compiler-rt/lib/fuzzer/FuzzerExtFunctionsWeak.cpp

   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