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      1 //===-- DWARFDebugLine.cpp ------------------------------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 
     10 #include "llvm/DebugInfo/DWARF/DWARFDebugLine.h"
     11 #include "llvm/Support/Dwarf.h"
     12 #include "llvm/Support/Format.h"
     13 #include "llvm/Support/Path.h"
     14 #include "llvm/Support/raw_ostream.h"
     15 #include <algorithm>
     16 using namespace llvm;
     17 using namespace dwarf;
     18 typedef DILineInfoSpecifier::FileLineInfoKind FileLineInfoKind;
     19 
     20 DWARFDebugLine::Prologue::Prologue() { clear(); }
     21 
     22 void DWARFDebugLine::Prologue::clear() {
     23   TotalLength = Version = PrologueLength = 0;
     24   MinInstLength = MaxOpsPerInst = DefaultIsStmt = LineBase = LineRange = 0;
     25   OpcodeBase = 0;
     26   IsDWARF64 = false;
     27   StandardOpcodeLengths.clear();
     28   IncludeDirectories.clear();
     29   FileNames.clear();
     30 }
     31 
     32 void DWARFDebugLine::Prologue::dump(raw_ostream &OS) const {
     33   OS << "Line table prologue:\n"
     34      << format("    total_length: 0x%8.8" PRIx64 "\n", TotalLength)
     35      << format("         version: %u\n", Version)
     36      << format(" prologue_length: 0x%8.8" PRIx64 "\n", PrologueLength)
     37      << format(" min_inst_length: %u\n", MinInstLength)
     38      << format(Version >= 4 ? "max_ops_per_inst: %u\n" : "", MaxOpsPerInst)
     39      << format(" default_is_stmt: %u\n", DefaultIsStmt)
     40      << format("       line_base: %i\n", LineBase)
     41      << format("      line_range: %u\n", LineRange)
     42      << format("     opcode_base: %u\n", OpcodeBase);
     43 
     44   for (uint32_t i = 0; i < StandardOpcodeLengths.size(); ++i)
     45     OS << format("standard_opcode_lengths[%s] = %u\n", LNStandardString(i + 1),
     46                  StandardOpcodeLengths[i]);
     47 
     48   if (!IncludeDirectories.empty())
     49     for (uint32_t i = 0; i < IncludeDirectories.size(); ++i)
     50       OS << format("include_directories[%3u] = '", i + 1)
     51          << IncludeDirectories[i] << "'\n";
     52 
     53   if (!FileNames.empty()) {
     54     OS << "                Dir  Mod Time   File Len   File Name\n"
     55        << "                ---- ---------- ---------- -----------"
     56           "----------------\n";
     57     for (uint32_t i = 0; i < FileNames.size(); ++i) {
     58       const FileNameEntry &fileEntry = FileNames[i];
     59       OS << format("file_names[%3u] %4" PRIu64 " ", i + 1, fileEntry.DirIdx)
     60          << format("0x%8.8" PRIx64 " 0x%8.8" PRIx64 " ", fileEntry.ModTime,
     61                    fileEntry.Length)
     62          << fileEntry.Name << '\n';
     63     }
     64   }
     65 }
     66 
     67 bool DWARFDebugLine::Prologue::parse(DataExtractor debug_line_data,
     68                                      uint32_t *offset_ptr) {
     69   const uint64_t prologue_offset = *offset_ptr;
     70 
     71   clear();
     72   TotalLength = debug_line_data.getU32(offset_ptr);
     73   if (TotalLength == UINT32_MAX) {
     74     IsDWARF64 = true;
     75     TotalLength = debug_line_data.getU64(offset_ptr);
     76   } else if (TotalLength > 0xffffff00) {
     77     return false;
     78   }
     79   Version = debug_line_data.getU16(offset_ptr);
     80   if (Version < 2)
     81     return false;
     82 
     83   PrologueLength =
     84       debug_line_data.getUnsigned(offset_ptr, sizeofPrologueLength());
     85   const uint64_t end_prologue_offset = PrologueLength + *offset_ptr;
     86   MinInstLength = debug_line_data.getU8(offset_ptr);
     87   if (Version >= 4)
     88     MaxOpsPerInst = debug_line_data.getU8(offset_ptr);
     89   DefaultIsStmt = debug_line_data.getU8(offset_ptr);
     90   LineBase = debug_line_data.getU8(offset_ptr);
     91   LineRange = debug_line_data.getU8(offset_ptr);
     92   OpcodeBase = debug_line_data.getU8(offset_ptr);
     93 
     94   StandardOpcodeLengths.reserve(OpcodeBase - 1);
     95   for (uint32_t i = 1; i < OpcodeBase; ++i) {
     96     uint8_t op_len = debug_line_data.getU8(offset_ptr);
     97     StandardOpcodeLengths.push_back(op_len);
     98   }
     99 
    100   while (*offset_ptr < end_prologue_offset) {
    101     const char *s = debug_line_data.getCStr(offset_ptr);
    102     if (s && s[0])
    103       IncludeDirectories.push_back(s);
    104     else
    105       break;
    106   }
    107 
    108   while (*offset_ptr < end_prologue_offset) {
    109     const char *name = debug_line_data.getCStr(offset_ptr);
    110     if (name && name[0]) {
    111       FileNameEntry fileEntry;
    112       fileEntry.Name = name;
    113       fileEntry.DirIdx = debug_line_data.getULEB128(offset_ptr);
    114       fileEntry.ModTime = debug_line_data.getULEB128(offset_ptr);
    115       fileEntry.Length = debug_line_data.getULEB128(offset_ptr);
    116       FileNames.push_back(fileEntry);
    117     } else {
    118       break;
    119     }
    120   }
    121 
    122   if (*offset_ptr != end_prologue_offset) {
    123     fprintf(stderr, "warning: parsing line table prologue at 0x%8.8" PRIx64
    124                     " should have ended at 0x%8.8" PRIx64
    125                     " but it ended at 0x%8.8" PRIx64 "\n",
    126             prologue_offset, end_prologue_offset, (uint64_t)*offset_ptr);
    127     return false;
    128   }
    129   return true;
    130 }
    131 
    132 DWARFDebugLine::Row::Row(bool default_is_stmt) { reset(default_is_stmt); }
    133 
    134 void DWARFDebugLine::Row::postAppend() {
    135   BasicBlock = false;
    136   PrologueEnd = false;
    137   EpilogueBegin = false;
    138 }
    139 
    140 void DWARFDebugLine::Row::reset(bool default_is_stmt) {
    141   Address = 0;
    142   Line = 1;
    143   Column = 0;
    144   File = 1;
    145   Isa = 0;
    146   Discriminator = 0;
    147   IsStmt = default_is_stmt;
    148   BasicBlock = false;
    149   EndSequence = false;
    150   PrologueEnd = false;
    151   EpilogueBegin = false;
    152 }
    153 
    154 void DWARFDebugLine::Row::dump(raw_ostream &OS) const {
    155   OS << format("0x%16.16" PRIx64 " %6u %6u", Address, Line, Column)
    156      << format(" %6u %3u %13u ", File, Isa, Discriminator)
    157      << (IsStmt ? " is_stmt" : "") << (BasicBlock ? " basic_block" : "")
    158      << (PrologueEnd ? " prologue_end" : "")
    159      << (EpilogueBegin ? " epilogue_begin" : "")
    160      << (EndSequence ? " end_sequence" : "") << '\n';
    161 }
    162 
    163 DWARFDebugLine::Sequence::Sequence() { reset(); }
    164 
    165 void DWARFDebugLine::Sequence::reset() {
    166   LowPC = 0;
    167   HighPC = 0;
    168   FirstRowIndex = 0;
    169   LastRowIndex = 0;
    170   Empty = true;
    171 }
    172 
    173 DWARFDebugLine::LineTable::LineTable() { clear(); }
    174 
    175 void DWARFDebugLine::LineTable::dump(raw_ostream &OS) const {
    176   Prologue.dump(OS);
    177   OS << '\n';
    178 
    179   if (!Rows.empty()) {
    180     OS << "Address            Line   Column File   ISA Discriminator Flags\n"
    181        << "------------------ ------ ------ ------ --- ------------- "
    182           "-------------\n";
    183     for (const Row &R : Rows) {
    184       R.dump(OS);
    185     }
    186   }
    187 }
    188 
    189 void DWARFDebugLine::LineTable::clear() {
    190   Prologue.clear();
    191   Rows.clear();
    192   Sequences.clear();
    193 }
    194 
    195 DWARFDebugLine::ParsingState::ParsingState(struct LineTable *LT)
    196     : LineTable(LT), RowNumber(0) {
    197   resetRowAndSequence();
    198 }
    199 
    200 void DWARFDebugLine::ParsingState::resetRowAndSequence() {
    201   Row.reset(LineTable->Prologue.DefaultIsStmt);
    202   Sequence.reset();
    203 }
    204 
    205 void DWARFDebugLine::ParsingState::appendRowToMatrix(uint32_t offset) {
    206   if (Sequence.Empty) {
    207     // Record the beginning of instruction sequence.
    208     Sequence.Empty = false;
    209     Sequence.LowPC = Row.Address;
    210     Sequence.FirstRowIndex = RowNumber;
    211   }
    212   ++RowNumber;
    213   LineTable->appendRow(Row);
    214   if (Row.EndSequence) {
    215     // Record the end of instruction sequence.
    216     Sequence.HighPC = Row.Address;
    217     Sequence.LastRowIndex = RowNumber;
    218     if (Sequence.isValid())
    219       LineTable->appendSequence(Sequence);
    220     Sequence.reset();
    221   }
    222   Row.postAppend();
    223 }
    224 
    225 const DWARFDebugLine::LineTable *
    226 DWARFDebugLine::getLineTable(uint32_t offset) const {
    227   LineTableConstIter pos = LineTableMap.find(offset);
    228   if (pos != LineTableMap.end())
    229     return &pos->second;
    230   return nullptr;
    231 }
    232 
    233 const DWARFDebugLine::LineTable *
    234 DWARFDebugLine::getOrParseLineTable(DataExtractor debug_line_data,
    235                                     uint32_t offset) {
    236   std::pair<LineTableIter, bool> pos =
    237       LineTableMap.insert(LineTableMapTy::value_type(offset, LineTable()));
    238   LineTable *LT = &pos.first->second;
    239   if (pos.second) {
    240     if (!LT->parse(debug_line_data, RelocMap, &offset))
    241       return nullptr;
    242   }
    243   return LT;
    244 }
    245 
    246 bool DWARFDebugLine::LineTable::parse(DataExtractor debug_line_data,
    247                                       const RelocAddrMap *RMap,
    248                                       uint32_t *offset_ptr) {
    249   const uint32_t debug_line_offset = *offset_ptr;
    250 
    251   clear();
    252 
    253   if (!Prologue.parse(debug_line_data, offset_ptr)) {
    254     // Restore our offset and return false to indicate failure!
    255     *offset_ptr = debug_line_offset;
    256     return false;
    257   }
    258 
    259   const uint32_t end_offset =
    260       debug_line_offset + Prologue.TotalLength + Prologue.sizeofTotalLength();
    261 
    262   ParsingState State(this);
    263 
    264   while (*offset_ptr < end_offset) {
    265     uint8_t opcode = debug_line_data.getU8(offset_ptr);
    266 
    267     if (opcode == 0) {
    268       // Extended Opcodes always start with a zero opcode followed by
    269       // a uleb128 length so you can skip ones you don't know about
    270       uint32_t ext_offset = *offset_ptr;
    271       uint64_t len = debug_line_data.getULEB128(offset_ptr);
    272       uint32_t arg_size = len - (*offset_ptr - ext_offset);
    273 
    274       uint8_t sub_opcode = debug_line_data.getU8(offset_ptr);
    275       switch (sub_opcode) {
    276       case DW_LNE_end_sequence:
    277         // Set the end_sequence register of the state machine to true and
    278         // append a row to the matrix using the current values of the
    279         // state-machine registers. Then reset the registers to the initial
    280         // values specified above. Every statement program sequence must end
    281         // with a DW_LNE_end_sequence instruction which creates a row whose
    282         // address is that of the byte after the last target machine instruction
    283         // of the sequence.
    284         State.Row.EndSequence = true;
    285         State.appendRowToMatrix(*offset_ptr);
    286         State.resetRowAndSequence();
    287         break;
    288 
    289       case DW_LNE_set_address:
    290         // Takes a single relocatable address as an operand. The size of the
    291         // operand is the size appropriate to hold an address on the target
    292         // machine. Set the address register to the value given by the
    293         // relocatable address. All of the other statement program opcodes
    294         // that affect the address register add a delta to it. This instruction
    295         // stores a relocatable value into it instead.
    296         {
    297           // If this address is in our relocation map, apply the relocation.
    298           RelocAddrMap::const_iterator AI = RMap->find(*offset_ptr);
    299           if (AI != RMap->end()) {
    300             const std::pair<uint8_t, int64_t> &R = AI->second;
    301             State.Row.Address =
    302                 debug_line_data.getAddress(offset_ptr) + R.second;
    303           } else
    304             State.Row.Address = debug_line_data.getAddress(offset_ptr);
    305         }
    306         break;
    307 
    308       case DW_LNE_define_file:
    309         // Takes 4 arguments. The first is a null terminated string containing
    310         // a source file name. The second is an unsigned LEB128 number
    311         // representing the directory index of the directory in which the file
    312         // was found. The third is an unsigned LEB128 number representing the
    313         // time of last modification of the file. The fourth is an unsigned
    314         // LEB128 number representing the length in bytes of the file. The time
    315         // and length fields may contain LEB128(0) if the information is not
    316         // available.
    317         //
    318         // The directory index represents an entry in the include_directories
    319         // section of the statement program prologue. The index is LEB128(0)
    320         // if the file was found in the current directory of the compilation,
    321         // LEB128(1) if it was found in the first directory in the
    322         // include_directories section, and so on. The directory index is
    323         // ignored for file names that represent full path names.
    324         //
    325         // The files are numbered, starting at 1, in the order in which they
    326         // appear; the names in the prologue come before names defined by
    327         // the DW_LNE_define_file instruction. These numbers are used in the
    328         // the file register of the state machine.
    329         {
    330           FileNameEntry fileEntry;
    331           fileEntry.Name = debug_line_data.getCStr(offset_ptr);
    332           fileEntry.DirIdx = debug_line_data.getULEB128(offset_ptr);
    333           fileEntry.ModTime = debug_line_data.getULEB128(offset_ptr);
    334           fileEntry.Length = debug_line_data.getULEB128(offset_ptr);
    335           Prologue.FileNames.push_back(fileEntry);
    336         }
    337         break;
    338 
    339       case DW_LNE_set_discriminator:
    340         State.Row.Discriminator = debug_line_data.getULEB128(offset_ptr);
    341         break;
    342 
    343       default:
    344         // Length doesn't include the zero opcode byte or the length itself, but
    345         // it does include the sub_opcode, so we have to adjust for that below
    346         (*offset_ptr) += arg_size;
    347         break;
    348       }
    349     } else if (opcode < Prologue.OpcodeBase) {
    350       switch (opcode) {
    351       // Standard Opcodes
    352       case DW_LNS_copy:
    353         // Takes no arguments. Append a row to the matrix using the
    354         // current values of the state-machine registers. Then set
    355         // the basic_block register to false.
    356         State.appendRowToMatrix(*offset_ptr);
    357         break;
    358 
    359       case DW_LNS_advance_pc:
    360         // Takes a single unsigned LEB128 operand, multiplies it by the
    361         // min_inst_length field of the prologue, and adds the
    362         // result to the address register of the state machine.
    363         State.Row.Address +=
    364             debug_line_data.getULEB128(offset_ptr) * Prologue.MinInstLength;
    365         break;
    366 
    367       case DW_LNS_advance_line:
    368         // Takes a single signed LEB128 operand and adds that value to
    369         // the line register of the state machine.
    370         State.Row.Line += debug_line_data.getSLEB128(offset_ptr);
    371         break;
    372 
    373       case DW_LNS_set_file:
    374         // Takes a single unsigned LEB128 operand and stores it in the file
    375         // register of the state machine.
    376         State.Row.File = debug_line_data.getULEB128(offset_ptr);
    377         break;
    378 
    379       case DW_LNS_set_column:
    380         // Takes a single unsigned LEB128 operand and stores it in the
    381         // column register of the state machine.
    382         State.Row.Column = debug_line_data.getULEB128(offset_ptr);
    383         break;
    384 
    385       case DW_LNS_negate_stmt:
    386         // Takes no arguments. Set the is_stmt register of the state
    387         // machine to the logical negation of its current value.
    388         State.Row.IsStmt = !State.Row.IsStmt;
    389         break;
    390 
    391       case DW_LNS_set_basic_block:
    392         // Takes no arguments. Set the basic_block register of the
    393         // state machine to true
    394         State.Row.BasicBlock = true;
    395         break;
    396 
    397       case DW_LNS_const_add_pc:
    398         // Takes no arguments. Add to the address register of the state
    399         // machine the address increment value corresponding to special
    400         // opcode 255. The motivation for DW_LNS_const_add_pc is this:
    401         // when the statement program needs to advance the address by a
    402         // small amount, it can use a single special opcode, which occupies
    403         // a single byte. When it needs to advance the address by up to
    404         // twice the range of the last special opcode, it can use
    405         // DW_LNS_const_add_pc followed by a special opcode, for a total
    406         // of two bytes. Only if it needs to advance the address by more
    407         // than twice that range will it need to use both DW_LNS_advance_pc
    408         // and a special opcode, requiring three or more bytes.
    409         {
    410           uint8_t adjust_opcode = 255 - Prologue.OpcodeBase;
    411           uint64_t addr_offset =
    412               (adjust_opcode / Prologue.LineRange) * Prologue.MinInstLength;
    413           State.Row.Address += addr_offset;
    414         }
    415         break;
    416 
    417       case DW_LNS_fixed_advance_pc:
    418         // Takes a single uhalf operand. Add to the address register of
    419         // the state machine the value of the (unencoded) operand. This
    420         // is the only extended opcode that takes an argument that is not
    421         // a variable length number. The motivation for DW_LNS_fixed_advance_pc
    422         // is this: existing assemblers cannot emit DW_LNS_advance_pc or
    423         // special opcodes because they cannot encode LEB128 numbers or
    424         // judge when the computation of a special opcode overflows and
    425         // requires the use of DW_LNS_advance_pc. Such assemblers, however,
    426         // can use DW_LNS_fixed_advance_pc instead, sacrificing compression.
    427         State.Row.Address += debug_line_data.getU16(offset_ptr);
    428         break;
    429 
    430       case DW_LNS_set_prologue_end:
    431         // Takes no arguments. Set the prologue_end register of the
    432         // state machine to true
    433         State.Row.PrologueEnd = true;
    434         break;
    435 
    436       case DW_LNS_set_epilogue_begin:
    437         // Takes no arguments. Set the basic_block register of the
    438         // state machine to true
    439         State.Row.EpilogueBegin = true;
    440         break;
    441 
    442       case DW_LNS_set_isa:
    443         // Takes a single unsigned LEB128 operand and stores it in the
    444         // column register of the state machine.
    445         State.Row.Isa = debug_line_data.getULEB128(offset_ptr);
    446         break;
    447 
    448       default:
    449         // Handle any unknown standard opcodes here. We know the lengths
    450         // of such opcodes because they are specified in the prologue
    451         // as a multiple of LEB128 operands for each opcode.
    452         {
    453           assert(opcode - 1U < Prologue.StandardOpcodeLengths.size());
    454           uint8_t opcode_length = Prologue.StandardOpcodeLengths[opcode - 1];
    455           for (uint8_t i = 0; i < opcode_length; ++i)
    456             debug_line_data.getULEB128(offset_ptr);
    457         }
    458         break;
    459       }
    460     } else {
    461       // Special Opcodes
    462 
    463       // A special opcode value is chosen based on the amount that needs
    464       // to be added to the line and address registers. The maximum line
    465       // increment for a special opcode is the value of the line_base
    466       // field in the header, plus the value of the line_range field,
    467       // minus 1 (line base + line range - 1). If the desired line
    468       // increment is greater than the maximum line increment, a standard
    469       // opcode must be used instead of a special opcode. The "address
    470       // advance" is calculated by dividing the desired address increment
    471       // by the minimum_instruction_length field from the header. The
    472       // special opcode is then calculated using the following formula:
    473       //
    474       //  opcode = (desired line increment - line_base) +
    475       //           (line_range * address advance) + opcode_base
    476       //
    477       // If the resulting opcode is greater than 255, a standard opcode
    478       // must be used instead.
    479       //
    480       // To decode a special opcode, subtract the opcode_base from the
    481       // opcode itself to give the adjusted opcode. The amount to
    482       // increment the address register is the result of the adjusted
    483       // opcode divided by the line_range multiplied by the
    484       // minimum_instruction_length field from the header. That is:
    485       //
    486       //  address increment = (adjusted opcode / line_range) *
    487       //                      minimum_instruction_length
    488       //
    489       // The amount to increment the line register is the line_base plus
    490       // the result of the adjusted opcode modulo the line_range. That is:
    491       //
    492       // line increment = line_base + (adjusted opcode % line_range)
    493 
    494       uint8_t adjust_opcode = opcode - Prologue.OpcodeBase;
    495       uint64_t addr_offset =
    496           (adjust_opcode / Prologue.LineRange) * Prologue.MinInstLength;
    497       int32_t line_offset =
    498           Prologue.LineBase + (adjust_opcode % Prologue.LineRange);
    499       State.Row.Line += line_offset;
    500       State.Row.Address += addr_offset;
    501       State.appendRowToMatrix(*offset_ptr);
    502       // Reset discriminator to 0.
    503       State.Row.Discriminator = 0;
    504     }
    505   }
    506 
    507   if (!State.Sequence.Empty) {
    508     fprintf(stderr, "warning: last sequence in debug line table is not"
    509                     "terminated!\n");
    510   }
    511 
    512   // Sort all sequences so that address lookup will work faster.
    513   if (!Sequences.empty()) {
    514     std::sort(Sequences.begin(), Sequences.end(), Sequence::orderByLowPC);
    515     // Note: actually, instruction address ranges of sequences should not
    516     // overlap (in shared objects and executables). If they do, the address
    517     // lookup would still work, though, but result would be ambiguous.
    518     // We don't report warning in this case. For example,
    519     // sometimes .so compiled from multiple object files contains a few
    520     // rudimentary sequences for address ranges [0x0, 0xsomething).
    521   }
    522 
    523   return end_offset;
    524 }
    525 
    526 uint32_t
    527 DWARFDebugLine::LineTable::findRowInSeq(const DWARFDebugLine::Sequence &seq,
    528                                         uint64_t address) const {
    529   if (!seq.containsPC(address))
    530     return UnknownRowIndex;
    531   // Search for instruction address in the rows describing the sequence.
    532   // Rows are stored in a vector, so we may use arithmetical operations with
    533   // iterators.
    534   DWARFDebugLine::Row row;
    535   row.Address = address;
    536   RowIter first_row = Rows.begin() + seq.FirstRowIndex;
    537   RowIter last_row = Rows.begin() + seq.LastRowIndex;
    538   LineTable::RowIter row_pos = std::lower_bound(
    539       first_row, last_row, row, DWARFDebugLine::Row::orderByAddress);
    540   if (row_pos == last_row) {
    541     return seq.LastRowIndex - 1;
    542   }
    543   uint32_t index = seq.FirstRowIndex + (row_pos - first_row);
    544   if (row_pos->Address > address) {
    545     if (row_pos == first_row)
    546       return UnknownRowIndex;
    547     else
    548       index--;
    549   }
    550   return index;
    551 }
    552 
    553 uint32_t DWARFDebugLine::LineTable::lookupAddress(uint64_t address) const {
    554   if (Sequences.empty())
    555     return UnknownRowIndex;
    556   // First, find an instruction sequence containing the given address.
    557   DWARFDebugLine::Sequence sequence;
    558   sequence.LowPC = address;
    559   SequenceIter first_seq = Sequences.begin();
    560   SequenceIter last_seq = Sequences.end();
    561   SequenceIter seq_pos = std::lower_bound(
    562       first_seq, last_seq, sequence, DWARFDebugLine::Sequence::orderByLowPC);
    563   DWARFDebugLine::Sequence found_seq;
    564   if (seq_pos == last_seq) {
    565     found_seq = Sequences.back();
    566   } else if (seq_pos->LowPC == address) {
    567     found_seq = *seq_pos;
    568   } else {
    569     if (seq_pos == first_seq)
    570       return UnknownRowIndex;
    571     found_seq = *(seq_pos - 1);
    572   }
    573   return findRowInSeq(found_seq, address);
    574 }
    575 
    576 bool DWARFDebugLine::LineTable::lookupAddressRange(
    577     uint64_t address, uint64_t size, std::vector<uint32_t> &result) const {
    578   if (Sequences.empty())
    579     return false;
    580   uint64_t end_addr = address + size;
    581   // First, find an instruction sequence containing the given address.
    582   DWARFDebugLine::Sequence sequence;
    583   sequence.LowPC = address;
    584   SequenceIter first_seq = Sequences.begin();
    585   SequenceIter last_seq = Sequences.end();
    586   SequenceIter seq_pos = std::lower_bound(
    587       first_seq, last_seq, sequence, DWARFDebugLine::Sequence::orderByLowPC);
    588   if (seq_pos == last_seq || seq_pos->LowPC != address) {
    589     if (seq_pos == first_seq)
    590       return false;
    591     seq_pos--;
    592   }
    593   if (!seq_pos->containsPC(address))
    594     return false;
    595 
    596   SequenceIter start_pos = seq_pos;
    597 
    598   // Add the rows from the first sequence to the vector, starting with the
    599   // index we just calculated
    600 
    601   while (seq_pos != last_seq && seq_pos->LowPC < end_addr) {
    602     const DWARFDebugLine::Sequence &cur_seq = *seq_pos;
    603     // For the first sequence, we need to find which row in the sequence is the
    604     // first in our range.
    605     uint32_t first_row_index = cur_seq.FirstRowIndex;
    606     if (seq_pos == start_pos)
    607       first_row_index = findRowInSeq(cur_seq, address);
    608 
    609     // Figure out the last row in the range.
    610     uint32_t last_row_index = findRowInSeq(cur_seq, end_addr - 1);
    611     if (last_row_index == UnknownRowIndex)
    612       last_row_index = cur_seq.LastRowIndex - 1;
    613 
    614     assert(first_row_index != UnknownRowIndex);
    615     assert(last_row_index != UnknownRowIndex);
    616 
    617     for (uint32_t i = first_row_index; i <= last_row_index; ++i) {
    618       result.push_back(i);
    619     }
    620 
    621     ++seq_pos;
    622   }
    623 
    624   return true;
    625 }
    626 
    627 bool DWARFDebugLine::LineTable::getFileNameByIndex(uint64_t FileIndex,
    628                                                    const char *CompDir,
    629                                                    FileLineInfoKind Kind,
    630                                                    std::string &Result) const {
    631   if (FileIndex == 0 || FileIndex > Prologue.FileNames.size() ||
    632       Kind == FileLineInfoKind::None)
    633     return false;
    634   const FileNameEntry &Entry = Prologue.FileNames[FileIndex - 1];
    635   const char *FileName = Entry.Name;
    636   if (Kind != FileLineInfoKind::AbsoluteFilePath ||
    637       sys::path::is_absolute(FileName)) {
    638     Result = FileName;
    639     return true;
    640   }
    641 
    642   SmallString<16> FilePath;
    643   uint64_t IncludeDirIndex = Entry.DirIdx;
    644   const char *IncludeDir = "";
    645   // Be defensive about the contents of Entry.
    646   if (IncludeDirIndex > 0 &&
    647       IncludeDirIndex <= Prologue.IncludeDirectories.size())
    648     IncludeDir = Prologue.IncludeDirectories[IncludeDirIndex - 1];
    649 
    650   // We may still need to append compilation directory of compile unit.
    651   // We know that FileName is not absolute, the only way to have an
    652   // absolute path at this point would be if IncludeDir is absolute.
    653   if (CompDir && Kind == FileLineInfoKind::AbsoluteFilePath &&
    654       sys::path::is_relative(IncludeDir))
    655     sys::path::append(FilePath, CompDir);
    656 
    657   // sys::path::append skips empty strings.
    658   sys::path::append(FilePath, IncludeDir, FileName);
    659   Result = FilePath.str();
    660   return true;
    661 }
    662 
    663 bool DWARFDebugLine::LineTable::getFileLineInfoForAddress(
    664     uint64_t Address, const char *CompDir, FileLineInfoKind Kind,
    665     DILineInfo &Result) const {
    666   // Get the index of row we're looking for in the line table.
    667   uint32_t RowIndex = lookupAddress(Address);
    668   if (RowIndex == -1U)
    669     return false;
    670   // Take file number and line/column from the row.
    671   const auto &Row = Rows[RowIndex];
    672   if (!getFileNameByIndex(Row.File, CompDir, Kind, Result.FileName))
    673     return false;
    674   Result.Line = Row.Line;
    675   Result.Column = Row.Column;
    676   return true;
    677 }
    678