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 18 using 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 46 extern "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 59 template <typename T> 60 static 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 69 namespace fuzzer { 70 71 ExternalFunctions::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