lib/MC/MCParser/ELFAsmParser.cpp

//===- ELFAsmParser.cpp - ELF Assembly Parser -----------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "llvm/MC/MCParser/MCAsmParserExtension.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCParser/MCAsmLexer.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/Support/ELF.h"
using namespace llvm;

namespace {

class ELFAsmParser : public MCAsmParserExtension {
  template<bool (ELFAsmParser::*Handler)(StringRef, SMLoc)>
  void AddDirectiveHandler(StringRef Directive) {
    getParser().AddDirectiveHandler(this, Directive,
                                    HandleDirective<ELFAsmParser, Handler>);
  }

  bool ParseSectionSwitch(StringRef Section, unsigned Type,
                          unsigned Flags, SectionKind Kind);
  bool SeenIdent;

public:
  ELFAsmParser() : SeenIdent(false) {
    BracketExpressionsSupported = true;
  }

  virtual void Initialize(MCAsmParser &Parser) {
    // Call the base implementation.
    this->MCAsmParserExtension::Initialize(Parser);

    AddDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveData>(".data");
    AddDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveText>(".text");
    AddDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveBSS>(".bss");
    AddDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveRoData>(".rodata");
    AddDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveTData>(".tdata");
    AddDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveTBSS>(".tbss");
    AddDirectiveHandler<
      &ELFAsmParser::ParseSectionDirectiveDataRel>(".data.rel");
    AddDirectiveHandler<
      &ELFAsmParser::ParseSectionDirectiveDataRelRo>(".data.rel.ro");
    AddDirectiveHandler<
      &ELFAsmParser::ParseSectionDirectiveDataRelRoLocal>(".data.rel.ro.local");
    AddDirectiveHandler<
      &ELFAsmParser::ParseSectionDirectiveEhFrame>(".eh_frame");
    AddDirectiveHandler<&ELFAsmParser::ParseDirectiveSection>(".section");
    AddDirectiveHandler<
      &ELFAsmParser::ParseDirectivePushSection>(".pushsection");
    AddDirectiveHandler<&ELFAsmParser::ParseDirectivePopSection>(".popsection");
    AddDirectiveHandler<&ELFAsmParser::ParseDirectiveSize>(".size");
    AddDirectiveHandler<&ELFAsmParser::ParseDirectivePrevious>(".previous");
    AddDirectiveHandler<&ELFAsmParser::ParseDirectiveType>(".type");
    AddDirectiveHandler<&ELFAsmParser::ParseDirectiveIdent>(".ident");
    AddDirectiveHandler<&ELFAsmParser::ParseDirectiveSymver>(".symver");
    AddDirectiveHandler<&ELFAsmParser::ParseDirectiveWeakref>(".weakref");
  }

  // FIXME: Part of this logic is duplicated in the MCELFStreamer. What is
  // the best way for us to get access to it?
  bool ParseSectionDirectiveData(StringRef, SMLoc) {
    return ParseSectionSwitch(".data", ELF::SHT_PROGBITS,
                              ELF::SHF_WRITE |ELF::SHF_ALLOC,
                              SectionKind::getDataRel());
  }
  bool ParseSectionDirectiveText(StringRef, SMLoc) {
    return ParseSectionSwitch(".text", ELF::SHT_PROGBITS,
                              ELF::SHF_EXECINSTR |
                              ELF::SHF_ALLOC, SectionKind::getText());
  }
  bool ParseSectionDirectiveBSS(StringRef, SMLoc) {
    return ParseSectionSwitch(".bss", ELF::SHT_NOBITS,
                              ELF::SHF_WRITE |
                              ELF::SHF_ALLOC, SectionKind::getBSS());
  }
  bool ParseSectionDirectiveRoData(StringRef, SMLoc) {
    return ParseSectionSwitch(".rodata", ELF::SHT_PROGBITS,
                              ELF::SHF_ALLOC,
                              SectionKind::getReadOnly());
  }
  bool ParseSectionDirectiveTData(StringRef, SMLoc) {
    return ParseSectionSwitch(".tdata", ELF::SHT_PROGBITS,
                              ELF::SHF_ALLOC |
                              ELF::SHF_TLS | ELF::SHF_WRITE,
                              SectionKind::getThreadData());
  }
  bool ParseSectionDirectiveTBSS(StringRef, SMLoc) {
    return ParseSectionSwitch(".tbss", ELF::SHT_NOBITS,
                              ELF::SHF_ALLOC |
                              ELF::SHF_TLS | ELF::SHF_WRITE,
                              SectionKind::getThreadBSS());
  }
  bool ParseSectionDirectiveDataRel(StringRef, SMLoc) {
    return ParseSectionSwitch(".data.rel", ELF::SHT_PROGBITS,
                              ELF::SHF_ALLOC |
                              ELF::SHF_WRITE,
                              SectionKind::getDataRel());
  }
  bool ParseSectionDirectiveDataRelRo(StringRef, SMLoc) {
    return ParseSectionSwitch(".data.rel.ro", ELF::SHT_PROGBITS,
                              ELF::SHF_ALLOC |
                              ELF::SHF_WRITE,
                              SectionKind::getReadOnlyWithRel());
  }
  bool ParseSectionDirectiveDataRelRoLocal(StringRef, SMLoc) {
    return ParseSectionSwitch(".data.rel.ro.local", ELF::SHT_PROGBITS,
                              ELF::SHF_ALLOC |
                              ELF::SHF_WRITE,
                              SectionKind::getReadOnlyWithRelLocal());
  }
  bool ParseSectionDirectiveEhFrame(StringRef, SMLoc) {
    return ParseSectionSwitch(".eh_frame", ELF::SHT_PROGBITS,
                              ELF::SHF_ALLOC |
                              ELF::SHF_WRITE,
                              SectionKind::getDataRel());
  }
  bool ParseDirectivePushSection(StringRef, SMLoc);
  bool ParseDirectivePopSection(StringRef, SMLoc);
  bool ParseDirectiveSection(StringRef, SMLoc);
  bool ParseDirectiveSize(StringRef, SMLoc);
  bool ParseDirectivePrevious(StringRef, SMLoc);
  bool ParseDirectiveType(StringRef, SMLoc);
  bool ParseDirectiveIdent(StringRef, SMLoc);
  bool ParseDirectiveSymver(StringRef, SMLoc);
  bool ParseDirectiveWeakref(StringRef, SMLoc);

private:
  bool ParseSectionName(StringRef &SectionName);
};

}

bool ELFAsmParser::ParseSectionSwitch(StringRef Section, unsigned Type,
                                      unsigned Flags, SectionKind Kind) {
  if (getLexer().isNot(AsmToken::EndOfStatement))
    return TokError("unexpected token in section switching directive");
  Lex();

  getStreamer().SwitchSection(getContext().getELFSection(
                                Section, Type, Flags, Kind));

  return false;
}

bool ELFAsmParser::ParseDirectiveSize(StringRef, SMLoc) {
  StringRef Name;
  if (getParser().ParseIdentifier(Name))
    return TokError("expected identifier in directive");
  MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);;

  if (getLexer().isNot(AsmToken::Comma))
    return TokError("unexpected token in directive");
  Lex();

  const MCExpr *Expr;
  if (getParser().ParseExpression(Expr))
    return true;

  if (getLexer().isNot(AsmToken::EndOfStatement))
    return TokError("unexpected token in directive");

  getStreamer().EmitELFSize(Sym, Expr);
  return false;
}

bool ELFAsmParser::ParseSectionName(StringRef &SectionName) {
  // A section name can contain -, so we cannot just use
  // ParseIdentifier.
  SMLoc FirstLoc = getLexer().getLoc();
  unsigned Size = 0;

  if (getLexer().is(AsmToken::String)) {
    SectionName = getTok().getIdentifier();
    Lex();
    return false;
  }

  for (;;) {
    StringRef Tmp;
    unsigned CurSize;

    SMLoc PrevLoc = getLexer().getLoc();
    if (getLexer().is(AsmToken::Minus)) {
      CurSize = 1;
      Lex(); // Consume the "-".
    } else if (getLexer().is(AsmToken::String)) {
      CurSize = getTok().getIdentifier().size() + 2;
      Lex();
    } else if (getLexer().is(AsmToken::Identifier)) {
      CurSize = getTok().getIdentifier().size();
      Lex();
    } else {
      break;
    }

    Size += CurSize;
    SectionName = StringRef(FirstLoc.getPointer(), Size);

    // Make sure the following token is adjacent.
    if (PrevLoc.getPointer() + CurSize != getTok().getLoc().getPointer())
      break;
  }
  if (Size == 0)
    return true;

  return false;
}

static SectionKind computeSectionKind(unsigned Flags) {
  if (Flags & ELF::SHF_EXECINSTR)
    return SectionKind::getText();
  if (Flags & ELF::SHF_TLS)
    return SectionKind::getThreadData();
  return SectionKind::getDataRel();
}

static int parseSectionFlags(StringRef flagsStr) {
  int flags = 0;

  for (unsigned i = 0; i < flagsStr.size(); i++) {
    switch (flagsStr[i]) {
    case 'a':
      flags |= ELF::SHF_ALLOC;
      break;
    case 'x':
      flags |= ELF::SHF_EXECINSTR;
      break;
    case 'w':
      flags |= ELF::SHF_WRITE;
      break;
    case 'M':
      flags |= ELF::SHF_MERGE;
      break;
    case 'S':
      flags |= ELF::SHF_STRINGS;
      break;
    case 'T':
      flags |= ELF::SHF_TLS;
      break;
    case 'c':
      flags |= ELF::XCORE_SHF_CP_SECTION;
      break;
    case 'd':
      flags |= ELF::XCORE_SHF_DP_SECTION;
      break;
    case 'G':
      flags |= ELF::SHF_GROUP;
      break;
    default:
      return -1;
    }
  }

  return flags;
}

bool ELFAsmParser::ParseDirectivePushSection(StringRef s, SMLoc loc) {
  getStreamer().PushSection();

  if (ParseDirectiveSection(s, loc)) {
    getStreamer().PopSection();
    return true;
  }

  return false;
}

bool ELFAsmParser::ParseDirectivePopSection(StringRef, SMLoc) {
  if (!getStreamer().PopSection())
    return TokError(".popsection without corresponding .pushsection");
  return false;
}

// FIXME: This is a work in progress.
bool ELFAsmParser::ParseDirectiveSection(StringRef, SMLoc) {
  StringRef SectionName;

  if (ParseSectionName(SectionName))
    return TokError("expected identifier in directive");

  StringRef TypeName;
  int64_t Size = 0;
  StringRef GroupName;
  unsigned Flags = 0;

  // Set the defaults first.
  if (SectionName == ".fini" || SectionName == ".init" ||
      SectionName == ".rodata")
    Flags |= ELF::SHF_ALLOC;
  if (SectionName == ".fini" || SectionName == ".init")
    Flags |= ELF::SHF_EXECINSTR;

  if (getLexer().is(AsmToken::Comma)) {
    Lex();

    if (getLexer().isNot(AsmToken::String))
      return TokError("expected string in directive");

    StringRef FlagsStr = getTok().getStringContents();
    Lex();

    int extraFlags = parseSectionFlags(FlagsStr);
    if (extraFlags < 0)
      return TokError("unknown flag");
    Flags |= extraFlags;

    bool Mergeable = Flags & ELF::SHF_MERGE;
    bool Group = Flags & ELF::SHF_GROUP;

    if (getLexer().isNot(AsmToken::Comma)) {
      if (Mergeable)
        return TokError("Mergeable section must specify the type");
      if (Group)
        return TokError("Group section must specify the type");
    } else {
      Lex();
      if (getLexer().isNot(AsmToken::Percent) && getLexer().isNot(AsmToken::At))
        return TokError("expected '@' or '%' before type");

      Lex();
      if (getParser().ParseIdentifier(TypeName))
        return TokError("expected identifier in directive");

      if (Mergeable) {
        if (getLexer().isNot(AsmToken::Comma))
          return TokError("expected the entry size");
        Lex();
        if (getParser().ParseAbsoluteExpression(Size))
          return true;
        if (Size <= 0)
          return TokError("entry size must be positive");
      }

      if (Group) {
        if (getLexer().isNot(AsmToken::Comma))
          return TokError("expected group name");
        Lex();
        if (getParser().ParseIdentifier(GroupName))
          return true;
        if (getLexer().is(AsmToken::Comma)) {
          Lex();
          StringRef Linkage;
          if (getParser().ParseIdentifier(Linkage))
            return true;
          if (Linkage != "comdat")
            return TokError("Linkage must be 'comdat'");
        }
      }
    }
  }

  if (getLexer().isNot(AsmToken::EndOfStatement))
    return TokError("unexpected token in directive");

  unsigned Type = ELF::SHT_PROGBITS;

  if (!TypeName.empty()) {
    if (TypeName == "init_array")
      Type = ELF::SHT_INIT_ARRAY;
    else if (TypeName == "fini_array")
      Type = ELF::SHT_FINI_ARRAY;
    else if (TypeName == "preinit_array")
      Type = ELF::SHT_PREINIT_ARRAY;
    else if (TypeName == "nobits")
      Type = ELF::SHT_NOBITS;
    else if (TypeName == "progbits")
      Type = ELF::SHT_PROGBITS;
    else if (TypeName == "note")
      Type = ELF::SHT_NOTE;
    else if (TypeName == "unwind")
      Type = ELF::SHT_X86_64_UNWIND;
    else
      return TokError("unknown section type");
  }

  SectionKind Kind = computeSectionKind(Flags);
  getStreamer().SwitchSection(getContext().getELFSection(SectionName, Type,
                                                         Flags, Kind, Size,
                                                         GroupName));
  return false;
}

bool ELFAsmParser::ParseDirectivePrevious(StringRef DirName, SMLoc) {
  const MCSection *PreviousSection = getStreamer().getPreviousSection();
  if (PreviousSection == NULL)
      return TokError(".previous without corresponding .section");
  getStreamer().SwitchSection(PreviousSection);

  return false;
}

/// ParseDirectiveELFType
///  ::= .type identifier , @attribute
bool ELFAsmParser::ParseDirectiveType(StringRef, SMLoc) {
  StringRef Name;
  if (getParser().ParseIdentifier(Name))
    return TokError("expected identifier in directive");

  // Handle the identifier as the key symbol.
  MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);

  if (getLexer().isNot(AsmToken::Comma))
    return TokError("unexpected token in '.type' directive");
  Lex();

  if (getLexer().isNot(AsmToken::Percent) && getLexer().isNot(AsmToken::At))
    return TokError("expected '@' or '%' before type");
  Lex();

  StringRef Type;
  SMLoc TypeLoc;

  TypeLoc = getLexer().getLoc();
  if (getParser().ParseIdentifier(Type))
    return TokError("expected symbol type in directive");

  MCSymbolAttr Attr = StringSwitch<MCSymbolAttr>(Type)
    .Case("function", MCSA_ELF_TypeFunction)
    .Case("object", MCSA_ELF_TypeObject)
    .Case("tls_object", MCSA_ELF_TypeTLS)
    .Case("common", MCSA_ELF_TypeCommon)
    .Case("notype", MCSA_ELF_TypeNoType)
    .Case("gnu_unique_object", MCSA_ELF_TypeGnuUniqueObject)
    .Default(MCSA_Invalid);

  if (Attr == MCSA_Invalid)
    return Error(TypeLoc, "unsupported attribute in '.type' directive");

  if (getLexer().isNot(AsmToken::EndOfStatement))
    return TokError("unexpected token in '.type' directive");

  Lex();

  getStreamer().EmitSymbolAttribute(Sym, Attr);

  return false;
}

/// ParseDirectiveIdent
///  ::= .ident string
bool ELFAsmParser::ParseDirectiveIdent(StringRef, SMLoc) {
  if (getLexer().isNot(AsmToken::String))
    return TokError("unexpected token in '.ident' directive");

  StringRef Data = getTok().getIdentifier();

  Lex();

  const MCSection *Comment =
    getContext().getELFSection(".comment", ELF::SHT_PROGBITS,
                               ELF::SHF_MERGE |
                               ELF::SHF_STRINGS,
                               SectionKind::getReadOnly(),
                               1, "");

  getStreamer().PushSection();
  getStreamer().SwitchSection(Comment);
  if (!SeenIdent) {
    getStreamer().EmitIntValue(0, 1);
    SeenIdent = true;
  }
  getStreamer().EmitBytes(Data, 0);
  getStreamer().EmitIntValue(0, 1);
  getStreamer().PopSection();
  return false;
}

/// ParseDirectiveSymver
///  ::= .symver foo, bar2@zed
bool ELFAsmParser::ParseDirectiveSymver(StringRef, SMLoc) {
  StringRef Name;
  if (getParser().ParseIdentifier(Name))
    return TokError("expected identifier in directive");

  if (getLexer().isNot(AsmToken::Comma))
    return TokError("expected a comma");

  Lex();

  StringRef AliasName;
  if (getParser().ParseIdentifier(AliasName))
    return TokError("expected identifier in directive");

  if (AliasName.find('@') == StringRef::npos)
    return TokError("expected a '@' in the name");

  MCSymbol *Alias = getContext().GetOrCreateSymbol(AliasName);
  MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);
  const MCExpr *Value = MCSymbolRefExpr::Create(Sym, getContext());

  getStreamer().EmitAssignment(Alias, Value);
  return false;
}

/// ParseDirectiveWeakref
///  ::= .weakref foo, bar
bool ELFAsmParser::ParseDirectiveWeakref(StringRef, SMLoc) {
  // FIXME: Share code with the other alias building directives.

  StringRef AliasName;
  if (getParser().ParseIdentifier(AliasName))
    return TokError("expected identifier in directive");

  if (getLexer().isNot(AsmToken::Comma))
    return TokError("expected a comma");

  Lex();

  StringRef Name;
  if (getParser().ParseIdentifier(Name))
    return TokError("expected identifier in directive");

  MCSymbol *Alias = getContext().GetOrCreateSymbol(AliasName);

  MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);

  getStreamer().EmitWeakReference(Alias, Sym);
  return false;
}

namespace llvm {

MCAsmParserExtension *createELFAsmParser() {
  return new ELFAsmParser;
}

}