1 //===- FuzzerExtFunctionsWeak.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 for Linux. This relies on the linker's support for weak 9 // symbols. We don't use this approach on Apple platforms because it requires 10 // clients of LibFuzzer to pass ``-U _<symbol_name>`` to the linker to allow 11 // weak symbols to be undefined. That is a complication we don't want to expose 12 // to clients right now. 13 //===----------------------------------------------------------------------===// 14 #include "FuzzerPlatform.h" 15 #if LIBFUZZER_LINUX || LIBFUZZER_NETBSD || LIBFUZZER_FUCHSIA || \ 16 LIBFUZZER_FREEBSD || LIBFUZZER_EMSCRIPTEN 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, visibility("default"))) 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 55