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llvm/lib/MC/MCAnalysis/MCObjectDisassembler.cpp

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//===- lib/MC/MCObjectDisassembler.cpp ------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCObjectDisassembler.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCAnalysis/MCAtom.h"
#include "llvm/MC/MCAnalysis/MCFunction.h"
#include "llvm/MC/MCAnalysis/MCModule.h"
#include "llvm/MC/MCAnalysis/MCObjectSymbolizer.h"
#include "llvm/MC/MCDisassembler.h"
#include "llvm/MC/MCInstrAnalysis.h"
#include "llvm/Object/MachO.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/MachO.h"
#include "llvm/Support/MemoryObject.h"
#include "llvm/Support/StringRefMemoryObject.h"
#include "llvm/Support/raw_ostream.h"
#include <map>
using namespace llvm;
using namespace object;
#define DEBUG_TYPE "mc"
MCObjectDisassembler::MCObjectDisassembler(const ObjectFile &Obj,
const MCDisassembler &Dis,
const MCInstrAnalysis &MIA)
: Obj(Obj), Dis(Dis), MIA(MIA), MOS(nullptr) {}
uint64_t MCObjectDisassembler::getEntrypoint() {
for (const SymbolRef &Symbol : Obj.symbols()) {
StringRef Name;
Symbol.getName(Name);
if (Name == "main" || Name == "_main") {
uint64_t Entrypoint;
Symbol.getAddress(Entrypoint);
return getEffectiveLoadAddr(Entrypoint);
}
}
return 0;
}
ArrayRef<uint64_t> MCObjectDisassembler::getStaticInitFunctions() {
return None;
}
ArrayRef<uint64_t> MCObjectDisassembler::getStaticExitFunctions() {
return None;
}
MemoryObject *MCObjectDisassembler::getRegionFor(uint64_t Addr) {
// FIXME: Keep track of object sections.
return FallbackRegion.get();
}
uint64_t MCObjectDisassembler::getEffectiveLoadAddr(uint64_t Addr) {
return Addr;
}
uint64_t MCObjectDisassembler::getOriginalLoadAddr(uint64_t Addr) {
return Addr;
}
MCModule *MCObjectDisassembler::buildEmptyModule() {
MCModule *Module = new MCModule;
Module->Entrypoint = getEntrypoint();
return Module;
}
MCModule *MCObjectDisassembler::buildModule(bool withCFG) {
MCModule *Module = buildEmptyModule();
buildSectionAtoms(Module);
if (withCFG)
buildCFG(Module);
return Module;
}
void MCObjectDisassembler::buildSectionAtoms(MCModule *Module) {
for (const SectionRef &Section : Obj.sections()) {
bool isText;
Section.isText(isText);
bool isData;
Section.isData(isData);
if (!isData && !isText)
continue;
uint64_t StartAddr;
Section.getAddress(StartAddr);
uint64_t SecSize;
Section.getSize(SecSize);
if (StartAddr == UnknownAddressOrSize || SecSize == UnknownAddressOrSize)
continue;
StartAddr = getEffectiveLoadAddr(StartAddr);
StringRef Contents;
Section.getContents(Contents);
StringRefMemoryObject memoryObject(Contents, StartAddr);
// We don't care about things like non-file-backed sections yet.
if (Contents.size() != SecSize || !SecSize)
continue;
uint64_t EndAddr = StartAddr + SecSize - 1;
StringRef SecName;
Section.getName(SecName);
if (isText) {
MCTextAtom *Text = nullptr;
MCDataAtom *InvalidData = nullptr;
uint64_t InstSize;
for (uint64_t Index = 0; Index < SecSize; Index += InstSize) {
const uint64_t CurAddr = StartAddr + Index;
MCInst Inst;
if (Dis.getInstruction(Inst, InstSize, memoryObject, CurAddr, nulls(),
nulls())) {
if (!Text) {
Text = Module->createTextAtom(CurAddr, CurAddr);
Text->setName(SecName);
}
Text->addInst(Inst, InstSize);
InvalidData = nullptr;
} else {
assert(InstSize && "getInstruction() consumed no bytes");
if (!InvalidData) {
Text = nullptr;
InvalidData = Module->createDataAtom(CurAddr, CurAddr+InstSize - 1);
}
for (uint64_t I = 0; I < InstSize; ++I)
InvalidData->addData(Contents[Index+I]);
}
}
} else {
MCDataAtom *Data = Module->createDataAtom(StartAddr, EndAddr);
Data->setName(SecName);
for (uint64_t Index = 0; Index < SecSize; ++Index)
Data->addData(Contents[Index]);
}
}
}
namespace {
struct BBInfo;
typedef SmallPtrSet<BBInfo*, 2> BBInfoSetTy;
struct BBInfo {
MCTextAtom *Atom;
MCBasicBlock *BB;
BBInfoSetTy Succs;
BBInfoSetTy Preds;
MCObjectDisassembler::AddressSetTy SuccAddrs;
BBInfo() : Atom(nullptr), BB(nullptr) {}
void addSucc(BBInfo &Succ) {
Succs.insert(&Succ);
Succ.Preds.insert(this);
}
};
}
static void RemoveDupsFromAddressVector(MCObjectDisassembler::AddressSetTy &V) {
std::sort(V.begin(), V.end());
V.erase(std::unique(V.begin(), V.end()), V.end());
}
void MCObjectDisassembler::buildCFG(MCModule *Module) {
typedef std::map<uint64_t, BBInfo> BBInfoByAddrTy;
BBInfoByAddrTy BBInfos;
AddressSetTy Splits;
AddressSetTy Calls;
for (const SymbolRef &Symbol : Obj.symbols()) {
SymbolRef::Type SymType;
Symbol.getType(SymType);
if (SymType == SymbolRef::ST_Function) {
uint64_t SymAddr;
Symbol.getAddress(SymAddr);
SymAddr = getEffectiveLoadAddr(SymAddr);
Calls.push_back(SymAddr);
Splits.push_back(SymAddr);
}
}
assert(Module->func_begin() == Module->func_end()
&& "Module already has a CFG!");
// First, determine the basic block boundaries and call targets.
for (MCModule::atom_iterator AI = Module->atom_begin(),
AE = Module->atom_end();
AI != AE; ++AI) {
MCTextAtom *TA = dyn_cast<MCTextAtom>(*AI);
if (!TA) continue;
Calls.push_back(TA->getBeginAddr());
BBInfos[TA->getBeginAddr()].Atom = TA;
for (MCTextAtom::const_iterator II = TA->begin(), IE = TA->end();
II != IE; ++II) {
if (MIA.isTerminator(II->Inst))
Splits.push_back(II->Address + II->Size);
uint64_t Target;
if (MIA.evaluateBranch(II->Inst, II->Address, II->Size, Target)) {
if (MIA.isCall(II->Inst))
Calls.push_back(Target);
Splits.push_back(Target);
}
}
}
RemoveDupsFromAddressVector(Splits);
RemoveDupsFromAddressVector(Calls);
// Split text atoms into basic block atoms.
for (AddressSetTy::const_iterator SI = Splits.begin(), SE = Splits.end();
SI != SE; ++SI) {
MCAtom *A = Module->findAtomContaining(*SI);
if (!A) continue;
MCTextAtom *TA = cast<MCTextAtom>(A);
if (TA->getBeginAddr() == *SI)
continue;
MCTextAtom *NewAtom = TA->split(*SI);
BBInfos[NewAtom->getBeginAddr()].Atom = NewAtom;
StringRef BBName = TA->getName();
BBName = BBName.substr(0, BBName.find_last_of(':'));
NewAtom->setName((BBName + ":" + utohexstr(*SI)).str());
}
// Compute succs/preds.
for (MCModule::atom_iterator AI = Module->atom_begin(),
AE = Module->atom_end();
AI != AE; ++AI) {
MCTextAtom *TA = dyn_cast<MCTextAtom>(*AI);
if (!TA) continue;
BBInfo &CurBB = BBInfos[TA->getBeginAddr()];
const MCDecodedInst &LI = TA->back();
if (MIA.isBranch(LI.Inst)) {
uint64_t Target;
if (MIA.evaluateBranch(LI.Inst, LI.Address, LI.Size, Target))
CurBB.addSucc(BBInfos[Target]);
if (MIA.isConditionalBranch(LI.Inst))
CurBB.addSucc(BBInfos[LI.Address + LI.Size]);
} else if (!MIA.isTerminator(LI.Inst))
CurBB.addSucc(BBInfos[LI.Address + LI.Size]);
}
// Create functions and basic blocks.
for (AddressSetTy::const_iterator CI = Calls.begin(), CE = Calls.end();
CI != CE; ++CI) {
BBInfo &BBI = BBInfos[*CI];
if (!BBI.Atom) continue;
MCFunction &MCFN = *Module->createFunction(BBI.Atom->getName());
// Create MCBBs.
SmallSetVector<BBInfo*, 16> Worklist;
Worklist.insert(&BBI);
for (size_t wi = 0; wi < Worklist.size(); ++wi) {
BBInfo *BBI = Worklist[wi];
if (!BBI->Atom)
continue;
BBI->BB = &MCFN.createBlock(*BBI->Atom);
// Add all predecessors and successors to the worklist.
for (BBInfoSetTy::iterator SI = BBI->Succs.begin(), SE = BBI->Succs.end();
SI != SE; ++SI)
Worklist.insert(*SI);
for (BBInfoSetTy::iterator PI = BBI->Preds.begin(), PE = BBI->Preds.end();
PI != PE; ++PI)
Worklist.insert(*PI);
}
// Set preds/succs.
for (size_t wi = 0; wi < Worklist.size(); ++wi) {
BBInfo *BBI = Worklist[wi];
MCBasicBlock *MCBB = BBI->BB;
if (!MCBB)
continue;
for (BBInfoSetTy::iterator SI = BBI->Succs.begin(), SE = BBI->Succs.end();
SI != SE; ++SI)
if ((*SI)->BB)
MCBB->addSuccessor((*SI)->BB);
for (BBInfoSetTy::iterator PI = BBI->Preds.begin(), PE = BBI->Preds.end();
PI != PE; ++PI)
if ((*PI)->BB)
MCBB->addPredecessor((*PI)->BB);
}
}
}
// Basic idea of the disassembly + discovery:
//
// start with the wanted address, insert it in the worklist
// while worklist not empty, take next address in the worklist:
// - check if atom exists there
// - if middle of atom:
// - split basic blocks referencing the atom
// - look for an already encountered BBInfo (using a map<atom, bbinfo>)
// - if there is, split it (new one, fallthrough, move succs, etc..)
// - if start of atom: nothing else to do
// - if no atom: create new atom and new bbinfo
// - look at the last instruction in the atom, add succs to worklist
// for all elements in the worklist:
// - create basic block, update preds/succs, etc..
//
MCBasicBlock *MCObjectDisassembler::getBBAt(MCModule *Module, MCFunction *MCFN,
uint64_t BBBeginAddr,
AddressSetTy &CallTargets,
AddressSetTy &TailCallTargets) {
typedef std::map<uint64_t, BBInfo> BBInfoByAddrTy;
typedef SmallSetVector<uint64_t, 16> AddrWorklistTy;
BBInfoByAddrTy BBInfos;
AddrWorklistTy Worklist;
Worklist.insert(BBBeginAddr);
for (size_t wi = 0; wi < Worklist.size(); ++wi) {
const uint64_t BeginAddr = Worklist[wi];
BBInfo *BBI = &BBInfos[BeginAddr];
MCTextAtom *&TA = BBI->Atom;
assert(!TA && "Discovered basic block already has an associated atom!");
// Look for an atom at BeginAddr.
if (MCAtom *A = Module->findAtomContaining(BeginAddr)) {
// FIXME: We don't care about mixed atoms, see above.
TA = cast<MCTextAtom>(A);
// The found atom doesn't begin at BeginAddr, we have to split it.
if (TA->getBeginAddr() != BeginAddr) {
// FIXME: Handle overlapping atoms: middle-starting instructions, etc..
MCTextAtom *NewTA = TA->split(BeginAddr);
// Look for an already encountered basic block that needs splitting
BBInfoByAddrTy::iterator It = BBInfos.find(TA->getBeginAddr());
if (It != BBInfos.end() && It->second.Atom) {
BBI->SuccAddrs = It->second.SuccAddrs;
It->second.SuccAddrs.clear();
It->second.SuccAddrs.push_back(BeginAddr);
}
TA = NewTA;
}
BBI->Atom = TA;
} else {
// If we didn't find an atom, then we have to disassemble to create one!
MemoryObject *Region = getRegionFor(BeginAddr);
if (!Region)
llvm_unreachable(("Couldn't find suitable region for disassembly at " +
utostr(BeginAddr)).c_str());
uint64_t InstSize;
uint64_t EndAddr = Region->getBase() + Region->getExtent();
// We want to stop before the next atom and have a fallthrough to it.
if (MCTextAtom *NextAtom =
cast_or_null<MCTextAtom>(Module->findFirstAtomAfter(BeginAddr)))
EndAddr = std::min(EndAddr, NextAtom->getBeginAddr());
for (uint64_t Addr = BeginAddr; Addr < EndAddr; Addr += InstSize) {
MCInst Inst;
if (Dis.getInstruction(Inst, InstSize, *Region, Addr, nulls(),
nulls())) {
if (!TA)
TA = Module->createTextAtom(Addr, Addr);
TA->addInst(Inst, InstSize);
} else {
// We don't care about splitting mixed atoms either.
llvm_unreachable("Couldn't disassemble instruction in atom.");
}
uint64_t BranchTarget;
if (MIA.evaluateBranch(Inst, Addr, InstSize, BranchTarget)) {
if (MIA.isCall(Inst))
CallTargets.push_back(BranchTarget);
}
if (MIA.isTerminator(Inst))
break;
}
BBI->Atom = TA;
}
assert(TA && "Couldn't disassemble atom, none was created!");
assert(TA->begin() != TA->end() && "Empty atom!");
MemoryObject *Region = getRegionFor(TA->getBeginAddr());
assert(Region && "Couldn't find region for already disassembled code!");
uint64_t EndRegion = Region->getBase() + Region->getExtent();
// Now we have a basic block atom, add successors.
// Add the fallthrough block.
if ((MIA.isConditionalBranch(TA->back().Inst) ||
!MIA.isTerminator(TA->back().Inst)) &&
(TA->getEndAddr() + 1 < EndRegion)) {
BBI->SuccAddrs.push_back(TA->getEndAddr() + 1);
Worklist.insert(TA->getEndAddr() + 1);
}
// If the terminator is a branch, add the target block.
if (MIA.isBranch(TA->back().Inst)) {
uint64_t BranchTarget;
if (MIA.evaluateBranch(TA->back().Inst, TA->back().Address,
TA->back().Size, BranchTarget)) {
StringRef ExtFnName;
if (MOS)
ExtFnName =
MOS->findExternalFunctionAt(getOriginalLoadAddr(BranchTarget));
if (!ExtFnName.empty()) {
TailCallTargets.push_back(BranchTarget);
CallTargets.push_back(BranchTarget);
} else {
BBI->SuccAddrs.push_back(BranchTarget);
Worklist.insert(BranchTarget);
}
}
}
}
for (size_t wi = 0, we = Worklist.size(); wi != we; ++wi) {
const uint64_t BeginAddr = Worklist[wi];
BBInfo *BBI = &BBInfos[BeginAddr];
assert(BBI->Atom && "Found a basic block without an associated atom!");
// Look for a basic block at BeginAddr.
BBI->BB = MCFN->find(BeginAddr);
if (BBI->BB) {
// FIXME: check that the succs/preds are the same
continue;
}
// If there was none, we have to create one from the atom.
BBI->BB = &MCFN->createBlock(*BBI->Atom);
}
for (size_t wi = 0, we = Worklist.size(); wi != we; ++wi) {
const uint64_t BeginAddr = Worklist[wi];
BBInfo *BBI = &BBInfos[BeginAddr];
MCBasicBlock *BB = BBI->BB;
RemoveDupsFromAddressVector(BBI->SuccAddrs);
for (AddressSetTy::const_iterator SI = BBI->SuccAddrs.begin(),
SE = BBI->SuccAddrs.end();
SI != SE; ++SI) {
MCBasicBlock *Succ = BBInfos[*SI].BB;
BB->addSuccessor(Succ);
Succ->addPredecessor(BB);
}
}
assert(BBInfos[Worklist[0]].BB &&
"No basic block created at requested address?");
return BBInfos[Worklist[0]].BB;
}
MCFunction *
MCObjectDisassembler::createFunction(MCModule *Module, uint64_t BeginAddr,
AddressSetTy &CallTargets,
AddressSetTy &TailCallTargets) {
// First, check if this is an external function.
StringRef ExtFnName;
if (MOS)
ExtFnName = MOS->findExternalFunctionAt(getOriginalLoadAddr(BeginAddr));
if (!ExtFnName.empty())
return Module->createFunction(ExtFnName);
// If it's not, look for an existing function.
for (MCModule::func_iterator FI = Module->func_begin(),
FE = Module->func_end();
FI != FE; ++FI) {
if ((*FI)->empty())
continue;
// FIXME: MCModule should provide a findFunctionByAddr()
if ((*FI)->getEntryBlock()->getInsts()->getBeginAddr() == BeginAddr)
return FI->get();
}
// Finally, just create a new one.
MCFunction *MCFN = Module->createFunction("");
getBBAt(Module, MCFN, BeginAddr, CallTargets, TailCallTargets);
return MCFN;
}
// MachO MCObjectDisassembler implementation.
MCMachOObjectDisassembler::MCMachOObjectDisassembler(
const MachOObjectFile &MOOF, const MCDisassembler &Dis,
const MCInstrAnalysis &MIA, uint64_t VMAddrSlide,
uint64_t HeaderLoadAddress)
: MCObjectDisassembler(MOOF, Dis, MIA), MOOF(MOOF),
VMAddrSlide(VMAddrSlide), HeaderLoadAddress(HeaderLoadAddress) {
for (const SectionRef &Section : MOOF.sections()) {
StringRef Name;
Section.getName(Name);
// FIXME: We should use the S_ section type instead of the name.
if (Name == "__mod_init_func") {
DEBUG(dbgs() << "Found __mod_init_func section!\n");
Section.getContents(ModInitContents);
} else if (Name == "__mod_exit_func") {
DEBUG(dbgs() << "Found __mod_exit_func section!\n");
Section.getContents(ModExitContents);
}
}
}
// FIXME: Only do the translations for addresses actually inside the object.
uint64_t MCMachOObjectDisassembler::getEffectiveLoadAddr(uint64_t Addr) {
return Addr + VMAddrSlide;
}
uint64_t
MCMachOObjectDisassembler::getOriginalLoadAddr(uint64_t EffectiveAddr) {
return EffectiveAddr - VMAddrSlide;
}
uint64_t MCMachOObjectDisassembler::getEntrypoint() {
uint64_t EntryFileOffset = 0;
// Look for LC_MAIN.
{
uint32_t LoadCommandCount = MOOF.getHeader().ncmds;
MachOObjectFile::LoadCommandInfo Load = MOOF.getFirstLoadCommandInfo();
for (unsigned I = 0;; ++I) {
if (Load.C.cmd == MachO::LC_MAIN) {
EntryFileOffset =
((const MachO::entry_point_command *)Load.Ptr)->entryoff;
break;
}
if (I == LoadCommandCount - 1)
break;
else
Load = MOOF.getNextLoadCommandInfo(Load);
}
}
// If we didn't find anything, default to the common implementation.
// FIXME: Maybe we could also look at LC_UNIXTHREAD and friends?
if (EntryFileOffset)
return MCObjectDisassembler::getEntrypoint();
return EntryFileOffset + HeaderLoadAddress;
}
ArrayRef<uint64_t> MCMachOObjectDisassembler::getStaticInitFunctions() {
// FIXME: We only handle 64bit mach-o
assert(MOOF.is64Bit());
size_t EntrySize = 8;
size_t EntryCount = ModInitContents.size() / EntrySize;
return makeArrayRef(
reinterpret_cast<const uint64_t *>(ModInitContents.data()), EntryCount);
}
ArrayRef<uint64_t> MCMachOObjectDisassembler::getStaticExitFunctions() {
// FIXME: We only handle 64bit mach-o
assert(MOOF.is64Bit());
size_t EntrySize = 8;
size_t EntryCount = ModExitContents.size() / EntrySize;
return makeArrayRef(
reinterpret_cast<const uint64_t *>(ModExitContents.data()), EntryCount);
}
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