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156a55209c9bd421a6c75652c8139f042516a1e6
llvm/bolt/RewriteInstance.cpp
Theodoros Kasampalis 156a55209c Simplification of loads from read-only data sections. 
Summary:
Instructions that load data from the a read-only data section and their
target address can be computed statically (e.g. RIP-relative addressing)
are modified to corresponding instructions that use immediate operands.
We apply the transformation only when the resulting instruction will have
smaller or equal size.

(cherry picked from FBD3397112)
2016-06-03 00:58:11 -07:00

2023 lines
71 KiB
C++
Raw Blame History

//===--- RewriteInstance.cpp - Interface for machine-level function -------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//===----------------------------------------------------------------------===//
#include "BinaryBasicBlock.h"
#include "BinaryContext.h"
#include "BinaryFunction.h"
#include "BinaryPassManager.h"
#include "DataReader.h"
#include "Exceptions.h"
#include "RewriteInstance.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/DebugInfo/DWARF/DWARFContext.h"
#include "llvm/DebugInfo/DWARF/DWARFDebugLine.h"
#include "llvm/ExecutionEngine/Orc/LambdaResolver.h"
#include "llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h"
#include "llvm/ExecutionEngine/RTDyldMemoryManager.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAsmLayout.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDisassembler.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCInstPrinter.h"
#include "llvm/MC/MCInstrAnalysis.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCObjectStreamer.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Errc.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/Target/TargetMachine.h"
#include <algorithm>
#include <fstream>
#include <stack>
#include <system_error>
#undef DEBUG_TYPE
#define DEBUG_TYPE "bolt"
using namespace llvm;
using namespace object;
using namespace bolt;
namespace opts {
static cl::opt<std::string>
OutputFilename("o", cl::desc("<output file>"), cl::Required);
static cl::list<std::string>
BreakFunctionNames("break-funcs",
cl::CommaSeparated,
cl::desc("list of functions to core dump on (debugging)"),
cl::value_desc("func1,func2,func3,..."),
cl::Hidden);
static cl::list<std::string>
FunctionNames("funcs",
cl::CommaSeparated,
cl::desc("list of functions to optimize"),
cl::value_desc("func1,func2,func3,..."));
static cl::opt<std::string>
FunctionNamesFile("funcs-file",
cl::desc("file with list of functions to optimize"));
static cl::list<std::string>
SkipFunctionNames("skip-funcs",
cl::CommaSeparated,
cl::desc("list of functions to skip"),
cl::value_desc("func1,func2,func3,..."));
static cl::opt<std::string>
SkipFunctionNamesFile("skip-funcs-file",
cl::desc("file with list of functions to skip"));
static cl::opt<unsigned>
MaxFunctions("max-funcs",
cl::desc("maximum # of functions to overwrite"),
cl::Optional);
cl::opt<BinaryFunction::SplittingType>
SplitFunctions("split-functions",
cl::desc("split functions into hot and cold regions"),
cl::init(BinaryFunction::ST_NONE),
cl::values(clEnumValN(BinaryFunction::ST_NONE, "0",
"do not split any function"),
clEnumValN(BinaryFunction::ST_EH, "1",
"split all landing pads"),
clEnumValN(BinaryFunction::ST_LARGE, "2",
"also split if function too large to fit"),
clEnumValN(BinaryFunction::ST_ALL, "3",
"split all functions"),
clEnumValEnd),
cl::Optional);
static cl::opt<bool>
UpdateDebugSections("update-debug-sections",
cl::desc("update DWARF debug sections of the executable"),
cl::Optional);
static cl::opt<bool>
FixDebugInfoLargeFunctions("fix-debuginfo-large-functions",
cl::init(true),
cl::desc("do another pass if we encounter large "
"functions, to correct their debug info."),
cl::Optional,
cl::ReallyHidden);
static cl::opt<bool>
AlignBlocks("align-blocks",
cl::desc("try to align BBs inserting nops"),
cl::Optional);
static cl::opt<bool>
UseGnuStack("use-gnu-stack",
cl::desc("use GNU_STACK program header for new segment"));
static cl::opt<bool>
DumpEHFrame("dump-eh-frame", cl::desc("dump parsed .eh_frame (debugging)"),
cl::Hidden);
cl::opt<bool>
PrintAll("print-all", cl::desc("print functions after each stage"),
cl::Hidden);
cl::opt<bool>
DumpDotAll("dump-dot-all",
cl::desc("dump function CFGs to graphviz format after each stage"),
cl::Hidden);
static cl::opt<bool>
PrintCFG("print-cfg", cl::desc("print functions after CFG construction"),
cl::Hidden);
static cl::opt<bool>
PrintLoopInfo("print-loops", cl::desc("print loop related information"),
cl::Hidden);
cl::opt<bool>
PrintUCE("print-uce",
cl::desc("print functions after unreachable code elimination"),
cl::Hidden);
cl::opt<bool>
PrintPeepholes("print-peepholes",
cl::desc("print functions after peephole optimization"),
cl::Hidden);
static cl::opt<bool>
PrintDisasm("print-disasm", cl::desc("print function after disassembly"),
cl::Hidden);
cl::opt<bool>
PrintEHRanges("print-eh-ranges",
cl::desc("print function with updated exception ranges"),
cl::Hidden);
cl::opt<bool>
PrintSimplifyROLoads("print-simplify-rodata-loads",
cl::desc("print functions after simplification of RO data"
" loads"),
cl::Hidden);
cl::opt<bool>
PrintReordered("print-reordered",
cl::desc("print functions after layout optimization"),
cl::Hidden);
static cl::opt<bool>
KeepTmp("keep-tmp",
cl::desc("preserve intermediate .o file"),
cl::Hidden);
cl::opt<bool>
AllowStripped("allow-stripped",
cl::desc("allow processing of stripped binaries"),
cl::Hidden);
// Check against lists of functions from options if we should
// optimize the function with a given name.
bool shouldProcess(const BinaryFunction &Function) {
if (opts::MaxFunctions && Function.getFunctionNumber() > opts::MaxFunctions)
return false;
auto populateFunctionNames = [](cl::opt<std::string> &FunctionNamesFile,
cl::list<std::string> &FunctionNames) {
assert(!FunctionNamesFile.empty() && "unexpected empty file name");
std::ifstream FuncsFile(FunctionNamesFile, std::ios::in);
std::string FuncName;
while (std::getline(FuncsFile, FuncName)) {
FunctionNames.push_back(FuncName);
}
FunctionNamesFile = "";
};
if (!FunctionNamesFile.empty())
populateFunctionNames(FunctionNamesFile, FunctionNames);
if (!SkipFunctionNamesFile.empty())
populateFunctionNames(SkipFunctionNamesFile, SkipFunctionNames);
bool IsValid = true;
if (!FunctionNames.empty()) {
IsValid = false;
for (auto &Name : FunctionNames) {
if (Function.hasName(Name)) {
IsValid = true;
break;
}
}
}
if (!IsValid)
return false;
if (!SkipFunctionNames.empty()) {
for (auto &Name : SkipFunctionNames) {
if (Function.hasName(Name)) {
IsValid = false;
break;
}
}
}
return IsValid;
}
} // namespace opts
static void report_error(StringRef Message, std::error_code EC) {
assert(EC);
errs() << "BOLT-ERROR: '" << Message << "': " << EC.message() << ".\n";
exit(1);
}
static void check_error(std::error_code EC, StringRef Message) {
if (!EC)
return;
report_error(Message, EC);
}
uint8_t *ExecutableFileMemoryManager::allocateSection(intptr_t Size,
unsigned Alignment,
unsigned SectionID,
StringRef SectionName,
bool IsCode,
bool IsReadOnly) {
uint8_t *ret;
if (IsCode) {
ret = SectionMemoryManager::allocateCodeSection(Size, Alignment,
SectionID, SectionName);
} else {
ret = SectionMemoryManager::allocateDataSection(Size, Alignment,
SectionID, SectionName,
IsReadOnly);
}
DEBUG(dbgs() << "BOLT: allocating " << (IsCode ? "code" : "data")
<< " section : " << SectionName
<< " with size " << Size << ", alignment " << Alignment
<< " at 0x" << ret << "\n");
SectionMapInfo[SectionName] = SectionInfo(reinterpret_cast<uint64_t>(ret),
Size,
Alignment,
IsCode,
IsReadOnly,
0,
0,
SectionID);
return ret;
}
/// Notifier for non-allocatable (note) section.
uint8_t *ExecutableFileMemoryManager::recordNoteSection(
const uint8_t *Data,
uintptr_t Size,
unsigned Alignment,
unsigned SectionID,
StringRef SectionName) {
DEBUG(dbgs() << "BOLT: note section "
<< SectionName
<< " with size " << Size << ", alignment " << Alignment
<< " at 0x"
<< Twine::utohexstr(reinterpret_cast<uint64_t>(Data)) << '\n');
if (SectionName == ".debug_line") {
// We need to make a copy of the section contents if we'll need it for
// a future reference.
uint8_t *DataCopy = new uint8_t[Size];
memcpy(DataCopy, Data, Size);
NoteSectionInfo[SectionName] =
SectionInfo(reinterpret_cast<uint64_t>(DataCopy),
Size,
Alignment,
/*IsCode=*/false,
/*IsReadOnly*/true,
0,
0,
SectionID);
return DataCopy;
} else {
DEBUG(dbgs() << "BOLT-DEBUG: ignoring section " << SectionName
<< " in recordNoteSection()\n");
return nullptr;
}
}
bool ExecutableFileMemoryManager::finalizeMemory(std::string *ErrMsg) {
DEBUG(dbgs() << "BOLT: finalizeMemory()\n");
return SectionMemoryManager::finalizeMemory(ErrMsg);
}
ExecutableFileMemoryManager::~ExecutableFileMemoryManager() {
for (auto &SII : NoteSectionInfo) {
delete[] reinterpret_cast<uint8_t *>(SII.second.AllocAddress);
}
}
/// Create BinaryContext for a given architecture \p ArchName and
/// triple \p TripleName.
static std::unique_ptr<BinaryContext> CreateBinaryContext(
std::string ArchName,
std::string TripleName,
const DataReader &DR,
std::unique_ptr<DWARFContext> DwCtx) {
std::string Error;
std::unique_ptr<Triple> TheTriple = llvm::make_unique<Triple>(TripleName);
const Target *TheTarget = TargetRegistry::lookupTarget(ArchName,
*TheTriple,
Error);
if (!TheTarget) {
errs() << "BOLT: " << Error;
return nullptr;
}
std::unique_ptr<const MCRegisterInfo> MRI(
TheTarget->createMCRegInfo(TripleName));
if (!MRI) {
errs() << "error: no register info for target " << TripleName << "\n";
return nullptr;
}
// Set up disassembler.
std::unique_ptr<const MCAsmInfo> AsmInfo(
TheTarget->createMCAsmInfo(*MRI, TripleName));
if (!AsmInfo) {
errs() << "error: no assembly info for target " << TripleName << "\n";
return nullptr;
}
std::unique_ptr<const MCSubtargetInfo> STI(
TheTarget->createMCSubtargetInfo(TripleName, "", ""));
if (!STI) {
errs() << "error: no subtarget info for target " << TripleName << "\n";
return nullptr;
}
std::unique_ptr<const MCInstrInfo> MII(TheTarget->createMCInstrInfo());
if (!MII) {
errs() << "error: no instruction info for target " << TripleName << "\n";
return nullptr;
}
std::unique_ptr<MCObjectFileInfo> MOFI =
llvm::make_unique<MCObjectFileInfo>();
std::unique_ptr<MCContext> Ctx =
llvm::make_unique<MCContext>(AsmInfo.get(), MRI.get(), MOFI.get());
MOFI->InitMCObjectFileInfo(*TheTriple, Reloc::Default,
CodeModel::Default, *Ctx);
std::unique_ptr<MCDisassembler> DisAsm(
TheTarget->createMCDisassembler(*STI, *Ctx));
if (!DisAsm) {
errs() << "error: no disassembler for target " << TripleName << "\n";
return nullptr;
}
std::unique_ptr<const MCInstrAnalysis> MIA(
TheTarget->createMCInstrAnalysis(MII.get()));
if (!MIA) {
errs() << "error: failed to create instruction analysis for target"
<< TripleName << "\n";
return nullptr;
}
int AsmPrinterVariant = AsmInfo->getAssemblerDialect();
std::unique_ptr<MCInstPrinter> InstructionPrinter(
TheTarget->createMCInstPrinter(Triple(TripleName), AsmPrinterVariant,
*AsmInfo, *MII, *MRI));
if (!InstructionPrinter) {
errs() << "error: no instruction printer for target " << TripleName
<< '\n';
return nullptr;
}
InstructionPrinter->setPrintImmHex(true);
std::unique_ptr<MCCodeEmitter> MCE(
TheTarget->createMCCodeEmitter(*MII, *MRI, *Ctx));
// Make sure we don't miss any output on core dumps.
outs().SetUnbuffered();
errs().SetUnbuffered();
dbgs().SetUnbuffered();
auto BC =
llvm::make_unique<BinaryContext>(std::move(Ctx),
std::move(DwCtx),
std::move(TheTriple),
TheTarget,
TripleName,
std::move(MCE),
std::move(MOFI),
std::move(AsmInfo),
std::move(MII),
std::move(STI),
std::move(InstructionPrinter),
std::move(MIA),
std::move(MRI),
std::move(DisAsm),
DR);
return BC;
}
RewriteInstance::RewriteInstance(ELFObjectFileBase *File,
const DataReader &DR)
: InputFile(File),
BC(CreateBinaryContext("x86-64", "x86_64-unknown-linux", DR,
std::unique_ptr<DWARFContext>(new DWARFContextInMemory(*InputFile)))) {
}
RewriteInstance::~RewriteInstance() {}
void RewriteInstance::reset() {
BinaryFunctions.clear();
FileSymRefs.clear();
auto &DR = BC->DR;
BC = CreateBinaryContext("x86-64", "x86_64-unknown-linux", DR,
std::unique_ptr<DWARFContext>(new DWARFContextInMemory(*InputFile)));
CFIRdWrt.reset(nullptr);
SectionMM.reset(nullptr);
Out.reset(nullptr);
EHFrame = nullptr;
FailedAddresses.clear();
RangesSectionsWriter.reset();
TotalScore = 0;
}
void RewriteInstance::discoverStorage() {
auto ELF64LEFile = dyn_cast<ELF64LEObjectFile>(InputFile);
if (!ELF64LEFile) {
errs() << "BOLT-ERROR: only 64-bit LE ELF binaries are supported\n";
exit(1);
}
auto Obj = ELF64LEFile->getELFFile();
// This is where the first segment and ELF header were allocated.
uint64_t FirstAllocAddress = std::numeric_limits<uint64_t>::max();
NextAvailableAddress = 0;
uint64_t NextAvailableOffset = 0;
for (const auto &Phdr : Obj->program_headers()) {
if (Phdr.p_type == ELF::PT_LOAD) {
FirstAllocAddress = std::min(FirstAllocAddress,
static_cast<uint64_t>(Phdr.p_vaddr));
NextAvailableAddress = std::max(NextAvailableAddress,
Phdr.p_vaddr + Phdr.p_memsz);
NextAvailableOffset = std::max(NextAvailableOffset,
Phdr.p_offset + Phdr.p_filesz);
}
}
assert(NextAvailableAddress && NextAvailableOffset &&
"no PT_LOAD pheader seen");
errs() << "BOLT-INFO: first alloc address is 0x"
<< Twine::utohexstr(FirstAllocAddress) << '\n';
FirstNonAllocatableOffset = NextAvailableOffset;
NextAvailableAddress = RoundUpToAlignment(NextAvailableAddress, PageAlign);
NextAvailableOffset = RoundUpToAlignment(NextAvailableOffset, PageAlign);
if (!opts::UseGnuStack) {
// This is where the black magic happens. Creating PHDR table in a segment
// other than that containing ELF header is tricky. Some loaders and/or
// parts of loaders will apply e_phoff from ELF header assuming both are in
// the same segment, while others will do the proper calculation.
// We create the new PHDR table in such a way that both of the methods
// of loading and locating the table work. There's a slight file size
// overhead because of that.
//
// NB: bfd's strip command cannot do the above and will corrupt the
// binary during the process of stripping non-allocatable sections.
if (NextAvailableOffset <= NextAvailableAddress - FirstAllocAddress) {
NextAvailableOffset = NextAvailableAddress - FirstAllocAddress;
} else {
NextAvailableAddress = NextAvailableOffset + FirstAllocAddress;
}
assert(NextAvailableOffset == NextAvailableAddress - FirstAllocAddress &&
"PHDR table address calculation error");
errs() << "BOLT-INFO: creating new program header table at address 0x"
<< Twine::utohexstr(NextAvailableAddress) << ", offset 0x"
<< Twine::utohexstr(NextAvailableOffset) << '\n';
PHDRTableAddress = NextAvailableAddress;
PHDRTableOffset = NextAvailableOffset;
// Reserve space for 3 extra pheaders.
unsigned Phnum = Obj->getHeader()->e_phnum;
Phnum += 3;
NextAvailableAddress += Phnum * sizeof(ELFFile<ELF64LE>::Elf_Phdr);
NextAvailableOffset += Phnum * sizeof(ELFFile<ELF64LE>::Elf_Phdr);
}
// Align at cache line.
NextAvailableAddress = RoundUpToAlignment(NextAvailableAddress, 64);
NextAvailableOffset = RoundUpToAlignment(NextAvailableOffset, 64);
NewTextSegmentAddress = NextAvailableAddress;
NewTextSegmentOffset = NextAvailableOffset;
}
void RewriteInstance::run() {
if (!BC) {
errs() << "failed to create a binary context\n";
return;
}
unsigned PassNumber = 1;
// Main "loop".
discoverStorage();
readSpecialSections();
discoverFileObjects();
readDebugInfo();
disassembleFunctions();
readFunctionDebugInfo();
runOptimizationPasses();
emitFunctions();
if (opts::SplitFunctions == BinaryFunction::ST_LARGE &&
checkLargeFunctions()) {
++PassNumber;
// Emit again because now some functions have been split
outs() << "BOLT: split-functions: starting pass " << PassNumber << "...\n";
reset();
discoverStorage();
readSpecialSections();
discoverFileObjects();
readDebugInfo();
disassembleFunctions();
readFunctionDebugInfo();
runOptimizationPasses();
emitFunctions();
}
// Emit functions again ignoring functions which still didn't fit in their
// original space, so that we don't generate incorrect debugging information
// for them (information that would reflect the optimized version).
if (opts::UpdateDebugSections && opts::FixDebugInfoLargeFunctions &&
checkLargeFunctions()) {
++PassNumber;
outs() << "BOLT: starting pass (ignoring large functions) "
<< PassNumber << "...\n";
reset();
discoverStorage();
readSpecialSections();
discoverFileObjects();
readDebugInfo();
disassembleFunctions();
for (uint64_t Address : LargeFunctions) {
auto FunctionIt = BinaryFunctions.find(Address);
assert(FunctionIt != BinaryFunctions.end() &&
"Invalid large function address.");
errs() << "BOLT-WARNING: Function " << FunctionIt->second.getName()
<< " is larger than its orginal size: emitting again marking it "
<< "as not simple.\n";
FunctionIt->second.setSimple(false);
}
readFunctionDebugInfo();
runOptimizationPasses();
emitFunctions();
}
if (opts::UpdateDebugSections)
updateDebugInfo();
// Copy allocatable part of the input.
std::error_code EC;
Out = llvm::make_unique<tool_output_file>(opts::OutputFilename, EC,
sys::fs::F_None, 0777);
check_error(EC, "cannot create output executable file");
Out->os() << InputFile->getData().substr(0, FirstNonAllocatableOffset);
// Rewrite allocatable contents and copy non-allocatable parts with mods.
rewriteFile();
}
void RewriteInstance::discoverFileObjects() {
std::string FileSymbolName;
bool SeenFileName = false;
FileSymRefs.clear();
BinaryFunctions.clear();
BC->GlobalAddresses.clear();
// For local symbols we want to keep track of associated FILE symbol for
// disambiguation by name.
for (const SymbolRef &Symbol : InputFile->symbols()) {
// Keep undefined symbols for pretty printing?
if (Symbol.getFlags() & SymbolRef::SF_Undefined)
continue;
ErrorOr<StringRef> NameOrError = Symbol.getName();
check_error(NameOrError.getError(), "cannot get symbol name");
if (Symbol.getType() == SymbolRef::ST_File) {
// Could be used for local symbol disambiguation.
FileSymbolName = *NameOrError;
SeenFileName = true;
continue;
}
ErrorOr<uint64_t> AddressOrErr = Symbol.getAddress();
check_error(AddressOrErr.getError(), "cannot get symbol address");
uint64_t Address = *AddressOrErr;
if (Address == 0) {
if (Symbol.getType() == SymbolRef::ST_Function)
errs() << "BOLT-WARNING: function with 0 address seen\n";
continue;
}
FileSymRefs[Address] = Symbol;
// There's nothing horribly wrong with anonymous symbols, but let's
// ignore them for now.
if (NameOrError->empty())
continue;
/// It is possible we are seeing a globalized local. LLVM might treat it as
/// a local if it has a "private global" prefix, e.g. ".L". Thus we have to
/// change the prefix to enforce global scope of the symbol.
std::string Name =
NameOrError->startswith(BC->AsmInfo->getPrivateGlobalPrefix())
? "PG." + std::string(*NameOrError)
: std::string(*NameOrError);
// Disambiguate all local symbols before adding to symbol table.
// Since we don't know if we will see a global with the same name,
// always modify the local name.
//
// NOTE: the naming convention for local symbols should match
// the one we use for profile data.
std::string UniqueName;
std::string AlternativeName;
if (Symbol.getFlags() & SymbolRef::SF_Global) {
assert(BC->GlobalSymbols.find(Name) == BC->GlobalSymbols.end() &&
"global name not unique");
UniqueName = Name;
} else {
// If we have a local file name, we should create 2 variants for the
// function name. The reason is that perf profile might have been
// collected on a binary that did not have the local file name (e.g. as
// a side effect of stripping debug info from the binary):
//
// primary: <function>/<id>
// alternative: <function>/<file>/<id2>
//
// The <id> field is used for disambiguation of local symbols since there
// could be identical function names coming from identical file names
// (e.g. from different directories).
std::string Prefix = Name + "/";
std::string AltPrefix;
if (!FileSymbolName.empty())
AltPrefix = Prefix + FileSymbolName + "/";
auto uniquifyName = [&] (std::string NamePrefix) {
unsigned LocalID = 1;
while (BC->GlobalSymbols.find(NamePrefix + std::to_string(LocalID))
!= BC->GlobalSymbols.end())
++LocalID;
return NamePrefix + std::to_string(LocalID);
};
UniqueName = uniquifyName(Prefix);
if (!AltPrefix.empty())
AlternativeName = uniquifyName(AltPrefix);
}
BC->registerNameAtAddress(UniqueName, Address);
if (!AlternativeName.empty())
BC->registerNameAtAddress(AlternativeName, Address);
// Only consider ST_Function symbols for functions. Although this
// assumption could be broken by assembly functions for which the type
// could be wrong, we skip such entries till the support for
// assembly is implemented.
if (Symbol.getType() != SymbolRef::ST_Function)
continue;
// TODO: populate address map with PLT entries for better readability.
// Ignore function with 0 size for now (possibly coming from assembly).
auto SymbolSize = ELFSymbolRef(Symbol).getSize();
if (SymbolSize == 0)
continue;
ErrorOr<section_iterator> SectionOrErr = Symbol.getSection();
check_error(SectionOrErr.getError(), "cannot get symbol section");
section_iterator Section = *SectionOrErr;
if (Section == InputFile->section_end()) {
// Could be an absolute symbol. Could record for pretty printing.
continue;
}
// Checkout for conflicts with function data from FDEs.
bool IsSimple = true;
auto FDEI = CFIRdWrt->getFDEs().lower_bound(Address);
if (FDEI != CFIRdWrt->getFDEs().end()) {
auto &FDE = *FDEI->second;
if (FDEI->first != Address) {
// There's no matching starting address in FDE. Make sure the previous
// FDE does not contain this address.
if (FDEI != CFIRdWrt->getFDEs().begin()) {
--FDEI;
auto &PrevFDE = *FDEI->second;
auto PrevStart = PrevFDE.getInitialLocation();
auto PrevLength = PrevFDE.getAddressRange();
if (Address > PrevStart && Address < PrevStart + PrevLength) {
errs() << "BOLT-WARNING: function " << UniqueName
<< " is in conflict with FDE ["
<< Twine::utohexstr(PrevStart) << ", "
<< Twine::utohexstr(PrevStart + PrevLength)
<< "). Skipping.\n";
IsSimple = false;
}
}
} else if (FDE.getAddressRange() != SymbolSize) {
// Function addresses match but sizes differ.
errs() << "BOLT-WARNING: sizes differ for function " << UniqueName
<< ". FDE : " << FDE.getAddressRange()
<< "; symbol table : " << SymbolSize << ". Skipping.\n";
// Create maximum size non-simple function.
IsSimple = false;
SymbolSize = std::max(SymbolSize, FDE.getAddressRange());
}
}
auto BFI = BinaryFunctions.find(Address);
if (BFI != BinaryFunctions.end()) {
// Duplicate function name. Make sure everything matches before we add
// an alternative name.
if (SymbolSize != BFI->second.getSize()) {
errs() << "BOLT-WARNING: size mismatch for duplicate entries "
<< UniqueName << ':' << SymbolSize << " and "
<< BFI->second.getName() << ':' << BFI->second.getSize() << '\n';
}
BFI->second.addAlternativeName(UniqueName);
} else {
// Create the function and add it to the map.
auto Result = BinaryFunctions.emplace(
Address,
BinaryFunction(UniqueName, Symbol, *Section, Address, SymbolSize,
*BC, IsSimple));
BFI = Result.first;
}
if (!AlternativeName.empty())
BFI->second.addAlternativeName(AlternativeName);
}
if (!SeenFileName && BC->DR.hasLocalsWithFileName() && !opts::AllowStripped) {
errs() << "BOLT-ERROR: input binary does not have local file symbols "
"but profile data includes function names with embedded file "
"names. It appears that the input binary was stripped while a "
"profiled binary was not. If you know what you are doing and "
"wish to proceed, use -allow-stripped option.\n";
exit(1);
}
}
void RewriteInstance::readSpecialSections() {
// Process special sections.
StringRef FrameHdrContents;
for (const auto &Section : InputFile->sections()) {
StringRef SectionName;
check_error(Section.getName(SectionName), "cannot get section name");
StringRef SectionContents;
check_error(Section.getContents(SectionContents),
"cannot get section contents");
ArrayRef<uint8_t> SectionData(
reinterpret_cast<const uint8_t *>(SectionContents.data()),
Section.getSize());
if (SectionName == ".gcc_except_table") {
LSDAData = SectionData;
LSDAAddress = Section.getAddress();
} else if (SectionName == ".eh_frame_hdr") {
FrameHdrAddress = Section.getAddress();
FrameHdrContents = SectionContents;
FrameHdrAlign = Section.getAlignment();
} else if (SectionName == ".debug_loc") {
DebugLocSize = Section.getSize();
}
if (Section.isText() || Section.isData() || Section.isBSS()) {
BC->AllocatableSections.emplace(std::make_pair(Section.getAddress(),
Section));
}
}
FrameHdrCopy =
std::vector<char>(FrameHdrContents.begin(), FrameHdrContents.end());
// Process debug sections.
EHFrame = BC->DwCtx->getEHFrame();
if (opts::DumpEHFrame) {
EHFrame->dump(outs());
}
CFIRdWrt.reset(new CFIReaderWriter(*EHFrame, FrameHdrAddress, FrameHdrCopy));
if (!EHFrame->ParseError.empty()) {
errs() << "BOLT-ERROR: EHFrame reader failed with message \""
<< EHFrame->ParseError << "\"\n";
exit(1);
}
}
void RewriteInstance::readDebugInfo() {
if (!opts::UpdateDebugSections)
return;
BC->preprocessDebugInfo(BinaryFunctions);
}
void RewriteInstance::readFunctionDebugInfo() {
if (!opts::UpdateDebugSections)
return;
BC->preprocessFunctionDebugInfo(BinaryFunctions);
}
void RewriteInstance::disassembleFunctions() {
// Disassemble every function and build it's control flow graph.
TotalScore = 0;
for (auto &BFI : BinaryFunctions) {
BinaryFunction &Function = BFI.second;
if (!opts::shouldProcess(Function)) {
DEBUG(dbgs() << "BOLT: skipping processing function "
<< Function.getName() << " per user request.\n");
continue;
}
SectionRef Section = Function.getSection();
assert(Section.getAddress() <= Function.getAddress() &&
Section.getAddress() + Section.getSize()
>= Function.getAddress() + Function.getSize() &&
"wrong section for function");
if (!Section.isText() || Section.isVirtual() || !Section.getSize()) {
// When could it happen?
errs() << "BOLT: corresponding section is non-executable or empty "
<< "for function " << Function.getName();
continue;
}
// Set the proper maximum size value after the whole symbol table
// has been processed.
auto SymRefI = FileSymRefs.upper_bound(Function.getAddress());
if (SymRefI != FileSymRefs.end()) {
uint64_t MaxSize;
auto SectionIter = *SymRefI->second.getSection();
if (SectionIter != InputFile->section_end() &&
*SectionIter == Function.getSection()) {
MaxSize = SymRefI->first - Function.getAddress();
} else {
// Function runs till the end of the containing section assuming
// the section does not run over the next symbol.
uint64_t SectionEnd = Function.getSection().getAddress() +
Function.getSection().getSize();
if (SectionEnd > SymRefI->first) {
errs() << "BOLT-WARNING: symbol after " << Function.getName()
<< " should not be in the same section.\n";
MaxSize = 0;
} else {
MaxSize = SectionEnd - Function.getAddress();
}
}
if (MaxSize < Function.getSize()) {
errs() << "BOLT-WARNING: symbol seen in the middle of the function "
<< Function.getName() << ". Skipping.\n";
Function.setSimple(false);
continue;
}
Function.setMaxSize(MaxSize);
}
StringRef SectionContents;
check_error(Section.getContents(SectionContents),
"cannot get section contents");
assert(SectionContents.size() == Section.getSize() &&
"section size mismatch");
// Function offset from the section start.
auto FunctionOffset = Function.getAddress() - Section.getAddress();
// Offset of the function in the file.
Function.setFileOffset(
SectionContents.data() - InputFile->getData().data() + FunctionOffset);
ArrayRef<uint8_t> FunctionData(
reinterpret_cast<const uint8_t *>
(SectionContents.data()) + FunctionOffset,
Function.getSize());
if (!Function.disassemble(FunctionData))
continue;
if (opts::PrintAll || opts::PrintDisasm)
Function.print(errs(), "after disassembly", true);
if (!Function.isSimple())
continue;
// Fill in CFI information for this function
if (EHFrame->ParseError.empty()) {
if (!CFIRdWrt->fillCFIInfoFor(Function)) {
errs() << "BOLT-WARNING: unable to fill CFI for function "
<< Function.getName() << '\n';
Function.setSimple(false);
continue;
}
}
// Parse LSDA.
if (Function.getLSDAAddress() != 0)
Function.parseLSDA(LSDAData, LSDAAddress);
if (!Function.buildCFG())
continue;
if (opts::PrintAll || opts::PrintCFG)
Function.print(errs(), "after building cfg", true);
if (opts::DumpDotAll)
Function.dumpGraphForPass("build-cfg");
if (opts::PrintLoopInfo) {
Function.calculateLoopInfo();
Function.printLoopInfo(errs());
}
TotalScore += Function.getFunctionScore();
} // Iterate over all functions
// Mark all functions with internal addresses serving as interprocedural
// branch targets as not simple -- pretty rare but can happen in code
// written in assembly.
// TODO: #9301815
for (auto Addr : BC->InterproceduralBranchTargets) {
// Check if this address is internal to some function we are reordering
auto I = BinaryFunctions.upper_bound(Addr);
if (I == BinaryFunctions.begin())
continue;
BinaryFunction &Func = (--I)->second;
uint64_t Offset = Addr - I->first;
if (Offset == 0 || Offset >= Func.getSize())
continue;
errs() << "BOLT-WARNING: Function " << Func.getName()
<< " has internal BBs that are target of a branch located in "
"another function. We will not process this function.\n";
Func.setSimple(false);
}
uint64_t NumSimpleFunctions{0};
uint64_t NumStaleProfileFunctions{0};
std::vector<BinaryFunction *> ProfiledFunctions;
for (auto &BFI : BinaryFunctions) {
auto &Function = BFI.second;
if (!Function.isSimple())
continue;
++NumSimpleFunctions;
if (Function.getExecutionCount() == BinaryFunction::COUNT_NO_PROFILE)
continue;
if (Function.hasValidProfile())
ProfiledFunctions.push_back(&Function);
else
++NumStaleProfileFunctions;
}
errs() << "BOLT-INFO: "
<< ProfiledFunctions.size() + NumStaleProfileFunctions
<< " functions out of " << NumSimpleFunctions << " simple functions ("
<< format("%.1f",
(ProfiledFunctions.size() + NumStaleProfileFunctions) /
(float) NumSimpleFunctions * 100.0f)
<< "%) have non-empty execution profile.\n";
if (NumStaleProfileFunctions) {
errs() << "BOLT-INFO: " << NumStaleProfileFunctions
<< format(" (%.1f%) ", NumStaleProfileFunctions /
(float) NumSimpleFunctions * 100.0f)
<< " function" << (NumStaleProfileFunctions == 1 ? "" : "s")
<< " have invalid (possibly stale) profile.\n";
}
if (ProfiledFunctions.size() > 10) {
errs() << "BOLT-INFO: top called functions are:\n";
std::sort(ProfiledFunctions.begin(), ProfiledFunctions.end(),
[](BinaryFunction *A, BinaryFunction *B) {
return B->getExecutionCount() < A->getExecutionCount();
}
);
auto SFI = ProfiledFunctions.begin();
for (int i = 0; i < 100 && SFI != ProfiledFunctions.end(); ++SFI, ++i) {
errs() << " " << (*SFI)->getName() << " : "
<< (*SFI)->getExecutionCount() << '\n';
}
}
}
void RewriteInstance::runOptimizationPasses() {
// Run optimization passes.
//
BinaryFunctionPassManager::runAllPasses(*BC, BinaryFunctions, LargeFunctions);
}
namespace {
// Helper function to emit the contents of a function via a MCStreamer object.
void emitFunction(MCStreamer &Streamer, BinaryFunction &Function,
BinaryContext &BC, bool EmitColdPart) {
// Define a helper to decode and emit CFI instructions at a given point in a
// BB
auto emitCFIInstr = [&Streamer](MCCFIInstruction &CFIInstr) {
switch (CFIInstr.getOperation()) {
default:
llvm_unreachable("Unexpected instruction");
case MCCFIInstruction::OpDefCfaOffset:
Streamer.EmitCFIDefCfaOffset(CFIInstr.getOffset());
break;
case MCCFIInstruction::OpAdjustCfaOffset:
Streamer.EmitCFIAdjustCfaOffset(CFIInstr.getOffset());
break;
case MCCFIInstruction::OpDefCfa:
Streamer.EmitCFIDefCfa(CFIInstr.getRegister(), CFIInstr.getOffset());
break;
case MCCFIInstruction::OpDefCfaRegister:
Streamer.EmitCFIDefCfaRegister(CFIInstr.getRegister());
break;
case MCCFIInstruction::OpOffset:
Streamer.EmitCFIOffset(CFIInstr.getRegister(), CFIInstr.getOffset());
break;
case MCCFIInstruction::OpRegister:
Streamer.EmitCFIRegister(CFIInstr.getRegister(),
CFIInstr.getRegister2());
break;
case MCCFIInstruction::OpRelOffset:
Streamer.EmitCFIRelOffset(CFIInstr.getRegister(), CFIInstr.getOffset());
break;
case MCCFIInstruction::OpUndefined:
Streamer.EmitCFIUndefined(CFIInstr.getRegister());
break;
case MCCFIInstruction::OpRememberState:
Streamer.EmitCFIRememberState();
break;
case MCCFIInstruction::OpRestoreState:
Streamer.EmitCFIRestoreState();
break;
case MCCFIInstruction::OpRestore:
Streamer.EmitCFIRestore(CFIInstr.getRegister());
break;
case MCCFIInstruction::OpSameValue:
Streamer.EmitCFISameValue(CFIInstr.getRegister());
break;
case MCCFIInstruction::OpGnuArgsSize:
Streamer.EmitCFIGnuArgsSize(CFIInstr.getOffset());
break;
}
};
// No need for human readability?
// FIXME: what difference does it make in reality?
// Ctx.setUseNamesOnTempLabels(false);
// Emit function start
// Each fuction is emmitted into its own section.
MCSectionELF *FunctionSection =
EmitColdPart
? BC.Ctx->getELFSection(
Function.getCodeSectionName().str().append(".cold"),
ELF::SHT_PROGBITS, ELF::SHF_EXECINSTR | ELF::SHF_ALLOC)
: BC.Ctx->getELFSection(Function.getCodeSectionName(),
ELF::SHT_PROGBITS,
ELF::SHF_EXECINSTR | ELF::SHF_ALLOC);
MCSection *Section = FunctionSection;
Section->setHasInstructions(true);
BC.Ctx->addGenDwarfSection(Section);
Streamer.SwitchSection(Section);
Streamer.EmitCodeAlignment(Function.getAlignment());
if (!EmitColdPart) {
MCSymbol *FunctionSymbol = BC.Ctx->getOrCreateSymbol(Function.getName());
Streamer.EmitSymbolAttribute(FunctionSymbol, MCSA_ELF_TypeFunction);
Streamer.EmitLabel(FunctionSymbol);
Function.setOutputSymbol(FunctionSymbol);
} else {
MCSymbol *FunctionSymbol =
BC.Ctx->getOrCreateSymbol(Twine(Function.getName()).concat(".cold"));
Streamer.EmitSymbolAttribute(FunctionSymbol, MCSA_ELF_TypeFunction);
Streamer.EmitLabel(FunctionSymbol);
Function.cold().setOutputSymbol(FunctionSymbol);
}
// Emit CFI start
if (Function.hasCFI()) {
Streamer.EmitCFIStartProc(/*IsSimple=*/false);
if (Function.getPersonalityFunction() != nullptr) {
Streamer.EmitCFIPersonality(Function.getPersonalityFunction(),
Function.getPersonalityEncoding());
}
if (!EmitColdPart && Function.getLSDASymbol()) {
Streamer.EmitCFILsda(Function.getLSDASymbol(),
BC.MOFI->getLSDAEncoding());
} else {
Streamer.EmitCFILsda(0, dwarf::DW_EH_PE_omit);
}
// Emit CFI instructions relative to the CIE
for (auto &CFIInstr : Function.cie()) {
// Ignore these CIE CFI insns because LLVM will already emit this.
switch (CFIInstr.getOperation()) {
default:
break;
case MCCFIInstruction::OpDefCfa:
if (CFIInstr.getRegister() == 7 && CFIInstr.getOffset() == 8)
continue;
break;
case MCCFIInstruction::OpOffset:
if (CFIInstr.getRegister() == 16 && CFIInstr.getOffset() == -8)
continue;
break;
}
emitCFIInstr(CFIInstr);
}
}
assert(!(*Function.begin()).isCold() &&
"first basic block should never be cold");
// Emit UD2 at the beginning if requested by user.
if (!opts::BreakFunctionNames.empty()) {
for (auto &Name : opts::BreakFunctionNames) {
if (Function.hasName(Name)) {
Streamer.EmitIntValue(0x0B0F, 2); // UD2: 0F 0B
break;
}
}
}
// Emit code.
int64_t CurrentGnuArgsSize = 0;
for (auto BB : Function.layout()) {
if (EmitColdPart != BB->isCold())
continue;
if (opts::AlignBlocks && BB->getAlignment() > 1)
Streamer.EmitCodeAlignment(BB->getAlignment());
Streamer.EmitLabel(BB->getLabel());
// Remember last .debug_line entry emitted so that we don't repeat them in
// subsequent instructions, as gdb can figure it out by looking at the
// previous instruction with available line number info.
SMLoc LastLocSeen;
for (const auto &Instr : *BB) {
// Handle pseudo instructions.
if (BC.MIA->isEHLabel(Instr)) {
assert(Instr.getNumOperands() == 1 && Instr.getOperand(0).isExpr() &&
"bad EH_LABEL instruction");
auto Label = &(cast<MCSymbolRefExpr>(Instr.getOperand(0).getExpr())
->getSymbol());
Streamer.EmitLabel(const_cast<MCSymbol *>(Label));
continue;
}
if (BC.MIA->isCFI(Instr)) {
emitCFIInstr(*Function.getCFIFor(Instr));
continue;
}
if (opts::UpdateDebugSections) {
auto RowReference = DebugLineTableRowRef::fromSMLoc(Instr.getLoc());
if (RowReference != DebugLineTableRowRef::NULL_ROW &&
Instr.getLoc().getPointer() != LastLocSeen.getPointer()) {
auto ULT = Function.getDWARFUnitLineTable();
auto Unit = ULT.first;
auto OriginalLineTable = ULT.second;
assert(Unit && OriginalLineTable &&
"Invalid CU offset set in instruction debug info.");
assert(RowReference.DwCompileUnitIndex == Unit->getOffset() &&
"DWARF compile unit mismatch");
const auto &OriginalRow =
OriginalLineTable->Rows[RowReference.RowIndex - 1];
BC.Ctx->setCurrentDwarfLoc(
OriginalRow.File,
OriginalRow.Line,
OriginalRow.Column,
(DWARF2_FLAG_IS_STMT * OriginalRow.IsStmt) |
(DWARF2_FLAG_BASIC_BLOCK * OriginalRow.BasicBlock) |
(DWARF2_FLAG_PROLOGUE_END * OriginalRow.PrologueEnd) |
(DWARF2_FLAG_EPILOGUE_BEGIN * OriginalRow.EpilogueBegin),
OriginalRow.Isa,
OriginalRow.Discriminator);
BC.Ctx->setDwarfCompileUnitID(Unit->getOffset());
LastLocSeen = Instr.getLoc();
}
}
// Emit GNU_args_size CFIs as necessary.
if (Function.usesGnuArgsSize() && BC.MIA->isInvoke(Instr)) {
auto NewGnuArgsSize = BC.MIA->getGnuArgsSize(Instr);
if (NewGnuArgsSize >= 0 && NewGnuArgsSize != CurrentGnuArgsSize) {
CurrentGnuArgsSize = NewGnuArgsSize;
Streamer.EmitCFIGnuArgsSize(CurrentGnuArgsSize);
}
}
Streamer.EmitInstruction(Instr, *BC.STI);
}
MCSymbol *BBEndLabel = BC.Ctx->createTempSymbol();
BB->setEndLabel(BBEndLabel);
Streamer.EmitLabel(BBEndLabel);
}
// Emit CFI end
if (Function.hasCFI())
Streamer.EmitCFIEndProc();
if (!EmitColdPart && Function.getFunctionEndLabel())
Streamer.EmitLabel(Function.getFunctionEndLabel());
// Emit LSDA before anything else?
if (!EmitColdPart)
Function.emitLSDA(&Streamer);
// TODO: is there any use in emiting end of function?
// Perhaps once we have a support for C++ exceptions.
// auto FunctionEndLabel = Ctx.createTempSymbol("func_end");
// Streamer.EmitLabel(FunctionEndLabel);
// Streamer.emitELFSize(FunctionSymbol, MCExpr());
}
template <typename T>
std::vector<T> singletonSet(T t) {
std::vector<T> Vec;
Vec.push_back(std::move(t));
return Vec;
}
} // anonymous namespace
void RewriteInstance::emitFunctions() {
std::error_code EC;
// This is an object file, which we keep for debugging purposes.
// Once we decide it's useless, we should create it in memory.
std::unique_ptr<tool_output_file> TempOut =
llvm::make_unique<tool_output_file>(opts::OutputFilename + ".bolt.o",
EC, sys::fs::F_None);
check_error(EC, "cannot create output object file");
std::unique_ptr<buffer_ostream> BOS =
make_unique<buffer_ostream>(TempOut->os());
raw_pwrite_stream *OS = BOS.get();
// Implicitly MCObjectStreamer takes ownership of MCAsmBackend (MAB)
// and MCCodeEmitter (MCE). ~MCObjectStreamer() will delete these
// two instances.
auto MCE = BC->TheTarget->createMCCodeEmitter(*BC->MII, *BC->MRI, *BC->Ctx);
auto MAB = BC->TheTarget->createMCAsmBackend(*BC->MRI, BC->TripleName, "");
std::unique_ptr<MCStreamer> Streamer(
BC->TheTarget->createMCObjectStreamer(*BC->TheTriple,
*BC->Ctx,
*MAB,
*OS,
MCE,
*BC->STI,
/* RelaxAll */ false,
/* DWARFMustBeAtTheEnd */ false));
Streamer->InitSections(false);
// Output functions one by one.
for (auto &BFI : BinaryFunctions) {
auto &Function = BFI.second;
if (!Function.isSimple())
continue;
if (!opts::shouldProcess(Function))
continue;
DEBUG(dbgs() << "BOLT: generating code for function \""
<< Function.getName() << "\" : "
<< Function.getFunctionNumber() << '\n');
emitFunction(*Streamer, Function, *BC.get(), /*EmitColdPart=*/false);
if (Function.isSplit())
emitFunction(*Streamer, Function, *BC.get(), /*EmitColdPart=*/true);
}
if (opts::UpdateDebugSections)
updateDebugLineInfoForNonSimpleFunctions();
Streamer->Finish();
//////////////////////////////////////////////////////////////////////////////
// Assign addresses to new functions/sections.
//////////////////////////////////////////////////////////////////////////////
auto EFMM = new ExecutableFileMemoryManager();
SectionMM.reset(EFMM);
if (opts::UpdateDebugSections) {
// Compute offsets of tables in .debug_line for each compile unit.
updateLineTableOffsets();
}
// Get output object as ObjectFile.
std::unique_ptr<MemoryBuffer> ObjectMemBuffer =
MemoryBuffer::getMemBuffer(BOS->str(), "in-memory object file", false);
ErrorOr<std::unique_ptr<object::ObjectFile>> ObjOrErr =
object::ObjectFile::createObjectFile(ObjectMemBuffer->getMemBufferRef());
check_error(ObjOrErr.getError(), "error creating in-memory object");
// Run ObjectLinkingLayer() with custom memory manager and symbol resolver.
orc::ObjectLinkingLayer<> OLT;
auto Resolver = orc::createLambdaResolver(
[&](const std::string &Name) {
DEBUG(dbgs() << "BOLT: looking for " << Name << "\n");
auto I = BC->GlobalSymbols.find(Name);
if (I == BC->GlobalSymbols.end())
return RuntimeDyld::SymbolInfo(nullptr);
return RuntimeDyld::SymbolInfo(I->second,
JITSymbolFlags::None);
},
[](const std::string &S) {
DEBUG(dbgs() << "BOLT: resolving " << S << "\n");
return nullptr;
}
);
auto ObjectsHandle = OLT.addObjectSet(
singletonSet(std::move(ObjOrErr.get())),
SectionMM.get(),
std::move(Resolver),
/* ProcessAllSections = */true);
// FIXME: use notifyObjectLoaded() to remap sections.
// Map every function/section current address in memory to that in
// the output binary.
uint64_t NewTextSectionStartAddress = NextAvailableAddress;
for (auto &BFI : BinaryFunctions) {
auto &Function = BFI.second;
if (!Function.isSimple())
continue;
auto TooLarge = false;
auto SMII = EFMM->SectionMapInfo.find(Function.getCodeSectionName());
if (SMII != EFMM->SectionMapInfo.end()) {
DEBUG(dbgs() << "BOLT: mapping 0x"
<< Twine::utohexstr(SMII->second.AllocAddress)
<< " to 0x" << Twine::utohexstr(Function.getAddress())
<< '\n');
OLT.mapSectionAddress(ObjectsHandle,
SMII->second.SectionID,
Function.getAddress());
Function.setImageAddress(SMII->second.AllocAddress);
Function.setImageSize(SMII->second.Size);
if (Function.getImageSize() > Function.getMaxSize()) {
TooLarge = true;
FailedAddresses.emplace_back(Function.getAddress());
}
} else {
errs() << "BOLT: cannot remap function " << Function.getName() << "\n";
FailedAddresses.emplace_back(Function.getAddress());
}
if (!Function.isSplit())
continue;
SMII = EFMM->SectionMapInfo.find(
Function.getCodeSectionName().str().append(".cold"));
if (SMII != EFMM->SectionMapInfo.end()) {
// Cold fragments are aligned at 16 bytes.
NextAvailableAddress = RoundUpToAlignment(NextAvailableAddress, 16);
DEBUG(dbgs() << "BOLT: mapping 0x"
<< Twine::utohexstr(SMII->second.AllocAddress)
<< " to 0x" << Twine::utohexstr(NextAvailableAddress)
<< " with size " << Twine::utohexstr(SMII->second.Size)
<< '\n');
OLT.mapSectionAddress(ObjectsHandle,
SMII->second.SectionID,
NextAvailableAddress);
Function.cold().setAddress(NextAvailableAddress);
Function.cold().setImageAddress(SMII->second.AllocAddress);
Function.cold().setImageSize(TooLarge ? 0 : SMII->second.Size);
Function.cold().setFileOffset(getFileOffsetFor(NextAvailableAddress));
NextAvailableAddress += Function.cold().getImageSize();
} else {
errs() << "BOLT: cannot remap function " << Function.getName() << "\n";
FailedAddresses.emplace_back(Function.getAddress());
}
}
// Add the new text section aggregating all existing code sections.
auto NewTextSectionSize = NextAvailableAddress - NewTextSectionStartAddress;
if (NewTextSectionSize) {
SectionMM->SectionMapInfo[".bolt.text"] =
SectionInfo(0,
NewTextSectionSize,
16,
true /*IsCode*/,
true /*IsReadOnly*/,
NewTextSectionStartAddress,
getFileOffsetFor(NewTextSectionStartAddress));
}
// Map special sections to their addresses in the output image.
//
// TODO: perhaps we should process all the allocated sections here?
std::vector<std::string> Sections = { ".eh_frame", ".gcc_except_table" };
for (auto &SectionName : Sections) {
auto SMII = EFMM->SectionMapInfo.find(SectionName);
if (SMII != EFMM->SectionMapInfo.end()) {
SectionInfo &SI = SMII->second;
NextAvailableAddress = RoundUpToAlignment(NextAvailableAddress,
SI.Alignment);
DEBUG(dbgs() << "BOLT: mapping 0x"
<< Twine::utohexstr(SI.AllocAddress)
<< " to 0x" << Twine::utohexstr(NextAvailableAddress)
<< '\n');
OLT.mapSectionAddress(ObjectsHandle,
SI.SectionID,
NextAvailableAddress);
SI.FileAddress = NextAvailableAddress;
SI.FileOffset = getFileOffsetFor(NextAvailableAddress);
NextAvailableAddress += SI.Size;
} else {
errs() << "BOLT: cannot remap " << SectionName << '\n';
}
}
if (opts::UpdateDebugSections) {
MCAsmLayout Layout(
static_cast<MCObjectStreamer *>(Streamer.get())->getAssembler());
for (auto &BFI : BinaryFunctions) {
auto &Function = BFI.second;
for (auto &BB : Function) {
if (!(BB.getLabel()->isDefined(false) &&
BB.getEndLabel() && BB.getEndLabel()->isDefined(false))) {
continue;
}
uint64_t BaseAddress = (BB.isCold() ? Function.cold().getAddress()
: Function.getAddress());
uint64_t BeginAddress =
BaseAddress + Layout.getSymbolOffset(*BB.getLabel());
uint64_t EndAddress =
BaseAddress + Layout.getSymbolOffset(*BB.getEndLabel());
BB.setOutputAddressRange(std::make_pair(BeginAddress, EndAddress));
}
}
}
OLT.emitAndFinalize(ObjectsHandle);
if (opts::KeepTmp)
TempOut->keep();
}
bool RewriteInstance::checkLargeFunctions() {
LargeFunctions.clear();
for (auto &BFI : BinaryFunctions) {
auto &Function = BFI.second;
// Ignore this function if we failed to map it to the output binary
if (Function.getImageAddress() == 0 || Function.getImageSize() == 0)
continue;
if (Function.getImageSize() <= Function.getMaxSize())
continue;
LargeFunctions.insert(BFI.first);
}
return !LargeFunctions.empty();
}
void RewriteInstance::patchELFPHDRTable() {
auto ELF64LEFile = dyn_cast<ELF64LEObjectFile>(InputFile);
if (!ELF64LEFile) {
errs() << "BOLT-ERROR: only 64-bit LE ELF binaries are supported\n";
exit(1);
}
auto Obj = ELF64LEFile->getELFFile();
auto &OS = Out->os();
// Write/re-write program headers.
Phnum = Obj->getHeader()->e_phnum;
if (PHDRTableOffset) {
// Writing new pheader table.
Phnum += 1; // only adding one new segment
// Segment size includes the size of the PHDR area.
NewTextSegmentSize = NextAvailableAddress - PHDRTableAddress;
} else {
assert(!PHDRTableAddress && "unexpected address for program header table");
// Update existing table.
PHDRTableOffset = Obj->getHeader()->e_phoff;
NewTextSegmentSize = NextAvailableAddress - NewTextSegmentAddress;
}
OS.seek(PHDRTableOffset);
bool ModdedGnuStack = false;
bool AddedSegment = false;
// Copy existing program headers with modifications.
for (auto &Phdr : Obj->program_headers()) {
auto NewPhdr = Phdr;
if (PHDRTableAddress && Phdr.p_type == ELF::PT_PHDR) {
NewPhdr.p_offset = PHDRTableOffset;
NewPhdr.p_vaddr = PHDRTableAddress;
NewPhdr.p_paddr = PHDRTableAddress;
NewPhdr.p_filesz = sizeof(NewPhdr) * Phnum;
NewPhdr.p_memsz = sizeof(NewPhdr) * Phnum;
} else if (Phdr.p_type == ELF::PT_GNU_EH_FRAME) {
auto SMII = SectionMM->SectionMapInfo.find(".eh_frame_hdr");
if (SMII != SectionMM->SectionMapInfo.end()) {
auto &EHFrameHdrSecInfo = SMII->second;
NewPhdr.p_offset = EHFrameHdrSecInfo.FileOffset;
NewPhdr.p_vaddr = EHFrameHdrSecInfo.FileAddress;
NewPhdr.p_paddr = EHFrameHdrSecInfo.FileAddress;
NewPhdr.p_filesz = EHFrameHdrSecInfo.Size;
NewPhdr.p_memsz = EHFrameHdrSecInfo.Size;
}
} else if (opts::UseGnuStack && Phdr.p_type == ELF::PT_GNU_STACK) {
NewPhdr.p_type = ELF::PT_LOAD;
NewPhdr.p_offset = NewTextSegmentOffset;
NewPhdr.p_vaddr = NewTextSegmentAddress;
NewPhdr.p_paddr = NewTextSegmentAddress;
NewPhdr.p_filesz = NewTextSegmentSize;
NewPhdr.p_memsz = NewTextSegmentSize;
NewPhdr.p_flags = ELF::PF_X | ELF::PF_R;
NewPhdr.p_align = PageAlign;
ModdedGnuStack = true;
} else if (!opts::UseGnuStack && Phdr.p_type == ELF::PT_DYNAMIC) {
// Insert new pheader
ELFFile<ELF64LE>::Elf_Phdr NewTextPhdr;
NewTextPhdr.p_type = ELF::PT_LOAD;
NewTextPhdr.p_offset = PHDRTableOffset;
NewTextPhdr.p_vaddr = PHDRTableAddress;
NewTextPhdr.p_paddr = PHDRTableAddress;
NewTextPhdr.p_filesz = NewTextSegmentSize;
NewTextPhdr.p_memsz = NewTextSegmentSize;
NewTextPhdr.p_flags = ELF::PF_X | ELF::PF_R;
NewTextPhdr.p_align = PageAlign;
OS.write(reinterpret_cast<const char *>(&NewTextPhdr),
sizeof(NewTextPhdr));
AddedSegment = true;
}
OS.write(reinterpret_cast<const char *>(&NewPhdr), sizeof(NewPhdr));
}
assert((!opts::UseGnuStack || ModdedGnuStack) &&
"could not find GNU_STACK program header to modify");
assert((opts::UseGnuStack || AddedSegment) &&
"could not add program header for the new segment");
}
void RewriteInstance::rewriteNoteSections() {
auto ELF64LEFile = dyn_cast<ELF64LEObjectFile>(InputFile);
if (!ELF64LEFile) {
errs() << "BOLT-ERROR: only 64-bit LE ELF binaries are supported\n";
exit(1);
}
auto Obj = ELF64LEFile->getELFFile();
auto &OS = Out->os();
uint64_t NextAvailableOffset = getFileOffsetFor(NextAvailableAddress);
assert(NextAvailableOffset >= FirstNonAllocatableOffset &&
"next available offset calculation failure");
OS.seek(NextAvailableOffset);
// Copy over non-allocatable section contents and update file offsets.
for (auto &Section : Obj->sections()) {
if (Section.sh_type == ELF::SHT_NULL)
continue;
if (Section.sh_flags & ELF::SHF_ALLOC)
continue;
// Insert padding as needed.
if (Section.sh_addralign > 1) {
auto Padding = OffsetToAlignment(NextAvailableOffset,
Section.sh_addralign);
const unsigned char ZeroByte{0};
for (unsigned I = 0; I < Padding; ++I)
OS.write(ZeroByte);
NextAvailableOffset += Padding;
assert(Section.sh_size % Section.sh_addralign == 0 &&
"section size does not match section alignment");
}
ErrorOr<StringRef> SectionName = Obj->getSectionName(&Section);
check_error(SectionName.getError(), "cannot get section name");
// New section size.
uint64_t Size = 0;
// Copy over section contents unless it's one of the sections we ovewrite.
if (!shouldOverwriteSection(*SectionName)) {
Size = Section.sh_size;
std::string Data = InputFile->getData().substr(Section.sh_offset, Size);
auto SectionPatchersIt = SectionPatchers.find(*SectionName);
if (SectionPatchersIt != SectionPatchers.end()) {
(*SectionPatchersIt->second).patchBinary(Data);
}
OS << Data;
}
// Address of extension to the section.
uint64_t Address{0};
// Perform section post-processing.
auto SII = SectionMM->NoteSectionInfo.find(*SectionName);
if (SII != SectionMM->NoteSectionInfo.end()) {
auto &SI = SII->second;
assert(SI.Alignment <= Section.sh_addralign &&
"alignment exceeds value in file");
// Write section extension.
Address = SI.AllocAddress;
if (Address) {
DEBUG(dbgs() << "BOLT: " << (Size ? "appending" : "writing")
<< " contents to section "
<< *SectionName << '\n');
OS.write(reinterpret_cast<const char *>(Address), SI.Size);
Size += SI.Size;
}
if (!SI.PendingRelocs.empty()) {
DEBUG(dbgs() << "BOLT-DEBUG: processing relocs for section "
<< *SectionName << '\n');
for (auto &Reloc : SI.PendingRelocs) {
DEBUG(dbgs() << "BOLT-DEBUG: writing value "
<< Twine::utohexstr(Reloc.Value)
<< " of size " << (unsigned)Reloc.Size
<< " at offset "
<< Twine::utohexstr(Reloc.Offset) << '\n');
assert(Reloc.Size == 4 &&
"only relocations of size 4 are supported at the moment");
OS.pwrite(reinterpret_cast<const char*>(&Reloc.Value),
Reloc.Size,
NextAvailableOffset + Reloc.Offset);
}
}
}
// Set/modify section info.
SectionMM->NoteSectionInfo[*SectionName] =
SectionInfo(Address,
Size,
Section.sh_addralign,
/*IsCode=*/false,
/*IsReadOnly=*/false,
/*FileAddress=*/0,
NextAvailableOffset);
NextAvailableOffset += Size;
}
}
// Rewrite section header table inserting new entries as needed. The sections
// header table size itself may affect the offsets of other sections,
// so we are placing it at the end of the binary.
//
// As we rewrite entries we need to track how many sections were inserted
// as it changes the sh_link value.
//
// The following are assumptoins about file modifications:
// * There are no modifications done to existing allocatable sections.
// * All new allocatable sections are written emmediately after existing
// allocatable sections.
// * There could be modifications done to non-allocatable sections, e.g.
// size could be increased.
// * New non-allocatable sections are added to the end of the file.
void RewriteInstance::patchELFSectionHeaderTable() {
auto ELF64LEFile = dyn_cast<ELF64LEObjectFile>(InputFile);
if (!ELF64LEFile) {
errs() << "BOLT-ERROR: only 64-bit LE ELF binaries are supported\n";
exit(1);
}
auto Obj = ELF64LEFile->getELFFile();
using Elf_Shdr = std::remove_pointer<decltype(Obj)>::type::Elf_Shdr;
auto &OS = Out->os();
auto SHTOffset = OS.tell();
// Copy over entries for original allocatable sections with minor
// modifications (e.g. name).
for (auto &Section : Obj->sections()) {
// Always ignore this section.
if (Section.sh_type == ELF::SHT_NULL) {
OS.write(reinterpret_cast<const char *>(&Section), sizeof(Section));
continue;
}
// Break at first non-allocatable section.
if (!(Section.sh_flags & ELF::SHF_ALLOC))
break;
ErrorOr<StringRef> SectionName = Obj->getSectionName(&Section);
check_error(SectionName.getError(), "cannot get section name");
auto NewSection = Section;
if (*SectionName == ".bss") {
// .bss section offset matches that of the next section.
NewSection.sh_offset = NewTextSegmentOffset;
}
auto SMII = SectionMM->SectionMapInfo.find(*SectionName);
if (SMII != SectionMM->SectionMapInfo.end()) {
auto &SecInfo = SMII->second;
SecInfo.ShName = Section.sh_name;
}
OS.write(reinterpret_cast<const char *>(&NewSection), sizeof(NewSection));
}
// Create entries for new allocatable sections.
std::vector<Elf_Shdr> SectionsToRewrite;
for (auto &SMII : SectionMM->SectionMapInfo) {
SectionInfo &SI = SMII.second;
// Ignore function sections.
if (SI.IsCode && SMII.first != ".bolt.text")
continue;
errs() << "BOLT-INFO: writing section header for "
<< SMII.first << '\n';
Elf_Shdr NewSection;
NewSection.sh_name = SI.ShName;
NewSection.sh_type = ELF::SHT_PROGBITS;
NewSection.sh_addr = SI.FileAddress;
NewSection.sh_offset = SI.FileOffset;
NewSection.sh_size = SI.Size;
NewSection.sh_entsize = 0;
NewSection.sh_flags = ELF::SHF_ALLOC | ELF::SHF_EXECINSTR;
NewSection.sh_link = 0;
NewSection.sh_info = 0;
NewSection.sh_addralign = SI.Alignment;
SectionsToRewrite.emplace_back(NewSection);
}
// Write section header entries for new allocatable sections in offset order.
std::stable_sort(SectionsToRewrite.begin(), SectionsToRewrite.end(),
[] (Elf_Shdr A, Elf_Shdr B) {
return A.sh_offset < B.sh_offset;
});
for (auto &SI : SectionsToRewrite) {
OS.write(reinterpret_cast<const char *>(&SI),
sizeof(SI));
}
auto NumNewSections = SectionsToRewrite.size();
// Copy over entries for non-allocatable sections performing necessary
// adjustements.
for (auto &Section : Obj->sections()) {
if (Section.sh_type == ELF::SHT_NULL)
continue;
if (Section.sh_flags & ELF::SHF_ALLOC)
continue;
ErrorOr<StringRef> SectionName = Obj->getSectionName(&Section);
check_error(SectionName.getError(), "cannot get section name");
auto SII = SectionMM->NoteSectionInfo.find(*SectionName);
assert(SII != SectionMM->NoteSectionInfo.end() &&
"missing section info for non-allocatable section");
auto NewSection = Section;
NewSection.sh_offset = SII->second.FileOffset;
NewSection.sh_size = SII->second.Size;
// Adjust sh_link for sections that use it.
if (Section.sh_link)
NewSection.sh_link = Section.sh_link + NumNewSections;
// Adjust sh_info for relocation sections.
if (Section.sh_type == ELF::SHT_REL || Section.sh_type == ELF::SHT_RELA) {
if (Section.sh_info)
NewSection.sh_info = Section.sh_info + NumNewSections;
}
OS.write(reinterpret_cast<const char *>(&NewSection), sizeof(NewSection));
}
// FIXME: Update _end in .dynamic
// Fix ELF header.
auto NewEhdr = *Obj->getHeader();
NewEhdr.e_phoff = PHDRTableOffset;
NewEhdr.e_phnum = Phnum;
NewEhdr.e_shoff = SHTOffset;
NewEhdr.e_shnum = NewEhdr.e_shnum + NumNewSections;
NewEhdr.e_shstrndx = NewEhdr.e_shstrndx + NumNewSections;
OS.pwrite(reinterpret_cast<const char *>(&NewEhdr), sizeof(NewEhdr), 0);
}
void RewriteInstance::rewriteFile() {
// We obtain an asm-specific writer so that we can emit nops in an
// architecture-specific way at the end of the function.
auto MCE = BC->TheTarget->createMCCodeEmitter(*BC->MII, *BC->MRI, *BC->Ctx);
auto MAB = BC->TheTarget->createMCAsmBackend(*BC->MRI, BC->TripleName, "");
std::unique_ptr<MCStreamer> Streamer(
BC->TheTarget->createMCObjectStreamer(*BC->TheTriple,
*BC->Ctx,
*MAB,
Out->os(),
MCE,
*BC->STI,
/* RelaxAll */ false,
/* DWARFMustBeAtTheEnd */ false));
auto &Writer = static_cast<MCObjectStreamer *>(Streamer.get())
->getAssembler()
.getWriter();
// Make sure output stream has enough reserved space, otherwise
// pwrite() will fail.
auto Offset = Out->os().seek(getFileOffsetFor(NextAvailableAddress));
assert(Offset == getFileOffsetFor(NextAvailableAddress) &&
"error resizing output file");
// Overwrite function in the output file.
uint64_t CountOverwrittenFunctions = 0;
uint64_t OverwrittenScore = 0;
for (auto &BFI : BinaryFunctions) {
auto &Function = BFI.second;
if (Function.getImageAddress() == 0 || Function.getImageSize() == 0)
continue;
if (Function.isSplit() && (Function.cold().getImageAddress() == 0 ||
Function.cold().getImageSize() == 0))
continue;
if (Function.getImageSize() > Function.getMaxSize()) {
errs() << "BOLT-WARNING: new function size (0x"
<< Twine::utohexstr(Function.getImageSize())
<< ") is larger than maximum allowed size (0x"
<< Twine::utohexstr(Function.getMaxSize())
<< ") for function " << Function.getName() << '\n';
FailedAddresses.emplace_back(Function.getAddress());
continue;
}
OverwrittenScore += Function.getFunctionScore();
// Overwrite function in the output file.
outs() << "BOLT: rewriting function \"" << Function.getName() << "\"\n";
Out->os().pwrite(reinterpret_cast<char *>(Function.getImageAddress()),
Function.getImageSize(), Function.getFileOffset());
// Write nops at the end of the function.
auto Pos = Out->os().tell();
Out->os().seek(Function.getFileOffset() + Function.getImageSize());
MAB->writeNopData(Function.getMaxSize() - Function.getImageSize(),
&Writer);
Out->os().seek(Pos);
if (!Function.isSplit()) {
++CountOverwrittenFunctions;
if (opts::MaxFunctions &&
CountOverwrittenFunctions == opts::MaxFunctions) {
outs() << "BOLT: maximum number of functions reached\n";
break;
}
continue;
}
// Write cold part
outs() << "BOLT: rewriting function \"" << Function.getName()
<< "\" (cold part)\n";
Out->os().pwrite(reinterpret_cast<char*>(Function.cold().getImageAddress()),
Function.cold().getImageSize(),
Function.cold().getFileOffset());
// FIXME: write nops after cold part too.
++CountOverwrittenFunctions;
if (opts::MaxFunctions && CountOverwrittenFunctions == opts::MaxFunctions) {
outs() << "BOLT: maximum number of functions reached\n";
break;
}
}
// Print function statistics.
outs() << "BOLT: " << CountOverwrittenFunctions
<< " out of " << BinaryFunctions.size()
<< " functions were overwritten.\n";
if (TotalScore != 0) {
double Coverage = OverwrittenScore / (double)TotalScore * 100.0;
outs() << format("BOLT: Rewritten functions cover %.2lf", Coverage)
<< "% of the execution count of simple functions of this binary.\n";
}
// Write all non-code sections.
for (auto &SMII : SectionMM->SectionMapInfo) {
SectionInfo &SI = SMII.second;
if (SI.IsCode)
continue;
outs() << "BOLT: writing new section " << SMII.first << '\n';
Out->os().pwrite(reinterpret_cast<const char *>(SI.AllocAddress),
SI.Size,
SI.FileOffset);
}
// If .eh_frame is present it requires special handling.
auto SMII = SectionMM->SectionMapInfo.find(".eh_frame");
if (SMII != SectionMM->SectionMapInfo.end()) {
auto &EHFrameSecInfo = SMII->second;
outs() << "BOLT: writing a new .eh_frame_hdr\n";
if (FrameHdrAlign > 1) {
NextAvailableAddress =
RoundUpToAlignment(NextAvailableAddress, FrameHdrAlign);
}
SectionInfo EHFrameHdrSecInfo;
EHFrameHdrSecInfo.FileAddress = NextAvailableAddress;
EHFrameHdrSecInfo.FileOffset = getFileOffsetFor(NextAvailableAddress);
std::sort(FailedAddresses.begin(), FailedAddresses.end());
CFIRdWrt->rewriteHeaderFor(
StringRef(reinterpret_cast<const char *>(EHFrameSecInfo.AllocAddress),
EHFrameSecInfo.Size),
EHFrameSecInfo.FileAddress,
EHFrameHdrSecInfo.FileAddress,
FailedAddresses);
EHFrameHdrSecInfo.Size = FrameHdrCopy.size();
assert(Out->os().tell() == EHFrameHdrSecInfo.FileOffset &&
"offset mismatch");
Out->os().write(FrameHdrCopy.data(), EHFrameHdrSecInfo.Size);
SectionMM->SectionMapInfo[".eh_frame_hdr"] = EHFrameHdrSecInfo;
NextAvailableAddress += EHFrameHdrSecInfo.Size;
}
// Patch program header table.
patchELFPHDRTable();
// Copy non-allocatable sections once allocatable part is finished.
rewriteNoteSections();
// Update ELF book-keeping info.
patchELFSectionHeaderTable();
// TODO: we should find a way to mark the binary as optimized by us.
Out->keep();
}
bool RewriteInstance::shouldOverwriteSection(StringRef SectionName) {
if (opts::UpdateDebugSections) {
for (auto &OverwriteName : DebugSectionsToOverwrite) {
if (SectionName == OverwriteName)
return true;
}
}
return false;
}
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