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
CheckFnPtr(void * FnPtr,const char * FnName,bool WarnIfMissing)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
ExternalFunctions()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
55