1//===-- lldb-expression-fuzzer.cpp ---------------------------------------===//
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//
9// \file
10// This file is a fuzzer for LLDB's expression evaluator. It uses protobufs
11// and the libprotobuf-mutator to create valid C-like inputs for the
12// expression evaluator.
13//
14//===---------------------------------------------------------------------===//
15
16#include <string>
17
18#include "cxx_proto.pb.h"
19#include "handle-cxx/handle_cxx.h"
20#include "lldb/API/SBBreakpoint.h"
21#include "lldb/API/SBDebugger.h"
22#include "lldb/API/SBError.h"
23#include "lldb/API/SBLaunchInfo.h"
24#include "lldb/API/SBProcess.h"
25#include "lldb/API/SBTarget.h"
26#include "proto-to-cxx/proto_to_cxx.h"
27#include "src/libfuzzer/libfuzzer_macro.h"
28#include "llvm/ADT/StringRef.h"
29#include "llvm/Support/Error.h"
30#include "llvm/Support/FileSystem.h"
31#include "llvm/Support/FormatVariadic.h"
32#include "llvm/Support/WithColor.h"
33
34using namespace lldb;
35using namespace llvm;
36using namespace clang_fuzzer;
37
38const char *target_path = nullptr;
39
40void ReportError(llvm::StringRef message) {
41  WithColor::error() << message << '\n';
42  exit(1);
43}
44
45extern "C" int LLVMFuzzerInitialize(int *argc, char ***argv) {
46#if !defined(_WIN32)
47  signal(SIGPIPE, SIG_IGN);
48#endif
49
50  // `target_path` can be set by either the "--lldb_fuzzer_target" commandline
51  // flag or the "LLDB_FUZZER_TARGET" environment variable. Arbitrarily, we
52  // always do flag parsing and only check the environment variable if the
53  // commandline flag is not set.
54  for (int i = 1; i < *argc; ++i) {
55    auto this_arg = llvm::StringRef((*argv)[i]);
56    WithColor::note() << "argv[" << i << "] = " << this_arg << "\n";
57    if (this_arg.consume_front("--lldb_fuzzer_target="))
58      target_path = this_arg.data();
59  }
60
61  if (!target_path)
62    target_path = ::getenv("LLDB_FUZZER_TARGET");
63
64  if (!target_path)
65    ReportError("No target path specified. Set one either as an environment "
66                "variable (i.e. LLDB_FUZZER_TARGET=target_path) or pass as a "
67                "command line flag (i.e. --lldb_fuzzer_target=target_path).");
68
69  if (!sys::fs::exists(target_path))
70    ReportError(formatv("target path '{0}' does not exist", target_path).str());
71
72  SBDebugger::Initialize();
73
74  return 0;
75}
76
77DEFINE_BINARY_PROTO_FUZZER(const clang_fuzzer::Function &input) {
78  std::string expression = clang_fuzzer::FunctionToString(input);
79
80  // Create a debugger and a target
81  SBDebugger debugger = SBDebugger::Create(false);
82  if (!debugger.IsValid())
83    ReportError("Couldn't create debugger");
84
85  SBTarget target = debugger.CreateTarget(target_path);
86  if (!target.IsValid())
87    ReportError(formatv("Couldn't create target '{0}'", target_path).str());
88
89  // Create a breakpoint on the only line in the program
90  SBBreakpoint breakpoint = target.BreakpointCreateByName("main", target_path);
91  if (!breakpoint.IsValid())
92    ReportError("Couldn't create breakpoint");
93
94  // Create launch info and error for launching the process
95  SBLaunchInfo launch_info = target.GetLaunchInfo();
96  SBError error;
97
98  // Launch the process and evaluate the fuzzer's input data
99  // as an expression
100  SBProcess process = target.Launch(launch_info, error);
101  if (!process.IsValid() || error.Fail())
102    ReportError("Couldn't launch process");
103
104  SBValue value = target.EvaluateExpression(expression.c_str());
105
106  debugger.DeleteTarget(target);
107  SBDebugger::Destroy(debugger);
108  SBModule::GarbageCollectAllocatedModules();
109}
110