1 //===- FuzzerExtFunctionsWeak.cpp - Interface to external functions -------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // Implementation for Linux. This relies on the linker's support for weak 10 // symbols. We don't use this approach on Apple platforms because it requires 11 // clients of LibFuzzer to pass ``-U _<symbol_name>`` to the linker to allow 12 // weak symbols to be undefined. That is a complication we don't want to expose 13 // to clients right now. 14 //===----------------------------------------------------------------------===// 15 #include "FuzzerDefs.h" 16 #if LIBFUZZER_LINUX 17 18 #include "FuzzerExtFunctions.h" 19 #include "FuzzerIO.h" 20 21 extern "C" { 22 // Declare these symbols as weak to allow them to be optionally defined. 23 #define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN) \ 24 __attribute__((weak)) RETURN_TYPE NAME FUNC_SIG 25 26 #include "FuzzerExtFunctions.def" 27 28 #undef EXT_FUNC 29 } 30 31 using namespace fuzzer; 32 33 static void CheckFnPtr(void *FnPtr, const char *FnName, bool WarnIfMissing) { 34 if (FnPtr == nullptr && WarnIfMissing) { 35 Printf("WARNING: Failed to find function \"%s\".\n", FnName); 36 } 37 } 38 39 namespace fuzzer { 40 41 ExternalFunctions::ExternalFunctions() { 42 #define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN) \ 43 this->NAME = ::NAME; \ 44 CheckFnPtr(reinterpret_cast<void *>(reinterpret_cast<uintptr_t>(::NAME)), \ 45 #NAME, WARN); 46 47 #include "FuzzerExtFunctions.def" 48 49 #undef EXT_FUNC 50 } 51 52 } // namespace fuzzer 53 54 #endif // LIBFUZZER_LINUX 55