1 //===- InstrOrderFile.cpp ---- Late IR instrumentation for order file ----===//
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 //===----------------------------------------------------------------------===//
10 
11 #include "llvm/Transforms/Instrumentation/InstrOrderFile.h"
12 #include "llvm/IR/Constants.h"
13 #include "llvm/IR/Function.h"
14 #include "llvm/IR/GlobalValue.h"
15 #include "llvm/IR/IRBuilder.h"
16 #include "llvm/IR/Instructions.h"
17 #include "llvm/IR/Module.h"
18 #include "llvm/ProfileData/InstrProf.h"
19 #include "llvm/Support/CommandLine.h"
20 #include "llvm/Support/FileSystem.h"
21 #include "llvm/Support/raw_ostream.h"
22 #include "llvm/Transforms/Instrumentation.h"
23 #include <fstream>
24 #include <mutex>
25 #include <sstream>
26 
27 using namespace llvm;
28 #define DEBUG_TYPE "instrorderfile"
29 
30 static cl::opt<std::string> ClOrderFileWriteMapping(
31     "orderfile-write-mapping", cl::init(""),
32     cl::desc(
33         "Dump functions and their MD5 hash to deobfuscate profile data"),
34     cl::Hidden);
35 
36 namespace {
37 
38 // We need a global bitmap to tell if a function is executed. We also
39 // need a global variable to save the order of functions. We can use a
40 // fixed-size buffer that saves the MD5 hash of the function. We need
41 // a global variable to save the index into the buffer.
42 
43 std::mutex MappingMutex;
44 
45 struct InstrOrderFile {
46 private:
47   GlobalVariable *OrderFileBuffer;
48   GlobalVariable *BufferIdx;
49   GlobalVariable *BitMap;
50   ArrayType *BufferTy;
51   ArrayType *MapTy;
52 
53 public:
54   InstrOrderFile() = default;
55 
56   void createOrderFileData(Module &M) {
57     LLVMContext &Ctx = M.getContext();
58     int NumFunctions = 0;
59     for (Function &F : M) {
60       if (!F.isDeclaration())
61         NumFunctions++;
62     }
63 
64     BufferTy =
65         ArrayType::get(Type::getInt64Ty(Ctx), INSTR_ORDER_FILE_BUFFER_SIZE);
66     Type *IdxTy = Type::getInt32Ty(Ctx);
67     MapTy = ArrayType::get(Type::getInt8Ty(Ctx), NumFunctions);
68 
69     // Create the global variables.
70     std::string SymbolName = INSTR_PROF_ORDERFILE_BUFFER_NAME_STR;
71     OrderFileBuffer = new GlobalVariable(M, BufferTy, false, GlobalValue::LinkOnceODRLinkage,
72                            Constant::getNullValue(BufferTy), SymbolName);
73     Triple TT = Triple(M.getTargetTriple());
74     OrderFileBuffer->setSection(
75         getInstrProfSectionName(IPSK_orderfile, TT.getObjectFormat()));
76 
77     std::string IndexName = INSTR_PROF_ORDERFILE_BUFFER_IDX_NAME_STR;
78     BufferIdx = new GlobalVariable(M, IdxTy, false, GlobalValue::LinkOnceODRLinkage,
79                            Constant::getNullValue(IdxTy), IndexName);
80 
81     std::string BitMapName = "bitmap_0";
82     BitMap = new GlobalVariable(M, MapTy, false, GlobalValue::PrivateLinkage,
83                                 Constant::getNullValue(MapTy), BitMapName);
84   }
85 
86   // Generate the code sequence in the entry block of each function to
87   // update the buffer.
88   void generateCodeSequence(Module &M, Function &F, int FuncId) {
89     if (!ClOrderFileWriteMapping.empty()) {
90       std::lock_guard<std::mutex> LogLock(MappingMutex);
91       std::error_code EC;
92       llvm::raw_fd_ostream OS(ClOrderFileWriteMapping, EC,
93                               llvm::sys::fs::OF_Append);
94       if (EC) {
95         report_fatal_error(Twine("Failed to open ") + ClOrderFileWriteMapping +
96                            " to save mapping file for order file instrumentation\n");
97       } else {
98         std::stringstream stream;
99         stream << std::hex << MD5Hash(F.getName());
100         std::string singleLine = "MD5 " + stream.str() + " " +
101                                  std::string(F.getName()) + '\n';
102         OS << singleLine;
103       }
104     }
105 
106     BasicBlock *OrigEntry = &F.getEntryBlock();
107 
108     LLVMContext &Ctx = M.getContext();
109     IntegerType *Int32Ty = Type::getInt32Ty(Ctx);
110     IntegerType *Int8Ty = Type::getInt8Ty(Ctx);
111 
112     // Create a new entry block for instrumentation. We will check the bitmap
113     // in this basic block.
114     BasicBlock *NewEntry =
115         BasicBlock::Create(M.getContext(), "order_file_entry", &F, OrigEntry);
116     IRBuilder<> entryB(NewEntry);
117     // Create a basic block for updating the circular buffer.
118     BasicBlock *UpdateOrderFileBB =
119         BasicBlock::Create(M.getContext(), "order_file_set", &F, OrigEntry);
120     IRBuilder<> updateB(UpdateOrderFileBB);
121 
122     // Check the bitmap, if it is already 1, do nothing.
123     // Otherwise, set the bit, grab the index, update the buffer.
124     Value *IdxFlags[] = {ConstantInt::get(Int32Ty, 0),
125                          ConstantInt::get(Int32Ty, FuncId)};
126     Value *MapAddr = entryB.CreateGEP(MapTy, BitMap, IdxFlags, "");
127     LoadInst *loadBitMap = entryB.CreateLoad(Int8Ty, MapAddr, "");
128     entryB.CreateStore(ConstantInt::get(Int8Ty, 1), MapAddr);
129     Value *IsNotExecuted =
130         entryB.CreateICmpEQ(loadBitMap, ConstantInt::get(Int8Ty, 0));
131     entryB.CreateCondBr(IsNotExecuted, UpdateOrderFileBB, OrigEntry);
132 
133     // Fill up UpdateOrderFileBB: grab the index, update the buffer!
134     Value *IdxVal = updateB.CreateAtomicRMW(
135         AtomicRMWInst::Add, BufferIdx, ConstantInt::get(Int32Ty, 1),
136         MaybeAlign(), AtomicOrdering::SequentiallyConsistent);
137     // We need to wrap around the index to fit it inside the buffer.
138     Value *WrappedIdx = updateB.CreateAnd(
139         IdxVal, ConstantInt::get(Int32Ty, INSTR_ORDER_FILE_BUFFER_MASK));
140     Value *BufferGEPIdx[] = {ConstantInt::get(Int32Ty, 0), WrappedIdx};
141     Value *BufferAddr =
142         updateB.CreateGEP(BufferTy, OrderFileBuffer, BufferGEPIdx, "");
143     updateB.CreateStore(ConstantInt::get(Type::getInt64Ty(Ctx), MD5Hash(F.getName())),
144                         BufferAddr);
145     updateB.CreateBr(OrigEntry);
146   }
147 
148   bool run(Module &M) {
149     createOrderFileData(M);
150 
151     int FuncId = 0;
152     for (Function &F : M) {
153       if (F.isDeclaration())
154         continue;
155       generateCodeSequence(M, F, FuncId);
156       ++FuncId;
157     }
158 
159     return true;
160   }
161 
162 }; // End of InstrOrderFile struct
163 } // End anonymous namespace
164 
165 PreservedAnalyses
166 InstrOrderFilePass::run(Module &M, ModuleAnalysisManager &AM) {
167   if (InstrOrderFile().run(M))
168     return PreservedAnalyses::none();
169   return PreservedAnalyses::all();
170 }
171