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revng-revng/codegenerator.cpp
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Andrea Gussoni cf42e497aa Introduce the Function Isolation Pass 
This commit introduces the Function Isolation Pass. We use the
information provided by the Function Boundaries Detection Pass to
organize the code that `revamb` places inside the `root` function in
different LLVM functions. To do this we obviously need to introduce some
changes and tricks to handle the execution of the translated program.

The main idea is to have two different realms (one where the isolated
functions live, one in which we have basically the old root function).
We start the execution from the realm of the *non isolated* functions,
and we transfer, as soon as possible, the execution to the *isolated
functions* realm. We then have a fallback mechanism to restore the
execution in the right place in the *non isolated* functions realm, and
so on.

The largest change, besides the re-organization of the code in different
functions, is the use of the exception handling mechanism provided by
the LLVM framework in order to be able to manage the switch between the
two realms.

We also introduce the `support.h` header file, which contains a couple
of definitions used by `support.c` and that need to be shared with some
of the components involved in the translation process. We have defined
some helper functions, directly in C, that we use both for handling the
exception mechanism and for giving extra debug informations when an
exception is raised.

The `revamb-dump` utility now supports the `-i` option to specify the
path were to save the new LLVM module.

The `translate` utility now supports the `-i` option that produces a
binary in which the function isolation has been applied.

We also introduced some tests that apply the function isolation pass to
the `Runtime/` tests already present. In this way we can verify that the
translation and the following function isolation preserve the behavior
of the program.

When serializing the new LLVM module we regenerate the metadata used for
debug purposes, and for doing this, since we not longer have only the
`root` function, we have changed some details in the `DebugHelper` class
in order to be able to emit the metadata for all the functions of our
interest in a single shot.
2018-04-22 15:19:36 +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/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(BinaryFile &Binary,
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 DetectFunctionBoundaries,
bool EnableLinking,
bool ExternalCSVs) :
TargetArchitecture(Target),
Context(getGlobalContext()),
TheModule((new Module("top", Context))),
OutputPath(Output),
Debug(new DebugHelper(Output, Debug, TheModule.get(), DebugInfo)),
Binary(Binary),
EnableOSRA(EnableOSRA),
DetectFunctionBoundaries(DetectFunctionBoundaries),
EnableLinking(EnableLinking),
ExternalCSVs(ExternalCSVs)
{
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;
// 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,
Binary.architecture().pointerSize());
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", Binary.programHeaderSize());
createConstGlobal("e_phnum", Binary.programHeadersCount());
createConstGlobal("phdr_address", Binary.programHeadersAddress());
for (SegmentInfo &Segment : Binary.segments()) {
// 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(Segment.StartVirtualAddress,
static_cast<const void *>(Segment.Data.data()),
static_cast<size_t>(Segment.Data.size()));
}
std::string Name = Segment.generateName();
// Get data and size
auto *DataType = ArrayType::get(Uint8Ty, Segment.size());
Constant *TheData = nullptr;
if (Segment.size() == Segment.Data.size()) {
// Create the array directly from the mmap'd ELF
TheData = ConstantDataArray::get(Context, Segment.Data);
} 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[]>(Segment.size());
::memcpy(FullData.get(),
Segment.Data.data(),
Segment.Data.size());
::bzero(FullData.get() + Segment.Data.size(),
Segment.size() - Segment.Data.size());
auto DataRef = ArrayRef<uint8_t>(FullData.get(), Segment.size());
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);
// Write the linking info CSV
LinkingInfoStream << "." << Name
<< ",0x" << std::hex << Segment.StartVirtualAddress
<< ",0x" << std::hex << Segment.EndVirtualAddress
<< std::endl;
}
}
Function *CodeGenerator::importHelperFunctionDefinition(StringRef Name) {
Function *HelperFunction = HelpersModule->getFunction(Name);
FunctionType *HelperType = HelperFunction->getFunctionType();
return cast<Function>(TheModule->getOrInsertFunction(Name, HelperType));
}
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();
}
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");
// Nothing to do here
if (CpuLoopExit == nullptr)
return false;
purgeNoReturn(CpuLoopExit);
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);
std::queue<User *> CpuLoopExitUsers;
for (User *TheUser : CpuLoopExit->users())
CpuLoopExitUsers.push(TheUser);
while (!CpuLoopExitUsers.empty()) {
auto *Call = cast<CallInst>(CpuLoopExitUsers.front());
CpuLoopExitUsers.pop();
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();
Function *Caller = Call->getParent()->getParent();
// Remove the call to cpu_loop_exit
Call->eraseFromParent();
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);
}
}
}
}
}
}
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) {
using FT = FunctionType;
// Declare useful functions
auto *AbortTy = FunctionType::get(Type::getVoidTy(Context), false);
auto *AbortFunction = TheModule->getOrInsertFunction("abort", AbortTy);
importHelperFunctionDefinition("target_set_brk");
TheModule->getOrInsertFunction("syscall_init",
FT::get(Type::getVoidTy(Context), { }, false));
// Instantiate helpers
VariableManager Variables(*TheModule, *HelpersModule, TargetArchitecture);
GlobalVariable *PCReg = Variables.getByEnvOffset(ptc.pc, "pc").first;
GlobalVariable *SPReg = Variables.getByEnvOffset(ptc.sp, "sp").first;
IRBuilder<> Builder(Context);
// Create main function
auto *MainType = FT::get(Builder.getVoidTy(),
{ SPReg->getType()->getPointerElementType() },
false);
auto *MainFunction = Function::Create(MainType,
Function::ExternalLinkage,
"root",
TheModule.get());
// Create the first basic block and create a placeholder for variable
// allocations
BasicBlock *Entry = BasicBlock::Create(Context, "entrypoint", MainFunction);
Builder.SetInsertPoint(Entry);
// Create revamb.inputarch named metadata.
QuickMetadata QMD(Context);
NamedMDNode *InputArchMD;
const char *MDName = "revamb.input.architecture";
InputArchMD = TheModule->getOrInsertNamedMetadata(MDName);
const Architecture &Arch = Binary.architecture();
// Currently revamb.inputarch is composed as follows:
//
// revamb.inputarch = {
// InstructionAlignment,
// DelaySlotSize,
// PCRegisterName,
// SPRegisterName
// }
auto *Tuple = MDTuple::get(Context, {
QMD.get(static_cast<uint32_t>(Arch.instructionAlignment())),
QMD.get(static_cast<uint32_t>(Arch.delaySlotSize())),
QMD.get("pc"),
QMD.get(Arch.stackPointerRegister()),
});
InputArchMD->addOperand(Tuple);
// Create an instance of JumpTargetManager
JumpTargetManager JumpTargets(MainFunction, PCReg, Binary, EnableOSRA);
if (VirtualAddress == 0) {
JumpTargets.harvestGlobalData();
VirtualAddress = Binary.entryPoint();
}
JumpTargets.registerJT(VirtualAddress, JumpTargetManager::GlobalData);
// Initialize the program counter
auto *StartPC = ConstantInt::get(PCReg->getType()->getPointerElementType(),
VirtualAddress);
// Use this instruction as the delimiter for local variables
auto *Delimiter = Builder.CreateStore(StartPC, PCReg);
// We need to remember this instruction so we can later insert a call here.
// The problem is that up until now we don't know where our CPUState structure is.
// After the translation we will and use this information to create a call to
// a helper function.
// TODO: we need a more elegant solution here
auto *InitEnvInsertPoint = Delimiter;
Builder.CreateStore(&*MainFunction->arg_begin(), SPReg);
// Fake jumps to the dispatcher-related basic blocks. This way all the blocks
// are always reachable.
auto *ReachSwitch = Builder.CreateSwitch(Builder.getInt8(0),
JumpTargets.dispatcher());
ReachSwitch->addCase(Builder.getInt8(1), JumpTargets.anyPC());
ReachSwitch->addCase(Builder.getInt8(2), JumpTargets.unexpectedPC());
std::tie(VirtualAddress, Entry) = JumpTargets.peek();
std::vector<BasicBlock *> Blocks;
InstructionTranslator Translator(Builder,
Variables,
JumpTargets,
Blocks,
Binary.architecture(),
TargetArchitecture);
while (Entry != nullptr) {
Builder.SetInsertPoint(Entry);
// TODO: what if create a new instance of an InstructionTranslator here?
Translator.reset();
// TODO: rename this type
PTCInstructionListPtr InstructionList(new PTCInstructionList);
size_t ConsumedSize = 0;
ConsumedSize = ptc.translate(VirtualAddress, InstructionList.get());
SmallSet<unsigned, 1> ToIgnore;
ToIgnore = Translator.preprocess(InstructionList.get());
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
&& ToIgnore.count(k) == 0) {
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++) {
if (ToIgnore.count(j) != 0)
continue;
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
&& ToIgnore.count(k) == 0) {
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
importHelperFunctionDefinition("cpu_loop");
Function *CpuLoop = HelpersModule->getFunction("cpu_loop");
assert(CpuLoop != nullptr);
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
// Initializes the CPUState which is important on x86 architecture.
if (HelpersModule->getFunction("initialize_env") != nullptr) {
Function *InitEnv = importHelperFunctionDefinition("initialize_env");
auto *CPUStateType = InitEnv->getFunctionType()->getParamType(0);
Instruction *InsertBefore = InitEnvInsertPoint;
auto *AddressComputation = Variables.computeEnvAddress(CPUStateType, InsertBefore);
CallInst::Create(InitEnv, { AddressComputation }, "", InsertBefore);
}
// 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);
}
if (EnableLinking) {
Linker TheLinker(*TheModule);
bool Result = TheLinker.linkInModule(std::move(HelpersModule),
Linker::LinkOnlyNeeded);
assert(!Result && "Linking failed");
}
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);
JumpTargets.finalizeJumpTargets();
purgeDeadBlocks(MainFunction);
if (DetectFunctionBoundaries) {
legacy::FunctionPassManager FPM(&*TheModule);
FPM.add(new FunctionBoundariesDetectionPass(&JumpTargets, ""));
FPM.run(*MainFunction);
}
JumpTargets.createJTReasonMD();
JumpTargets.noReturn().cleanup();
Translator.finalizeNewPCMarkers(CoveragePath);
Variables.finalize(ExternalCSVs);
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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