFIX(ret_type, func, ...) \
INTERCEPTOR(ret_type, func, __VA_ARGS__)
#else // __APPLE__
#define INTERCEPTOR_ZZZ(suffix, ret_type, func, ...) \
extern "C" ret_type func(__VA_ARGS__) suffix; \
extern "C" ret_type WRAP(func)(__VA_ARGS__); \
extern "C" INTERCEPTOR_ATTRIBUTE ret_type WRAP(func)(__VA_ARGS__)
#define INTERCEPTOR(ret_type, func, ...) \
INTERCEPTOR_ZZZ(/*no symbol variants*/, ret_type, func, __VA_ARGS__)
#define INTERCEPTOR_WITH_SUFFIX(ret_type, func, ...) \
INTERCEPTOR_ZZZ(__DARWIN_ALIAS_C(func), ret_type, func, __VA_ARGS__)
// Override |overridee| with |overrider|.
#define OVERRIDE_FUNCTION(overridee, overrider) \
INTERPOSER_2(overridee, WRAP(overrider))
#if defined(_WIN32)
# define INTERCEPTOR_WINAPI(ret_type, func, ...) \
typedef ret_type (__stdcall *FUNC_TYPE(func))(__VA_ARGS__); \
namespace __interception { \
FUNC_TYPE(func) PTR_TO_REAL(func); \
} \
extern "C" \
ret_type __stdcall WRAP(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 {
#if defined(_WIN64)
typedef unsigned long long uptr; // NOLINT
typedef unsigned long uptr; // NOLINT
#endif // _WIN64
} // namespace __interception
#if defined(__linux__) || defined(__FreeBSD__)
# include "interception_linux.h"
# define INTERCEPT_FUNCTION_VER(func, symver) \
#elif defined(__APPLE__)
# include "interception_mac.h"
# define INTERCEPT_FUNCTION_VER(func, symver) \
#else // defined(_WIN32)
# include "interception_win.h"
# define INTERCEPT_FUNCTION_VER(func, symver) \