src/libcompiler_builtins/compiler-rt/lib/fuzzer/FuzzerExtFunctionsDlsym.cpp

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