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      1 //===- ELFAsmParser.cpp - ELF Assembly Parser -----------------------------===//
      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/MC/MCParser/MCAsmParserExtension.h"
     11 #include "llvm/ADT/StringSwitch.h"
     12 #include "llvm/ADT/Twine.h"
     13 #include "llvm/MC/MCAsmInfo.h"
     14 #include "llvm/MC/MCContext.h"
     15 #include "llvm/MC/MCExpr.h"
     16 #include "llvm/MC/MCParser/MCAsmLexer.h"
     17 #include "llvm/MC/MCSectionELF.h"
     18 #include "llvm/MC/MCStreamer.h"
     19 #include "llvm/MC/MCSymbol.h"
     20 #include "llvm/Support/ELF.h"
     21 using namespace llvm;
     22 
     23 namespace {
     24 
     25 class ELFAsmParser : public MCAsmParserExtension {
     26   template<bool (ELFAsmParser::*HandlerMethod)(StringRef, SMLoc)>
     27   void addDirectiveHandler(StringRef Directive) {
     28     MCAsmParser::ExtensionDirectiveHandler Handler = std::make_pair(
     29         this, HandleDirective<ELFAsmParser, HandlerMethod>);
     30 
     31     getParser().addDirectiveHandler(Directive, Handler);
     32   }
     33 
     34   bool ParseSectionSwitch(StringRef Section, unsigned Type, unsigned Flags,
     35                           SectionKind Kind);
     36 
     37 public:
     38   ELFAsmParser() { BracketExpressionsSupported = true; }
     39 
     40   void Initialize(MCAsmParser &Parser) override {
     41     // Call the base implementation.
     42     this->MCAsmParserExtension::Initialize(Parser);
     43 
     44     addDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveData>(".data");
     45     addDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveText>(".text");
     46     addDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveBSS>(".bss");
     47     addDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveRoData>(".rodata");
     48     addDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveTData>(".tdata");
     49     addDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveTBSS>(".tbss");
     50     addDirectiveHandler<
     51       &ELFAsmParser::ParseSectionDirectiveDataRel>(".data.rel");
     52     addDirectiveHandler<
     53       &ELFAsmParser::ParseSectionDirectiveDataRelRo>(".data.rel.ro");
     54     addDirectiveHandler<
     55       &ELFAsmParser::ParseSectionDirectiveDataRelRoLocal>(".data.rel.ro.local");
     56     addDirectiveHandler<
     57       &ELFAsmParser::ParseSectionDirectiveEhFrame>(".eh_frame");
     58     addDirectiveHandler<&ELFAsmParser::ParseDirectiveSection>(".section");
     59     addDirectiveHandler<
     60       &ELFAsmParser::ParseDirectivePushSection>(".pushsection");
     61     addDirectiveHandler<&ELFAsmParser::ParseDirectivePopSection>(".popsection");
     62     addDirectiveHandler<&ELFAsmParser::ParseDirectiveSize>(".size");
     63     addDirectiveHandler<&ELFAsmParser::ParseDirectivePrevious>(".previous");
     64     addDirectiveHandler<&ELFAsmParser::ParseDirectiveType>(".type");
     65     addDirectiveHandler<&ELFAsmParser::ParseDirectiveIdent>(".ident");
     66     addDirectiveHandler<&ELFAsmParser::ParseDirectiveSymver>(".symver");
     67     addDirectiveHandler<&ELFAsmParser::ParseDirectiveVersion>(".version");
     68     addDirectiveHandler<&ELFAsmParser::ParseDirectiveWeakref>(".weakref");
     69     addDirectiveHandler<&ELFAsmParser::ParseDirectiveSymbolAttribute>(".weak");
     70     addDirectiveHandler<&ELFAsmParser::ParseDirectiveSymbolAttribute>(".local");
     71     addDirectiveHandler<
     72       &ELFAsmParser::ParseDirectiveSymbolAttribute>(".protected");
     73     addDirectiveHandler<
     74       &ELFAsmParser::ParseDirectiveSymbolAttribute>(".internal");
     75     addDirectiveHandler<
     76       &ELFAsmParser::ParseDirectiveSymbolAttribute>(".hidden");
     77     addDirectiveHandler<&ELFAsmParser::ParseDirectiveSubsection>(".subsection");
     78   }
     79 
     80   // FIXME: Part of this logic is duplicated in the MCELFStreamer. What is
     81   // the best way for us to get access to it?
     82   bool ParseSectionDirectiveData(StringRef, SMLoc) {
     83     return ParseSectionSwitch(".data", ELF::SHT_PROGBITS,
     84                               ELF::SHF_WRITE |ELF::SHF_ALLOC,
     85                               SectionKind::getDataRel());
     86   }
     87   bool ParseSectionDirectiveText(StringRef, SMLoc) {
     88     return ParseSectionSwitch(".text", ELF::SHT_PROGBITS,
     89                               ELF::SHF_EXECINSTR |
     90                               ELF::SHF_ALLOC, SectionKind::getText());
     91   }
     92   bool ParseSectionDirectiveBSS(StringRef, SMLoc) {
     93     return ParseSectionSwitch(".bss", ELF::SHT_NOBITS,
     94                               ELF::SHF_WRITE |
     95                               ELF::SHF_ALLOC, SectionKind::getBSS());
     96   }
     97   bool ParseSectionDirectiveRoData(StringRef, SMLoc) {
     98     return ParseSectionSwitch(".rodata", ELF::SHT_PROGBITS,
     99                               ELF::SHF_ALLOC,
    100                               SectionKind::getReadOnly());
    101   }
    102   bool ParseSectionDirectiveTData(StringRef, SMLoc) {
    103     return ParseSectionSwitch(".tdata", ELF::SHT_PROGBITS,
    104                               ELF::SHF_ALLOC |
    105                               ELF::SHF_TLS | ELF::SHF_WRITE,
    106                               SectionKind::getThreadData());
    107   }
    108   bool ParseSectionDirectiveTBSS(StringRef, SMLoc) {
    109     return ParseSectionSwitch(".tbss", ELF::SHT_NOBITS,
    110                               ELF::SHF_ALLOC |
    111                               ELF::SHF_TLS | ELF::SHF_WRITE,
    112                               SectionKind::getThreadBSS());
    113   }
    114   bool ParseSectionDirectiveDataRel(StringRef, SMLoc) {
    115     return ParseSectionSwitch(".data.rel", ELF::SHT_PROGBITS,
    116                               ELF::SHF_ALLOC |
    117                               ELF::SHF_WRITE,
    118                               SectionKind::getDataRel());
    119   }
    120   bool ParseSectionDirectiveDataRelRo(StringRef, SMLoc) {
    121     return ParseSectionSwitch(".data.rel.ro", ELF::SHT_PROGBITS,
    122                               ELF::SHF_ALLOC |
    123                               ELF::SHF_WRITE,
    124                               SectionKind::getReadOnlyWithRel());
    125   }
    126   bool ParseSectionDirectiveDataRelRoLocal(StringRef, SMLoc) {
    127     return ParseSectionSwitch(".data.rel.ro.local", ELF::SHT_PROGBITS,
    128                               ELF::SHF_ALLOC |
    129                               ELF::SHF_WRITE,
    130                               SectionKind::getReadOnlyWithRelLocal());
    131   }
    132   bool ParseSectionDirectiveEhFrame(StringRef, SMLoc) {
    133     return ParseSectionSwitch(".eh_frame", ELF::SHT_PROGBITS,
    134                               ELF::SHF_ALLOC |
    135                               ELF::SHF_WRITE,
    136                               SectionKind::getDataRel());
    137   }
    138   bool ParseDirectivePushSection(StringRef, SMLoc);
    139   bool ParseDirectivePopSection(StringRef, SMLoc);
    140   bool ParseDirectiveSection(StringRef, SMLoc);
    141   bool ParseDirectiveSize(StringRef, SMLoc);
    142   bool ParseDirectivePrevious(StringRef, SMLoc);
    143   bool ParseDirectiveType(StringRef, SMLoc);
    144   bool ParseDirectiveIdent(StringRef, SMLoc);
    145   bool ParseDirectiveSymver(StringRef, SMLoc);
    146   bool ParseDirectiveVersion(StringRef, SMLoc);
    147   bool ParseDirectiveWeakref(StringRef, SMLoc);
    148   bool ParseDirectiveSymbolAttribute(StringRef, SMLoc);
    149   bool ParseDirectiveSubsection(StringRef, SMLoc);
    150 
    151 private:
    152   bool ParseSectionName(StringRef &SectionName);
    153   bool ParseSectionArguments(bool IsPush, SMLoc loc);
    154   unsigned parseSunStyleSectionFlags();
    155 };
    156 
    157 }
    158 
    159 /// ParseDirectiveSymbolAttribute
    160 ///  ::= { ".local", ".weak", ... } [ identifier ( , identifier )* ]
    161 bool ELFAsmParser::ParseDirectiveSymbolAttribute(StringRef Directive, SMLoc) {
    162   MCSymbolAttr Attr = StringSwitch<MCSymbolAttr>(Directive)
    163     .Case(".weak", MCSA_Weak)
    164     .Case(".local", MCSA_Local)
    165     .Case(".hidden", MCSA_Hidden)
    166     .Case(".internal", MCSA_Internal)
    167     .Case(".protected", MCSA_Protected)
    168     .Default(MCSA_Invalid);
    169   assert(Attr != MCSA_Invalid && "unexpected symbol attribute directive!");
    170   if (getLexer().isNot(AsmToken::EndOfStatement)) {
    171     for (;;) {
    172       StringRef Name;
    173 
    174       if (getParser().parseIdentifier(Name))
    175         return TokError("expected identifier in directive");
    176 
    177       MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);
    178 
    179       getStreamer().EmitSymbolAttribute(Sym, Attr);
    180 
    181       if (getLexer().is(AsmToken::EndOfStatement))
    182         break;
    183 
    184       if (getLexer().isNot(AsmToken::Comma))
    185         return TokError("unexpected token in directive");
    186       Lex();
    187     }
    188   }
    189 
    190   Lex();
    191   return false;
    192 }
    193 
    194 bool ELFAsmParser::ParseSectionSwitch(StringRef Section, unsigned Type,
    195                                       unsigned Flags, SectionKind Kind) {
    196   const MCExpr *Subsection = nullptr;
    197   if (getLexer().isNot(AsmToken::EndOfStatement)) {
    198     if (getParser().parseExpression(Subsection))
    199       return true;
    200   }
    201 
    202   getStreamer().SwitchSection(getContext().getELFSection(Section, Type, Flags),
    203                               Subsection);
    204 
    205   return false;
    206 }
    207 
    208 bool ELFAsmParser::ParseDirectiveSize(StringRef, SMLoc) {
    209   StringRef Name;
    210   if (getParser().parseIdentifier(Name))
    211     return TokError("expected identifier in directive");
    212   MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);
    213 
    214   if (getLexer().isNot(AsmToken::Comma))
    215     return TokError("unexpected token in directive");
    216   Lex();
    217 
    218   const MCExpr *Expr;
    219   if (getParser().parseExpression(Expr))
    220     return true;
    221 
    222   if (getLexer().isNot(AsmToken::EndOfStatement))
    223     return TokError("unexpected token in directive");
    224 
    225   getStreamer().EmitELFSize(Sym, Expr);
    226   return false;
    227 }
    228 
    229 bool ELFAsmParser::ParseSectionName(StringRef &SectionName) {
    230   // A section name can contain -, so we cannot just use
    231   // parseIdentifier.
    232   SMLoc FirstLoc = getLexer().getLoc();
    233   unsigned Size = 0;
    234 
    235   if (getLexer().is(AsmToken::String)) {
    236     SectionName = getTok().getIdentifier();
    237     Lex();
    238     return false;
    239   }
    240 
    241   for (;;) {
    242     unsigned CurSize;
    243 
    244     SMLoc PrevLoc = getLexer().getLoc();
    245     if (getLexer().is(AsmToken::Minus)) {
    246       CurSize = 1;
    247       Lex(); // Consume the "-".
    248     } else if (getLexer().is(AsmToken::String)) {
    249       CurSize = getTok().getIdentifier().size() + 2;
    250       Lex();
    251     } else if (getLexer().is(AsmToken::Identifier)) {
    252       CurSize = getTok().getIdentifier().size();
    253       Lex();
    254     } else {
    255       break;
    256     }
    257 
    258     Size += CurSize;
    259     SectionName = StringRef(FirstLoc.getPointer(), Size);
    260 
    261     // Make sure the following token is adjacent.
    262     if (PrevLoc.getPointer() + CurSize != getTok().getLoc().getPointer())
    263       break;
    264   }
    265   if (Size == 0)
    266     return true;
    267 
    268   return false;
    269 }
    270 
    271 static unsigned parseSectionFlags(StringRef flagsStr, bool *UseLastGroup) {
    272   unsigned flags = 0;
    273 
    274   for (unsigned i = 0; i < flagsStr.size(); i++) {
    275     switch (flagsStr[i]) {
    276     case 'a':
    277       flags |= ELF::SHF_ALLOC;
    278       break;
    279     case 'e':
    280       flags |= ELF::SHF_EXCLUDE;
    281       break;
    282     case 'x':
    283       flags |= ELF::SHF_EXECINSTR;
    284       break;
    285     case 'w':
    286       flags |= ELF::SHF_WRITE;
    287       break;
    288     case 'M':
    289       flags |= ELF::SHF_MERGE;
    290       break;
    291     case 'S':
    292       flags |= ELF::SHF_STRINGS;
    293       break;
    294     case 'T':
    295       flags |= ELF::SHF_TLS;
    296       break;
    297     case 'c':
    298       flags |= ELF::XCORE_SHF_CP_SECTION;
    299       break;
    300     case 'd':
    301       flags |= ELF::XCORE_SHF_DP_SECTION;
    302       break;
    303     case 'G':
    304       flags |= ELF::SHF_GROUP;
    305       break;
    306     case '?':
    307       *UseLastGroup = true;
    308       break;
    309     default:
    310       return -1U;
    311     }
    312   }
    313 
    314   return flags;
    315 }
    316 
    317 unsigned ELFAsmParser::parseSunStyleSectionFlags() {
    318   unsigned flags = 0;
    319   while (getLexer().is(AsmToken::Hash)) {
    320     Lex(); // Eat the #.
    321 
    322     if (!getLexer().is(AsmToken::Identifier))
    323       return -1U;
    324 
    325     StringRef flagId = getTok().getIdentifier();
    326     if (flagId == "alloc")
    327       flags |= ELF::SHF_ALLOC;
    328     else if (flagId == "execinstr")
    329       flags |= ELF::SHF_EXECINSTR;
    330     else if (flagId == "write")
    331       flags |= ELF::SHF_WRITE;
    332     else if (flagId == "tls")
    333       flags |= ELF::SHF_TLS;
    334     else
    335       return -1U;
    336 
    337     Lex(); // Eat the flag.
    338 
    339     if (!getLexer().is(AsmToken::Comma))
    340         break;
    341     Lex(); // Eat the comma.
    342   }
    343   return flags;
    344 }
    345 
    346 
    347 bool ELFAsmParser::ParseDirectivePushSection(StringRef s, SMLoc loc) {
    348   getStreamer().PushSection();
    349 
    350   if (ParseSectionArguments(/*IsPush=*/true, loc)) {
    351     getStreamer().PopSection();
    352     return true;
    353   }
    354 
    355   return false;
    356 }
    357 
    358 bool ELFAsmParser::ParseDirectivePopSection(StringRef, SMLoc) {
    359   if (!getStreamer().PopSection())
    360     return TokError(".popsection without corresponding .pushsection");
    361   return false;
    362 }
    363 
    364 // FIXME: This is a work in progress.
    365 bool ELFAsmParser::ParseDirectiveSection(StringRef, SMLoc loc) {
    366   return ParseSectionArguments(/*IsPush=*/false, loc);
    367 }
    368 
    369 bool ELFAsmParser::ParseSectionArguments(bool IsPush, SMLoc loc) {
    370   StringRef SectionName;
    371 
    372   if (ParseSectionName(SectionName))
    373     return TokError("expected identifier in directive");
    374 
    375   StringRef TypeName;
    376   int64_t Size = 0;
    377   StringRef GroupName;
    378   unsigned Flags = 0;
    379   const MCExpr *Subsection = nullptr;
    380   bool UseLastGroup = false;
    381   StringRef UniqueStr;
    382   int64_t UniqueID = ~0;
    383 
    384   // Set the defaults first.
    385   if (SectionName == ".fini" || SectionName == ".init" ||
    386       SectionName == ".rodata")
    387     Flags |= ELF::SHF_ALLOC;
    388   if (SectionName == ".fini" || SectionName == ".init")
    389     Flags |= ELF::SHF_EXECINSTR;
    390 
    391   if (getLexer().is(AsmToken::Comma)) {
    392     Lex();
    393 
    394     if (IsPush && getLexer().isNot(AsmToken::String)) {
    395       if (getParser().parseExpression(Subsection))
    396         return true;
    397       if (getLexer().isNot(AsmToken::Comma))
    398         goto EndStmt;
    399       Lex();
    400     }
    401 
    402     unsigned extraFlags;
    403 
    404     if (getLexer().isNot(AsmToken::String)) {
    405       if (!getContext().getAsmInfo()->usesSunStyleELFSectionSwitchSyntax()
    406           || getLexer().isNot(AsmToken::Hash))
    407         return TokError("expected string in directive");
    408       extraFlags = parseSunStyleSectionFlags();
    409     } else {
    410       StringRef FlagsStr = getTok().getStringContents();
    411       Lex();
    412       extraFlags = parseSectionFlags(FlagsStr, &UseLastGroup);
    413     }
    414 
    415     if (extraFlags == -1U)
    416       return TokError("unknown flag");
    417     Flags |= extraFlags;
    418 
    419     bool Mergeable = Flags & ELF::SHF_MERGE;
    420     bool Group = Flags & ELF::SHF_GROUP;
    421     if (Group && UseLastGroup)
    422       return TokError("Section cannot specifiy a group name while also acting "
    423                       "as a member of the last group");
    424 
    425     if (getLexer().isNot(AsmToken::Comma)) {
    426       if (Mergeable)
    427         return TokError("Mergeable section must specify the type");
    428       if (Group)
    429         return TokError("Group section must specify the type");
    430     } else {
    431       Lex();
    432       if (getLexer().is(AsmToken::At) || getLexer().is(AsmToken::Percent) ||
    433           getLexer().is(AsmToken::String)) {
    434         if (!getLexer().is(AsmToken::String))
    435           Lex();
    436       } else
    437         return TokError("expected '@<type>', '%<type>' or \"<type>\"");
    438 
    439       if (getParser().parseIdentifier(TypeName))
    440         return TokError("expected identifier in directive");
    441 
    442       if (Mergeable) {
    443         if (getLexer().isNot(AsmToken::Comma))
    444           return TokError("expected the entry size");
    445         Lex();
    446         if (getParser().parseAbsoluteExpression(Size))
    447           return true;
    448         if (Size <= 0)
    449           return TokError("entry size must be positive");
    450       }
    451 
    452       if (Group) {
    453         if (getLexer().isNot(AsmToken::Comma))
    454           return TokError("expected group name");
    455         Lex();
    456         if (getParser().parseIdentifier(GroupName))
    457           return true;
    458         if (getLexer().is(AsmToken::Comma)) {
    459           Lex();
    460           StringRef Linkage;
    461           if (getParser().parseIdentifier(Linkage))
    462             return true;
    463           if (Linkage != "comdat")
    464             return TokError("Linkage must be 'comdat'");
    465         }
    466       }
    467       if (getLexer().is(AsmToken::Comma)) {
    468         Lex();
    469         if (getParser().parseIdentifier(UniqueStr))
    470           return TokError("expected identifier in directive");
    471         if (UniqueStr != "unique")
    472           return TokError("expected 'unique'");
    473         if (getLexer().isNot(AsmToken::Comma))
    474           return TokError("expected commma");
    475         Lex();
    476         if (getParser().parseAbsoluteExpression(UniqueID))
    477           return true;
    478         if (UniqueID < 0)
    479           return TokError("unique id must be positive");
    480         if (!isUInt<32>(UniqueID) || UniqueID == ~0U)
    481           return TokError("unique id is too large");
    482       }
    483     }
    484   }
    485 
    486 EndStmt:
    487   if (getLexer().isNot(AsmToken::EndOfStatement))
    488     return TokError("unexpected token in directive");
    489 
    490   unsigned Type = ELF::SHT_PROGBITS;
    491 
    492   if (TypeName.empty()) {
    493     if (SectionName.startswith(".note"))
    494       Type = ELF::SHT_NOTE;
    495     else if (SectionName == ".init_array")
    496       Type = ELF::SHT_INIT_ARRAY;
    497     else if (SectionName == ".fini_array")
    498       Type = ELF::SHT_FINI_ARRAY;
    499     else if (SectionName == ".preinit_array")
    500       Type = ELF::SHT_PREINIT_ARRAY;
    501   } else {
    502     if (TypeName == "init_array")
    503       Type = ELF::SHT_INIT_ARRAY;
    504     else if (TypeName == "fini_array")
    505       Type = ELF::SHT_FINI_ARRAY;
    506     else if (TypeName == "preinit_array")
    507       Type = ELF::SHT_PREINIT_ARRAY;
    508     else if (TypeName == "nobits")
    509       Type = ELF::SHT_NOBITS;
    510     else if (TypeName == "progbits")
    511       Type = ELF::SHT_PROGBITS;
    512     else if (TypeName == "note")
    513       Type = ELF::SHT_NOTE;
    514     else if (TypeName == "unwind")
    515       Type = ELF::SHT_X86_64_UNWIND;
    516     else
    517       return TokError("unknown section type");
    518   }
    519 
    520   if (UseLastGroup) {
    521     MCSectionSubPair CurrentSection = getStreamer().getCurrentSection();
    522     if (const MCSectionELF *Section =
    523             cast_or_null<MCSectionELF>(CurrentSection.first))
    524       if (const MCSymbol *Group = Section->getGroup()) {
    525         GroupName = Group->getName();
    526         Flags |= ELF::SHF_GROUP;
    527       }
    528   }
    529 
    530   const MCSection *ELFSection = getContext().getELFSection(
    531       SectionName, Type, Flags, Size, GroupName, UniqueID);
    532   getStreamer().SwitchSection(ELFSection, Subsection);
    533 
    534   if (getContext().getGenDwarfForAssembly()) {
    535     auto &Sections = getContext().getGenDwarfSectionSyms();
    536     auto InsertResult = Sections.insert(
    537         std::make_pair(ELFSection, std::make_pair(nullptr, nullptr)));
    538     if (InsertResult.second) {
    539       if (getContext().getDwarfVersion() <= 2)
    540         Warning(loc, "DWARF2 only supports one section per compilation unit");
    541 
    542       MCSymbol *SectionStartSymbol = getContext().CreateTempSymbol();
    543       getStreamer().EmitLabel(SectionStartSymbol);
    544       InsertResult.first->second.first = SectionStartSymbol;
    545     }
    546   }
    547 
    548   return false;
    549 }
    550 
    551 bool ELFAsmParser::ParseDirectivePrevious(StringRef DirName, SMLoc) {
    552   MCSectionSubPair PreviousSection = getStreamer().getPreviousSection();
    553   if (PreviousSection.first == nullptr)
    554       return TokError(".previous without corresponding .section");
    555   getStreamer().SwitchSection(PreviousSection.first, PreviousSection.second);
    556 
    557   return false;
    558 }
    559 
    560 static MCSymbolAttr MCAttrForString(StringRef Type) {
    561   return StringSwitch<MCSymbolAttr>(Type)
    562           .Cases("STT_FUNC", "function", MCSA_ELF_TypeFunction)
    563           .Cases("STT_OBJECT", "object", MCSA_ELF_TypeObject)
    564           .Cases("STT_TLS", "tls_object", MCSA_ELF_TypeTLS)
    565           .Cases("STT_COMMON", "common", MCSA_ELF_TypeCommon)
    566           .Cases("STT_NOTYPE", "notype", MCSA_ELF_TypeNoType)
    567           .Cases("STT_GNU_IFUNC", "gnu_indirect_function",
    568                  MCSA_ELF_TypeIndFunction)
    569           .Case("gnu_unique_object", MCSA_ELF_TypeGnuUniqueObject)
    570           .Default(MCSA_Invalid);
    571 }
    572 
    573 /// ParseDirectiveELFType
    574 ///  ::= .type identifier , STT_<TYPE_IN_UPPER_CASE>
    575 ///  ::= .type identifier , #attribute
    576 ///  ::= .type identifier , @attribute
    577 ///  ::= .type identifier , %attribute
    578 ///  ::= .type identifier , "attribute"
    579 bool ELFAsmParser::ParseDirectiveType(StringRef, SMLoc) {
    580   StringRef Name;
    581   if (getParser().parseIdentifier(Name))
    582     return TokError("expected identifier in directive");
    583 
    584   // Handle the identifier as the key symbol.
    585   MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);
    586 
    587   // NOTE the comma is optional in all cases.  It is only documented as being
    588   // optional in the first case, however, GAS will silently treat the comma as
    589   // optional in all cases.  Furthermore, although the documentation states that
    590   // the first form only accepts STT_<TYPE_IN_UPPER_CASE>, in reality, GAS
    591   // accepts both the upper case name as well as the lower case aliases.
    592   if (getLexer().is(AsmToken::Comma))
    593     Lex();
    594 
    595   if (getLexer().isNot(AsmToken::Identifier) &&
    596       getLexer().isNot(AsmToken::Hash) && getLexer().isNot(AsmToken::At) &&
    597       getLexer().isNot(AsmToken::Percent) && getLexer().isNot(AsmToken::String))
    598     return TokError("expected STT_<TYPE_IN_UPPER_CASE>, '#<type>', '@<type>', "
    599                     "'%<type>' or \"<type>\"");
    600 
    601   if (getLexer().isNot(AsmToken::String) &&
    602       getLexer().isNot(AsmToken::Identifier))
    603     Lex();
    604 
    605   SMLoc TypeLoc = getLexer().getLoc();
    606 
    607   StringRef Type;
    608   if (getParser().parseIdentifier(Type))
    609     return TokError("expected symbol type in directive");
    610 
    611   MCSymbolAttr Attr = MCAttrForString(Type);
    612   if (Attr == MCSA_Invalid)
    613     return Error(TypeLoc, "unsupported attribute in '.type' directive");
    614 
    615   if (getLexer().isNot(AsmToken::EndOfStatement))
    616     return TokError("unexpected token in '.type' directive");
    617   Lex();
    618 
    619   getStreamer().EmitSymbolAttribute(Sym, Attr);
    620 
    621   return false;
    622 }
    623 
    624 /// ParseDirectiveIdent
    625 ///  ::= .ident string
    626 bool ELFAsmParser::ParseDirectiveIdent(StringRef, SMLoc) {
    627   if (getLexer().isNot(AsmToken::String))
    628     return TokError("unexpected token in '.ident' directive");
    629 
    630   StringRef Data = getTok().getIdentifier();
    631 
    632   Lex();
    633 
    634   getStreamer().EmitIdent(Data);
    635   return false;
    636 }
    637 
    638 /// ParseDirectiveSymver
    639 ///  ::= .symver foo, bar2@zed
    640 bool ELFAsmParser::ParseDirectiveSymver(StringRef, SMLoc) {
    641   StringRef Name;
    642   if (getParser().parseIdentifier(Name))
    643     return TokError("expected identifier in directive");
    644 
    645   if (getLexer().isNot(AsmToken::Comma))
    646     return TokError("expected a comma");
    647 
    648   // ARM assembly uses @ for a comment...
    649   // except when parsing the second parameter of the .symver directive.
    650   // Force the next symbol to allow @ in the identifier, which is
    651   // required for this directive and then reset it to its initial state.
    652   const bool AllowAtInIdentifier = getLexer().getAllowAtInIdentifier();
    653   getLexer().setAllowAtInIdentifier(true);
    654   Lex();
    655   getLexer().setAllowAtInIdentifier(AllowAtInIdentifier);
    656 
    657   StringRef AliasName;
    658   if (getParser().parseIdentifier(AliasName))
    659     return TokError("expected identifier in directive");
    660 
    661   if (AliasName.find('@') == StringRef::npos)
    662     return TokError("expected a '@' in the name");
    663 
    664   MCSymbol *Alias = getContext().GetOrCreateSymbol(AliasName);
    665   MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);
    666   const MCExpr *Value = MCSymbolRefExpr::Create(Sym, getContext());
    667 
    668   getStreamer().EmitAssignment(Alias, Value);
    669   return false;
    670 }
    671 
    672 /// ParseDirectiveVersion
    673 ///  ::= .version string
    674 bool ELFAsmParser::ParseDirectiveVersion(StringRef, SMLoc) {
    675   if (getLexer().isNot(AsmToken::String))
    676     return TokError("unexpected token in '.version' directive");
    677 
    678   StringRef Data = getTok().getIdentifier();
    679 
    680   Lex();
    681 
    682   const MCSection *Note = getContext().getELFSection(".note", ELF::SHT_NOTE, 0);
    683 
    684   getStreamer().PushSection();
    685   getStreamer().SwitchSection(Note);
    686   getStreamer().EmitIntValue(Data.size()+1, 4); // namesz.
    687   getStreamer().EmitIntValue(0, 4);             // descsz = 0 (no description).
    688   getStreamer().EmitIntValue(1, 4);             // type = NT_VERSION.
    689   getStreamer().EmitBytes(Data);                // name.
    690   getStreamer().EmitIntValue(0, 1);             // terminate the string.
    691   getStreamer().EmitValueToAlignment(4);        // ensure 4 byte alignment.
    692   getStreamer().PopSection();
    693   return false;
    694 }
    695 
    696 /// ParseDirectiveWeakref
    697 ///  ::= .weakref foo, bar
    698 bool ELFAsmParser::ParseDirectiveWeakref(StringRef, SMLoc) {
    699   // FIXME: Share code with the other alias building directives.
    700 
    701   StringRef AliasName;
    702   if (getParser().parseIdentifier(AliasName))
    703     return TokError("expected identifier in directive");
    704 
    705   if (getLexer().isNot(AsmToken::Comma))
    706     return TokError("expected a comma");
    707 
    708   Lex();
    709 
    710   StringRef Name;
    711   if (getParser().parseIdentifier(Name))
    712     return TokError("expected identifier in directive");
    713 
    714   MCSymbol *Alias = getContext().GetOrCreateSymbol(AliasName);
    715 
    716   MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);
    717 
    718   getStreamer().EmitWeakReference(Alias, Sym);
    719   return false;
    720 }
    721 
    722 bool ELFAsmParser::ParseDirectiveSubsection(StringRef, SMLoc) {
    723   const MCExpr *Subsection = nullptr;
    724   if (getLexer().isNot(AsmToken::EndOfStatement)) {
    725     if (getParser().parseExpression(Subsection))
    726      return true;
    727   }
    728 
    729   if (getLexer().isNot(AsmToken::EndOfStatement))
    730     return TokError("unexpected token in directive");
    731 
    732   getStreamer().SubSection(Subsection);
    733   return false;
    734 }
    735 
    736 namespace llvm {
    737 
    738 MCAsmParserExtension *createELFAsmParser() {
    739   return new ELFAsmParser;
    740 }
    741 
    742 }
    743