FuzzerExtFunctionsDlsym.cpp

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//===- FuzzerExtFunctionsDlsym.cpp - Interface to external functions ------===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

// Implementation for operating systems that support dlsym(). We only use it on

// Apple platforms for now. We don't use this approach on Linux because it

// requires that clients of LibFuzzer pass ``--export-dynamic`` to the linker.

// That is a complication we don't wish to expose to clients right now.

//===----------------------------------------------------------------------===//

#include "FuzzerPlatform.h"

#if LIBFUZZER_APPLE

#include "FuzzerExtFunctions.h"

#include "FuzzerIO.h"

#include <dlfcn.h>

using namespace fuzzer;

template <typename T>

static T GetFnPtr(const char *FnName, bool WarnIfMissing) {

  dlerror(); // Clear any previous errors.

  void *Fn = dlsym(RTLD_DEFAULT, FnName);

  if (Fn == nullptr) {

    if (WarnIfMissing) {

      const char *ErrorMsg = dlerror();

      Printf("WARNING: Failed to find function \"%s\".", FnName);

      if (ErrorMsg)

        Printf(" Reason %s.", ErrorMsg);

      Printf("\n");

  return reinterpret_cast<T>(Fn);

namespace fuzzer {

ExternalFunctions::ExternalFunctions() {

#define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN)                            \

  this->NAME = GetFnPtr<decltype(ExternalFunctions::NAME)>(#NAME, WARN)

#include "FuzzerExtFunctions.def"

#undef EXT_FUNC

} // namespace fuzzer

#endif // LIBFUZZER_APPLE