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 "FuzzerDefs.h" 13#if LIBFUZZER_WINDOWS 14 15#include "FuzzerExtFunctions.h" 16#include "FuzzerIO.h" 17 18using namespace fuzzer; 19 20// Intermediate macro to ensure the parameter is expanded before stringified. 21#define STRINGIFY_(A) #A 22#define STRINGIFY(A) STRINGIFY_(A) 23 24#if LIBFUZZER_MSVC 25// Copied from compiler-rt/lib/sanitizer_common/sanitizer_win_defs.h 26#if defined(_M_IX86) || defined(__i386__) 27#define WIN_SYM_PREFIX "_" 28#else 29#define WIN_SYM_PREFIX 30#endif 31 32// Declare external functions as having alternativenames, so that we can 33// determine if they are not defined. 34#define EXTERNAL_FUNC(Name, Default) \ 35 __pragma(comment(linker, "/alternatename:" WIN_SYM_PREFIX STRINGIFY( \ 36 Name) "=" WIN_SYM_PREFIX STRINGIFY(Default))) 37#else 38// Declare external functions as weak to allow them to default to a specified 39// function if not defined explicitly. We must use weak symbols because clang's 40// support for alternatename is not 100%, see 41// https://bugs.llvm.org/show_bug.cgi?id=40218 for more details. 42#define EXTERNAL_FUNC(Name, Default) \ 43 __attribute__((weak, alias(STRINGIFY(Default)))) 44#endif // LIBFUZZER_MSVC 45 46extern "C" { 47#define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN) \ 48 RETURN_TYPE NAME##Def FUNC_SIG { \ 49 Printf("ERROR: Function \"%s\" not defined.\n", #NAME); \ 50 exit(1); \ 51 } \ 52 EXTERNAL_FUNC(NAME, NAME##Def) RETURN_TYPE NAME FUNC_SIG 53 54#include "FuzzerExtFunctions.def" 55 56#undef EXT_FUNC 57} 58 59template <typename T> 60static T *GetFnPtr(T *Fun, T *FunDef, const char *FnName, bool WarnIfMissing) { 61 if (Fun == FunDef) { 62 if (WarnIfMissing) 63 Printf("WARNING: Failed to find function \"%s\".\n", FnName); 64 return nullptr; 65 } 66 return Fun; 67} 68 69namespace fuzzer { 70 71ExternalFunctions::ExternalFunctions() { 72#define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN) \ 73 this->NAME = GetFnPtr<decltype(::NAME)>(::NAME, ::NAME##Def, #NAME, WARN); 74 75#include "FuzzerExtFunctions.def" 76 77#undef EXT_FUNC 78} 79 80} // namespace fuzzer 81 82#endif // LIBFUZZER_WINDOWS 83