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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/Support/ELF.h"
     20 using namespace llvm;
     21 
     22 namespace {
     23 
     24 class ELFAsmParser : public MCAsmParserExtension {
     25   template<bool (ELFAsmParser::*Handler)(StringRef, SMLoc)>
     26   void AddDirectiveHandler(StringRef Directive) {
     27     getParser().AddDirectiveHandler(this, Directive,
     28                                     HandleDirective<ELFAsmParser, Handler>);
     29   }
     30 
     31   bool ParseSectionSwitch(StringRef Section, unsigned Type,
     32                           unsigned Flags, SectionKind Kind);
     33   bool SeenIdent;
     34 
     35 public:
     36   ELFAsmParser() : SeenIdent(false) {
     37     BracketExpressionsSupported = true;
     38   }
     39 
     40   virtual void Initialize(MCAsmParser &Parser) {
     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::ParseDirectiveWeakref>(".weakref");
     68     AddDirectiveHandler<&ELFAsmParser::ParseDirectiveSymbolAttribute>(".weak");
     69     AddDirectiveHandler<&ELFAsmParser::ParseDirectiveSymbolAttribute>(".local");
     70     AddDirectiveHandler<
     71       &ELFAsmParser::ParseDirectiveSymbolAttribute>(".protected");
     72     AddDirectiveHandler<
     73       &ELFAsmParser::ParseDirectiveSymbolAttribute>(".internal");
     74     AddDirectiveHandler<
     75       &ELFAsmParser::ParseDirectiveSymbolAttribute>(".hidden");
     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::getDataRel());
     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 |
    115                               ELF::SHF_WRITE,
    116                               SectionKind::getDataRel());
    117   }
    118   bool ParseSectionDirectiveDataRelRo(StringRef, SMLoc) {
    119     return ParseSectionSwitch(".data.rel.ro", ELF::SHT_PROGBITS,
    120                               ELF::SHF_ALLOC |
    121                               ELF::SHF_WRITE,
    122                               SectionKind::getReadOnlyWithRel());
    123   }
    124   bool ParseSectionDirectiveDataRelRoLocal(StringRef, SMLoc) {
    125     return ParseSectionSwitch(".data.rel.ro.local", ELF::SHT_PROGBITS,
    126                               ELF::SHF_ALLOC |
    127                               ELF::SHF_WRITE,
    128                               SectionKind::getReadOnlyWithRelLocal());
    129   }
    130   bool ParseSectionDirectiveEhFrame(StringRef, SMLoc) {
    131     return ParseSectionSwitch(".eh_frame", ELF::SHT_PROGBITS,
    132                               ELF::SHF_ALLOC |
    133                               ELF::SHF_WRITE,
    134                               SectionKind::getDataRel());
    135   }
    136   bool ParseDirectivePushSection(StringRef, SMLoc);
    137   bool ParseDirectivePopSection(StringRef, SMLoc);
    138   bool ParseDirectiveSection(StringRef, SMLoc);
    139   bool ParseDirectiveSize(StringRef, SMLoc);
    140   bool ParseDirectivePrevious(StringRef, SMLoc);
    141   bool ParseDirectiveType(StringRef, SMLoc);
    142   bool ParseDirectiveIdent(StringRef, SMLoc);
    143   bool ParseDirectiveSymver(StringRef, SMLoc);
    144   bool ParseDirectiveWeakref(StringRef, SMLoc);
    145   bool ParseDirectiveSymbolAttribute(StringRef, SMLoc);
    146 
    147 private:
    148   bool ParseSectionName(StringRef &SectionName);
    149 };
    150 
    151 }
    152 
    153 /// ParseDirectiveSymbolAttribute
    154 ///  ::= { ".local", ".weak", ... } [ identifier ( , identifier )* ]
    155 bool ELFAsmParser::ParseDirectiveSymbolAttribute(StringRef Directive, SMLoc) {
    156   MCSymbolAttr Attr = StringSwitch<MCSymbolAttr>(Directive)
    157     .Case(".weak", MCSA_Weak)
    158     .Case(".local", MCSA_Local)
    159     .Case(".hidden", MCSA_Hidden)
    160     .Case(".internal", MCSA_Internal)
    161     .Case(".protected", MCSA_Protected)
    162     .Default(MCSA_Invalid);
    163   assert(Attr != MCSA_Invalid && "unexpected symbol attribute directive!");
    164   if (getLexer().isNot(AsmToken::EndOfStatement)) {
    165     for (;;) {
    166       StringRef Name;
    167 
    168       if (getParser().ParseIdentifier(Name))
    169         return TokError("expected identifier in directive");
    170 
    171       MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);
    172 
    173       getStreamer().EmitSymbolAttribute(Sym, Attr);
    174 
    175       if (getLexer().is(AsmToken::EndOfStatement))
    176         break;
    177 
    178       if (getLexer().isNot(AsmToken::Comma))
    179         return TokError("unexpected token in directive");
    180       Lex();
    181     }
    182   }
    183 
    184   Lex();
    185   return false;
    186 }
    187 
    188 bool ELFAsmParser::ParseSectionSwitch(StringRef Section, unsigned Type,
    189                                       unsigned Flags, SectionKind Kind) {
    190   if (getLexer().isNot(AsmToken::EndOfStatement))
    191     return TokError("unexpected token in section switching directive");
    192   Lex();
    193 
    194   getStreamer().SwitchSection(getContext().getELFSection(
    195                                 Section, Type, Flags, Kind));
    196 
    197   return false;
    198 }
    199 
    200 bool ELFAsmParser::ParseDirectiveSize(StringRef, SMLoc) {
    201   StringRef Name;
    202   if (getParser().ParseIdentifier(Name))
    203     return TokError("expected identifier in directive");
    204   MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);;
    205 
    206   if (getLexer().isNot(AsmToken::Comma))
    207     return TokError("unexpected token in directive");
    208   Lex();
    209 
    210   const MCExpr *Expr;
    211   if (getParser().ParseExpression(Expr))
    212     return true;
    213 
    214   if (getLexer().isNot(AsmToken::EndOfStatement))
    215     return TokError("unexpected token in directive");
    216 
    217   getStreamer().EmitELFSize(Sym, Expr);
    218   return false;
    219 }
    220 
    221 bool ELFAsmParser::ParseSectionName(StringRef &SectionName) {
    222   // A section name can contain -, so we cannot just use
    223   // ParseIdentifier.
    224   SMLoc FirstLoc = getLexer().getLoc();
    225   unsigned Size = 0;
    226 
    227   if (getLexer().is(AsmToken::String)) {
    228     SectionName = getTok().getIdentifier();
    229     Lex();
    230     return false;
    231   }
    232 
    233   for (;;) {
    234     StringRef Tmp;
    235     unsigned CurSize;
    236 
    237     SMLoc PrevLoc = getLexer().getLoc();
    238     if (getLexer().is(AsmToken::Minus)) {
    239       CurSize = 1;
    240       Lex(); // Consume the "-".
    241     } else if (getLexer().is(AsmToken::String)) {
    242       CurSize = getTok().getIdentifier().size() + 2;
    243       Lex();
    244     } else if (getLexer().is(AsmToken::Identifier)) {
    245       CurSize = getTok().getIdentifier().size();
    246       Lex();
    247     } else {
    248       break;
    249     }
    250 
    251     Size += CurSize;
    252     SectionName = StringRef(FirstLoc.getPointer(), Size);
    253 
    254     // Make sure the following token is adjacent.
    255     if (PrevLoc.getPointer() + CurSize != getTok().getLoc().getPointer())
    256       break;
    257   }
    258   if (Size == 0)
    259     return true;
    260 
    261   return false;
    262 }
    263 
    264 static SectionKind computeSectionKind(unsigned Flags) {
    265   if (Flags & ELF::SHF_EXECINSTR)
    266     return SectionKind::getText();
    267   if (Flags & ELF::SHF_TLS)
    268     return SectionKind::getThreadData();
    269   return SectionKind::getDataRel();
    270 }
    271 
    272 static int parseSectionFlags(StringRef flagsStr) {
    273   int flags = 0;
    274 
    275   for (unsigned i = 0; i < flagsStr.size(); i++) {
    276     switch (flagsStr[i]) {
    277     case 'a':
    278       flags |= ELF::SHF_ALLOC;
    279       break;
    280     case 'x':
    281       flags |= ELF::SHF_EXECINSTR;
    282       break;
    283     case 'w':
    284       flags |= ELF::SHF_WRITE;
    285       break;
    286     case 'M':
    287       flags |= ELF::SHF_MERGE;
    288       break;
    289     case 'S':
    290       flags |= ELF::SHF_STRINGS;
    291       break;
    292     case 'T':
    293       flags |= ELF::SHF_TLS;
    294       break;
    295     case 'c':
    296       flags |= ELF::XCORE_SHF_CP_SECTION;
    297       break;
    298     case 'd':
    299       flags |= ELF::XCORE_SHF_DP_SECTION;
    300       break;
    301     case 'G':
    302       flags |= ELF::SHF_GROUP;
    303       break;
    304     default:
    305       return -1;
    306     }
    307   }
    308 
    309   return flags;
    310 }
    311 
    312 bool ELFAsmParser::ParseDirectivePushSection(StringRef s, SMLoc loc) {
    313   getStreamer().PushSection();
    314 
    315   if (ParseDirectiveSection(s, loc)) {
    316     getStreamer().PopSection();
    317     return true;
    318   }
    319 
    320   return false;
    321 }
    322 
    323 bool ELFAsmParser::ParseDirectivePopSection(StringRef, SMLoc) {
    324   if (!getStreamer().PopSection())
    325     return TokError(".popsection without corresponding .pushsection");
    326   return false;
    327 }
    328 
    329 // FIXME: This is a work in progress.
    330 bool ELFAsmParser::ParseDirectiveSection(StringRef, SMLoc) {
    331   StringRef SectionName;
    332 
    333   if (ParseSectionName(SectionName))
    334     return TokError("expected identifier in directive");
    335 
    336   StringRef TypeName;
    337   int64_t Size = 0;
    338   StringRef GroupName;
    339   unsigned Flags = 0;
    340 
    341   // Set the defaults first.
    342   if (SectionName == ".fini" || SectionName == ".init" ||
    343       SectionName == ".rodata")
    344     Flags |= ELF::SHF_ALLOC;
    345   if (SectionName == ".fini" || SectionName == ".init")
    346     Flags |= ELF::SHF_EXECINSTR;
    347 
    348   if (getLexer().is(AsmToken::Comma)) {
    349     Lex();
    350 
    351     if (getLexer().isNot(AsmToken::String))
    352       return TokError("expected string in directive");
    353 
    354     StringRef FlagsStr = getTok().getStringContents();
    355     Lex();
    356 
    357     int extraFlags = parseSectionFlags(FlagsStr);
    358     if (extraFlags < 0)
    359       return TokError("unknown flag");
    360     Flags |= extraFlags;
    361 
    362     bool Mergeable = Flags & ELF::SHF_MERGE;
    363     bool Group = Flags & ELF::SHF_GROUP;
    364 
    365     if (getLexer().isNot(AsmToken::Comma)) {
    366       if (Mergeable)
    367         return TokError("Mergeable section must specify the type");
    368       if (Group)
    369         return TokError("Group section must specify the type");
    370     } else {
    371       Lex();
    372       if (getLexer().isNot(AsmToken::Percent) && getLexer().isNot(AsmToken::At))
    373         return TokError("expected '@' or '%' before type");
    374 
    375       Lex();
    376       if (getParser().ParseIdentifier(TypeName))
    377         return TokError("expected identifier in directive");
    378 
    379       if (Mergeable) {
    380         if (getLexer().isNot(AsmToken::Comma))
    381           return TokError("expected the entry size");
    382         Lex();
    383         if (getParser().ParseAbsoluteExpression(Size))
    384           return true;
    385         if (Size <= 0)
    386           return TokError("entry size must be positive");
    387       }
    388 
    389       if (Group) {
    390         if (getLexer().isNot(AsmToken::Comma))
    391           return TokError("expected group name");
    392         Lex();
    393         if (getParser().ParseIdentifier(GroupName))
    394           return true;
    395         if (getLexer().is(AsmToken::Comma)) {
    396           Lex();
    397           StringRef Linkage;
    398           if (getParser().ParseIdentifier(Linkage))
    399             return true;
    400           if (Linkage != "comdat")
    401             return TokError("Linkage must be 'comdat'");
    402         }
    403       }
    404     }
    405   }
    406 
    407   if (getLexer().isNot(AsmToken::EndOfStatement))
    408     return TokError("unexpected token in directive");
    409 
    410   unsigned Type = ELF::SHT_PROGBITS;
    411 
    412   if (!TypeName.empty()) {
    413     if (TypeName == "init_array")
    414       Type = ELF::SHT_INIT_ARRAY;
    415     else if (TypeName == "fini_array")
    416       Type = ELF::SHT_FINI_ARRAY;
    417     else if (TypeName == "preinit_array")
    418       Type = ELF::SHT_PREINIT_ARRAY;
    419     else if (TypeName == "nobits")
    420       Type = ELF::SHT_NOBITS;
    421     else if (TypeName == "progbits")
    422       Type = ELF::SHT_PROGBITS;
    423     else if (TypeName == "note")
    424       Type = ELF::SHT_NOTE;
    425     else if (TypeName == "unwind")
    426       Type = ELF::SHT_X86_64_UNWIND;
    427     else
    428       return TokError("unknown section type");
    429   }
    430 
    431   SectionKind Kind = computeSectionKind(Flags);
    432   getStreamer().SwitchSection(getContext().getELFSection(SectionName, Type,
    433                                                          Flags, Kind, Size,
    434                                                          GroupName));
    435   return false;
    436 }
    437 
    438 bool ELFAsmParser::ParseDirectivePrevious(StringRef DirName, SMLoc) {
    439   const MCSection *PreviousSection = getStreamer().getPreviousSection();
    440   if (PreviousSection == NULL)
    441       return TokError(".previous without corresponding .section");
    442   getStreamer().SwitchSection(PreviousSection);
    443 
    444   return false;
    445 }
    446 
    447 /// ParseDirectiveELFType
    448 ///  ::= .type identifier , @attribute
    449 bool ELFAsmParser::ParseDirectiveType(StringRef, SMLoc) {
    450   StringRef Name;
    451   if (getParser().ParseIdentifier(Name))
    452     return TokError("expected identifier in directive");
    453 
    454   // Handle the identifier as the key symbol.
    455   MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);
    456 
    457   if (getLexer().isNot(AsmToken::Comma))
    458     return TokError("unexpected token in '.type' directive");
    459   Lex();
    460 
    461   if (getLexer().isNot(AsmToken::Percent) && getLexer().isNot(AsmToken::At))
    462     return TokError("expected '@' or '%' before type");
    463   Lex();
    464 
    465   StringRef Type;
    466   SMLoc TypeLoc;
    467 
    468   TypeLoc = getLexer().getLoc();
    469   if (getParser().ParseIdentifier(Type))
    470     return TokError("expected symbol type in directive");
    471 
    472   MCSymbolAttr Attr = StringSwitch<MCSymbolAttr>(Type)
    473     .Case("function", MCSA_ELF_TypeFunction)
    474     .Case("object", MCSA_ELF_TypeObject)
    475     .Case("tls_object", MCSA_ELF_TypeTLS)
    476     .Case("common", MCSA_ELF_TypeCommon)
    477     .Case("notype", MCSA_ELF_TypeNoType)
    478     .Case("gnu_unique_object", MCSA_ELF_TypeGnuUniqueObject)
    479     .Default(MCSA_Invalid);
    480 
    481   if (Attr == MCSA_Invalid)
    482     return Error(TypeLoc, "unsupported attribute in '.type' directive");
    483 
    484   if (getLexer().isNot(AsmToken::EndOfStatement))
    485     return TokError("unexpected token in '.type' directive");
    486 
    487   Lex();
    488 
    489   getStreamer().EmitSymbolAttribute(Sym, Attr);
    490 
    491   return false;
    492 }
    493 
    494 /// ParseDirectiveIdent
    495 ///  ::= .ident string
    496 bool ELFAsmParser::ParseDirectiveIdent(StringRef, SMLoc) {
    497   if (getLexer().isNot(AsmToken::String))
    498     return TokError("unexpected token in '.ident' directive");
    499 
    500   StringRef Data = getTok().getIdentifier();
    501 
    502   Lex();
    503 
    504   const MCSection *Comment =
    505     getContext().getELFSection(".comment", ELF::SHT_PROGBITS,
    506                                ELF::SHF_MERGE |
    507                                ELF::SHF_STRINGS,
    508                                SectionKind::getReadOnly(),
    509                                1, "");
    510 
    511   getStreamer().PushSection();
    512   getStreamer().SwitchSection(Comment);
    513   if (!SeenIdent) {
    514     getStreamer().EmitIntValue(0, 1);
    515     SeenIdent = true;
    516   }
    517   getStreamer().EmitBytes(Data, 0);
    518   getStreamer().EmitIntValue(0, 1);
    519   getStreamer().PopSection();
    520   return false;
    521 }
    522 
    523 /// ParseDirectiveSymver
    524 ///  ::= .symver foo, bar2@zed
    525 bool ELFAsmParser::ParseDirectiveSymver(StringRef, SMLoc) {
    526   StringRef Name;
    527   if (getParser().ParseIdentifier(Name))
    528     return TokError("expected identifier in directive");
    529 
    530   if (getLexer().isNot(AsmToken::Comma))
    531     return TokError("expected a comma");
    532 
    533   Lex();
    534 
    535   StringRef AliasName;
    536   if (getParser().ParseIdentifier(AliasName))
    537     return TokError("expected identifier in directive");
    538 
    539   if (AliasName.find('@') == StringRef::npos)
    540     return TokError("expected a '@' in the name");
    541 
    542   MCSymbol *Alias = getContext().GetOrCreateSymbol(AliasName);
    543   MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);
    544   const MCExpr *Value = MCSymbolRefExpr::Create(Sym, getContext());
    545 
    546   getStreamer().EmitAssignment(Alias, Value);
    547   return false;
    548 }
    549 
    550 /// ParseDirectiveWeakref
    551 ///  ::= .weakref foo, bar
    552 bool ELFAsmParser::ParseDirectiveWeakref(StringRef, SMLoc) {
    553   // FIXME: Share code with the other alias building directives.
    554 
    555   StringRef AliasName;
    556   if (getParser().ParseIdentifier(AliasName))
    557     return TokError("expected identifier in directive");
    558 
    559   if (getLexer().isNot(AsmToken::Comma))
    560     return TokError("expected a comma");
    561 
    562   Lex();
    563 
    564   StringRef Name;
    565   if (getParser().ParseIdentifier(Name))
    566     return TokError("expected identifier in directive");
    567 
    568   MCSymbol *Alias = getContext().GetOrCreateSymbol(AliasName);
    569 
    570   MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);
    571 
    572   getStreamer().EmitWeakReference(Alias, Sym);
    573   return false;
    574 }
    575 
    576 namespace llvm {
    577 
    578 MCAsmParserExtension *createELFAsmParser() {
    579   return new ELFAsmParser;
    580 }
    581 
    582 }
    583