[llvm] 69be352 - Reapply "[ORC] Initial MachO debugging support (via GDB JIT debug.." with fixes.

Lang Hames via llvm-commits llvm-commits at lists.llvm.org
Sun Nov 14 14:53:20 PST 2021


Author: Lang Hames
Date: 2021-11-14T14:44:07-08:00
New Revision: 69be352a1961ac3a51fcd87e461a70b926639613

URL: https://github.com/llvm/llvm-project/commit/69be352a1961ac3a51fcd87e461a70b926639613
DIFF: https://github.com/llvm/llvm-project/commit/69be352a1961ac3a51fcd87e461a70b926639613.diff

LOG: Reapply "[ORC] Initial MachO debugging support (via GDB JIT debug.." with fixes.

This reapplies e1933a0488a50eb939210808fc895d374570d891 (which was reverted in
f55ba3525eb19baed7d3f23638cbbd880246a370 due to bot failures, e.g.
https://lab.llvm.org/buildbot/#/builders/117/builds/2768).

The bot failures were due to a missing symbol error: We use the input object's
mangling to decide how to mangle the debug-info registration function name. This
caused lookup of the registration function to fail when the input object
mangling didn't match the host mangling.

Disbaling the test on non-Darwin platforms is the easiest short-term solution.
I have filed https://llvm.org/PR52503 with a proposed longer term solution.

Added: 
    llvm/include/llvm/ExecutionEngine/Orc/DebuggerSupportPlugin.h
    llvm/lib/ExecutionEngine/Orc/DebuggerSupportPlugin.cpp
    llvm/test/ExecutionEngine/JITLink/X86/MachO_gdb_jit_debuginfo_register.s

Modified: 
    llvm/include/llvm/ExecutionEngine/JITLink/JITLink.h
    llvm/lib/ExecutionEngine/JITLink/JITLinkMemoryManager.cpp
    llvm/lib/ExecutionEngine/JITLink/MachOLinkGraphBuilder.cpp
    llvm/lib/ExecutionEngine/Orc/CMakeLists.txt
    llvm/lib/ExecutionEngine/Orc/TargetProcess/JITLoaderGDB.cpp
    llvm/tools/llvm-jitlink/llvm-jitlink.cpp

Removed: 
    llvm/test/ExecutionEngine/JITLink/X86/MachO_skip_debug_sections.s


################################################################################
diff  --git a/llvm/include/llvm/ExecutionEngine/JITLink/JITLink.h b/llvm/include/llvm/ExecutionEngine/JITLink/JITLink.h
index 4a5d18437e39e..a9a54e59ef51d 100644
--- a/llvm/include/llvm/ExecutionEngine/JITLink/JITLink.h
+++ b/llvm/include/llvm/ExecutionEngine/JITLink/JITLink.h
@@ -343,6 +343,12 @@ class Block : public Addressable {
   std::vector<Edge> Edges;
 };
 
+// Align a JITTargetAddress to conform with block alignment requirements.
+inline JITTargetAddress alignToBlock(JITTargetAddress Addr, Block &B) {
+  uint64_t Delta = (B.getAlignmentOffset() - Addr) % B.getAlignment();
+  return Addr + Delta;
+}
+
 /// Describes symbol linkage. This can be used to make resolve definition
 /// clashes.
 enum class Linkage : uint8_t {

diff  --git a/llvm/include/llvm/ExecutionEngine/Orc/DebuggerSupportPlugin.h b/llvm/include/llvm/ExecutionEngine/Orc/DebuggerSupportPlugin.h
new file mode 100644
index 0000000000000..af092b3287d35
--- /dev/null
+++ b/llvm/include/llvm/ExecutionEngine/Orc/DebuggerSupportPlugin.h
@@ -0,0 +1,64 @@
+//===--- DebugerSupportPlugin.h -- Utils for debugger support ---*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Generates debug objects and registers them using the jit-loader-gdb protocol.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_ORC_DEBUGGERSUPPORT_H
+#define LLVM_EXECUTIONENGINE_ORC_DEBUGGERSUPPORT_H
+
+#include "llvm/ExecutionEngine/Orc/Core.h"
+#include "llvm/ExecutionEngine/Orc/EPCDebugObjectRegistrar.h"
+#include "llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h"
+
+namespace llvm {
+namespace orc {
+
+/// For each object containing debug info, installs JITLink passes to synthesize
+/// a debug object and then register it via the GDB JIT-registration interface.
+///
+/// Currently MachO only. For ELF use DebugObjectManagerPlugin. These two
+/// plugins will be merged in the near future.
+class GDBJITDebugInfoRegistrationPlugin : public ObjectLinkingLayer::Plugin {
+public:
+  class DebugSectionSynthesizer {
+  public:
+    virtual ~DebugSectionSynthesizer() {}
+    virtual Error startSynthesis() = 0;
+    virtual Error completeSynthesisAndRegister() = 0;
+  };
+
+  static Expected<std::unique_ptr<GDBJITDebugInfoRegistrationPlugin>>
+  Create(ExecutionSession &ES, JITDylib &ProcessJD, const Triple &TT);
+
+  GDBJITDebugInfoRegistrationPlugin(ExecutorAddr RegisterActionAddr)
+      : RegisterActionAddr(RegisterActionAddr) {}
+
+  Error notifyFailed(MaterializationResponsibility &MR) override;
+  Error notifyRemovingResources(ResourceKey K) override;
+
+  void notifyTransferringResources(ResourceKey DstKey,
+                                   ResourceKey SrcKey) override;
+
+  void modifyPassConfig(MaterializationResponsibility &MR,
+                        jitlink::LinkGraph &LG,
+                        jitlink::PassConfiguration &PassConfig) override;
+
+private:
+  void modifyPassConfigForMachO(MaterializationResponsibility &MR,
+                                jitlink::LinkGraph &LG,
+                                jitlink::PassConfiguration &PassConfig);
+
+  ExecutorAddr RegisterActionAddr;
+};
+
+} // namespace orc
+} // namespace llvm
+
+#endif // LLVM_EXECUTIONENGINE_ORC_DEBUGGERSUPPORT_H

diff  --git a/llvm/lib/ExecutionEngine/JITLink/JITLinkMemoryManager.cpp b/llvm/lib/ExecutionEngine/JITLink/JITLinkMemoryManager.cpp
index 4fb349255f75c..831b9b26d2fde 100644
--- a/llvm/lib/ExecutionEngine/JITLink/JITLinkMemoryManager.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/JITLinkMemoryManager.cpp
@@ -72,12 +72,6 @@ static Error runAllocAction(JITLinkMemoryManager::AllocActionCall &C) {
                     static_cast<size_t>(C.CtxSize)));
 }
 
-// Align a JITTargetAddress to conform with block alignment requirements.
-static JITTargetAddress alignToBlock(JITTargetAddress Addr, Block &B) {
-  uint64_t Delta = (B.getAlignmentOffset() - Addr) % B.getAlignment();
-  return Addr + Delta;
-}
-
 BasicLayout::BasicLayout(LinkGraph &G) : G(G) {
 
   for (auto &Sec : G.sections()) {

diff  --git a/llvm/lib/ExecutionEngine/JITLink/MachOLinkGraphBuilder.cpp b/llvm/lib/ExecutionEngine/JITLink/MachOLinkGraphBuilder.cpp
index 438a23830efd8..01f2ae76785a6 100644
--- a/llvm/lib/ExecutionEngine/JITLink/MachOLinkGraphBuilder.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/MachOLinkGraphBuilder.cpp
@@ -180,17 +180,10 @@ Error MachOLinkGraphBuilder::createNormalizedSections() {
     else
       Prot = MemProt::Read | MemProt::Write;
 
-    if (!isDebugSection(NSec)) {
-      auto FullyQualifiedName =
-          G->allocateString(StringRef(NSec.SegName) + "," + NSec.SectName);
-      NSec.GraphSection = &G->createSection(
-          StringRef(FullyQualifiedName.data(), FullyQualifiedName.size()),
-          Prot);
-    } else
-      LLVM_DEBUG({
-        dbgs() << "    " << NSec.SegName << "," << NSec.SectName
-               << " is a debug section: No graph section will be created.\n";
-      });
+    auto FullyQualifiedName =
+        G->allocateString(StringRef(NSec.SegName) + "," + NSec.SectName);
+    NSec.GraphSection = &G->createSection(
+        StringRef(FullyQualifiedName.data(), FullyQualifiedName.size()), Prot);
 
     IndexToSection.insert(std::make_pair(SecIndex, std::move(NSec)));
   }

diff  --git a/llvm/lib/ExecutionEngine/Orc/CMakeLists.txt b/llvm/lib/ExecutionEngine/Orc/CMakeLists.txt
index 60e7751dc9680..0c503d7ce20f9 100644
--- a/llvm/lib/ExecutionEngine/Orc/CMakeLists.txt
+++ b/llvm/lib/ExecutionEngine/Orc/CMakeLists.txt
@@ -3,6 +3,7 @@ add_llvm_component_library(LLVMOrcJIT
   CompileUtils.cpp
   Core.cpp
   DebugObjectManagerPlugin.cpp
+  DebuggerSupportPlugin.cpp
   DebugUtils.cpp
   EPCDynamicLibrarySearchGenerator.cpp
   EPCDebugObjectRegistrar.cpp

diff  --git a/llvm/lib/ExecutionEngine/Orc/DebuggerSupportPlugin.cpp b/llvm/lib/ExecutionEngine/Orc/DebuggerSupportPlugin.cpp
new file mode 100644
index 0000000000000..8479495623b8d
--- /dev/null
+++ b/llvm/lib/ExecutionEngine/Orc/DebuggerSupportPlugin.cpp
@@ -0,0 +1,450 @@
+//===------- 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/DebuggerSupportPlugin.h"
+
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringSet.h"
+#include "llvm/BinaryFormat/MachO.h"
+
+#define DEBUG_TYPE "orc"
+
+using namespace llvm;
+using namespace llvm::jitlink;
+using namespace llvm::orc;
+
+static const char *SynthDebugSectionName = "__jitlink_synth_debug_object";
+
+namespace {
+
+struct MachO64LE {
+  using UIntPtr = uint64_t;
+
+  using Header = MachO::mach_header_64;
+  using SegmentLC = MachO::segment_command_64;
+  using Section = MachO::section_64;
+  using NList = MachO::nlist_64;
+
+  static constexpr support::endianness Endianness = support::little;
+  static constexpr const uint32_t Magic = MachO::MH_MAGIC_64;
+  static constexpr const uint32_t SegmentCmd = MachO::LC_SEGMENT_64;
+};
+
+class MachODebugObjectSynthesizerBase
+    : public GDBJITDebugInfoRegistrationPlugin::DebugSectionSynthesizer {
+public:
+  static bool isDebugSection(Section &Sec) {
+    return Sec.getName().startswith("__DWARF,");
+  }
+
+  MachODebugObjectSynthesizerBase(LinkGraph &G, ExecutorAddr RegisterActionAddr)
+      : G(G), RegisterActionAddr(RegisterActionAddr) {}
+  virtual ~MachODebugObjectSynthesizerBase() {}
+
+  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 {
+private:
+  class MachOStructWriter {
+  public:
+    MachOStructWriter(MutableArrayRef<char> Buffer) : Buffer(Buffer) {}
+
+    size_t getOffset() const { return Offset; }
+
+    template <typename MachOStruct> void write(MachOStruct S) {
+      assert(Offset + sizeof(S) <= Buffer.size() &&
+             "Container block overflow while constructing debug MachO");
+      if (MachOTraits::Endianness != support::endian::system_endianness())
+        MachO::swapStruct(S);
+      memcpy(Buffer.data() + Offset, &S, sizeof(S));
+      Offset += sizeof(S);
+    }
+
+  private:
+    MutableArrayRef<char> Buffer;
+    size_t Offset = 0;
+  };
+
+public:
+  using MachODebugObjectSynthesizerBase::MachODebugObjectSynthesizerBase;
+
+  Error startSynthesis() override {
+    LLVM_DEBUG({
+      dbgs() << "Creating " << SynthDebugSectionName << " for " << G.getName()
+             << "\n";
+    });
+    auto &SDOSec = G.createSection(SynthDebugSectionName, MemProt::Read);
+
+    struct DebugSectionInfo {
+      Section *Sec = nullptr;
+      StringRef SegName;
+      StringRef SecName;
+      JITTargetAddress Alignment = 0;
+      JITTargetAddress StartAddr = 0;
+      uint64_t Size = 0;
+    };
+
+    SmallVector<DebugSectionInfo, 12> DebugSecInfos;
+    size_t NumSections = 0;
+    for (auto &Sec : G.sections()) {
+      if (llvm::empty(Sec.blocks()))
+        continue;
+
+      ++NumSections;
+      if (isDebugSection(Sec)) {
+        size_t SepPos = Sec.getName().find(',');
+        if (SepPos > 16 || (Sec.getName().size() - (SepPos + 1) > 16)) {
+          LLVM_DEBUG({
+            dbgs() << "Skipping debug object synthesis for graph "
+                   << G.getName()
+                   << ": encountered non-standard DWARF section name \""
+                   << Sec.getName() << "\"\n";
+          });
+          return Error::success();
+        }
+        DebugSecInfos.push_back({&Sec, Sec.getName().substr(0, SepPos),
+                                 Sec.getName().substr(SepPos + 1), 0, 0});
+      } else
+        NonDebugSections.push_back(&Sec);
+    }
+
+    // Create container block.
+    size_t SectionsCmdSize =
+        sizeof(typename MachOTraits::Section) * NumSections;
+    size_t SegmentLCSize =
+        sizeof(typename MachOTraits::SegmentLC) + SectionsCmdSize;
+    size_t ContainerBlockSize =
+        sizeof(typename MachOTraits::Header) + SegmentLCSize;
+    auto ContainerBlockContent = G.allocateBuffer(ContainerBlockSize);
+    MachOContainerBlock =
+        &G.createMutableContentBlock(SDOSec, ContainerBlockContent, 0, 8, 0);
+
+    // Copy debug section blocks and symbols.
+    JITTargetAddress NextBlockAddr = MachOContainerBlock->getSize();
+    for (auto &SI : DebugSecInfos) {
+      assert(!llvm::empty(SI.Sec->blocks()) && "Empty debug info section?");
+
+      // Update addresses in debug section.
+      LLVM_DEBUG({
+        dbgs() << "  Appending " << SI.Sec->getName() << " ("
+               << SI.Sec->blocks_size() << " block(s)) at "
+               << formatv("{0:x8}", NextBlockAddr) << "\n";
+      });
+      for (auto *B : SI.Sec->blocks()) {
+        NextBlockAddr = alignToBlock(NextBlockAddr, *B);
+        B->setAddress(NextBlockAddr);
+        NextBlockAddr += B->getSize();
+      }
+
+      auto &FirstBlock = **SI.Sec->blocks().begin();
+      if (FirstBlock.getAlignmentOffset() != 0)
+        return make_error<StringError>(
+            "First block in " + SI.Sec->getName() +
+                " section has non-zero alignment offset",
+            inconvertibleErrorCode());
+      if (FirstBlock.getAlignment() > std::numeric_limits<uint32_t>::max())
+        return make_error<StringError>("First block in " + SI.Sec->getName() +
+                                           " has alignment >4Gb",
+                                       inconvertibleErrorCode());
+
+      SI.Alignment = FirstBlock.getAlignment();
+      SI.StartAddr = FirstBlock.getAddress();
+      SI.Size = NextBlockAddr - SI.StartAddr;
+      G.mergeSections(SDOSec, *SI.Sec);
+      SI.Sec = nullptr;
+    }
+    size_t DebugSectionsSize = NextBlockAddr - MachOContainerBlock->getSize();
+
+    // Write MachO header and debug section load commands.
+    MachOStructWriter Writer(MachOContainerBlock->getAlreadyMutableContent());
+    typename MachOTraits::Header Hdr;
+    memset(&Hdr, 0, sizeof(Hdr));
+    Hdr.magic = MachOTraits::Magic;
+    switch (G.getTargetTriple().getArch()) {
+    case Triple::x86_64:
+      Hdr.cputype = MachO::CPU_TYPE_X86_64;
+      Hdr.cpusubtype = MachO::CPU_SUBTYPE_X86_64_ALL;
+      break;
+    case Triple::aarch64:
+      Hdr.cputype = MachO::CPU_TYPE_ARM64;
+      Hdr.cpusubtype = MachO::CPU_SUBTYPE_ARM64_ALL;
+      break;
+    default:
+      llvm_unreachable("Unsupported architecture");
+    }
+    Hdr.filetype = MachO::MH_OBJECT;
+    Hdr.ncmds = 1;
+    Hdr.sizeofcmds = SegmentLCSize;
+    Hdr.flags = 0;
+    Writer.write(Hdr);
+
+    typename MachOTraits::SegmentLC SegLC;
+    memset(&SegLC, 0, sizeof(SegLC));
+    SegLC.cmd = MachOTraits::SegmentCmd;
+    SegLC.cmdsize = SegmentLCSize;
+    SegLC.vmaddr = ContainerBlockSize;
+    SegLC.vmsize = DebugSectionsSize;
+    SegLC.fileoff = ContainerBlockSize;
+    SegLC.filesize = DebugSectionsSize;
+    SegLC.maxprot =
+        MachO::VM_PROT_READ | MachO::VM_PROT_WRITE | MachO::VM_PROT_EXECUTE;
+    SegLC.initprot =
+        MachO::VM_PROT_READ | MachO::VM_PROT_WRITE | MachO::VM_PROT_EXECUTE;
+    SegLC.nsects = NumSections;
+    SegLC.flags = 0;
+    Writer.write(SegLC);
+
+    StringSet<> ExistingLongNames;
+    for (auto &SI : DebugSecInfos) {
+      typename MachOTraits::Section Sec;
+      memset(&Sec, 0, sizeof(Sec));
+      memcpy(Sec.sectname, SI.SecName.data(), SI.SecName.size());
+      memcpy(Sec.segname, SI.SegName.data(), SI.SegName.size());
+      Sec.addr = SI.StartAddr;
+      Sec.size = SI.Size;
+      Sec.offset = SI.StartAddr;
+      Sec.align = SI.Alignment;
+      Sec.reloff = 0;
+      Sec.nreloc = 0;
+      Sec.flags = MachO::S_ATTR_DEBUG;
+      Writer.write(Sec);
+    }
+
+    // Set MachOContainerBlock to indicate success to
+    // completeSynthesisAndRegister.
+    NonDebugSectionsStart = Writer.getOffset();
+    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();
+    }
+
+    LLVM_DEBUG({
+      dbgs() << "Writing MachO debug object header for " << G.getName() << "\n";
+    });
+
+    MachOStructWriter Writer(
+        MachOContainerBlock->getAlreadyMutableContent().drop_front(
+            NonDebugSectionsStart));
+
+    unsigned LongSectionNameIdx = 0;
+    for (auto *Sec : NonDebugSections) {
+      size_t SepPos = Sec->getName().find(',');
+      StringRef SegName, SecName;
+      std::string CustomSecName;
+
+      if ((SepPos == StringRef::npos && Sec->getName().size() <= 16)) {
+        // No embedded segment name, short section name.
+        SegName = "__JITLINK_CUSTOM";
+        SecName = Sec->getName();
+      } else if (SepPos < 16 && (Sec->getName().size() - (SepPos + 1) <= 16)) {
+        // Canonical embedded segment and section name.
+        SegName = Sec->getName().substr(0, SepPos);
+        SecName = Sec->getName().substr(SepPos + 1);
+      } else {
+        // Long section name that needs to be truncated.
+        assert(Sec->getName().size() > 16 &&
+               "Short section name should have been handled above");
+        SegName = "__JITLINK_CUSTOM";
+        auto IdxStr = std::to_string(++LongSectionNameIdx);
+        CustomSecName = Sec->getName().substr(0, 15 - IdxStr.size()).str();
+        CustomSecName += ".";
+        CustomSecName += IdxStr;
+        SecName = StringRef(CustomSecName.data(), 16);
+      }
+
+      SectionRange R(*Sec);
+      if (R.getFirstBlock()->getAlignmentOffset() != 0)
+        return make_error<StringError>(
+            "While building MachO debug object for " + G.getName() +
+                " first block has non-zero alignment offset",
+            inconvertibleErrorCode());
+
+      typename MachOTraits::Section SecCmd;
+      memset(&SecCmd, 0, sizeof(SecCmd));
+      memcpy(SecCmd.sectname, SecName.data(), SecName.size());
+      memcpy(SecCmd.segname, SegName.data(), SegName.size());
+      SecCmd.addr = R.getStart();
+      SecCmd.size = R.getSize();
+      SecCmd.offset = 0;
+      SecCmd.align = R.getFirstBlock()->getAlignment();
+      SecCmd.reloff = 0;
+      SecCmd.nreloc = 0;
+      SecCmd.flags = 0;
+      Writer.write(SecCmd);
+    }
+
+    SectionRange R(MachOContainerBlock->getSection());
+    G.allocActions().push_back(
+        {{RegisterActionAddr.getValue(), R.getStart(), R.getSize()}, {}});
+    return Error::success();
+  }
+
+private:
+  Block *MachOContainerBlock = nullptr;
+  SmallVector<Section *, 16> NonDebugSections;
+  size_t NonDebugSectionsStart = 0;
+};
+
+} // 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 Addr = ES.lookup({&ProcessJD}, RegisterActionAddr))
+    return std::make_unique<GDBJITDebugInfoRegistrationPlugin>(
+        ExecutorAddr(Addr->getAddress()));
+  else
+    return Addr.takeError();
+}
+
+Error GDBJITDebugInfoRegistrationPlugin::notifyFailed(
+    MaterializationResponsibility &MR) {
+  return Error::success();
+}
+
+Error GDBJITDebugInfoRegistrationPlugin::notifyRemovingResources(
+    ResourceKey K) {
+  return Error::success();
+}
+
+void GDBJITDebugInfoRegistrationPlugin::notifyTransferringResources(
+    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() == support::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() == support::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>>(
+        LG, RegisterActionAddr);
+    PassConfig.PrePrunePasses.push_back(
+        [=](LinkGraph &G) { return MDOS->preserveDebugSections(); });
+    PassConfig.PostPrunePasses.push_back(
+        [=](LinkGraph &G) { return MDOS->startSynthesis(); });
+    PassConfig.PreFixupPasses.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

diff  --git a/llvm/lib/ExecutionEngine/Orc/TargetProcess/JITLoaderGDB.cpp b/llvm/lib/ExecutionEngine/Orc/TargetProcess/JITLoaderGDB.cpp
index e12a800f06668..4c15e25b1d898 100644
--- a/llvm/lib/ExecutionEngine/Orc/TargetProcess/JITLoaderGDB.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/TargetProcess/JITLoaderGDB.cpp
@@ -10,6 +10,7 @@
 
 #include "llvm/ExecutionEngine/JITSymbol.h"
 #include "llvm/Support/BinaryStreamReader.h"
+#include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/ManagedStatic.h"
 
 #include <cstdint>
@@ -70,10 +71,18 @@ using namespace llvm::orc;
 ManagedStatic<std::mutex> JITDebugLock;
 
 // Register debug object, return error message or null for success.
-static void registerJITLoaderGDBImpl(ExecutorAddrRange DebugObjRange) {
+static void registerJITLoaderGDBImpl(const char *ObjAddr, size_t Size) {
+  LLVM_DEBUG({
+    dbgs() << "Registering debug object with GDB JIT interface "
+           << formatv("([{0:x16} -- {1:x16}])",
+                      reinterpret_cast<uintptr_t>(ObjAddr),
+                      reinterpret_cast<uintptr_t>(ObjAddr + Size))
+           << "\n";
+  });
+
   jit_code_entry *E = new jit_code_entry;
-  E->symfile_addr = DebugObjRange.Start.toPtr<const char *>();
-  E->symfile_size = DebugObjRange.size().getValue();
+  E->symfile_addr = ObjAddr;
+  E->symfile_size = Size;
   E->prev_entry = nullptr;
 
   std::lock_guard<std::mutex> Lock(*JITDebugLock);
@@ -93,10 +102,26 @@ static void registerJITLoaderGDBImpl(ExecutorAddrRange DebugObjRange) {
   __jit_debug_register_code();
 }
 
+extern "C" orc::shared::CWrapperFunctionResult
+llvm_orc_registerJITLoaderGDBAllocAction(const char *Data, size_t Size) {
+  using namespace orc::shared;
+  return WrapperFunction<SPSError()>::handle(nullptr, 0,
+                                             [=]() -> Error {
+                                               registerJITLoaderGDBImpl(Data,
+                                                                        Size);
+                                               return Error::success();
+                                             })
+      .release();
+}
+
 extern "C" orc::shared::CWrapperFunctionResult
 llvm_orc_registerJITLoaderGDBWrapper(const char *Data, uint64_t Size) {
   using namespace orc::shared;
   return WrapperFunction<void(SPSExecutorAddrRange)>::handle(
-             Data, Size, registerJITLoaderGDBImpl)
+             Data, Size,
+             [](ExecutorAddrRange R) {
+               registerJITLoaderGDBImpl(R.Start.toPtr<char *>(),
+                                        R.size().getValue());
+             })
       .release();
 }

diff  --git a/llvm/test/ExecutionEngine/JITLink/X86/MachO_gdb_jit_debuginfo_register.s b/llvm/test/ExecutionEngine/JITLink/X86/MachO_gdb_jit_debuginfo_register.s
new file mode 100644
index 0000000000000..968b7c9794c94
--- /dev/null
+++ b/llvm/test/ExecutionEngine/JITLink/X86/MachO_gdb_jit_debuginfo_register.s
@@ -0,0 +1,27 @@
+# REQUIRES: system-darwin && asserts
+# RUN: llvm-mc -triple=x86_64-apple-macosx10.9 -filetype=obj -o %t %s
+# RUN: llvm-jitlink -debug-only=orc -noexec %t 2>&1 | FileCheck %s
+#
+# Check that presence of a "__DWARF" section triggers the
+# GDBJITDebugInfoRegistrationPlugin.
+#
+# This test requires a darwin host (despite being a noexec test) because we use
+# the input object's mangling to determine the mangling of the registration
+# function to use. Since the input is MachO, the mangling will only line up
+# properly on Darwin. (See https://llvm.org/PR52503 for a proposed longer term
+# solution).
+#
+# CHECK: Registering debug object with GDB JIT interface
+
+	.section	__TEXT,__text,regular,pure_instructions
+	.globl	_main
+	.p2align	4, 0x90
+_main:
+	xorl	%eax, %eax
+	retq
+
+	.section	__DWARF,__debug_str,regular,debug
+Linfo_string:
+	.asciz	"test dwarf string"
+
+.subsections_via_symbols

diff  --git a/llvm/test/ExecutionEngine/JITLink/X86/MachO_skip_debug_sections.s b/llvm/test/ExecutionEngine/JITLink/X86/MachO_skip_debug_sections.s
deleted file mode 100644
index 4d43ade6f3b7f..0000000000000
--- a/llvm/test/ExecutionEngine/JITLink/X86/MachO_skip_debug_sections.s
+++ /dev/null
@@ -1,21 +0,0 @@
-# REQUIRES: asserts
-# RUN: llvm-mc -triple=x86_64-apple-macosx10.9 -filetype=obj -o %t %s
-# RUN: llvm-jitlink -debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
-#
-# Check that debug sections are not emitted, and consequently that we don't
-# error out due to buggy past-the-end anonymous relocations in __debug_ranges.
-#
-# CHECK: __debug_ranges is a debug section: No graph section will be created.
-  .section	__TEXT,__text,regular,pure_instructions
-  .macosx_version_min 10, 15
-	.globl	_main
-	.p2align	4, 0x90
-_main:
-	retq
-Lpast_the_end:
-
-	.section	__DWARF,__debug_ranges
-	.p2align	4
-	.quad	Lpast_the_end
-
-.subsections_via_symbols

diff  --git a/llvm/tools/llvm-jitlink/llvm-jitlink.cpp b/llvm/tools/llvm-jitlink/llvm-jitlink.cpp
index f3486868c514a..81c1e94b6b135 100644
--- a/llvm/tools/llvm-jitlink/llvm-jitlink.cpp
+++ b/llvm/tools/llvm-jitlink/llvm-jitlink.cpp
@@ -16,6 +16,7 @@
 
 #include "llvm/BinaryFormat/Magic.h"
 #include "llvm/ExecutionEngine/Orc/DebugObjectManagerPlugin.h"
+#include "llvm/ExecutionEngine/Orc/DebuggerSupportPlugin.h"
 #include "llvm/ExecutionEngine/Orc/ELFNixPlatform.h"
 #include "llvm/ExecutionEngine/Orc/EPCDebugObjectRegistrar.h"
 #include "llvm/ExecutionEngine/Orc/EPCDynamicLibrarySearchGenerator.h"
@@ -987,8 +988,13 @@ Session::Session(std::unique_ptr<ExecutorProcessControl> EPC, Error &Err)
     ExitOnErr(loadProcessSymbols(*this));
   ExitOnErr(loadDylibs(*this));
 
-  // Set up the platform.
   auto &TT = ES.getExecutorProcessControl().getTargetTriple();
+
+  if (TT.isOSBinFormatMachO())
+    ObjLayer.addPlugin(ExitOnErr(
+        GDBJITDebugInfoRegistrationPlugin::Create(this->ES, *MainJD, TT)));
+
+  // Set up the platform.
   if (TT.isOSBinFormatMachO() && !OrcRuntime.empty()) {
     if (auto P =
             MachOPlatform::Create(ES, ObjLayer, *MainJD, OrcRuntime.c_str()))


        


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