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BinaryFunction.cpp
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//===- bolt/Core/BinaryFunction.cpp - Low-level function ------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the BinaryFunction class.
//
//===----------------------------------------------------------------------===//
#include "bolt/Core/BinaryFunction.h"
#include "bolt/Core/BinaryBasicBlock.h"
#include "bolt/Core/DynoStats.h"
#include "bolt/Core/HashUtilities.h"
#include "bolt/Core/MCPlusBuilder.h"
#include "bolt/Utils/NameResolver.h"
#include "bolt/Utils/NameShortener.h"
#include "bolt/Utils/Utils.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Demangle/Demangle.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDisassembler/MCDisassembler.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstPrinter.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GenericDomTreeConstruction.h"
#include "llvm/Support/GenericLoopInfoImpl.h"
#include "llvm/Support/GraphWriter.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/Regex.h"
#include "llvm/Support/Timer.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/xxhash.h"
#include <functional>
#include <limits>
#include <numeric>
#include <stack>
#include <string>
#define DEBUG_TYPE "bolt"
using namespace llvm;
using namespace bolt;
namespace opts {
extern cl::OptionCategory BoltCategory;
extern cl::OptionCategory BoltOptCategory;
extern cl::opt<bool> EnableBAT;
extern cl::opt<bool> Instrument;
extern cl::opt<bool> StrictMode;
extern cl::opt<bool> UpdateDebugSections;
extern cl::opt<unsigned> Verbosity;
extern bool processAllFunctions();
cl::opt<bool> CheckEncoding(
"check-encoding",
cl::desc("perform verification of LLVM instruction encoding/decoding. "
"Every instruction in the input is decoded and re-encoded. "
"If the resulting bytes do not match the input, a warning message "
"is printed."),
cl::Hidden, cl::cat(BoltCategory));
static cl::opt<bool> DotToolTipCode(
"dot-tooltip-code",
cl::desc("add basic block instructions as tool tips on nodes"), cl::Hidden,
cl::cat(BoltCategory));
cl::opt<JumpTableSupportLevel>
JumpTables("jump-tables",
cl::desc("jump tables support (default=basic)"),
cl::init(JTS_BASIC),
cl::values(
clEnumValN(JTS_NONE, "none",
"do not optimize functions with jump tables"),
clEnumValN(JTS_BASIC, "basic",
"optimize functions with jump tables"),
clEnumValN(JTS_MOVE, "move",
"move jump tables to a separate section"),
clEnumValN(JTS_SPLIT, "split",
"split jump tables section into hot and cold based on "
"function execution frequency"),
clEnumValN(JTS_AGGRESSIVE, "aggressive",
"aggressively split jump tables section based on usage "
"of the tables")),
cl::ZeroOrMore,
cl::cat(BoltOptCategory));
static cl::opt<bool> NoScan(
"no-scan",
cl::desc(
"do not scan cold functions for external references (may result in "
"slower binary)"),
cl::Hidden, cl::cat(BoltOptCategory));
cl::opt<bool>
PreserveBlocksAlignment("preserve-blocks-alignment",
cl::desc("try to preserve basic block alignment"),
cl::cat(BoltOptCategory));
static cl::opt<bool> PrintOutputAddressRange(
"print-output-address-range",
cl::desc(
"print output address range for each basic block in the function when"
"BinaryFunction::print is called"),
cl::Hidden, cl::cat(BoltOptCategory));
cl::opt<bool>
PrintDynoStats("dyno-stats",
cl::desc("print execution info based on profile"),
cl::cat(BoltCategory));
static cl::opt<bool>
PrintDynoStatsOnly("print-dyno-stats-only",
cl::desc("while printing functions output dyno-stats and skip instructions"),
cl::init(false),
cl::Hidden,
cl::cat(BoltCategory));
static cl::list<std::string>
PrintOnly("print-only",
cl::CommaSeparated,
cl::desc("list of functions to print"),
cl::value_desc("func1,func2,func3,..."),
cl::Hidden,
cl::cat(BoltCategory));
cl::opt<bool>
TimeBuild("time-build",
cl::desc("print time spent constructing binary functions"),
cl::Hidden, cl::cat(BoltCategory));
cl::opt<bool>
TrapOnAVX512("trap-avx512",
cl::desc("in relocation mode trap upon entry to any function that uses "
"AVX-512 instructions"),
cl::init(false),
cl::ZeroOrMore,
cl::Hidden,
cl::cat(BoltCategory));
bool shouldPrint(const BinaryFunction &Function) {
if (Function.isIgnored())
return false;
if (PrintOnly.empty())
return true;
for (std::string &Name : opts::PrintOnly) {
if (Function.hasNameRegex(Name)) {
return true;
}
}
std::optional<StringRef> Origin = Function.getOriginSectionName();
if (Origin && llvm::any_of(opts::PrintOnly, [&](const std::string &Name) {
return Name == *Origin;
}))
return true;
return false;
}
} // namespace opts
namespace llvm {
namespace bolt {
template <typename R> static bool emptyRange(const R &Range) {
return Range.begin() == Range.end();
}
/// Gets debug line information for the instruction located at the given
/// address in the original binary. The SMLoc's pointer is used
/// to point to this information, which is represented by a
/// DebugLineTableRowRef. The returned pointer is null if no debug line
/// information for this instruction was found.
static SMLoc findDebugLineInformationForInstructionAt(
uint64_t Address, DWARFUnit *Unit,
const DWARFDebugLine::LineTable *LineTable) {
// We use the pointer in SMLoc to store an instance of DebugLineTableRowRef,
// which occupies 64 bits. Thus, we can only proceed if the struct fits into
// the pointer itself.
static_assert(
sizeof(decltype(SMLoc().getPointer())) >= sizeof(DebugLineTableRowRef),
"Cannot fit instruction debug line information into SMLoc's pointer");
SMLoc NullResult = DebugLineTableRowRef::NULL_ROW.toSMLoc();
uint32_t RowIndex = LineTable->lookupAddress(
{Address, object::SectionedAddress::UndefSection});
if (RowIndex == LineTable->UnknownRowIndex)
return NullResult;
assert(RowIndex < LineTable->Rows.size() &&
"Line Table lookup returned invalid index.");
decltype(SMLoc().getPointer()) Ptr;
DebugLineTableRowRef *InstructionLocation =
reinterpret_cast<DebugLineTableRowRef *>(&Ptr);
InstructionLocation->DwCompileUnitIndex = Unit->getOffset();
InstructionLocation->RowIndex = RowIndex + 1;
return SMLoc::getFromPointer(Ptr);
}
static std::string buildSectionName(StringRef Prefix, StringRef Name,
const BinaryContext &BC) {
if (BC.isELF())
return (Prefix + Name).str();
static NameShortener NS;
return (Prefix + Twine(NS.getID(Name))).str();
}
static raw_ostream &operator<<(raw_ostream &OS,
const BinaryFunction::State State) {
switch (State) {
case BinaryFunction::State::Empty: OS << "empty"; break;
case BinaryFunction::State::Disassembled: OS << "disassembled"; break;
case BinaryFunction::State::CFG: OS << "CFG constructed"; break;
case BinaryFunction::State::CFG_Finalized: OS << "CFG finalized"; break;
case BinaryFunction::State::EmittedCFG: OS << "emitted with CFG"; break;
case BinaryFunction::State::Emitted: OS << "emitted"; break;
}
return OS;
}
std::string BinaryFunction::buildCodeSectionName(StringRef Name,
const BinaryContext &BC) {
return buildSectionName(BC.isELF() ? ".local.text." : ".l.text.", Name, BC);
}
std::string BinaryFunction::buildColdCodeSectionName(StringRef Name,
const BinaryContext &BC) {
return buildSectionName(BC.isELF() ? ".local.cold.text." : ".l.c.text.", Name,
BC);
}
uint64_t BinaryFunction::Count = 0;
std::optional<StringRef>
BinaryFunction::hasNameRegex(const StringRef Name) const {
const std::string RegexName = (Twine("^") + StringRef(Name) + "$").str();
Regex MatchName(RegexName);
return forEachName(
[&MatchName](StringRef Name) { return MatchName.match(Name); });
}
std::optional<StringRef>
BinaryFunction::hasRestoredNameRegex(const StringRef Name) const {
const std::string RegexName = (Twine("^") + StringRef(Name) + "$").str();
Regex MatchName(RegexName);
return forEachName([&MatchName](StringRef Name) {
return MatchName.match(NameResolver::restore(Name));
});
}
std::string BinaryFunction::getDemangledName() const {
StringRef MangledName = NameResolver::restore(getOneName());
return demangle(MangledName.str());
}
BinaryBasicBlock *
BinaryFunction::getBasicBlockContainingOffset(uint64_t Offset) {
if (Offset > Size)
return nullptr;
if (BasicBlockOffsets.empty())
return nullptr;
/*
* This is commented out because it makes BOLT too slow.
* assert(std::is_sorted(BasicBlockOffsets.begin(),
* BasicBlockOffsets.end(),
* CompareBasicBlockOffsets())));
*/
auto I =
llvm::upper_bound(BasicBlockOffsets, BasicBlockOffset(Offset, nullptr),
CompareBasicBlockOffsets());
assert(I != BasicBlockOffsets.begin() && "first basic block not at offset 0");
--I;
BinaryBasicBlock *BB = I->second;
return (Offset < BB->getOffset() + BB->getOriginalSize()) ? BB : nullptr;
}
void BinaryFunction::markUnreachableBlocks() {
std::stack<BinaryBasicBlock *> Stack;
for (BinaryBasicBlock &BB : blocks())
BB.markValid(false);
// Add all entries and landing pads as roots.
for (BinaryBasicBlock *BB : BasicBlocks) {
if (isEntryPoint(*BB) || BB->isLandingPad()) {
Stack.push(BB);
BB->markValid(true);
continue;
}
// FIXME:
// Also mark BBs with indirect jumps as reachable, since we do not
// support removing unused jump tables yet (GH-issue20).
for (const MCInst &Inst : *BB) {
if (BC.MIB->getJumpTable(Inst)) {
Stack.push(BB);
BB->markValid(true);
break;
}
}
}
// Determine reachable BBs from the entry point
while (!Stack.empty()) {
BinaryBasicBlock *BB = Stack.top();
Stack.pop();
for (BinaryBasicBlock *Succ : BB->successors()) {
if (Succ->isValid())
continue;
Succ->markValid(true);
Stack.push(Succ);
}
}
}
// Any unnecessary fallthrough jumps revealed after calling eraseInvalidBBs
// will be cleaned up by fixBranches().
std::pair<unsigned, uint64_t>
BinaryFunction::eraseInvalidBBs(const MCCodeEmitter *Emitter) {
DenseSet<const BinaryBasicBlock *> InvalidBBs;
unsigned Count = 0;
uint64_t Bytes = 0;
for (BinaryBasicBlock *const BB : BasicBlocks) {
if (!BB->isValid()) {
assert(!isEntryPoint(*BB) && "all entry blocks must be valid");
InvalidBBs.insert(BB);
++Count;
Bytes += BC.computeCodeSize(BB->begin(), BB->end(), Emitter);
}
}
Layout.eraseBasicBlocks(InvalidBBs);
BasicBlockListType NewBasicBlocks;
for (auto I = BasicBlocks.begin(), E = BasicBlocks.end(); I != E; ++I) {
BinaryBasicBlock *BB = *I;
if (InvalidBBs.contains(BB)) {
// Make sure the block is removed from the list of predecessors.
BB->removeAllSuccessors();
DeletedBasicBlocks.push_back(BB);
} else {
NewBasicBlocks.push_back(BB);
}
}
BasicBlocks = std::move(NewBasicBlocks);
assert(BasicBlocks.size() == Layout.block_size());
// Update CFG state if needed
if (Count > 0)
recomputeLandingPads();
return std::make_pair(Count, Bytes);
}
bool BinaryFunction::isForwardCall(const MCSymbol *CalleeSymbol) const {
// This function should work properly before and after function reordering.
// In order to accomplish this, we use the function index (if it is valid).
// If the function indices are not valid, we fall back to the original
// addresses. This should be ok because the functions without valid indices
// should have been ordered with a stable sort.
const BinaryFunction *CalleeBF = BC.getFunctionForSymbol(CalleeSymbol);
if (CalleeBF) {
if (CalleeBF->isInjected())
return true;
return compareBinaryFunctionByIndex(this, CalleeBF);
} else {
// Absolute symbol.
ErrorOr<uint64_t> CalleeAddressOrError = BC.getSymbolValue(*CalleeSymbol);
assert(CalleeAddressOrError && "unregistered symbol found");
return *CalleeAddressOrError > getAddress();
}
}
void BinaryFunction::dump() const {
// getDynoStats calls FunctionLayout::updateLayoutIndices and
// BasicBlock::analyzeBranch. The former cannot be const, but should be
// removed, the latter should be made const, but seems to require refactoring.
// Forcing all callers to have a non-const reference to BinaryFunction to call
// dump non-const however is not ideal either. Adding this const_cast is right
// now the best solution. It is safe, because BinaryFunction itself is not
// modified. Only BinaryBasicBlocks are actually modified (if it all) and we
// have mutable pointers to those regardless whether this function is
// const-qualified or not.
const_cast<BinaryFunction &>(*this).print(dbgs(), "");
}
void BinaryFunction::print(raw_ostream &OS, std::string Annotation) {
if (!opts::shouldPrint(*this))
return;
StringRef SectionName =
OriginSection ? OriginSection->getName() : "<no origin section>";
OS << "Binary Function \"" << *this << "\" " << Annotation << " {";
std::vector<StringRef> AllNames = getNames();
if (AllNames.size() > 1) {
OS << "\n All names : ";
const char *Sep = "";
for (const StringRef &Name : AllNames) {
OS << Sep << Name;
Sep = "\n ";
}
}
OS << "\n Number : " << FunctionNumber;
OS << "\n State : " << CurrentState;
OS << "\n Address : 0x" << Twine::utohexstr(Address);
OS << "\n Size : 0x" << Twine::utohexstr(Size);
OS << "\n MaxSize : 0x" << Twine::utohexstr(MaxSize);
OS << "\n Offset : 0x" << Twine::utohexstr(getFileOffset());
OS << "\n Section : " << SectionName;
OS << "\n Orc Section : " << getCodeSectionName();
OS << "\n LSDA : 0x" << Twine::utohexstr(getLSDAAddress());
OS << "\n IsSimple : " << IsSimple;
OS << "\n IsMultiEntry: " << isMultiEntry();
OS << "\n IsSplit : " << isSplit();
OS << "\n BB Count : " << size();
if (HasUnknownControlFlow)
OS << "\n Unknown CF : true";
if (getPersonalityFunction())
OS << "\n Personality : " << getPersonalityFunction()->getName();
if (IsFragment)
OS << "\n IsFragment : true";
if (isFolded())
OS << "\n FoldedInto : " << *getFoldedIntoFunction();
for (BinaryFunction *ParentFragment : ParentFragments)
OS << "\n Parent : " << *ParentFragment;
if (!Fragments.empty()) {
OS << "\n Fragments : ";
ListSeparator LS;
for (BinaryFunction *Frag : Fragments)
OS << LS << *Frag;
}
if (hasCFG())
OS << "\n Hash : " << Twine::utohexstr(computeHash());
if (isMultiEntry()) {
OS << "\n Secondary Entry Points : ";
ListSeparator LS;
for (const auto &KV : SecondaryEntryPoints)
OS << LS << KV.second->getName();
}
if (FrameInstructions.size())
OS << "\n CFI Instrs : " << FrameInstructions.size();
if (!Layout.block_empty()) {
OS << "\n BB Layout : ";
ListSeparator LS;
for (const BinaryBasicBlock *BB : Layout.blocks())
OS << LS << BB->getName();
}
if (getImageAddress())
OS << "\n Image : 0x" << Twine::utohexstr(getImageAddress());
if (ExecutionCount != COUNT_NO_PROFILE) {
OS << "\n Exec Count : " << ExecutionCount;
OS << "\n Branch Count: " << RawBranchCount;
OS << "\n Profile Acc : " << format("%.1f%%", ProfileMatchRatio * 100.0f);
}
if (opts::PrintDynoStats && !getLayout().block_empty()) {
OS << '\n';
DynoStats dynoStats = getDynoStats(*this);
OS << dynoStats;
}
OS << "\n}\n";
if (opts::PrintDynoStatsOnly || !BC.InstPrinter)
return;
// Offset of the instruction in function.
uint64_t Offset = 0;
if (BasicBlocks.empty() && !Instructions.empty()) {
// Print before CFG was built.
for (const std::pair<const uint32_t, MCInst> &II : Instructions) {
Offset = II.first;
// Print label if exists at this offset.
auto LI = Labels.find(Offset);
if (LI != Labels.end()) {
if (const MCSymbol *EntrySymbol =
getSecondaryEntryPointSymbol(LI->second))
OS << EntrySymbol->getName() << " (Entry Point):\n";
OS << LI->second->getName() << ":\n";
}
BC.printInstruction(OS, II.second, Offset, this);
}
}
StringRef SplitPointMsg = "";
for (const FunctionFragment &FF : Layout.fragments()) {
OS << SplitPointMsg;
SplitPointMsg = "------- HOT-COLD SPLIT POINT -------\n\n";
for (const BinaryBasicBlock *BB : FF) {
OS << BB->getName() << " (" << BB->size()
<< " instructions, align : " << BB->getAlignment() << ")\n";
if (opts::PrintOutputAddressRange)
OS << formatv(" Output Address Range: [{0:x}, {1:x}) ({2} bytes)\n",
BB->getOutputAddressRange().first,
BB->getOutputAddressRange().second, BB->getOutputSize());
if (isEntryPoint(*BB)) {
if (MCSymbol *EntrySymbol = getSecondaryEntryPointSymbol(*BB))
OS << " Secondary Entry Point: " << EntrySymbol->getName() << '\n';
else
OS << " Entry Point\n";
}
if (BB->isLandingPad())
OS << " Landing Pad\n";
uint64_t BBExecCount = BB->getExecutionCount();
if (hasValidProfile()) {
OS << " Exec Count : ";
if (BB->getExecutionCount() != BinaryBasicBlock::COUNT_NO_PROFILE)
OS << BBExecCount << '\n';
else
OS << "<unknown>\n";
}
if (hasCFI())
OS << " CFI State : " << BB->getCFIState() << '\n';
if (opts::EnableBAT) {
OS << " Input offset: 0x" << Twine::utohexstr(BB->getInputOffset())
<< "\n";
}
if (!BB->pred_empty()) {
OS << " Predecessors: ";
ListSeparator LS;
for (BinaryBasicBlock *Pred : BB->predecessors())
OS << LS << Pred->getName();
OS << '\n';
}
if (!BB->throw_empty()) {
OS << " Throwers: ";
ListSeparator LS;
for (BinaryBasicBlock *Throw : BB->throwers())
OS << LS << Throw->getName();
OS << '\n';
}
Offset = alignTo(Offset, BB->getAlignment());
// Note: offsets are imprecise since this is happening prior to
// relaxation.
Offset = BC.printInstructions(OS, BB->begin(), BB->end(), Offset, this);
if (!BB->succ_empty()) {
OS << " Successors: ";
// For more than 2 successors, sort them based on frequency.
std::vector<uint64_t> Indices(BB->succ_size());
std::iota(Indices.begin(), Indices.end(), 0);
if (BB->succ_size() > 2 && BB->getKnownExecutionCount()) {
llvm::stable_sort(Indices, [&](const uint64_t A, const uint64_t B) {
return BB->BranchInfo[B] < BB->BranchInfo[A];
});
}
ListSeparator LS;
for (unsigned I = 0; I < Indices.size(); ++I) {
BinaryBasicBlock *Succ = BB->Successors[Indices[I]];
const BinaryBasicBlock::BinaryBranchInfo &BI =
BB->BranchInfo[Indices[I]];
OS << LS << Succ->getName();
if (ExecutionCount != COUNT_NO_PROFILE &&
BI.MispredictedCount != BinaryBasicBlock::COUNT_INFERRED) {
OS << " (mispreds: " << BI.MispredictedCount
<< ", count: " << BI.Count << ")";
} else if (ExecutionCount != COUNT_NO_PROFILE &&
BI.Count != BinaryBasicBlock::COUNT_NO_PROFILE) {
OS << " (inferred count: " << BI.Count << ")";
}
}
OS << '\n';
}
if (!BB->lp_empty()) {
OS << " Landing Pads: ";
ListSeparator LS;
for (BinaryBasicBlock *LP : BB->landing_pads()) {
OS << LS << LP->getName();
if (ExecutionCount != COUNT_NO_PROFILE) {
OS << " (count: " << LP->getExecutionCount() << ")";
}
}
OS << '\n';
}
// In CFG_Finalized state we can miscalculate CFI state at exit.
if (CurrentState == State::CFG && hasCFI()) {
const int32_t CFIStateAtExit = BB->getCFIStateAtExit();
if (CFIStateAtExit >= 0)
OS << " CFI State: " << CFIStateAtExit << '\n';
}
OS << '\n';
}
}
// Dump new exception ranges for the function.
if (!CallSites.empty()) {
OS << "EH table:\n";
for (const FunctionFragment &FF : getLayout().fragments()) {
for (const auto &FCSI : getCallSites(FF.getFragmentNum())) {
const CallSite &CSI = FCSI.second;
OS << " [" << *CSI.Start << ", " << *CSI.End << ") landing pad : ";
if (CSI.LP)
OS << *CSI.LP;
else
OS << "0";
OS << ", action : " << CSI.Action << '\n';
}
}
OS << '\n';
}
// Print all jump tables.
for (const std::pair<const uint64_t, JumpTable *> &JTI : JumpTables)
JTI.second->print(OS);
OS << "DWARF CFI Instructions:\n";
if (OffsetToCFI.size()) {
// Pre-buildCFG information
for (const std::pair<const uint32_t, uint32_t> &Elmt : OffsetToCFI) {
OS << format(" %08x:\t", Elmt.first);
assert(Elmt.second < FrameInstructions.size() && "Incorrect CFI offset");
BinaryContext::printCFI(OS, FrameInstructions[Elmt.second]);
OS << "\n";
}
} else {
// Post-buildCFG information
for (uint32_t I = 0, E = FrameInstructions.size(); I != E; ++I) {
const MCCFIInstruction &CFI = FrameInstructions[I];
OS << format(" %d:\t", I);
BinaryContext::printCFI(OS, CFI);
OS << "\n";
}
}
if (FrameInstructions.empty())
OS << " <empty>\n";
OS << "End of Function \"" << *this << "\"\n\n";
}
void BinaryFunction::printRelocations(raw_ostream &OS, uint64_t Offset,
uint64_t Size) const {
const char *Sep = " # Relocs: ";
auto RI = Relocations.lower_bound(Offset);
while (RI != Relocations.end() && RI->first < Offset + Size) {
OS << Sep << "(R: " << RI->second << ")";
Sep = ", ";
++RI;
}
}
static std::string mutateDWARFExpressionTargetReg(const MCCFIInstruction &Instr,
MCPhysReg NewReg) {
StringRef ExprBytes = Instr.getValues();
assert(ExprBytes.size() > 1 && "DWARF expression CFI is too short");
uint8_t Opcode = ExprBytes[0];
assert((Opcode == dwarf::DW_CFA_expression ||
Opcode == dwarf::DW_CFA_val_expression) &&
"invalid DWARF expression CFI");
(void)Opcode;
const uint8_t *const Start =
reinterpret_cast<const uint8_t *>(ExprBytes.drop_front(1).data());
const uint8_t *const End =
reinterpret_cast<const uint8_t *>(Start + ExprBytes.size() - 1);
unsigned Size = 0;
decodeULEB128(Start, &Size, End);
assert(Size > 0 && "Invalid reg encoding for DWARF expression CFI");
SmallString<8> Tmp;
raw_svector_ostream OSE(Tmp);
encodeULEB128(NewReg, OSE);
return Twine(ExprBytes.slice(0, 1))
.concat(OSE.str())
.concat(ExprBytes.drop_front(1 + Size))
.str();
}
void BinaryFunction::mutateCFIRegisterFor(const MCInst &Instr,
MCPhysReg NewReg) {
const MCCFIInstruction *OldCFI = getCFIFor(Instr);
assert(OldCFI && "invalid CFI instr");
switch (OldCFI->getOperation()) {
default:
llvm_unreachable("Unexpected instruction");
case MCCFIInstruction::OpDefCfa:
setCFIFor(Instr, MCCFIInstruction::cfiDefCfa(nullptr, NewReg,
OldCFI->getOffset()));
break;
case MCCFIInstruction::OpDefCfaRegister:
setCFIFor(Instr, MCCFIInstruction::createDefCfaRegister(nullptr, NewReg));
break;
case MCCFIInstruction::OpOffset:
setCFIFor(Instr, MCCFIInstruction::createOffset(nullptr, NewReg,
OldCFI->getOffset()));
break;
case MCCFIInstruction::OpRegister:
setCFIFor(Instr, MCCFIInstruction::createRegister(nullptr, NewReg,
OldCFI->getRegister2()));
break;
case MCCFIInstruction::OpSameValue:
setCFIFor(Instr, MCCFIInstruction::createSameValue(nullptr, NewReg));
break;
case MCCFIInstruction::OpEscape:
setCFIFor(Instr,
MCCFIInstruction::createEscape(
nullptr,
StringRef(mutateDWARFExpressionTargetReg(*OldCFI, NewReg))));
break;
case MCCFIInstruction::OpRestore:
setCFIFor(Instr, MCCFIInstruction::createRestore(nullptr, NewReg));
break;
case MCCFIInstruction::OpUndefined:
setCFIFor(Instr, MCCFIInstruction::createUndefined(nullptr, NewReg));
break;
}
}
const MCCFIInstruction *BinaryFunction::mutateCFIOffsetFor(const MCInst &Instr,
int64_t NewOffset) {
const MCCFIInstruction *OldCFI = getCFIFor(Instr);
assert(OldCFI && "invalid CFI instr");
switch (OldCFI->getOperation()) {
default:
llvm_unreachable("Unexpected instruction");
case MCCFIInstruction::OpDefCfaOffset:
setCFIFor(Instr, MCCFIInstruction::cfiDefCfaOffset(nullptr, NewOffset));
break;
case MCCFIInstruction::OpAdjustCfaOffset:
setCFIFor(Instr,
MCCFIInstruction::createAdjustCfaOffset(nullptr, NewOffset));
break;
case MCCFIInstruction::OpDefCfa:
setCFIFor(Instr, MCCFIInstruction::cfiDefCfa(nullptr, OldCFI->getRegister(),
NewOffset));
break;
case MCCFIInstruction::OpOffset:
setCFIFor(Instr, MCCFIInstruction::createOffset(
nullptr, OldCFI->getRegister(), NewOffset));
break;
}
return getCFIFor(Instr);
}
IndirectBranchType
BinaryFunction::processIndirectBranch(MCInst &Instruction, unsigned Size,
uint64_t Offset,
uint64_t &TargetAddress) {
const unsigned PtrSize = BC.AsmInfo->getCodePointerSize();
// The instruction referencing memory used by the branch instruction.
// It could be the branch instruction itself or one of the instructions
// setting the value of the register used by the branch.
MCInst *MemLocInstr;
// The instruction loading the fixed PIC jump table entry value.
MCInst *FixedEntryLoadInstr;
// Address of the table referenced by MemLocInstr. Could be either an
// array of function pointers, or a jump table.
uint64_t ArrayStart = 0;
unsigned BaseRegNum, IndexRegNum;
int64_t DispValue;
const MCExpr *DispExpr;
// In AArch, identify the instruction adding the PC-relative offset to
// jump table entries to correctly decode it.
MCInst *PCRelBaseInstr;
uint64_t PCRelAddr = 0;
auto Begin = Instructions.begin();
if (BC.isAArch64()) {
PreserveNops = BC.HasRelocations;
// Start at the last label as an approximation of the current basic block.
// This is a heuristic, since the full set of labels have yet to be
// determined
for (const uint32_t Offset :
llvm::make_first_range(llvm::reverse(Labels))) {
auto II = Instructions.find(Offset);
if (II != Instructions.end()) {
Begin = II;
break;
}
}
}
IndirectBranchType BranchType = BC.MIB->analyzeIndirectBranch(
Instruction, Begin, Instructions.end(), PtrSize, MemLocInstr, BaseRegNum,
IndexRegNum, DispValue, DispExpr, PCRelBaseInstr, FixedEntryLoadInstr);
if (BranchType == IndirectBranchType::UNKNOWN && !MemLocInstr)
return BranchType;
if (MemLocInstr != &Instruction)
IndexRegNum = BC.MIB->getNoRegister();
if (BC.isAArch64()) {
const MCSymbol *Sym = BC.MIB->getTargetSymbol(*PCRelBaseInstr, 1);
assert(Sym && "Symbol extraction failed");
ErrorOr<uint64_t> SymValueOrError = BC.getSymbolValue(*Sym);
if (SymValueOrError) {
PCRelAddr = *SymValueOrError;
} else {
for (std::pair<const uint32_t, MCSymbol *> &Elmt : Labels) {
if (Elmt.second == Sym) {
PCRelAddr = Elmt.first + getAddress();
break;
}
}
}
uint64_t InstrAddr = 0;
for (auto II = Instructions.rbegin(); II != Instructions.rend(); ++II) {
if (&II->second == PCRelBaseInstr) {
InstrAddr = II->first + getAddress();
break;
}
}
assert(InstrAddr != 0 && "instruction not found");
// We do this to avoid spurious references to code locations outside this
// function (for example, if the indirect jump lives in the last basic
// block of the function, it will create a reference to the next function).
// This replaces a symbol reference with an immediate.
BC.MIB->replaceMemOperandDisp(*PCRelBaseInstr,
MCOperand::createImm(PCRelAddr - InstrAddr));
// FIXME: Disable full jump table processing for AArch64 until we have a
// proper way of determining the jump table limits.
return IndirectBranchType::UNKNOWN;
}
auto getExprValue = [&](const MCExpr *Expr) {
const MCSymbol *TargetSym;
uint64_t TargetOffset;
std::tie(TargetSym, TargetOffset) = BC.MIB->getTargetSymbolInfo(Expr);
ErrorOr<uint64_t> SymValueOrError = BC.getSymbolValue(*TargetSym);
assert(SymValueOrError && "Global symbol needs a value");
return *SymValueOrError + TargetOffset;
};
// RIP-relative addressing should be converted to symbol form by now
// in processed instructions (but not in jump).
if (DispExpr) {
ArrayStart = getExprValue(DispExpr);
BaseRegNum = BC.MIB->getNoRegister();
if (BC.isAArch64()) {
ArrayStart &= ~0xFFFULL;
ArrayStart += DispValue & 0xFFFULL;
}
} else {
ArrayStart = static_cast<uint64_t>(DispValue);
}
if (BaseRegNum == BC.MRI->getProgramCounter())
ArrayStart += getAddress() + Offset + Size;
if (FixedEntryLoadInstr) {
assert(BranchType == IndirectBranchType::POSSIBLE_PIC_FIXED_BRANCH &&
"Invalid IndirectBranch type");
MCInst::iterator FixedEntryDispOperand =
BC.MIB->getMemOperandDisp(*FixedEntryLoadInstr);
assert(FixedEntryDispOperand != FixedEntryLoadInstr->end() &&
"Invalid memory instruction");
const MCExpr *FixedEntryDispExpr = FixedEntryDispOperand->getExpr();
const uint64_t EntryAddress = getExprValue(FixedEntryDispExpr);
uint64_t EntrySize = BC.getJumpTableEntrySize(JumpTable::JTT_PIC);
ErrorOr<int64_t> Value =
BC.getSignedValueAtAddress(EntryAddress, EntrySize);
if (!Value)
return IndirectBranchType::UNKNOWN;
BC.outs() << "BOLT-INFO: fixed PIC indirect branch detected in " << *this
<< " at 0x" << Twine::utohexstr(getAddress() + Offset)
<< " referencing data at 0x" << Twine::utohexstr(EntryAddress)
<< " the destination value is 0x"
<< Twine::utohexstr(ArrayStart + *Value) << '\n';
TargetAddress = ArrayStart + *Value;
// Remove spurious JumpTable at EntryAddress caused by PIC reference from
// the load instruction.
BC.deleteJumpTable(EntryAddress);
// Replace FixedEntryDispExpr used in target address calculation with outer
// jump table reference.
JumpTable *JT = BC.getJumpTableContainingAddress(ArrayStart);
assert(JT && "Must have a containing jump table for PIC fixed branch");
BC.MIB->replaceMemOperandDisp(*FixedEntryLoadInstr, JT->getFirstLabel(),
EntryAddress - ArrayStart, &*BC.Ctx);
return BranchType;
}
LLVM_DEBUG(dbgs() << "BOLT-DEBUG: addressed memory is 0x"
<< Twine::utohexstr(ArrayStart) << '\n');
ErrorOr<BinarySection &> Section = BC.getSectionForAddress(ArrayStart);
if (!Section) {
// No section - possibly an absolute address. Since we don't allow
// internal function addresses to escape the function scope - we
// consider it a tail call.
if (opts::Verbosity >= 1) {
BC.errs() << "BOLT-WARNING: no section for address 0x"
<< Twine::utohexstr(ArrayStart) << " referenced from function "
<< *this << '\n';
}
return IndirectBranchType::POSSIBLE_TAIL_CALL;
}
if (Section->isVirtual()) {
// The contents are filled at runtime.
return IndirectBranchType::POSSIBLE_TAIL_CALL;
}
if (BranchType == IndirectBranchType::POSSIBLE_FIXED_BRANCH) {
ErrorOr<uint64_t> Value = BC.getPointerAtAddress(ArrayStart);
if (!Value)
return IndirectBranchType::UNKNOWN;
if (BC.getSectionForAddress(ArrayStart)->isWritable())
return IndirectBranchType::UNKNOWN;
BC.outs() << "BOLT-INFO: fixed indirect branch detected in " << *this
<< " at 0x" << Twine::utohexstr(getAddress() + Offset)
<< " referencing data at 0x" << Twine::utohexstr(ArrayStart)
<< " the destination value is 0x" << Twine::utohexstr(*Value)
<< '\n';
TargetAddress = *Value;
return BranchType;
}
// Check if there's already a jump table registered at this address.
MemoryContentsType MemType;
if (JumpTable *JT = BC.getJumpTableContainingAddress(ArrayStart)) {
switch (JT->Type) {
case JumpTable::JTT_NORMAL:
MemType = MemoryContentsType::POSSIBLE_JUMP_TABLE;
break;
case JumpTable::JTT_PIC:
MemType = MemoryContentsType::POSSIBLE_PIC_JUMP_TABLE;
break;
}
} else {
MemType = BC.analyzeMemoryAt(ArrayStart, *this);
}
// Check that jump table type in instruction pattern matches memory contents.
JumpTable::JumpTableType JTType;
if (BranchType == IndirectBranchType::POSSIBLE_PIC_JUMP_TABLE) {
if (MemType != MemoryContentsType::POSSIBLE_PIC_JUMP_TABLE)
return IndirectBranchType::UNKNOWN;
JTType = JumpTable::JTT_PIC;
} else {
if (MemType == MemoryContentsType::POSSIBLE_PIC_JUMP_TABLE)
return IndirectBranchType::UNKNOWN;
if (MemType == MemoryContentsType::UNKNOWN)
return IndirectBranchType::POSSIBLE_TAIL_CALL;
BranchType = IndirectBranchType::POSSIBLE_JUMP_TABLE;
JTType = JumpTable::JTT_NORMAL;
}
// Convert the instruction into jump table branch.
const MCSymbol *JTLabel = BC.getOrCreateJumpTable(*this, ArrayStart, JTType);
BC.MIB->replaceMemOperandDisp(*MemLocInstr, JTLabel, BC.Ctx.get());
BC.MIB->setJumpTable(Instruction, ArrayStart, IndexRegNum);
JTSites.emplace_back(Offset, ArrayStart);
return BranchType;
}
MCSymbol *BinaryFunction::getOrCreateLocalLabel(uint64_t Address,
bool CreatePastEnd) {
const uint64_t Offset = Address - getAddress();