compiler-rt/lib/fuzzer/FuzzerExtFunctionsWindows.cpp

   1 //=== FuzzerExtWindows.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 of FuzzerExtFunctions for Windows. Uses alternatename when
   9 // compiled with MSVC. Uses weak aliases when compiled with clang. Unfortunately
  10 // the method each compiler supports is not supported by the other.
  11 //===----------------------------------------------------------------------===//
  12 #include "FuzzerPlatform.h"
  13 #if LIBFUZZER_WINDOWS
  14
  15 #include "FuzzerExtFunctions.h"
  16 #include "FuzzerIO.h"
  17
  18 using namespace fuzzer;
  19
  20 // Intermediate macro to ensure the parameter is expanded before stringified.
  21 #define STRINGIFY_(A) #A
  22 #define STRINGIFY(A) STRINGIFY_(A)
  23
  24 #if LIBFUZZER_MSVC
  25 // Copied from compiler-rt/lib/sanitizer_common/sanitizer_win_defs.h
  26 #if defined(_M_IX86) || defined(__i386__)
  27 #define WIN_SYM_PREFIX "_"
  28 #else
  29 #define WIN_SYM_PREFIX
  30 #endif
  31
  32 // Declare external functions as having alternativenames, so that we can
  33 // determine if they are not defined.
  34 #define EXTERNAL_FUNC(Name, Default)                                   \
  35   __pragma(comment(linker, "/alternatename:" WIN_SYM_PREFIX STRINGIFY( \
  36                                Name) "=" WIN_SYM_PREFIX STRINGIFY(Default)))
  37 #else
  38 // Declare external functions as weak to allow them to default to a specified
  39 // function if not defined explicitly. We must use weak symbols because clang's
  40 // support for alternatename is not 100%, see
  41 // https://bugs.llvm.org/show_bug.cgi?id=40218 for more details.
  42 #define EXTERNAL_FUNC(Name, Default) \
  43   __attribute__((weak, alias(STRINGIFY(Default))))
  44 #endif  // LIBFUZZER_MSVC
  45
  46 extern "C" {
  47 #define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN)         \
  48   RETURN_TYPE NAME##Def FUNC_SIG {                          \
  49     Printf("ERROR: Function \"%s\" not defined.\n", #NAME); \
  50     exit(1);                                                \
  51   }                                                         \
  52   EXTERNAL_FUNC(NAME, NAME##Def) RETURN_TYPE NAME FUNC_SIG
  53
  54 #include "FuzzerExtFunctions.def"
  55
  56 #undef EXT_FUNC
  57 }
  58
  59 template <typename T>
  60 static T *GetFnPtr(T *Fun, T *FunDef, const char *FnName, bool WarnIfMissing) {
  61   if (Fun == FunDef) {
  62     if (WarnIfMissing)
  63       Printf("WARNING: Failed to find function \"%s\".\n", FnName);
  64     return nullptr;
  65   }
  66   return Fun;
  67 }
  68
  69 namespace fuzzer {
  70
  71 ExternalFunctions::ExternalFunctions() {
  72 #define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN) \
  73   this->NAME = GetFnPtr<decltype(::NAME)>(::NAME, ::NAME##Def, #NAME, WARN);
  74
  75 #include "FuzzerExtFunctions.def"
  76
  77 #undef EXT_FUNC
  78 }
  79
  80 }  // namespace fuzzer
  81
  82 #endif // LIBFUZZER_WINDOWS