1 //==-- handle_llvm.cpp - Helper function for Clang fuzzers -----------------==//
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 // Implements HandleLLVM for use by the Clang fuzzers. First runs a loop
10 // vectorizer optimization pass over the given IR code. Then mimics lli on both
11 // versions to JIT the generated code and execute it. Currently, functions are
12 // executed on dummy inputs.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #include "handle_llvm.h"
17 #include "input_arrays.h"
18 
19 #include "llvm/ADT/Triple.h"
20 #include "llvm/Analysis/TargetLibraryInfo.h"
21 #include "llvm/Analysis/TargetTransformInfo.h"
22 #include "llvm/CodeGen/CommandFlags.h"
23 #include "llvm/CodeGen/MachineModuleInfo.h"
24 #include "llvm/CodeGen/TargetPassConfig.h"
25 #include "llvm/ExecutionEngine/JITEventListener.h"
26 #include "llvm/ExecutionEngine/JITSymbol.h"
27 #include "llvm/ExecutionEngine/MCJIT.h"
28 #include "llvm/ExecutionEngine/ObjectCache.h"
29 #include "llvm/ExecutionEngine/RTDyldMemoryManager.h"
30 #include "llvm/ExecutionEngine/SectionMemoryManager.h"
31 #include "llvm/IR/IRPrintingPasses.h"
32 #include "llvm/IR/LLVMContext.h"
33 #include "llvm/IR/LegacyPassManager.h"
34 #include "llvm/IR/LegacyPassNameParser.h"
35 #include "llvm/IR/Module.h"
36 #include "llvm/IR/Verifier.h"
37 #include "llvm/IRReader/IRReader.h"
38 #include "llvm/Pass.h"
39 #include "llvm/PassRegistry.h"
40 #include "llvm/Support/MemoryBuffer.h"
41 #include "llvm/Support/SourceMgr.h"
42 #include "llvm/Support/TargetRegistry.h"
43 #include "llvm/Support/TargetSelect.h"
44 #include "llvm/Target/TargetMachine.h"
45 #include "llvm/Transforms/IPO.h"
46 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
47 #include "llvm/Transforms/Vectorize.h"
48 
49 using namespace llvm;
50 
51 static codegen::RegisterCodeGenFlags CGF;
52 
53 // Define a type for the functions that are compiled and executed
54 typedef void (*LLVMFunc)(int*, int*, int*, int);
55 
56 // Helper function to parse command line args and find the optimization level
57 static void getOptLevel(const std::vector<const char *> &ExtraArgs,
58                               CodeGenOpt::Level &OLvl) {
59   // Find the optimization level from the command line args
60   OLvl = CodeGenOpt::Default;
61   for (auto &A : ExtraArgs) {
62     if (A[0] == '-' && A[1] == 'O') {
63       switch(A[2]) {
64         case '0': OLvl = CodeGenOpt::None; break;
65         case '1': OLvl = CodeGenOpt::Less; break;
66         case '2': OLvl = CodeGenOpt::Default; break;
67         case '3': OLvl = CodeGenOpt::Aggressive; break;
68         default:
69           errs() << "error: opt level must be between 0 and 3.\n";
70           std::exit(1);
71       }
72     }
73   }
74 }
75 
76 static void ErrorAndExit(std::string message) {
77   errs()<< "ERROR: " << message << "\n";
78   std::exit(1);
79 }
80 
81 // Helper function to add optimization passes to the TargetMachine at the
82 // specified optimization level, OptLevel
83 static void AddOptimizationPasses(legacy::PassManagerBase &MPM,
84                                   CodeGenOpt::Level OptLevel,
85                                   unsigned SizeLevel) {
86   // Create and initialize a PassManagerBuilder
87   PassManagerBuilder Builder;
88   Builder.OptLevel = OptLevel;
89   Builder.SizeLevel = SizeLevel;
90   Builder.Inliner = createFunctionInliningPass(OptLevel, SizeLevel, false);
91   Builder.LoopVectorize = true;
92   Builder.populateModulePassManager(MPM);
93 }
94 
95 // Mimics the opt tool to run an optimization pass over the provided IR
96 static std::string OptLLVM(const std::string &IR, CodeGenOpt::Level OLvl) {
97   // Create a module that will run the optimization passes
98   SMDiagnostic Err;
99   LLVMContext Context;
100   std::unique_ptr<Module> M = parseIR(MemoryBufferRef(IR, "IR"), Err, Context);
101   if (!M || verifyModule(*M, &errs()))
102     ErrorAndExit("Could not parse IR");
103 
104   Triple ModuleTriple(M->getTargetTriple());
105   const TargetOptions Options =
106       codegen::InitTargetOptionsFromCodeGenFlags(ModuleTriple);
107   std::string E;
108   const Target *TheTarget =
109       TargetRegistry::lookupTarget(codegen::getMArch(), ModuleTriple, E);
110   if (!TheTarget)
111     ErrorAndExit(E);
112 
113   std::unique_ptr<TargetMachine> TM(TheTarget->createTargetMachine(
114       M->getTargetTriple(), codegen::getCPUStr(), codegen::getFeaturesStr(),
115       Options, codegen::getExplicitRelocModel(),
116       codegen::getExplicitCodeModel(), OLvl));
117   if (!TM)
118     ErrorAndExit("Could not create target machine");
119 
120   codegen::setFunctionAttributes(codegen::getCPUStr(),
121                                  codegen::getFeaturesStr(), *M);
122 
123   legacy::PassManager Passes;
124 
125   Passes.add(new TargetLibraryInfoWrapperPass(ModuleTriple));
126   Passes.add(createTargetTransformInfoWrapperPass(TM->getTargetIRAnalysis()));
127 
128   LLVMTargetMachine &LTM = static_cast<LLVMTargetMachine &>(*TM);
129   Passes.add(LTM.createPassConfig(Passes));
130 
131   Passes.add(createVerifierPass());
132 
133   AddOptimizationPasses(Passes, OLvl, 0);
134 
135   // Add a pass that writes the optimized IR to an output stream
136   std::string outString;
137   raw_string_ostream OS(outString);
138   Passes.add(createPrintModulePass(OS, "", false));
139 
140   Passes.run(*M);
141 
142   return OS.str();
143 }
144 
145 // Takes a function and runs it on a set of inputs
146 // First determines whether f is the optimized or unoptimized function
147 static void RunFuncOnInputs(LLVMFunc f, int Arr[kNumArrays][kArraySize]) {
148   for (int i = 0; i < kNumArrays / 3; i++)
149     f(Arr[i], Arr[i + (kNumArrays / 3)], Arr[i + (2 * kNumArrays / 3)],
150       kArraySize);
151 }
152 
153 // Takes a string of IR and compiles it using LLVM's JIT Engine
154 static void CreateAndRunJITFunc(const std::string &IR, CodeGenOpt::Level OLvl) {
155   SMDiagnostic Err;
156   LLVMContext Context;
157   std::unique_ptr<Module> M = parseIR(MemoryBufferRef(IR, "IR"), Err, Context);
158   if (!M)
159     ErrorAndExit("Could not parse IR");
160 
161   Function *EntryFunc = M->getFunction("foo");
162   if (!EntryFunc)
163     ErrorAndExit("Function not found in module");
164 
165   std::string ErrorMsg;
166   Triple ModuleTriple(M->getTargetTriple());
167 
168   EngineBuilder builder(std::move(M));
169   builder.setMArch(codegen::getMArch());
170   builder.setMCPU(codegen::getCPUStr());
171   builder.setMAttrs(codegen::getFeatureList());
172   builder.setErrorStr(&ErrorMsg);
173   builder.setEngineKind(EngineKind::JIT);
174   builder.setMCJITMemoryManager(std::make_unique<SectionMemoryManager>());
175   builder.setOptLevel(OLvl);
176   builder.setTargetOptions(
177       codegen::InitTargetOptionsFromCodeGenFlags(ModuleTriple));
178 
179   std::unique_ptr<ExecutionEngine> EE(builder.create());
180   if (!EE)
181     ErrorAndExit("Could not create execution engine");
182 
183   EE->finalizeObject();
184   EE->runStaticConstructorsDestructors(false);
185 
186 #if defined(__GNUC__) && !defined(__clang) &&                                  \
187     ((__GNUC__ == 4) && (__GNUC_MINOR__ < 9))
188 // Silence
189 //
190 //   warning: ISO C++ forbids casting between pointer-to-function and
191 //   pointer-to-object [-Wpedantic]
192 //
193 // Since C++11 this casting is conditionally supported and GCC versions
194 // starting from 4.9.0 don't warn about the cast.
195 #pragma GCC diagnostic push
196 #pragma GCC diagnostic ignored "-Wpedantic"
197 #endif
198   LLVMFunc f = reinterpret_cast<LLVMFunc>(EE->getPointerToFunction(EntryFunc));
199 #if defined(__GNUC__) && !defined(__clang) &&                                  \
200     ((__GNUC__ == 4) && (__GNUC_MINOR__ < 9))
201 #pragma GCC diagnostic pop
202 #endif
203 
204   // Figure out if we are running the optimized func or the unoptimized func
205   RunFuncOnInputs(f, (OLvl == CodeGenOpt::None) ? UnoptArrays : OptArrays);
206 
207   EE->runStaticConstructorsDestructors(true);
208 }
209 
210 // Main fuzz target called by ExampleClangLLVMProtoFuzzer.cpp
211 // Mimics the lli tool to JIT the LLVM IR code and execute it
212 void clang_fuzzer::HandleLLVM(const std::string &IR,
213                               const std::vector<const char *> &ExtraArgs) {
214   // Populate OptArrays and UnoptArrays with the arrays from InputArrays
215   memcpy(OptArrays, InputArrays, kTotalSize);
216   memcpy(UnoptArrays, InputArrays, kTotalSize);
217 
218   // Parse ExtraArgs to set the optimization level
219   CodeGenOpt::Level OLvl;
220   getOptLevel(ExtraArgs, OLvl);
221 
222   // First we optimize the IR by running a loop vectorizer pass
223   std::string OptIR = OptLLVM(IR, OLvl);
224 
225   CreateAndRunJITFunc(OptIR, OLvl);
226   CreateAndRunJITFunc(IR, CodeGenOpt::None);
227 
228   if (memcmp(OptArrays, UnoptArrays, kTotalSize))
229     ErrorAndExit("!!!BUG!!!");
230 
231   return;
232 }
233