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