gdb-jit.cc 61.1 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/diagnostics/gdb-jit.h"
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#include <map>
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#include <memory>
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#include <vector>
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#include "src/api/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/execution/frames-inl.h"
#include "src/execution/frames.h"
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#include "src/handles/global-handles.h"
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#include "src/init/bootstrapper.h"
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#include "src/objects/objects.h"
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#include "src/utils/ostreams.h"
#include "src/utils/vector.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;
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using DebugObject = MachO;
using DebugSection = MachOSection;
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#else
#define __ELF
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class ELF;
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class ELFSection;
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using DebugObject = ELF;
using DebugSection = ELFSection;
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#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),
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        buffer_(reinterpret_cast<byte*>(malloc(capacity_))) {}
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  ~Writer() { free(buffer_); }
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  uintptr_t position() const { return position_; }
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  template <typename T>
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  class Slot {
   public:
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    Slot(Writer* w, uintptr_t offset) : w_(w), offset_(offset) {}
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    T* operator->() { return w_->RawSlotAt<T>(offset_); }
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    void set(const T& value) { *w_->RawSlotAt<T>(offset_) = value; }
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    Slot<T> at(int i) { return Slot<T>(w_, offset_ + sizeof(T) * i); }
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   private:
    Writer* w_;
    uintptr_t offset_;
  };

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

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

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

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  template <typename T>
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  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:
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  template <typename T>
  friend class Slot;
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  template <typename T>
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  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>
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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) { return false; }
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  using Header = THeader;
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};

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_ = base::bits::WhichPowerOfTwo(align_);
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    }
  }

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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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  };

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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)
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      : 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:
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  FullHeaderELFSection(const char* name, Type type, uintptr_t align,
                       uintptr_t addr, uintptr_t offset, uintptr_t size,
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                       uintptr_t flags)
      : ELFSection(name, type, align),
        addr_(addr),
        offset_(offset),
        size_(size),
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        flags_(flags) {}
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 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();
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    Writer::Slot<MachOSegmentCommand> cmd =
        WriteSegmentCommand(w, code_start, code_size);
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    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;
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    header->cputype = 7;     // i386
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    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
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    header->cpusubtype = 3;            // CPU_SUBTYPE_I386_ALL
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    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);
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    cmd->cmdsize = sizeof(MachOSegmentCommand) +
                   sizeof(MachOSection::Header) * cmd->nsects;
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    return cmd;
  }

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  void WriteSections(Writer* w, Writer::Slot<MachOSegmentCommand> cmd,
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                     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
  };

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  ELFSymbol(const char* name, uintptr_t value, uintptr_t size, Binding binding,
            Type type, uint16_t section)
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      : name(name),
        value(value),
        size(size),
        info((binding << 4) | type),
        other(0),
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        section(section) {}
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  Binding binding() const { return static_cast<Binding>(info >> 4); }
#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 {
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    SerializedLayout(uint32_t name, uintptr_t value, uintptr_t size,
                     Binding binding, Type type, uint16_t section)
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        : name(name),
          value(value),
          size(size),
          info((binding << 4) | type),
          other(0),
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          section(section) {}
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    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 || \
    V8_TARGET_ARCH_PPC64 && V8_OS_LINUX || V8_TARGET_ARCH_S390X
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  struct SerializedLayout {
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    SerializedLayout(uint32_t name, uintptr_t value, uintptr_t size,
                     Binding binding, Type type, uint16_t section)
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        : name(name),
          info((binding << 4) | type),
          other(0),
          section(section),
          value(value),
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          size(size) {}
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    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);
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    symbols.at(0).set(ELFSymbol::SerializedLayout(
        0, 0, 0, ELFSymbol::BIND_LOCAL, ELFSymbol::TYPE_NOTYPE, 0));
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    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_;
858
};
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#endif  // defined(__ELF)
860

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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:
879
  void AddPCInfo(const PCInfo& pc_info) { pc_info_.push_back(pc_info); }
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881
  std::vector<PCInfo> pc_info_;
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};

884
class CodeDescription {
885
 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) {}
898

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  const char* name() const { return name_; }
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901
  LineInfo* lineinfo() const { return lineinfo_; }
902

903
  bool is_function() const {
904
    Code::Kind kind = code_.kind();
905
    return kind == Code::OPTIMIZED_FUNCTION;
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  }

908
  bool has_scope_info() const { return !shared_info_.is_null(); }
909

910
  ScopeInfo scope_info() const {
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    DCHECK(has_scope_info());
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    return shared_info_.scope_info();
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  }

915
  uintptr_t CodeStart() const {
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    return static_cast<uintptr_t>(code_.InstructionStart());
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  }

919
  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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931
  bool IsLineInfoAvailable() { return lineinfo_ != nullptr; }
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933
#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];
  }
938

939
  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

945
  std::unique_ptr<char[]> GetFilename() {
946
    if (!shared_info_.is_null()) {
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      return String::cast(script().name()).ToCString();
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    } else {
      std::unique_ptr<char[]> result(new char[1]);
      result[0] = 0;
      return result;
    }
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  }

955
  int GetScriptLineNumber(int pos) {
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    if (!shared_info_.is_null()) {
957
      return script().GetLineNumber(pos) + 1;
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    } else {
      return 0;
    }
  }
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 private:
  const char* name_;
965
  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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};

973
#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);
  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
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      : MachOSection("__debug_info", "__DWARF", 1,
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                     MachOSection::S_REGULAR | MachOSection::S_ATTR_DEBUG),
#endif
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        desc_(desc) {
  }
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  // 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
  };

1041
  enum DWARF2Encoding { DW_ATE_ADDRESS = 0x1, DW_ATE_SIGNED = 0x5 };
1042

1043
  bool WriteBodyInternal(Writer* w) override {
1044
    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());
1055
    w->Write<uint32_t>(0);
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    uint32_t ty_offset = static_cast<uint32_t>(w->position() - cu_start);
    w->WriteULEB128(3);
1059
    w->Write<uint8_t>(kSystemPointerSize);
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    w->WriteString("v8value");

1062
    if (desc_->has_scope_info()) {
1063
      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();
Jakob Kummerow's avatar
Jakob Kummerow committed
1070
#if V8_TARGET_ARCH_IA32
1071
      w->Write<uint8_t>(DW_OP_reg5);  // The frame pointer's here on ia32
1072
#elif V8_TARGET_ARCH_X64
1073
      w->Write<uint8_t>(DW_OP_reg6);  // and here on x64.
1074
#elif V8_TARGET_ARCH_ARM
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      UNIMPLEMENTED();
1076
#elif V8_TARGET_ARCH_MIPS
1077
      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();
      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;

1095
      EmbeddedVector<char, 256> buffer;
1096
      StringBuilder builder(buffer.begin(), buffer.length());
1097

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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(StandardFrameConstants::kFixedFrameSizeAboveFp +
1108
                        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, 3);
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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);
1117
      w->WriteULEB128(current_abbreviation++);
1118
      w->WriteString(".scope_info");
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      w->WriteULEB128(current_abbreviation++);
      w->WriteString(".previous");
      w->WriteULEB128(current_abbreviation++);
      w->WriteString(".extension");

1124
      for (int context_slot = 0; context_slot < context_slots; ++context_slot) {
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        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);
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        w->WriteSLEB128(StandardFrameConstants::kFunctionOffset);
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        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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    }

1156
    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_;
};

1165
class DebugAbbrevSection : public DebugSection {
1166
 public:
1167 1168 1169 1170
  explicit DebugAbbrevSection(CodeDescription* desc)
#ifdef __ELF
      : ELFSection(".debug_abbrev", TYPE_PROGBITS, 1),
#else
1171
      : MachOSection("__debug_abbrev", "__DWARF", 1,
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                     MachOSection::S_REGULAR | MachOSection::S_ATTR_DEBUG),
#endif
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        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.
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  enum DWARF2ChildrenDetermination { DW_CHILDREN_NO = 0, DW_CHILDREN_YES = 1 };
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  // 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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  };

1216 1217
  void WriteVariableAbbreviation(Writer* w, int abbreviation_code,
                                 bool has_value, bool is_parameter) {
1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232
    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);
  }

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  bool WriteBodyInternal(Writer* w) override {
1234
    int current_abbreviation = 1;
1235
    bool extra_info = desc_->has_scope_info();
1236
    DCHECK(desc_->IsLineInfoAvailable());
1237
    w->WriteULEB128(current_abbreviation++);
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    w->WriteULEB128(DW_TAG_COMPILE_UNIT);
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    w->Write<uint8_t>(extra_info ? DW_CHILDREN_YES : DW_CHILDREN_NO);
1240 1241 1242 1243 1244 1245 1246 1247 1248 1249
    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);
1250 1251

    if (extra_info) {
1252
      ScopeInfo scope = desc_->scope_info();
1253 1254
      int params = scope.ParameterCount();
      int context_slots = scope.ContextLocalCount();
1255 1256
      // The real slot ID is internal_slots + context_slot_id.
      int internal_slots = Context::MIN_CONTEXT_SLOTS;
1257 1258
      // Total children is params + context_slots + internal_slots + 2
      // (__function and __context).
1259 1260 1261 1262 1263

      // 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);
1264
      w->Write<uint8_t>(DW_CHILDREN_YES);
1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289
      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);
      }

1290
      for (int internal_slot = 0; internal_slot < internal_slots;
1291 1292 1293 1294
           ++internal_slot) {
        WriteVariableAbbreviation(w, current_abbreviation++, false, false);
      }

1295
      for (int context_slot = 0; context_slot < context_slots; ++context_slot) {
1296 1297 1298 1299 1300 1301 1302 1303 1304
        WriteVariableAbbreviation(w, current_abbreviation++, false, false);
      }

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

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

1305
      w->WriteULEB128(0);  // Terminate the sibling list.
1306 1307 1308
    }

    w->WriteULEB128(0);  // Terminate the table.
1309 1310
    return true;
  }
1311 1312 1313

 private:
  CodeDescription* desc_;
1314 1315
};

1316
class DebugLineSection : public DebugSection {
1317 1318
 public:
  explicit DebugLineSection(CodeDescription* desc)
1319
#ifdef __ELF
1320
      : ELFSection(".debug_line", TYPE_PROGBITS, 1),
1321
#else
1322
      : MachOSection("__debug_line", "__DWARF", 1,
1323 1324
                     MachOSection::S_REGULAR | MachOSection::S_ATTR_DEBUG),
#endif
1325 1326
        desc_(desc) {
  }
1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344

  // 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
  };

1345
  bool WriteBodyInternal(Writer* w) override {
1346 1347 1348 1349
    // Write prologue.
    Writer::Slot<uint32_t> total_length = w->CreateSlotHere<uint32_t>();
    uintptr_t start = w->position();

1350 1351 1352 1353 1354 1355
    // 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;

1356 1357 1358
    w->Write<uint16_t>(2);  // Field version.
    Writer::Slot<uint32_t> prologue_length = w->CreateSlotHere<uint32_t>();
    uintptr_t prologue_start = w->position();
1359 1360 1361 1362
    w->Write<uint8_t>(1);            // Field minimum_instruction_length.
    w->Write<uint8_t>(1);            // Field default_is_stmt.
    w->Write<int8_t>(line_base);     // Field line_base.
    w->Write<uint8_t>(line_range);   // Field line_range.
1363
    w->Write<uint8_t>(opcode_base);  // Field opcode_base.
1364 1365 1366 1367 1368 1369 1370
    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.
1371
    w->WriteString(desc_->GetFilename().get());  // File name.
1372 1373 1374
    w->WriteULEB128(0);                          // Current directory.
    w->WriteULEB128(0);                          // Unknown modification time.
    w->WriteULEB128(0);                          // Unknown file size.
1375 1376 1377 1378
    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));
1379
    w->Write<intptr_t>(desc_->CodeStart());
1380
    w->Write<uint8_t>(DW_LNS_COPY);
1381 1382 1383 1384 1385

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

1386 1387
    std::vector<LineInfo::PCInfo>* pc_info = desc_->lineinfo()->pc_info();
    std::sort(pc_info->begin(), pc_info->end(), &ComparePCInfo);
1388

1389
    for (size_t i = 0; i < pc_info->size(); i++) {
1390
      LineInfo::PCInfo* info = &pc_info->at(i);
1391
      DCHECK(info->pc_ >= pc);
1392 1393 1394

      // Reduce bloating in the debug line table by removing duplicate line
      // entries (per DWARF2 standard).
1395
      intptr_t new_line = desc_->GetScriptLineNumber(info->pos_);
1396 1397
      if (new_line == line) {
        continue;
1398
      }
1399 1400 1401 1402 1403

      // 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.
1404
      if ((i + 1) == pc_info->size()) {
1405 1406 1407 1408
        if (!is_statement) {
          w->Write<uint8_t>(DW_LNS_NEGATE_STMT);
        }
      } else if (is_statement != info->is_statement_) {
1409 1410 1411
        w->Write<uint8_t>(DW_LNS_NEGATE_STMT);
        is_statement = !is_statement;
      }
1412 1413 1414 1415 1416 1417 1418 1419

      // 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)
1420 1421
      intptr_t special_opcode =
          (line_diff - line_base) + (line_range * pc_diff) + opcode_base;
1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435

      // 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);
1436 1437
        w->Write<uint8_t>(DW_LNS_COPY);
      }
1438 1439 1440 1441

      // Increment the pc and line operands.
      pc += pc_diff;
      line += line_diff;
1442
    }
1443 1444 1445 1446
    // 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);
1447 1448 1449 1450 1451 1452
    WriteExtendedOpcode(w, DW_LNE_END_SEQUENCE, 0);
    total_length.set(static_cast<uint32_t>(w->position() - start));
    return true;
  }

 private:
1453
  void WriteExtendedOpcode(Writer* w, DWARF2ExtendedOpcode op,
1454 1455 1456 1457 1458 1459
                           size_t operands_size) {
    w->Write<uint8_t>(0);
    w->WriteULEB128(operands_size + 1);
    w->Write<uint8_t>(op);
  }

1460 1461 1462 1463 1464
  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_;
1465
      }
1466
      return false;
1467
    }
1468
    return a.pc_ < b.pc_;
1469 1470 1471 1472 1473
  }

  CodeDescription* desc_;
};

1474
#if V8_TARGET_ARCH_X64
1475

1476
class UnwindInfoSection : public DebugSection {
1477
 public:
1478
  explicit UnwindInfoSection(CodeDescription* desc);
1479
  bool WriteBodyInternal(Writer* w) override;
1480

1481 1482
  int WriteCIE(Writer* w);
  void WriteFDE(Writer* w, int);
1483

1484 1485 1486 1487
  void WriteFDEStateOnEntry(Writer* w);
  void WriteFDEStateAfterRBPPush(Writer* w);
  void WriteFDEStateAfterRBPSet(Writer* w);
  void WriteFDEStateAfterRBPPop(Writer* w);
1488

1489
  void WriteLength(Writer* w, Writer::Slot<uint32_t>* length_slot,
1490 1491 1492
                   int initial_position);

 private:
1493
  CodeDescription* desc_;
1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542

  // 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
  };
};

1543
void UnwindInfoSection::WriteLength(Writer* w,
1544 1545
                                    Writer::Slot<uint32_t>* length_slot,
                                    int initial_position) {
1546
  uint32_t align = (w->position() - initial_position) % kSystemPointerSize;
1547 1548

  if (align != 0) {
1549
    for (uint32_t i = 0; i < (kSystemPointerSize - align); i++) {
1550 1551 1552 1553
      w->Write<uint8_t>(DW_CFA_NOP);
    }
  }

1554
  DCHECK_EQ((w->position() - initial_position) % kSystemPointerSize, 0);
1555
  length_slot->set(static_cast<uint32_t>(w->position() - initial_position));
1556 1557
}

1558
UnwindInfoSection::UnwindInfoSection(CodeDescription* desc)
1559 1560 1561 1562 1563 1564
#ifdef __ELF
    : ELFSection(".eh_frame", TYPE_X86_64_UNWIND, 1),
#else
    : MachOSection("__eh_frame", "__TEXT", sizeof(uintptr_t),
                   MachOSection::S_REGULAR),
#endif
1565 1566
      desc_(desc) {
}
1567

1568
int UnwindInfoSection::WriteCIE(Writer* w) {
1569
  Writer::Slot<uint32_t> cie_length_slot = w->CreateSlotHere<uint32_t>();
1570
  uint32_t cie_position = static_cast<uint32_t>(w->position());
1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586

  // 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;
}

1587
void UnwindInfoSection::WriteFDE(Writer* w, int cie_position) {
1588 1589
  // The only FDE for this function. The CFA is the current RBP.
  Writer::Slot<uint32_t> fde_length_slot = w->CreateSlotHere<uint32_t>();
1590
  int fde_position = static_cast<uint32_t>(w->position());
1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603
  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);
}

1604
void UnwindInfoSection::WriteFDEStateOnEntry(Writer* w) {
1605 1606 1607 1608 1609 1610 1611
  // 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);
1612
  w->WriteSLEB128(-kSystemPointerSize);
1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629

  // 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));
}

1630
void UnwindInfoSection::WriteFDEStateAfterRBPPush(Writer* w) {
1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649
  // 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));
}

1650
void UnwindInfoSection::WriteFDEStateAfterRBPSet(Writer* w) {
1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663
  // 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));
}

1664
void UnwindInfoSection::WriteFDEStateAfterRBPPop(Writer* w) {
1665 1666 1667 1668 1669 1670
  // 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);
1671
  w->WriteSLEB128(-kSystemPointerSize);
1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682

  // 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());
}

1683
bool UnwindInfoSection::WriteBodyInternal(Writer* w) {
1684 1685 1686 1687 1688 1689 1690
  uint32_t cie_position = WriteCIE(w);
  WriteFDE(w, cie_position);
  return true;
}

#endif  // V8_TARGET_ARCH_X64

1691
static void CreateDWARFSections(CodeDescription* desc, Zone* zone,
1692
                                DebugObject* obj) {
1693
  if (desc->IsLineInfoAvailable()) {
1694 1695 1696
    obj->AddSection(new (zone) DebugInfoSection(desc));
    obj->AddSection(new (zone) DebugAbbrevSection(desc));
    obj->AddSection(new (zone) DebugLineSection(desc));
1697
  }
1698
#if V8_TARGET_ARCH_X64
1699
  obj->AddSection(new (zone) UnwindInfoSection(desc));
1700
#endif
1701 1702 1703 1704 1705 1706
}

// -------------------------------------------------------------------
// Binary GDB JIT Interface as described in
//   http://sourceware.org/gdb/onlinedocs/gdb/Declarations.html
extern "C" {
1707
enum JITAction { JIT_NOACTION = 0, JIT_REGISTER_FN, JIT_UNREGISTER_FN };
1708

1709 1710 1711 1712 1713 1714
struct JITCodeEntry {
  JITCodeEntry* next_;
  JITCodeEntry* prev_;
  Address symfile_addr_;
  uint64_t symfile_size_;
};
1715

1716 1717 1718 1719 1720 1721
struct JITDescriptor {
  uint32_t version_;
  uint32_t action_flag_;
  JITCodeEntry* relevant_entry_;
  JITCodeEntry* first_entry_;
};
1722

1723 1724 1725 1726 1727 1728 1729 1730 1731
// 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() { __asm__(""); }

// GDB will inspect contents of this descriptor.
// Static initialization is necessary to prevent GDB from seeing
// uninitialized descriptor.
JITDescriptor __jit_debug_descriptor = {1, 0, nullptr, nullptr};
1732 1733

#ifdef OBJECT_PRINT
1734 1735
void __gdb_print_v8_object(Object object) {
  StdoutStream os;
1736
  object.Print(os);
1737 1738
  os << std::flush;
}
1739
#endif
1740 1741 1742 1743
}

static JITCodeEntry* CreateCodeEntry(Address symfile_addr,
                                     uintptr_t symfile_size) {
1744 1745
  JITCodeEntry* entry =
      static_cast<JITCodeEntry*>(malloc(sizeof(JITCodeEntry) + symfile_size));
1746 1747 1748

  entry->symfile_addr_ = reinterpret_cast<Address>(entry + 1);
  entry->symfile_size_ = symfile_size;
1749 1750
  MemCopy(reinterpret_cast<void*>(entry->symfile_addr_),
          reinterpret_cast<void*>(symfile_addr), symfile_size);
1751

1752
  entry->prev_ = entry->next_ = nullptr;
1753 1754 1755 1756

  return entry;
}

1757
static void DestroyCodeEntry(JITCodeEntry* entry) { free(entry); }
1758

1759
static void RegisterCodeEntry(JITCodeEntry* entry) {
1760
  entry->next_ = __jit_debug_descriptor.first_entry_;
1761
  if (entry->next_ != nullptr) entry->next_->prev_ = entry;
1762 1763
  __jit_debug_descriptor.first_entry_ = __jit_debug_descriptor.relevant_entry_ =
      entry;
1764 1765 1766 1767 1768 1769

  __jit_debug_descriptor.action_flag_ = JIT_REGISTER_FN;
  __jit_debug_register_code();
}

static void UnregisterCodeEntry(JITCodeEntry* entry) {
1770
  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 AddressRangeLess {
  bool operator()(const AddressRange& a, const AddressRange& b) const {
    if (a.start == b.start) return a.end < b.end;
    return a.start < b.start;
  }
};

struct CodeMapConfig {
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  using Key = AddressRange;
  using Value = JITCodeEntry*;
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  using Less = AddressRangeLess;
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};
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using CodeMap =
    std::map<CodeMapConfig::Key, CodeMapConfig::Value, CodeMapConfig::Less>;
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static CodeMap* GetCodeMap() {
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  // TODO(jgruber): Don't leak.
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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 map that intersect the given address range,
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// and deregister them from GDB.
static void RemoveJITCodeEntries(CodeMap* map, const AddressRange& range) {
  DCHECK(range.start < range.end);

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  if (map->empty()) return;

  // Find the first overlapping entry.
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  // If successful, points to the first element not less than `range`. The
  // returned iterator has the key in `first` and the value in `second`.
  auto it = map->lower_bound(range);
  auto start_it = it;

  if (it == map->end()) {
    start_it = map->begin();
  } else if (it != map->begin()) {
    for (--it; it != map->begin(); --it) {
      if ((*it).first.end <= range.start) break;
      start_it = it;
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    }
  }
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  DCHECK(start_it != map->end());

  // Find the first non-overlapping entry after `range`.

  const auto end_it = map->lower_bound({range.end, 0});

  // Evict intersecting ranges.

  if (std::distance(start_it, end_it) < 1) return;  // No overlapping entries.

  for (auto it = start_it; it != end_it; it++) {
    JITCodeEntry* old_entry = (*it).second;
    UnregisterCodeEntry(old_entry);
    DestroyCodeEntry(old_entry);
  }

  map->erase(start_it, end_it);
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}

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// Insert the entry into the map and register it with GDB.
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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

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  auto result = map->emplace(range, entry);
  DCHECK(result.second);  // Insertion happened.
  USE(result);
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  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;
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  range.start = code.address();
  range.end = code.address() + code.CodeSize();
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  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();
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  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;
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      StringBuilder builder(buffer.begin(), buffer.length());
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      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();
    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
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#undef __MACH_O
#undef __ELF