gdb-jit.cc 62.3 KB
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// Copyright 2010 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
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#include "src/gdb-jit.h"
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#include <memory>
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#include <vector>
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#include "src/api-inl.h"
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#include "src/base/bits.h"
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#include "src/base/platform/platform.h"
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#include "src/bootstrapper.h"
#include "src/frames-inl.h"
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#include "src/frames.h"
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#include "src/global-handles.h"
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#include "src/objects.h"
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#include "src/ostreams.h"
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#include "src/snapshot/natives.h"
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#include "src/splay-tree-inl.h"
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#include "src/zone/zone-chunk-list.h"
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namespace v8 {
namespace internal {
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namespace GDBJITInterface {

#ifdef ENABLE_GDB_JIT_INTERFACE
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#ifdef __APPLE__
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#define __MACH_O
class MachO;
class MachOSection;
typedef MachO DebugObject;
typedef MachOSection DebugSection;
#else
#define __ELF
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class ELF;
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class ELFSection;
typedef ELF DebugObject;
typedef ELFSection DebugSection;
#endif
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class Writer {
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 public:
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  explicit Writer(DebugObject* debug_object)
      : debug_object_(debug_object),
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        position_(0),
        capacity_(1024),
        buffer_(reinterpret_cast<byte*>(malloc(capacity_))) {
  }

  ~Writer() {
    free(buffer_);
  }

  uintptr_t position() const {
    return position_;
  }

  template<typename T>
  class Slot {
   public:
    Slot(Writer* w, uintptr_t offset) : w_(w), offset_(offset) { }

    T* operator-> () {
      return w_->RawSlotAt<T>(offset_);
    }

    void set(const T& value) {
      *w_->RawSlotAt<T>(offset_) = value;
    }

    Slot<T> at(int i) {
      return Slot<T>(w_, offset_ + sizeof(T) * i);
    }

   private:
    Writer* w_;
    uintptr_t offset_;
  };

  template<typename T>
  void Write(const T& val) {
    Ensure(position_ + sizeof(T));
    *RawSlotAt<T>(position_) = val;
    position_ += sizeof(T);
  }

  template<typename T>
  Slot<T> SlotAt(uintptr_t offset) {
    Ensure(offset + sizeof(T));
    return Slot<T>(this, offset);
  }

  template<typename T>
  Slot<T> CreateSlotHere() {
    return CreateSlotsHere<T>(1);
  }

  template<typename T>
  Slot<T> CreateSlotsHere(uint32_t count) {
    uintptr_t slot_position = position_;
    position_ += sizeof(T) * count;
    Ensure(position_);
    return SlotAt<T>(slot_position);
  }

  void Ensure(uintptr_t pos) {
    if (capacity_ < pos) {
      while (capacity_ < pos) capacity_ *= 2;
      buffer_ = reinterpret_cast<byte*>(realloc(buffer_, capacity_));
    }
  }

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  DebugObject* debug_object() { return debug_object_; }
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  byte* buffer() { return buffer_; }

  void Align(uintptr_t align) {
    uintptr_t delta = position_ % align;
    if (delta == 0) return;
    uintptr_t padding = align - delta;
    Ensure(position_ += padding);
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    DCHECK_EQ(position_ % align, 0);
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  }

  void WriteULEB128(uintptr_t value) {
    do {
      uint8_t byte = value & 0x7F;
      value >>= 7;
      if (value != 0) byte |= 0x80;
      Write<uint8_t>(byte);
    } while (value != 0);
  }

  void WriteSLEB128(intptr_t value) {
    bool more = true;
    while (more) {
      int8_t byte = value & 0x7F;
      bool byte_sign = byte & 0x40;
      value >>= 7;

      if ((value == 0 && !byte_sign) || (value == -1 && byte_sign)) {
        more = false;
      } else {
        byte |= 0x80;
      }

      Write<int8_t>(byte);
    }
  }

  void WriteString(const char* str) {
    do {
      Write<char>(*str);
    } while (*str++);
  }

 private:
  template<typename T> friend class Slot;

  template<typename T>
  T* RawSlotAt(uintptr_t offset) {
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    DCHECK(offset < capacity_ && offset + sizeof(T) <= capacity_);
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    return reinterpret_cast<T*>(&buffer_[offset]);
  }

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  DebugObject* debug_object_;
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  uintptr_t position_;
  uintptr_t capacity_;
  byte* buffer_;
};

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class ELFStringTable;
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template<typename THeader>
class DebugSectionBase : public ZoneObject {
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 public:
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  virtual ~DebugSectionBase() = default;
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  virtual void WriteBody(Writer::Slot<THeader> header, Writer* writer) {
    uintptr_t start = writer->position();
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    if (WriteBodyInternal(writer)) {
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      uintptr_t end = writer->position();
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      header->offset = static_cast<uint32_t>(start);
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#if defined(__MACH_O)
      header->addr = 0;
#endif
      header->size = end - start;
    }
  }

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  virtual bool WriteBodyInternal(Writer* writer) {
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    return false;
  }

  typedef THeader Header;
};


struct MachOSectionHeader {
  char sectname[16];
  char segname[16];
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#if V8_TARGET_ARCH_IA32
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  uint32_t addr;
  uint32_t size;
#else
  uint64_t addr;
  uint64_t size;
#endif
  uint32_t offset;
  uint32_t align;
  uint32_t reloff;
  uint32_t nreloc;
  uint32_t flags;
  uint32_t reserved1;
  uint32_t reserved2;
};


class MachOSection : public DebugSectionBase<MachOSectionHeader> {
 public:
  enum Type {
    S_REGULAR = 0x0u,
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    S_ATTR_COALESCED = 0xBu,
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    S_ATTR_SOME_INSTRUCTIONS = 0x400u,
    S_ATTR_DEBUG = 0x02000000u,
    S_ATTR_PURE_INSTRUCTIONS = 0x80000000u
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  };

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  MachOSection(const char* name, const char* segment, uint32_t align,
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               uint32_t flags)
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      : name_(name), segment_(segment), align_(align), flags_(flags) {
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    if (align_ != 0) {
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      DCHECK(base::bits::IsPowerOfTwo(align));
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      align_ = WhichPowerOf2(align_);
    }
  }

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  ~MachOSection() override = default;
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  virtual void PopulateHeader(Writer::Slot<Header> header) {
    header->addr = 0;
    header->size = 0;
    header->offset = 0;
    header->align = align_;
    header->reloff = 0;
    header->nreloc = 0;
    header->flags = flags_;
    header->reserved1 = 0;
    header->reserved2 = 0;
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    memset(header->sectname, 0, sizeof(header->sectname));
    memset(header->segname, 0, sizeof(header->segname));
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    DCHECK(strlen(name_) < sizeof(header->sectname));
    DCHECK(strlen(segment_) < sizeof(header->segname));
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    strncpy(header->sectname, name_, sizeof(header->sectname));
    strncpy(header->segname, segment_, sizeof(header->segname));
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  }

 private:
  const char* name_;
  const char* segment_;
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  uint32_t align_;
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  uint32_t flags_;
};


struct ELFSectionHeader {
  uint32_t name;
  uint32_t type;
  uintptr_t flags;
  uintptr_t address;
  uintptr_t offset;
  uintptr_t size;
  uint32_t link;
  uint32_t info;
  uintptr_t alignment;
  uintptr_t entry_size;
};
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#if defined(__ELF)
class ELFSection : public DebugSectionBase<ELFSectionHeader> {
 public:
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  enum Type {
    TYPE_NULL = 0,
    TYPE_PROGBITS = 1,
    TYPE_SYMTAB = 2,
    TYPE_STRTAB = 3,
    TYPE_RELA = 4,
    TYPE_HASH = 5,
    TYPE_DYNAMIC = 6,
    TYPE_NOTE = 7,
    TYPE_NOBITS = 8,
    TYPE_REL = 9,
    TYPE_SHLIB = 10,
    TYPE_DYNSYM = 11,
    TYPE_LOPROC = 0x70000000,
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    TYPE_X86_64_UNWIND = 0x70000001,
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    TYPE_HIPROC = 0x7FFFFFFF,
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    TYPE_LOUSER = 0x80000000,
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    TYPE_HIUSER = 0xFFFFFFFF
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  };

  enum Flags {
    FLAG_WRITE = 1,
    FLAG_ALLOC = 2,
    FLAG_EXEC = 4
  };

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  enum SpecialIndexes { INDEX_ABSOLUTE = 0xFFF1 };
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  ELFSection(const char* name, Type type, uintptr_t align)
      : name_(name), type_(type), align_(align) { }

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  ~ELFSection() override = default;
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  void PopulateHeader(Writer::Slot<Header> header, ELFStringTable* strtab);
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  void WriteBody(Writer::Slot<Header> header, Writer* w) override {
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    uintptr_t start = w->position();
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    if (WriteBodyInternal(w)) {
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      uintptr_t end = w->position();
      header->offset = start;
      header->size = end - start;
    }
  }

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  bool WriteBodyInternal(Writer* w) override { return false; }
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  uint16_t index() const { return index_; }
  void set_index(uint16_t index) { index_ = index; }

 protected:
  virtual void PopulateHeader(Writer::Slot<Header> header) {
    header->flags = 0;
    header->address = 0;
    header->offset = 0;
    header->size = 0;
    header->link = 0;
    header->info = 0;
    header->entry_size = 0;
  }

 private:
  const char* name_;
  Type type_;
  uintptr_t align_;
  uint16_t index_;
};
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#endif  // defined(__ELF)
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#if defined(__MACH_O)
class MachOTextSection : public MachOSection {
 public:
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  MachOTextSection(uint32_t align, uintptr_t addr, uintptr_t size)
      : MachOSection("__text", "__TEXT", align,
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                     MachOSection::S_REGULAR |
                         MachOSection::S_ATTR_SOME_INSTRUCTIONS |
                         MachOSection::S_ATTR_PURE_INSTRUCTIONS),
        addr_(addr),
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        size_(size) {}
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 protected:
  virtual void PopulateHeader(Writer::Slot<Header> header) {
    MachOSection::PopulateHeader(header);
    header->addr = addr_;
    header->size = size_;
  }

 private:
  uintptr_t addr_;
  uintptr_t size_;
};
#endif  // defined(__MACH_O)


#if defined(__ELF)
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class FullHeaderELFSection : public ELFSection {
 public:
  FullHeaderELFSection(const char* name,
                       Type type,
                       uintptr_t align,
                       uintptr_t addr,
                       uintptr_t offset,
                       uintptr_t size,
                       uintptr_t flags)
      : ELFSection(name, type, align),
        addr_(addr),
        offset_(offset),
        size_(size),
        flags_(flags) { }

 protected:
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  void PopulateHeader(Writer::Slot<Header> header) override {
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    ELFSection::PopulateHeader(header);
    header->address = addr_;
    header->offset = offset_;
    header->size = size_;
    header->flags = flags_;
  }

 private:
  uintptr_t addr_;
  uintptr_t offset_;
  uintptr_t size_;
  uintptr_t flags_;
};


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class ELFStringTable : public ELFSection {
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 public:
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  explicit ELFStringTable(const char* name)
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      : ELFSection(name, TYPE_STRTAB, 1),
        writer_(nullptr),
        offset_(0),
        size_(0) {}
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  uintptr_t Add(const char* str) {
    if (*str == '\0') return 0;

    uintptr_t offset = size_;
    WriteString(str);
    return offset;
  }

  void AttachWriter(Writer* w) {
    writer_ = w;
    offset_ = writer_->position();

    // First entry in the string table should be an empty string.
    WriteString("");
  }

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  void DetachWriter() { writer_ = nullptr; }
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  void WriteBody(Writer::Slot<Header> header, Writer* w) override {
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    DCHECK_NULL(writer_);
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    header->offset = offset_;
    header->size = size_;
  }

 private:
  void WriteString(const char* str) {
    uintptr_t written = 0;
    do {
      writer_->Write(*str);
      written++;
    } while (*str++);
    size_ += written;
  }

  Writer* writer_;

  uintptr_t offset_;
  uintptr_t size_;
};


void ELFSection::PopulateHeader(Writer::Slot<ELFSection::Header> header,
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                                ELFStringTable* strtab) {
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  header->name = static_cast<uint32_t>(strtab->Add(name_));
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  header->type = type_;
  header->alignment = align_;
  PopulateHeader(header);
}
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#endif  // defined(__ELF)


#if defined(__MACH_O)
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class MachO {
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 public:
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  explicit MachO(Zone* zone) : sections_(zone) {}
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  size_t AddSection(MachOSection* section) {
    sections_.push_back(section);
    return sections_.size() - 1;
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  }

  void Write(Writer* w, uintptr_t code_start, uintptr_t code_size) {
    Writer::Slot<MachOHeader> header = WriteHeader(w);
    uintptr_t load_command_start = w->position();
    Writer::Slot<MachOSegmentCommand> cmd = WriteSegmentCommand(w,
                                                                code_start,
                                                                code_size);
    WriteSections(w, cmd, header, load_command_start);
  }

 private:
  struct MachOHeader {
    uint32_t magic;
    uint32_t cputype;
    uint32_t cpusubtype;
    uint32_t filetype;
    uint32_t ncmds;
    uint32_t sizeofcmds;
    uint32_t flags;
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#if V8_TARGET_ARCH_X64
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    uint32_t reserved;
#endif
  };

  struct MachOSegmentCommand {
    uint32_t cmd;
    uint32_t cmdsize;
    char segname[16];
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#if V8_TARGET_ARCH_IA32
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    uint32_t vmaddr;
    uint32_t vmsize;
    uint32_t fileoff;
    uint32_t filesize;
#else
    uint64_t vmaddr;
    uint64_t vmsize;
    uint64_t fileoff;
    uint64_t filesize;
#endif
    uint32_t maxprot;
    uint32_t initprot;
    uint32_t nsects;
    uint32_t flags;
  };

  enum MachOLoadCommandCmd {
    LC_SEGMENT_32 = 0x00000001u,
    LC_SEGMENT_64 = 0x00000019u
  };


  Writer::Slot<MachOHeader> WriteHeader(Writer* w) {
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    DCHECK_EQ(w->position(), 0);
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    Writer::Slot<MachOHeader> header = w->CreateSlotHere<MachOHeader>();
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#if V8_TARGET_ARCH_IA32
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    header->magic = 0xFEEDFACEu;
    header->cputype = 7;  // i386
    header->cpusubtype = 3;  // CPU_SUBTYPE_I386_ALL
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#elif V8_TARGET_ARCH_X64
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    header->magic = 0xFEEDFACFu;
    header->cputype = 7 | 0x01000000;  // i386 | 64-bit ABI
    header->cpusubtype = 3;  // CPU_SUBTYPE_I386_ALL
    header->reserved = 0;
#else
#error Unsupported target architecture.
#endif
    header->filetype = 0x1;  // MH_OBJECT
    header->ncmds = 1;
    header->sizeofcmds = 0;
    header->flags = 0;
    return header;
  }
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  Writer::Slot<MachOSegmentCommand> WriteSegmentCommand(Writer* w,
                                                        uintptr_t code_start,
                                                        uintptr_t code_size) {
    Writer::Slot<MachOSegmentCommand> cmd =
        w->CreateSlotHere<MachOSegmentCommand>();
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#if V8_TARGET_ARCH_IA32
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    cmd->cmd = LC_SEGMENT_32;
#else
    cmd->cmd = LC_SEGMENT_64;
#endif
    cmd->vmaddr = code_start;
    cmd->vmsize = code_size;
    cmd->fileoff = 0;
    cmd->filesize = 0;
    cmd->maxprot = 7;
    cmd->initprot = 7;
    cmd->flags = 0;
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    cmd->nsects = static_cast<uint32_t>(sections_.size());
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    memset(cmd->segname, 0, 16);
    cmd->cmdsize = sizeof(MachOSegmentCommand) + sizeof(MachOSection::Header) *
        cmd->nsects;
    return cmd;
  }


  void WriteSections(Writer* w,
                     Writer::Slot<MachOSegmentCommand> cmd,
                     Writer::Slot<MachOHeader> header,
                     uintptr_t load_command_start) {
    Writer::Slot<MachOSection::Header> headers =
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        w->CreateSlotsHere<MachOSection::Header>(
            static_cast<uint32_t>(sections_.size()));
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    cmd->fileoff = w->position();
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    header->sizeofcmds =
        static_cast<uint32_t>(w->position() - load_command_start);
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    uint32_t index = 0;
    for (MachOSection* section : sections_) {
      section->PopulateHeader(headers.at(index));
      section->WriteBody(headers.at(index), w);
      index++;
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    }
    cmd->filesize = w->position() - (uintptr_t)cmd->fileoff;
  }

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  ZoneChunkList<MachOSection*> sections_;
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};
#endif  // defined(__MACH_O)


#if defined(__ELF)
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class ELF {
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 public:
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  explicit ELF(Zone* zone) : sections_(zone) {
    sections_.push_back(new (zone) ELFSection("", ELFSection::TYPE_NULL, 0));
    sections_.push_back(new (zone) ELFStringTable(".shstrtab"));
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  }

  void Write(Writer* w) {
    WriteHeader(w);
    WriteSectionTable(w);
    WriteSections(w);
  }

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  ELFSection* SectionAt(uint32_t index) { return *sections_.Find(index); }
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  size_t AddSection(ELFSection* section) {
    sections_.push_back(section);
    section->set_index(sections_.size() - 1);
    return sections_.size() - 1;
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  }

 private:
  struct ELFHeader {
    uint8_t ident[16];
    uint16_t type;
    uint16_t machine;
    uint32_t version;
    uintptr_t entry;
    uintptr_t pht_offset;
    uintptr_t sht_offset;
    uint32_t flags;
    uint16_t header_size;
    uint16_t pht_entry_size;
    uint16_t pht_entry_num;
    uint16_t sht_entry_size;
    uint16_t sht_entry_num;
    uint16_t sht_strtab_index;
  };


  void WriteHeader(Writer* w) {
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    DCHECK_EQ(w->position(), 0);
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    Writer::Slot<ELFHeader> header = w->CreateSlotHere<ELFHeader>();
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#if (V8_TARGET_ARCH_IA32 || V8_TARGET_ARCH_ARM)
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    const uint8_t ident[16] = {0x7F, 'E', 'L', 'F', 1, 1, 1, 0,
                               0,    0,   0,   0,   0, 0, 0, 0};
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#elif(V8_TARGET_ARCH_X64 && V8_TARGET_ARCH_64_BIT) || \
    (V8_TARGET_ARCH_PPC64 && V8_TARGET_LITTLE_ENDIAN)
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    const uint8_t ident[16] = {0x7F, 'E', 'L', 'F', 2, 1, 1, 0,
                               0,    0,   0,   0,   0, 0, 0, 0};
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#elif V8_TARGET_ARCH_PPC64 && V8_TARGET_BIG_ENDIAN && V8_OS_LINUX
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    const uint8_t ident[16] = {0x7F, 'E', 'L', 'F', 2, 2, 1, 0,
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                               0,    0,   0,   0,   0, 0, 0, 0};
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#elif V8_TARGET_ARCH_S390X
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    const uint8_t ident[16] = {0x7F, 'E', 'L', 'F', 2, 2, 1, 3,
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                               0,    0,   0,   0,   0, 0, 0, 0};
#elif V8_TARGET_ARCH_S390
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    const uint8_t ident[16] = {0x7F, 'E', 'L', 'F', 1, 2, 1, 3,
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                               0,    0,   0,   0,   0, 0, 0, 0};
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#else
#error Unsupported target architecture.
#endif
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    memcpy(header->ident, ident, 16);
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    header->type = 1;
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#if V8_TARGET_ARCH_IA32
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    header->machine = 3;
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#elif V8_TARGET_ARCH_X64
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    // Processor identification value for x64 is 62 as defined in
    //    System V ABI, AMD64 Supplement
    //    http://www.x86-64.org/documentation/abi.pdf
    header->machine = 62;
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#elif V8_TARGET_ARCH_ARM
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    // Set to EM_ARM, defined as 40, in "ARM ELF File Format" at
    // infocenter.arm.com/help/topic/com.arm.doc.dui0101a/DUI0101A_Elf.pdf
    header->machine = 40;
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#elif V8_TARGET_ARCH_PPC64 && V8_OS_LINUX
    // Set to EM_PPC64, defined as 21, in Power ABI,
    // Join the next 4 lines, omitting the spaces and double-slashes.
    // https://www-03.ibm.com/technologyconnect/tgcm/TGCMFileServlet.wss/
    // ABI64BitOpenPOWERv1.1_16July2015_pub.pdf?
    // id=B81AEC1A37F5DAF185257C3E004E8845&linkid=1n0000&c_t=
    // c9xw7v5dzsj7gt1ifgf4cjbcnskqptmr
    header->machine = 21;
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#elif V8_TARGET_ARCH_S390
    // Processor identification value is 22 (EM_S390) as defined in the ABI:
    // http://refspecs.linuxbase.org/ELF/zSeries/lzsabi0_s390.html#AEN1691
    // http://refspecs.linuxbase.org/ELF/zSeries/lzsabi0_zSeries.html#AEN1599
    header->machine = 22;
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#else
#error Unsupported target architecture.
#endif
    header->version = 1;
    header->entry = 0;
    header->pht_offset = 0;
    header->sht_offset = sizeof(ELFHeader);  // Section table follows header.
    header->flags = 0;
    header->header_size = sizeof(ELFHeader);
    header->pht_entry_size = 0;
    header->pht_entry_num = 0;
    header->sht_entry_size = sizeof(ELFSection::Header);
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    header->sht_entry_num = sections_.size();
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    header->sht_strtab_index = 1;
  }

  void WriteSectionTable(Writer* w) {
    // Section headers table immediately follows file header.
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    DCHECK(w->position() == sizeof(ELFHeader));
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    Writer::Slot<ELFSection::Header> headers =
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        w->CreateSlotsHere<ELFSection::Header>(
            static_cast<uint32_t>(sections_.size()));
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    // String table for section table is the first section.
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    ELFStringTable* strtab = static_cast<ELFStringTable*>(SectionAt(1));
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    strtab->AttachWriter(w);
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    uint32_t index = 0;
    for (ELFSection* section : sections_) {
      section->PopulateHeader(headers.at(index), strtab);
      index++;
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    }
    strtab->DetachWriter();
  }

  int SectionHeaderPosition(uint32_t section_index) {
    return sizeof(ELFHeader) + sizeof(ELFSection::Header) * section_index;
  }

  void WriteSections(Writer* w) {
    Writer::Slot<ELFSection::Header> headers =
        w->SlotAt<ELFSection::Header>(sizeof(ELFHeader));

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    uint32_t index = 0;
    for (ELFSection* section : sections_) {
      section->WriteBody(headers.at(index), w);
      index++;
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    }
  }

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  ZoneChunkList<ELFSection*> sections_;
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};

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class ELFSymbol {
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 public:
  enum Type {
    TYPE_NOTYPE = 0,
    TYPE_OBJECT = 1,
    TYPE_FUNC = 2,
    TYPE_SECTION = 3,
    TYPE_FILE = 4,
    TYPE_LOPROC = 13,
    TYPE_HIPROC = 15
  };

  enum Binding {
    BIND_LOCAL = 0,
    BIND_GLOBAL = 1,
    BIND_WEAK = 2,
    BIND_LOPROC = 13,
    BIND_HIPROC = 15
  };

  ELFSymbol(const char* name,
            uintptr_t value,
            uintptr_t size,
            Binding binding,
            Type type,
            uint16_t section)
      : name(name),
        value(value),
        size(size),
        info((binding << 4) | type),
        other(0),
        section(section) {
  }

  Binding binding() const {
    return static_cast<Binding>(info >> 4);
  }
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#if (V8_TARGET_ARCH_IA32 || V8_TARGET_ARCH_ARM ||     \
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     (V8_TARGET_ARCH_S390 && V8_TARGET_ARCH_32_BIT))
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  struct SerializedLayout {
    SerializedLayout(uint32_t name,
                     uintptr_t value,
                     uintptr_t size,
                     Binding binding,
                     Type type,
                     uint16_t section)
        : name(name),
          value(value),
          size(size),
          info((binding << 4) | type),
          other(0),
          section(section) {
    }

    uint32_t name;
    uintptr_t value;
    uintptr_t size;
    uint8_t info;
    uint8_t other;
    uint16_t section;
  };
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#elif(V8_TARGET_ARCH_X64 && V8_TARGET_ARCH_64_BIT) || \
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    (V8_TARGET_ARCH_PPC64 && V8_OS_LINUX) || V8_TARGET_ARCH_S390X
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  struct SerializedLayout {
    SerializedLayout(uint32_t name,
                     uintptr_t value,
                     uintptr_t size,
                     Binding binding,
                     Type type,
                     uint16_t section)
        : name(name),
          info((binding << 4) | type),
          other(0),
          section(section),
          value(value),
          size(size) {
    }

    uint32_t name;
    uint8_t info;
    uint8_t other;
    uint16_t section;
    uintptr_t value;
    uintptr_t size;
  };
#endif

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  void Write(Writer::Slot<SerializedLayout> s, ELFStringTable* t) const {
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    // Convert symbol names from strings to indexes in the string table.
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    s->name = static_cast<uint32_t>(t->Add(name));
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    s->value = value;
    s->size = size;
    s->info = info;
    s->other = other;
    s->section = section;
  }

 private:
  const char* name;
  uintptr_t value;
  uintptr_t size;
  uint8_t info;
  uint8_t other;
  uint16_t section;
};


class ELFSymbolTable : public ELFSection {
 public:
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  ELFSymbolTable(const char* name, Zone* zone)
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      : ELFSection(name, TYPE_SYMTAB, sizeof(uintptr_t)),
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        locals_(zone),
        globals_(zone) {}
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  void WriteBody(Writer::Slot<Header> header, Writer* w) override {
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    w->Align(header->alignment);
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    size_t total_symbols = locals_.size() + globals_.size() + 1;
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    header->offset = w->position();

    Writer::Slot<ELFSymbol::SerializedLayout> symbols =
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        w->CreateSlotsHere<ELFSymbol::SerializedLayout>(
            static_cast<uint32_t>(total_symbols));
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    header->size = w->position() - header->offset;

    // String table for this symbol table should follow it in the section table.
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    ELFStringTable* strtab =
        static_cast<ELFStringTable*>(w->debug_object()->SectionAt(index() + 1));
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    strtab->AttachWriter(w);
    symbols.at(0).set(ELFSymbol::SerializedLayout(0,
                                                  0,
                                                  0,
                                                  ELFSymbol::BIND_LOCAL,
                                                  ELFSymbol::TYPE_NOTYPE,
                                                  0));
    WriteSymbolsList(&locals_, symbols.at(1), strtab);
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    WriteSymbolsList(&globals_,
                     symbols.at(static_cast<uint32_t>(locals_.size() + 1)),
                     strtab);
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    strtab->DetachWriter();
  }

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  void Add(const ELFSymbol& symbol) {
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    if (symbol.binding() == ELFSymbol::BIND_LOCAL) {
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      locals_.push_back(symbol);
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    } else {
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      globals_.push_back(symbol);
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    }
  }

 protected:
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  void PopulateHeader(Writer::Slot<Header> header) override {
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    ELFSection::PopulateHeader(header);
    // We are assuming that string table will follow symbol table.
    header->link = index() + 1;
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    header->info = static_cast<uint32_t>(locals_.size() + 1);
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    header->entry_size = sizeof(ELFSymbol::SerializedLayout);
  }

 private:
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  void WriteSymbolsList(const ZoneChunkList<ELFSymbol>* src,
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                        Writer::Slot<ELFSymbol::SerializedLayout> dst,
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                        ELFStringTable* strtab) {
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    int i = 0;
    for (const ELFSymbol& symbol : *src) {
      symbol.Write(dst.at(i++), strtab);
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    }
  }

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  ZoneChunkList<ELFSymbol> locals_;
  ZoneChunkList<ELFSymbol> globals_;
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};
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#endif  // defined(__ELF)
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class LineInfo : public Malloced {
 public:
  void SetPosition(intptr_t pc, int pos, bool is_statement) {
    AddPCInfo(PCInfo(pc, pos, is_statement));
  }

  struct PCInfo {
    PCInfo(intptr_t pc, int pos, bool is_statement)
        : pc_(pc), pos_(pos), is_statement_(is_statement) {}

    intptr_t pc_;
    int pos_;
    bool is_statement_;
  };

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  std::vector<PCInfo>* pc_info() { return &pc_info_; }
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 private:
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  void AddPCInfo(const PCInfo& pc_info) { pc_info_.push_back(pc_info); }
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  std::vector<PCInfo> pc_info_;
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};

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class CodeDescription {
944
 public:
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#if V8_TARGET_ARCH_X64
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  enum StackState {
    POST_RBP_PUSH,
    POST_RBP_SET,
    POST_RBP_POP,
    STACK_STATE_MAX
  };
#endif

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  CodeDescription(const char* name, Code code, SharedFunctionInfo shared,
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                  LineInfo* lineinfo)
      : name_(name), code_(code), shared_info_(shared), lineinfo_(lineinfo) {}
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  const char* name() const {
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    return name_;
  }

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  LineInfo* lineinfo() const { return lineinfo_; }
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  bool is_function() const {
    Code::Kind kind = code_->kind();
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    return kind == Code::OPTIMIZED_FUNCTION;
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  }

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  bool has_scope_info() const { return !shared_info_.is_null(); }
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  ScopeInfo scope_info() const {
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    DCHECK(has_scope_info());
    return shared_info_->scope_info();
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  }

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  uintptr_t CodeStart() const {
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    return static_cast<uintptr_t>(code_->InstructionStart());
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  }

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  uintptr_t CodeEnd() const {
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    return static_cast<uintptr_t>(code_->InstructionEnd());
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  }

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  uintptr_t CodeSize() const {
    return CodeEnd() - CodeStart();
  }

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  bool has_script() {
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    return !shared_info_.is_null() && shared_info_->script()->IsScript();
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  }

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  Script script() { return Script::cast(shared_info_->script()); }
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  bool IsLineInfoAvailable() { return lineinfo_ != nullptr; }
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#if V8_TARGET_ARCH_X64
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  uintptr_t GetStackStateStartAddress(StackState state) const {
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    DCHECK(state < STACK_STATE_MAX);
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    return stack_state_start_addresses_[state];
  }
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  void SetStackStateStartAddress(StackState state, uintptr_t addr) {
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    DCHECK(state < STACK_STATE_MAX);
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    stack_state_start_addresses_[state] = addr;
  }
#endif

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  std::unique_ptr<char[]> GetFilename() {
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    if (!shared_info_.is_null()) {
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      return String::cast(script()->name())->ToCString();
    } else {
      std::unique_ptr<char[]> result(new char[1]);
      result[0] = 0;
      return result;
    }
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  }

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  int GetScriptLineNumber(int pos) {
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    if (!shared_info_.is_null()) {
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      return script()->GetLineNumber(pos) + 1;
    } else {
      return 0;
    }
  }
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 private:
  const char* name_;
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  Code code_;
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  SharedFunctionInfo shared_info_;
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  LineInfo* lineinfo_;
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#if V8_TARGET_ARCH_X64
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  uintptr_t stack_state_start_addresses_[STACK_STATE_MAX];
#endif
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};

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#if defined(__ELF)
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static void CreateSymbolsTable(CodeDescription* desc, Zone* zone, ELF* elf,
                               size_t text_section_index) {
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  ELFSymbolTable* symtab = new(zone) ELFSymbolTable(".symtab", zone);
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  ELFStringTable* strtab = new(zone) ELFStringTable(".strtab");
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  // Symbol table should be followed by the linked string table.
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  elf->AddSection(symtab);
  elf->AddSection(strtab);
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  symtab->Add(ELFSymbol("V8 Code", 0, 0, ELFSymbol::BIND_LOCAL,
                        ELFSymbol::TYPE_FILE, ELFSection::INDEX_ABSOLUTE));

  symtab->Add(ELFSymbol(desc->name(), 0, desc->CodeSize(),
                        ELFSymbol::BIND_GLOBAL, ELFSymbol::TYPE_FUNC,
                        text_section_index));
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}
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#endif  // defined(__ELF)
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class DebugInfoSection : public DebugSection {
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 public:
  explicit DebugInfoSection(CodeDescription* desc)
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#if defined(__ELF)
      : ELFSection(".debug_info", TYPE_PROGBITS, 1),
#else
      : MachOSection("__debug_info",
                     "__DWARF",
                     1,
                     MachOSection::S_REGULAR | MachOSection::S_ATTR_DEBUG),
#endif
        desc_(desc) { }

  // DWARF2 standard
  enum DWARF2LocationOp {
    DW_OP_reg0 = 0x50,
    DW_OP_reg1 = 0x51,
    DW_OP_reg2 = 0x52,
    DW_OP_reg3 = 0x53,
    DW_OP_reg4 = 0x54,
    DW_OP_reg5 = 0x55,
    DW_OP_reg6 = 0x56,
    DW_OP_reg7 = 0x57,
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    DW_OP_reg8 = 0x58,
    DW_OP_reg9 = 0x59,
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    DW_OP_reg10 = 0x5A,
    DW_OP_reg11 = 0x5B,
    DW_OP_reg12 = 0x5C,
    DW_OP_reg13 = 0x5D,
    DW_OP_reg14 = 0x5E,
    DW_OP_reg15 = 0x5F,
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    DW_OP_reg16 = 0x60,
    DW_OP_reg17 = 0x61,
    DW_OP_reg18 = 0x62,
    DW_OP_reg19 = 0x63,
    DW_OP_reg20 = 0x64,
    DW_OP_reg21 = 0x65,
    DW_OP_reg22 = 0x66,
    DW_OP_reg23 = 0x67,
    DW_OP_reg24 = 0x68,
    DW_OP_reg25 = 0x69,
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    DW_OP_reg26 = 0x6A,
    DW_OP_reg27 = 0x6B,
    DW_OP_reg28 = 0x6C,
    DW_OP_reg29 = 0x6D,
    DW_OP_reg30 = 0x6E,
    DW_OP_reg31 = 0x6F,
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    DW_OP_fbreg = 0x91  // 1 param: SLEB128 offset
  };

  enum DWARF2Encoding {
    DW_ATE_ADDRESS = 0x1,
    DW_ATE_SIGNED = 0x5
  };
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  bool WriteBodyInternal(Writer* w) override {
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    uintptr_t cu_start = w->position();
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    Writer::Slot<uint32_t> size = w->CreateSlotHere<uint32_t>();
    uintptr_t start = w->position();
    w->Write<uint16_t>(2);  // DWARF version.
    w->Write<uint32_t>(0);  // Abbreviation table offset.
    w->Write<uint8_t>(sizeof(intptr_t));

    w->WriteULEB128(1);  // Abbreviation code.
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    w->WriteString(desc_->GetFilename().get());
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    w->Write<intptr_t>(desc_->CodeStart());
    w->Write<intptr_t>(desc_->CodeStart() + desc_->CodeSize());
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    w->Write<uint32_t>(0);
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    uint32_t ty_offset = static_cast<uint32_t>(w->position() - cu_start);
    w->WriteULEB128(3);
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    w->Write<uint8_t>(kSystemPointerSize);
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    w->WriteString("v8value");

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    if (desc_->has_scope_info()) {
1131
      ScopeInfo scope = desc_->scope_info();
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      w->WriteULEB128(2);
      w->WriteString(desc_->name());
      w->Write<intptr_t>(desc_->CodeStart());
      w->Write<intptr_t>(desc_->CodeStart() + desc_->CodeSize());
      Writer::Slot<uint32_t> fb_block_size = w->CreateSlotHere<uint32_t>();
      uintptr_t fb_block_start = w->position();
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1138
#if V8_TARGET_ARCH_IA32
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      w->Write<uint8_t>(DW_OP_reg5);  // The frame pointer's here on ia32
1140
#elif V8_TARGET_ARCH_X64
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      w->Write<uint8_t>(DW_OP_reg6);  // and here on x64.
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#elif V8_TARGET_ARCH_ARM
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      UNIMPLEMENTED();
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#elif V8_TARGET_ARCH_MIPS
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      UNIMPLEMENTED();
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#elif V8_TARGET_ARCH_MIPS64
      UNIMPLEMENTED();
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#elif V8_TARGET_ARCH_PPC64 && V8_OS_LINUX
      w->Write<uint8_t>(DW_OP_reg31);  // The frame pointer is here on PPC64.
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#elif V8_TARGET_ARCH_S390
      w->Write<uint8_t>(DW_OP_reg11);  // The frame pointer's here on S390.
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#else
#error Unsupported target architecture.
#endif
      fb_block_size.set(static_cast<uint32_t>(w->position() - fb_block_start));

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      int params = scope->ParameterCount();
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      int context_slots = scope->ContextLocalCount();
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      // The real slot ID is internal_slots + context_slot_id.
      int internal_slots = Context::MIN_CONTEXT_SLOTS;
      int current_abbreviation = 4;

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      EmbeddedVector<char, 256> buffer;
      StringBuilder builder(buffer.start(), buffer.length());

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      for (int param = 0; param < params; ++param) {
        w->WriteULEB128(current_abbreviation++);
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        builder.Reset();
        builder.AddFormatted("param%d", param);
        w->WriteString(builder.Finalize());
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        w->Write<uint32_t>(ty_offset);
        Writer::Slot<uint32_t> block_size = w->CreateSlotHere<uint32_t>();
        uintptr_t block_start = w->position();
        w->Write<uint8_t>(DW_OP_fbreg);
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        w->WriteSLEB128(JavaScriptFrameConstants::kLastParameterOffset +
                        kSystemPointerSize * (params - param - 1));
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        block_size.set(static_cast<uint32_t>(w->position() - block_start));
      }

      // See contexts.h for more information.
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      DCHECK_EQ(Context::MIN_CONTEXT_SLOTS, 4);
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      DCHECK_EQ(Context::SCOPE_INFO_INDEX, 0);
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      DCHECK_EQ(Context::PREVIOUS_INDEX, 1);
      DCHECK_EQ(Context::EXTENSION_INDEX, 2);
      DCHECK_EQ(Context::NATIVE_CONTEXT_INDEX, 3);
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      w->WriteULEB128(current_abbreviation++);
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      w->WriteString(".scope_info");
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      w->WriteULEB128(current_abbreviation++);
      w->WriteString(".previous");
      w->WriteULEB128(current_abbreviation++);
      w->WriteString(".extension");
      w->WriteULEB128(current_abbreviation++);
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      w->WriteString(".native_context");
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      for (int context_slot = 0;
           context_slot < context_slots;
           ++context_slot) {
        w->WriteULEB128(current_abbreviation++);
        builder.Reset();
        builder.AddFormatted("context_slot%d", context_slot + internal_slots);
        w->WriteString(builder.Finalize());
      }

      {
        w->WriteULEB128(current_abbreviation++);
        w->WriteString("__function");
        w->Write<uint32_t>(ty_offset);
        Writer::Slot<uint32_t> block_size = w->CreateSlotHere<uint32_t>();
        uintptr_t block_start = w->position();
        w->Write<uint8_t>(DW_OP_fbreg);
        w->WriteSLEB128(JavaScriptFrameConstants::kFunctionOffset);
        block_size.set(static_cast<uint32_t>(w->position() - block_start));
      }

      {
        w->WriteULEB128(current_abbreviation++);
        w->WriteString("__context");
        w->Write<uint32_t>(ty_offset);
        Writer::Slot<uint32_t> block_size = w->CreateSlotHere<uint32_t>();
        uintptr_t block_start = w->position();
        w->Write<uint8_t>(DW_OP_fbreg);
        w->WriteSLEB128(StandardFrameConstants::kContextOffset);
        block_size.set(static_cast<uint32_t>(w->position() - block_start));
      }
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      w->WriteULEB128(0);  // Terminate the sub program.
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    }

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    w->WriteULEB128(0);  // Terminate the compile unit.
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    size.set(static_cast<uint32_t>(w->position() - start));
    return true;
  }

 private:
  CodeDescription* desc_;
};


1239
class DebugAbbrevSection : public DebugSection {
1240
 public:
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  explicit DebugAbbrevSection(CodeDescription* desc)
#ifdef __ELF
      : ELFSection(".debug_abbrev", TYPE_PROGBITS, 1),
#else
      : MachOSection("__debug_abbrev",
                     "__DWARF",
                     1,
                     MachOSection::S_REGULAR | MachOSection::S_ATTR_DEBUG),
#endif
        desc_(desc) { }
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  // DWARF2 standard, figure 14.
  enum DWARF2Tags {
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    DW_TAG_FORMAL_PARAMETER = 0x05,
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    DW_TAG_POINTER_TYPE = 0xF,
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    DW_TAG_COMPILE_UNIT = 0x11,
    DW_TAG_STRUCTURE_TYPE = 0x13,
    DW_TAG_BASE_TYPE = 0x24,
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    DW_TAG_SUBPROGRAM = 0x2E,
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    DW_TAG_VARIABLE = 0x34
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  };

  // DWARF2 standard, figure 16.
  enum DWARF2ChildrenDetermination {
    DW_CHILDREN_NO = 0,
    DW_CHILDREN_YES = 1
  };

  // DWARF standard, figure 17.
  enum DWARF2Attribute {
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    DW_AT_LOCATION = 0x2,
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    DW_AT_NAME = 0x3,
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    DW_AT_BYTE_SIZE = 0xB,
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    DW_AT_STMT_LIST = 0x10,
    DW_AT_LOW_PC = 0x11,
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    DW_AT_HIGH_PC = 0x12,
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    DW_AT_ENCODING = 0x3E,
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    DW_AT_FRAME_BASE = 0x40,
    DW_AT_TYPE = 0x49
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  };

  // DWARF2 standard, figure 19.
  enum DWARF2AttributeForm {
    DW_FORM_ADDR = 0x1,
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    DW_FORM_BLOCK4 = 0x4,
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    DW_FORM_STRING = 0x8,
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    DW_FORM_DATA4 = 0x6,
    DW_FORM_BLOCK = 0x9,
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    DW_FORM_DATA1 = 0xB,
    DW_FORM_FLAG = 0xC,
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    DW_FORM_REF4 = 0x13
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  };

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  void WriteVariableAbbreviation(Writer* w,
                                 int abbreviation_code,
                                 bool has_value,
                                 bool is_parameter) {
    w->WriteULEB128(abbreviation_code);
    w->WriteULEB128(is_parameter ? DW_TAG_FORMAL_PARAMETER : DW_TAG_VARIABLE);
    w->Write<uint8_t>(DW_CHILDREN_NO);
    w->WriteULEB128(DW_AT_NAME);
    w->WriteULEB128(DW_FORM_STRING);
    if (has_value) {
      w->WriteULEB128(DW_AT_TYPE);
      w->WriteULEB128(DW_FORM_REF4);
      w->WriteULEB128(DW_AT_LOCATION);
      w->WriteULEB128(DW_FORM_BLOCK4);
    }
    w->WriteULEB128(0);
    w->WriteULEB128(0);
  }

1313
  bool WriteBodyInternal(Writer* w) override {
1314
    int current_abbreviation = 1;
1315
    bool extra_info = desc_->has_scope_info();
1316
    DCHECK(desc_->IsLineInfoAvailable());
1317
    w->WriteULEB128(current_abbreviation++);
1318
    w->WriteULEB128(DW_TAG_COMPILE_UNIT);
1319
    w->Write<uint8_t>(extra_info ? DW_CHILDREN_YES : DW_CHILDREN_NO);
1320 1321 1322 1323 1324 1325 1326 1327 1328 1329
    w->WriteULEB128(DW_AT_NAME);
    w->WriteULEB128(DW_FORM_STRING);
    w->WriteULEB128(DW_AT_LOW_PC);
    w->WriteULEB128(DW_FORM_ADDR);
    w->WriteULEB128(DW_AT_HIGH_PC);
    w->WriteULEB128(DW_FORM_ADDR);
    w->WriteULEB128(DW_AT_STMT_LIST);
    w->WriteULEB128(DW_FORM_DATA4);
    w->WriteULEB128(0);
    w->WriteULEB128(0);
1330 1331

    if (extra_info) {
1332
      ScopeInfo scope = desc_->scope_info();
1333
      int params = scope->ParameterCount();
1334
      int context_slots = scope->ContextLocalCount();
1335 1336
      // The real slot ID is internal_slots + context_slot_id.
      int internal_slots = Context::MIN_CONTEXT_SLOTS;
1337 1338
      // Total children is params + context_slots + internal_slots + 2
      // (__function and __context).
1339 1340 1341 1342 1343

      // The extra duplication below seems to be necessary to keep
      // gdb from getting upset on OSX.
      w->WriteULEB128(current_abbreviation++);  // Abbreviation code.
      w->WriteULEB128(DW_TAG_SUBPROGRAM);
1344
      w->Write<uint8_t>(DW_CHILDREN_YES);
1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387
      w->WriteULEB128(DW_AT_NAME);
      w->WriteULEB128(DW_FORM_STRING);
      w->WriteULEB128(DW_AT_LOW_PC);
      w->WriteULEB128(DW_FORM_ADDR);
      w->WriteULEB128(DW_AT_HIGH_PC);
      w->WriteULEB128(DW_FORM_ADDR);
      w->WriteULEB128(DW_AT_FRAME_BASE);
      w->WriteULEB128(DW_FORM_BLOCK4);
      w->WriteULEB128(0);
      w->WriteULEB128(0);

      w->WriteULEB128(current_abbreviation++);
      w->WriteULEB128(DW_TAG_STRUCTURE_TYPE);
      w->Write<uint8_t>(DW_CHILDREN_NO);
      w->WriteULEB128(DW_AT_BYTE_SIZE);
      w->WriteULEB128(DW_FORM_DATA1);
      w->WriteULEB128(DW_AT_NAME);
      w->WriteULEB128(DW_FORM_STRING);
      w->WriteULEB128(0);
      w->WriteULEB128(0);

      for (int param = 0; param < params; ++param) {
        WriteVariableAbbreviation(w, current_abbreviation++, true, true);
      }

      for (int internal_slot = 0;
           internal_slot < internal_slots;
           ++internal_slot) {
        WriteVariableAbbreviation(w, current_abbreviation++, false, false);
      }

      for (int context_slot = 0;
           context_slot < context_slots;
           ++context_slot) {
        WriteVariableAbbreviation(w, current_abbreviation++, false, false);
      }

      // The function.
      WriteVariableAbbreviation(w, current_abbreviation++, true, false);

      // The context.
      WriteVariableAbbreviation(w, current_abbreviation++, true, false);

1388
      w->WriteULEB128(0);  // Terminate the sibling list.
1389 1390 1391
    }

    w->WriteULEB128(0);  // Terminate the table.
1392 1393
    return true;
  }
1394 1395 1396

 private:
  CodeDescription* desc_;
1397 1398 1399
};


1400
class DebugLineSection : public DebugSection {
1401 1402
 public:
  explicit DebugLineSection(CodeDescription* desc)
1403
#ifdef __ELF
1404
      : ELFSection(".debug_line", TYPE_PROGBITS, 1),
1405 1406 1407 1408 1409 1410
#else
      : MachOSection("__debug_line",
                     "__DWARF",
                     1,
                     MachOSection::S_REGULAR | MachOSection::S_ATTR_DEBUG),
#endif
1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429
        desc_(desc) { }

  // DWARF2 standard, figure 34.
  enum DWARF2Opcodes {
    DW_LNS_COPY = 1,
    DW_LNS_ADVANCE_PC = 2,
    DW_LNS_ADVANCE_LINE = 3,
    DW_LNS_SET_FILE = 4,
    DW_LNS_SET_COLUMN = 5,
    DW_LNS_NEGATE_STMT = 6
  };

  // DWARF2 standard, figure 35.
  enum DWARF2ExtendedOpcode {
    DW_LNE_END_SEQUENCE = 1,
    DW_LNE_SET_ADDRESS = 2,
    DW_LNE_DEFINE_FILE = 3
  };

1430
  bool WriteBodyInternal(Writer* w) override {
1431 1432 1433 1434
    // Write prologue.
    Writer::Slot<uint32_t> total_length = w->CreateSlotHere<uint32_t>();
    uintptr_t start = w->position();

1435 1436 1437 1438 1439 1440
    // Used for special opcodes
    const int8_t line_base = 1;
    const uint8_t line_range = 7;
    const int8_t max_line_incr = (line_base + line_range - 1);
    const uint8_t opcode_base = DW_LNS_NEGATE_STMT + 1;

1441 1442 1443 1444 1445
    w->Write<uint16_t>(2);  // Field version.
    Writer::Slot<uint32_t> prologue_length = w->CreateSlotHere<uint32_t>();
    uintptr_t prologue_start = w->position();
    w->Write<uint8_t>(1);  // Field minimum_instruction_length.
    w->Write<uint8_t>(1);  // Field default_is_stmt.
1446 1447 1448
    w->Write<int8_t>(line_base);  // Field line_base.
    w->Write<uint8_t>(line_range);  // Field line_range.
    w->Write<uint8_t>(opcode_base);  // Field opcode_base.
1449 1450 1451 1452 1453 1454 1455
    w->Write<uint8_t>(0);  // DW_LNS_COPY operands count.
    w->Write<uint8_t>(1);  // DW_LNS_ADVANCE_PC operands count.
    w->Write<uint8_t>(1);  // DW_LNS_ADVANCE_LINE operands count.
    w->Write<uint8_t>(1);  // DW_LNS_SET_FILE operands count.
    w->Write<uint8_t>(1);  // DW_LNS_SET_COLUMN operands count.
    w->Write<uint8_t>(0);  // DW_LNS_NEGATE_STMT operands count.
    w->Write<uint8_t>(0);  // Empty include_directories sequence.
1456
    w->WriteString(desc_->GetFilename().get());  // File name.
1457 1458 1459 1460 1461 1462 1463
    w->WriteULEB128(0);  // Current directory.
    w->WriteULEB128(0);  // Unknown modification time.
    w->WriteULEB128(0);  // Unknown file size.
    w->Write<uint8_t>(0);
    prologue_length.set(static_cast<uint32_t>(w->position() - prologue_start));

    WriteExtendedOpcode(w, DW_LNE_SET_ADDRESS, sizeof(intptr_t));
1464
    w->Write<intptr_t>(desc_->CodeStart());
1465
    w->Write<uint8_t>(DW_LNS_COPY);
1466 1467 1468 1469 1470

    intptr_t pc = 0;
    intptr_t line = 1;
    bool is_statement = true;

1471 1472
    std::vector<LineInfo::PCInfo>* pc_info = desc_->lineinfo()->pc_info();
    std::sort(pc_info->begin(), pc_info->end(), &ComparePCInfo);
1473

1474
    for (size_t i = 0; i < pc_info->size(); i++) {
1475
      LineInfo::PCInfo* info = &pc_info->at(i);
1476
      DCHECK(info->pc_ >= pc);
1477 1478 1479 1480 1481 1482

      // Reduce bloating in the debug line table by removing duplicate line
      // entries (per DWARF2 standard).
      intptr_t  new_line = desc_->GetScriptLineNumber(info->pos_);
      if (new_line == line) {
        continue;
1483
      }
1484 1485 1486 1487 1488

      // Mark statement boundaries.  For a better debugging experience, mark
      // the last pc address in the function as a statement (e.g. "}"), so that
      // a user can see the result of the last line executed in the function,
      // should control reach the end.
1489
      if ((i + 1) == pc_info->size()) {
1490 1491 1492 1493
        if (!is_statement) {
          w->Write<uint8_t>(DW_LNS_NEGATE_STMT);
        }
      } else if (is_statement != info->is_statement_) {
1494 1495 1496
        w->Write<uint8_t>(DW_LNS_NEGATE_STMT);
        is_statement = !is_statement;
      }
1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520

      // Generate special opcodes, if possible.  This results in more compact
      // debug line tables.  See the DWARF 2.0 standard to learn more about
      // special opcodes.
      uintptr_t pc_diff = info->pc_ - pc;
      intptr_t line_diff = new_line - line;

      // Compute special opcode (see DWARF 2.0 standard)
      intptr_t special_opcode = (line_diff - line_base) +
                                (line_range * pc_diff) + opcode_base;

      // If special_opcode is less than or equal to 255, it can be used as a
      // special opcode.  If line_diff is larger than the max line increment
      // allowed for a special opcode, or if line_diff is less than the minimum
      // line that can be added to the line register (i.e. line_base), then
      // special_opcode can't be used.
      if ((special_opcode >= opcode_base) && (special_opcode <= 255) &&
          (line_diff <= max_line_incr) && (line_diff >= line_base)) {
        w->Write<uint8_t>(special_opcode);
      } else {
        w->Write<uint8_t>(DW_LNS_ADVANCE_PC);
        w->WriteSLEB128(pc_diff);
        w->Write<uint8_t>(DW_LNS_ADVANCE_LINE);
        w->WriteSLEB128(line_diff);
1521 1522
        w->Write<uint8_t>(DW_LNS_COPY);
      }
1523 1524 1525 1526

      // Increment the pc and line operands.
      pc += pc_diff;
      line += line_diff;
1527
    }
1528 1529 1530 1531
    // Advance the pc to the end of the routine, since the end sequence opcode
    // requires this.
    w->Write<uint8_t>(DW_LNS_ADVANCE_PC);
    w->WriteSLEB128(desc_->CodeSize() - pc);
1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545
    WriteExtendedOpcode(w, DW_LNE_END_SEQUENCE, 0);
    total_length.set(static_cast<uint32_t>(w->position() - start));
    return true;
  }

 private:
  void WriteExtendedOpcode(Writer* w,
                           DWARF2ExtendedOpcode op,
                           size_t operands_size) {
    w->Write<uint8_t>(0);
    w->WriteULEB128(operands_size + 1);
    w->Write<uint8_t>(op);
  }

1546 1547 1548 1549 1550
  static bool ComparePCInfo(const LineInfo::PCInfo& a,
                            const LineInfo::PCInfo& b) {
    if (a.pc_ == b.pc_) {
      if (a.is_statement_ != b.is_statement_) {
        return !b.is_statement_;
1551
      }
1552
      return false;
1553
    }
1554
    return a.pc_ < b.pc_;
1555 1556 1557 1558 1559 1560
  }

  CodeDescription* desc_;
};


1561
#if V8_TARGET_ARCH_X64
1562

1563
class UnwindInfoSection : public DebugSection {
1564
 public:
1565
  explicit UnwindInfoSection(CodeDescription* desc);
1566
  bool WriteBodyInternal(Writer* w) override;
1567

1568 1569
  int WriteCIE(Writer* w);
  void WriteFDE(Writer* w, int);
1570

1571 1572 1573 1574
  void WriteFDEStateOnEntry(Writer* w);
  void WriteFDEStateAfterRBPPush(Writer* w);
  void WriteFDEStateAfterRBPSet(Writer* w);
  void WriteFDEStateAfterRBPPop(Writer* w);
1575

1576
  void WriteLength(Writer* w,
1577 1578 1579 1580
                   Writer::Slot<uint32_t>* length_slot,
                   int initial_position);

 private:
1581
  CodeDescription* desc_;
1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631

  // DWARF3 Specification, Table 7.23
  enum CFIInstructions {
    DW_CFA_ADVANCE_LOC = 0x40,
    DW_CFA_OFFSET = 0x80,
    DW_CFA_RESTORE = 0xC0,
    DW_CFA_NOP = 0x00,
    DW_CFA_SET_LOC = 0x01,
    DW_CFA_ADVANCE_LOC1 = 0x02,
    DW_CFA_ADVANCE_LOC2 = 0x03,
    DW_CFA_ADVANCE_LOC4 = 0x04,
    DW_CFA_OFFSET_EXTENDED = 0x05,
    DW_CFA_RESTORE_EXTENDED = 0x06,
    DW_CFA_UNDEFINED = 0x07,
    DW_CFA_SAME_VALUE = 0x08,
    DW_CFA_REGISTER = 0x09,
    DW_CFA_REMEMBER_STATE = 0x0A,
    DW_CFA_RESTORE_STATE = 0x0B,
    DW_CFA_DEF_CFA = 0x0C,
    DW_CFA_DEF_CFA_REGISTER = 0x0D,
    DW_CFA_DEF_CFA_OFFSET = 0x0E,

    DW_CFA_DEF_CFA_EXPRESSION = 0x0F,
    DW_CFA_EXPRESSION = 0x10,
    DW_CFA_OFFSET_EXTENDED_SF = 0x11,
    DW_CFA_DEF_CFA_SF = 0x12,
    DW_CFA_DEF_CFA_OFFSET_SF = 0x13,
    DW_CFA_VAL_OFFSET = 0x14,
    DW_CFA_VAL_OFFSET_SF = 0x15,
    DW_CFA_VAL_EXPRESSION = 0x16
  };

  // System V ABI, AMD64 Supplement, Version 0.99.5, Figure 3.36
  enum RegisterMapping {
    // Only the relevant ones have been added to reduce clutter.
    AMD64_RBP = 6,
    AMD64_RSP = 7,
    AMD64_RA = 16
  };

  enum CFIConstants {
    CIE_ID = 0,
    CIE_VERSION = 1,
    CODE_ALIGN_FACTOR = 1,
    DATA_ALIGN_FACTOR = 1,
    RETURN_ADDRESS_REGISTER = AMD64_RA
  };
};


1632
void UnwindInfoSection::WriteLength(Writer* w,
1633 1634
                                    Writer::Slot<uint32_t>* length_slot,
                                    int initial_position) {
1635
  uint32_t align = (w->position() - initial_position) % kSystemPointerSize;
1636 1637

  if (align != 0) {
1638
    for (uint32_t i = 0; i < (kSystemPointerSize - align); i++) {
1639 1640 1641 1642
      w->Write<uint8_t>(DW_CFA_NOP);
    }
  }

1643
  DCHECK_EQ((w->position() - initial_position) % kSystemPointerSize, 0);
1644
  length_slot->set(static_cast<uint32_t>(w->position() - initial_position));
1645 1646 1647
}


1648
UnwindInfoSection::UnwindInfoSection(CodeDescription* desc)
1649 1650 1651 1652 1653 1654 1655
#ifdef __ELF
    : ELFSection(".eh_frame", TYPE_X86_64_UNWIND, 1),
#else
    : MachOSection("__eh_frame", "__TEXT", sizeof(uintptr_t),
                   MachOSection::S_REGULAR),
#endif
      desc_(desc) { }
1656

1657
int UnwindInfoSection::WriteCIE(Writer* w) {
1658
  Writer::Slot<uint32_t> cie_length_slot = w->CreateSlotHere<uint32_t>();
1659
  uint32_t cie_position = static_cast<uint32_t>(w->position());
1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676

  // Write out the CIE header. Currently no 'common instructions' are
  // emitted onto the CIE; every FDE has its own set of instructions.

  w->Write<uint32_t>(CIE_ID);
  w->Write<uint8_t>(CIE_VERSION);
  w->Write<uint8_t>(0);  // Null augmentation string.
  w->WriteSLEB128(CODE_ALIGN_FACTOR);
  w->WriteSLEB128(DATA_ALIGN_FACTOR);
  w->Write<uint8_t>(RETURN_ADDRESS_REGISTER);

  WriteLength(w, &cie_length_slot, cie_position);

  return cie_position;
}


1677
void UnwindInfoSection::WriteFDE(Writer* w, int cie_position) {
1678 1679
  // The only FDE for this function. The CFA is the current RBP.
  Writer::Slot<uint32_t> fde_length_slot = w->CreateSlotHere<uint32_t>();
1680
  int fde_position = static_cast<uint32_t>(w->position());
1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694
  w->Write<int32_t>(fde_position - cie_position + 4);

  w->Write<uintptr_t>(desc_->CodeStart());
  w->Write<uintptr_t>(desc_->CodeSize());

  WriteFDEStateOnEntry(w);
  WriteFDEStateAfterRBPPush(w);
  WriteFDEStateAfterRBPSet(w);
  WriteFDEStateAfterRBPPop(w);

  WriteLength(w, &fde_length_slot, fde_position);
}


1695
void UnwindInfoSection::WriteFDEStateOnEntry(Writer* w) {
1696 1697 1698 1699 1700 1701 1702
  // The first state, just after the control has been transferred to the the
  // function.

  // RBP for this function will be the value of RSP after pushing the RBP
  // for the previous function. The previous RBP has not been pushed yet.
  w->Write<uint8_t>(DW_CFA_DEF_CFA_SF);
  w->WriteULEB128(AMD64_RSP);
1703
  w->WriteSLEB128(-kSystemPointerSize);
1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721

  // The RA is stored at location CFA + kCallerPCOffset. This is an invariant,
  // and hence omitted from the next states.
  w->Write<uint8_t>(DW_CFA_OFFSET_EXTENDED);
  w->WriteULEB128(AMD64_RA);
  w->WriteSLEB128(StandardFrameConstants::kCallerPCOffset);

  // The RBP of the previous function is still in RBP.
  w->Write<uint8_t>(DW_CFA_SAME_VALUE);
  w->WriteULEB128(AMD64_RBP);

  // Last location described by this entry.
  w->Write<uint8_t>(DW_CFA_SET_LOC);
  w->Write<uint64_t>(
      desc_->GetStackStateStartAddress(CodeDescription::POST_RBP_PUSH));
}


1722
void UnwindInfoSection::WriteFDEStateAfterRBPPush(Writer* w) {
1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742
  // The second state, just after RBP has been pushed.

  // RBP / CFA for this function is now the current RSP, so just set the
  // offset from the previous rule (from -8) to 0.
  w->Write<uint8_t>(DW_CFA_DEF_CFA_OFFSET);
  w->WriteULEB128(0);

  // The previous RBP is stored at CFA + kCallerFPOffset. This is an invariant
  // in this and the next state, and hence omitted in the next state.
  w->Write<uint8_t>(DW_CFA_OFFSET_EXTENDED);
  w->WriteULEB128(AMD64_RBP);
  w->WriteSLEB128(StandardFrameConstants::kCallerFPOffset);

  // Last location described by this entry.
  w->Write<uint8_t>(DW_CFA_SET_LOC);
  w->Write<uint64_t>(
      desc_->GetStackStateStartAddress(CodeDescription::POST_RBP_SET));
}


1743
void UnwindInfoSection::WriteFDEStateAfterRBPSet(Writer* w) {
1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757
  // The third state, after the RBP has been set.

  // The CFA can now directly be set to RBP.
  w->Write<uint8_t>(DW_CFA_DEF_CFA);
  w->WriteULEB128(AMD64_RBP);
  w->WriteULEB128(0);

  // Last location described by this entry.
  w->Write<uint8_t>(DW_CFA_SET_LOC);
  w->Write<uint64_t>(
      desc_->GetStackStateStartAddress(CodeDescription::POST_RBP_POP));
}


1758
void UnwindInfoSection::WriteFDEStateAfterRBPPop(Writer* w) {
1759 1760 1761 1762 1763 1764
  // The fourth (final) state. The RBP has been popped (just before issuing a
  // return).

  // The CFA can is now calculated in the same way as in the first state.
  w->Write<uint8_t>(DW_CFA_DEF_CFA_SF);
  w->WriteULEB128(AMD64_RSP);
1765
  w->WriteSLEB128(-kSystemPointerSize);
1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777

  // The RBP
  w->Write<uint8_t>(DW_CFA_OFFSET_EXTENDED);
  w->WriteULEB128(AMD64_RBP);
  w->WriteSLEB128(StandardFrameConstants::kCallerFPOffset);

  // Last location described by this entry.
  w->Write<uint8_t>(DW_CFA_SET_LOC);
  w->Write<uint64_t>(desc_->CodeEnd());
}


1778
bool UnwindInfoSection::WriteBodyInternal(Writer* w) {
1779 1780 1781 1782 1783 1784 1785 1786
  uint32_t cie_position = WriteCIE(w);
  WriteFDE(w, cie_position);
  return true;
}


#endif  // V8_TARGET_ARCH_X64

1787 1788 1789
static void CreateDWARFSections(CodeDescription* desc,
                                Zone* zone,
                                DebugObject* obj) {
1790
  if (desc->IsLineInfoAvailable()) {
1791 1792 1793
    obj->AddSection(new(zone) DebugInfoSection(desc));
    obj->AddSection(new(zone) DebugAbbrevSection(desc));
    obj->AddSection(new(zone) DebugLineSection(desc));
1794
  }
1795
#if V8_TARGET_ARCH_X64
1796
  obj->AddSection(new(zone) UnwindInfoSection(desc));
1797
#endif
1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820
}


// -------------------------------------------------------------------
// Binary GDB JIT Interface as described in
//   http://sourceware.org/gdb/onlinedocs/gdb/Declarations.html
extern "C" {
  typedef enum {
    JIT_NOACTION = 0,
    JIT_REGISTER_FN,
    JIT_UNREGISTER_FN
  } JITAction;

  struct JITCodeEntry {
    JITCodeEntry* next_;
    JITCodeEntry* prev_;
    Address symfile_addr_;
    uint64_t symfile_size_;
  };

  struct JITDescriptor {
    uint32_t version_;
    uint32_t action_flag_;
1821 1822
    JITCodeEntry* relevant_entry_;
    JITCodeEntry* first_entry_;
1823 1824 1825 1826 1827 1828
  };

  // GDB will place breakpoint into this function.
  // To prevent GCC from inlining or removing it we place noinline attribute
  // and inline assembler statement inside.
  void __attribute__((noinline)) __jit_debug_register_code() {
1829
    __asm__("");
1830 1831 1832 1833 1834
  }

  // GDB will inspect contents of this descriptor.
  // Static initialization is necessary to prevent GDB from seeing
  // uninitialized descriptor.
1835
  JITDescriptor __jit_debug_descriptor = {1, 0, nullptr, nullptr};
1836 1837

#ifdef OBJECT_PRINT
1838
  void __gdb_print_v8_object(Object object) {
1839
    StdoutStream os;
1840
    object->Print(os);
1841
    os << std::flush;
1842 1843
  }
#endif
1844 1845 1846 1847 1848 1849 1850 1851 1852 1853
}


static JITCodeEntry* CreateCodeEntry(Address symfile_addr,
                                     uintptr_t symfile_size) {
  JITCodeEntry* entry = static_cast<JITCodeEntry*>(
      malloc(sizeof(JITCodeEntry) + symfile_size));

  entry->symfile_addr_ = reinterpret_cast<Address>(entry + 1);
  entry->symfile_size_ = symfile_size;
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  MemCopy(reinterpret_cast<void*>(entry->symfile_addr_),
          reinterpret_cast<void*>(symfile_addr), symfile_size);
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  entry->prev_ = entry->next_ = nullptr;
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  return entry;
}


static void DestroyCodeEntry(JITCodeEntry* entry) {
  free(entry);
}


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static void RegisterCodeEntry(JITCodeEntry* entry) {
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  entry->next_ = __jit_debug_descriptor.first_entry_;
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  if (entry->next_ != nullptr) entry->next_->prev_ = entry;
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  __jit_debug_descriptor.first_entry_ =
      __jit_debug_descriptor.relevant_entry_ = entry;

  __jit_debug_descriptor.action_flag_ = JIT_REGISTER_FN;
  __jit_debug_register_code();
}


static void UnregisterCodeEntry(JITCodeEntry* entry) {
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  if (entry->prev_ != nullptr) {
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    entry->prev_->next_ = entry->next_;
  } else {
    __jit_debug_descriptor.first_entry_ = entry->next_;
  }

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  if (entry->next_ != nullptr) {
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    entry->next_->prev_ = entry->prev_;
  }

  __jit_debug_descriptor.relevant_entry_ = entry;
  __jit_debug_descriptor.action_flag_ = JIT_UNREGISTER_FN;
  __jit_debug_register_code();
}


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static JITCodeEntry* CreateELFObject(CodeDescription* desc, Isolate* isolate) {
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#ifdef __MACH_O
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  Zone zone(isolate->allocator(), ZONE_NAME);
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  MachO mach_o(&zone);
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  Writer w(&mach_o);

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  mach_o.AddSection(new(&zone) MachOTextSection(kCodeAlignment,
                                                desc->CodeStart(),
                                                desc->CodeSize()));
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  CreateDWARFSections(desc, &zone, &mach_o);
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  mach_o.Write(&w, desc->CodeStart(), desc->CodeSize());
#else
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  Zone zone(isolate->allocator(), ZONE_NAME);
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  ELF elf(&zone);
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  Writer w(&elf);

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  size_t text_section_index = elf.AddSection(new (&zone) FullHeaderELFSection(
      ".text", ELFSection::TYPE_NOBITS, kCodeAlignment, desc->CodeStart(), 0,
      desc->CodeSize(), ELFSection::FLAG_ALLOC | ELFSection::FLAG_EXEC));
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  CreateSymbolsTable(desc, &zone, &elf, text_section_index);
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  CreateDWARFSections(desc, &zone, &elf);
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  elf.Write(&w);
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#endif
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  return CreateCodeEntry(reinterpret_cast<Address>(w.buffer()), w.position());
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}


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struct AddressRange {
  Address start;
  Address end;
};
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struct SplayTreeConfig {
  typedef AddressRange Key;
  typedef JITCodeEntry* Value;
  static const AddressRange kNoKey;
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  static Value NoValue() { return nullptr; }
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  static int Compare(const AddressRange& a, const AddressRange& b) {
    // ptrdiff_t probably doesn't fit in an int.
    if (a.start < b.start) return -1;
    if (a.start == b.start) return 0;
    return 1;
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  }
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};
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const AddressRange SplayTreeConfig::kNoKey = {0, 0};
typedef SplayTree<SplayTreeConfig> CodeMap;
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static CodeMap* GetCodeMap() {
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  static CodeMap* code_map = nullptr;
  if (code_map == nullptr) code_map = new CodeMap();
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  return code_map;
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}


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static uint32_t HashCodeAddress(Address addr) {
  static const uintptr_t kGoldenRatio = 2654435761u;
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  return static_cast<uint32_t>((addr >> kCodeAlignmentBits) * kGoldenRatio);
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}

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static base::HashMap* GetLineMap() {
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  static base::HashMap* line_map = nullptr;
  if (line_map == nullptr) {
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    line_map = new base::HashMap();
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  }
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  return line_map;
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}


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static void PutLineInfo(Address addr, LineInfo* info) {
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  base::HashMap* line_map = GetLineMap();
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  base::HashMap::Entry* e = line_map->LookupOrInsert(
      reinterpret_cast<void*>(addr), HashCodeAddress(addr));
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  if (e->value != nullptr) delete static_cast<LineInfo*>(e->value);
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  e->value = info;
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}


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static LineInfo* GetLineInfo(Address addr) {
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  void* value = GetLineMap()->Remove(reinterpret_cast<void*>(addr),
                                     HashCodeAddress(addr));
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  return static_cast<LineInfo*>(value);
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}

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static void AddUnwindInfo(CodeDescription* desc) {
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#if V8_TARGET_ARCH_X64
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  if (desc->is_function()) {
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    // To avoid propagating unwinding information through
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    // compilation pipeline we use an approximation.
    // For most use cases this should not affect usability.
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    static const int kFramePointerPushOffset = 1;
    static const int kFramePointerSetOffset = 4;
    static const int kFramePointerPopOffset = -3;

    uintptr_t frame_pointer_push_address =
        desc->CodeStart() + kFramePointerPushOffset;

    uintptr_t frame_pointer_set_address =
        desc->CodeStart() + kFramePointerSetOffset;

    uintptr_t frame_pointer_pop_address =
        desc->CodeEnd() + kFramePointerPopOffset;

    desc->SetStackStateStartAddress(CodeDescription::POST_RBP_PUSH,
                                    frame_pointer_push_address);
    desc->SetStackStateStartAddress(CodeDescription::POST_RBP_SET,
                                    frame_pointer_set_address);
    desc->SetStackStateStartAddress(CodeDescription::POST_RBP_POP,
                                    frame_pointer_pop_address);
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  } else {
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    desc->SetStackStateStartAddress(CodeDescription::POST_RBP_PUSH,
                                    desc->CodeStart());
    desc->SetStackStateStartAddress(CodeDescription::POST_RBP_SET,
                                    desc->CodeStart());
    desc->SetStackStateStartAddress(CodeDescription::POST_RBP_POP,
                                    desc->CodeEnd());
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  }
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#endif  // V8_TARGET_ARCH_X64
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}


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static base::LazyMutex mutex = LAZY_MUTEX_INITIALIZER;
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// Remove entries from the splay tree that intersect the given address range,
// and deregister them from GDB.
static void RemoveJITCodeEntries(CodeMap* map, const AddressRange& range) {
  DCHECK(range.start < range.end);
  CodeMap::Locator cur;
  if (map->FindGreatestLessThan(range, &cur) || map->FindLeast(&cur)) {
    // Skip entries that are entirely less than the range of interest.
    while (cur.key().end <= range.start) {
      // CodeMap::FindLeastGreaterThan succeeds for entries whose key is greater
      // than _or equal to_ the given key, so we have to advance our key to get
      // the next one.
      AddressRange new_key;
      new_key.start = cur.key().end;
      new_key.end = 0;
      if (!map->FindLeastGreaterThan(new_key, &cur)) return;
    }
    // Evict intersecting ranges.
    while (cur.key().start < range.end) {
      AddressRange old_range = cur.key();
      JITCodeEntry* old_entry = cur.value();

      UnregisterCodeEntry(old_entry);
      DestroyCodeEntry(old_entry);

      CHECK(map->Remove(old_range));
      if (!map->FindLeastGreaterThan(old_range, &cur)) return;
    }
  }
}


// Insert the entry into the splay tree and register it with GDB.
static void AddJITCodeEntry(CodeMap* map, const AddressRange& range,
                            JITCodeEntry* entry, bool dump_if_enabled,
                            const char* name_hint) {
#if defined(DEBUG) && !V8_OS_WIN
  static int file_num = 0;
  if (FLAG_gdbjit_dump && dump_if_enabled) {
    static const int kMaxFileNameSize = 64;
    char file_name[64];

    SNPrintF(Vector<char>(file_name, kMaxFileNameSize), "/tmp/elfdump%s%d.o",
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             (name_hint != nullptr) ? name_hint : "", file_num++);
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    WriteBytes(file_name, reinterpret_cast<byte*>(entry->symfile_addr_),
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               static_cast<int>(entry->symfile_size_));
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  }
#endif

  CodeMap::Locator cur;
  CHECK(map->Insert(range, &cur));
  cur.set_value(entry);

  RegisterCodeEntry(entry);
}

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static void AddCode(const char* name, Code code, SharedFunctionInfo shared,
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                    LineInfo* lineinfo) {
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  DisallowHeapAllocation no_gc;
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  CodeMap* code_map = GetCodeMap();
  AddressRange range;
  range.start = code->address();
  range.end = code->address() + code->CodeSize();
  RemoveJITCodeEntries(code_map, range);
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  CodeDescription code_desc(name, code, shared, lineinfo);
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  if (!FLAG_gdbjit_full && !code_desc.IsLineInfoAvailable()) {
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    delete lineinfo;
    return;
  }

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  AddUnwindInfo(&code_desc);
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  Isolate* isolate = code->GetIsolate();
  JITCodeEntry* entry = CreateELFObject(&code_desc, isolate);
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  delete lineinfo;

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  const char* name_hint = nullptr;
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  bool should_dump = false;
  if (FLAG_gdbjit_dump) {
    if (strlen(FLAG_gdbjit_dump_filter) == 0) {
      name_hint = name;
      should_dump = true;
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    } else if (name != nullptr) {
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      name_hint = strstr(name, FLAG_gdbjit_dump_filter);
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      should_dump = (name_hint != nullptr);
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    }
  }
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  AddJITCodeEntry(code_map, range, entry, should_dump, name_hint);
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}

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void EventHandler(const v8::JitCodeEvent* event) {
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  if (!FLAG_gdbjit) return;
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  if (event->code_type != v8::JitCodeEvent::JIT_CODE) return;
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  base::MutexGuard lock_guard(mutex.Pointer());
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  switch (event->type) {
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    case v8::JitCodeEvent::CODE_ADDED: {
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      Address addr = reinterpret_cast<Address>(event->code_start);
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      Isolate* isolate = reinterpret_cast<Isolate*>(event->isolate);
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      Code code = isolate->heap()->GcSafeFindCodeForInnerPointer(addr);
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      LineInfo* lineinfo = GetLineInfo(addr);
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      EmbeddedVector<char, 256> buffer;
      StringBuilder builder(buffer.start(), buffer.length());
      builder.AddSubstring(event->name.str, static_cast<int>(event->name.len));
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      // It's called UnboundScript in the API but it's a SharedFunctionInfo.
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      SharedFunctionInfo shared = event->script.IsEmpty()
                                      ? SharedFunctionInfo()
                                      : *Utils::OpenHandle(*event->script);
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      AddCode(builder.Finalize(), code, shared, lineinfo);
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      break;
    }
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    case v8::JitCodeEvent::CODE_MOVED:
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      // Enabling the GDB JIT interface should disable code compaction.
      UNREACHABLE();
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      break;
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    case v8::JitCodeEvent::CODE_REMOVED:
      // Do nothing.  Instead, adding code causes eviction of any entry whose
      // address range intersects the address range of the added code.
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      break;
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    case v8::JitCodeEvent::CODE_ADD_LINE_POS_INFO: {
      LineInfo* line_info = reinterpret_cast<LineInfo*>(event->user_data);
      line_info->SetPosition(static_cast<intptr_t>(event->line_info.offset),
                             static_cast<int>(event->line_info.pos),
                             event->line_info.position_type ==
                                 v8::JitCodeEvent::STATEMENT_POSITION);
      break;
    }
    case v8::JitCodeEvent::CODE_START_LINE_INFO_RECORDING: {
      v8::JitCodeEvent* mutable_event = const_cast<v8::JitCodeEvent*>(event);
      mutable_event->user_data = new LineInfo();
      break;
    }
    case v8::JitCodeEvent::CODE_END_LINE_INFO_RECORDING: {
      LineInfo* line_info = reinterpret_cast<LineInfo*>(event->user_data);
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      PutLineInfo(reinterpret_cast<Address>(event->code_start), line_info);
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      break;
    }
  }
}
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#endif
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}  // namespace GDBJITInterface
}  // namespace internal
}  // namespace v8