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)
28typedef __sanitizer::uptr SIZE_T;
29typedef __sanitizer::sptr SSIZE_T;
30typedef __sanitizer::sptr PTRDIFF_T;
31typedef __sanitizer::s64 INTMAX_T;
32typedef __sanitizer::u64 UINTMAX_T;
33typedef __sanitizer::OFF_T OFF_T;
34typedef __sanitizer::OFF64_T OFF64_T;
35
36// How to add an interceptor:
37// Suppose you need to wrap/replace system function (generally, from libc):
38// int foo(const char *bar, double baz);
39// You'll need to:
40// 1) define INTERCEPTOR(int, foo, const char *bar, double baz) { ... } in
41// your source file. See the notes below for cases when
42// INTERCEPTOR_WITH_SUFFIX(...) should be used instead.
43// 2) Call "INTERCEPT_FUNCTION(foo)" prior to the first call of "foo".
44// INTERCEPT_FUNCTION(foo) evaluates to "true" iff the function was
45// intercepted successfully.
46// You can access original function by calling REAL(foo)(bar, baz).
47// By default, REAL(foo) will be visible only inside your interceptor, and if
48// you want to use it in other parts of RTL, you'll need to:
49// 3a) add DECLARE_REAL(int, foo, const char*, double) to a
50// header file.
51// However, if the call "INTERCEPT_FUNCTION(foo)" and definition for
52// INTERCEPTOR(..., foo, ...) are in different files, you'll instead need to:
53// 3b) add DECLARE_REAL_AND_INTERCEPTOR(int, foo, const char*, double)
54// to a header file.
55
56// Notes: 1. Things may not work properly if macro INTERCEPTOR(...) {...} or
57// DECLARE_REAL(...) are located inside namespaces.
58// 2. On Mac you can also use: "OVERRIDE_FUNCTION(foo, zoo)" to
59// effectively redirect calls from "foo" to "zoo". In this case
60// you aren't required to implement
61// INTERCEPTOR(int, foo, const char *bar, double baz) {...}
62// but instead you'll have to add
63// DECLARE_REAL(int, foo, const char *bar, double baz) in your
64// source file (to define a pointer to overriden function).
65// 3. Some Mac functions have symbol variants discriminated by
66// additional suffixes, e.g. _$UNIX2003 (see
67// https://developer.apple.com/library/mac/#releasenotes/Darwin/SymbolVariantsRelNotes/index.html
68// for more details). To intercept such functions you need to use the
69// INTERCEPTOR_WITH_SUFFIX(...) macro.
70
71// How it works on Linux
72// ---------------------
73//
74// To replace system functions on Linux we just need to declare functions with
75// the same names in our library and then obtain the real function pointers
76// using dlsym().
77//
78// There is one complication: a user may also intercept some of the functions we
79// intercept. To allow for up to 3 interceptors (including ours) of a given
80// function "func", the interceptor implementation is in ___interceptor_func,
81// which is aliased by a weak function __interceptor_func, which in turn is
82// aliased (via a trampoline) by weak wrapper function "func".
83//
84// Most user interceptors should define a foreign interceptor as follows:
85//
86// - provide a non-weak function "func" that performs interception;
87// - if __interceptor_func exists, call it to perform the real functionality;
88// - if it does not exist, figure out the real function and call it instead.
89//
90// In rare cases, a foreign interceptor (of another dynamic analysis runtime)
91// may be defined as follows (on supported architectures):
92//
93// - provide a non-weak function __interceptor_func that performs interception;
94// - if ___interceptor_func exists, call it to perform the real functionality;
95// - if it does not exist, figure out the real function and call it instead;
96// - provide a weak function "func" that is an alias to __interceptor_func.
97//
98// With this protocol, sanitizer interceptors, foreign user interceptors, and
99// foreign interceptors of other dynamic analysis runtimes, or any combination
100// thereof, may co-exist simultaneously.
101//
102// How it works on Mac OS
103// ----------------------
104//
105// This is not so on Mac OS, where the two-level namespace makes our replacement
106// functions invisible to other libraries. This may be overcomed using the
107// DYLD_FORCE_FLAT_NAMESPACE, but some errors loading the shared libraries in
108// Chromium were noticed when doing so.
109//
110// Instead we create a dylib containing a __DATA,__interpose section that
111// associates library functions with their wrappers. When this dylib is
112// preloaded before an executable using DYLD_INSERT_LIBRARIES, it routes all the
113// calls to interposed functions done through stubs to the wrapper functions.
114//
115// As it's decided at compile time which functions are to be intercepted on Mac,
116// INTERCEPT_FUNCTION() is effectively a no-op on this system.
117
118#if SANITIZER_APPLE
119#include <sys/cdefs.h> // For __DARWIN_ALIAS_C().
120
121// Just a pair of pointers.
122struct interpose_substitution {
123 const __sanitizer::uptr replacement;
124 const __sanitizer::uptr original;
125};
126
127// For a function foo() create a global pair of pointers { wrap_foo, foo } in
128// the __DATA,__interpose section.
129// As a result all the calls to foo() will be routed to wrap_foo() at runtime.
130#define INTERPOSER(func_name) __attribute__((used)) \
131const interpose_substitution substitution_##func_name[] \
132 __attribute__((section("__DATA, __interpose"))) = { \
133 { reinterpret_cast<const uptr>(WRAP(func_name)), \
134 reinterpret_cast<const uptr>(func_name) } \
135}
136
137// For a function foo() and a wrapper function bar() create a global pair
138// of pointers { bar, foo } in the __DATA,__interpose section.
139// As a result all the calls to foo() will be routed to bar() at runtime.
140#define INTERPOSER_2(func_name, wrapper_name) __attribute__((used)) \
141const interpose_substitution substitution_##func_name[] \
142 __attribute__((section("__DATA, __interpose"))) = { \
143 { reinterpret_cast<const uptr>(wrapper_name), \
144 reinterpret_cast<const uptr>(func_name) } \
145}
146
147# define WRAP(x) wrap_##x
148# define TRAMPOLINE(x) WRAP(x)
149# define INTERCEPTOR_ATTRIBUTE
150# define DECLARE_WRAPPER(ret_type, func, ...)
151
152#elif SANITIZER_WINDOWS
153# define WRAP(x) __asan_wrap_##x
154# define TRAMPOLINE(x) WRAP(x)
155# define INTERCEPTOR_ATTRIBUTE __declspec(dllexport)
156# define DECLARE_WRAPPER(ret_type, func, ...) \
157 extern "C" ret_type func(__VA_ARGS__);
158# define DECLARE_WRAPPER_WINAPI(ret_type, func, ...) \
159 extern "C" __declspec(dllimport) ret_type __stdcall func(__VA_ARGS__);
160#elif !SANITIZER_FUCHSIA // LINUX, FREEBSD, NETBSD, SOLARIS
161# define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default")))
162# if ASM_INTERCEPTOR_TRAMPOLINE_SUPPORT
163// Weak aliases of weak aliases do not work, therefore we need to set up a
164// trampoline function. The function "func" is a weak alias to the trampoline
165// (so that we may check if "func" was overridden), which calls the weak
166// function __interceptor_func, which in turn aliases the actual interceptor
167// implementation ___interceptor_func:
168//
169// [wrapper "func": weak] --(alias)--> [TRAMPOLINE(func)]
170// |
171// +--------(tail call)-------+
172// |
173// v
174// [__interceptor_func: weak] --(alias)--> [WRAP(func)]
175//
176// We use inline assembly to define most of this, because not all compilers
177// support functions with the "naked" attribute with every architecture.
178# define WRAP(x) ___interceptor_ ## x
179# define TRAMPOLINE(x) __interceptor_trampoline_ ## x
180# if SANITIZER_FREEBSD || SANITIZER_NETBSD
181// FreeBSD's dynamic linker (incompliantly) gives non-weak symbols higher
182// priority than weak ones so weak aliases won't work for indirect calls
183// in position-independent (-fPIC / -fPIE) mode.
184# define __ASM_WEAK_WRAPPER(func) ".globl " #func "\n"
185# else
186# define __ASM_WEAK_WRAPPER(func) ".weak " #func "\n"
187# endif // SANITIZER_FREEBSD || SANITIZER_NETBSD
188# if defined(__arm__) || defined(__aarch64__)
189# define ASM_TYPE_FUNCTION_STR "%function"
190# else
191# define ASM_TYPE_FUNCTION_STR "@function"
192# endif
193// Keep trampoline implementation in sync with sanitizer_common/sanitizer_asm.h
194# define DECLARE_WRAPPER(ret_type, func, ...) \
195 extern "C" ret_type func(__VA_ARGS__); \
196 extern "C" ret_type TRAMPOLINE(func)(__VA_ARGS__); \
197 extern "C" ret_type __interceptor_##func(__VA_ARGS__) \
198 INTERCEPTOR_ATTRIBUTE __attribute__((weak)) ALIAS(WRAP(func)); \
199 asm( \
200 ".text\n" \
201 __ASM_WEAK_WRAPPER(func) \
202 ".set " #func ", " SANITIZER_STRINGIFY(TRAMPOLINE(func)) "\n" \
203 ".globl " SANITIZER_STRINGIFY(TRAMPOLINE(func)) "\n" \
204 ".type " SANITIZER_STRINGIFY(TRAMPOLINE(func)) ", " \
205 ASM_TYPE_FUNCTION_STR "\n" \
206 SANITIZER_STRINGIFY(TRAMPOLINE(func)) ":\n" \
207 C_ASM_STARTPROC "\n" \
208 C_ASM_TAIL_CALL(SANITIZER_STRINGIFY(TRAMPOLINE(func)), \
209 "__interceptor_" \
210 SANITIZER_STRINGIFY(ASM_PREEMPTIBLE_SYM(func))) "\n" \
211 C_ASM_ENDPROC "\n" \
212 ".size " SANITIZER_STRINGIFY(TRAMPOLINE(func)) ", " \
213 ".-" SANITIZER_STRINGIFY(TRAMPOLINE(func)) "\n" \
214 );
215# else // ASM_INTERCEPTOR_TRAMPOLINE_SUPPORT
216// Some architectures cannot implement efficient interceptor trampolines with
217// just a plain jump due to complexities of resolving a preemptible symbol. In
218// those cases, revert to just this scheme:
219//
220// [wrapper "func": weak] --(alias)--> [WRAP(func)]
221//
222# define WRAP(x) __interceptor_ ## x
223# define TRAMPOLINE(x) WRAP(x)
224# if SANITIZER_FREEBSD || SANITIZER_NETBSD
225# define __ATTRIBUTE_WEAK_WRAPPER
226# else
227# define __ATTRIBUTE_WEAK_WRAPPER __attribute__((weak))
228# endif // SANITIZER_FREEBSD || SANITIZER_NETBSD
229# define DECLARE_WRAPPER(ret_type, func, ...) \
230 extern "C" ret_type func(__VA_ARGS__) \
231 INTERCEPTOR_ATTRIBUTE __ATTRIBUTE_WEAK_WRAPPER ALIAS(WRAP(func));
232# endif // ASM_INTERCEPTOR_TRAMPOLINE_SUPPORT
233#endif
234
235#if SANITIZER_FUCHSIA
236// There is no general interception at all on Fuchsia.
237// Sanitizer runtimes just define functions directly to preempt them,
238// and have bespoke ways to access the underlying libc functions.
239# include <zircon/sanitizer.h>
240# define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default")))
241# define REAL(x) __unsanitized_##x
242# define DECLARE_REAL(ret_type, func, ...)
243#elif !SANITIZER_APPLE
244# define PTR_TO_REAL(x) real_##x
245# define REAL(x) __interception::PTR_TO_REAL(x)
246# define FUNC_TYPE(x) x##_type
247
248# define DECLARE_REAL(ret_type, func, ...) \
249 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \
250 namespace __interception { \
251 extern FUNC_TYPE(func) PTR_TO_REAL(func); \
252 }
253# define ASSIGN_REAL(dst, src) REAL(dst) = REAL(src)
254#else // SANITIZER_APPLE
255# define REAL(x) x
256# define DECLARE_REAL(ret_type, func, ...) \
257 extern "C" ret_type func(__VA_ARGS__);
258# define ASSIGN_REAL(x, y)
259#endif // SANITIZER_APPLE
260
261#if !SANITIZER_FUCHSIA
262# define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) \
263 DECLARE_REAL(ret_type, func, __VA_ARGS__) \
264 extern "C" ret_type TRAMPOLINE(func)(__VA_ARGS__); \
265 extern "C" ret_type WRAP(func)(__VA_ARGS__);
266// Declare an interceptor and its wrapper defined in a different translation
267// unit (ex. asm).
268# define DECLARE_EXTERN_INTERCEPTOR_AND_WRAPPER(ret_type, func, ...) \
269 extern "C" ret_type TRAMPOLINE(func)(__VA_ARGS__); \
270 extern "C" ret_type WRAP(func)(__VA_ARGS__); \
271 extern "C" ret_type func(__VA_ARGS__);
272#else
273# define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...)
274# define DECLARE_EXTERN_INTERCEPTOR_AND_WRAPPER(ret_type, func, ...)
275#endif
276
277// Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR
278// macros does its job. In exceptional cases you may need to call REAL(foo)
279// without defining INTERCEPTOR(..., foo, ...). For example, if you override
280// foo with an interceptor for other function.
281#if !SANITIZER_APPLE && !SANITIZER_FUCHSIA
282# define DEFINE_REAL(ret_type, func, ...) \
283 typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \
284 namespace __interception { \
285 FUNC_TYPE(func) PTR_TO_REAL(func); \
286 }
287#else
288# define DEFINE_REAL(ret_type, func, ...)
289#endif
290
291#if SANITIZER_FUCHSIA
292
293// We need to define the __interceptor_func name just to get
294// sanitizer_common/scripts/gen_dynamic_list.py to export func.
295// But we don't need to export __interceptor_func to get that.
296#define INTERCEPTOR(ret_type, func, ...) \
297 extern "C"[[ gnu::alias(#func), gnu::visibility("hidden") ]] ret_type \
298 __interceptor_##func(__VA_ARGS__); \
299 extern "C" INTERCEPTOR_ATTRIBUTE ret_type func(__VA_ARGS__)
300
301#elif !SANITIZER_APPLE
302
303#define INTERCEPTOR(ret_type, func, ...) \
304 DEFINE_REAL(ret_type, func, __VA_ARGS__) \
305 DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \
306 extern "C" INTERCEPTOR_ATTRIBUTE ret_type WRAP(func)(__VA_ARGS__)
307
308// We don't need INTERCEPTOR_WITH_SUFFIX on non-Darwin for now.
309#define INTERCEPTOR_WITH_SUFFIX(ret_type, func, ...) \
310 INTERCEPTOR(ret_type, func, __VA_ARGS__)
311
312#else // SANITIZER_APPLE
313
314#define INTERCEPTOR_ZZZ(suffix, ret_type, func, ...) \
315 extern "C" ret_type func(__VA_ARGS__) suffix; \
316 extern "C" ret_type WRAP(func)(__VA_ARGS__); \
317 INTERPOSER(func); \
318 extern "C" INTERCEPTOR_ATTRIBUTE ret_type WRAP(func)(__VA_ARGS__)
319
320#define INTERCEPTOR(ret_type, func, ...) \
321 INTERCEPTOR_ZZZ(/*no symbol variants*/, ret_type, func, __VA_ARGS__)
322
323#define INTERCEPTOR_WITH_SUFFIX(ret_type, func, ...) \
324 INTERCEPTOR_ZZZ(__DARWIN_ALIAS_C(func), ret_type, func, __VA_ARGS__)
325
326// Override |overridee| with |overrider|.
327#define OVERRIDE_FUNCTION(overridee, overrider) \
328 INTERPOSER_2(overridee, WRAP(overrider))
329#endif
330
331#if SANITIZER_WINDOWS
332# define INTERCEPTOR_WINAPI(ret_type, func, ...) \
333 typedef ret_type (__stdcall *FUNC_TYPE(func))(__VA_ARGS__); \
334 namespace __interception { \
335 FUNC_TYPE(func) PTR_TO_REAL(func); \
336 } \
337 extern "C" INTERCEPTOR_ATTRIBUTE ret_type __stdcall WRAP(func)(__VA_ARGS__)
338#endif
339
340// ISO C++ forbids casting between pointer-to-function and pointer-to-object,
341// so we use casting via an integral type __interception::uptr,
342// assuming that system is POSIX-compliant. Using other hacks seem
343// challenging, as we don't even pass function type to
344// INTERCEPT_FUNCTION macro, only its name.
345namespace __interception {
346#if defined(_WIN64)
347typedef unsigned long long uptr;
348#else
349typedef unsigned long uptr;
350#endif // _WIN64
351
352#if defined(__ELF__) && !SANITIZER_FUCHSIA
353// The use of interceptors makes many sanitizers unusable for static linking.
354// Define a function, if called, will cause a linker error (undefined _DYNAMIC).
355// However, -static-pie (which is not common) cannot be detected at link time.
356extern uptr kDynamic[] asm("_DYNAMIC");
357inline void DoesNotSupportStaticLinking() {
358 [[maybe_unused]] volatile auto x = &kDynamic;
359}
360#else
361inline void DoesNotSupportStaticLinking() {}
362#endif
363} // namespace __interception
364
365#define INCLUDED_FROM_INTERCEPTION_LIB
366
367#if SANITIZER_LINUX || SANITIZER_FREEBSD || SANITIZER_NETBSD || \
368 SANITIZER_SOLARIS
369
370# include "interception_linux.h"
371# define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_LINUX_OR_FREEBSD(func)
372# define INTERCEPT_FUNCTION_VER(func, symver) \
373 INTERCEPT_FUNCTION_VER_LINUX_OR_FREEBSD(func, symver)
374#elif SANITIZER_APPLE
375# include "interception_mac.h"
376# define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_MAC(func)
377# define INTERCEPT_FUNCTION_VER(func, symver) \
378 INTERCEPT_FUNCTION_VER_MAC(func, symver)
379#elif SANITIZER_WINDOWS
380# include "interception_win.h"
381# define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_WIN(func)
382# define INTERCEPT_FUNCTION_VER(func, symver) \
383 INTERCEPT_FUNCTION_VER_WIN(func, symver)
384#endif
385
386#undef INCLUDED_FROM_INTERCEPTION_LIB
387
388#endif // INTERCEPTION_H
389

source code of compiler-rt/lib/interception/interception.h