src/llvm-project/llvm/lib/ExecutionEngine/Orc/Debugging/DebuggerSupportPlugin.cpp - toolchain/rustc - Git at Google

 //===------- DebuggerSupportPlugin.cpp - Utils for debugger support -------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 //
 //===----------------------------------------------------------------------===//

 #include "llvm/ExecutionEngine/Orc/Debugging/DebuggerSupportPlugin.h"
 #include "llvm/ExecutionEngine/Orc/MachOBuilder.h"

 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/BinaryFormat/MachO.h"
 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
 #include "llvm/DebugInfo/DWARF/DWARFDebugLine.h"

 #include <chrono>

 #define DEBUG_TYPE "orc"

 using namespace llvm;
 using namespace llvm::jitlink;
 using namespace llvm::orc;

 static const char *SynthDebugSectionName = "__jitlink_synth_debug_object";

 namespace {

 class MachODebugObjectSynthesizerBase
     : public GDBJITDebugInfoRegistrationPlugin::DebugSectionSynthesizer {
 public:
   static bool isDebugSection(Section &Sec) {
     return Sec.getName().starts_with("__DWARF,");
   }

   MachODebugObjectSynthesizerBase(LinkGraph &G, ExecutorAddr RegisterActionAddr)
       : G(G), RegisterActionAddr(RegisterActionAddr) {}
   virtual ~MachODebugObjectSynthesizerBase() = default;

   Error preserveDebugSections() {
     if (G.findSectionByName(SynthDebugSectionName)) {
       LLVM_DEBUG({
         dbgs() << "MachODebugObjectSynthesizer skipping graph " << G.getName()
                << " which contains an unexpected existing "
                << SynthDebugSectionName << " section.\n";
       });
       return Error::success();
     }

     LLVM_DEBUG({
       dbgs() << "MachODebugObjectSynthesizer visiting graph " << G.getName()
              << "\n";
     });
     for (auto &Sec : G.sections()) {
       if (!isDebugSection(Sec))
         continue;
       // Preserve blocks in this debug section by marking one existing symbol
       // live for each block, and introducing a new live, anonymous symbol for
       // each currently unreferenced block.
       LLVM_DEBUG({
         dbgs() << "  Preserving debug section " << Sec.getName() << "\n";
       });
       SmallSet<Block *, 8> PreservedBlocks;
       for (auto *Sym : Sec.symbols()) {
         bool NewPreservedBlock =
             PreservedBlocks.insert(&Sym->getBlock()).second;
         if (NewPreservedBlock)
           Sym->setLive(true);
       }
       for (auto *B : Sec.blocks())
         if (!PreservedBlocks.count(B))
           G.addAnonymousSymbol(*B, 0, 0, false, true);
     }

     return Error::success();
   }

 protected:
   LinkGraph &G;
   ExecutorAddr RegisterActionAddr;
 };

 template <typename MachOTraits>
 class MachODebugObjectSynthesizer : public MachODebugObjectSynthesizerBase {
 public:
   MachODebugObjectSynthesizer(ExecutionSession &ES, LinkGraph &G,
                               ExecutorAddr RegisterActionAddr)
       : MachODebugObjectSynthesizerBase(G, RegisterActionAddr),
         Builder(ES.getPageSize()) {}

   using MachODebugObjectSynthesizerBase::MachODebugObjectSynthesizerBase;

   Error startSynthesis() override {
     LLVM_DEBUG({
       dbgs() << "Creating " << SynthDebugSectionName << " for " << G.getName()
              << "\n";
     });

     for (auto &Sec : G.sections()) {
       if (Sec.blocks().empty())
         continue;

       // Skip sections whose name's don't fit the MachO standard.
       if (Sec.getName().empty() || Sec.getName().size() > 33 ||
           Sec.getName().find(',') > 16)
         continue;

       if (isDebugSection(Sec))
         DebugSections.push_back({&Sec, nullptr});
       else if (Sec.getMemLifetime() != MemLifetime::NoAlloc)
         NonDebugSections.push_back({&Sec, nullptr});
     }

     // Bail out early if no debug sections.
     if (DebugSections.empty())
       return Error::success();

     // Write MachO header and debug section load commands.
     Builder.Header.filetype = MachO::MH_OBJECT;
     switch (G.getTargetTriple().getArch()) {
     case Triple::x86_64:
       Builder.Header.cputype = MachO::CPU_TYPE_X86_64;
       Builder.Header.cpusubtype = MachO::CPU_SUBTYPE_X86_64_ALL;
       break;
     case Triple::aarch64:
       Builder.Header.cputype = MachO::CPU_TYPE_ARM64;
       Builder.Header.cpusubtype = MachO::CPU_SUBTYPE_ARM64_ALL;
       break;
     default:
       llvm_unreachable("Unsupported architecture");
     }

     Seg = &Builder.addSegment("");

     StringMap<std::unique_ptr<MemoryBuffer>> DebugSectionMap;
     StringRef DebugLineSectionData;
     for (auto &DSec : DebugSections) {
       auto [SegName, SecName] = DSec.GraphSec->getName().split(',');
       DSec.BuilderSec = &Seg->addSection(SecName, SegName);

       SectionRange SR(*DSec.GraphSec);
       DSec.BuilderSec->Content.Size = SR.getSize();
       if (!SR.empty()) {
         DSec.BuilderSec->align = Log2_64(SR.getFirstBlock()->getAlignment());
         StringRef SectionData(SR.getFirstBlock()->getContent().data(),
                               SR.getFirstBlock()->getSize());
         DebugSectionMap[SecName] =
             MemoryBuffer::getMemBuffer(SectionData, G.getName(), false);
         if (SecName == "__debug_line")
           DebugLineSectionData = SectionData;
       }
     }

     std::optional<StringRef> FileName;
     if (!DebugLineSectionData.empty()) {
       assert((G.getEndianness() == llvm::endianness::big ||
               G.getEndianness() == llvm::endianness::little) &&
              "G.getEndianness() must be either big or little");
       auto DWARFCtx =
           DWARFContext::create(DebugSectionMap, G.getPointerSize(),
                                G.getEndianness() == llvm::endianness::little);
       DWARFDataExtractor DebugLineData(
           DebugLineSectionData, G.getEndianness() == llvm::endianness::little,
           G.getPointerSize());
       uint64_t Offset = 0;
       DWARFDebugLine::LineTable LineTable;

       // Try to parse line data. Consume error on failure.
       if (auto Err = LineTable.parse(DebugLineData, &Offset, *DWARFCtx, nullptr,
                                      consumeError)) {
         handleAllErrors(std::move(Err), [&](ErrorInfoBase &EIB) {
           LLVM_DEBUG({
             dbgs() << "Cannot parse line table for \"" << G.getName() << "\": ";
             EIB.log(dbgs());
             dbgs() << "\n";
           });
         });
       } else {
         if (!LineTable.Prologue.FileNames.empty())
           FileName = *dwarf::toString(LineTable.Prologue.FileNames[0].Name);
       }
     }

     // If no line table (or unable to use) then use graph name.
     // FIXME: There are probably other debug sections we should look in first.
     if (!FileName)
       FileName = StringRef(G.getName());

     Builder.addSymbol("", MachO::N_SO, 0, 0, 0);
     Builder.addSymbol(*FileName, MachO::N_SO, 0, 0, 0);
     auto TimeStamp = std::chrono::duration_cast<std::chrono::seconds>(
                          std::chrono::system_clock::now().time_since_epoch())
                          .count();
     Builder.addSymbol("", MachO::N_OSO, 3, 1, TimeStamp);

     for (auto &NDSP : NonDebugSections) {
       auto [SegName, SecName] = NDSP.GraphSec->getName().split(',');
       NDSP.BuilderSec = &Seg->addSection(SecName, SegName);
       SectionRange SR(*NDSP.GraphSec);
       if (!SR.empty())
         NDSP.BuilderSec->align = Log2_64(SR.getFirstBlock()->getAlignment());

       // Add stabs.
       for (auto *Sym : NDSP.GraphSec->symbols()) {
         // Skip anonymous symbols.
         if (!Sym->hasName())
           continue;

         uint8_t SymType = Sym->isCallable() ? MachO::N_FUN : MachO::N_GSYM;

         Builder.addSymbol("", MachO::N_BNSYM, 1, 0, 0);
         StabSymbols.push_back(
             {*Sym, Builder.addSymbol(Sym->getName(), SymType, 1, 0, 0),
              Builder.addSymbol(Sym->getName(), SymType, 0, 0, 0)});
         Builder.addSymbol("", MachO::N_ENSYM, 1, 0, 0);
       }
     }

     Builder.addSymbol("", MachO::N_SO, 1, 0, 0);

     // Lay out the debug object, create a section and block for it.
     size_t DebugObjectSize = Builder.layout();

     auto &SDOSec = G.createSection(SynthDebugSectionName, MemProt::Read);
     MachOContainerBlock = &G.createMutableContentBlock(
         SDOSec, G.allocateBuffer(DebugObjectSize), orc::ExecutorAddr(), 8, 0);

     return Error::success();
   }

   Error completeSynthesisAndRegister() override {
     if (!MachOContainerBlock) {
       LLVM_DEBUG({
         dbgs() << "Not writing MachO debug object header for " << G.getName()
                << " since createDebugSection failed\n";
       });

       return Error::success();
     }
     ExecutorAddr MaxAddr;
     for (auto &NDSec : NonDebugSections) {
       SectionRange SR(*NDSec.GraphSec);
       NDSec.BuilderSec->addr = SR.getStart().getValue();
       NDSec.BuilderSec->size = SR.getSize();
       NDSec.BuilderSec->offset = SR.getStart().getValue();
       if (SR.getEnd() > MaxAddr)
         MaxAddr = SR.getEnd();
     }

     for (auto &DSec : DebugSections) {
       if (DSec.GraphSec->blocks_size() != 1)
         return make_error<StringError>(
             "Unexpected number of blocks in debug info section",
             inconvertibleErrorCode());

       if (ExecutorAddr(DSec.BuilderSec->addr) + DSec.BuilderSec->size > MaxAddr)
         MaxAddr = ExecutorAddr(DSec.BuilderSec->addr) + DSec.BuilderSec->size;

       auto &B = **DSec.GraphSec->blocks().begin();
       DSec.BuilderSec->Content.Data = B.getContent().data();
       DSec.BuilderSec->Content.Size = B.getContent().size();
       DSec.BuilderSec->flags |= MachO::S_ATTR_DEBUG;
     }

     LLVM_DEBUG({
       dbgs() << "Writing MachO debug object header for " << G.getName() << "\n";
     });

     // Update stab symbol addresses.
     for (auto &SS : StabSymbols) {
       SS.StartStab.nlist().n_value = SS.Sym.getAddress().getValue();
       SS.EndStab.nlist().n_value = SS.Sym.getSize();
     }

     Builder.write(MachOContainerBlock->getAlreadyMutableContent());

     static constexpr bool AutoRegisterCode = true;
     SectionRange R(MachOContainerBlock->getSection());
     G.allocActions().push_back(
         {cantFail(shared::WrapperFunctionCall::Create<
                   shared::SPSArgList<shared::SPSExecutorAddrRange, bool>>(
              RegisterActionAddr, R.getRange(), AutoRegisterCode)),
          {}});

     return Error::success();
   }

 private:
   struct SectionPair {
     Section *GraphSec = nullptr;
     typename MachOBuilder<MachOTraits>::Section *BuilderSec = nullptr;
   };

   struct StabSymbolsEntry {
     using RelocTarget = typename MachOBuilder<MachOTraits>::RelocTarget;

     StabSymbolsEntry(Symbol &Sym, RelocTarget StartStab, RelocTarget EndStab)
         : Sym(Sym), StartStab(StartStab), EndStab(EndStab) {}

     Symbol &Sym;
     RelocTarget StartStab, EndStab;
   };

   using BuilderType = MachOBuilder<MachOTraits>;

   Block *MachOContainerBlock = nullptr;
   MachOBuilder<MachOTraits> Builder;
   typename MachOBuilder<MachOTraits>::Segment *Seg = nullptr;
   std::vector<StabSymbolsEntry> StabSymbols;
   SmallVector<SectionPair, 16> DebugSections;
   SmallVector<SectionPair, 16> NonDebugSections;
 };

 } // end anonymous namespace

 namespace llvm {
 namespace orc {

 Expected<std::unique_ptr<GDBJITDebugInfoRegistrationPlugin>>
 GDBJITDebugInfoRegistrationPlugin::Create(ExecutionSession &ES,
                                           JITDylib &ProcessJD,
                                           const Triple &TT) {
   auto RegisterActionAddr =
       TT.isOSBinFormatMachO()
           ? ES.intern("_llvm_orc_registerJITLoaderGDBAllocAction")
           : ES.intern("llvm_orc_registerJITLoaderGDBAllocAction");

   if (auto RegisterSym = ES.lookup({&ProcessJD}, RegisterActionAddr))
     return std::make_unique<GDBJITDebugInfoRegistrationPlugin>(
         RegisterSym->getAddress());
   else
     return RegisterSym.takeError();
 }

 Error GDBJITDebugInfoRegistrationPlugin::notifyFailed(
     MaterializationResponsibility &MR) {
   return Error::success();
 }

 Error GDBJITDebugInfoRegistrationPlugin::notifyRemovingResources(
     JITDylib &JD, ResourceKey K) {
   return Error::success();
 }

 void GDBJITDebugInfoRegistrationPlugin::notifyTransferringResources(
     JITDylib &JD, ResourceKey DstKey, ResourceKey SrcKey) {}

 void GDBJITDebugInfoRegistrationPlugin::modifyPassConfig(
     MaterializationResponsibility &MR, LinkGraph &LG,
     PassConfiguration &PassConfig) {

   if (LG.getTargetTriple().getObjectFormat() == Triple::MachO)
     modifyPassConfigForMachO(MR, LG, PassConfig);
   else {
     LLVM_DEBUG({
       dbgs() << "GDBJITDebugInfoRegistrationPlugin skipping unspported graph "
              << LG.getName() << "(triple = " << LG.getTargetTriple().str()
              << "\n";
     });
   }
 }

 void GDBJITDebugInfoRegistrationPlugin::modifyPassConfigForMachO(
     MaterializationResponsibility &MR, jitlink::LinkGraph &LG,
     jitlink::PassConfiguration &PassConfig) {

   switch (LG.getTargetTriple().getArch()) {
   case Triple::x86_64:
   case Triple::aarch64:
     // Supported, continue.
     assert(LG.getPointerSize() == 8 && "Graph has incorrect pointer size");
     assert(LG.getEndianness() == llvm::endianness::little &&
            "Graph has incorrect endianness");
     break;
   default:
     // Unsupported.
     LLVM_DEBUG({
       dbgs() << "GDBJITDebugInfoRegistrationPlugin skipping unsupported "
              << "MachO graph " << LG.getName()
              << "(triple = " << LG.getTargetTriple().str()
              << ", pointer size = " << LG.getPointerSize() << ", endianness = "
              << (LG.getEndianness() == llvm::endianness::big ? "big" : "little")
              << ")\n";
     });
     return;
   }

   // Scan for debug sections. If we find one then install passes.
   bool HasDebugSections = false;
   for (auto &Sec : LG.sections())
     if (MachODebugObjectSynthesizerBase::isDebugSection(Sec)) {
       HasDebugSections = true;
       break;
     }

   if (HasDebugSections) {
     LLVM_DEBUG({
       dbgs() << "GDBJITDebugInfoRegistrationPlugin: Graph " << LG.getName()
              << " contains debug info. Installing debugger support passes.\n";
     });

     auto MDOS = std::make_shared<MachODebugObjectSynthesizer<MachO64LE>>(
         MR.getTargetJITDylib().getExecutionSession(), LG, RegisterActionAddr);
     PassConfig.PrePrunePasses.push_back(
         [=](LinkGraph &G) { return MDOS->preserveDebugSections(); });
     PassConfig.PostPrunePasses.push_back(
         [=](LinkGraph &G) { return MDOS->startSynthesis(); });
     PassConfig.PostFixupPasses.push_back(
         [=](LinkGraph &G) { return MDOS->completeSynthesisAndRegister(); });
   } else {
     LLVM_DEBUG({
       dbgs() << "GDBJITDebugInfoRegistrationPlugin: Graph " << LG.getName()
              << " contains no debug info. Skipping.\n";
     });
   }
 }

 } // namespace orc
 } // namespace llvm
	//===------- DebuggerSupportPlugin.cpp - Utils for debugger support -------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//
	//
	//
	//===----------------------------------------------------------------------===//

	#include "llvm/ExecutionEngine/Orc/Debugging/DebuggerSupportPlugin.h"
	#include "llvm/ExecutionEngine/Orc/MachOBuilder.h"

	#include "llvm/ADT/SmallSet.h"
	#include "llvm/ADT/SmallVector.h"
	#include "llvm/BinaryFormat/MachO.h"
	#include "llvm/DebugInfo/DWARF/DWARFContext.h"
	#include "llvm/DebugInfo/DWARF/DWARFDebugLine.h"

	#include <chrono>

	#define DEBUG_TYPE "orc"

	using namespace llvm;
	using namespace llvm::jitlink;
	using namespace llvm::orc;

	static const char *SynthDebugSectionName = "__jitlink_synth_debug_object";

	namespace {

	class MachODebugObjectSynthesizerBase
	: public GDBJITDebugInfoRegistrationPlugin::DebugSectionSynthesizer {
	public:
	static bool isDebugSection(Section &Sec) {
	return Sec.getName().starts_with("__DWARF,");
	}

	MachODebugObjectSynthesizerBase(LinkGraph &G, ExecutorAddr RegisterActionAddr)
	: G(G), RegisterActionAddr(RegisterActionAddr) {}
	virtual ~MachODebugObjectSynthesizerBase() = default;

	Error preserveDebugSections() {
	if (G.findSectionByName(SynthDebugSectionName)) {
	LLVM_DEBUG({
	dbgs() << "MachODebugObjectSynthesizer skipping graph " << G.getName()
	<< " which contains an unexpected existing "
	<< SynthDebugSectionName << " section.\n";
	});
	return Error::success();
	}

	LLVM_DEBUG({
	dbgs() << "MachODebugObjectSynthesizer visiting graph " << G.getName()
	<< "\n";
	});
	for (auto &Sec : G.sections()) {
	if (!isDebugSection(Sec))
	continue;
	// Preserve blocks in this debug section by marking one existing symbol
	// live for each block, and introducing a new live, anonymous symbol for
	// each currently unreferenced block.
	LLVM_DEBUG({
	dbgs() << " Preserving debug section " << Sec.getName() << "\n";
	});
	SmallSet<Block *, 8> PreservedBlocks;
	for (auto *Sym : Sec.symbols()) {
	bool NewPreservedBlock =
	PreservedBlocks.insert(&Sym->getBlock()).second;
	if (NewPreservedBlock)
	Sym->setLive(true);
	}
	for (auto *B : Sec.blocks())
	if (!PreservedBlocks.count(B))
	G.addAnonymousSymbol(*B, 0, 0, false, true);
	}

	return Error::success();
	}

	protected:
	LinkGraph &G;
	ExecutorAddr RegisterActionAddr;
	};

	template <typename MachOTraits>
	class MachODebugObjectSynthesizer : public MachODebugObjectSynthesizerBase {
	public:
	MachODebugObjectSynthesizer(ExecutionSession &ES, LinkGraph &G,
	ExecutorAddr RegisterActionAddr)
	: MachODebugObjectSynthesizerBase(G, RegisterActionAddr),
	Builder(ES.getPageSize()) {}

	using MachODebugObjectSynthesizerBase::MachODebugObjectSynthesizerBase;

	Error startSynthesis() override {
	LLVM_DEBUG({
	dbgs() << "Creating " << SynthDebugSectionName << " for " << G.getName()
	<< "\n";
	});

	for (auto &Sec : G.sections()) {
	if (Sec.blocks().empty())
	continue;

	// Skip sections whose name's don't fit the MachO standard.
	if (Sec.getName().empty() \|\| Sec.getName().size() > 33 \|\|
	Sec.getName().find(',') > 16)
	continue;

	if (isDebugSection(Sec))
	DebugSections.push_back({&Sec, nullptr});
	else if (Sec.getMemLifetime() != MemLifetime::NoAlloc)
	NonDebugSections.push_back({&Sec, nullptr});
	}

	// Bail out early if no debug sections.
	if (DebugSections.empty())
	return Error::success();

	// Write MachO header and debug section load commands.
	Builder.Header.filetype = MachO::MH_OBJECT;
	switch (G.getTargetTriple().getArch()) {
	case Triple::x86_64:
	Builder.Header.cputype = MachO::CPU_TYPE_X86_64;
	Builder.Header.cpusubtype = MachO::CPU_SUBTYPE_X86_64_ALL;
	break;
	case Triple::aarch64:
	Builder.Header.cputype = MachO::CPU_TYPE_ARM64;
	Builder.Header.cpusubtype = MachO::CPU_SUBTYPE_ARM64_ALL;
	break;
	default:
	llvm_unreachable("Unsupported architecture");
	}

	Seg = &Builder.addSegment("");

	StringMap<std::unique_ptr<MemoryBuffer>> DebugSectionMap;
	StringRef DebugLineSectionData;
	for (auto &DSec : DebugSections) {
	auto [SegName, SecName] = DSec.GraphSec->getName().split(',');
	DSec.BuilderSec = &Seg->addSection(SecName, SegName);

	SectionRange SR(*DSec.GraphSec);
	DSec.BuilderSec->Content.Size = SR.getSize();
	if (!SR.empty()) {
	DSec.BuilderSec->align = Log2_64(SR.getFirstBlock()->getAlignment());
	StringRef SectionData(SR.getFirstBlock()->getContent().data(),
	SR.getFirstBlock()->getSize());
	DebugSectionMap[SecName] =
	MemoryBuffer::getMemBuffer(SectionData, G.getName(), false);
	if (SecName == "__debug_line")
	DebugLineSectionData = SectionData;
	}
	}

	std::optional<StringRef> FileName;
	if (!DebugLineSectionData.empty()) {
	assert((G.getEndianness() == llvm::endianness::big \|\|
	G.getEndianness() == llvm::endianness::little) &&
	"G.getEndianness() must be either big or little");
	auto DWARFCtx =
	DWARFContext::create(DebugSectionMap, G.getPointerSize(),
	G.getEndianness() == llvm::endianness::little);
	DWARFDataExtractor DebugLineData(
	DebugLineSectionData, G.getEndianness() == llvm::endianness::little,
	G.getPointerSize());
	uint64_t Offset = 0;
	DWARFDebugLine::LineTable LineTable;

	// Try to parse line data. Consume error on failure.
	if (auto Err = LineTable.parse(DebugLineData, &Offset, *DWARFCtx, nullptr,
	consumeError)) {
	handleAllErrors(std::move(Err), [&](ErrorInfoBase &EIB) {
	LLVM_DEBUG({
	dbgs() << "Cannot parse line table for \"" << G.getName() << "\": ";
	EIB.log(dbgs());
	dbgs() << "\n";
	});
	});
	} else {
	if (!LineTable.Prologue.FileNames.empty())
	FileName = *dwarf::toString(LineTable.Prologue.FileNames[0].Name);
	}
	}

	// If no line table (or unable to use) then use graph name.
	// FIXME: There are probably other debug sections we should look in first.
	if (!FileName)
	FileName = StringRef(G.getName());

	Builder.addSymbol("", MachO::N_SO, 0, 0, 0);
	Builder.addSymbol(*FileName, MachO::N_SO, 0, 0, 0);
	auto TimeStamp = std::chrono::duration_cast<std::chrono::seconds>(
	std::chrono::system_clock::now().time_since_epoch())
	.count();
	Builder.addSymbol("", MachO::N_OSO, 3, 1, TimeStamp);

	for (auto &NDSP : NonDebugSections) {
	auto [SegName, SecName] = NDSP.GraphSec->getName().split(',');
	NDSP.BuilderSec = &Seg->addSection(SecName, SegName);
	SectionRange SR(*NDSP.GraphSec);
	if (!SR.empty())
	NDSP.BuilderSec->align = Log2_64(SR.getFirstBlock()->getAlignment());

	// Add stabs.
	for (auto *Sym : NDSP.GraphSec->symbols()) {
	// Skip anonymous symbols.
	if (!Sym->hasName())
	continue;

	uint8_t SymType = Sym->isCallable() ? MachO::N_FUN : MachO::N_GSYM;

	Builder.addSymbol("", MachO::N_BNSYM, 1, 0, 0);
	StabSymbols.push_back(
	{*Sym, Builder.addSymbol(Sym->getName(), SymType, 1, 0, 0),
	Builder.addSymbol(Sym->getName(), SymType, 0, 0, 0)});
	Builder.addSymbol("", MachO::N_ENSYM, 1, 0, 0);
	}
	}

	Builder.addSymbol("", MachO::N_SO, 1, 0, 0);

	// Lay out the debug object, create a section and block for it.
	size_t DebugObjectSize = Builder.layout();

	auto &SDOSec = G.createSection(SynthDebugSectionName, MemProt::Read);
	MachOContainerBlock = &G.createMutableContentBlock(
	SDOSec, G.allocateBuffer(DebugObjectSize), orc::ExecutorAddr(), 8, 0);

	return Error::success();
	}

	Error completeSynthesisAndRegister() override {
	if (!MachOContainerBlock) {
	LLVM_DEBUG({
	dbgs() << "Not writing MachO debug object header for " << G.getName()
	<< " since createDebugSection failed\n";
	});

	return Error::success();
	}
	ExecutorAddr MaxAddr;
	for (auto &NDSec : NonDebugSections) {
	SectionRange SR(*NDSec.GraphSec);
	NDSec.BuilderSec->addr = SR.getStart().getValue();
	NDSec.BuilderSec->size = SR.getSize();
	NDSec.BuilderSec->offset = SR.getStart().getValue();
	if (SR.getEnd() > MaxAddr)
	MaxAddr = SR.getEnd();
	}

	for (auto &DSec : DebugSections) {
	if (DSec.GraphSec->blocks_size() != 1)
	return make_error<StringError>(
	"Unexpected number of blocks in debug info section",
	inconvertibleErrorCode());

	if (ExecutorAddr(DSec.BuilderSec->addr) + DSec.BuilderSec->size > MaxAddr)
	MaxAddr = ExecutorAddr(DSec.BuilderSec->addr) + DSec.BuilderSec->size;

	auto &B = **DSec.GraphSec->blocks().begin();
	DSec.BuilderSec->Content.Data = B.getContent().data();
	DSec.BuilderSec->Content.Size = B.getContent().size();
	DSec.BuilderSec->flags \|= MachO::S_ATTR_DEBUG;
	}

	LLVM_DEBUG({
	dbgs() << "Writing MachO debug object header for " << G.getName() << "\n";
	});

	// Update stab symbol addresses.
	for (auto &SS : StabSymbols) {
	SS.StartStab.nlist().n_value = SS.Sym.getAddress().getValue();
	SS.EndStab.nlist().n_value = SS.Sym.getSize();
	}

	Builder.write(MachOContainerBlock->getAlreadyMutableContent());

	static constexpr bool AutoRegisterCode = true;
	SectionRange R(MachOContainerBlock->getSection());
	G.allocActions().push_back(
	{cantFail(shared::WrapperFunctionCall::Create<
	shared::SPSArgList<shared::SPSExecutorAddrRange, bool>>(
	RegisterActionAddr, R.getRange(), AutoRegisterCode)),
	{}});

	return Error::success();
	}

	private:
	struct SectionPair {
	Section *GraphSec = nullptr;
	typename MachOBuilder<MachOTraits>::Section *BuilderSec = nullptr;
	};

	struct StabSymbolsEntry {
	using RelocTarget = typename MachOBuilder<MachOTraits>::RelocTarget;

	StabSymbolsEntry(Symbol &Sym, RelocTarget StartStab, RelocTarget EndStab)
	: Sym(Sym), StartStab(StartStab), EndStab(EndStab) {}

	Symbol &Sym;
	RelocTarget StartStab, EndStab;
	};

	using BuilderType = MachOBuilder<MachOTraits>;

	Block *MachOContainerBlock = nullptr;
	MachOBuilder<MachOTraits> Builder;
	typename MachOBuilder<MachOTraits>::Segment *Seg = nullptr;
	std::vector<StabSymbolsEntry> StabSymbols;
	SmallVector<SectionPair, 16> DebugSections;
	SmallVector<SectionPair, 16> NonDebugSections;
	};

	} // end anonymous namespace

	namespace llvm {
	namespace orc {

	Expected<std::unique_ptr<GDBJITDebugInfoRegistrationPlugin>>
	GDBJITDebugInfoRegistrationPlugin::Create(ExecutionSession &ES,
	JITDylib &ProcessJD,
	const Triple &TT) {
	auto RegisterActionAddr =
	TT.isOSBinFormatMachO()
	? ES.intern("_llvm_orc_registerJITLoaderGDBAllocAction")
	: ES.intern("llvm_orc_registerJITLoaderGDBAllocAction");

	if (auto RegisterSym = ES.lookup({&ProcessJD}, RegisterActionAddr))
	return std::make_unique<GDBJITDebugInfoRegistrationPlugin>(
	RegisterSym->getAddress());
	else
	return RegisterSym.takeError();
	}

	Error GDBJITDebugInfoRegistrationPlugin::notifyFailed(
	MaterializationResponsibility &MR) {
	return Error::success();
	}

	Error GDBJITDebugInfoRegistrationPlugin::notifyRemovingResources(
	JITDylib &JD, ResourceKey K) {
	return Error::success();
	}

	void GDBJITDebugInfoRegistrationPlugin::notifyTransferringResources(
	JITDylib &JD, ResourceKey DstKey, ResourceKey SrcKey) {}

	void GDBJITDebugInfoRegistrationPlugin::modifyPassConfig(
	MaterializationResponsibility &MR, LinkGraph &LG,
	PassConfiguration &PassConfig) {

	if (LG.getTargetTriple().getObjectFormat() == Triple::MachO)
	modifyPassConfigForMachO(MR, LG, PassConfig);
	else {
	LLVM_DEBUG({
	dbgs() << "GDBJITDebugInfoRegistrationPlugin skipping unspported graph "
	<< LG.getName() << "(triple = " << LG.getTargetTriple().str()
	<< "\n";
	});
	}
	}

	void GDBJITDebugInfoRegistrationPlugin::modifyPassConfigForMachO(
	MaterializationResponsibility &MR, jitlink::LinkGraph &LG,
	jitlink::PassConfiguration &PassConfig) {

	switch (LG.getTargetTriple().getArch()) {
	case Triple::x86_64:
	case Triple::aarch64:
	// Supported, continue.
	assert(LG.getPointerSize() == 8 && "Graph has incorrect pointer size");
	assert(LG.getEndianness() == llvm::endianness::little &&
	"Graph has incorrect endianness");
	break;
	default:
	// Unsupported.
	LLVM_DEBUG({
	dbgs() << "GDBJITDebugInfoRegistrationPlugin skipping unsupported "
	<< "MachO graph " << LG.getName()
	<< "(triple = " << LG.getTargetTriple().str()
	<< ", pointer size = " << LG.getPointerSize() << ", endianness = "
	<< (LG.getEndianness() == llvm::endianness::big ? "big" : "little")
	<< ")\n";
	});
	return;
	}

	// Scan for debug sections. If we find one then install passes.
	bool HasDebugSections = false;
	for (auto &Sec : LG.sections())
	if (MachODebugObjectSynthesizerBase::isDebugSection(Sec)) {
	HasDebugSections = true;
	break;
	}

	if (HasDebugSections) {
	LLVM_DEBUG({
	dbgs() << "GDBJITDebugInfoRegistrationPlugin: Graph " << LG.getName()
	<< " contains debug info. Installing debugger support passes.\n";
	});

	auto MDOS = std::make_shared<MachODebugObjectSynthesizer<MachO64LE>>(
	MR.getTargetJITDylib().getExecutionSession(), LG, RegisterActionAddr);
	PassConfig.PrePrunePasses.push_back(
	[=](LinkGraph &G) { return MDOS->preserveDebugSections(); });
	PassConfig.PostPrunePasses.push_back(
	[=](LinkGraph &G) { return MDOS->startSynthesis(); });
	PassConfig.PostFixupPasses.push_back(
	[=](LinkGraph &G) { return MDOS->completeSynthesisAndRegister(); });
	} else {
	LLVM_DEBUG({
	dbgs() << "GDBJITDebugInfoRegistrationPlugin: Graph " << LG.getName()
	<< " contains no debug info. Skipping.\n";
	});
	}
	}

	} // namespace orc
	} // namespace llvm