compiler-rt/lib/fuzzer/FuzzerExtFunctionsDlsym.cpp

   1 //===- FuzzerExtFunctionsDlsym.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 operating systems that support dlsym(). We only use it on
   9 // Apple platforms for now. We don't use this approach on Linux because it
  10 // requires that clients of LibFuzzer pass ``--export-dynamic`` to the linker.
  11 // That is a complication we don't wish to expose to clients right now.
  12 //===----------------------------------------------------------------------===//
  13 #include "FuzzerPlatform.h"
  14 #if LIBFUZZER_APPLE
  15
  16 #include "FuzzerExtFunctions.h"
  17 #include "FuzzerIO.h"
  18 #include <dlfcn.h>
  19
  20 using namespace fuzzer;
  21
  22 template <typename T>
  23 static T GetFnPtr(const char *FnName, bool WarnIfMissing) {
  24   dlerror(); // Clear any previous errors.
  25   void *Fn = dlsym(RTLD_DEFAULT, FnName);
  26   if (Fn == nullptr) {
  27     if (WarnIfMissing) {
  28       const char *ErrorMsg = dlerror();
  29       Printf("WARNING: Failed to find function \"%s\".", FnName);
  30       if (ErrorMsg)
  31         Printf(" Reason %s.", ErrorMsg);
  32       Printf("\n");
  33     }
  34   }
  35   return reinterpret_cast<T>(Fn);
  36 }
  37
  38 namespace fuzzer {
  39
  40 ExternalFunctions::ExternalFunctions() {
  41 #define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN)                            \
  42   this->NAME = GetFnPtr<decltype(ExternalFunctions::NAME)>(#NAME, WARN)
  43
  44 #include "FuzzerExtFunctions.def"
  45
  46 #undef EXT_FUNC
  47 }
  48
  49 } // namespace fuzzer
  50
  51 #endif // LIBFUZZER_APPLE