1 //===--- llvm-isel-fuzzer.cpp - Fuzzer for instruction selection ----------===//
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 // Tool to fuzz instruction selection using libFuzzer.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/ADT/StringRef.h"
14 #include "llvm/Analysis/TargetLibraryInfo.h"
15 #include "llvm/Bitcode/BitcodeReader.h"
16 #include "llvm/Bitcode/BitcodeWriter.h"
17 #include "llvm/CodeGen/CommandFlags.h"
18 #include "llvm/FuzzMutate/FuzzerCLI.h"
19 #include "llvm/FuzzMutate/IRMutator.h"
20 #include "llvm/FuzzMutate/Operations.h"
21 #include "llvm/IR/Constants.h"
22 #include "llvm/IR/LLVMContext.h"
23 #include "llvm/IR/LegacyPassManager.h"
24 #include "llvm/IR/Module.h"
25 #include "llvm/IR/Verifier.h"
26 #include "llvm/IRReader/IRReader.h"
27 #include "llvm/Support/CommandLine.h"
28 #include "llvm/Support/DataTypes.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Support/SourceMgr.h"
31 #include "llvm/Support/TargetRegistry.h"
32 #include "llvm/Support/TargetSelect.h"
33 #include "llvm/Target/TargetMachine.h"
34 
35 #define DEBUG_TYPE "isel-fuzzer"
36 
37 using namespace llvm;
38 
39 static codegen::RegisterCodeGenFlags CGF;
40 
41 static cl::opt<char>
42 OptLevel("O",
43          cl::desc("Optimization level. [-O0, -O1, -O2, or -O3] "
44                   "(default = '-O2')"),
45          cl::Prefix,
46          cl::ZeroOrMore,
47          cl::init(' '));
48 
49 static cl::opt<std::string>
50 TargetTriple("mtriple", cl::desc("Override target triple for module"));
51 
52 static std::unique_ptr<TargetMachine> TM;
53 static std::unique_ptr<IRMutator> Mutator;
54 
55 std::unique_ptr<IRMutator> createISelMutator() {
56   std::vector<TypeGetter> Types{
57       Type::getInt1Ty,  Type::getInt8Ty,  Type::getInt16Ty, Type::getInt32Ty,
58       Type::getInt64Ty, Type::getFloatTy, Type::getDoubleTy};
59 
60   std::vector<std::unique_ptr<IRMutationStrategy>> Strategies;
61   Strategies.emplace_back(
62       new InjectorIRStrategy(InjectorIRStrategy::getDefaultOps()));
63   Strategies.emplace_back(new InstDeleterIRStrategy());
64 
65   return std::make_unique<IRMutator>(std::move(Types), std::move(Strategies));
66 }
67 
68 extern "C" LLVM_ATTRIBUTE_USED size_t LLVMFuzzerCustomMutator(
69     uint8_t *Data, size_t Size, size_t MaxSize, unsigned int Seed) {
70   LLVMContext Context;
71   std::unique_ptr<Module> M;
72   if (Size <= 1)
73     // We get bogus data given an empty corpus - just create a new module.
74     M.reset(new Module("M", Context));
75   else
76     M = parseModule(Data, Size, Context);
77 
78   Mutator->mutateModule(*M, Seed, Size, MaxSize);
79 
80   return writeModule(*M, Data, MaxSize);
81 }
82 
83 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
84   if (Size <= 1)
85     // We get bogus data given an empty corpus - ignore it.
86     return 0;
87 
88   LLVMContext Context;
89   auto M = parseAndVerify(Data, Size, Context);
90   if (!M) {
91     errs() << "error: input module is broken!\n";
92     return 0;
93   }
94 
95   // Set up the module to build for our target.
96   M->setTargetTriple(TM->getTargetTriple().normalize());
97   M->setDataLayout(TM->createDataLayout());
98 
99   // Build up a PM to do instruction selection.
100   legacy::PassManager PM;
101   TargetLibraryInfoImpl TLII(TM->getTargetTriple());
102   PM.add(new TargetLibraryInfoWrapperPass(TLII));
103   raw_null_ostream OS;
104   TM->addPassesToEmitFile(PM, OS, nullptr, CGFT_Null);
105   PM.run(*M);
106 
107   return 0;
108 }
109 
110 static void handleLLVMFatalError(void *, const std::string &Message, bool) {
111   // TODO: Would it be better to call into the fuzzer internals directly?
112   dbgs() << "LLVM ERROR: " << Message << "\n"
113          << "Aborting to trigger fuzzer exit handling.\n";
114   abort();
115 }
116 
117 extern "C" LLVM_ATTRIBUTE_USED int LLVMFuzzerInitialize(int *argc,
118                                                         char ***argv) {
119   EnableDebugBuffering = true;
120 
121   InitializeAllTargets();
122   InitializeAllTargetMCs();
123   InitializeAllAsmPrinters();
124   InitializeAllAsmParsers();
125 
126   handleExecNameEncodedBEOpts(*argv[0]);
127   parseFuzzerCLOpts(*argc, *argv);
128 
129   if (TargetTriple.empty()) {
130     errs() << *argv[0] << ": -mtriple must be specified\n";
131     exit(1);
132   }
133 
134   Triple TheTriple = Triple(Triple::normalize(TargetTriple));
135 
136   // Get the target specific parser.
137   std::string Error;
138   const Target *TheTarget =
139       TargetRegistry::lookupTarget(codegen::getMArch(), TheTriple, Error);
140   if (!TheTarget) {
141     errs() << argv[0] << ": " << Error;
142     return 1;
143   }
144 
145   // Set up the pipeline like llc does.
146   std::string CPUStr = codegen::getCPUStr(),
147               FeaturesStr = codegen::getFeaturesStr();
148 
149   CodeGenOpt::Level OLvl = CodeGenOpt::Default;
150   switch (OptLevel) {
151   default:
152     errs() << argv[0] << ": invalid optimization level.\n";
153     return 1;
154   case ' ': break;
155   case '0': OLvl = CodeGenOpt::None; break;
156   case '1': OLvl = CodeGenOpt::Less; break;
157   case '2': OLvl = CodeGenOpt::Default; break;
158   case '3': OLvl = CodeGenOpt::Aggressive; break;
159   }
160 
161   TargetOptions Options = codegen::InitTargetOptionsFromCodeGenFlags();
162   TM.reset(TheTarget->createTargetMachine(
163       TheTriple.getTriple(), CPUStr, FeaturesStr, Options,
164       codegen::getExplicitRelocModel(), codegen::getExplicitCodeModel(), OLvl));
165   assert(TM && "Could not allocate target machine!");
166 
167   // Make sure we print the summary and the current unit when LLVM errors out.
168   install_fatal_error_handler(handleLLVMFatalError, nullptr);
169 
170   // Finally, create our mutator.
171   Mutator = createISelMutator();
172   return 0;
173 }
174