1//=== FuzzerExtWindows.cpp - Interface to external functions --------------===//
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// Implementation of FuzzerExtFunctions for Windows. Uses alternatename when
9// compiled with MSVC. Uses weak aliases when compiled with clang. Unfortunately
10// the method each compiler supports is not supported by the other.
11//===----------------------------------------------------------------------===//
12#include "FuzzerPlatform.h"
13#if LIBFUZZER_WINDOWS
14
15#include "FuzzerExtFunctions.h"
16#include "FuzzerIO.h"
17#include <stdlib.h>
18
19using namespace fuzzer;
20
21// Intermediate macro to ensure the parameter is expanded before stringified.
22#define STRINGIFY_(A) #A
23#define STRINGIFY(A) STRINGIFY_(A)
24
25#if LIBFUZZER_MSVC
26#define GET_FUNCTION_ADDRESS(fn) &fn
27#else
28#define GET_FUNCTION_ADDRESS(fn) __builtin_function_start(fn)
29#endif // LIBFUZER_MSVC
30
31// Copied from compiler-rt/lib/sanitizer_common/sanitizer_win_defs.h
32#if defined(_M_IX86) || defined(__i386__)
33#define WIN_SYM_PREFIX "_"
34#else
35#define WIN_SYM_PREFIX
36#endif
37
38// Declare external functions as having alternativenames, so that we can
39// determine if they are not defined.
40#define EXTERNAL_FUNC(Name, Default) \
41 __pragma(comment(linker, "/alternatename:" WIN_SYM_PREFIX STRINGIFY( \
42 Name) "=" WIN_SYM_PREFIX STRINGIFY(Default)))
43
44extern "C" {
45#define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN) \
46 RETURN_TYPE NAME##Def FUNC_SIG { \
47 Printf("ERROR: Function \"%s\" not defined.\n", #NAME); \
48 exit(1); \
49 } \
50 EXTERNAL_FUNC(NAME, NAME##Def) RETURN_TYPE NAME FUNC_SIG
51
52#include "FuzzerExtFunctions.def"
53
54#undef EXT_FUNC
55}
56
57template <typename T>
58static T *GetFnPtr(void *Fun, void *FunDef, const char *FnName,
59 bool WarnIfMissing) {
60 if (Fun == FunDef) {
61 if (WarnIfMissing)
62 Printf("WARNING: Failed to find function \"%s\".\n", FnName);
63 return nullptr;
64 }
65 return (T *)Fun;
66}
67
68namespace fuzzer {
69
70ExternalFunctions::ExternalFunctions() {
71#define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN) \
72 this->NAME = GetFnPtr<decltype(::NAME)>(GET_FUNCTION_ADDRESS(::NAME), \
73 GET_FUNCTION_ADDRESS(::NAME##Def), \
74 #NAME, WARN);
75
76#include "FuzzerExtFunctions.def"
77
78#undef EXT_FUNC
79}
80
81} // namespace fuzzer
82
83#endif // LIBFUZZER_WINDOWS
84