Home | History | Annotate | Download | only in MCParser 
      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   Lex();
    192 
    193   getStreamer().SwitchSection(getContext().getELFSection(Section, Type, Flags),
    194                               Subsection);
    195 
    196   return false;
    197 }
    198 
    199 bool ELFAsmParser::ParseDirectiveSize(StringRef, SMLoc) {
    200   StringRef Name;
    201   if (getParser().parseIdentifier(Name))
    202     return TokError("expected identifier in directive");
    203   MCSymbolELF *Sym = cast<MCSymbolELF>(getContext().getOrCreateSymbol(Name));
    204 
    205   if (getLexer().isNot(AsmToken::Comma))
    206     return TokError("unexpected token in directive");
    207   Lex();
    208 
    209   const MCExpr *Expr;
    210   if (getParser().parseExpression(Expr))
    211     return true;
    212 
    213   if (getLexer().isNot(AsmToken::EndOfStatement))
    214     return TokError("unexpected token in directive");
    215 
    216   getStreamer().emitELFSize(Sym, Expr);
    217   return false;
    218 }
    219 
    220 bool ELFAsmParser::ParseSectionName(StringRef &SectionName) {
    221   // A section name can contain -, so we cannot just use
    222   // parseIdentifier.
    223   SMLoc FirstLoc = getLexer().getLoc();
    224   unsigned Size = 0;
    225 
    226   if (getLexer().is(AsmToken::String)) {
    227     SectionName = getTok().getIdentifier();
    228     Lex();
    229     return false;
    230   }
    231 
    232   for (;;) {
    233 
    234     SMLoc PrevLoc = getLexer().getLoc();
    235     if (getLexer().is(AsmToken::Comma) ||
    236       getLexer().is(AsmToken::EndOfStatement))
    237       break;
    238 
    239     unsigned CurSize;
    240     if (getLexer().is(AsmToken::String)) {
    241       CurSize = getTok().getIdentifier().size() + 2;
    242       Lex();
    243     } else if (getLexer().is(AsmToken::Identifier)) {
    244       CurSize = getTok().getIdentifier().size();
    245       Lex();
    246     } else {
    247       CurSize = getTok().getString().size();
    248       Lex();
    249     }
    250     Size += CurSize;
    251     SectionName = StringRef(FirstLoc.getPointer(), Size);
    252 
    253     // Make sure the following token is adjacent.
    254     if (PrevLoc.getPointer() + CurSize != getTok().getLoc().getPointer())
    255       break;
    256   }
    257   if (Size == 0)
    258     return true;
    259 
    260   return false;
    261 }
    262 
    263 static unsigned parseSectionFlags(StringRef flagsStr, bool *UseLastGroup) {
    264   unsigned flags = 0;
    265 
    266   for (char i : flagsStr) {
    267     switch (i) {
    268     case 'a':
    269       flags |= ELF::SHF_ALLOC;
    270       break;
    271     case 'e':
    272       flags |= ELF::SHF_EXCLUDE;
    273       break;
    274     case 'x':
    275       flags |= ELF::SHF_EXECINSTR;
    276       break;
    277     case 'w':
    278       flags |= ELF::SHF_WRITE;
    279       break;
    280     case 'M':
    281       flags |= ELF::SHF_MERGE;
    282       break;
    283     case 'S':
    284       flags |= ELF::SHF_STRINGS;
    285       break;
    286     case 'T':
    287       flags |= ELF::SHF_TLS;
    288       break;
    289     case 'c':
    290       flags |= ELF::XCORE_SHF_CP_SECTION;
    291       break;
    292     case 'd':
    293       flags |= ELF::XCORE_SHF_DP_SECTION;
    294       break;
    295     case 'G':
    296       flags |= ELF::SHF_GROUP;
    297       break;
    298     case '?':
    299       *UseLastGroup = true;
    300       break;
    301     default:
    302       return -1U;
    303     }
    304   }
    305 
    306   return flags;
    307 }
    308 
    309 unsigned ELFAsmParser::parseSunStyleSectionFlags() {
    310   unsigned flags = 0;
    311   while (getLexer().is(AsmToken::Hash)) {
    312     Lex(); // Eat the #.
    313 
    314     if (!getLexer().is(AsmToken::Identifier))
    315       return -1U;
    316 
    317     StringRef flagId = getTok().getIdentifier();
    318     if (flagId == "alloc")
    319       flags |= ELF::SHF_ALLOC;
    320     else if (flagId == "execinstr")
    321       flags |= ELF::SHF_EXECINSTR;
    322     else if (flagId == "write")
    323       flags |= ELF::SHF_WRITE;
    324     else if (flagId == "tls")
    325       flags |= ELF::SHF_TLS;
    326     else
    327       return -1U;
    328 
    329     Lex(); // Eat the flag.
    330 
    331     if (!getLexer().is(AsmToken::Comma))
    332         break;
    333     Lex(); // Eat the comma.
    334   }
    335   return flags;
    336 }
    337 
    338 
    339 bool ELFAsmParser::ParseDirectivePushSection(StringRef s, SMLoc loc) {
    340   getStreamer().PushSection();
    341 
    342   if (ParseSectionArguments(/*IsPush=*/true, loc)) {
    343     getStreamer().PopSection();
    344     return true;
    345   }
    346 
    347   return false;
    348 }
    349 
    350 bool ELFAsmParser::ParseDirectivePopSection(StringRef, SMLoc) {
    351   if (!getStreamer().PopSection())
    352     return TokError(".popsection without corresponding .pushsection");
    353   return false;
    354 }
    355 
    356 // FIXME: This is a work in progress.
    357 bool ELFAsmParser::ParseDirectiveSection(StringRef, SMLoc loc) {
    358   return ParseSectionArguments(/*IsPush=*/false, loc);
    359 }
    360 
    361 bool ELFAsmParser::ParseSectionArguments(bool IsPush, SMLoc loc) {
    362   StringRef SectionName;
    363 
    364   if (ParseSectionName(SectionName))
    365     return TokError("expected identifier in directive");
    366 
    367   StringRef TypeName;
    368   int64_t Size = 0;
    369   StringRef GroupName;
    370   unsigned Flags = 0;
    371   const MCExpr *Subsection = nullptr;
    372   bool UseLastGroup = false;
    373   StringRef UniqueStr;
    374   int64_t UniqueID = ~0;
    375 
    376   // Set the defaults first.
    377   if (SectionName == ".fini" || SectionName == ".init" ||
    378       SectionName == ".rodata")
    379     Flags |= ELF::SHF_ALLOC;
    380   if (SectionName == ".fini" || SectionName == ".init")
    381     Flags |= ELF::SHF_EXECINSTR;
    382 
    383   if (getLexer().is(AsmToken::Comma)) {
    384     Lex();
    385 
    386     if (IsPush && getLexer().isNot(AsmToken::String)) {
    387       if (getParser().parseExpression(Subsection))
    388         return true;
    389       if (getLexer().isNot(AsmToken::Comma))
    390         goto EndStmt;
    391       Lex();
    392     }
    393 
    394     unsigned extraFlags;
    395 
    396     if (getLexer().isNot(AsmToken::String)) {
    397       if (!getContext().getAsmInfo()->usesSunStyleELFSectionSwitchSyntax()
    398           || getLexer().isNot(AsmToken::Hash))
    399         return TokError("expected string in directive");
    400       extraFlags = parseSunStyleSectionFlags();
    401     } else {
    402       StringRef FlagsStr = getTok().getStringContents();
    403       Lex();
    404       extraFlags = parseSectionFlags(FlagsStr, &UseLastGroup);
    405     }
    406 
    407     if (extraFlags == -1U)
    408       return TokError("unknown flag");
    409     Flags |= extraFlags;
    410 
    411     bool Mergeable = Flags & ELF::SHF_MERGE;
    412     bool Group = Flags & ELF::SHF_GROUP;
    413     if (Group && UseLastGroup)
    414       return TokError("Section cannot specifiy a group name while also acting "
    415                       "as a member of the last group");
    416 
    417     if (getLexer().isNot(AsmToken::Comma)) {
    418       if (Mergeable)
    419         return TokError("Mergeable section must specify the type");
    420       if (Group)
    421         return TokError("Group section must specify the type");
    422     } else {
    423       Lex();
    424       if (getLexer().is(AsmToken::At) || getLexer().is(AsmToken::Percent) ||
    425           getLexer().is(AsmToken::String)) {
    426         if (!getLexer().is(AsmToken::String))
    427           Lex();
    428       } else
    429         return TokError("expected '@<type>', '%<type>' or \"<type>\"");
    430 
    431       if (getParser().parseIdentifier(TypeName))
    432         return TokError("expected identifier in directive");
    433 
    434       if (Mergeable) {
    435         if (getLexer().isNot(AsmToken::Comma))
    436           return TokError("expected the entry size");
    437         Lex();
    438         if (getParser().parseAbsoluteExpression(Size))
    439           return true;
    440         if (Size <= 0)
    441           return TokError("entry size must be positive");
    442       }
    443 
    444       if (Group) {
    445         if (getLexer().isNot(AsmToken::Comma))
    446           return TokError("expected group name");
    447         Lex();
    448         if (getParser().parseIdentifier(GroupName))
    449           return true;
    450         if (getLexer().is(AsmToken::Comma)) {
    451           Lex();
    452           StringRef Linkage;
    453           if (getParser().parseIdentifier(Linkage))
    454             return true;
    455           if (Linkage != "comdat")
    456             return TokError("Linkage must be 'comdat'");
    457         }
    458       }
    459       if (getLexer().is(AsmToken::Comma)) {
    460         Lex();
    461         if (getParser().parseIdentifier(UniqueStr))
    462           return TokError("expected identifier in directive");
    463         if (UniqueStr != "unique")
    464           return TokError("expected 'unique'");
    465         if (getLexer().isNot(AsmToken::Comma))
    466           return TokError("expected commma");
    467         Lex();
    468         if (getParser().parseAbsoluteExpression(UniqueID))
    469           return true;
    470         if (UniqueID < 0)
    471           return TokError("unique id must be positive");
    472         if (!isUInt<32>(UniqueID) || UniqueID == ~0U)
    473           return TokError("unique id is too large");
    474       }
    475     }
    476   }
    477 
    478 EndStmt:
    479   if (getLexer().isNot(AsmToken::EndOfStatement))
    480     return TokError("unexpected token in directive");
    481 
    482   unsigned Type = ELF::SHT_PROGBITS;
    483 
    484   if (TypeName.empty()) {
    485     if (SectionName.startswith(".note"))
    486       Type = ELF::SHT_NOTE;
    487     else if (SectionName == ".init_array")
    488       Type = ELF::SHT_INIT_ARRAY;
    489     else if (SectionName == ".fini_array")
    490       Type = ELF::SHT_FINI_ARRAY;
    491     else if (SectionName == ".preinit_array")
    492       Type = ELF::SHT_PREINIT_ARRAY;
    493   } else {
    494     if (TypeName == "init_array")
    495       Type = ELF::SHT_INIT_ARRAY;
    496     else if (TypeName == "fini_array")
    497       Type = ELF::SHT_FINI_ARRAY;
    498     else if (TypeName == "preinit_array")
    499       Type = ELF::SHT_PREINIT_ARRAY;
    500     else if (TypeName == "nobits")
    501       Type = ELF::SHT_NOBITS;
    502     else if (TypeName == "progbits")
    503       Type = ELF::SHT_PROGBITS;
    504     else if (TypeName == "note")
    505       Type = ELF::SHT_NOTE;
    506     else if (TypeName == "unwind")
    507       Type = ELF::SHT_X86_64_UNWIND;
    508     else
    509       return TokError("unknown section type");
    510   }
    511 
    512   if (UseLastGroup) {
    513     MCSectionSubPair CurrentSection = getStreamer().getCurrentSection();
    514     if (const MCSectionELF *Section =
    515             cast_or_null<MCSectionELF>(CurrentSection.first))
    516       if (const MCSymbol *Group = Section->getGroup()) {
    517         GroupName = Group->getName();
    518         Flags |= ELF::SHF_GROUP;
    519       }
    520   }
    521 
    522   MCSection *ELFSection = getContext().getELFSection(SectionName, Type, Flags,
    523                                                      Size, GroupName, UniqueID);
    524   getStreamer().SwitchSection(ELFSection, Subsection);
    525 
    526   if (getContext().getGenDwarfForAssembly()) {
    527     bool InsertResult = getContext().addGenDwarfSection(ELFSection);
    528     if (InsertResult) {
    529       if (getContext().getDwarfVersion() <= 2)
    530         Warning(loc, "DWARF2 only supports one section per compilation unit");
    531 
    532       if (!ELFSection->getBeginSymbol()) {
    533         MCSymbol *SectionStartSymbol = getContext().createTempSymbol();
    534         getStreamer().EmitLabel(SectionStartSymbol);
    535         ELFSection->setBeginSymbol(SectionStartSymbol);
    536       }
    537     }
    538   }
    539 
    540   return false;
    541 }
    542 
    543 bool ELFAsmParser::ParseDirectivePrevious(StringRef DirName, SMLoc) {
    544   MCSectionSubPair PreviousSection = getStreamer().getPreviousSection();
    545   if (PreviousSection.first == nullptr)
    546       return TokError(".previous without corresponding .section");
    547   getStreamer().SwitchSection(PreviousSection.first, PreviousSection.second);
    548 
    549   return false;
    550 }
    551 
    552 static MCSymbolAttr MCAttrForString(StringRef Type) {
    553   return StringSwitch<MCSymbolAttr>(Type)
    554           .Cases("STT_FUNC", "function", MCSA_ELF_TypeFunction)
    555           .Cases("STT_OBJECT", "object", MCSA_ELF_TypeObject)
    556           .Cases("STT_TLS", "tls_object", MCSA_ELF_TypeTLS)
    557           .Cases("STT_COMMON", "common", MCSA_ELF_TypeCommon)
    558           .Cases("STT_NOTYPE", "notype", MCSA_ELF_TypeNoType)
    559           .Cases("STT_GNU_IFUNC", "gnu_indirect_function",
    560                  MCSA_ELF_TypeIndFunction)
    561           .Case("gnu_unique_object", MCSA_ELF_TypeGnuUniqueObject)
    562           .Default(MCSA_Invalid);
    563 }
    564 
    565 /// ParseDirectiveELFType
    566 ///  ::= .type identifier , STT_<TYPE_IN_UPPER_CASE>
    567 ///  ::= .type identifier , #attribute
    568 ///  ::= .type identifier , @attribute
    569 ///  ::= .type identifier , %attribute
    570 ///  ::= .type identifier , "attribute"
    571 bool ELFAsmParser::ParseDirectiveType(StringRef, SMLoc) {
    572   StringRef Name;
    573   if (getParser().parseIdentifier(Name))
    574     return TokError("expected identifier in directive");
    575 
    576   // Handle the identifier as the key symbol.
    577   MCSymbol *Sym = getContext().getOrCreateSymbol(Name);
    578 
    579   // NOTE the comma is optional in all cases.  It is only documented as being
    580   // optional in the first case, however, GAS will silently treat the comma as
    581   // optional in all cases.  Furthermore, although the documentation states that
    582   // the first form only accepts STT_<TYPE_IN_UPPER_CASE>, in reality, GAS
    583   // accepts both the upper case name as well as the lower case aliases.
    584   if (getLexer().is(AsmToken::Comma))
    585     Lex();
    586 
    587   if (getLexer().isNot(AsmToken::Identifier) &&
    588       getLexer().isNot(AsmToken::Hash) &&
    589       getLexer().isNot(AsmToken::Percent) &&
    590       getLexer().isNot(AsmToken::String)) {
    591     if (!getLexer().getAllowAtInIdentifier())
    592       return TokError("expected STT_<TYPE_IN_UPPER_CASE>, '#<type>', "
    593                       "'%<type>' or \"<type>\"");
    594     else if (getLexer().isNot(AsmToken::At))
    595       return TokError("expected STT_<TYPE_IN_UPPER_CASE>, '#<type>', '@<type>', "
    596                       "'%<type>' or \"<type>\"");
    597   }
    598 
    599   if (getLexer().isNot(AsmToken::String) &&
    600       getLexer().isNot(AsmToken::Identifier))
    601     Lex();
    602 
    603   SMLoc TypeLoc = getLexer().getLoc();
    604 
    605   StringRef Type;
    606   if (getParser().parseIdentifier(Type))
    607     return TokError("expected symbol type in directive");
    608 
    609   MCSymbolAttr Attr = MCAttrForString(Type);
    610   if (Attr == MCSA_Invalid)
    611     return Error(TypeLoc, "unsupported attribute in '.type' directive");
    612 
    613   if (getLexer().isNot(AsmToken::EndOfStatement))
    614     return TokError("unexpected token in '.type' directive");
    615   Lex();
    616 
    617   getStreamer().EmitSymbolAttribute(Sym, Attr);
    618 
    619   return false;
    620 }
    621 
    622 /// ParseDirectiveIdent
    623 ///  ::= .ident string
    624 bool ELFAsmParser::ParseDirectiveIdent(StringRef, SMLoc) {
    625   if (getLexer().isNot(AsmToken::String))
    626     return TokError("unexpected token in '.ident' directive");
    627 
    628   StringRef Data = getTok().getIdentifier();
    629 
    630   Lex();
    631 
    632   getStreamer().EmitIdent(Data);
    633   return false;
    634 }
    635 
    636 /// ParseDirectiveSymver
    637 ///  ::= .symver foo, bar2@zed
    638 bool ELFAsmParser::ParseDirectiveSymver(StringRef, SMLoc) {
    639   StringRef Name;
    640   if (getParser().parseIdentifier(Name))
    641     return TokError("expected identifier in directive");
    642 
    643   if (getLexer().isNot(AsmToken::Comma))
    644     return TokError("expected a comma");
    645 
    646   // ARM assembly uses @ for a comment...
    647   // except when parsing the second parameter of the .symver directive.
    648   // Force the next symbol to allow @ in the identifier, which is
    649   // required for this directive and then reset it to its initial state.
    650   const bool AllowAtInIdentifier = getLexer().getAllowAtInIdentifier();
    651   getLexer().setAllowAtInIdentifier(true);
    652   Lex();
    653   getLexer().setAllowAtInIdentifier(AllowAtInIdentifier);
    654 
    655   StringRef AliasName;
    656   if (getParser().parseIdentifier(AliasName))
    657     return TokError("expected identifier in directive");
    658 
    659   if (AliasName.find('@') == StringRef::npos)
    660     return TokError("expected a '@' in the name");
    661 
    662   MCSymbol *Alias = getContext().getOrCreateSymbol(AliasName);
    663   MCSymbol *Sym = getContext().getOrCreateSymbol(Name);
    664   const MCExpr *Value = MCSymbolRefExpr::create(Sym, getContext());
    665 
    666   getStreamer().EmitAssignment(Alias, Value);
    667   return false;
    668 }
    669 
    670 /// ParseDirectiveVersion
    671 ///  ::= .version string
    672 bool ELFAsmParser::ParseDirectiveVersion(StringRef, SMLoc) {
    673   if (getLexer().isNot(AsmToken::String))
    674     return TokError("unexpected token in '.version' directive");
    675 
    676   StringRef Data = getTok().getIdentifier();
    677 
    678   Lex();
    679 
    680   MCSection *Note = getContext().getELFSection(".note", ELF::SHT_NOTE, 0);
    681 
    682   getStreamer().PushSection();
    683   getStreamer().SwitchSection(Note);
    684   getStreamer().EmitIntValue(Data.size()+1, 4); // namesz.
    685   getStreamer().EmitIntValue(0, 4);             // descsz = 0 (no description).
    686   getStreamer().EmitIntValue(1, 4);             // type = NT_VERSION.
    687   getStreamer().EmitBytes(Data);                // name.
    688   getStreamer().EmitIntValue(0, 1);             // terminate the string.
    689   getStreamer().EmitValueToAlignment(4);        // ensure 4 byte alignment.
    690   getStreamer().PopSection();
    691   return false;
    692 }
    693 
    694 /// ParseDirectiveWeakref
    695 ///  ::= .weakref foo, bar
    696 bool ELFAsmParser::ParseDirectiveWeakref(StringRef, SMLoc) {
    697   // FIXME: Share code with the other alias building directives.
    698 
    699   StringRef AliasName;
    700   if (getParser().parseIdentifier(AliasName))
    701     return TokError("expected identifier in directive");
    702 
    703   if (getLexer().isNot(AsmToken::Comma))
    704     return TokError("expected a comma");
    705 
    706   Lex();
    707 
    708   StringRef Name;
    709   if (getParser().parseIdentifier(Name))
    710     return TokError("expected identifier in directive");
    711 
    712   MCSymbol *Alias = getContext().getOrCreateSymbol(AliasName);
    713 
    714   MCSymbol *Sym = getContext().getOrCreateSymbol(Name);
    715 
    716   getStreamer().EmitWeakReference(Alias, Sym);
    717   return false;
    718 }
    719 
    720 bool ELFAsmParser::ParseDirectiveSubsection(StringRef, SMLoc) {
    721   const MCExpr *Subsection = nullptr;
    722   if (getLexer().isNot(AsmToken::EndOfStatement)) {
    723     if (getParser().parseExpression(Subsection))
    724      return true;
    725   }
    726 
    727   if (getLexer().isNot(AsmToken::EndOfStatement))
    728     return TokError("unexpected token in directive");
    729 
    730   getStreamer().SubSection(Subsection);
    731   return false;
    732 }
    733 
    734 namespace llvm {
    735 
    736 MCAsmParserExtension *createELFAsmParser() {
    737   return new ELFAsmParser;
    738 }
    739 
    740 }
    741