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      1 // Copyright 2010 the V8 project authors. All rights reserved.
      2 // Redistribution and use in source and binary forms, with or without
      3 // modification, are permitted provided that the following conditions are
      4 // met:
      5 //
      6 //     * Redistributions of source code must retain the above copyright
      7 //       notice, this list of conditions and the following disclaimer.
      8 //     * Redistributions in binary form must reproduce the above
      9 //       copyright notice, this list of conditions and the following
     10 //       disclaimer in the documentation and/or other materials provided
     11 //       with the distribution.
     12 //     * Neither the name of Google Inc. nor the names of its
     13 //       contributors may be used to endorse or promote products derived
     14 //       from this software without specific prior written permission.
     15 //
     16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27 
     28 #ifdef ENABLE_GDB_JIT_INTERFACE
     29 #include "v8.h"
     30 #include "gdb-jit.h"
     31 
     32 #include "bootstrapper.h"
     33 #include "compiler.h"
     34 #include "global-handles.h"
     35 #include "messages.h"
     36 #include "platform.h"
     37 #include "natives.h"
     38 #include "scopeinfo.h"
     39 
     40 namespace v8 {
     41 namespace internal {
     42 
     43 #ifdef __APPLE__
     44 #define __MACH_O
     45 class MachO;
     46 class MachOSection;
     47 typedef MachO DebugObject;
     48 typedef MachOSection DebugSection;
     49 #else
     50 #define __ELF
     51 class ELF;
     52 class ELFSection;
     53 typedef ELF DebugObject;
     54 typedef ELFSection DebugSection;
     55 #endif
     56 
     57 class Writer BASE_EMBEDDED {
     58  public:
     59   explicit Writer(DebugObject* debug_object)
     60       : debug_object_(debug_object),
     61         position_(0),
     62         capacity_(1024),
     63         buffer_(reinterpret_cast<byte*>(malloc(capacity_))) {
     64   }
     65 
     66   ~Writer() {
     67     free(buffer_);
     68   }
     69 
     70   uintptr_t position() const {
     71     return position_;
     72   }
     73 
     74   template<typename T>
     75   class Slot {
     76    public:
     77     Slot(Writer* w, uintptr_t offset) : w_(w), offset_(offset) { }
     78 
     79     T* operator-> () {
     80       return w_->RawSlotAt<T>(offset_);
     81     }
     82 
     83     void set(const T& value) {
     84       *w_->RawSlotAt<T>(offset_) = value;
     85     }
     86 
     87     Slot<T> at(int i) {
     88       return Slot<T>(w_, offset_ + sizeof(T) * i);
     89     }
     90 
     91    private:
     92     Writer* w_;
     93     uintptr_t offset_;
     94   };
     95 
     96   template<typename T>
     97   void Write(const T& val) {
     98     Ensure(position_ + sizeof(T));
     99     *RawSlotAt<T>(position_) = val;
    100     position_ += sizeof(T);
    101   }
    102 
    103   template<typename T>
    104   Slot<T> SlotAt(uintptr_t offset) {
    105     Ensure(offset + sizeof(T));
    106     return Slot<T>(this, offset);
    107   }
    108 
    109   template<typename T>
    110   Slot<T> CreateSlotHere() {
    111     return CreateSlotsHere<T>(1);
    112   }
    113 
    114   template<typename T>
    115   Slot<T> CreateSlotsHere(uint32_t count) {
    116     uintptr_t slot_position = position_;
    117     position_ += sizeof(T) * count;
    118     Ensure(position_);
    119     return SlotAt<T>(slot_position);
    120   }
    121 
    122   void Ensure(uintptr_t pos) {
    123     if (capacity_ < pos) {
    124       while (capacity_ < pos) capacity_ *= 2;
    125       buffer_ = reinterpret_cast<byte*>(realloc(buffer_, capacity_));
    126     }
    127   }
    128 
    129   DebugObject* debug_object() { return debug_object_; }
    130 
    131   byte* buffer() { return buffer_; }
    132 
    133   void Align(uintptr_t align) {
    134     uintptr_t delta = position_ % align;
    135     if (delta == 0) return;
    136     uintptr_t padding = align - delta;
    137     Ensure(position_ += padding);
    138     ASSERT((position_ % align) == 0);
    139   }
    140 
    141   void WriteULEB128(uintptr_t value) {
    142     do {
    143       uint8_t byte = value & 0x7F;
    144       value >>= 7;
    145       if (value != 0) byte |= 0x80;
    146       Write<uint8_t>(byte);
    147     } while (value != 0);
    148   }
    149 
    150   void WriteSLEB128(intptr_t value) {
    151     bool more = true;
    152     while (more) {
    153       int8_t byte = value & 0x7F;
    154       bool byte_sign = byte & 0x40;
    155       value >>= 7;
    156 
    157       if ((value == 0 && !byte_sign) || (value == -1 && byte_sign)) {
    158         more = false;
    159       } else {
    160         byte |= 0x80;
    161       }
    162 
    163       Write<int8_t>(byte);
    164     }
    165   }
    166 
    167   void WriteString(const char* str) {
    168     do {
    169       Write<char>(*str);
    170     } while (*str++);
    171   }
    172 
    173  private:
    174   template<typename T> friend class Slot;
    175 
    176   template<typename T>
    177   T* RawSlotAt(uintptr_t offset) {
    178     ASSERT(offset < capacity_ && offset + sizeof(T) <= capacity_);
    179     return reinterpret_cast<T*>(&buffer_[offset]);
    180   }
    181 
    182   DebugObject* debug_object_;
    183   uintptr_t position_;
    184   uintptr_t capacity_;
    185   byte* buffer_;
    186 };
    187 
    188 class StringTable;
    189 
    190 template<typename THeader>
    191 class DebugSectionBase : public ZoneObject {
    192  public:
    193   virtual ~DebugSectionBase() { }
    194 
    195   virtual void WriteBody(Writer::Slot<THeader> header, Writer* writer) {
    196     uintptr_t start = writer->position();
    197     if (WriteBody(writer)) {
    198       uintptr_t end = writer->position();
    199       header->offset = start;
    200 #if defined(__MACH_O)
    201       header->addr = 0;
    202 #endif
    203       header->size = end - start;
    204     }
    205   }
    206 
    207   virtual bool WriteBody(Writer* writer) {
    208     return false;
    209   }
    210 
    211   typedef THeader Header;
    212 };
    213 
    214 
    215 struct MachOSectionHeader {
    216   char sectname[16];
    217   char segname[16];
    218 #if defined(V8_TARGET_ARCH_IA32)
    219   uint32_t addr;
    220   uint32_t size;
    221 #else
    222   uint64_t addr;
    223   uint64_t size;
    224 #endif
    225   uint32_t offset;
    226   uint32_t align;
    227   uint32_t reloff;
    228   uint32_t nreloc;
    229   uint32_t flags;
    230   uint32_t reserved1;
    231   uint32_t reserved2;
    232 };
    233 
    234 
    235 class MachOSection : public DebugSectionBase<MachOSectionHeader> {
    236  public:
    237   enum Type {
    238     S_REGULAR = 0x0u,
    239     S_ATTR_COALESCED = 0xbu,
    240     S_ATTR_SOME_INSTRUCTIONS = 0x400u,
    241     S_ATTR_DEBUG = 0x02000000u,
    242     S_ATTR_PURE_INSTRUCTIONS = 0x80000000u
    243   };
    244 
    245   MachOSection(const char* name,
    246                const char* segment,
    247                uintptr_t align,
    248                uint32_t flags)
    249     : name_(name),
    250       segment_(segment),
    251       align_(align),
    252       flags_(flags) {
    253     ASSERT(IsPowerOf2(align));
    254     if (align_ != 0) {
    255       align_ = WhichPowerOf2(align_);
    256     }
    257   }
    258 
    259   virtual ~MachOSection() { }
    260 
    261   virtual void PopulateHeader(Writer::Slot<Header> header) {
    262     header->addr = 0;
    263     header->size = 0;
    264     header->offset = 0;
    265     header->align = align_;
    266     header->reloff = 0;
    267     header->nreloc = 0;
    268     header->flags = flags_;
    269     header->reserved1 = 0;
    270     header->reserved2 = 0;
    271     memset(header->sectname, 0, sizeof(header->sectname));
    272     memset(header->segname, 0, sizeof(header->segname));
    273     ASSERT(strlen(name_) < sizeof(header->sectname));
    274     ASSERT(strlen(segment_) < sizeof(header->segname));
    275     strncpy(header->sectname, name_, sizeof(header->sectname));
    276     strncpy(header->segname, segment_, sizeof(header->segname));
    277   }
    278 
    279  private:
    280   const char* name_;
    281   const char* segment_;
    282   uintptr_t align_;
    283   uint32_t flags_;
    284 };
    285 
    286 
    287 struct ELFSectionHeader {
    288   uint32_t name;
    289   uint32_t type;
    290   uintptr_t flags;
    291   uintptr_t address;
    292   uintptr_t offset;
    293   uintptr_t size;
    294   uint32_t link;
    295   uint32_t info;
    296   uintptr_t alignment;
    297   uintptr_t entry_size;
    298 };
    299 
    300 
    301 #if defined(__ELF)
    302 class ELFSection : public DebugSectionBase<ELFSectionHeader> {
    303  public:
    304   enum Type {
    305     TYPE_NULL = 0,
    306     TYPE_PROGBITS = 1,
    307     TYPE_SYMTAB = 2,
    308     TYPE_STRTAB = 3,
    309     TYPE_RELA = 4,
    310     TYPE_HASH = 5,
    311     TYPE_DYNAMIC = 6,
    312     TYPE_NOTE = 7,
    313     TYPE_NOBITS = 8,
    314     TYPE_REL = 9,
    315     TYPE_SHLIB = 10,
    316     TYPE_DYNSYM = 11,
    317     TYPE_LOPROC = 0x70000000,
    318     TYPE_X86_64_UNWIND = 0x70000001,
    319     TYPE_HIPROC = 0x7fffffff,
    320     TYPE_LOUSER = 0x80000000,
    321     TYPE_HIUSER = 0xffffffff
    322   };
    323 
    324   enum Flags {
    325     FLAG_WRITE = 1,
    326     FLAG_ALLOC = 2,
    327     FLAG_EXEC = 4
    328   };
    329 
    330   enum SpecialIndexes {
    331     INDEX_ABSOLUTE = 0xfff1
    332   };
    333 
    334   ELFSection(const char* name, Type type, uintptr_t align)
    335       : name_(name), type_(type), align_(align) { }
    336 
    337   virtual ~ELFSection() { }
    338 
    339   void PopulateHeader(Writer::Slot<Header> header, StringTable* strtab);
    340 
    341   virtual void WriteBody(Writer::Slot<Header> header, Writer* w) {
    342     uintptr_t start = w->position();
    343     if (WriteBody(w)) {
    344       uintptr_t end = w->position();
    345       header->offset = start;
    346       header->size = end - start;
    347     }
    348   }
    349 
    350   virtual bool WriteBody(Writer* w) {
    351     return false;
    352   }
    353 
    354   uint16_t index() const { return index_; }
    355   void set_index(uint16_t index) { index_ = index; }
    356 
    357  protected:
    358   virtual void PopulateHeader(Writer::Slot<Header> header) {
    359     header->flags = 0;
    360     header->address = 0;
    361     header->offset = 0;
    362     header->size = 0;
    363     header->link = 0;
    364     header->info = 0;
    365     header->entry_size = 0;
    366   }
    367 
    368  private:
    369   const char* name_;
    370   Type type_;
    371   uintptr_t align_;
    372   uint16_t index_;
    373 };
    374 #endif  // defined(__ELF)
    375 
    376 
    377 #if defined(__MACH_O)
    378 class MachOTextSection : public MachOSection {
    379  public:
    380   MachOTextSection(uintptr_t align,
    381                    uintptr_t addr,
    382                    uintptr_t size)
    383       : MachOSection("__text",
    384                      "__TEXT",
    385                      align,
    386                      MachOSection::S_REGULAR |
    387                          MachOSection::S_ATTR_SOME_INSTRUCTIONS |
    388                          MachOSection::S_ATTR_PURE_INSTRUCTIONS),
    389         addr_(addr),
    390         size_(size) { }
    391 
    392  protected:
    393   virtual void PopulateHeader(Writer::Slot<Header> header) {
    394     MachOSection::PopulateHeader(header);
    395     header->addr = addr_;
    396     header->size = size_;
    397   }
    398 
    399  private:
    400   uintptr_t addr_;
    401   uintptr_t size_;
    402 };
    403 #endif  // defined(__MACH_O)
    404 
    405 
    406 #if defined(__ELF)
    407 class FullHeaderELFSection : public ELFSection {
    408  public:
    409   FullHeaderELFSection(const char* name,
    410                        Type type,
    411                        uintptr_t align,
    412                        uintptr_t addr,
    413                        uintptr_t offset,
    414                        uintptr_t size,
    415                        uintptr_t flags)
    416       : ELFSection(name, type, align),
    417         addr_(addr),
    418         offset_(offset),
    419         size_(size),
    420         flags_(flags) { }
    421 
    422  protected:
    423   virtual void PopulateHeader(Writer::Slot<Header> header) {
    424     ELFSection::PopulateHeader(header);
    425     header->address = addr_;
    426     header->offset = offset_;
    427     header->size = size_;
    428     header->flags = flags_;
    429   }
    430 
    431  private:
    432   uintptr_t addr_;
    433   uintptr_t offset_;
    434   uintptr_t size_;
    435   uintptr_t flags_;
    436 };
    437 
    438 
    439 class StringTable : public ELFSection {
    440  public:
    441   explicit StringTable(const char* name)
    442       : ELFSection(name, TYPE_STRTAB, 1), writer_(NULL), offset_(0), size_(0) {
    443   }
    444 
    445   uintptr_t Add(const char* str) {
    446     if (*str == '\0') return 0;
    447 
    448     uintptr_t offset = size_;
    449     WriteString(str);
    450     return offset;
    451   }
    452 
    453   void AttachWriter(Writer* w) {
    454     writer_ = w;
    455     offset_ = writer_->position();
    456 
    457     // First entry in the string table should be an empty string.
    458     WriteString("");
    459   }
    460 
    461   void DetachWriter() {
    462     writer_ = NULL;
    463   }
    464 
    465   virtual void WriteBody(Writer::Slot<Header> header, Writer* w) {
    466     ASSERT(writer_ == NULL);
    467     header->offset = offset_;
    468     header->size = size_;
    469   }
    470 
    471  private:
    472   void WriteString(const char* str) {
    473     uintptr_t written = 0;
    474     do {
    475       writer_->Write(*str);
    476       written++;
    477     } while (*str++);
    478     size_ += written;
    479   }
    480 
    481   Writer* writer_;
    482 
    483   uintptr_t offset_;
    484   uintptr_t size_;
    485 };
    486 
    487 
    488 void ELFSection::PopulateHeader(Writer::Slot<ELFSection::Header> header,
    489                                 StringTable* strtab) {
    490   header->name = strtab->Add(name_);
    491   header->type = type_;
    492   header->alignment = align_;
    493   PopulateHeader(header);
    494 }
    495 #endif  // defined(__ELF)
    496 
    497 
    498 #if defined(__MACH_O)
    499 class MachO BASE_EMBEDDED {
    500  public:
    501   MachO() : sections_(6) { }
    502 
    503   uint32_t AddSection(MachOSection* section) {
    504     sections_.Add(section);
    505     return sections_.length() - 1;
    506   }
    507 
    508   void Write(Writer* w, uintptr_t code_start, uintptr_t code_size) {
    509     Writer::Slot<MachOHeader> header = WriteHeader(w);
    510     uintptr_t load_command_start = w->position();
    511     Writer::Slot<MachOSegmentCommand> cmd = WriteSegmentCommand(w,
    512                                                                 code_start,
    513                                                                 code_size);
    514     WriteSections(w, cmd, header, load_command_start);
    515   }
    516 
    517  private:
    518   struct MachOHeader {
    519     uint32_t magic;
    520     uint32_t cputype;
    521     uint32_t cpusubtype;
    522     uint32_t filetype;
    523     uint32_t ncmds;
    524     uint32_t sizeofcmds;
    525     uint32_t flags;
    526 #if defined(V8_TARGET_ARCH_X64)
    527     uint32_t reserved;
    528 #endif
    529   };
    530 
    531   struct MachOSegmentCommand {
    532     uint32_t cmd;
    533     uint32_t cmdsize;
    534     char segname[16];
    535 #if defined(V8_TARGET_ARCH_IA32)
    536     uint32_t vmaddr;
    537     uint32_t vmsize;
    538     uint32_t fileoff;
    539     uint32_t filesize;
    540 #else
    541     uint64_t vmaddr;
    542     uint64_t vmsize;
    543     uint64_t fileoff;
    544     uint64_t filesize;
    545 #endif
    546     uint32_t maxprot;
    547     uint32_t initprot;
    548     uint32_t nsects;
    549     uint32_t flags;
    550   };
    551 
    552   enum MachOLoadCommandCmd {
    553     LC_SEGMENT_32 = 0x00000001u,
    554     LC_SEGMENT_64 = 0x00000019u
    555   };
    556 
    557 
    558   Writer::Slot<MachOHeader> WriteHeader(Writer* w) {
    559     ASSERT(w->position() == 0);
    560     Writer::Slot<MachOHeader> header = w->CreateSlotHere<MachOHeader>();
    561 #if defined(V8_TARGET_ARCH_IA32)
    562     header->magic = 0xFEEDFACEu;
    563     header->cputype = 7;  // i386
    564     header->cpusubtype = 3;  // CPU_SUBTYPE_I386_ALL
    565 #elif defined(V8_TARGET_ARCH_X64)
    566     header->magic = 0xFEEDFACFu;
    567     header->cputype = 7 | 0x01000000;  // i386 | 64-bit ABI
    568     header->cpusubtype = 3;  // CPU_SUBTYPE_I386_ALL
    569     header->reserved = 0;
    570 #else
    571 #error Unsupported target architecture.
    572 #endif
    573     header->filetype = 0x1;  // MH_OBJECT
    574     header->ncmds = 1;
    575     header->sizeofcmds = 0;
    576     header->flags = 0;
    577     return header;
    578   }
    579 
    580 
    581   Writer::Slot<MachOSegmentCommand> WriteSegmentCommand(Writer* w,
    582                                                         uintptr_t code_start,
    583                                                         uintptr_t code_size) {
    584     Writer::Slot<MachOSegmentCommand> cmd =
    585         w->CreateSlotHere<MachOSegmentCommand>();
    586 #if defined(V8_TARGET_ARCH_IA32)
    587     cmd->cmd = LC_SEGMENT_32;
    588 #else
    589     cmd->cmd = LC_SEGMENT_64;
    590 #endif
    591     cmd->vmaddr = code_start;
    592     cmd->vmsize = code_size;
    593     cmd->fileoff = 0;
    594     cmd->filesize = 0;
    595     cmd->maxprot = 7;
    596     cmd->initprot = 7;
    597     cmd->flags = 0;
    598     cmd->nsects = sections_.length();
    599     memset(cmd->segname, 0, 16);
    600     cmd->cmdsize = sizeof(MachOSegmentCommand) + sizeof(MachOSection::Header) *
    601         cmd->nsects;
    602     return cmd;
    603   }
    604 
    605 
    606   void WriteSections(Writer* w,
    607                      Writer::Slot<MachOSegmentCommand> cmd,
    608                      Writer::Slot<MachOHeader> header,
    609                      uintptr_t load_command_start) {
    610     Writer::Slot<MachOSection::Header> headers =
    611         w->CreateSlotsHere<MachOSection::Header>(sections_.length());
    612     cmd->fileoff = w->position();
    613     header->sizeofcmds = w->position() - load_command_start;
    614     for (int section = 0; section < sections_.length(); ++section) {
    615       sections_[section]->PopulateHeader(headers.at(section));
    616       sections_[section]->WriteBody(headers.at(section), w);
    617     }
    618     cmd->filesize = w->position() - (uintptr_t)cmd->fileoff;
    619   }
    620 
    621 
    622   ZoneList<MachOSection*> sections_;
    623 };
    624 #endif  // defined(__MACH_O)
    625 
    626 
    627 #if defined(__ELF)
    628 class ELF BASE_EMBEDDED {
    629  public:
    630   ELF() : sections_(6) {
    631     sections_.Add(new ELFSection("", ELFSection::TYPE_NULL, 0));
    632     sections_.Add(new StringTable(".shstrtab"));
    633   }
    634 
    635   void Write(Writer* w) {
    636     WriteHeader(w);
    637     WriteSectionTable(w);
    638     WriteSections(w);
    639   }
    640 
    641   ELFSection* SectionAt(uint32_t index) {
    642     return sections_[index];
    643   }
    644 
    645   uint32_t AddSection(ELFSection* section) {
    646     sections_.Add(section);
    647     section->set_index(sections_.length() - 1);
    648     return sections_.length() - 1;
    649   }
    650 
    651  private:
    652   struct ELFHeader {
    653     uint8_t ident[16];
    654     uint16_t type;
    655     uint16_t machine;
    656     uint32_t version;
    657     uintptr_t entry;
    658     uintptr_t pht_offset;
    659     uintptr_t sht_offset;
    660     uint32_t flags;
    661     uint16_t header_size;
    662     uint16_t pht_entry_size;
    663     uint16_t pht_entry_num;
    664     uint16_t sht_entry_size;
    665     uint16_t sht_entry_num;
    666     uint16_t sht_strtab_index;
    667   };
    668 
    669 
    670   void WriteHeader(Writer* w) {
    671     ASSERT(w->position() == 0);
    672     Writer::Slot<ELFHeader> header = w->CreateSlotHere<ELFHeader>();
    673 #if defined(V8_TARGET_ARCH_IA32) || defined(V8_TARGET_ARCH_ARM)
    674     const uint8_t ident[16] =
    675         { 0x7f, 'E', 'L', 'F', 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0};
    676 #elif defined(V8_TARGET_ARCH_X64)
    677     const uint8_t ident[16] =
    678         { 0x7f, 'E', 'L', 'F', 2, 1, 1, 0, 0, 0 , 0, 0, 0, 0, 0, 0};
    679 #else
    680 #error Unsupported target architecture.
    681 #endif
    682     memcpy(header->ident, ident, 16);
    683     header->type = 1;
    684 #if defined(V8_TARGET_ARCH_IA32)
    685     header->machine = 3;
    686 #elif defined(V8_TARGET_ARCH_X64)
    687     // Processor identification value for x64 is 62 as defined in
    688     //    System V ABI, AMD64 Supplement
    689     //    http://www.x86-64.org/documentation/abi.pdf
    690     header->machine = 62;
    691 #elif defined(V8_TARGET_ARCH_ARM)
    692     // Set to EM_ARM, defined as 40, in "ARM ELF File Format" at
    693     // infocenter.arm.com/help/topic/com.arm.doc.dui0101a/DUI0101A_Elf.pdf
    694     header->machine = 40;
    695 #else
    696 #error Unsupported target architecture.
    697 #endif
    698     header->version = 1;
    699     header->entry = 0;
    700     header->pht_offset = 0;
    701     header->sht_offset = sizeof(ELFHeader);  // Section table follows header.
    702     header->flags = 0;
    703     header->header_size = sizeof(ELFHeader);
    704     header->pht_entry_size = 0;
    705     header->pht_entry_num = 0;
    706     header->sht_entry_size = sizeof(ELFSection::Header);
    707     header->sht_entry_num = sections_.length();
    708     header->sht_strtab_index = 1;
    709   }
    710 
    711   void WriteSectionTable(Writer* w) {
    712     // Section headers table immediately follows file header.
    713     ASSERT(w->position() == sizeof(ELFHeader));
    714 
    715     Writer::Slot<ELFSection::Header> headers =
    716         w->CreateSlotsHere<ELFSection::Header>(sections_.length());
    717 
    718     // String table for section table is the first section.
    719     StringTable* strtab = static_cast<StringTable*>(SectionAt(1));
    720     strtab->AttachWriter(w);
    721     for (int i = 0, length = sections_.length();
    722          i < length;
    723          i++) {
    724       sections_[i]->PopulateHeader(headers.at(i), strtab);
    725     }
    726     strtab->DetachWriter();
    727   }
    728 
    729   int SectionHeaderPosition(uint32_t section_index) {
    730     return sizeof(ELFHeader) + sizeof(ELFSection::Header) * section_index;
    731   }
    732 
    733   void WriteSections(Writer* w) {
    734     Writer::Slot<ELFSection::Header> headers =
    735         w->SlotAt<ELFSection::Header>(sizeof(ELFHeader));
    736 
    737     for (int i = 0, length = sections_.length();
    738          i < length;
    739          i++) {
    740       sections_[i]->WriteBody(headers.at(i), w);
    741     }
    742   }
    743 
    744   ZoneList<ELFSection*> sections_;
    745 };
    746 
    747 
    748 class ELFSymbol BASE_EMBEDDED {
    749  public:
    750   enum Type {
    751     TYPE_NOTYPE = 0,
    752     TYPE_OBJECT = 1,
    753     TYPE_FUNC = 2,
    754     TYPE_SECTION = 3,
    755     TYPE_FILE = 4,
    756     TYPE_LOPROC = 13,
    757     TYPE_HIPROC = 15
    758   };
    759 
    760   enum Binding {
    761     BIND_LOCAL = 0,
    762     BIND_GLOBAL = 1,
    763     BIND_WEAK = 2,
    764     BIND_LOPROC = 13,
    765     BIND_HIPROC = 15
    766   };
    767 
    768   ELFSymbol(const char* name,
    769             uintptr_t value,
    770             uintptr_t size,
    771             Binding binding,
    772             Type type,
    773             uint16_t section)
    774       : name(name),
    775         value(value),
    776         size(size),
    777         info((binding << 4) | type),
    778         other(0),
    779         section(section) {
    780   }
    781 
    782   Binding binding() const {
    783     return static_cast<Binding>(info >> 4);
    784   }
    785 #if defined(V8_TARGET_ARCH_IA32) || defined(V8_TARGET_ARCH_ARM)
    786   struct SerializedLayout {
    787     SerializedLayout(uint32_t name,
    788                      uintptr_t value,
    789                      uintptr_t size,
    790                      Binding binding,
    791                      Type type,
    792                      uint16_t section)
    793         : name(name),
    794           value(value),
    795           size(size),
    796           info((binding << 4) | type),
    797           other(0),
    798           section(section) {
    799     }
    800 
    801     uint32_t name;
    802     uintptr_t value;
    803     uintptr_t size;
    804     uint8_t info;
    805     uint8_t other;
    806     uint16_t section;
    807   };
    808 #elif defined(V8_TARGET_ARCH_X64)
    809   struct SerializedLayout {
    810     SerializedLayout(uint32_t name,
    811                      uintptr_t value,
    812                      uintptr_t size,
    813                      Binding binding,
    814                      Type type,
    815                      uint16_t section)
    816         : name(name),
    817           info((binding << 4) | type),
    818           other(0),
    819           section(section),
    820           value(value),
    821           size(size) {
    822     }
    823 
    824     uint32_t name;
    825     uint8_t info;
    826     uint8_t other;
    827     uint16_t section;
    828     uintptr_t value;
    829     uintptr_t size;
    830   };
    831 #endif
    832 
    833   void Write(Writer::Slot<SerializedLayout> s, StringTable* t) {
    834     // Convert symbol names from strings to indexes in the string table.
    835     s->name = t->Add(name);
    836     s->value = value;
    837     s->size = size;
    838     s->info = info;
    839     s->other = other;
    840     s->section = section;
    841   }
    842 
    843  private:
    844   const char* name;
    845   uintptr_t value;
    846   uintptr_t size;
    847   uint8_t info;
    848   uint8_t other;
    849   uint16_t section;
    850 };
    851 
    852 
    853 class ELFSymbolTable : public ELFSection {
    854  public:
    855   explicit ELFSymbolTable(const char* name)
    856       : ELFSection(name, TYPE_SYMTAB, sizeof(uintptr_t)),
    857         locals_(1),
    858         globals_(1) {
    859   }
    860 
    861   virtual void WriteBody(Writer::Slot<Header> header, Writer* w) {
    862     w->Align(header->alignment);
    863     int total_symbols = locals_.length() + globals_.length() + 1;
    864     header->offset = w->position();
    865 
    866     Writer::Slot<ELFSymbol::SerializedLayout> symbols =
    867         w->CreateSlotsHere<ELFSymbol::SerializedLayout>(total_symbols);
    868 
    869     header->size = w->position() - header->offset;
    870 
    871     // String table for this symbol table should follow it in the section table.
    872     StringTable* strtab =
    873         static_cast<StringTable*>(w->debug_object()->SectionAt(index() + 1));
    874     strtab->AttachWriter(w);
    875     symbols.at(0).set(ELFSymbol::SerializedLayout(0,
    876                                                   0,
    877                                                   0,
    878                                                   ELFSymbol::BIND_LOCAL,
    879                                                   ELFSymbol::TYPE_NOTYPE,
    880                                                   0));
    881     WriteSymbolsList(&locals_, symbols.at(1), strtab);
    882     WriteSymbolsList(&globals_, symbols.at(locals_.length() + 1), strtab);
    883     strtab->DetachWriter();
    884   }
    885 
    886   void Add(const ELFSymbol& symbol) {
    887     if (symbol.binding() == ELFSymbol::BIND_LOCAL) {
    888       locals_.Add(symbol);
    889     } else {
    890       globals_.Add(symbol);
    891     }
    892   }
    893 
    894  protected:
    895   virtual void PopulateHeader(Writer::Slot<Header> header) {
    896     ELFSection::PopulateHeader(header);
    897     // We are assuming that string table will follow symbol table.
    898     header->link = index() + 1;
    899     header->info = locals_.length() + 1;
    900     header->entry_size = sizeof(ELFSymbol::SerializedLayout);
    901   }
    902 
    903  private:
    904   void WriteSymbolsList(const ZoneList<ELFSymbol>* src,
    905                         Writer::Slot<ELFSymbol::SerializedLayout> dst,
    906                         StringTable* strtab) {
    907     for (int i = 0, len = src->length();
    908          i < len;
    909          i++) {
    910       src->at(i).Write(dst.at(i), strtab);
    911     }
    912   }
    913 
    914   ZoneList<ELFSymbol> locals_;
    915   ZoneList<ELFSymbol> globals_;
    916 };
    917 #endif  // defined(__ELF)
    918 
    919 
    920 class CodeDescription BASE_EMBEDDED {
    921  public:
    922 #ifdef V8_TARGET_ARCH_X64
    923   enum StackState {
    924     POST_RBP_PUSH,
    925     POST_RBP_SET,
    926     POST_RBP_POP,
    927     STACK_STATE_MAX
    928   };
    929 #endif
    930 
    931   CodeDescription(const char* name,
    932                   Code* code,
    933                   Handle<Script> script,
    934                   GDBJITLineInfo* lineinfo,
    935                   GDBJITInterface::CodeTag tag,
    936                   CompilationInfo* info)
    937       : name_(name),
    938         code_(code),
    939         script_(script),
    940         lineinfo_(lineinfo),
    941         tag_(tag),
    942         info_(info) {
    943   }
    944 
    945   const char* name() const {
    946     return name_;
    947   }
    948 
    949   GDBJITLineInfo* lineinfo() const {
    950     return lineinfo_;
    951   }
    952 
    953   GDBJITInterface::CodeTag tag() const {
    954     return tag_;
    955   }
    956 
    957   CompilationInfo* info() const {
    958     return info_;
    959   }
    960 
    961   bool IsInfoAvailable() const {
    962     return info_ != NULL;
    963   }
    964 
    965   uintptr_t CodeStart() const {
    966     return reinterpret_cast<uintptr_t>(code_->instruction_start());
    967   }
    968 
    969   uintptr_t CodeEnd() const {
    970     return reinterpret_cast<uintptr_t>(code_->instruction_end());
    971   }
    972 
    973   uintptr_t CodeSize() const {
    974     return CodeEnd() - CodeStart();
    975   }
    976 
    977   bool IsLineInfoAvailable() {
    978     return !script_.is_null() &&
    979         script_->source()->IsString() &&
    980         script_->HasValidSource() &&
    981         script_->name()->IsString() &&
    982         lineinfo_ != NULL;
    983   }
    984 
    985 #ifdef V8_TARGET_ARCH_X64
    986   uintptr_t GetStackStateStartAddress(StackState state) const {
    987     ASSERT(state < STACK_STATE_MAX);
    988     return stack_state_start_addresses_[state];
    989   }
    990 
    991   void SetStackStateStartAddress(StackState state, uintptr_t addr) {
    992     ASSERT(state < STACK_STATE_MAX);
    993     stack_state_start_addresses_[state] = addr;
    994   }
    995 #endif
    996 
    997   SmartArrayPointer<char> GetFilename() {
    998     return String::cast(script_->name())->ToCString();
    999   }
   1000 
   1001   int GetScriptLineNumber(int pos) {
   1002     return GetScriptLineNumberSafe(script_, pos) + 1;
   1003   }
   1004 
   1005 
   1006  private:
   1007   const char* name_;
   1008   Code* code_;
   1009   Handle<Script> script_;
   1010   GDBJITLineInfo* lineinfo_;
   1011   GDBJITInterface::CodeTag tag_;
   1012   CompilationInfo* info_;
   1013 #ifdef V8_TARGET_ARCH_X64
   1014   uintptr_t stack_state_start_addresses_[STACK_STATE_MAX];
   1015 #endif
   1016 };
   1017 
   1018 #if defined(__ELF)
   1019 static void CreateSymbolsTable(CodeDescription* desc,
   1020                                ELF* elf,
   1021                                int text_section_index) {
   1022   ELFSymbolTable* symtab = new ELFSymbolTable(".symtab");
   1023   StringTable* strtab = new StringTable(".strtab");
   1024 
   1025   // Symbol table should be followed by the linked string table.
   1026   elf->AddSection(symtab);
   1027   elf->AddSection(strtab);
   1028 
   1029   symtab->Add(ELFSymbol("V8 Code",
   1030                         0,
   1031                         0,
   1032                         ELFSymbol::BIND_LOCAL,
   1033                         ELFSymbol::TYPE_FILE,
   1034                         ELFSection::INDEX_ABSOLUTE));
   1035 
   1036   symtab->Add(ELFSymbol(desc->name(),
   1037                         0,
   1038                         desc->CodeSize(),
   1039                         ELFSymbol::BIND_GLOBAL,
   1040                         ELFSymbol::TYPE_FUNC,
   1041                         text_section_index));
   1042 }
   1043 #endif  // defined(__ELF)
   1044 
   1045 
   1046 class DebugInfoSection : public DebugSection {
   1047  public:
   1048   explicit DebugInfoSection(CodeDescription* desc)
   1049 #if defined(__ELF)
   1050       : ELFSection(".debug_info", TYPE_PROGBITS, 1),
   1051 #else
   1052       : MachOSection("__debug_info",
   1053                      "__DWARF",
   1054                      1,
   1055                      MachOSection::S_REGULAR | MachOSection::S_ATTR_DEBUG),
   1056 #endif
   1057         desc_(desc) { }
   1058 
   1059   // DWARF2 standard
   1060   enum DWARF2LocationOp {
   1061     DW_OP_reg0 = 0x50,
   1062     DW_OP_reg1 = 0x51,
   1063     DW_OP_reg2 = 0x52,
   1064     DW_OP_reg3 = 0x53,
   1065     DW_OP_reg4 = 0x54,
   1066     DW_OP_reg5 = 0x55,
   1067     DW_OP_reg6 = 0x56,
   1068     DW_OP_reg7 = 0x57,
   1069     DW_OP_fbreg = 0x91  // 1 param: SLEB128 offset
   1070   };
   1071 
   1072   enum DWARF2Encoding {
   1073     DW_ATE_ADDRESS = 0x1,
   1074     DW_ATE_SIGNED = 0x5
   1075   };
   1076 
   1077   bool WriteBody(Writer* w) {
   1078     uintptr_t cu_start = w->position();
   1079     Writer::Slot<uint32_t> size = w->CreateSlotHere<uint32_t>();
   1080     uintptr_t start = w->position();
   1081     w->Write<uint16_t>(2);  // DWARF version.
   1082     w->Write<uint32_t>(0);  // Abbreviation table offset.
   1083     w->Write<uint8_t>(sizeof(intptr_t));
   1084 
   1085     w->WriteULEB128(1);  // Abbreviation code.
   1086     w->WriteString(*desc_->GetFilename());
   1087     w->Write<intptr_t>(desc_->CodeStart());
   1088     w->Write<intptr_t>(desc_->CodeStart() + desc_->CodeSize());
   1089     w->Write<uint32_t>(0);
   1090 
   1091     uint32_t ty_offset = static_cast<uint32_t>(w->position() - cu_start);
   1092     w->WriteULEB128(3);
   1093     w->Write<uint8_t>(kPointerSize);
   1094     w->WriteString("v8value");
   1095 
   1096     if (desc_->IsInfoAvailable()) {
   1097       CompilationInfo* info = desc_->info();
   1098       ScopeInfo<FreeStoreAllocationPolicy> scope_info(info->scope());
   1099       w->WriteULEB128(2);
   1100       w->WriteString(desc_->name());
   1101       w->Write<intptr_t>(desc_->CodeStart());
   1102       w->Write<intptr_t>(desc_->CodeStart() + desc_->CodeSize());
   1103       Writer::Slot<uint32_t> fb_block_size = w->CreateSlotHere<uint32_t>();
   1104       uintptr_t fb_block_start = w->position();
   1105 #if defined(V8_TARGET_ARCH_IA32)
   1106       w->Write<uint8_t>(DW_OP_reg5);  // The frame pointer's here on ia32
   1107 #elif defined(V8_TARGET_ARCH_X64)
   1108       w->Write<uint8_t>(DW_OP_reg6);  // and here on x64.
   1109 #else
   1110 #error Unsupported target architecture.
   1111 #endif
   1112       fb_block_size.set(static_cast<uint32_t>(w->position() - fb_block_start));
   1113 
   1114       int params = scope_info.number_of_parameters();
   1115       int slots = scope_info.number_of_stack_slots();
   1116       int context_slots = scope_info.number_of_context_slots();
   1117       // The real slot ID is internal_slots + context_slot_id.
   1118       int internal_slots = Context::MIN_CONTEXT_SLOTS;
   1119       int locals = scope_info.LocalCount();
   1120       int current_abbreviation = 4;
   1121 
   1122       for (int param = 0; param < params; ++param) {
   1123         w->WriteULEB128(current_abbreviation++);
   1124         w->WriteString(
   1125             *scope_info.ParameterName(param)->ToCString(DISALLOW_NULLS));
   1126         w->Write<uint32_t>(ty_offset);
   1127         Writer::Slot<uint32_t> block_size = w->CreateSlotHere<uint32_t>();
   1128         uintptr_t block_start = w->position();
   1129         w->Write<uint8_t>(DW_OP_fbreg);
   1130         w->WriteSLEB128(
   1131           JavaScriptFrameConstants::kLastParameterOffset +
   1132               kPointerSize * (params - param - 1));
   1133         block_size.set(static_cast<uint32_t>(w->position() - block_start));
   1134       }
   1135 
   1136       EmbeddedVector<char, 256> buffer;
   1137       StringBuilder builder(buffer.start(), buffer.length());
   1138 
   1139       for (int slot = 0; slot < slots; ++slot) {
   1140         w->WriteULEB128(current_abbreviation++);
   1141         builder.Reset();
   1142         builder.AddFormatted("slot%d", slot);
   1143         w->WriteString(builder.Finalize());
   1144       }
   1145 
   1146       // See contexts.h for more information.
   1147       ASSERT(Context::MIN_CONTEXT_SLOTS == 4);
   1148       ASSERT(Context::CLOSURE_INDEX == 0);
   1149       ASSERT(Context::PREVIOUS_INDEX == 1);
   1150       ASSERT(Context::EXTENSION_INDEX == 2);
   1151       ASSERT(Context::GLOBAL_INDEX == 3);
   1152       w->WriteULEB128(current_abbreviation++);
   1153       w->WriteString(".closure");
   1154       w->WriteULEB128(current_abbreviation++);
   1155       w->WriteString(".previous");
   1156       w->WriteULEB128(current_abbreviation++);
   1157       w->WriteString(".extension");
   1158       w->WriteULEB128(current_abbreviation++);
   1159       w->WriteString(".global");
   1160 
   1161       for (int context_slot = 0;
   1162            context_slot < context_slots;
   1163            ++context_slot) {
   1164         w->WriteULEB128(current_abbreviation++);
   1165         builder.Reset();
   1166         builder.AddFormatted("context_slot%d", context_slot + internal_slots);
   1167         w->WriteString(builder.Finalize());
   1168       }
   1169 
   1170       for (int local = 0; local < locals; ++local) {
   1171         w->WriteULEB128(current_abbreviation++);
   1172         w->WriteString(
   1173             *scope_info.LocalName(local)->ToCString(DISALLOW_NULLS));
   1174         w->Write<uint32_t>(ty_offset);
   1175         Writer::Slot<uint32_t> block_size = w->CreateSlotHere<uint32_t>();
   1176         uintptr_t block_start = w->position();
   1177         w->Write<uint8_t>(DW_OP_fbreg);
   1178         w->WriteSLEB128(
   1179           JavaScriptFrameConstants::kLocal0Offset -
   1180               kPointerSize * local);
   1181         block_size.set(static_cast<uint32_t>(w->position() - block_start));
   1182       }
   1183 
   1184       {
   1185         w->WriteULEB128(current_abbreviation++);
   1186         w->WriteString("__function");
   1187         w->Write<uint32_t>(ty_offset);
   1188         Writer::Slot<uint32_t> block_size = w->CreateSlotHere<uint32_t>();
   1189         uintptr_t block_start = w->position();
   1190         w->Write<uint8_t>(DW_OP_fbreg);
   1191         w->WriteSLEB128(JavaScriptFrameConstants::kFunctionOffset);
   1192         block_size.set(static_cast<uint32_t>(w->position() - block_start));
   1193       }
   1194 
   1195       {
   1196         w->WriteULEB128(current_abbreviation++);
   1197         w->WriteString("__context");
   1198         w->Write<uint32_t>(ty_offset);
   1199         Writer::Slot<uint32_t> block_size = w->CreateSlotHere<uint32_t>();
   1200         uintptr_t block_start = w->position();
   1201         w->Write<uint8_t>(DW_OP_fbreg);
   1202         w->WriteSLEB128(StandardFrameConstants::kContextOffset);
   1203         block_size.set(static_cast<uint32_t>(w->position() - block_start));
   1204       }
   1205     }
   1206 
   1207     size.set(static_cast<uint32_t>(w->position() - start));
   1208     return true;
   1209   }
   1210 
   1211  private:
   1212   CodeDescription* desc_;
   1213 };
   1214 
   1215 
   1216 class DebugAbbrevSection : public DebugSection {
   1217  public:
   1218   explicit DebugAbbrevSection(CodeDescription* desc)
   1219 #ifdef __ELF
   1220       : ELFSection(".debug_abbrev", TYPE_PROGBITS, 1),
   1221 #else
   1222       : MachOSection("__debug_abbrev",
   1223                      "__DWARF",
   1224                      1,
   1225                      MachOSection::S_REGULAR | MachOSection::S_ATTR_DEBUG),
   1226 #endif
   1227         desc_(desc) { }
   1228 
   1229   // DWARF2 standard, figure 14.
   1230   enum DWARF2Tags {
   1231     DW_TAG_FORMAL_PARAMETER = 0x05,
   1232     DW_TAG_POINTER_TYPE = 0xf,
   1233     DW_TAG_COMPILE_UNIT = 0x11,
   1234     DW_TAG_STRUCTURE_TYPE = 0x13,
   1235     DW_TAG_BASE_TYPE = 0x24,
   1236     DW_TAG_SUBPROGRAM = 0x2e,
   1237     DW_TAG_VARIABLE = 0x34
   1238   };
   1239 
   1240   // DWARF2 standard, figure 16.
   1241   enum DWARF2ChildrenDetermination {
   1242     DW_CHILDREN_NO = 0,
   1243     DW_CHILDREN_YES = 1
   1244   };
   1245 
   1246   // DWARF standard, figure 17.
   1247   enum DWARF2Attribute {
   1248     DW_AT_LOCATION = 0x2,
   1249     DW_AT_NAME = 0x3,
   1250     DW_AT_BYTE_SIZE = 0xb,
   1251     DW_AT_STMT_LIST = 0x10,
   1252     DW_AT_LOW_PC = 0x11,
   1253     DW_AT_HIGH_PC = 0x12,
   1254     DW_AT_ENCODING = 0x3e,
   1255     DW_AT_FRAME_BASE = 0x40,
   1256     DW_AT_TYPE = 0x49
   1257   };
   1258 
   1259   // DWARF2 standard, figure 19.
   1260   enum DWARF2AttributeForm {
   1261     DW_FORM_ADDR = 0x1,
   1262     DW_FORM_BLOCK4 = 0x4,
   1263     DW_FORM_STRING = 0x8,
   1264     DW_FORM_DATA4 = 0x6,
   1265     DW_FORM_BLOCK = 0x9,
   1266     DW_FORM_DATA1 = 0xb,
   1267     DW_FORM_FLAG = 0xc,
   1268     DW_FORM_REF4 = 0x13
   1269   };
   1270 
   1271   void WriteVariableAbbreviation(Writer* w,
   1272                                  int abbreviation_code,
   1273                                  bool has_value,
   1274                                  bool is_parameter) {
   1275     w->WriteULEB128(abbreviation_code);
   1276     w->WriteULEB128(is_parameter ? DW_TAG_FORMAL_PARAMETER : DW_TAG_VARIABLE);
   1277     w->Write<uint8_t>(DW_CHILDREN_NO);
   1278     w->WriteULEB128(DW_AT_NAME);
   1279     w->WriteULEB128(DW_FORM_STRING);
   1280     if (has_value) {
   1281       w->WriteULEB128(DW_AT_TYPE);
   1282       w->WriteULEB128(DW_FORM_REF4);
   1283       w->WriteULEB128(DW_AT_LOCATION);
   1284       w->WriteULEB128(DW_FORM_BLOCK4);
   1285     }
   1286     w->WriteULEB128(0);
   1287     w->WriteULEB128(0);
   1288   }
   1289 
   1290   bool WriteBody(Writer* w) {
   1291     int current_abbreviation = 1;
   1292     bool extra_info = desc_->IsInfoAvailable();
   1293     ASSERT(desc_->IsLineInfoAvailable());
   1294     w->WriteULEB128(current_abbreviation++);
   1295     w->WriteULEB128(DW_TAG_COMPILE_UNIT);
   1296     w->Write<uint8_t>(extra_info ? DW_CHILDREN_YES : DW_CHILDREN_NO);
   1297     w->WriteULEB128(DW_AT_NAME);
   1298     w->WriteULEB128(DW_FORM_STRING);
   1299     w->WriteULEB128(DW_AT_LOW_PC);
   1300     w->WriteULEB128(DW_FORM_ADDR);
   1301     w->WriteULEB128(DW_AT_HIGH_PC);
   1302     w->WriteULEB128(DW_FORM_ADDR);
   1303     w->WriteULEB128(DW_AT_STMT_LIST);
   1304     w->WriteULEB128(DW_FORM_DATA4);
   1305     w->WriteULEB128(0);
   1306     w->WriteULEB128(0);
   1307 
   1308     if (extra_info) {
   1309       CompilationInfo* info = desc_->info();
   1310       ScopeInfo<FreeStoreAllocationPolicy> scope_info(info->scope());
   1311       int params = scope_info.number_of_parameters();
   1312       int slots = scope_info.number_of_stack_slots();
   1313       int context_slots = scope_info.number_of_context_slots();
   1314       // The real slot ID is internal_slots + context_slot_id.
   1315       int internal_slots = Context::MIN_CONTEXT_SLOTS;
   1316       int locals = scope_info.LocalCount();
   1317       int total_children =
   1318           params + slots + context_slots + internal_slots + locals + 2;
   1319 
   1320       // The extra duplication below seems to be necessary to keep
   1321       // gdb from getting upset on OSX.
   1322       w->WriteULEB128(current_abbreviation++);  // Abbreviation code.
   1323       w->WriteULEB128(DW_TAG_SUBPROGRAM);
   1324       w->Write<uint8_t>(
   1325           total_children != 0 ? DW_CHILDREN_YES : DW_CHILDREN_NO);
   1326       w->WriteULEB128(DW_AT_NAME);
   1327       w->WriteULEB128(DW_FORM_STRING);
   1328       w->WriteULEB128(DW_AT_LOW_PC);
   1329       w->WriteULEB128(DW_FORM_ADDR);
   1330       w->WriteULEB128(DW_AT_HIGH_PC);
   1331       w->WriteULEB128(DW_FORM_ADDR);
   1332       w->WriteULEB128(DW_AT_FRAME_BASE);
   1333       w->WriteULEB128(DW_FORM_BLOCK4);
   1334       w->WriteULEB128(0);
   1335       w->WriteULEB128(0);
   1336 
   1337       w->WriteULEB128(current_abbreviation++);
   1338       w->WriteULEB128(DW_TAG_STRUCTURE_TYPE);
   1339       w->Write<uint8_t>(DW_CHILDREN_NO);
   1340       w->WriteULEB128(DW_AT_BYTE_SIZE);
   1341       w->WriteULEB128(DW_FORM_DATA1);
   1342       w->WriteULEB128(DW_AT_NAME);
   1343       w->WriteULEB128(DW_FORM_STRING);
   1344       w->WriteULEB128(0);
   1345       w->WriteULEB128(0);
   1346 
   1347       for (int param = 0; param < params; ++param) {
   1348         WriteVariableAbbreviation(w, current_abbreviation++, true, true);
   1349       }
   1350 
   1351       for (int slot = 0; slot < slots; ++slot) {
   1352         WriteVariableAbbreviation(w, current_abbreviation++, false, false);
   1353       }
   1354 
   1355       for (int internal_slot = 0;
   1356            internal_slot < internal_slots;
   1357            ++internal_slot) {
   1358         WriteVariableAbbreviation(w, current_abbreviation++, false, false);
   1359       }
   1360 
   1361       for (int context_slot = 0;
   1362            context_slot < context_slots;
   1363            ++context_slot) {
   1364         WriteVariableAbbreviation(w, current_abbreviation++, false, false);
   1365       }
   1366 
   1367       for (int local = 0; local < locals; ++local) {
   1368         WriteVariableAbbreviation(w, current_abbreviation++, true, false);
   1369       }
   1370 
   1371       // The function.
   1372       WriteVariableAbbreviation(w, current_abbreviation++, true, false);
   1373 
   1374       // The context.
   1375       WriteVariableAbbreviation(w, current_abbreviation++, true, false);
   1376 
   1377       if (total_children != 0) {
   1378         w->WriteULEB128(0);  // Terminate the sibling list.
   1379       }
   1380     }
   1381 
   1382     w->WriteULEB128(0);  // Terminate the table.
   1383     return true;
   1384   }
   1385 
   1386  private:
   1387   CodeDescription* desc_;
   1388 };
   1389 
   1390 
   1391 class DebugLineSection : public DebugSection {
   1392  public:
   1393   explicit DebugLineSection(CodeDescription* desc)
   1394 #ifdef __ELF
   1395       : ELFSection(".debug_line", TYPE_PROGBITS, 1),
   1396 #else
   1397       : MachOSection("__debug_line",
   1398                      "__DWARF",
   1399                      1,
   1400                      MachOSection::S_REGULAR | MachOSection::S_ATTR_DEBUG),
   1401 #endif
   1402         desc_(desc) { }
   1403 
   1404   // DWARF2 standard, figure 34.
   1405   enum DWARF2Opcodes {
   1406     DW_LNS_COPY = 1,
   1407     DW_LNS_ADVANCE_PC = 2,
   1408     DW_LNS_ADVANCE_LINE = 3,
   1409     DW_LNS_SET_FILE = 4,
   1410     DW_LNS_SET_COLUMN = 5,
   1411     DW_LNS_NEGATE_STMT = 6
   1412   };
   1413 
   1414   // DWARF2 standard, figure 35.
   1415   enum DWARF2ExtendedOpcode {
   1416     DW_LNE_END_SEQUENCE = 1,
   1417     DW_LNE_SET_ADDRESS = 2,
   1418     DW_LNE_DEFINE_FILE = 3
   1419   };
   1420 
   1421   bool WriteBody(Writer* w) {
   1422     // Write prologue.
   1423     Writer::Slot<uint32_t> total_length = w->CreateSlotHere<uint32_t>();
   1424     uintptr_t start = w->position();
   1425 
   1426     // Used for special opcodes
   1427     const int8_t line_base = 1;
   1428     const uint8_t line_range = 7;
   1429     const int8_t max_line_incr = (line_base + line_range - 1);
   1430     const uint8_t opcode_base = DW_LNS_NEGATE_STMT + 1;
   1431 
   1432     w->Write<uint16_t>(2);  // Field version.
   1433     Writer::Slot<uint32_t> prologue_length = w->CreateSlotHere<uint32_t>();
   1434     uintptr_t prologue_start = w->position();
   1435     w->Write<uint8_t>(1);  // Field minimum_instruction_length.
   1436     w->Write<uint8_t>(1);  // Field default_is_stmt.
   1437     w->Write<int8_t>(line_base);  // Field line_base.
   1438     w->Write<uint8_t>(line_range);  // Field line_range.
   1439     w->Write<uint8_t>(opcode_base);  // Field opcode_base.
   1440     w->Write<uint8_t>(0);  // DW_LNS_COPY operands count.
   1441     w->Write<uint8_t>(1);  // DW_LNS_ADVANCE_PC operands count.
   1442     w->Write<uint8_t>(1);  // DW_LNS_ADVANCE_LINE operands count.
   1443     w->Write<uint8_t>(1);  // DW_LNS_SET_FILE operands count.
   1444     w->Write<uint8_t>(1);  // DW_LNS_SET_COLUMN operands count.
   1445     w->Write<uint8_t>(0);  // DW_LNS_NEGATE_STMT operands count.
   1446     w->Write<uint8_t>(0);  // Empty include_directories sequence.
   1447     w->WriteString(*desc_->GetFilename());  // File name.
   1448     w->WriteULEB128(0);  // Current directory.
   1449     w->WriteULEB128(0);  // Unknown modification time.
   1450     w->WriteULEB128(0);  // Unknown file size.
   1451     w->Write<uint8_t>(0);
   1452     prologue_length.set(static_cast<uint32_t>(w->position() - prologue_start));
   1453 
   1454     WriteExtendedOpcode(w, DW_LNE_SET_ADDRESS, sizeof(intptr_t));
   1455     w->Write<intptr_t>(desc_->CodeStart());
   1456     w->Write<uint8_t>(DW_LNS_COPY);
   1457 
   1458     intptr_t pc = 0;
   1459     intptr_t line = 1;
   1460     bool is_statement = true;
   1461 
   1462     List<GDBJITLineInfo::PCInfo>* pc_info = desc_->lineinfo()->pc_info();
   1463     pc_info->Sort(&ComparePCInfo);
   1464 
   1465     int pc_info_length = pc_info->length();
   1466     for (int i = 0; i < pc_info_length; i++) {
   1467       GDBJITLineInfo::PCInfo* info = &pc_info->at(i);
   1468       ASSERT(info->pc_ >= pc);
   1469 
   1470       // Reduce bloating in the debug line table by removing duplicate line
   1471       // entries (per DWARF2 standard).
   1472       intptr_t  new_line = desc_->GetScriptLineNumber(info->pos_);
   1473       if (new_line == line) {
   1474         continue;
   1475       }
   1476 
   1477       // Mark statement boundaries.  For a better debugging experience, mark
   1478       // the last pc address in the function as a statement (e.g. "}"), so that
   1479       // a user can see the result of the last line executed in the function,
   1480       // should control reach the end.
   1481       if ((i+1) == pc_info_length) {
   1482         if (!is_statement) {
   1483           w->Write<uint8_t>(DW_LNS_NEGATE_STMT);
   1484         }
   1485       } else if (is_statement != info->is_statement_) {
   1486         w->Write<uint8_t>(DW_LNS_NEGATE_STMT);
   1487         is_statement = !is_statement;
   1488       }
   1489 
   1490       // Generate special opcodes, if possible.  This results in more compact
   1491       // debug line tables.  See the DWARF 2.0 standard to learn more about
   1492       // special opcodes.
   1493       uintptr_t pc_diff = info->pc_ - pc;
   1494       intptr_t line_diff = new_line - line;
   1495 
   1496       // Compute special opcode (see DWARF 2.0 standard)
   1497       intptr_t special_opcode = (line_diff - line_base) +
   1498                                 (line_range * pc_diff) + opcode_base;
   1499 
   1500       // If special_opcode is less than or equal to 255, it can be used as a
   1501       // special opcode.  If line_diff is larger than the max line increment
   1502       // allowed for a special opcode, or if line_diff is less than the minimum
   1503       // line that can be added to the line register (i.e. line_base), then
   1504       // special_opcode can't be used.
   1505       if ((special_opcode >= opcode_base) && (special_opcode <= 255) &&
   1506           (line_diff <= max_line_incr) && (line_diff >= line_base)) {
   1507         w->Write<uint8_t>(special_opcode);
   1508       } else {
   1509         w->Write<uint8_t>(DW_LNS_ADVANCE_PC);
   1510         w->WriteSLEB128(pc_diff);
   1511         w->Write<uint8_t>(DW_LNS_ADVANCE_LINE);
   1512         w->WriteSLEB128(line_diff);
   1513         w->Write<uint8_t>(DW_LNS_COPY);
   1514       }
   1515 
   1516       // Increment the pc and line operands.
   1517       pc += pc_diff;
   1518       line += line_diff;
   1519     }
   1520     // Advance the pc to the end of the routine, since the end sequence opcode
   1521     // requires this.
   1522     w->Write<uint8_t>(DW_LNS_ADVANCE_PC);
   1523     w->WriteSLEB128(desc_->CodeSize() - pc);
   1524     WriteExtendedOpcode(w, DW_LNE_END_SEQUENCE, 0);
   1525     total_length.set(static_cast<uint32_t>(w->position() - start));
   1526     return true;
   1527   }
   1528 
   1529  private:
   1530   void WriteExtendedOpcode(Writer* w,
   1531                            DWARF2ExtendedOpcode op,
   1532                            size_t operands_size) {
   1533     w->Write<uint8_t>(0);
   1534     w->WriteULEB128(operands_size + 1);
   1535     w->Write<uint8_t>(op);
   1536   }
   1537 
   1538   static int ComparePCInfo(const GDBJITLineInfo::PCInfo* a,
   1539                            const GDBJITLineInfo::PCInfo* b) {
   1540     if (a->pc_ == b->pc_) {
   1541       if (a->is_statement_ != b->is_statement_) {
   1542         return b->is_statement_ ? +1 : -1;
   1543       }
   1544       return 0;
   1545     } else if (a->pc_ > b->pc_) {
   1546       return +1;
   1547     } else {
   1548       return -1;
   1549     }
   1550   }
   1551 
   1552   CodeDescription* desc_;
   1553 };
   1554 
   1555 
   1556 #ifdef V8_TARGET_ARCH_X64
   1557 
   1558 class UnwindInfoSection : public DebugSection {
   1559  public:
   1560   explicit UnwindInfoSection(CodeDescription* desc);
   1561   virtual bool WriteBody(Writer* w);
   1562 
   1563   int WriteCIE(Writer* w);
   1564   void WriteFDE(Writer* w, int);
   1565 
   1566   void WriteFDEStateOnEntry(Writer* w);
   1567   void WriteFDEStateAfterRBPPush(Writer* w);
   1568   void WriteFDEStateAfterRBPSet(Writer* w);
   1569   void WriteFDEStateAfterRBPPop(Writer* w);
   1570 
   1571   void WriteLength(Writer* w,
   1572                    Writer::Slot<uint32_t>* length_slot,
   1573                    int initial_position);
   1574 
   1575  private:
   1576   CodeDescription* desc_;
   1577 
   1578   // DWARF3 Specification, Table 7.23
   1579   enum CFIInstructions {
   1580     DW_CFA_ADVANCE_LOC = 0x40,
   1581     DW_CFA_OFFSET = 0x80,
   1582     DW_CFA_RESTORE = 0xC0,
   1583     DW_CFA_NOP = 0x00,
   1584     DW_CFA_SET_LOC = 0x01,
   1585     DW_CFA_ADVANCE_LOC1 = 0x02,
   1586     DW_CFA_ADVANCE_LOC2 = 0x03,
   1587     DW_CFA_ADVANCE_LOC4 = 0x04,
   1588     DW_CFA_OFFSET_EXTENDED = 0x05,
   1589     DW_CFA_RESTORE_EXTENDED = 0x06,
   1590     DW_CFA_UNDEFINED = 0x07,
   1591     DW_CFA_SAME_VALUE = 0x08,
   1592     DW_CFA_REGISTER = 0x09,
   1593     DW_CFA_REMEMBER_STATE = 0x0A,
   1594     DW_CFA_RESTORE_STATE = 0x0B,
   1595     DW_CFA_DEF_CFA = 0x0C,
   1596     DW_CFA_DEF_CFA_REGISTER = 0x0D,
   1597     DW_CFA_DEF_CFA_OFFSET = 0x0E,
   1598 
   1599     DW_CFA_DEF_CFA_EXPRESSION = 0x0F,
   1600     DW_CFA_EXPRESSION = 0x10,
   1601     DW_CFA_OFFSET_EXTENDED_SF = 0x11,
   1602     DW_CFA_DEF_CFA_SF = 0x12,
   1603     DW_CFA_DEF_CFA_OFFSET_SF = 0x13,
   1604     DW_CFA_VAL_OFFSET = 0x14,
   1605     DW_CFA_VAL_OFFSET_SF = 0x15,
   1606     DW_CFA_VAL_EXPRESSION = 0x16
   1607   };
   1608 
   1609   // System V ABI, AMD64 Supplement, Version 0.99.5, Figure 3.36
   1610   enum RegisterMapping {
   1611     // Only the relevant ones have been added to reduce clutter.
   1612     AMD64_RBP = 6,
   1613     AMD64_RSP = 7,
   1614     AMD64_RA = 16
   1615   };
   1616 
   1617   enum CFIConstants {
   1618     CIE_ID = 0,
   1619     CIE_VERSION = 1,
   1620     CODE_ALIGN_FACTOR = 1,
   1621     DATA_ALIGN_FACTOR = 1,
   1622     RETURN_ADDRESS_REGISTER = AMD64_RA
   1623   };
   1624 };
   1625 
   1626 
   1627 void UnwindInfoSection::WriteLength(Writer* w,
   1628                                     Writer::Slot<uint32_t>* length_slot,
   1629                                     int initial_position) {
   1630   uint32_t align = (w->position() - initial_position) % kPointerSize;
   1631 
   1632   if (align != 0) {
   1633     for (uint32_t i = 0; i < (kPointerSize - align); i++) {
   1634       w->Write<uint8_t>(DW_CFA_NOP);
   1635     }
   1636   }
   1637 
   1638   ASSERT((w->position() - initial_position) % kPointerSize == 0);
   1639   length_slot->set(w->position() - initial_position);
   1640 }
   1641 
   1642 
   1643 UnwindInfoSection::UnwindInfoSection(CodeDescription* desc)
   1644 #ifdef __ELF
   1645     : ELFSection(".eh_frame", TYPE_X86_64_UNWIND, 1),
   1646 #else
   1647     : MachOSection("__eh_frame", "__TEXT", sizeof(uintptr_t),
   1648                    MachOSection::S_REGULAR),
   1649 #endif
   1650       desc_(desc) { }
   1651 
   1652 int UnwindInfoSection::WriteCIE(Writer* w) {
   1653   Writer::Slot<uint32_t> cie_length_slot = w->CreateSlotHere<uint32_t>();
   1654   uint32_t cie_position = w->position();
   1655 
   1656   // Write out the CIE header. Currently no 'common instructions' are
   1657   // emitted onto the CIE; every FDE has its own set of instructions.
   1658 
   1659   w->Write<uint32_t>(CIE_ID);
   1660   w->Write<uint8_t>(CIE_VERSION);
   1661   w->Write<uint8_t>(0);  // Null augmentation string.
   1662   w->WriteSLEB128(CODE_ALIGN_FACTOR);
   1663   w->WriteSLEB128(DATA_ALIGN_FACTOR);
   1664   w->Write<uint8_t>(RETURN_ADDRESS_REGISTER);
   1665 
   1666   WriteLength(w, &cie_length_slot, cie_position);
   1667 
   1668   return cie_position;
   1669 }
   1670 
   1671 
   1672 void UnwindInfoSection::WriteFDE(Writer* w, int cie_position) {
   1673   // The only FDE for this function. The CFA is the current RBP.
   1674   Writer::Slot<uint32_t> fde_length_slot = w->CreateSlotHere<uint32_t>();
   1675   int fde_position = w->position();
   1676   w->Write<int32_t>(fde_position - cie_position + 4);
   1677 
   1678   w->Write<uintptr_t>(desc_->CodeStart());
   1679   w->Write<uintptr_t>(desc_->CodeSize());
   1680 
   1681   WriteFDEStateOnEntry(w);
   1682   WriteFDEStateAfterRBPPush(w);
   1683   WriteFDEStateAfterRBPSet(w);
   1684   WriteFDEStateAfterRBPPop(w);
   1685 
   1686   WriteLength(w, &fde_length_slot, fde_position);
   1687 }
   1688 
   1689 
   1690 void UnwindInfoSection::WriteFDEStateOnEntry(Writer* w) {
   1691   // The first state, just after the control has been transferred to the the
   1692   // function.
   1693 
   1694   // RBP for this function will be the value of RSP after pushing the RBP
   1695   // for the previous function. The previous RBP has not been pushed yet.
   1696   w->Write<uint8_t>(DW_CFA_DEF_CFA_SF);
   1697   w->WriteULEB128(AMD64_RSP);
   1698   w->WriteSLEB128(-kPointerSize);
   1699 
   1700   // The RA is stored at location CFA + kCallerPCOffset. This is an invariant,
   1701   // and hence omitted from the next states.
   1702   w->Write<uint8_t>(DW_CFA_OFFSET_EXTENDED);
   1703   w->WriteULEB128(AMD64_RA);
   1704   w->WriteSLEB128(StandardFrameConstants::kCallerPCOffset);
   1705 
   1706   // The RBP of the previous function is still in RBP.
   1707   w->Write<uint8_t>(DW_CFA_SAME_VALUE);
   1708   w->WriteULEB128(AMD64_RBP);
   1709 
   1710   // Last location described by this entry.
   1711   w->Write<uint8_t>(DW_CFA_SET_LOC);
   1712   w->Write<uint64_t>(
   1713       desc_->GetStackStateStartAddress(CodeDescription::POST_RBP_PUSH));
   1714 }
   1715 
   1716 
   1717 void UnwindInfoSection::WriteFDEStateAfterRBPPush(Writer* w) {
   1718   // The second state, just after RBP has been pushed.
   1719 
   1720   // RBP / CFA for this function is now the current RSP, so just set the
   1721   // offset from the previous rule (from -8) to 0.
   1722   w->Write<uint8_t>(DW_CFA_DEF_CFA_OFFSET);
   1723   w->WriteULEB128(0);
   1724 
   1725   // The previous RBP is stored at CFA + kCallerFPOffset. This is an invariant
   1726   // in this and the next state, and hence omitted in the next state.
   1727   w->Write<uint8_t>(DW_CFA_OFFSET_EXTENDED);
   1728   w->WriteULEB128(AMD64_RBP);
   1729   w->WriteSLEB128(StandardFrameConstants::kCallerFPOffset);
   1730 
   1731   // Last location described by this entry.
   1732   w->Write<uint8_t>(DW_CFA_SET_LOC);
   1733   w->Write<uint64_t>(
   1734       desc_->GetStackStateStartAddress(CodeDescription::POST_RBP_SET));
   1735 }
   1736 
   1737 
   1738 void UnwindInfoSection::WriteFDEStateAfterRBPSet(Writer* w) {
   1739   // The third state, after the RBP has been set.
   1740 
   1741   // The CFA can now directly be set to RBP.
   1742   w->Write<uint8_t>(DW_CFA_DEF_CFA);
   1743   w->WriteULEB128(AMD64_RBP);
   1744   w->WriteULEB128(0);
   1745 
   1746   // Last location described by this entry.
   1747   w->Write<uint8_t>(DW_CFA_SET_LOC);
   1748   w->Write<uint64_t>(
   1749       desc_->GetStackStateStartAddress(CodeDescription::POST_RBP_POP));
   1750 }
   1751 
   1752 
   1753 void UnwindInfoSection::WriteFDEStateAfterRBPPop(Writer* w) {
   1754   // The fourth (final) state. The RBP has been popped (just before issuing a
   1755   // return).
   1756 
   1757   // The CFA can is now calculated in the same way as in the first state.
   1758   w->Write<uint8_t>(DW_CFA_DEF_CFA_SF);
   1759   w->WriteULEB128(AMD64_RSP);
   1760   w->WriteSLEB128(-kPointerSize);
   1761 
   1762   // The RBP
   1763   w->Write<uint8_t>(DW_CFA_OFFSET_EXTENDED);
   1764   w->WriteULEB128(AMD64_RBP);
   1765   w->WriteSLEB128(StandardFrameConstants::kCallerFPOffset);
   1766 
   1767   // Last location described by this entry.
   1768   w->Write<uint8_t>(DW_CFA_SET_LOC);
   1769   w->Write<uint64_t>(desc_->CodeEnd());
   1770 }
   1771 
   1772 
   1773 bool UnwindInfoSection::WriteBody(Writer* w) {
   1774   uint32_t cie_position = WriteCIE(w);
   1775   WriteFDE(w, cie_position);
   1776   return true;
   1777 }
   1778 
   1779 
   1780 #endif  // V8_TARGET_ARCH_X64
   1781 
   1782 static void CreateDWARFSections(CodeDescription* desc, DebugObject* obj) {
   1783   if (desc->IsLineInfoAvailable()) {
   1784     obj->AddSection(new DebugInfoSection(desc));
   1785     obj->AddSection(new DebugAbbrevSection(desc));
   1786     obj->AddSection(new DebugLineSection(desc));
   1787   }
   1788 #ifdef V8_TARGET_ARCH_X64
   1789   obj->AddSection(new UnwindInfoSection(desc));
   1790 #endif
   1791 }
   1792 
   1793 
   1794 // -------------------------------------------------------------------
   1795 // Binary GDB JIT Interface as described in
   1796 //   http://sourceware.org/gdb/onlinedocs/gdb/Declarations.html
   1797 extern "C" {
   1798   typedef enum {
   1799     JIT_NOACTION = 0,
   1800     JIT_REGISTER_FN,
   1801     JIT_UNREGISTER_FN
   1802   } JITAction;
   1803 
   1804   struct JITCodeEntry {
   1805     JITCodeEntry* next_;
   1806     JITCodeEntry* prev_;
   1807     Address symfile_addr_;
   1808     uint64_t symfile_size_;
   1809   };
   1810 
   1811   struct JITDescriptor {
   1812     uint32_t version_;
   1813     uint32_t action_flag_;
   1814     JITCodeEntry* relevant_entry_;
   1815     JITCodeEntry* first_entry_;
   1816   };
   1817 
   1818   // GDB will place breakpoint into this function.
   1819   // To prevent GCC from inlining or removing it we place noinline attribute
   1820   // and inline assembler statement inside.
   1821   void __attribute__((noinline)) __jit_debug_register_code() {
   1822     __asm__("");
   1823   }
   1824 
   1825   // GDB will inspect contents of this descriptor.
   1826   // Static initialization is necessary to prevent GDB from seeing
   1827   // uninitialized descriptor.
   1828   JITDescriptor __jit_debug_descriptor = { 1, 0, 0, 0 };
   1829 
   1830 #ifdef OBJECT_PRINT
   1831   void __gdb_print_v8_object(MaybeObject* object) {
   1832     object->Print();
   1833     fprintf(stdout, "\n");
   1834   }
   1835 #endif
   1836 }
   1837 
   1838 
   1839 static JITCodeEntry* CreateCodeEntry(Address symfile_addr,
   1840                                      uintptr_t symfile_size) {
   1841   JITCodeEntry* entry = static_cast<JITCodeEntry*>(
   1842       malloc(sizeof(JITCodeEntry) + symfile_size));
   1843 
   1844   entry->symfile_addr_ = reinterpret_cast<Address>(entry + 1);
   1845   entry->symfile_size_ = symfile_size;
   1846   memcpy(entry->symfile_addr_, symfile_addr, symfile_size);
   1847 
   1848   entry->prev_ = entry->next_ = NULL;
   1849 
   1850   return entry;
   1851 }
   1852 
   1853 
   1854 static void DestroyCodeEntry(JITCodeEntry* entry) {
   1855   free(entry);
   1856 }
   1857 
   1858 
   1859 static void RegisterCodeEntry(JITCodeEntry* entry,
   1860                               bool dump_if_enabled,
   1861                               const char* name_hint) {
   1862 #if defined(DEBUG) && !defined(WIN32)
   1863   static int file_num = 0;
   1864   if (FLAG_gdbjit_dump && dump_if_enabled) {
   1865     static const int kMaxFileNameSize = 64;
   1866     static const char* kElfFilePrefix = "/tmp/elfdump";
   1867     static const char* kObjFileExt = ".o";
   1868     char file_name[64];
   1869 
   1870     OS::SNPrintF(Vector<char>(file_name, kMaxFileNameSize),
   1871                  "%s%s%d%s",
   1872                  kElfFilePrefix,
   1873                  (name_hint != NULL) ? name_hint : "",
   1874                  file_num++,
   1875                  kObjFileExt);
   1876     WriteBytes(file_name, entry->symfile_addr_, entry->symfile_size_);
   1877   }
   1878 #endif
   1879 
   1880   entry->next_ = __jit_debug_descriptor.first_entry_;
   1881   if (entry->next_ != NULL) entry->next_->prev_ = entry;
   1882   __jit_debug_descriptor.first_entry_ =
   1883       __jit_debug_descriptor.relevant_entry_ = entry;
   1884 
   1885   __jit_debug_descriptor.action_flag_ = JIT_REGISTER_FN;
   1886   __jit_debug_register_code();
   1887 }
   1888 
   1889 
   1890 static void UnregisterCodeEntry(JITCodeEntry* entry) {
   1891   if (entry->prev_ != NULL) {
   1892     entry->prev_->next_ = entry->next_;
   1893   } else {
   1894     __jit_debug_descriptor.first_entry_ = entry->next_;
   1895   }
   1896 
   1897   if (entry->next_ != NULL) {
   1898     entry->next_->prev_ = entry->prev_;
   1899   }
   1900 
   1901   __jit_debug_descriptor.relevant_entry_ = entry;
   1902   __jit_debug_descriptor.action_flag_ = JIT_UNREGISTER_FN;
   1903   __jit_debug_register_code();
   1904 }
   1905 
   1906 
   1907 static JITCodeEntry* CreateELFObject(CodeDescription* desc) {
   1908   ZoneScope zone_scope(Isolate::Current(), DELETE_ON_EXIT);
   1909 #ifdef __MACH_O
   1910   MachO mach_o;
   1911   Writer w(&mach_o);
   1912 
   1913   mach_o.AddSection(new MachOTextSection(kCodeAlignment,
   1914                                          desc->CodeStart(),
   1915                                          desc->CodeSize()));
   1916 
   1917   CreateDWARFSections(desc, &mach_o);
   1918 
   1919   mach_o.Write(&w, desc->CodeStart(), desc->CodeSize());
   1920 #else
   1921   ELF elf;
   1922   Writer w(&elf);
   1923 
   1924   int text_section_index = elf.AddSection(
   1925       new FullHeaderELFSection(".text",
   1926                                ELFSection::TYPE_NOBITS,
   1927                                kCodeAlignment,
   1928                                desc->CodeStart(),
   1929                                0,
   1930                                desc->CodeSize(),
   1931                                ELFSection::FLAG_ALLOC | ELFSection::FLAG_EXEC));
   1932 
   1933   CreateSymbolsTable(desc, &elf, text_section_index);
   1934 
   1935   CreateDWARFSections(desc, &elf);
   1936 
   1937   elf.Write(&w);
   1938 #endif
   1939 
   1940   return CreateCodeEntry(w.buffer(), w.position());
   1941 }
   1942 
   1943 
   1944 static bool SameCodeObjects(void* key1, void* key2) {
   1945   return key1 == key2;
   1946 }
   1947 
   1948 
   1949 static HashMap* GetEntries() {
   1950   static HashMap* entries = NULL;
   1951   if (entries == NULL) {
   1952     entries = new HashMap(&SameCodeObjects);
   1953   }
   1954   return entries;
   1955 }
   1956 
   1957 
   1958 static uint32_t HashForCodeObject(Code* code) {
   1959   static const uintptr_t kGoldenRatio = 2654435761u;
   1960   uintptr_t hash = reinterpret_cast<uintptr_t>(code->address());
   1961   return static_cast<uint32_t>((hash >> kCodeAlignmentBits) * kGoldenRatio);
   1962 }
   1963 
   1964 
   1965 static const intptr_t kLineInfoTag = 0x1;
   1966 
   1967 
   1968 static bool IsLineInfoTagged(void* ptr) {
   1969   return 0 != (reinterpret_cast<intptr_t>(ptr) & kLineInfoTag);
   1970 }
   1971 
   1972 
   1973 static void* TagLineInfo(GDBJITLineInfo* ptr) {
   1974   return reinterpret_cast<void*>(
   1975       reinterpret_cast<intptr_t>(ptr) | kLineInfoTag);
   1976 }
   1977 
   1978 
   1979 static GDBJITLineInfo* UntagLineInfo(void* ptr) {
   1980   return reinterpret_cast<GDBJITLineInfo*>(
   1981       reinterpret_cast<intptr_t>(ptr) & ~kLineInfoTag);
   1982 }
   1983 
   1984 
   1985 void GDBJITInterface::AddCode(Handle<String> name,
   1986                               Handle<Script> script,
   1987                               Handle<Code> code,
   1988                               CompilationInfo* info) {
   1989   if (!FLAG_gdbjit) return;
   1990 
   1991   // Force initialization of line_ends array.
   1992   GetScriptLineNumber(script, 0);
   1993 
   1994   if (!name.is_null()) {
   1995     SmartArrayPointer<char> name_cstring = name->ToCString(DISALLOW_NULLS);
   1996     AddCode(*name_cstring, *code, GDBJITInterface::FUNCTION, *script, info);
   1997   } else {
   1998     AddCode("", *code, GDBJITInterface::FUNCTION, *script, info);
   1999   }
   2000 }
   2001 
   2002 static void AddUnwindInfo(CodeDescription* desc) {
   2003 #ifdef V8_TARGET_ARCH_X64
   2004   if (desc->tag() == GDBJITInterface::FUNCTION) {
   2005     // To avoid propagating unwinding information through
   2006     // compilation pipeline we use an approximation.
   2007     // For most use cases this should not affect usability.
   2008     static const int kFramePointerPushOffset = 1;
   2009     static const int kFramePointerSetOffset = 4;
   2010     static const int kFramePointerPopOffset = -3;
   2011 
   2012     uintptr_t frame_pointer_push_address =
   2013         desc->CodeStart() + kFramePointerPushOffset;
   2014 
   2015     uintptr_t frame_pointer_set_address =
   2016         desc->CodeStart() + kFramePointerSetOffset;
   2017 
   2018     uintptr_t frame_pointer_pop_address =
   2019         desc->CodeEnd() + kFramePointerPopOffset;
   2020 
   2021     desc->SetStackStateStartAddress(CodeDescription::POST_RBP_PUSH,
   2022                                     frame_pointer_push_address);
   2023     desc->SetStackStateStartAddress(CodeDescription::POST_RBP_SET,
   2024                                     frame_pointer_set_address);
   2025     desc->SetStackStateStartAddress(CodeDescription::POST_RBP_POP,
   2026                                     frame_pointer_pop_address);
   2027   } else {
   2028     desc->SetStackStateStartAddress(CodeDescription::POST_RBP_PUSH,
   2029                                     desc->CodeStart());
   2030     desc->SetStackStateStartAddress(CodeDescription::POST_RBP_SET,
   2031                                     desc->CodeStart());
   2032     desc->SetStackStateStartAddress(CodeDescription::POST_RBP_POP,
   2033                                     desc->CodeEnd());
   2034   }
   2035 #endif  // V8_TARGET_ARCH_X64
   2036 }
   2037 
   2038 
   2039 static LazyMutex mutex = LAZY_MUTEX_INITIALIZER;
   2040 
   2041 
   2042 void GDBJITInterface::AddCode(const char* name,
   2043                               Code* code,
   2044                               GDBJITInterface::CodeTag tag,
   2045                               Script* script,
   2046                               CompilationInfo* info) {
   2047   if (!FLAG_gdbjit) return;
   2048 
   2049   ScopedLock lock(mutex.Pointer());
   2050   AssertNoAllocation no_gc;
   2051 
   2052   HashMap::Entry* e = GetEntries()->Lookup(code, HashForCodeObject(code), true);
   2053   if (e->value != NULL && !IsLineInfoTagged(e->value)) return;
   2054 
   2055   GDBJITLineInfo* lineinfo = UntagLineInfo(e->value);
   2056   CodeDescription code_desc(name,
   2057                             code,
   2058                             script != NULL ? Handle<Script>(script)
   2059                                            : Handle<Script>(),
   2060                             lineinfo,
   2061                             tag,
   2062                             info);
   2063 
   2064   if (!FLAG_gdbjit_full && !code_desc.IsLineInfoAvailable()) {
   2065     delete lineinfo;
   2066     GetEntries()->Remove(code, HashForCodeObject(code));
   2067     return;
   2068   }
   2069 
   2070   AddUnwindInfo(&code_desc);
   2071   JITCodeEntry* entry = CreateELFObject(&code_desc);
   2072   ASSERT(!IsLineInfoTagged(entry));
   2073 
   2074   delete lineinfo;
   2075   e->value = entry;
   2076 
   2077   const char* name_hint = NULL;
   2078   bool should_dump = false;
   2079   if (FLAG_gdbjit_dump) {
   2080     if (strlen(FLAG_gdbjit_dump_filter) == 0) {
   2081       name_hint = name;
   2082       should_dump = true;
   2083     } else if (name != NULL) {
   2084       name_hint = strstr(name, FLAG_gdbjit_dump_filter);
   2085       should_dump = (name_hint != NULL);
   2086     }
   2087   }
   2088   RegisterCodeEntry(entry, should_dump, name_hint);
   2089 }
   2090 
   2091 
   2092 void GDBJITInterface::AddCode(GDBJITInterface::CodeTag tag,
   2093                               const char* name,
   2094                               Code* code) {
   2095   if (!FLAG_gdbjit) return;
   2096 
   2097   EmbeddedVector<char, 256> buffer;
   2098   StringBuilder builder(buffer.start(), buffer.length());
   2099 
   2100   builder.AddString(Tag2String(tag));
   2101   if ((name != NULL) && (*name != '\0')) {
   2102     builder.AddString(": ");
   2103     builder.AddString(name);
   2104   } else {
   2105     builder.AddFormatted(": code object %p", static_cast<void*>(code));
   2106   }
   2107 
   2108   AddCode(builder.Finalize(), code, tag, NULL, NULL);
   2109 }
   2110 
   2111 
   2112 void GDBJITInterface::AddCode(GDBJITInterface::CodeTag tag,
   2113                               String* name,
   2114                               Code* code) {
   2115   if (!FLAG_gdbjit) return;
   2116   AddCode(tag, name != NULL ? *name->ToCString(DISALLOW_NULLS) : NULL, code);
   2117 }
   2118 
   2119 
   2120 void GDBJITInterface::AddCode(GDBJITInterface::CodeTag tag, Code* code) {
   2121   if (!FLAG_gdbjit) return;
   2122 
   2123   AddCode(tag, "", code);
   2124 }
   2125 
   2126 
   2127 void GDBJITInterface::RemoveCode(Code* code) {
   2128   if (!FLAG_gdbjit) return;
   2129 
   2130   ScopedLock lock(mutex.Pointer());
   2131   HashMap::Entry* e = GetEntries()->Lookup(code,
   2132                                            HashForCodeObject(code),
   2133                                            false);
   2134   if (e == NULL) return;
   2135 
   2136   if (IsLineInfoTagged(e->value)) {
   2137     delete UntagLineInfo(e->value);
   2138   } else {
   2139     JITCodeEntry* entry = static_cast<JITCodeEntry*>(e->value);
   2140     UnregisterCodeEntry(entry);
   2141     DestroyCodeEntry(entry);
   2142   }
   2143   e->value = NULL;
   2144   GetEntries()->Remove(code, HashForCodeObject(code));
   2145 }
   2146 
   2147 
   2148 void GDBJITInterface::RegisterDetailedLineInfo(Code* code,
   2149                                                GDBJITLineInfo* line_info) {
   2150   ScopedLock lock(mutex.Pointer());
   2151   ASSERT(!IsLineInfoTagged(line_info));
   2152   HashMap::Entry* e = GetEntries()->Lookup(code, HashForCodeObject(code), true);
   2153   ASSERT(e->value == NULL);
   2154   e->value = TagLineInfo(line_info);
   2155 }
   2156 
   2157 
   2158 } }  // namespace v8::internal
   2159 #endif
   2160