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llvm-mirror/tools/dsymutil/DwarfLinker.cpp
Frederic Riss a282092928 [dsymutil] Add support for debug_loc section. 
There is no need to look into the location expressions to transfer them,
the only modification to apply is to patch their base address to reflect
the linked function address.

llvm-svn: 232267
2015-03-14 15:49:07 +00:00

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//===- tools/dsymutil/DwarfLinker.cpp - Dwarf debug info linker -----------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "DebugMap.h"
#include "BinaryHolder.h"
#include "DebugMap.h"
#include "dsymutil.h"
#include "llvm/ADT/IntervalMap.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/DIE.h"
#include "llvm/DebugInfo/DWARF/DWARFContext.h"
#include "llvm/DebugInfo/DWARF/DWARFDebugInfoEntry.h"
#include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/Object/MachO.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include <string>
#include <tuple>
namespace llvm {
namespace dsymutil {
namespace {
void warn(const Twine &Warning, const Twine &Context) {
errs() << Twine("while processing ") + Context + ":\n";
errs() << Twine("warning: ") + Warning + "\n";
}
bool error(const Twine &Error, const Twine &Context) {
errs() << Twine("while processing ") + Context + ":\n";
errs() << Twine("error: ") + Error + "\n";
return false;
}
template <typename KeyT, typename ValT>
using HalfOpenIntervalMap =
IntervalMap<KeyT, ValT, IntervalMapImpl::NodeSizer<KeyT, ValT>::LeafSize,
IntervalMapHalfOpenInfo<KeyT>>;
typedef HalfOpenIntervalMap<uint64_t, int64_t> FunctionIntervals;
/// \brief Stores all information relating to a compile unit, be it in
/// its original instance in the object file to its brand new cloned
/// and linked DIE tree.
class CompileUnit {
public:
/// \brief Information gathered about a DIE in the object file.
struct DIEInfo {
int64_t AddrAdjust; ///< Address offset to apply to the described entity.
DIE *Clone; ///< Cloned version of that DIE.
uint32_t ParentIdx; ///< The index of this DIE's parent.
bool Keep; ///< Is the DIE part of the linked output?
bool InDebugMap; ///< Was this DIE's entity found in the map?
};
CompileUnit(DWARFUnit &OrigUnit, unsigned ID)
: OrigUnit(OrigUnit), ID(ID), LowPc(UINT64_MAX), HighPc(0), RangeAlloc(),
Ranges(RangeAlloc), UnitRangeAttribute(nullptr) {
Info.resize(OrigUnit.getNumDIEs());
}
CompileUnit(CompileUnit &&RHS)
: OrigUnit(RHS.OrigUnit), Info(std::move(RHS.Info)),
CUDie(std::move(RHS.CUDie)), StartOffset(RHS.StartOffset),
NextUnitOffset(RHS.NextUnitOffset), RangeAlloc(), Ranges(RangeAlloc) {
// The CompileUnit container has been 'reserve()'d with the right
// size. We cannot move the IntervalMap anyway.
llvm_unreachable("CompileUnits should not be moved.");
}
DWARFUnit &getOrigUnit() const { return OrigUnit; }
unsigned getUniqueID() const { return ID; }
DIE *getOutputUnitDIE() const { return CUDie.get(); }
void setOutputUnitDIE(DIE *Die) { CUDie.reset(Die); }
DIEInfo &getInfo(unsigned Idx) { return Info[Idx]; }
const DIEInfo &getInfo(unsigned Idx) const { return Info[Idx]; }
uint64_t getStartOffset() const { return StartOffset; }
uint64_t getNextUnitOffset() const { return NextUnitOffset; }
void setStartOffset(uint64_t DebugInfoSize) { StartOffset = DebugInfoSize; }
uint64_t getLowPc() const { return LowPc; }
uint64_t getHighPc() const { return HighPc; }
DIEInteger *getUnitRangesAttribute() const { return UnitRangeAttribute; }
const FunctionIntervals &getFunctionRanges() const { return Ranges; }
const std::vector<DIEInteger *> &getRangesAttributes() const {
return RangeAttributes;
}
const std::vector<std::pair<DIEInteger *, int64_t>> &
getLocationAttributes() const {
return LocationAttributes;
}
/// \brief Compute the end offset for this unit. Must be
/// called after the CU's DIEs have been cloned.
/// \returns the next unit offset (which is also the current
/// debug_info section size).
uint64_t computeNextUnitOffset();
/// \brief Keep track of a forward reference to DIE \p Die in \p
/// RefUnit by \p Attr. The attribute should be fixed up later to
/// point to the absolute offset of \p Die in the debug_info section.
void noteForwardReference(DIE *Die, const CompileUnit *RefUnit,
DIEInteger *Attr);
/// \brief Apply all fixups recored by noteForwardReference().
void fixupForwardReferences();
/// \brief Add a function range [\p LowPC, \p HighPC) that is
/// relocatad by applying offset \p PCOffset.
void addFunctionRange(uint64_t LowPC, uint64_t HighPC, int64_t PCOffset);
/// \brief Keep track of a DW_AT_range attribute that we will need to
/// patch up later.
void noteRangeAttribute(const DIE &Die, DIEInteger *Attr);
/// \brief Keep track of a location attribute pointing to a location
/// list in the debug_loc section.
void noteLocationAttribute(DIEInteger *Attr, int64_t PcOffset);
private:
DWARFUnit &OrigUnit;
unsigned ID;
std::vector<DIEInfo> Info; ///< DIE info indexed by DIE index.
std::unique_ptr<DIE> CUDie; ///< Root of the linked DIE tree.
uint64_t StartOffset;
uint64_t NextUnitOffset;
uint64_t LowPc;
uint64_t HighPc;
/// \brief A list of attributes to fixup with the absolute offset of
/// a DIE in the debug_info section.
///
/// The offsets for the attributes in this array couldn't be set while
/// cloning because for cross-cu forward refences the target DIE's
/// offset isn't known you emit the reference attribute.
std::vector<std::tuple<DIE *, const CompileUnit *, DIEInteger *>>
ForwardDIEReferences;
FunctionIntervals::Allocator RangeAlloc;
/// \brief The ranges in that interval map are the PC ranges for
/// functions in this unit, associated with the PC offset to apply
/// to the addresses to get the linked address.
FunctionIntervals Ranges;
/// \brief DW_AT_ranges attributes to patch after we have gathered
/// all the unit's function addresses.
/// @{
std::vector<DIEInteger *> RangeAttributes;
DIEInteger *UnitRangeAttribute;
/// @}
/// \brief Location attributes that need to be transfered from th
/// original debug_loc section to the liked one. They are stored
/// along with the PC offset that is to be applied to their
/// function's address.
std::vector<std::pair<DIEInteger *, int64_t>> LocationAttributes;
};
uint64_t CompileUnit::computeNextUnitOffset() {
NextUnitOffset = StartOffset + 11 /* Header size */;
// The root DIE might be null, meaning that the Unit had nothing to
// contribute to the linked output. In that case, we will emit the
// unit header without any actual DIE.
if (CUDie)
NextUnitOffset += CUDie->getSize();
return NextUnitOffset;
}
/// \brief Keep track of a forward cross-cu reference from this unit
/// to \p Die that lives in \p RefUnit.
void CompileUnit::noteForwardReference(DIE *Die, const CompileUnit *RefUnit,
DIEInteger *Attr) {
ForwardDIEReferences.emplace_back(Die, RefUnit, Attr);
}
/// \brief Apply all fixups recorded by noteForwardReference().
void CompileUnit::fixupForwardReferences() {
for (const auto &Ref : ForwardDIEReferences) {
DIE *RefDie;
const CompileUnit *RefUnit;
DIEInteger *Attr;
std::tie(RefDie, RefUnit, Attr) = Ref;
Attr->setValue(RefDie->getOffset() + RefUnit->getStartOffset());
}
}
void CompileUnit::addFunctionRange(uint64_t FuncLowPc, uint64_t FuncHighPc,
int64_t PcOffset) {
Ranges.insert(FuncLowPc, FuncHighPc, PcOffset);
this->LowPc = std::min(LowPc, FuncLowPc + PcOffset);
this->HighPc = std::max(HighPc, FuncHighPc + PcOffset);
}
void CompileUnit::noteRangeAttribute(const DIE &Die, DIEInteger *Attr) {
if (Die.getTag() != dwarf::DW_TAG_compile_unit)
RangeAttributes.push_back(Attr);
else
UnitRangeAttribute = Attr;
}
void CompileUnit::noteLocationAttribute(DIEInteger *Attr, int64_t PcOffset) {
LocationAttributes.emplace_back(Attr, PcOffset);
}
/// \brief A string table that doesn't need relocations.
///
/// We are doing a final link, no need for a string table that
/// has relocation entries for every reference to it. This class
/// provides this ablitity by just associating offsets with
/// strings.
class NonRelocatableStringpool {
public:
/// \brief Entries are stored into the StringMap and simply linked
/// together through the second element of this pair in order to
/// keep track of insertion order.
typedef StringMap<std::pair<uint32_t, StringMapEntryBase *>, BumpPtrAllocator>
MapTy;
NonRelocatableStringpool()
: CurrentEndOffset(0), Sentinel(0), Last(&Sentinel) {
// Legacy dsymutil puts an empty string at the start of the line
// table.
getStringOffset("");
}
/// \brief Get the offset of string \p S in the string table. This
/// can insert a new element or return the offset of a preexisitng
/// one.
uint32_t getStringOffset(StringRef S);
/// \brief Get permanent storage for \p S (but do not necessarily
/// emit \p S in the output section).
/// \returns The StringRef that points to permanent storage to use
/// in place of \p S.
StringRef internString(StringRef S);
// \brief Return the first entry of the string table.
const MapTy::MapEntryTy *getFirstEntry() const {
return getNextEntry(&Sentinel);
}
// \brief Get the entry following \p E in the string table or null
// if \p E was the last entry.
const MapTy::MapEntryTy *getNextEntry(const MapTy::MapEntryTy *E) const {
return static_cast<const MapTy::MapEntryTy *>(E->getValue().second);
}
uint64_t getSize() { return CurrentEndOffset; }
private:
MapTy Strings;
uint32_t CurrentEndOffset;
MapTy::MapEntryTy Sentinel, *Last;
};
/// \brief Get the offset of string \p S in the string table. This
/// can insert a new element or return the offset of a preexisitng
/// one.
uint32_t NonRelocatableStringpool::getStringOffset(StringRef S) {
if (S.empty() && !Strings.empty())
return 0;
std::pair<uint32_t, StringMapEntryBase *> Entry(0, nullptr);
MapTy::iterator It;
bool Inserted;
// A non-empty string can't be at offset 0, so if we have an entry
// with a 0 offset, it must be a previously interned string.
std::tie(It, Inserted) = Strings.insert(std::make_pair(S, Entry));
if (Inserted || It->getValue().first == 0) {
// Set offset and chain at the end of the entries list.
It->getValue().first = CurrentEndOffset;
CurrentEndOffset += S.size() + 1; // +1 for the '\0'.
Last->getValue().second = &*It;
Last = &*It;
}
return It->getValue().first;
}
/// \brief Put \p S into the StringMap so that it gets permanent
/// storage, but do not actually link it in the chain of elements
/// that go into the output section. A latter call to
/// getStringOffset() with the same string will chain it though.
StringRef NonRelocatableStringpool::internString(StringRef S) {
std::pair<uint32_t, StringMapEntryBase *> Entry(0, nullptr);
auto InsertResult = Strings.insert(std::make_pair(S, Entry));
return InsertResult.first->getKey();
}
/// \brief The Dwarf streaming logic
///
/// All interactions with the MC layer that is used to build the debug
/// information binary representation are handled in this class.
class DwarfStreamer {
/// \defgroup MCObjects MC layer objects constructed by the streamer
/// @{
std::unique_ptr<MCRegisterInfo> MRI;
std::unique_ptr<MCAsmInfo> MAI;
std::unique_ptr<MCObjectFileInfo> MOFI;
std::unique_ptr<MCContext> MC;
MCAsmBackend *MAB; // Owned by MCStreamer
std::unique_ptr<MCInstrInfo> MII;
std::unique_ptr<MCSubtargetInfo> MSTI;
MCCodeEmitter *MCE; // Owned by MCStreamer
MCStreamer *MS; // Owned by AsmPrinter
std::unique_ptr<TargetMachine> TM;
std::unique_ptr<AsmPrinter> Asm;
/// @}
/// \brief the file we stream the linked Dwarf to.
std::unique_ptr<raw_fd_ostream> OutFile;
uint32_t RangesSectionSize;
uint32_t LocSectionSize;
public:
/// \brief Actually create the streamer and the ouptut file.
///
/// This could be done directly in the constructor, but it feels
/// more natural to handle errors through return value.
bool init(Triple TheTriple, StringRef OutputFilename);
/// \brief Dump the file to the disk.
bool finish();
AsmPrinter &getAsmPrinter() const { return *Asm; }
/// \brief Set the current output section to debug_info and change
/// the MC Dwarf version to \p DwarfVersion.
void switchToDebugInfoSection(unsigned DwarfVersion);
/// \brief Emit the compilation unit header for \p Unit in the
/// debug_info section.
///
/// As a side effect, this also switches the current Dwarf version
/// of the MC layer to the one of U.getOrigUnit().
void emitCompileUnitHeader(CompileUnit &Unit);
/// \brief Recursively emit the DIE tree rooted at \p Die.
void emitDIE(DIE &Die);
/// \brief Emit the abbreviation table \p Abbrevs to the
/// debug_abbrev section.
void emitAbbrevs(const std::vector<DIEAbbrev *> &Abbrevs);
/// \brief Emit the string table described by \p Pool.
void emitStrings(const NonRelocatableStringpool &Pool);
/// \brief Emit debug_ranges for \p FuncRange by translating the
/// original \p Entries.
void emitRangesEntries(
int64_t UnitPcOffset, uint64_t OrigLowPc,
FunctionIntervals::const_iterator FuncRange,
const std::vector<DWARFDebugRangeList::RangeListEntry> &Entries,
unsigned AddressSize);
/// \brief Emit debug_aranges entries for \p Unit and if \p
/// DoRangesSection is true, also emit the debug_ranges entries for
/// the DW_TAG_compile_unit's DW_AT_ranges attribute.
void emitUnitRangesEntries(CompileUnit &Unit, bool DoRangesSection);
uint32_t getRangesSectionSize() const { return RangesSectionSize; }
/// \brief Emit the debug_loc contribution for \p Unit by copying
/// the entries from \p Dwarf and offseting them. Update the
/// location attributes to point to the new entries.
void emitLocationsForUnit(const CompileUnit &Unit, DWARFContext &Dwarf);
};
bool DwarfStreamer::init(Triple TheTriple, StringRef OutputFilename) {
std::string ErrorStr;
std::string TripleName;
StringRef Context = "dwarf streamer init";
// Get the target.
const Target *TheTarget =
TargetRegistry::lookupTarget(TripleName, TheTriple, ErrorStr);
if (!TheTarget)
return error(ErrorStr, Context);
TripleName = TheTriple.getTriple();
// Create all the MC Objects.
MRI.reset(TheTarget->createMCRegInfo(TripleName));
if (!MRI)
return error(Twine("no register info for target ") + TripleName, Context);
MAI.reset(TheTarget->createMCAsmInfo(*MRI, TripleName));
if (!MAI)
return error("no asm info for target " + TripleName, Context);
MOFI.reset(new MCObjectFileInfo);
MC.reset(new MCContext(MAI.get(), MRI.get(), MOFI.get()));
MOFI->InitMCObjectFileInfo(TripleName, Reloc::Default, CodeModel::Default,
*MC);
MAB = TheTarget->createMCAsmBackend(*MRI, TripleName, "");
if (!MAB)
return error("no asm backend for target " + TripleName, Context);
MII.reset(TheTarget->createMCInstrInfo());
if (!MII)
return error("no instr info info for target " + TripleName, Context);
MSTI.reset(TheTarget->createMCSubtargetInfo(TripleName, "", ""));
if (!MSTI)
return error("no subtarget info for target " + TripleName, Context);
MCE = TheTarget->createMCCodeEmitter(*MII, *MRI, *MC);
if (!MCE)
return error("no code emitter for target " + TripleName, Context);
// Create the output file.
std::error_code EC;
OutFile =
llvm::make_unique<raw_fd_ostream>(OutputFilename, EC, sys::fs::F_None);
if (EC)
return error(Twine(OutputFilename) + ": " + EC.message(), Context);
MS = TheTarget->createMCObjectStreamer(TripleName, *MC, *MAB, *OutFile, MCE,
*MSTI, false);
if (!MS)
return error("no object streamer for target " + TripleName, Context);
// Finally create the AsmPrinter we'll use to emit the DIEs.
TM.reset(TheTarget->createTargetMachine(TripleName, "", "", TargetOptions()));
if (!TM)
return error("no target machine for target " + TripleName, Context);
Asm.reset(TheTarget->createAsmPrinter(*TM, std::unique_ptr<MCStreamer>(MS)));
if (!Asm)
return error("no asm printer for target " + TripleName, Context);
RangesSectionSize = 0;
LocSectionSize = 0;
return true;
}
bool DwarfStreamer::finish() {
MS->Finish();
return true;
}
/// \brief Set the current output section to debug_info and change
/// the MC Dwarf version to \p DwarfVersion.
void DwarfStreamer::switchToDebugInfoSection(unsigned DwarfVersion) {
MS->SwitchSection(MOFI->getDwarfInfoSection());
MC->setDwarfVersion(DwarfVersion);
}
/// \brief Emit the compilation unit header for \p Unit in the
/// debug_info section.
///
/// A Dwarf scetion header is encoded as:
/// uint32_t Unit length (omiting this field)
/// uint16_t Version
/// uint32_t Abbreviation table offset
/// uint8_t Address size
///
/// Leading to a total of 11 bytes.
void DwarfStreamer::emitCompileUnitHeader(CompileUnit &Unit) {
unsigned Version = Unit.getOrigUnit().getVersion();
switchToDebugInfoSection(Version);
// Emit size of content not including length itself. The size has
// already been computed in CompileUnit::computeOffsets(). Substract
// 4 to that size to account for the length field.
Asm->EmitInt32(Unit.getNextUnitOffset() - Unit.getStartOffset() - 4);
Asm->EmitInt16(Version);
// We share one abbreviations table across all units so it's always at the
// start of the section.
Asm->EmitInt32(0);
Asm->EmitInt8(Unit.getOrigUnit().getAddressByteSize());
}
/// \brief Emit the \p Abbrevs array as the shared abbreviation table
/// for the linked Dwarf file.
void DwarfStreamer::emitAbbrevs(const std::vector<DIEAbbrev *> &Abbrevs) {
MS->SwitchSection(MOFI->getDwarfAbbrevSection());
Asm->emitDwarfAbbrevs(Abbrevs);
}
/// \brief Recursively emit the DIE tree rooted at \p Die.
void DwarfStreamer::emitDIE(DIE &Die) {
MS->SwitchSection(MOFI->getDwarfInfoSection());
Asm->emitDwarfDIE(Die);
}
/// \brief Emit the debug_str section stored in \p Pool.
void DwarfStreamer::emitStrings(const NonRelocatableStringpool &Pool) {
Asm->OutStreamer.SwitchSection(MOFI->getDwarfStrSection());
for (auto *Entry = Pool.getFirstEntry(); Entry;
Entry = Pool.getNextEntry(Entry))
Asm->OutStreamer.EmitBytes(
StringRef(Entry->getKey().data(), Entry->getKey().size() + 1));
}
/// \brief Emit the debug_range section contents for \p FuncRange by
/// translating the original \p Entries. The debug_range section
/// format is totally trivial, consisting just of pairs of address
/// sized addresses describing the ranges.
void DwarfStreamer::emitRangesEntries(
int64_t UnitPcOffset, uint64_t OrigLowPc,
FunctionIntervals::const_iterator FuncRange,
const std::vector<DWARFDebugRangeList::RangeListEntry> &Entries,
unsigned AddressSize) {
MS->SwitchSection(MC->getObjectFileInfo()->getDwarfRangesSection());
// Offset each range by the right amount.
int64_t PcOffset = FuncRange.value() + UnitPcOffset;
for (const auto &Range : Entries) {
if (Range.isBaseAddressSelectionEntry(AddressSize)) {
warn("unsupported base address selection operation",
"emitting debug_ranges");
break;
}
// Do not emit empty ranges.
if (Range.StartAddress == Range.EndAddress)
continue;
// All range entries should lie in the function range.
if (!(Range.StartAddress + OrigLowPc >= FuncRange.start() &&
Range.EndAddress + OrigLowPc <= FuncRange.stop()))
warn("inconsistent range data.", "emitting debug_ranges");
MS->EmitIntValue(Range.StartAddress + PcOffset, AddressSize);
MS->EmitIntValue(Range.EndAddress + PcOffset, AddressSize);
RangesSectionSize += 2 * AddressSize;
}
// Add the terminator entry.
MS->EmitIntValue(0, AddressSize);
MS->EmitIntValue(0, AddressSize);
RangesSectionSize += 2 * AddressSize;
}
/// \brief Emit the debug_aranges contribution of a unit and
/// if \p DoDebugRanges is true the debug_range contents for a
/// compile_unit level DW_AT_ranges attribute (Which are basically the
/// same thing with a different base address).
/// Just aggregate all the ranges gathered inside that unit.
void DwarfStreamer::emitUnitRangesEntries(CompileUnit &Unit,
bool DoDebugRanges) {
unsigned AddressSize = Unit.getOrigUnit().getAddressByteSize();
// Gather the ranges in a vector, so that we can simplify them. The
// IntervalMap will have coalesced the non-linked ranges, but here
// we want to coalesce the linked addresses.
std::vector<std::pair<uint64_t, uint64_t>> Ranges;
const auto &FunctionRanges = Unit.getFunctionRanges();
for (auto Range = FunctionRanges.begin(), End = FunctionRanges.end();
Range != End; ++Range)
Ranges.push_back(std::make_pair(Range.start() + Range.value(),
Range.stop() + Range.value()));
// The object addresses where sorted, but again, the linked
// addresses might end up in a different order.
std::sort(Ranges.begin(), Ranges.end());
if (!Ranges.empty()) {
MS->SwitchSection(MC->getObjectFileInfo()->getDwarfARangesSection());
MCSymbol *BeginLabel = Asm->GetTempSymbol("Barange", Unit.getUniqueID());
MCSymbol *EndLabel = Asm->GetTempSymbol("Earange", Unit.getUniqueID());
unsigned HeaderSize =
sizeof(int32_t) + // Size of contents (w/o this field
sizeof(int16_t) + // DWARF ARange version number
sizeof(int32_t) + // Offset of CU in the .debug_info section
sizeof(int8_t) + // Pointer Size (in bytes)
sizeof(int8_t); // Segment Size (in bytes)
unsigned TupleSize = AddressSize * 2;
unsigned Padding = OffsetToAlignment(HeaderSize, TupleSize);
Asm->EmitLabelDifference(EndLabel, BeginLabel, 4); // Arange length
Asm->OutStreamer.EmitLabel(BeginLabel);
Asm->EmitInt16(dwarf::DW_ARANGES_VERSION); // Version number
Asm->EmitInt32(Unit.getStartOffset()); // Corresponding unit's offset
Asm->EmitInt8(AddressSize); // Address size
Asm->EmitInt8(0); // Segment size
Asm->OutStreamer.EmitFill(Padding, 0x0);
for (auto Range = Ranges.begin(), End = Ranges.end(); Range != End;
++Range) {
uint64_t RangeStart = Range->first;
MS->EmitIntValue(RangeStart, AddressSize);
while ((Range + 1) != End && Range->second == (Range + 1)->first)
++Range;
MS->EmitIntValue(Range->second - RangeStart, AddressSize);
}
// Emit terminator
Asm->OutStreamer.EmitIntValue(0, AddressSize);
Asm->OutStreamer.EmitIntValue(0, AddressSize);
Asm->OutStreamer.EmitLabel(EndLabel);
}
if (!DoDebugRanges)
return;
MS->SwitchSection(MC->getObjectFileInfo()->getDwarfRangesSection());
// Offset each range by the right amount.
int64_t PcOffset = -Unit.getLowPc();
// Emit coalesced ranges.
for (auto Range = Ranges.begin(), End = Ranges.end(); Range != End; ++Range) {
MS->EmitIntValue(Range->first + PcOffset, AddressSize);
while (Range + 1 != End && Range->second == (Range + 1)->first)
++Range;
MS->EmitIntValue(Range->second + PcOffset, AddressSize);
RangesSectionSize += 2 * AddressSize;
}
// Add the terminator entry.
MS->EmitIntValue(0, AddressSize);
MS->EmitIntValue(0, AddressSize);
RangesSectionSize += 2 * AddressSize;
}
/// \brief Emit location lists for \p Unit and update attribtues to
/// point to the new entries.
void DwarfStreamer::emitLocationsForUnit(const CompileUnit &Unit,
DWARFContext &Dwarf) {
const std::vector<std::pair<DIEInteger *, int64_t>> &Attributes =
Unit.getLocationAttributes();
if (Attributes.empty())
return;
MS->SwitchSection(MC->getObjectFileInfo()->getDwarfLocSection());
unsigned AddressSize = Unit.getOrigUnit().getAddressByteSize();
const DWARFSection &InputSec = Dwarf.getLocSection();
DataExtractor Data(InputSec.Data, Dwarf.isLittleEndian(), AddressSize);
DWARFUnit &OrigUnit = Unit.getOrigUnit();
const auto *OrigUnitDie = OrigUnit.getCompileUnitDIE(false);
int64_t UnitPcOffset = 0;
uint64_t OrigLowPc = OrigUnitDie->getAttributeValueAsAddress(
&OrigUnit, dwarf::DW_AT_low_pc, -1ULL);
if (OrigLowPc != -1ULL)
UnitPcOffset = int64_t(OrigLowPc) - Unit.getLowPc();
for (const auto &Attr : Attributes) {
uint32_t Offset = Attr.first->getValue();
Attr.first->setValue(LocSectionSize);
// This is the quantity to add to the old location address to get
// the correct address for the new one.
int64_t LocPcOffset = Attr.second + UnitPcOffset;
while (Data.isValidOffset(Offset)) {
uint64_t Low = Data.getUnsigned(&Offset, AddressSize);
uint64_t High = Data.getUnsigned(&Offset, AddressSize);
LocSectionSize += 2 * AddressSize;
if (Low == 0 && High == 0) {
Asm->OutStreamer.EmitIntValue(0, AddressSize);
Asm->OutStreamer.EmitIntValue(0, AddressSize);
break;
}
Asm->OutStreamer.EmitIntValue(Low + LocPcOffset, AddressSize);
Asm->OutStreamer.EmitIntValue(High + LocPcOffset, AddressSize);
uint64_t Length = Data.getU16(&Offset);
Asm->OutStreamer.EmitIntValue(Length, 2);
// Just copy the bytes over.
Asm->OutStreamer.EmitBytes(
StringRef(InputSec.Data.substr(Offset, Length)));
Offset += Length;
LocSectionSize += Length + 2;
}
}
}
/// \brief The core of the Dwarf linking logic.
///
/// The link of the dwarf information from the object files will be
/// driven by the selection of 'root DIEs', which are DIEs that
/// describe variables or functions that are present in the linked
/// binary (and thus have entries in the debug map). All the debug
/// information that will be linked (the DIEs, but also the line
/// tables, ranges, ...) is derived from that set of root DIEs.
///
/// The root DIEs are identified because they contain relocations that
/// correspond to a debug map entry at specific places (the low_pc for
/// a function, the location for a variable). These relocations are
/// called ValidRelocs in the DwarfLinker and are gathered as a very
/// first step when we start processing a DebugMapObject.
class DwarfLinker {
public:
DwarfLinker(StringRef OutputFilename, const LinkOptions &Options)
: OutputFilename(OutputFilename), Options(Options),
BinHolder(Options.Verbose) {}
~DwarfLinker() {
for (auto *Abbrev : Abbreviations)
delete Abbrev;
}
/// \brief Link the contents of the DebugMap.
bool link(const DebugMap &);
private:
/// \brief Called at the start of a debug object link.
void startDebugObject(DWARFContext &);
/// \brief Called at the end of a debug object link.
void endDebugObject();
/// \defgroup FindValidRelocations Translate debug map into a list
/// of relevant relocations
///
/// @{
struct ValidReloc {
uint32_t Offset;
uint32_t Size;
uint64_t Addend;
const DebugMapObject::DebugMapEntry *Mapping;
ValidReloc(uint32_t Offset, uint32_t Size, uint64_t Addend,
const DebugMapObject::DebugMapEntry *Mapping)
: Offset(Offset), Size(Size), Addend(Addend), Mapping(Mapping) {}
bool operator<(const ValidReloc &RHS) const { return Offset < RHS.Offset; }
};
/// \brief The valid relocations for the current DebugMapObject.
/// This vector is sorted by relocation offset.
std::vector<ValidReloc> ValidRelocs;
/// \brief Index into ValidRelocs of the next relocation to
/// consider. As we walk the DIEs in acsending file offset and as
/// ValidRelocs is sorted by file offset, keeping this index
/// uptodate is all we have to do to have a cheap lookup during the
/// root DIE selection and during DIE cloning.
unsigned NextValidReloc;
bool findValidRelocsInDebugInfo(const object::ObjectFile &Obj,
const DebugMapObject &DMO);
bool findValidRelocs(const object::SectionRef &Section,
const object::ObjectFile &Obj,
const DebugMapObject &DMO);
void findValidRelocsMachO(const object::SectionRef &Section,
const object::MachOObjectFile &Obj,
const DebugMapObject &DMO);
/// @}
/// \defgroup FindRootDIEs Find DIEs corresponding to debug map entries.
///
/// @{
/// \brief Recursively walk the \p DIE tree and look for DIEs to
/// keep. Store that information in \p CU's DIEInfo.
void lookForDIEsToKeep(const DWARFDebugInfoEntryMinimal &DIE,
const DebugMapObject &DMO, CompileUnit &CU,
unsigned Flags);
/// \brief Flags passed to DwarfLinker::lookForDIEsToKeep
enum TravesalFlags {
TF_Keep = 1 << 0, ///< Mark the traversed DIEs as kept.
TF_InFunctionScope = 1 << 1, ///< Current scope is a fucntion scope.
TF_DependencyWalk = 1 << 2, ///< Walking the dependencies of a kept DIE.
TF_ParentWalk = 1 << 3, ///< Walking up the parents of a kept DIE.
};
/// \brief Mark the passed DIE as well as all the ones it depends on
/// as kept.
void keepDIEAndDenpendencies(const DWARFDebugInfoEntryMinimal &DIE,
CompileUnit::DIEInfo &MyInfo,
const DebugMapObject &DMO, CompileUnit &CU,
unsigned Flags);
unsigned shouldKeepDIE(const DWARFDebugInfoEntryMinimal &DIE,
CompileUnit &Unit, CompileUnit::DIEInfo &MyInfo,
unsigned Flags);
unsigned shouldKeepVariableDIE(const DWARFDebugInfoEntryMinimal &DIE,
CompileUnit &Unit,
CompileUnit::DIEInfo &MyInfo, unsigned Flags);
unsigned shouldKeepSubprogramDIE(const DWARFDebugInfoEntryMinimal &DIE,
CompileUnit &Unit,
CompileUnit::DIEInfo &MyInfo,
unsigned Flags);
bool hasValidRelocation(uint32_t StartOffset, uint32_t EndOffset,
CompileUnit::DIEInfo &Info);
/// @}
/// \defgroup Linking Methods used to link the debug information
///
/// @{
/// \brief Recursively clone \p InputDIE into an tree of DIE objects
/// where useless (as decided by lookForDIEsToKeep()) bits have been
/// stripped out and addresses have been rewritten according to the
/// debug map.
///
/// \param OutOffset is the offset the cloned DIE in the output
/// compile unit.
/// \param PCOffset (while cloning a function scope) is the offset
/// applied to the entry point of the function to get the linked address.
///
/// \returns the root of the cloned tree.
DIE *cloneDIE(const DWARFDebugInfoEntryMinimal &InputDIE, CompileUnit &U,
int64_t PCOffset, uint32_t OutOffset);
typedef DWARFAbbreviationDeclaration::AttributeSpec AttributeSpec;
/// \brief Information gathered and exchanged between the various
/// clone*Attributes helpers about the attributes of a particular DIE.
struct AttributesInfo {
uint64_t OrigHighPc; ///< Value of AT_high_pc in the input DIE
int64_t PCOffset; ///< Offset to apply to PC addresses inside a function.
AttributesInfo() : OrigHighPc(0), PCOffset(0) {}
};
/// \brief Helper for cloneDIE.
unsigned cloneAttribute(DIE &Die, const DWARFDebugInfoEntryMinimal &InputDIE,
CompileUnit &U, const DWARFFormValue &Val,
const AttributeSpec AttrSpec, unsigned AttrSize,
AttributesInfo &AttrInfo);
/// \brief Helper for cloneDIE.
unsigned cloneStringAttribute(DIE &Die, AttributeSpec AttrSpec,
const DWARFFormValue &Val, const DWARFUnit &U);
/// \brief Helper for cloneDIE.
unsigned
cloneDieReferenceAttribute(DIE &Die,
const DWARFDebugInfoEntryMinimal &InputDIE,
AttributeSpec AttrSpec, unsigned AttrSize,
const DWARFFormValue &Val, CompileUnit &Unit);
/// \brief Helper for cloneDIE.
unsigned cloneBlockAttribute(DIE &Die, AttributeSpec AttrSpec,
const DWARFFormValue &Val, unsigned AttrSize);
/// \brief Helper for cloneDIE.
unsigned cloneAddressAttribute(DIE &Die, AttributeSpec AttrSpec,
const DWARFFormValue &Val,
const CompileUnit &Unit, AttributesInfo &Info);
/// \brief Helper for cloneDIE.
unsigned cloneScalarAttribute(DIE &Die,
const DWARFDebugInfoEntryMinimal &InputDIE,
CompileUnit &U, AttributeSpec AttrSpec,
const DWARFFormValue &Val, unsigned AttrSize,
const AttributesInfo &Info);
/// \brief Helper for cloneDIE.
bool applyValidRelocs(MutableArrayRef<char> Data, uint32_t BaseOffset,
bool isLittleEndian);
/// \brief Assign an abbreviation number to \p Abbrev
void AssignAbbrev(DIEAbbrev &Abbrev);
/// \brief FoldingSet that uniques the abbreviations.
FoldingSet<DIEAbbrev> AbbreviationsSet;
/// \brief Storage for the unique Abbreviations.
/// This is passed to AsmPrinter::emitDwarfAbbrevs(), thus it cannot
/// be changed to a vecot of unique_ptrs.
std::vector<DIEAbbrev *> Abbreviations;
/// \brief Compute and emit debug_ranges section for \p Unit, and
/// patch the attributes referencing it.
void patchRangesForUnit(const CompileUnit &Unit, DWARFContext &Dwarf) const;
/// \brief Generate and emit the DW_AT_ranges attribute for a
/// compile_unit if it had one.
void generateUnitRanges(CompileUnit &Unit) const;
/// \brief DIELoc objects that need to be destructed (but not freed!).
std::vector<DIELoc *> DIELocs;
/// \brief DIEBlock objects that need to be destructed (but not freed!).
std::vector<DIEBlock *> DIEBlocks;
/// \brief Allocator used for all the DIEValue objects.
BumpPtrAllocator DIEAlloc;
/// @}
/// \defgroup Helpers Various helper methods.
///
/// @{
const DWARFDebugInfoEntryMinimal *
resolveDIEReference(DWARFFormValue &RefValue, const DWARFUnit &Unit,
const DWARFDebugInfoEntryMinimal &DIE,
CompileUnit *&ReferencedCU);
CompileUnit *getUnitForOffset(unsigned Offset);
void reportWarning(const Twine &Warning, const DWARFUnit *Unit = nullptr,
const DWARFDebugInfoEntryMinimal *DIE = nullptr) const;
bool createStreamer(Triple TheTriple, StringRef OutputFilename);
/// @}
private:
std::string OutputFilename;
LinkOptions Options;
BinaryHolder BinHolder;
std::unique_ptr<DwarfStreamer> Streamer;
/// The units of the current debug map object.
std::vector<CompileUnit> Units;
/// The debug map object curently under consideration.
DebugMapObject *CurrentDebugObject;
/// \brief The Dwarf string pool
NonRelocatableStringpool StringPool;
};
/// \brief Similar to DWARFUnitSection::getUnitForOffset(), but
/// returning our CompileUnit object instead.
CompileUnit *DwarfLinker::getUnitForOffset(unsigned Offset) {
auto CU =
std::upper_bound(Units.begin(), Units.end(), Offset,
[](uint32_t LHS, const CompileUnit &RHS) {
return LHS < RHS.getOrigUnit().getNextUnitOffset();
});
return CU != Units.end() ? &*CU : nullptr;
}
/// \brief Resolve the DIE attribute reference that has been
/// extracted in \p RefValue. The resulting DIE migh be in another
/// CompileUnit which is stored into \p ReferencedCU.
/// \returns null if resolving fails for any reason.
const DWARFDebugInfoEntryMinimal *DwarfLinker::resolveDIEReference(
DWARFFormValue &RefValue, const DWARFUnit &Unit,
const DWARFDebugInfoEntryMinimal &DIE, CompileUnit *&RefCU) {
assert(RefValue.isFormClass(DWARFFormValue::FC_Reference));
uint64_t RefOffset = *RefValue.getAsReference(&Unit);
if ((RefCU = getUnitForOffset(RefOffset)))
if (const auto *RefDie = RefCU->getOrigUnit().getDIEForOffset(RefOffset))
return RefDie;
reportWarning("could not find referenced DIE", &Unit, &DIE);
return nullptr;
}
/// \brief Report a warning to the user, optionaly including
/// information about a specific \p DIE related to the warning.
void DwarfLinker::reportWarning(const Twine &Warning, const DWARFUnit *Unit,
const DWARFDebugInfoEntryMinimal *DIE) const {
StringRef Context = "<debug map>";
if (CurrentDebugObject)
Context = CurrentDebugObject->getObjectFilename();
warn(Warning, Context);
if (!Options.Verbose || !DIE)
return;
errs() << " in DIE:\n";
DIE->dump(errs(), const_cast<DWARFUnit *>(Unit), 0 /* RecurseDepth */,
6 /* Indent */);
}
bool DwarfLinker::createStreamer(Triple TheTriple, StringRef OutputFilename) {
if (Options.NoOutput)
return true;
Streamer = llvm::make_unique<DwarfStreamer>();
return Streamer->init(TheTriple, OutputFilename);
}
/// \brief Recursive helper to gather the child->parent relationships in the
/// original compile unit.
static void gatherDIEParents(const DWARFDebugInfoEntryMinimal *DIE,
unsigned ParentIdx, CompileUnit &CU) {
unsigned MyIdx = CU.getOrigUnit().getDIEIndex(DIE);
CU.getInfo(MyIdx).ParentIdx = ParentIdx;
if (DIE->hasChildren())
for (auto *Child = DIE->getFirstChild(); Child && !Child->isNULL();
Child = Child->getSibling())
gatherDIEParents(Child, MyIdx, CU);
}
static bool dieNeedsChildrenToBeMeaningful(uint32_t Tag) {
switch (Tag) {
default:
return false;
case dwarf::DW_TAG_subprogram:
case dwarf::DW_TAG_lexical_block:
case dwarf::DW_TAG_subroutine_type:
case dwarf::DW_TAG_structure_type:
case dwarf::DW_TAG_class_type:
case dwarf::DW_TAG_union_type:
return true;
}
llvm_unreachable("Invalid Tag");
}
void DwarfLinker::startDebugObject(DWARFContext &Dwarf) {
Units.reserve(Dwarf.getNumCompileUnits());
NextValidReloc = 0;
}
void DwarfLinker::endDebugObject() {
Units.clear();
ValidRelocs.clear();
for (auto *Block : DIEBlocks)
Block->~DIEBlock();
for (auto *Loc : DIELocs)
Loc->~DIELoc();
DIEBlocks.clear();
DIELocs.clear();
DIEAlloc.Reset();
}
/// \brief Iterate over the relocations of the given \p Section and
/// store the ones that correspond to debug map entries into the
/// ValidRelocs array.
void DwarfLinker::findValidRelocsMachO(const object::SectionRef &Section,
const object::MachOObjectFile &Obj,
const DebugMapObject &DMO) {
StringRef Contents;
Section.getContents(Contents);
DataExtractor Data(Contents, Obj.isLittleEndian(), 0);
for (const object::RelocationRef &Reloc : Section.relocations()) {
object::DataRefImpl RelocDataRef = Reloc.getRawDataRefImpl();
MachO::any_relocation_info MachOReloc = Obj.getRelocation(RelocDataRef);
unsigned RelocSize = 1 << Obj.getAnyRelocationLength(MachOReloc);
uint64_t Offset64;
if ((RelocSize != 4 && RelocSize != 8) || Reloc.getOffset(Offset64)) {
reportWarning(" unsupported relocation in debug_info section.");
continue;
}
uint32_t Offset = Offset64;
// Mach-o uses REL relocations, the addend is at the relocation offset.
uint64_t Addend = Data.getUnsigned(&Offset, RelocSize);
auto Sym = Reloc.getSymbol();
if (Sym != Obj.symbol_end()) {
StringRef SymbolName;
if (Sym->getName(SymbolName)) {
reportWarning("error getting relocation symbol name.");
continue;
}
if (const auto *Mapping = DMO.lookupSymbol(SymbolName))
ValidRelocs.emplace_back(Offset64, RelocSize, Addend, Mapping);
} else if (const auto *Mapping = DMO.lookupObjectAddress(Addend)) {
// Do not store the addend. The addend was the address of the
// symbol in the object file, the address in the binary that is
// stored in the debug map doesn't need to be offseted.
ValidRelocs.emplace_back(Offset64, RelocSize, 0, Mapping);
}
}
}
/// \brief Dispatch the valid relocation finding logic to the
/// appropriate handler depending on the object file format.
bool DwarfLinker::findValidRelocs(const object::SectionRef &Section,
const object::ObjectFile &Obj,
const DebugMapObject &DMO) {
// Dispatch to the right handler depending on the file type.
if (auto *MachOObj = dyn_cast<object::MachOObjectFile>(&Obj))
findValidRelocsMachO(Section, *MachOObj, DMO);
else
reportWarning(Twine("unsupported object file type: ") + Obj.getFileName());
if (ValidRelocs.empty())
return false;
// Sort the relocations by offset. We will walk the DIEs linearly in
// the file, this allows us to just keep an index in the relocation
// array that we advance during our walk, rather than resorting to
// some associative container. See DwarfLinker::NextValidReloc.
std::sort(ValidRelocs.begin(), ValidRelocs.end());
return true;
}
/// \brief Look for relocations in the debug_info section that match
/// entries in the debug map. These relocations will drive the Dwarf
/// link by indicating which DIEs refer to symbols present in the
/// linked binary.
/// \returns wether there are any valid relocations in the debug info.
bool DwarfLinker::findValidRelocsInDebugInfo(const object::ObjectFile &Obj,
const DebugMapObject &DMO) {
// Find the debug_info section.
for (const object::SectionRef &Section : Obj.sections()) {
StringRef SectionName;
Section.getName(SectionName);
SectionName = SectionName.substr(SectionName.find_first_not_of("._"));
if (SectionName != "debug_info")
continue;
return findValidRelocs(Section, Obj, DMO);
}
return false;
}
/// \brief Checks that there is a relocation against an actual debug
/// map entry between \p StartOffset and \p NextOffset.
///
/// This function must be called with offsets in strictly ascending
/// order because it never looks back at relocations it already 'went past'.
/// \returns true and sets Info.InDebugMap if it is the case.
bool DwarfLinker::hasValidRelocation(uint32_t StartOffset, uint32_t EndOffset,
CompileUnit::DIEInfo &Info) {
assert(NextValidReloc == 0 ||
StartOffset > ValidRelocs[NextValidReloc - 1].Offset);
if (NextValidReloc >= ValidRelocs.size())
return false;
uint64_t RelocOffset = ValidRelocs[NextValidReloc].Offset;
// We might need to skip some relocs that we didn't consider. For
// example the high_pc of a discarded DIE might contain a reloc that
// is in the list because it actually corresponds to the start of a
// function that is in the debug map.
while (RelocOffset < StartOffset && NextValidReloc < ValidRelocs.size() - 1)
RelocOffset = ValidRelocs[++NextValidReloc].Offset;
if (RelocOffset < StartOffset || RelocOffset >= EndOffset)
return false;
const auto &ValidReloc = ValidRelocs[NextValidReloc++];
if (Options.Verbose)
outs() << "Found valid debug map entry: " << ValidReloc.Mapping->getKey()
<< " " << format("\t%016" PRIx64 " => %016" PRIx64,
ValidReloc.Mapping->getValue().ObjectAddress,
ValidReloc.Mapping->getValue().BinaryAddress);
Info.AddrAdjust = int64_t(ValidReloc.Mapping->getValue().BinaryAddress) +
ValidReloc.Addend -
ValidReloc.Mapping->getValue().ObjectAddress;
Info.InDebugMap = true;
return true;
}
/// \brief Get the starting and ending (exclusive) offset for the
/// attribute with index \p Idx descibed by \p Abbrev. \p Offset is
/// supposed to point to the position of the first attribute described
/// by \p Abbrev.
/// \return [StartOffset, EndOffset) as a pair.
static std::pair<uint32_t, uint32_t>
getAttributeOffsets(const DWARFAbbreviationDeclaration *Abbrev, unsigned Idx,
unsigned Offset, const DWARFUnit &Unit) {
DataExtractor Data = Unit.getDebugInfoExtractor();
for (unsigned i = 0; i < Idx; ++i)
DWARFFormValue::skipValue(Abbrev->getFormByIndex(i), Data, &Offset, &Unit);
uint32_t End = Offset;
DWARFFormValue::skipValue(Abbrev->getFormByIndex(Idx), Data, &End, &Unit);
return std::make_pair(Offset, End);
}
/// \brief Check if a variable describing DIE should be kept.
/// \returns updated TraversalFlags.
unsigned DwarfLinker::shouldKeepVariableDIE(
const DWARFDebugInfoEntryMinimal &DIE, CompileUnit &Unit,
CompileUnit::DIEInfo &MyInfo, unsigned Flags) {
const auto *Abbrev = DIE.getAbbreviationDeclarationPtr();
// Global variables with constant value can always be kept.
if (!(Flags & TF_InFunctionScope) &&
Abbrev->findAttributeIndex(dwarf::DW_AT_const_value) != -1U) {
MyInfo.InDebugMap = true;
return Flags | TF_Keep;
}
uint32_t LocationIdx = Abbrev->findAttributeIndex(dwarf::DW_AT_location);
if (LocationIdx == -1U)
return Flags;
uint32_t Offset = DIE.getOffset() + getULEB128Size(Abbrev->getCode());
const DWARFUnit &OrigUnit = Unit.getOrigUnit();
uint32_t LocationOffset, LocationEndOffset;
std::tie(LocationOffset, LocationEndOffset) =
getAttributeOffsets(Abbrev, LocationIdx, Offset, OrigUnit);
// See if there is a relocation to a valid debug map entry inside
// this variable's location. The order is important here. We want to
// always check in the variable has a valid relocation, so that the
// DIEInfo is filled. However, we don't want a static variable in a
// function to force us to keep the enclosing function.
if (!hasValidRelocation(LocationOffset, LocationEndOffset, MyInfo) ||
(Flags & TF_InFunctionScope))
return Flags;
if (Options.Verbose)
DIE.dump(outs(), const_cast<DWARFUnit *>(&OrigUnit), 0, 8 /* Indent */);
return Flags | TF_Keep;
}
/// \brief Check if a function describing DIE should be kept.
/// \returns updated TraversalFlags.
unsigned DwarfLinker::shouldKeepSubprogramDIE(
const DWARFDebugInfoEntryMinimal &DIE, CompileUnit &Unit,
CompileUnit::DIEInfo &MyInfo, unsigned Flags) {
const auto *Abbrev = DIE.getAbbreviationDeclarationPtr();
Flags |= TF_InFunctionScope;
uint32_t LowPcIdx = Abbrev->findAttributeIndex(dwarf::DW_AT_low_pc);
if (LowPcIdx == -1U)
return Flags;
uint32_t Offset = DIE.getOffset() + getULEB128Size(Abbrev->getCode());
const DWARFUnit &OrigUnit = Unit.getOrigUnit();
uint32_t LowPcOffset, LowPcEndOffset;
std::tie(LowPcOffset, LowPcEndOffset) =
getAttributeOffsets(Abbrev, LowPcIdx, Offset, OrigUnit);
uint64_t LowPc =
DIE.getAttributeValueAsAddress(&OrigUnit, dwarf::DW_AT_low_pc, -1ULL);
assert(LowPc != -1ULL && "low_pc attribute is not an address.");
if (LowPc == -1ULL ||
!hasValidRelocation(LowPcOffset, LowPcEndOffset, MyInfo))
return Flags;
if (Options.Verbose)
DIE.dump(outs(), const_cast<DWARFUnit *>(&OrigUnit), 0, 8 /* Indent */);
Flags |= TF_Keep;
DWARFFormValue HighPcValue;
if (!DIE.getAttributeValue(&OrigUnit, dwarf::DW_AT_high_pc, HighPcValue)) {
reportWarning("Function without high_pc. Range will be discarded.\n",
&OrigUnit, &DIE);
return Flags;
}
uint64_t HighPc;
if (HighPcValue.isFormClass(DWARFFormValue::FC_Address)) {
HighPc = *HighPcValue.getAsAddress(&OrigUnit);
} else {
assert(HighPcValue.isFormClass(DWARFFormValue::FC_Constant));
HighPc = LowPc + *HighPcValue.getAsUnsignedConstant();
}
Unit.addFunctionRange(LowPc, HighPc, MyInfo.AddrAdjust);
return Flags;
}
/// \brief Check if a DIE should be kept.
/// \returns updated TraversalFlags.
unsigned DwarfLinker::shouldKeepDIE(const DWARFDebugInfoEntryMinimal &DIE,
CompileUnit &Unit,
CompileUnit::DIEInfo &MyInfo,
unsigned Flags) {
switch (DIE.getTag()) {
case dwarf::DW_TAG_constant:
case dwarf::DW_TAG_variable:
return shouldKeepVariableDIE(DIE, Unit, MyInfo, Flags);
case dwarf::DW_TAG_subprogram:
return shouldKeepSubprogramDIE(DIE, Unit, MyInfo, Flags);
case dwarf::DW_TAG_module:
case dwarf::DW_TAG_imported_module:
case dwarf::DW_TAG_imported_declaration:
case dwarf::DW_TAG_imported_unit:
// We always want to keep these.
return Flags | TF_Keep;
}
return Flags;
}
/// \brief Mark the passed DIE as well as all the ones it depends on
/// as kept.
///
/// This function is called by lookForDIEsToKeep on DIEs that are
/// newly discovered to be needed in the link. It recursively calls
/// back to lookForDIEsToKeep while adding TF_DependencyWalk to the
/// TraversalFlags to inform it that it's not doing the primary DIE
/// tree walk.
void DwarfLinker::keepDIEAndDenpendencies(const DWARFDebugInfoEntryMinimal &DIE,
CompileUnit::DIEInfo &MyInfo,
const DebugMapObject &DMO,
CompileUnit &CU, unsigned Flags) {
const DWARFUnit &Unit = CU.getOrigUnit();
MyInfo.Keep = true;
// First mark all the parent chain as kept.
unsigned AncestorIdx = MyInfo.ParentIdx;
while (!CU.getInfo(AncestorIdx).Keep) {
lookForDIEsToKeep(*Unit.getDIEAtIndex(AncestorIdx), DMO, CU,
TF_ParentWalk | TF_Keep | TF_DependencyWalk);
AncestorIdx = CU.getInfo(AncestorIdx).ParentIdx;
}
// Then we need to mark all the DIEs referenced by this DIE's
// attributes as kept.
DataExtractor Data = Unit.getDebugInfoExtractor();
const auto *Abbrev = DIE.getAbbreviationDeclarationPtr();
uint32_t Offset = DIE.getOffset() + getULEB128Size(Abbrev->getCode());
// Mark all DIEs referenced through atttributes as kept.
for (const auto &AttrSpec : Abbrev->attributes()) {
DWARFFormValue Val(AttrSpec.Form);
if (!Val.isFormClass(DWARFFormValue::FC_Reference)) {
DWARFFormValue::skipValue(AttrSpec.Form, Data, &Offset, &Unit);
continue;
}
Val.extractValue(Data, &Offset, &Unit);
CompileUnit *ReferencedCU;
if (const auto *RefDIE = resolveDIEReference(Val, Unit, DIE, ReferencedCU))
lookForDIEsToKeep(*RefDIE, DMO, *ReferencedCU,
TF_Keep | TF_DependencyWalk);
}
}
/// \brief Recursively walk the \p DIE tree and look for DIEs to
/// keep. Store that information in \p CU's DIEInfo.
///
/// This function is the entry point of the DIE selection
/// algorithm. It is expected to walk the DIE tree in file order and
/// (though the mediation of its helper) call hasValidRelocation() on
/// each DIE that might be a 'root DIE' (See DwarfLinker class
/// comment).
/// While walking the dependencies of root DIEs, this function is
/// also called, but during these dependency walks the file order is
/// not respected. The TF_DependencyWalk flag tells us which kind of
/// traversal we are currently doing.
void DwarfLinker::lookForDIEsToKeep(const DWARFDebugInfoEntryMinimal &DIE,
const DebugMapObject &DMO, CompileUnit &CU,
unsigned Flags) {
unsigned Idx = CU.getOrigUnit().getDIEIndex(&DIE);
CompileUnit::DIEInfo &MyInfo = CU.getInfo(Idx);
bool AlreadyKept = MyInfo.Keep;
// If the Keep flag is set, we are marking a required DIE's
// dependencies. If our target is already marked as kept, we're all
// set.
if ((Flags & TF_DependencyWalk) && AlreadyKept)
return;
// We must not call shouldKeepDIE while called from keepDIEAndDenpendencies,
// because it would screw up the relocation finding logic.
if (!(Flags & TF_DependencyWalk))
Flags = shouldKeepDIE(DIE, CU, MyInfo, Flags);
// If it is a newly kept DIE mark it as well as all its dependencies as kept.
if (!AlreadyKept && (Flags & TF_Keep))
keepDIEAndDenpendencies(DIE, MyInfo, DMO, CU, Flags);
// The TF_ParentWalk flag tells us that we are currently walking up
// the parent chain of a required DIE, and we don't want to mark all
// the children of the parents as kept (consider for example a
// DW_TAG_namespace node in the parent chain). There are however a
// set of DIE types for which we want to ignore that directive and still
// walk their children.
if (dieNeedsChildrenToBeMeaningful(DIE.getTag()))
Flags &= ~TF_ParentWalk;
if (!DIE.hasChildren() || (Flags & TF_ParentWalk))
return;
for (auto *Child = DIE.getFirstChild(); Child && !Child->isNULL();
Child = Child->getSibling())
lookForDIEsToKeep(*Child, DMO, CU, Flags);
}
/// \brief Assign an abbreviation numer to \p Abbrev.
///
/// Our DIEs get freed after every DebugMapObject has been processed,
/// thus the FoldingSet we use to unique DIEAbbrevs cannot refer to
/// the instances hold by the DIEs. When we encounter an abbreviation
/// that we don't know, we create a permanent copy of it.
void DwarfLinker::AssignAbbrev(DIEAbbrev &Abbrev) {
// Check the set for priors.
FoldingSetNodeID ID;
Abbrev.Profile(ID);
void *InsertToken;
DIEAbbrev *InSet = AbbreviationsSet.FindNodeOrInsertPos(ID, InsertToken);
// If it's newly added.
if (InSet) {
// Assign existing abbreviation number.
Abbrev.setNumber(InSet->getNumber());
} else {
// Add to abbreviation list.
Abbreviations.push_back(
new DIEAbbrev(Abbrev.getTag(), Abbrev.hasChildren()));
for (const auto &Attr : Abbrev.getData())
Abbreviations.back()->AddAttribute(Attr.getAttribute(), Attr.getForm());
AbbreviationsSet.InsertNode(Abbreviations.back(), InsertToken);
// Assign the unique abbreviation number.
Abbrev.setNumber(Abbreviations.size());
Abbreviations.back()->setNumber(Abbreviations.size());
}
}
/// \brief Clone a string attribute described by \p AttrSpec and add
/// it to \p Die.
/// \returns the size of the new attribute.
unsigned DwarfLinker::cloneStringAttribute(DIE &Die, AttributeSpec AttrSpec,
const DWARFFormValue &Val,
const DWARFUnit &U) {
// Switch everything to out of line strings.
const char *String = *Val.getAsCString(&U);
unsigned Offset = StringPool.getStringOffset(String);
Die.addValue(dwarf::Attribute(AttrSpec.Attr), dwarf::DW_FORM_strp,
new (DIEAlloc) DIEInteger(Offset));
return 4;
}
/// \brief Clone an attribute referencing another DIE and add
/// it to \p Die.
/// \returns the size of the new attribute.
unsigned DwarfLinker::cloneDieReferenceAttribute(
DIE &Die, const DWARFDebugInfoEntryMinimal &InputDIE,
AttributeSpec AttrSpec, unsigned AttrSize, const DWARFFormValue &Val,
CompileUnit &Unit) {
uint32_t Ref = *Val.getAsReference(&Unit.getOrigUnit());
DIE *NewRefDie = nullptr;
CompileUnit *RefUnit = nullptr;
const DWARFDebugInfoEntryMinimal *RefDie = nullptr;
if (!(RefUnit = getUnitForOffset(Ref)) ||
!(RefDie = RefUnit->getOrigUnit().getDIEForOffset(Ref))) {
const char *AttributeString = dwarf::AttributeString(AttrSpec.Attr);
if (!AttributeString)
AttributeString = "DW_AT_???";
reportWarning(Twine("Missing DIE for ref in attribute ") + AttributeString +
". Dropping.",
&Unit.getOrigUnit(), &InputDIE);
return 0;
}
unsigned Idx = RefUnit->getOrigUnit().getDIEIndex(RefDie);
CompileUnit::DIEInfo &RefInfo = RefUnit->getInfo(Idx);
if (!RefInfo.Clone) {
assert(Ref > InputDIE.getOffset());
// We haven't cloned this DIE yet. Just create an empty one and
// store it. It'll get really cloned when we process it.
RefInfo.Clone = new DIE(dwarf::Tag(RefDie->getTag()));
}
NewRefDie = RefInfo.Clone;
if (AttrSpec.Form == dwarf::DW_FORM_ref_addr) {
// We cannot currently rely on a DIEEntry to emit ref_addr
// references, because the implementation calls back to DwarfDebug
// to find the unit offset. (We don't have a DwarfDebug)
// FIXME: we should be able to design DIEEntry reliance on
// DwarfDebug away.
DIEInteger *Attr;
if (Ref < InputDIE.getOffset()) {
// We must have already cloned that DIE.
uint32_t NewRefOffset =
RefUnit->getStartOffset() + NewRefDie->getOffset();
Attr = new (DIEAlloc) DIEInteger(NewRefOffset);
} else {
// A forward reference. Note and fixup later.
Attr = new (DIEAlloc) DIEInteger(0xBADDEF);
Unit.noteForwardReference(NewRefDie, RefUnit, Attr);
}
Die.addValue(dwarf::Attribute(AttrSpec.Attr), dwarf::DW_FORM_ref_addr,
Attr);
return AttrSize;
}
Die.addValue(dwarf::Attribute(AttrSpec.Attr), dwarf::Form(AttrSpec.Form),
new (DIEAlloc) DIEEntry(*NewRefDie));
return AttrSize;
}
/// \brief Clone an attribute of block form (locations, constants) and add
/// it to \p Die.
/// \returns the size of the new attribute.
unsigned DwarfLinker::cloneBlockAttribute(DIE &Die, AttributeSpec AttrSpec,
const DWARFFormValue &Val,
unsigned AttrSize) {
DIE *Attr;
DIEValue *Value;
DIELoc *Loc = nullptr;
DIEBlock *Block = nullptr;
// Just copy the block data over.
if (AttrSpec.Form == dwarf::DW_FORM_exprloc) {
Loc = new (DIEAlloc) DIELoc();
DIELocs.push_back(Loc);
} else {
Block = new (DIEAlloc) DIEBlock();
DIEBlocks.push_back(Block);
}
Attr = Loc ? static_cast<DIE *>(Loc) : static_cast<DIE *>(Block);
Value = Loc ? static_cast<DIEValue *>(Loc) : static_cast<DIEValue *>(Block);
ArrayRef<uint8_t> Bytes = *Val.getAsBlock();
for (auto Byte : Bytes)
Attr->addValue(static_cast<dwarf::Attribute>(0), dwarf::DW_FORM_data1,
new (DIEAlloc) DIEInteger(Byte));
// FIXME: If DIEBlock and DIELoc just reuses the Size field of
// the DIE class, this if could be replaced by
// Attr->setSize(Bytes.size()).
if (Streamer) {
if (Loc)
Loc->ComputeSize(&Streamer->getAsmPrinter());
else
Block->ComputeSize(&Streamer->getAsmPrinter());
}
Die.addValue(dwarf::Attribute(AttrSpec.Attr), dwarf::Form(AttrSpec.Form),
Value);
return AttrSize;
}
/// \brief Clone an address attribute and add it to \p Die.
/// \returns the size of the new attribute.
unsigned DwarfLinker::cloneAddressAttribute(DIE &Die, AttributeSpec AttrSpec,
const DWARFFormValue &Val,
const CompileUnit &Unit,
AttributesInfo &Info) {
uint64_t Addr = *Val.getAsAddress(&Unit.getOrigUnit());
if (AttrSpec.Attr == dwarf::DW_AT_low_pc) {
if (Die.getTag() == dwarf::DW_TAG_inlined_subroutine ||
Die.getTag() == dwarf::DW_TAG_lexical_block)
Addr += Info.PCOffset;
else if (Die.getTag() == dwarf::DW_TAG_compile_unit) {
Addr = Unit.getLowPc();
if (Addr == UINT64_MAX)
return 0;
}
} else if (AttrSpec.Attr == dwarf::DW_AT_high_pc) {
if (Die.getTag() == dwarf::DW_TAG_compile_unit) {
if (uint64_t HighPc = Unit.getHighPc())
Addr = HighPc;
else
return 0;
} else
// If we have a high_pc recorded for the input DIE, use
// it. Otherwise (when no relocations where applied) just use the
// one we just decoded.
Addr = (Info.OrigHighPc ? Info.OrigHighPc : Addr) + Info.PCOffset;
}
Die.addValue(static_cast<dwarf::Attribute>(AttrSpec.Attr),
static_cast<dwarf::Form>(AttrSpec.Form),
new (DIEAlloc) DIEInteger(Addr));
return Unit.getOrigUnit().getAddressByteSize();
}
/// \brief Clone a scalar attribute and add it to \p Die.
/// \returns the size of the new attribute.
unsigned DwarfLinker::cloneScalarAttribute(
DIE &Die, const DWARFDebugInfoEntryMinimal &InputDIE, CompileUnit &Unit,
AttributeSpec AttrSpec, const DWARFFormValue &Val, unsigned AttrSize,
const AttributesInfo &Info) {
uint64_t Value;
if (AttrSpec.Attr == dwarf::DW_AT_high_pc &&
Die.getTag() == dwarf::DW_TAG_compile_unit) {
if (Unit.getLowPc() == -1ULL)
return 0;
// Dwarf >= 4 high_pc is an size, not an address.
Value = Unit.getHighPc() - Unit.getLowPc();
} else if (AttrSpec.Form == dwarf::DW_FORM_sec_offset)
Value = *Val.getAsSectionOffset();
else if (AttrSpec.Form == dwarf::DW_FORM_sdata)
Value = *Val.getAsSignedConstant();
else if (auto OptionalValue = Val.getAsUnsignedConstant())
Value = *OptionalValue;
else {
reportWarning("Unsupported scalar attribute form. Dropping attribute.",
&Unit.getOrigUnit(), &InputDIE);
return 0;
}
DIEInteger *Attr = new (DIEAlloc) DIEInteger(Value);
if (AttrSpec.Attr == dwarf::DW_AT_ranges)
Unit.noteRangeAttribute(Die, Attr);
// A more generic way to check for location attributes would be
// nice, but it's very unlikely that any other attribute needs a
// location list.
else if (AttrSpec.Attr == dwarf::DW_AT_location ||
AttrSpec.Attr == dwarf::DW_AT_frame_base)
Unit.noteLocationAttribute(Attr, Info.PCOffset);
Die.addValue(dwarf::Attribute(AttrSpec.Attr), dwarf::Form(AttrSpec.Form),
Attr);
return AttrSize;
}
/// \brief Clone \p InputDIE's attribute described by \p AttrSpec with
/// value \p Val, and add it to \p Die.
/// \returns the size of the cloned attribute.
unsigned DwarfLinker::cloneAttribute(DIE &Die,
const DWARFDebugInfoEntryMinimal &InputDIE,
CompileUnit &Unit,
const DWARFFormValue &Val,
const AttributeSpec AttrSpec,
unsigned AttrSize, AttributesInfo &Info) {
const DWARFUnit &U = Unit.getOrigUnit();
switch (AttrSpec.Form) {
case dwarf::DW_FORM_strp:
case dwarf::DW_FORM_string:
return cloneStringAttribute(Die, AttrSpec, Val, U);
case dwarf::DW_FORM_ref_addr:
case dwarf::DW_FORM_ref1:
case dwarf::DW_FORM_ref2:
case dwarf::DW_FORM_ref4:
case dwarf::DW_FORM_ref8:
return cloneDieReferenceAttribute(Die, InputDIE, AttrSpec, AttrSize, Val,
Unit);
case dwarf::DW_FORM_block:
case dwarf::DW_FORM_block1:
case dwarf::DW_FORM_block2:
case dwarf::DW_FORM_block4:
case dwarf::DW_FORM_exprloc:
return cloneBlockAttribute(Die, AttrSpec, Val, AttrSize);
case dwarf::DW_FORM_addr:
return cloneAddressAttribute(Die, AttrSpec, Val, Unit, Info);
case dwarf::DW_FORM_data1:
case dwarf::DW_FORM_data2:
case dwarf::DW_FORM_data4:
case dwarf::DW_FORM_data8:
case dwarf::DW_FORM_udata:
case dwarf::DW_FORM_sdata:
case dwarf::DW_FORM_sec_offset:
case dwarf::DW_FORM_flag:
case dwarf::DW_FORM_flag_present:
return cloneScalarAttribute(Die, InputDIE, Unit, AttrSpec, Val, AttrSize,
Info);
default:
reportWarning("Unsupported attribute form in cloneAttribute. Dropping.", &U,
&InputDIE);
}
return 0;
}
/// \brief Apply the valid relocations found by findValidRelocs() to
/// the buffer \p Data, taking into account that Data is at \p BaseOffset
/// in the debug_info section.
///
/// Like for findValidRelocs(), this function must be called with
/// monotonic \p BaseOffset values.
///
/// \returns wether any reloc has been applied.
bool DwarfLinker::applyValidRelocs(MutableArrayRef<char> Data,
uint32_t BaseOffset, bool isLittleEndian) {
assert((NextValidReloc == 0 ||
BaseOffset > ValidRelocs[NextValidReloc - 1].Offset) &&
"BaseOffset should only be increasing.");
if (NextValidReloc >= ValidRelocs.size())
return false;
// Skip relocs that haven't been applied.
while (NextValidReloc < ValidRelocs.size() &&
ValidRelocs[NextValidReloc].Offset < BaseOffset)
++NextValidReloc;
bool Applied = false;
uint64_t EndOffset = BaseOffset + Data.size();
while (NextValidReloc < ValidRelocs.size() &&
ValidRelocs[NextValidReloc].Offset >= BaseOffset &&
ValidRelocs[NextValidReloc].Offset < EndOffset) {
const auto &ValidReloc = ValidRelocs[NextValidReloc++];
assert(ValidReloc.Offset - BaseOffset < Data.size());
assert(ValidReloc.Offset - BaseOffset + ValidReloc.Size <= Data.size());
char Buf[8];
uint64_t Value = ValidReloc.Mapping->getValue().BinaryAddress;
Value += ValidReloc.Addend;
for (unsigned i = 0; i != ValidReloc.Size; ++i) {
unsigned Index = isLittleEndian ? i : (ValidReloc.Size - i - 1);
Buf[i] = uint8_t(Value >> (Index * 8));
}
assert(ValidReloc.Size <= sizeof(Buf));
memcpy(&Data[ValidReloc.Offset - BaseOffset], Buf, ValidReloc.Size);
Applied = true;
}
return Applied;
}
/// \brief Recursively clone \p InputDIE's subtrees that have been
/// selected to appear in the linked output.
///
/// \param OutOffset is the Offset where the newly created DIE will
/// lie in the linked compile unit.
///
/// \returns the cloned DIE object or null if nothing was selected.
DIE *DwarfLinker::cloneDIE(const DWARFDebugInfoEntryMinimal &InputDIE,
CompileUnit &Unit, int64_t PCOffset,
uint32_t OutOffset) {
DWARFUnit &U = Unit.getOrigUnit();
unsigned Idx = U.getDIEIndex(&InputDIE);
CompileUnit::DIEInfo &Info = Unit.getInfo(Idx);
// Should the DIE appear in the output?
if (!Unit.getInfo(Idx).Keep)
return nullptr;
uint32_t Offset = InputDIE.getOffset();
// The DIE might have been already created by a forward reference
// (see cloneDieReferenceAttribute()).
DIE *Die = Info.Clone;
if (!Die)
Die = Info.Clone = new DIE(dwarf::Tag(InputDIE.getTag()));
assert(Die->getTag() == InputDIE.getTag());
Die->setOffset(OutOffset);
// Extract and clone every attribute.
DataExtractor Data = U.getDebugInfoExtractor();
uint32_t NextOffset = U.getDIEAtIndex(Idx + 1)->getOffset();
AttributesInfo AttrInfo;
// We could copy the data only if we need to aply a relocation to
// it. After testing, it seems there is no performance downside to
// doing the copy unconditionally, and it makes the code simpler.
SmallString<40> DIECopy(Data.getData().substr(Offset, NextOffset - Offset));
Data = DataExtractor(DIECopy, Data.isLittleEndian(), Data.getAddressSize());
// Modify the copy with relocated addresses.
if (applyValidRelocs(DIECopy, Offset, Data.isLittleEndian())) {
// If we applied relocations, we store the value of high_pc that was
// potentially stored in the input DIE. If high_pc is an address
// (Dwarf version == 2), then it might have been relocated to a
// totally unrelated value (because the end address in the object
// file might be start address of another function which got moved
// independantly by the linker). The computation of the actual
// high_pc value is done in cloneAddressAttribute().
AttrInfo.OrigHighPc =
InputDIE.getAttributeValueAsAddress(&U, dwarf::DW_AT_high_pc, 0);
}
// Reset the Offset to 0 as we will be working on the local copy of
// the data.
Offset = 0;
const auto *Abbrev = InputDIE.getAbbreviationDeclarationPtr();
Offset += getULEB128Size(Abbrev->getCode());
// We are entering a subprogram. Get and propagate the PCOffset.
if (Die->getTag() == dwarf::DW_TAG_subprogram)
PCOffset = Info.AddrAdjust;
AttrInfo.PCOffset = PCOffset;
for (const auto &AttrSpec : Abbrev->attributes()) {
DWARFFormValue Val(AttrSpec.Form);
uint32_t AttrSize = Offset;
Val.extractValue(Data, &Offset, &U);
AttrSize = Offset - AttrSize;
OutOffset +=
cloneAttribute(*Die, InputDIE, Unit, Val, AttrSpec, AttrSize, AttrInfo);
}
DIEAbbrev &NewAbbrev = Die->getAbbrev();
// If a scope DIE is kept, we must have kept at least one child. If
// it's not the case, we'll just be emitting one wasteful end of
// children marker, but things won't break.
if (InputDIE.hasChildren())
NewAbbrev.setChildrenFlag(dwarf::DW_CHILDREN_yes);
// Assign a permanent abbrev number
AssignAbbrev(Die->getAbbrev());
// Add the size of the abbreviation number to the output offset.
OutOffset += getULEB128Size(Die->getAbbrevNumber());
if (!Abbrev->hasChildren()) {
// Update our size.
Die->setSize(OutOffset - Die->getOffset());
return Die;
}
// Recursively clone children.
for (auto *Child = InputDIE.getFirstChild(); Child && !Child->isNULL();
Child = Child->getSibling()) {
if (DIE *Clone = cloneDIE(*Child, Unit, PCOffset, OutOffset)) {
Die->addChild(std::unique_ptr<DIE>(Clone));
OutOffset = Clone->getOffset() + Clone->getSize();
}
}
// Account for the end of children marker.
OutOffset += sizeof(int8_t);
// Update our size.
Die->setSize(OutOffset - Die->getOffset());
return Die;
}
/// \brief Patch the input object file relevant debug_ranges entries
/// and emit them in the output file. Update the relevant attributes
/// to point at the new entries.
void DwarfLinker::patchRangesForUnit(const CompileUnit &Unit,
DWARFContext &OrigDwarf) const {
DWARFDebugRangeList RangeList;
const auto &FunctionRanges = Unit.getFunctionRanges();
unsigned AddressSize = Unit.getOrigUnit().getAddressByteSize();
DataExtractor RangeExtractor(OrigDwarf.getRangeSection(),
OrigDwarf.isLittleEndian(), AddressSize);
auto InvalidRange = FunctionRanges.end(), CurrRange = InvalidRange;
DWARFUnit &OrigUnit = Unit.getOrigUnit();
const auto *OrigUnitDie = OrigUnit.getCompileUnitDIE(false);
uint64_t OrigLowPc = OrigUnitDie->getAttributeValueAsAddress(
&OrigUnit, dwarf::DW_AT_low_pc, -1ULL);
// Ranges addresses are based on the unit's low_pc. Compute the
// offset we need to apply to adapt to the the new unit's low_pc.
int64_t UnitPcOffset = 0;
if (OrigLowPc != -1ULL)
UnitPcOffset = int64_t(OrigLowPc) - Unit.getLowPc();
for (const auto &RangeAttribute : Unit.getRangesAttributes()) {
uint32_t Offset = RangeAttribute->getValue();
RangeAttribute->setValue(Streamer->getRangesSectionSize());
RangeList.extract(RangeExtractor, &Offset);
const auto &Entries = RangeList.getEntries();
const DWARFDebugRangeList::RangeListEntry &First = Entries.front();
if (CurrRange == InvalidRange || First.StartAddress < CurrRange.start() ||
First.StartAddress >= CurrRange.stop()) {
CurrRange = FunctionRanges.find(First.StartAddress + OrigLowPc);
if (CurrRange == InvalidRange ||
CurrRange.start() > First.StartAddress + OrigLowPc) {
reportWarning("no mapping for range.");
continue;
}
}
Streamer->emitRangesEntries(UnitPcOffset, OrigLowPc, CurrRange, Entries,
AddressSize);
}
}
/// \brief Generate the debug_aranges entries for \p Unit and if the
/// unit has a DW_AT_ranges attribute, also emit the debug_ranges
/// contribution for this attribute.
/// FIXME: this could actually be done right in patchRangesForUnit,
/// but for the sake of initial bit-for-bit compatibility with legacy
/// dsymutil, we have to do it in a delayed pass.
void DwarfLinker::generateUnitRanges(CompileUnit &Unit) const {
DIEInteger *Attr = Unit.getUnitRangesAttribute();
if (Attr)
Attr->setValue(Streamer->getRangesSectionSize());
Streamer->emitUnitRangesEntries(Unit, Attr != nullptr);
}
bool DwarfLinker::link(const DebugMap &Map) {
if (Map.begin() == Map.end()) {
errs() << "Empty debug map.\n";
return false;
}
if (!createStreamer(Map.getTriple(), OutputFilename))
return false;
// Size of the DIEs (and headers) generated for the linked output.
uint64_t OutputDebugInfoSize = 0;
// A unique ID that identifies each compile unit.
unsigned UnitID = 0;
for (const auto &Obj : Map.objects()) {
CurrentDebugObject = Obj.get();
if (Options.Verbose)
outs() << "DEBUG MAP OBJECT: " << Obj->getObjectFilename() << "\n";
auto ErrOrObj = BinHolder.GetObjectFile(Obj->getObjectFilename());
if (std::error_code EC = ErrOrObj.getError()) {
reportWarning(Twine(Obj->getObjectFilename()) + ": " + EC.message());
continue;
}
// Look for relocations that correspond to debug map entries.
if (!findValidRelocsInDebugInfo(*ErrOrObj, *Obj)) {
if (Options.Verbose)
outs() << "No valid relocations found. Skipping.\n";
continue;
}
// Setup access to the debug info.
DWARFContextInMemory DwarfContext(*ErrOrObj);
startDebugObject(DwarfContext);
// In a first phase, just read in the debug info and store the DIE
// parent links that we will use during the next phase.
for (const auto &CU : DwarfContext.compile_units()) {
auto *CUDie = CU->getCompileUnitDIE(false);
if (Options.Verbose) {
outs() << "Input compilation unit:";
CUDie->dump(outs(), CU.get(), 0);
}
Units.emplace_back(*CU, UnitID++);
gatherDIEParents(CUDie, 0, Units.back());
}
// Then mark all the DIEs that need to be present in the linked
// output and collect some information about them. Note that this
// loop can not be merged with the previous one becaue cross-cu
// references require the ParentIdx to be setup for every CU in
// the object file before calling this.
for (auto &CurrentUnit : Units)
lookForDIEsToKeep(*CurrentUnit.getOrigUnit().getCompileUnitDIE(), *Obj,
CurrentUnit, 0);
// The calls to applyValidRelocs inside cloneDIE will walk the
// reloc array again (in the same way findValidRelocsInDebugInfo()
// did). We need to reset the NextValidReloc index to the beginning.
NextValidReloc = 0;
// Construct the output DIE tree by cloning the DIEs we chose to
// keep above. If there are no valid relocs, then there's nothing
// to clone/emit.
if (!ValidRelocs.empty())
for (auto &CurrentUnit : Units) {
const auto *InputDIE = CurrentUnit.getOrigUnit().getCompileUnitDIE();
CurrentUnit.setStartOffset(OutputDebugInfoSize);
DIE *OutputDIE = cloneDIE(*InputDIE, CurrentUnit, 0 /* PCOffset */,
11 /* Unit Header size */);
CurrentUnit.setOutputUnitDIE(OutputDIE);
OutputDebugInfoSize = CurrentUnit.computeNextUnitOffset();
if (!OutputDIE || Options.NoOutput)
continue;
patchRangesForUnit(CurrentUnit, DwarfContext);
Streamer->emitLocationsForUnit(CurrentUnit, DwarfContext);
}
// Emit all the compile unit's debug information.
if (!ValidRelocs.empty() && !Options.NoOutput)
for (auto &CurrentUnit : Units) {
generateUnitRanges(CurrentUnit);
CurrentUnit.fixupForwardReferences();
Streamer->emitCompileUnitHeader(CurrentUnit);
if (!CurrentUnit.getOutputUnitDIE())
continue;
Streamer->emitDIE(*CurrentUnit.getOutputUnitDIE());
}
// Clean-up before starting working on the next object.
endDebugObject();
}
// Emit everything that's global.
if (!Options.NoOutput) {
Streamer->emitAbbrevs(Abbreviations);
Streamer->emitStrings(StringPool);
}
return Options.NoOutput ? true : Streamer->finish();
}
}
bool linkDwarf(StringRef OutputFilename, const DebugMap &DM,
const LinkOptions &Options) {
DwarfLinker Linker(OutputFilename, Options);
return Linker.link(DM);
}
}
}
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