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revng-revng/codegenerator.cpp
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Alessandro Di Federico c50dcc5c5d Use symbols to produce meaningful names 
This commit introduces the usage of symbols, if they are available. We
employ them to produce meaningful names for basic block names.

* Collect the symbols from `.symtab`/`.dynsym`
* Box the `Segments` into a new data structure (`BinaryInfo`) which also
  handles symbols.
* `JumpTargetManager::nameForAddress`: produce a meaningful name using
  symbols, if possible.
* Spread some `const`-ness
2016-09-28 00:03:13 +02:00

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/// \file codegenerator.cpp
/// \brief This file handles the whole translation process from the input
/// assembly to LLVM IR.
//
// This file is distributed under the MIT License. See LICENSE.md for details.
//
// Standard includes
#include <cstring>
#include <memory>
#include <sstream>
#include <vector>
#include <fstream>
#include <queue>
#include <set>
#include <utility>
// LLVM includes
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/ExecutionEngine/RuntimeDyld.h"
#include "llvm/IR/AssemblyAnnotationWriter.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/DiagnosticPrinter.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Module.h"
#include "llvm/IRReader/IRReader.h"
#include "llvm/Linker/Linker.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/raw_os_ostream.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
// Boost includes
#include <boost/icl/interval_map.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/icl/right_open_interval.hpp>
// Local includes
#include "codegenerator.h"
#include "debug.h"
#include "debughelper.h"
#include "functionboundariesdetection.h"
#include "instructiontranslator.h"
#include "jumptargetmanager.h"
#include "ptcinterface.h"
#include "revamb.h"
#include "variablemanager.h"
using namespace llvm;
using std::make_pair;
template<typename T, typename... Args>
inline std::array<T, sizeof...(Args)>
make_array(Args&&... args) {
return { { std::forward<Args>(args)... } };
}
// Outline the destructor for the sake of privacy in the header
CodeGenerator::~CodeGenerator() = default;
CodeGenerator::CodeGenerator(std::string Input,
Architecture& Target,
std::string Output,
std::string Helpers,
DebugInfoType DebugInfo,
std::string Debug,
std::string LinkingInfo,
std::string Coverage,
std::string BBSummary,
bool EnableOSRA,
bool EnableTracing,
bool UseSections) :
TargetArchitecture(Target),
Context(getGlobalContext()),
TheModule((new Module("top", Context))),
OutputPath(Output),
Debug(new DebugHelper(Output, Debug, TheModule.get(), DebugInfo)),
EnableOSRA(EnableOSRA),
EnableTracing(EnableTracing)
{
OriginalInstrMDKind = Context.getMDKindID("oi");
PTCInstrMDKind = Context.getMDKindID("pi");
DbgMDKind = Context.getMDKindID("dbg");
SMDiagnostic Errors;
HelpersModule = parseIRFile(Helpers, Errors, Context);
if (HelpersModule.get() == nullptr) {
Errors.print("revamb", dbgs());
abort();
}
if (Coverage.size() == 0)
Coverage = Output + ".coverage.csv";
this->CoveragePath = Coverage;
if (BBSummary.size() == 0)
BBSummary = Output + ".bbsummary.csv";
this->BBSummaryPath = BBSummary;
auto BinaryOrErr = object::createBinary(Input);
assert(BinaryOrErr && "Couldn't open the input file");
BinaryHandle = std::move(BinaryOrErr.get());
// We only support ELF for now
auto *TheBinary = cast<object::ObjectFile>(BinaryHandle.getBinary());
// TODO: QEMU should provide this information
unsigned InstructionAlignment = 0;
StringRef SyscallHelper = "";
StringRef SyscallNumberRegister = "";
ArrayRef<uint64_t> NoReturnSyscalls = { };
switch (TheBinary->getArch()) {
case Triple::x86_64:
InstructionAlignment = 1;
SyscallHelper = "helper_syscall";
SyscallNumberRegister = "rax";
NoReturnSyscalls = {
0xe7, // exit_group
0x3c, // exit
0x3b // execve
};
break;
case Triple::arm:
InstructionAlignment = 4;
SyscallHelper = "helper_exception_with_syndrome";
SyscallNumberRegister = "r7";
NoReturnSyscalls = {
0xf8, // exit_group
0x1, // exit
0xb // execve
};
break;
case Triple::mips:
InstructionAlignment = 4;
SyscallHelper = "helper_raise_exception";
SyscallNumberRegister = "v0";
NoReturnSyscalls = {
0x1096, // exit_group
0xfa1, // exit
0xfab // execve
};
break;
default:
assert(false);
}
SourceArchitecture = Architecture(InstructionAlignment,
1,
TheBinary->isLittleEndian(),
TheBinary->getBytesInAddress() * 8,
SyscallHelper,
SyscallNumberRegister,
NoReturnSyscalls);
if (SourceArchitecture.pointerSize() == 32) {
if (SourceArchitecture.isLittleEndian()) {
parseELF<object::ELF32LE>(TheBinary, LinkingInfo, UseSections);
} else {
parseELF<object::ELF32BE>(TheBinary, LinkingInfo, UseSections);
}
} else if (SourceArchitecture.pointerSize() == 64) {
if (SourceArchitecture.isLittleEndian()) {
parseELF<object::ELF64LE>(TheBinary, LinkingInfo, UseSections);
} else {
parseELF<object::ELF64BE>(TheBinary, LinkingInfo, UseSections);
}
} else {
assert("Unexpect address size");
}
}
std::string SegmentInfo::generateName() {
// Create name from start and size
std::stringstream NameStream;
NameStream << ".o_"
<< (IsReadable ? "r" : "")
<< (IsWriteable ? "w" : "")
<< (IsExecutable ? "x" : "")
<< "_0x" << std::hex << StartVirtualAddress;
return NameStream.str();
}
template<typename T>
void CodeGenerator::parseELF(object::ObjectFile *TheBinary,
std::string LinkingInfo,
bool UseSections) {
// Parse the ELF file
std::error_code EC;
object::ELFFile<T> TheELF(TheBinary->getData(), EC);
assert(!EC && "Error while loading the ELF file");
// Look for static or dynamic symbols
using Elf_ShdrPtr = decltype(&(*TheELF.sections().begin()));
Elf_ShdrPtr Symtab = nullptr;
for (auto &Section : TheELF.sections()){
auto Name = TheELF.getSectionName(&Section);
if (Name && Name.get() == ".symtab") {
Symtab = &Section;
break;
} else if (Name && Name.get() == ".dynsym") {
Symtab = &Section;
}
}
// If we found a symbol table
if (Symtab != nullptr && Symtab->sh_link != 0) {
// Obtain a reference to the string table
auto *Strtab = TheELF.getSection(Symtab->sh_link).get();
auto StrtabArray = TheELF.getSectionContents(Strtab).get();
StringRef StrtabContent(reinterpret_cast<const char *>(StrtabArray.data()),
StrtabArray.size());
// Collect symbol names
for (auto &Symbol : TheELF.symbols(Symtab)) {
Binary.Symbols.push_back({
Symbol.getName(StrtabContent).get(),
Symbol.st_value,
Symbol.st_size
});
}
}
const auto *ElfHeader = TheELF.getHeader();
EntryPoint = static_cast<uint64_t>(ElfHeader->e_entry);
// Prepare the linking info CSV
if (LinkingInfo.size() == 0)
LinkingInfo = OutputPath + ".li.csv";
std::ofstream LinkingInfoStream(LinkingInfo);
LinkingInfoStream << "name,start,end" << std::endl;
auto *Uint8Ty = Type::getInt8Ty(Context);
auto *ElfHeaderHelper = new GlobalVariable(*TheModule,
Uint8Ty,
true,
GlobalValue::ExternalLinkage,
ConstantInt::get(Uint8Ty, 0),
".elfheaderhelper");
ElfHeaderHelper->setAlignment(1);
ElfHeaderHelper->setSection(".elfheaderhelper");
auto *RegisterType = Type::getIntNTy(Context, T::Is64Bits ? 64 : 32);
auto createConstGlobal = [this, &RegisterType] (const Twine &Name,
uint64_t Value) {
return new GlobalVariable(*TheModule,
RegisterType,
true,
GlobalValue::ExternalLinkage,
ConstantInt::get(RegisterType, Value),
Name);
};
// These values will be used to populate the auxiliary vectors
createConstGlobal("e_phentsize", ElfHeader->e_phentsize);
createConstGlobal("e_phnum", ElfHeader->e_phnum);
// Loop over the program headers looking for PT_LOAD segments, read them out
// and create a global variable for each one of them (writable or read-only),
// assign them a section and output information about them in the linking info
// CSV
using Elf_Phdr = const typename object::ELFFile<T>::Elf_Phdr;
for (Elf_Phdr &ProgramHeader : TheELF.program_headers())
if (ProgramHeader.p_type == ELF::PT_LOAD) {
SegmentInfo Segment;
Segment.StartVirtualAddress = ProgramHeader.p_vaddr;
Segment.EndVirtualAddress = ProgramHeader.p_vaddr + ProgramHeader.p_memsz;
Segment.IsReadable = ProgramHeader.p_flags & ELF::PF_R;
Segment.IsWriteable = ProgramHeader.p_flags & ELF::PF_W;
Segment.IsExecutable = ProgramHeader.p_flags & ELF::PF_X;
// If it's an executable segment, and we've been asked so, register which
// sections actually contain code
if (UseSections && Segment.IsExecutable) {
using Elf_Shdr = const typename object::ELFFile<T>::Elf_Shdr;
auto Inserter = std::back_inserter(Segment.ExecutableSections);
for (Elf_Shdr &SectionHeader : TheELF.sections())
if (SectionHeader.sh_flags & ELF::SHF_EXECINSTR)
Inserter = make_pair(SectionHeader.sh_addr,
SectionHeader.sh_addr + SectionHeader.sh_size);
}
auto ActualStartAddress = TheELF.base() + ProgramHeader.p_offset;
// If it's executable register it as a valid code area
if (Segment.IsExecutable) {
// We ignore possible p_filesz-p_memsz mismatches, zeros wouldn't be
// useful code anyway
ptc.mmap(static_cast<uint64_t>(ProgramHeader.p_vaddr),
static_cast<const void *>(ActualStartAddress),
static_cast<size_t>(ProgramHeader.p_filesz));
}
std::string Name = Segment.generateName();
// Get data and size
auto *DataType = ArrayType::get(Uint8Ty, ProgramHeader.p_memsz);
Constant *TheData = nullptr;
if (ProgramHeader.p_memsz == ProgramHeader.p_filesz) {
// Create the array directly from the mmap'd ELF
auto FileData = ArrayRef<uint8_t>(ActualStartAddress,
ProgramHeader.p_filesz);
TheData = ConstantDataArray::get(Context, FileData);
} else {
// If we have extra data at the end we need to create a copy of the
// segment and append the NULL bytes
auto FullData = make_unique<uint8_t[]>(ProgramHeader.p_memsz);
::memcpy(FullData.get(),
ActualStartAddress,
ProgramHeader.p_filesz);
::bzero(FullData.get() + ProgramHeader.p_filesz,
ProgramHeader.p_memsz - ProgramHeader.p_filesz);
auto DataRef = ArrayRef<uint8_t>(FullData.get(), ProgramHeader.p_memsz);
TheData = ConstantDataArray::get(Context, DataRef);
}
// Create a new global variable
Segment.Variable = new GlobalVariable(*TheModule,
DataType,
!Segment.IsWriteable,
GlobalValue::ExternalLinkage,
TheData,
Name);
// Force alignment to 1 and assign the variable to a specific section
Segment.Variable->setAlignment(1);
Segment.Variable->setSection(Name);
// Check if it's the segment containing the program headers
auto ProgramHeaderStart = ProgramHeader.p_offset;
auto ProgramHeaderEnd = ProgramHeader.p_offset + ProgramHeader.p_filesz;
if (ProgramHeaderStart <= ElfHeader->e_phoff
&& ElfHeader->e_phoff < ProgramHeaderEnd) {
auto PhdrAddress = static_cast<uint64_t>(ProgramHeader.p_vaddr
+ ElfHeader->e_phoff
- ProgramHeader.p_offset);
createConstGlobal("phdr_address", PhdrAddress);
}
// Write the linking info CSV
LinkingInfoStream << Name
<< ",0x" << std::hex << Segment.StartVirtualAddress
<< ",0x" << std::hex << Segment.EndVirtualAddress
<< std::endl;
Binary.Segments.push_back(Segment);
}
}
static BasicBlock *replaceFunction(Function *ToReplace) {
ToReplace->setLinkage(GlobalValue::InternalLinkage);
ToReplace->dropAllReferences();
return BasicBlock::Create(ToReplace->getParent()->getContext(),
"",
ToReplace);
}
static void replaceFunctionWithRet(Function *ToReplace, uint64_t Result) {
if (ToReplace == nullptr)
return;
BasicBlock *Body = replaceFunction(ToReplace);
Value *ResultValue;
if (ToReplace->getReturnType()->isVoidTy()) {
assert(Result == 0);
ResultValue = nullptr;
} else if (ToReplace->getReturnType()->isIntegerTy()) {
auto *ReturnType = cast<IntegerType>(ToReplace->getReturnType());
ResultValue = ConstantInt::get(ReturnType, Result, false);
} else {
llvm_unreachable("No-op functions can only return void or an integer type");
}
ReturnInst::Create(ToReplace->getParent()->getContext(), ResultValue, Body);
}
class CpuLoopFunctionPass : public llvm::FunctionPass {
public:
static char ID;
CpuLoopFunctionPass() : llvm::FunctionPass(ID) { }
void getAnalysisUsage(llvm::AnalysisUsage &AU) const override;
bool runOnFunction(llvm::Function &F) override;
};
char CpuLoopFunctionPass::ID = 0;
static RegisterPass<CpuLoopFunctionPass> X("cpu-loop",
"cpu_loop FunctionPass",
false,
false);
void CpuLoopFunctionPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<LoopInfoWrapperPass>();
}
template<class Range, class UnaryPredicate>
auto find_unique(Range&& TheRange, UnaryPredicate Predicate)
-> decltype(*TheRange.begin()) {
const auto Begin = TheRange.begin();
const auto End = TheRange.end();
auto It = std::find_if(Begin, End, Predicate);
auto Result = It;
assert(Result != End);
assert(std::find_if(++It, End, Predicate) == End);
return *Result;
}
template<class Range>
auto find_unique(Range&& TheRange)
-> decltype(*TheRange.begin()) {
const auto Begin = TheRange.begin();
const auto End = TheRange.end();
auto Result = Begin;
assert(Begin != End && ++Result == End);
(void) Result;
(void) End;
return *Begin;
}
bool CpuLoopFunctionPass::runOnFunction(Function &F) {
// cpu_loop must return void
assert(F.getReturnType()->isVoidTy());
Module *TheModule = F.getParent();
// Part 1: remove the backedge of the main infinite loop
const LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
const Loop *OutermostLoop = find_unique(LI);
BasicBlock *Header = OutermostLoop->getHeader();
// Check that the header has only one predecessor inside the loop
auto IsInLoop = [&OutermostLoop] (BasicBlock *Predecessor) {
return OutermostLoop->contains(Predecessor);
};
BasicBlock *Footer = find_unique(predecessors(Header), IsInLoop);
// Assert on the type of the last instruction (branch or brcond)
assert(Footer->end() != Footer->begin());
Instruction *LastInstruction = &*--Footer->end();
assert(isa<BranchInst>(LastInstruction));
// Remove the last instruction and replace it with a ret
LastInstruction->eraseFromParent();
ReturnInst::Create(F.getParent()->getContext(), Footer);
// Part 2: replace the call to cpu_*_exec with exception_index
auto IsCpuExec = [] (Function& TheFunction) {
StringRef Name = TheFunction.getName();
return Name.startswith("cpu_") && Name.endswith("_exec");
};
Function& CpuExec = find_unique(F.getParent()->functions(), IsCpuExec);
User *CallUser = find_unique(CpuExec.users(), [&F] (User *TheUser) {
auto *TheInstruction = dyn_cast<Instruction>(TheUser);
if (TheInstruction == nullptr)
return false;
return TheInstruction->getParent()->getParent() == &F;
});
auto *Call = cast<CallInst>(CallUser);
assert(Call->getCalledFunction() == &CpuExec);
Value *ExceptionIndex = TheModule->getOrInsertGlobal("exception_index",
CpuExec.getReturnType());
Value *LoadExceptionIndex = new LoadInst(ExceptionIndex, "", Call);
Call->replaceAllUsesWith(LoadExceptionIndex);
Call->eraseFromParent();
return true;
}
class CpuLoopExitPass : public llvm::ModulePass {
public:
static char ID;
CpuLoopExitPass() : llvm::ModulePass(ID), VM(0) { }
CpuLoopExitPass(VariableManager *VM) :
llvm::ModulePass(ID),
VM(VM) { }
bool runOnModule(llvm::Module& M) override;
private:
VariableManager *VM;
};
char CpuLoopExitPass::ID = 0;
static RegisterPass<CpuLoopExitPass> Y("cpu-loop-exit",
"cpu_loop_exit Pass",
false,
false);
static void purgeNoReturn(Function *F) {
auto &Context = F->getParent()->getContext();
if (F->hasFnAttribute(Attribute::NoReturn))
F->removeFnAttr(Attribute::NoReturn);
for (User *U : F->users())
if (auto *Call = dyn_cast<CallInst>(U))
if (Call->hasFnAttr(Attribute::NoReturn)) {
auto OldAttr = Call->getAttributes();
auto NewAttr = OldAttr.removeAttribute(Context,
AttributeSet::FunctionIndex,
Attribute::NoReturn);
Call->setAttributes(NewAttr);
}
}
static ReturnInst *createRet(Instruction *Position) {
Function *F = Position->getParent()->getParent();
purgeNoReturn(F);
Type *ReturnType = F->getFunctionType()->getReturnType();
if (ReturnType->isVoidTy()) {
return ReturnInst::Create(F->getParent()->getContext(), nullptr, Position);
} else if (ReturnType->isIntegerTy()) {
auto *Zero = ConstantInt::get(static_cast<IntegerType*>(ReturnType), 0);
return ReturnInst::Create(F->getParent()->getContext(), Zero, Position);
} else {
assert("Return type not supported");
}
return nullptr;
}
/// Find all calls to cpu_loop_exit and replace them with:
///
/// * call cpu_loop
/// * set cpu_loop_exiting = true
/// * return
///
/// Then look for all the callers of the function calling cpu_loop_exit and make
/// them check whether they should return immediately (cpu_loop_exiting == true)
/// or not.
/// Then when we reach the root function, set cpu_loop_exiting to false after
/// the call.
bool CpuLoopExitPass::runOnModule(llvm::Module& M) {
Function *CpuLoopExit = M.getFunction("cpu_loop_exit");
purgeNoReturn(CpuLoopExit);
// Nothing to do here
if (CpuLoopExit == nullptr)
return false;
Function *CpuLoop = M.getFunction("cpu_loop");
LLVMContext &Context = M.getContext();
IntegerType *BoolType = Type::getInt1Ty(Context);
std::set<Function *> FixedCallers;
Constant *CpuLoopExitingVariable = nullptr;
CpuLoopExitingVariable = new GlobalVariable(M,
BoolType,
false,
GlobalValue::CommonLinkage,
ConstantInt::getFalse(BoolType),
StringRef("cpu_loop_exiting"));
assert(CpuLoop != nullptr);
for (User *TheUser : CpuLoopExit->users()) {
auto *Call = cast<CallInst>(TheUser);
assert(Call->getCalledFunction() == CpuLoopExit);
// Call cpu_loop
auto *EnvType = CpuLoop->getFunctionType()->getParamType(0);
auto *AddressComputation = VM->computeEnvAddress(EnvType, Call);
CallInst::Create(CpuLoop, { AddressComputation }, "", Call);
// Set cpu_loop_exiting to true
new StoreInst(ConstantInt::getTrue(BoolType), CpuLoopExitingVariable, Call);
// Return immediately
createRet(Call);
auto *Unreach = cast<UnreachableInst>(&*++Call->getIterator());
Unreach->eraseFromParent();
// Remove the call to cpu_loop_exit
Function *Caller = Call->getParent()->getParent();
if (FixedCallers.find(Caller) == FixedCallers.end()) {
FixedCallers.insert(Caller);
std::queue<Value *> WorkList;
WorkList.push(Caller);
while (!WorkList.empty()) {
Value *F = WorkList.front();
WorkList.pop();
for (User *RecUser : F->users()) {
auto *RecCall = dyn_cast<CallInst>(RecUser);
if (RecCall == nullptr) {
auto *Cast = dyn_cast<ConstantExpr>(RecUser);
assert(Cast != nullptr && "Unexpected user");
assert(Cast->getOperand(0) == F && Cast->isCast());
WorkList.push(Cast);
continue;
}
Function *RecCaller = RecCall->getParent()->getParent();
// TODO: make this more reliable than using function name
if (RecCaller->getName() == "root") {
// If we got to the translated function, just reset cpu_loop_exiting
// to false
new StoreInst(ConstantInt::getFalse(BoolType),
CpuLoopExitingVariable,
&*++RecCall->getIterator());
} else {
// If the caller is a QEMU helper function make it check
// cpu_loop_exiting and if it's true, make it return
// Split BB
BasicBlock *OldBB = RecCall->getParent();
BasicBlock::iterator SplitPoint = ++RecCall->getIterator();
assert(SplitPoint != OldBB->end());
BasicBlock *NewBB = OldBB->splitBasicBlock(SplitPoint);
// Add a BB with a ret
BasicBlock *QuitBB = BasicBlock::Create(Context,
"cpu_loop_exit_return",
RecCaller,
NewBB);
UnreachableInst *Temp = new UnreachableInst(Context, QuitBB);
createRet(Temp);
Temp->eraseFromParent();
// Check value of cpu_loop_exiting
auto *Branch = cast<BranchInst>(&*++(RecCall->getIterator()));
auto *Compare = new ICmpInst(Branch,
CmpInst::ICMP_EQ,
new LoadInst(CpuLoopExitingVariable,
"",
Branch),
ConstantInt::getTrue(BoolType));
BranchInst::Create(QuitBB, NewBB, Compare, Branch);
Branch->eraseFromParent();
// Add to the work list only if it hasn't been fixed already
if (FixedCallers.find(RecCaller) == FixedCallers.end()) {
FixedCallers.insert(RecCaller);
WorkList.push(RecCaller);
}
}
}
}
}
}
for (User *TheUser : CpuLoopExit->users())
cast<Instruction>(TheUser)->eraseFromParent();
return true;
}
/// Removes all the basic blocks without predecessors from F
// TODO: this is not efficient, but it shouldn't be critical
static void purgeDeadBlocks(Function *F) {
std::vector<BasicBlock *> Kill;
do {
for (BasicBlock *Dead : Kill)
DeleteDeadBlock(Dead);
Kill.clear();
// Skip the first basic block
for (BasicBlock &BB : make_range(++F->begin(), F->end()))
if (pred_empty(&BB))
Kill.push_back(&BB);
} while (!Kill.empty());
}
void CodeGenerator::translate(uint64_t VirtualAddress,
std::string Name) {
// Declare useful functions
auto *AbortTy = FunctionType::get(Type::getVoidTy(Context), false);
auto *AbortFunction = TheModule->getOrInsertFunction("abort", AbortTy);
auto *TargetSetBrkFunction = HelpersModule->getFunction("target_set_brk");
TheModule->getOrInsertFunction("target_set_brk",
TargetSetBrkFunction->getFunctionType());
Function *CpuLoop = HelpersModule->getFunction("cpu_loop");
assert(CpuLoop != nullptr);
TheModule->getOrInsertFunction("cpu_loop", CpuLoop->getFunctionType());
TheModule->getOrInsertFunction("syscall_init",
FunctionType::get(Type::getVoidTy(Context),
{ },
false));
IRBuilder<> Builder(Context);
// Create main function
auto *MainType = FunctionType::get(Builder.getVoidTy(), false);
auto *MainFunction = Function::Create(MainType,
Function::ExternalLinkage,
Name,
TheModule.get());
Debug->newFunction(MainFunction);
// Create the first basic block and create a placeholder for variable
// allocations
BasicBlock *Entry = BasicBlock::Create(Context,
"entrypoint",
MainFunction);
Builder.SetInsertPoint(Entry);
// Instantiate helpers
VariableManager Variables(*TheModule,
*HelpersModule,
TargetArchitecture);
auto *PCReg = Variables.getByEnvOffset(ptc.pc, "pc").first;
JumpTargetManager JumpTargets(MainFunction,
PCReg,
SourceArchitecture,
Binary,
EnableOSRA);
if (VirtualAddress == 0) {
JumpTargets.harvestGlobalData();
VirtualAddress = EntryPoint;
}
dbg << "Entry address: 0x" << std::hex << VirtualAddress << std::endl;
BasicBlock *Head = JumpTargets.getBlockAt(VirtualAddress);
// Fake jump to the dispatcher. This way all the blocks are always reachable.
// Also, use this branch as the delimiter to create local variables.
auto *Delimiter = Builder.CreateCondBr(Builder.getTrue(),
Head,
JumpTargets.dispatcher());
std::tie(VirtualAddress, Entry) = JumpTargets.peek();
std::vector<BasicBlock *> Blocks;
InstructionTranslator Translator(Builder,
Variables,
JumpTargets,
Blocks,
SourceArchitecture,
TargetArchitecture);
while (Entry != nullptr) {
Builder.SetInsertPoint(Entry);
Translator.reset();
// TODO: rename this type
PTCInstructionListPtr InstructionList(new PTCInstructionList);
size_t ConsumedSize = 0;
ConsumedSize = ptc.translate(VirtualAddress, InstructionList.get());
JumpTargets.registerOriginalBB(VirtualAddress, ConsumedSize);
DBG("ptc", dumpTranslation(dbg, InstructionList.get()));
Variables.newFunction(Delimiter, InstructionList.get());
unsigned j = 0;
MDNode* MDOriginalInstr = nullptr;
bool StopTranslation = false;
uint64_t PC = VirtualAddress;
uint64_t NextPC = 0;
uint64_t EndPC = VirtualAddress + ConsumedSize;
const auto InstructionCount = InstructionList->instruction_count;
using IT = InstructionTranslator;
IT::TranslationResult Result;
bool ForceNewBlock = false;
// Handle the first PTC_INSTRUCTION_op_debug_insn_start
{
PTCInstruction *NextInstruction = nullptr;
for (unsigned k = 1; k < InstructionCount; k++) {
PTCInstruction *I = &InstructionList->instructions[k];
if (I->opc == PTC_INSTRUCTION_op_debug_insn_start) {
NextInstruction = I;
break;
}
}
PTCInstruction *Instruction = &InstructionList->instructions[j];
std::tie(Result,
MDOriginalInstr,
PC,
NextPC) = Translator.newInstruction(Instruction,
NextInstruction,
EndPC,
true,
false);
j++;
}
// TODO: shall we move this whole loop in InstructionTranslator?
for (; j < InstructionCount && !StopTranslation; j++) {
PTCInstruction Instruction = InstructionList->instructions[j];
PTCOpcode Opcode = Instruction.opc;
Blocks.clear();
Blocks.push_back(Builder.GetInsertBlock());
switch(Opcode) {
case PTC_INSTRUCTION_op_discard:
// Instructions we don't even consider
break;
case PTC_INSTRUCTION_op_debug_insn_start:
{
// Find next instruction, if there is one
PTCInstruction *NextInstruction = nullptr;
for (unsigned k = j + 1; k < InstructionCount; k++) {
PTCInstruction *I = &InstructionList->instructions[k];
if (I->opc == PTC_INSTRUCTION_op_debug_insn_start) {
NextInstruction = I;
break;
}
}
std::tie(Result,
MDOriginalInstr,
PC,
NextPC) = Translator.newInstruction(&Instruction,
NextInstruction,
EndPC,
false,
ForceNewBlock);
ForceNewBlock = false;
break;
}
case PTC_INSTRUCTION_op_call:
{
Result = Translator.translateCall(&Instruction);
// Sometimes libtinycode terminates a basic block with a call, in this
// case force a fallthrough
auto &IL = InstructionList;
if (j == IL->instruction_count - 1) {
using JTM = JumpTargetManager;
Builder.CreateBr(notNull(JumpTargets.registerJT(EndPC,
JTM::PostHelper)));
}
break;
}
default:
Result = Translator.translate(&Instruction, PC, NextPC);
}
switch (Result) {
case IT::Success:
// No-op
break;
case IT::Abort:
Builder.CreateCall(AbortFunction);
Builder.CreateUnreachable();
StopTranslation = true;
break;
case IT::Stop:
StopTranslation = true;
break;
case IT::ForceNewPC:
ForceNewBlock = true;
break;
}
// Create a new metadata referencing the PTC instruction we have just
// translated
std::stringstream PTCStringStream;
dumpInstruction(PTCStringStream, InstructionList.get(), j);
std::string PTCString = PTCStringStream.str() + "\n";
MDString *MDPTCString = MDString::get(Context, PTCString);
MDNode* MDPTCInstr = MDNode::getDistinct(Context, MDPTCString);
// Set metadata for all the new instructions
for (BasicBlock *Block : Blocks) {
BasicBlock::iterator I = Block->end();
while (I != Block->begin() && !(--I)->hasMetadata()) {
I->setMetadata(OriginalInstrMDKind, MDOriginalInstr);
I->setMetadata(PTCInstrMDKind, MDPTCInstr);
}
}
} // End loop over instructions
if (ForceNewBlock)
JumpTargets.registerJT(EndPC, JumpTargetManager::PostHelper);
// We might have a leftover block, probably due to the block created after
// the last call to exit_tb
auto *LastBlock = Builder.GetInsertBlock();
if (LastBlock->empty())
LastBlock->eraseFromParent();
else if (!LastBlock->rbegin()->isTerminator()) {
// Something went wrong, probably a mistranslation
Builder.CreateUnreachable();
}
// Obtain a new program counter to translate
std::tie(VirtualAddress, Entry) = JumpTargets.peek();
} // End translations loop
legacy::FunctionPassManager CpuLoopPM(TheModule.get());
CpuLoopPM.add(new LoopInfoWrapperPass());
CpuLoopPM.add(new CpuLoopFunctionPass());
CpuLoopPM.run(*CpuLoop);
// CpuLoopFunctionPass expects a variable name exception_index to exist
Variables.getByEnvOffset(ptc.exception_index, "exception_index");
// Handle some specific QEMU functions as no-ops or abort
auto NoOpFunctionNames = make_array<const char *>("qemu_log_mask",
"fprintf",
"cpu_dump_state",
"mmap_lock",
"mmap_unlock",
"pthread_cond_broadcast",
"pthread_mutex_unlock",
"pthread_mutex_lock",
"pthread_cond_wait",
"pthread_cond_signal",
"cpu_exit",
"start_exclusive",
"process_pending_signals",
"end_exclusive");
auto AbortFunctionNames = make_array<const char *>("cpu_restore_state",
"gdb_handlesig",
"queue_signal",
"cpu_mips_exec",
// syscall.c
"print_syscall",
"print_syscall_ret",
"do_ioctl_dm",
// ARM cpu_loop
"EmulateAll",
"cpu_abort",
"do_arm_semihosting");
// EmulateAll: requires access to the opcode
// do_arm_semihosting: we don't care about semihosting
// From syscall.c
new GlobalVariable(*TheModule,
Type::getInt32Ty(Context),
false,
GlobalValue::CommonLinkage,
ConstantInt::get(Type::getInt32Ty(Context), 0),
StringRef("do_strace"));
for (auto Name : NoOpFunctionNames)
replaceFunctionWithRet(HelpersModule->getFunction(Name), 0);
for (auto Name : AbortFunctionNames) {
Function *TheFunction = HelpersModule->getFunction(Name);
if (TheFunction != nullptr) {
assert(HelpersModule->getFunction("abort") != nullptr);
BasicBlock *NewBody = replaceFunction(TheFunction);
CallInst::Create(HelpersModule->getFunction("abort"), { }, NewBody);
new UnreachableInst(Context, NewBody);
}
}
replaceFunctionWithRet(HelpersModule->getFunction("page_check_range"), 1);
replaceFunctionWithRet(HelpersModule->getFunction("page_get_flags"),
0xffffffff);
// HACK: the LLVM linker does not import non-static functions anymore if
// LinkOnlyNeeded is specified. We don't want this so mark all the
// non-static symbols not directly imported as static.
{
std::set<StringRef> Declarations;
for (auto& GV : TheModule->functions())
if (GV.isDeclaration())
Declarations.insert(GV.getName());
for (auto& GV : TheModule->globals())
if (GV.isDeclaration())
Declarations.insert(GV.getName());
for (auto& GV : HelpersModule->functions())
if (!GV.isDeclaration()
&& Declarations.find(GV.getName()) == Declarations.end()
&& GV.hasExternalLinkage())
GV.setLinkage(GlobalValue::InternalLinkage);
for (auto& GV : HelpersModule->globals())
if (!GV.isDeclaration()
&& Declarations.find(GV.getName()) == Declarations.end()
&& GV.hasExternalLinkage())
GV.setLinkage(GlobalValue::InternalLinkage);
}
Linker TheLinker(*TheModule);
bool Result = TheLinker.linkInModule(std::move(HelpersModule),
Linker::LinkOnlyNeeded);
assert(!Result && "Linking failed");
(void) Result;
Variables.setDataLayout(&TheModule->getDataLayout());
legacy::PassManager PM;
PM.add(createSROAPass());
PM.add(new CpuLoopExitPass(&Variables));
PM.add(Variables.createCorrectCPUStateUsagePass());
PM.add(createDeadCodeEliminationPass());
PM.run(*TheModule);
// TODO: transform the following in passes?
JumpTargets.collectBBSummary(BBSummaryPath);
JumpTargets.translateIndirectJumps();
JumpTargets.finalizeJumpTargets();
purgeDeadBlocks(MainFunction);
legacy::FunctionPassManager FPM(&*TheModule);
FPM.add(new FunctionBoundariesDetectionPass(&JumpTargets, ""));
FPM.run(*MainFunction);
Translator.finalizeNewPCMarkers(CoveragePath, EnableTracing);
Debug->generateDebugInfo();
}
void CodeGenerator::serialize() {
// Ask the debug handler if it already has a good copy of the IR, if not dump
// it
if (!Debug->copySource()) {
std::ofstream Output(OutputPath);
Debug->print(Output, false);
}
}
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