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/ADT/StringRef.h"
11 #include "llvm/ADT/StringSwitch.h"
12 #include "llvm/BinaryFormat/ELF.h"
13 #include "llvm/MC/MCAsmInfo.h"
14 #include "llvm/MC/MCContext.h"
15 #include "llvm/MC/MCDirectives.h"
16 #include "llvm/MC/MCExpr.h"
17 #include "llvm/MC/MCParser/MCAsmLexer.h"
18 #include "llvm/MC/MCParser/MCAsmParser.h"
19 #include "llvm/MC/MCParser/MCAsmParserExtension.h"
20 #include "llvm/MC/MCSection.h"
21 #include "llvm/MC/MCSectionELF.h"
22 #include "llvm/MC/MCStreamer.h"
23 #include "llvm/MC/MCSymbol.h"
24 #include "llvm/MC/MCSymbolELF.h"
25 #include "llvm/MC/SectionKind.h"
26 #include "llvm/Support/Casting.h"
27 #include "llvm/Support/MathExtras.h"
28 #include "llvm/Support/SMLoc.h"
29 #include <cassert>
30 #include <cstdint>
31 #include <utility>
32 
33 using namespace llvm;
34 
35 namespace {
36 
37 class ELFAsmParser : public MCAsmParserExtension {
38   template<bool (ELFAsmParser::*HandlerMethod)(StringRef, SMLoc)>
39   void addDirectiveHandler(StringRef Directive) {
40     MCAsmParser::ExtensionDirectiveHandler Handler = std::make_pair(
41         this, HandleDirective<ELFAsmParser, HandlerMethod>);
42 
43     getParser().addDirectiveHandler(Directive, Handler);
44   }
45 
46   bool ParseSectionSwitch(StringRef Section, unsigned Type, unsigned Flags,
47                           SectionKind Kind);
48 
49 public:
50   ELFAsmParser() { BracketExpressionsSupported = true; }
51 
52   void Initialize(MCAsmParser &Parser) override {
53     // Call the base implementation.
54     this->MCAsmParserExtension::Initialize(Parser);
55 
56     addDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveData>(".data");
57     addDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveText>(".text");
58     addDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveBSS>(".bss");
59     addDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveRoData>(".rodata");
60     addDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveTData>(".tdata");
61     addDirectiveHandler<&ELFAsmParser::ParseSectionDirectiveTBSS>(".tbss");
62     addDirectiveHandler<
63       &ELFAsmParser::ParseSectionDirectiveDataRel>(".data.rel");
64     addDirectiveHandler<
65       &ELFAsmParser::ParseSectionDirectiveDataRelRo>(".data.rel.ro");
66     addDirectiveHandler<
67       &ELFAsmParser::ParseSectionDirectiveEhFrame>(".eh_frame");
68     addDirectiveHandler<&ELFAsmParser::ParseDirectiveSection>(".section");
69     addDirectiveHandler<
70       &ELFAsmParser::ParseDirectivePushSection>(".pushsection");
71     addDirectiveHandler<&ELFAsmParser::ParseDirectivePopSection>(".popsection");
72     addDirectiveHandler<&ELFAsmParser::ParseDirectiveSize>(".size");
73     addDirectiveHandler<&ELFAsmParser::ParseDirectivePrevious>(".previous");
74     addDirectiveHandler<&ELFAsmParser::ParseDirectiveType>(".type");
75     addDirectiveHandler<&ELFAsmParser::ParseDirectiveIdent>(".ident");
76     addDirectiveHandler<&ELFAsmParser::ParseDirectiveSymver>(".symver");
77     addDirectiveHandler<&ELFAsmParser::ParseDirectiveVersion>(".version");
78     addDirectiveHandler<&ELFAsmParser::ParseDirectiveWeakref>(".weakref");
79     addDirectiveHandler<&ELFAsmParser::ParseDirectiveSymbolAttribute>(".weak");
80     addDirectiveHandler<&ELFAsmParser::ParseDirectiveSymbolAttribute>(".local");
81     addDirectiveHandler<
82       &ELFAsmParser::ParseDirectiveSymbolAttribute>(".protected");
83     addDirectiveHandler<
84       &ELFAsmParser::ParseDirectiveSymbolAttribute>(".internal");
85     addDirectiveHandler<
86       &ELFAsmParser::ParseDirectiveSymbolAttribute>(".hidden");
87     addDirectiveHandler<&ELFAsmParser::ParseDirectiveSubsection>(".subsection");
88   }
89 
90   // FIXME: Part of this logic is duplicated in the MCELFStreamer. What is
91   // the best way for us to get access to it?
92   bool ParseSectionDirectiveData(StringRef, SMLoc) {
93     return ParseSectionSwitch(".data", ELF::SHT_PROGBITS,
94                               ELF::SHF_WRITE | ELF::SHF_ALLOC,
95                               SectionKind::getData());
96   }
97   bool ParseSectionDirectiveText(StringRef, SMLoc) {
98     return ParseSectionSwitch(".text", ELF::SHT_PROGBITS,
99                               ELF::SHF_EXECINSTR |
100                               ELF::SHF_ALLOC, SectionKind::getText());
101   }
102   bool ParseSectionDirectiveBSS(StringRef, SMLoc) {
103     return ParseSectionSwitch(".bss", ELF::SHT_NOBITS,
104                               ELF::SHF_WRITE |
105                               ELF::SHF_ALLOC, SectionKind::getBSS());
106   }
107   bool ParseSectionDirectiveRoData(StringRef, SMLoc) {
108     return ParseSectionSwitch(".rodata", ELF::SHT_PROGBITS,
109                               ELF::SHF_ALLOC,
110                               SectionKind::getReadOnly());
111   }
112   bool ParseSectionDirectiveTData(StringRef, SMLoc) {
113     return ParseSectionSwitch(".tdata", ELF::SHT_PROGBITS,
114                               ELF::SHF_ALLOC |
115                               ELF::SHF_TLS | ELF::SHF_WRITE,
116                               SectionKind::getThreadData());
117   }
118   bool ParseSectionDirectiveTBSS(StringRef, SMLoc) {
119     return ParseSectionSwitch(".tbss", ELF::SHT_NOBITS,
120                               ELF::SHF_ALLOC |
121                               ELF::SHF_TLS | ELF::SHF_WRITE,
122                               SectionKind::getThreadBSS());
123   }
124   bool ParseSectionDirectiveDataRel(StringRef, SMLoc) {
125     return ParseSectionSwitch(".data.rel", ELF::SHT_PROGBITS,
126                               ELF::SHF_ALLOC | ELF::SHF_WRITE,
127                               SectionKind::getData());
128   }
129   bool ParseSectionDirectiveDataRelRo(StringRef, SMLoc) {
130     return ParseSectionSwitch(".data.rel.ro", ELF::SHT_PROGBITS,
131                               ELF::SHF_ALLOC |
132                               ELF::SHF_WRITE,
133                               SectionKind::getReadOnlyWithRel());
134   }
135   bool ParseSectionDirectiveEhFrame(StringRef, SMLoc) {
136     return ParseSectionSwitch(".eh_frame", ELF::SHT_PROGBITS,
137                               ELF::SHF_ALLOC | ELF::SHF_WRITE,
138                               SectionKind::getData());
139   }
140   bool ParseDirectivePushSection(StringRef, SMLoc);
141   bool ParseDirectivePopSection(StringRef, SMLoc);
142   bool ParseDirectiveSection(StringRef, SMLoc);
143   bool ParseDirectiveSize(StringRef, SMLoc);
144   bool ParseDirectivePrevious(StringRef, SMLoc);
145   bool ParseDirectiveType(StringRef, SMLoc);
146   bool ParseDirectiveIdent(StringRef, SMLoc);
147   bool ParseDirectiveSymver(StringRef, SMLoc);
148   bool ParseDirectiveVersion(StringRef, SMLoc);
149   bool ParseDirectiveWeakref(StringRef, SMLoc);
150   bool ParseDirectiveSymbolAttribute(StringRef, SMLoc);
151   bool ParseDirectiveSubsection(StringRef, SMLoc);
152 
153 private:
154   bool ParseSectionName(StringRef &SectionName);
155   bool ParseSectionArguments(bool IsPush, SMLoc loc);
156   unsigned parseSunStyleSectionFlags();
157   bool maybeParseSectionType(StringRef &TypeName);
158   bool parseMergeSize(int64_t &Size);
159   bool parseGroup(StringRef &GroupName);
160   bool parseMetadataSym(MCSymbolELF *&Associated);
161   bool maybeParseUniqueID(int64_t &UniqueID);
162 };
163 
164 } // end anonymous namespace
165 
166 /// ParseDirectiveSymbolAttribute
167 ///  ::= { ".local", ".weak", ... } [ identifier ( , identifier )* ]
168 bool ELFAsmParser::ParseDirectiveSymbolAttribute(StringRef Directive, SMLoc) {
169   MCSymbolAttr Attr = StringSwitch<MCSymbolAttr>(Directive)
170     .Case(".weak", MCSA_Weak)
171     .Case(".local", MCSA_Local)
172     .Case(".hidden", MCSA_Hidden)
173     .Case(".internal", MCSA_Internal)
174     .Case(".protected", MCSA_Protected)
175     .Default(MCSA_Invalid);
176   assert(Attr != MCSA_Invalid && "unexpected symbol attribute directive!");
177   if (getLexer().isNot(AsmToken::EndOfStatement)) {
178     while (true) {
179       StringRef Name;
180 
181       if (getParser().parseIdentifier(Name))
182         return TokError("expected identifier in directive");
183 
184       MCSymbol *Sym = getContext().getOrCreateSymbol(Name);
185 
186       getStreamer().EmitSymbolAttribute(Sym, Attr);
187 
188       if (getLexer().is(AsmToken::EndOfStatement))
189         break;
190 
191       if (getLexer().isNot(AsmToken::Comma))
192         return TokError("unexpected token in directive");
193       Lex();
194     }
195   }
196 
197   Lex();
198   return false;
199 }
200 
201 bool ELFAsmParser::ParseSectionSwitch(StringRef Section, unsigned Type,
202                                       unsigned Flags, SectionKind Kind) {
203   const MCExpr *Subsection = nullptr;
204   if (getLexer().isNot(AsmToken::EndOfStatement)) {
205     if (getParser().parseExpression(Subsection))
206       return true;
207   }
208   Lex();
209 
210   getStreamer().SwitchSection(getContext().getELFSection(Section, Type, Flags),
211                               Subsection);
212 
213   return false;
214 }
215 
216 bool ELFAsmParser::ParseDirectiveSize(StringRef, SMLoc) {
217   StringRef Name;
218   if (getParser().parseIdentifier(Name))
219     return TokError("expected identifier in directive");
220   MCSymbolELF *Sym = cast<MCSymbolELF>(getContext().getOrCreateSymbol(Name));
221 
222   if (getLexer().isNot(AsmToken::Comma))
223     return TokError("unexpected token in directive");
224   Lex();
225 
226   const MCExpr *Expr;
227   if (getParser().parseExpression(Expr))
228     return true;
229 
230   if (getLexer().isNot(AsmToken::EndOfStatement))
231     return TokError("unexpected token in directive");
232   Lex();
233 
234   getStreamer().emitELFSize(Sym, Expr);
235   return false;
236 }
237 
238 bool ELFAsmParser::ParseSectionName(StringRef &SectionName) {
239   // A section name can contain -, so we cannot just use
240   // parseIdentifier.
241   SMLoc FirstLoc = getLexer().getLoc();
242   unsigned Size = 0;
243 
244   if (getLexer().is(AsmToken::String)) {
245     SectionName = getTok().getIdentifier();
246     Lex();
247     return false;
248   }
249 
250   while (!getParser().hasPendingError()) {
251     SMLoc PrevLoc = getLexer().getLoc();
252     if (getLexer().is(AsmToken::Comma) ||
253       getLexer().is(AsmToken::EndOfStatement))
254       break;
255 
256     unsigned CurSize;
257     if (getLexer().is(AsmToken::String)) {
258       CurSize = getTok().getIdentifier().size() + 2;
259       Lex();
260     } else if (getLexer().is(AsmToken::Identifier)) {
261       CurSize = getTok().getIdentifier().size();
262       Lex();
263     } else {
264       CurSize = getTok().getString().size();
265       Lex();
266     }
267     Size += CurSize;
268     SectionName = StringRef(FirstLoc.getPointer(), Size);
269 
270     // Make sure the following token is adjacent.
271     if (PrevLoc.getPointer() + CurSize != getTok().getLoc().getPointer())
272       break;
273   }
274   if (Size == 0)
275     return true;
276 
277   return false;
278 }
279 
280 static unsigned parseSectionFlags(StringRef flagsStr, bool *UseLastGroup) {
281   unsigned flags = 0;
282 
283   // If a valid numerical value is set for the section flag, use it verbatim
284   if (!flagsStr.getAsInteger(0, flags))
285     return flags;
286 
287   for (char i : flagsStr) {
288     switch (i) {
289     case 'a':
290       flags |= ELF::SHF_ALLOC;
291       break;
292     case 'e':
293       flags |= ELF::SHF_EXCLUDE;
294       break;
295     case 'x':
296       flags |= ELF::SHF_EXECINSTR;
297       break;
298     case 'w':
299       flags |= ELF::SHF_WRITE;
300       break;
301     case 'o':
302       flags |= ELF::SHF_LINK_ORDER;
303       break;
304     case 'M':
305       flags |= ELF::SHF_MERGE;
306       break;
307     case 'S':
308       flags |= ELF::SHF_STRINGS;
309       break;
310     case 'T':
311       flags |= ELF::SHF_TLS;
312       break;
313     case 'c':
314       flags |= ELF::XCORE_SHF_CP_SECTION;
315       break;
316     case 'd':
317       flags |= ELF::XCORE_SHF_DP_SECTION;
318       break;
319     case 'y':
320       flags |= ELF::SHF_ARM_PURECODE;
321       break;
322     case 'G':
323       flags |= ELF::SHF_GROUP;
324       break;
325     case '?':
326       *UseLastGroup = true;
327       break;
328     default:
329       return -1U;
330     }
331   }
332 
333   return flags;
334 }
335 
336 unsigned ELFAsmParser::parseSunStyleSectionFlags() {
337   unsigned flags = 0;
338   while (getLexer().is(AsmToken::Hash)) {
339     Lex(); // Eat the #.
340 
341     if (!getLexer().is(AsmToken::Identifier))
342       return -1U;
343 
344     StringRef flagId = getTok().getIdentifier();
345     if (flagId == "alloc")
346       flags |= ELF::SHF_ALLOC;
347     else if (flagId == "execinstr")
348       flags |= ELF::SHF_EXECINSTR;
349     else if (flagId == "write")
350       flags |= ELF::SHF_WRITE;
351     else if (flagId == "tls")
352       flags |= ELF::SHF_TLS;
353     else
354       return -1U;
355 
356     Lex(); // Eat the flag.
357 
358     if (!getLexer().is(AsmToken::Comma))
359         break;
360     Lex(); // Eat the comma.
361   }
362   return flags;
363 }
364 
365 
366 bool ELFAsmParser::ParseDirectivePushSection(StringRef s, SMLoc loc) {
367   getStreamer().PushSection();
368 
369   if (ParseSectionArguments(/*IsPush=*/true, loc)) {
370     getStreamer().PopSection();
371     return true;
372   }
373 
374   return false;
375 }
376 
377 bool ELFAsmParser::ParseDirectivePopSection(StringRef, SMLoc) {
378   if (!getStreamer().PopSection())
379     return TokError(".popsection without corresponding .pushsection");
380   return false;
381 }
382 
383 // FIXME: This is a work in progress.
384 bool ELFAsmParser::ParseDirectiveSection(StringRef, SMLoc loc) {
385   return ParseSectionArguments(/*IsPush=*/false, loc);
386 }
387 
388 bool ELFAsmParser::maybeParseSectionType(StringRef &TypeName) {
389   MCAsmLexer &L = getLexer();
390   if (L.isNot(AsmToken::Comma))
391     return false;
392   Lex();
393   if (L.isNot(AsmToken::At) && L.isNot(AsmToken::Percent) &&
394       L.isNot(AsmToken::String)) {
395     if (L.getAllowAtInIdentifier())
396       return TokError("expected '@<type>', '%<type>' or \"<type>\"");
397     else
398       return TokError("expected '%<type>' or \"<type>\"");
399   }
400   if (!L.is(AsmToken::String))
401     Lex();
402   if (L.is(AsmToken::Integer)) {
403     TypeName = getTok().getString();
404     Lex();
405   } else if (getParser().parseIdentifier(TypeName))
406     return TokError("expected identifier in directive");
407   return false;
408 }
409 
410 bool ELFAsmParser::parseMergeSize(int64_t &Size) {
411   if (getLexer().isNot(AsmToken::Comma))
412     return TokError("expected the entry size");
413   Lex();
414   if (getParser().parseAbsoluteExpression(Size))
415     return true;
416   if (Size <= 0)
417     return TokError("entry size must be positive");
418   return false;
419 }
420 
421 bool ELFAsmParser::parseGroup(StringRef &GroupName) {
422   MCAsmLexer &L = getLexer();
423   if (L.isNot(AsmToken::Comma))
424     return TokError("expected group name");
425   Lex();
426   if (L.is(AsmToken::Integer)) {
427     GroupName = getTok().getString();
428     Lex();
429   } else if (getParser().parseIdentifier(GroupName)) {
430     return TokError("invalid group name");
431   }
432   if (L.is(AsmToken::Comma)) {
433     Lex();
434     StringRef Linkage;
435     if (getParser().parseIdentifier(Linkage))
436       return TokError("invalid linkage");
437     if (Linkage != "comdat")
438       return TokError("Linkage must be 'comdat'");
439   }
440   return false;
441 }
442 
443 bool ELFAsmParser::parseMetadataSym(MCSymbolELF *&Associated) {
444   MCAsmLexer &L = getLexer();
445   if (L.isNot(AsmToken::Comma))
446     return TokError("expected metadata symbol");
447   Lex();
448   StringRef Name;
449   if (getParser().parseIdentifier(Name))
450     return TokError("invalid metadata symbol");
451   Associated = dyn_cast_or_null<MCSymbolELF>(getContext().lookupSymbol(Name));
452   if (!Associated || !Associated->isInSection())
453     return TokError("symbol is not in a section: " + Name);
454   return false;
455 }
456 
457 bool ELFAsmParser::maybeParseUniqueID(int64_t &UniqueID) {
458   MCAsmLexer &L = getLexer();
459   if (L.isNot(AsmToken::Comma))
460     return false;
461   Lex();
462   StringRef UniqueStr;
463   if (getParser().parseIdentifier(UniqueStr))
464     return TokError("expected identifier in directive");
465   if (UniqueStr != "unique")
466     return TokError("expected 'unique'");
467   if (L.isNot(AsmToken::Comma))
468     return TokError("expected commma");
469   Lex();
470   if (getParser().parseAbsoluteExpression(UniqueID))
471     return true;
472   if (UniqueID < 0)
473     return TokError("unique id must be positive");
474   if (!isUInt<32>(UniqueID) || UniqueID == ~0U)
475     return TokError("unique id is too large");
476   return false;
477 }
478 
479 static bool hasPrefix(StringRef SectionName, StringRef Prefix) {
480   return SectionName.startswith(Prefix) || SectionName == Prefix.drop_back();
481 }
482 
483 bool ELFAsmParser::ParseSectionArguments(bool IsPush, SMLoc loc) {
484   StringRef SectionName;
485 
486   if (ParseSectionName(SectionName))
487     return TokError("expected identifier in directive");
488 
489   StringRef TypeName;
490   int64_t Size = 0;
491   StringRef GroupName;
492   unsigned Flags = 0;
493   const MCExpr *Subsection = nullptr;
494   bool UseLastGroup = false;
495   MCSymbolELF *Associated = nullptr;
496   int64_t UniqueID = ~0;
497 
498   // Set the defaults first.
499   if (hasPrefix(SectionName, ".rodata.") || SectionName == ".rodata1")
500     Flags |= ELF::SHF_ALLOC;
501   if (SectionName == ".fini" || SectionName == ".init" ||
502       hasPrefix(SectionName, ".text."))
503     Flags |= ELF::SHF_ALLOC | ELF::SHF_EXECINSTR;
504   if (hasPrefix(SectionName, ".data.") || SectionName == ".data1" ||
505       hasPrefix(SectionName, ".bss.") ||
506       hasPrefix(SectionName, ".init_array.") ||
507       hasPrefix(SectionName, ".fini_array.") ||
508       hasPrefix(SectionName, ".preinit_array."))
509     Flags |= ELF::SHF_ALLOC | ELF::SHF_WRITE;
510   if (hasPrefix(SectionName, ".tdata.") ||
511       hasPrefix(SectionName, ".tbss."))
512     Flags |= ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_TLS;
513 
514   if (getLexer().is(AsmToken::Comma)) {
515     Lex();
516 
517     if (IsPush && getLexer().isNot(AsmToken::String)) {
518       if (getParser().parseExpression(Subsection))
519         return true;
520       if (getLexer().isNot(AsmToken::Comma))
521         goto EndStmt;
522       Lex();
523     }
524 
525     unsigned extraFlags;
526 
527     if (getLexer().isNot(AsmToken::String)) {
528       if (!getContext().getAsmInfo()->usesSunStyleELFSectionSwitchSyntax()
529           || getLexer().isNot(AsmToken::Hash))
530         return TokError("expected string in directive");
531       extraFlags = parseSunStyleSectionFlags();
532     } else {
533       StringRef FlagsStr = getTok().getStringContents();
534       Lex();
535       extraFlags = parseSectionFlags(FlagsStr, &UseLastGroup);
536     }
537 
538     if (extraFlags == -1U)
539       return TokError("unknown flag");
540     Flags |= extraFlags;
541 
542     bool Mergeable = Flags & ELF::SHF_MERGE;
543     bool Group = Flags & ELF::SHF_GROUP;
544     if (Group && UseLastGroup)
545       return TokError("Section cannot specifiy a group name while also acting "
546                       "as a member of the last group");
547 
548     if (maybeParseSectionType(TypeName))
549       return true;
550 
551     MCAsmLexer &L = getLexer();
552     if (TypeName.empty()) {
553       if (Mergeable)
554         return TokError("Mergeable section must specify the type");
555       if (Group)
556         return TokError("Group section must specify the type");
557       if (L.isNot(AsmToken::EndOfStatement))
558         return TokError("unexpected token in directive");
559     }
560 
561     if (Mergeable)
562       if (parseMergeSize(Size))
563         return true;
564     if (Group)
565       if (parseGroup(GroupName))
566         return true;
567     if (Flags & ELF::SHF_LINK_ORDER)
568       if (parseMetadataSym(Associated))
569         return true;
570     if (maybeParseUniqueID(UniqueID))
571       return true;
572   }
573 
574 EndStmt:
575   if (getLexer().isNot(AsmToken::EndOfStatement))
576     return TokError("unexpected token in directive");
577   Lex();
578 
579   unsigned Type = ELF::SHT_PROGBITS;
580 
581   if (TypeName.empty()) {
582     if (SectionName.startswith(".note"))
583       Type = ELF::SHT_NOTE;
584     else if (hasPrefix(SectionName, ".init_array."))
585       Type = ELF::SHT_INIT_ARRAY;
586     else if (hasPrefix(SectionName, ".bss."))
587       Type = ELF::SHT_NOBITS;
588     else if (hasPrefix(SectionName, ".tbss."))
589       Type = ELF::SHT_NOBITS;
590     else if (hasPrefix(SectionName, ".fini_array."))
591       Type = ELF::SHT_FINI_ARRAY;
592     else if (hasPrefix(SectionName, ".preinit_array."))
593       Type = ELF::SHT_PREINIT_ARRAY;
594   } else {
595     if (TypeName == "init_array")
596       Type = ELF::SHT_INIT_ARRAY;
597     else if (TypeName == "fini_array")
598       Type = ELF::SHT_FINI_ARRAY;
599     else if (TypeName == "preinit_array")
600       Type = ELF::SHT_PREINIT_ARRAY;
601     else if (TypeName == "nobits")
602       Type = ELF::SHT_NOBITS;
603     else if (TypeName == "progbits")
604       Type = ELF::SHT_PROGBITS;
605     else if (TypeName == "note")
606       Type = ELF::SHT_NOTE;
607     else if (TypeName == "unwind")
608       Type = ELF::SHT_X86_64_UNWIND;
609     else if (TypeName == "llvm_odrtab")
610       Type = ELF::SHT_LLVM_ODRTAB;
611     else if (TypeName.getAsInteger(0, Type))
612       return TokError("unknown section type");
613   }
614 
615   if (UseLastGroup) {
616     MCSectionSubPair CurrentSection = getStreamer().getCurrentSection();
617     if (const MCSectionELF *Section =
618             cast_or_null<MCSectionELF>(CurrentSection.first))
619       if (const MCSymbol *Group = Section->getGroup()) {
620         GroupName = Group->getName();
621         Flags |= ELF::SHF_GROUP;
622       }
623   }
624 
625   MCSection *ELFSection =
626       getContext().getELFSection(SectionName, Type, Flags, Size, GroupName,
627                                  UniqueID, Associated);
628   getStreamer().SwitchSection(ELFSection, Subsection);
629 
630   if (getContext().getGenDwarfForAssembly()) {
631     bool InsertResult = getContext().addGenDwarfSection(ELFSection);
632     if (InsertResult) {
633       if (getContext().getDwarfVersion() <= 2)
634         Warning(loc, "DWARF2 only supports one section per compilation unit");
635 
636       if (!ELFSection->getBeginSymbol()) {
637         MCSymbol *SectionStartSymbol = getContext().createTempSymbol();
638         getStreamer().EmitLabel(SectionStartSymbol);
639         ELFSection->setBeginSymbol(SectionStartSymbol);
640       }
641     }
642   }
643 
644   return false;
645 }
646 
647 bool ELFAsmParser::ParseDirectivePrevious(StringRef DirName, SMLoc) {
648   MCSectionSubPair PreviousSection = getStreamer().getPreviousSection();
649   if (PreviousSection.first == nullptr)
650       return TokError(".previous without corresponding .section");
651   getStreamer().SwitchSection(PreviousSection.first, PreviousSection.second);
652 
653   return false;
654 }
655 
656 static MCSymbolAttr MCAttrForString(StringRef Type) {
657   return StringSwitch<MCSymbolAttr>(Type)
658           .Cases("STT_FUNC", "function", MCSA_ELF_TypeFunction)
659           .Cases("STT_OBJECT", "object", MCSA_ELF_TypeObject)
660           .Cases("STT_TLS", "tls_object", MCSA_ELF_TypeTLS)
661           .Cases("STT_COMMON", "common", MCSA_ELF_TypeCommon)
662           .Cases("STT_NOTYPE", "notype", MCSA_ELF_TypeNoType)
663           .Cases("STT_GNU_IFUNC", "gnu_indirect_function",
664                  MCSA_ELF_TypeIndFunction)
665           .Case("gnu_unique_object", MCSA_ELF_TypeGnuUniqueObject)
666           .Default(MCSA_Invalid);
667 }
668 
669 /// ParseDirectiveELFType
670 ///  ::= .type identifier , STT_<TYPE_IN_UPPER_CASE>
671 ///  ::= .type identifier , #attribute
672 ///  ::= .type identifier , @attribute
673 ///  ::= .type identifier , %attribute
674 ///  ::= .type identifier , "attribute"
675 bool ELFAsmParser::ParseDirectiveType(StringRef, SMLoc) {
676   StringRef Name;
677   if (getParser().parseIdentifier(Name))
678     return TokError("expected identifier in directive");
679 
680   // Handle the identifier as the key symbol.
681   MCSymbol *Sym = getContext().getOrCreateSymbol(Name);
682 
683   // NOTE the comma is optional in all cases.  It is only documented as being
684   // optional in the first case, however, GAS will silently treat the comma as
685   // optional in all cases.  Furthermore, although the documentation states that
686   // the first form only accepts STT_<TYPE_IN_UPPER_CASE>, in reality, GAS
687   // accepts both the upper case name as well as the lower case aliases.
688   if (getLexer().is(AsmToken::Comma))
689     Lex();
690 
691   if (getLexer().isNot(AsmToken::Identifier) &&
692       getLexer().isNot(AsmToken::Hash) &&
693       getLexer().isNot(AsmToken::Percent) &&
694       getLexer().isNot(AsmToken::String)) {
695     if (!getLexer().getAllowAtInIdentifier())
696       return TokError("expected STT_<TYPE_IN_UPPER_CASE>, '#<type>', "
697                       "'%<type>' or \"<type>\"");
698     else if (getLexer().isNot(AsmToken::At))
699       return TokError("expected STT_<TYPE_IN_UPPER_CASE>, '#<type>', '@<type>', "
700                       "'%<type>' or \"<type>\"");
701   }
702 
703   if (getLexer().isNot(AsmToken::String) &&
704       getLexer().isNot(AsmToken::Identifier))
705     Lex();
706 
707   SMLoc TypeLoc = getLexer().getLoc();
708 
709   StringRef Type;
710   if (getParser().parseIdentifier(Type))
711     return TokError("expected symbol type in directive");
712 
713   MCSymbolAttr Attr = MCAttrForString(Type);
714   if (Attr == MCSA_Invalid)
715     return Error(TypeLoc, "unsupported attribute in '.type' directive");
716 
717   if (getLexer().isNot(AsmToken::EndOfStatement))
718     return TokError("unexpected token in '.type' directive");
719   Lex();
720 
721   getStreamer().EmitSymbolAttribute(Sym, Attr);
722 
723   return false;
724 }
725 
726 /// ParseDirectiveIdent
727 ///  ::= .ident string
728 bool ELFAsmParser::ParseDirectiveIdent(StringRef, SMLoc) {
729   if (getLexer().isNot(AsmToken::String))
730     return TokError("unexpected token in '.ident' directive");
731 
732   StringRef Data = getTok().getIdentifier();
733 
734   Lex();
735 
736   if (getLexer().isNot(AsmToken::EndOfStatement))
737     return TokError("unexpected token in '.ident' directive");
738   Lex();
739 
740   getStreamer().EmitIdent(Data);
741   return false;
742 }
743 
744 /// ParseDirectiveSymver
745 ///  ::= .symver foo, bar2@zed
746 bool ELFAsmParser::ParseDirectiveSymver(StringRef, SMLoc) {
747   StringRef Name;
748   if (getParser().parseIdentifier(Name))
749     return TokError("expected identifier in directive");
750 
751   if (getLexer().isNot(AsmToken::Comma))
752     return TokError("expected a comma");
753 
754   // ARM assembly uses @ for a comment...
755   // except when parsing the second parameter of the .symver directive.
756   // Force the next symbol to allow @ in the identifier, which is
757   // required for this directive and then reset it to its initial state.
758   const bool AllowAtInIdentifier = getLexer().getAllowAtInIdentifier();
759   getLexer().setAllowAtInIdentifier(true);
760   Lex();
761   getLexer().setAllowAtInIdentifier(AllowAtInIdentifier);
762 
763   StringRef AliasName;
764   if (getParser().parseIdentifier(AliasName))
765     return TokError("expected identifier in directive");
766 
767   if (AliasName.find('@') == StringRef::npos)
768     return TokError("expected a '@' in the name");
769 
770   MCSymbol *Sym = getContext().getOrCreateSymbol(Name);
771   getStreamer().emitELFSymverDirective(AliasName, Sym);
772   return false;
773 }
774 
775 /// ParseDirectiveVersion
776 ///  ::= .version string
777 bool ELFAsmParser::ParseDirectiveVersion(StringRef, SMLoc) {
778   if (getLexer().isNot(AsmToken::String))
779     return TokError("unexpected token in '.version' directive");
780 
781   StringRef Data = getTok().getIdentifier();
782 
783   Lex();
784 
785   MCSection *Note = getContext().getELFSection(".note", ELF::SHT_NOTE, 0);
786 
787   getStreamer().PushSection();
788   getStreamer().SwitchSection(Note);
789   getStreamer().EmitIntValue(Data.size()+1, 4); // namesz.
790   getStreamer().EmitIntValue(0, 4);             // descsz = 0 (no description).
791   getStreamer().EmitIntValue(1, 4);             // type = NT_VERSION.
792   getStreamer().EmitBytes(Data);                // name.
793   getStreamer().EmitIntValue(0, 1);             // terminate the string.
794   getStreamer().EmitValueToAlignment(4);        // ensure 4 byte alignment.
795   getStreamer().PopSection();
796   return false;
797 }
798 
799 /// ParseDirectiveWeakref
800 ///  ::= .weakref foo, bar
801 bool ELFAsmParser::ParseDirectiveWeakref(StringRef, SMLoc) {
802   // FIXME: Share code with the other alias building directives.
803 
804   StringRef AliasName;
805   if (getParser().parseIdentifier(AliasName))
806     return TokError("expected identifier in directive");
807 
808   if (getLexer().isNot(AsmToken::Comma))
809     return TokError("expected a comma");
810 
811   Lex();
812 
813   StringRef Name;
814   if (getParser().parseIdentifier(Name))
815     return TokError("expected identifier in directive");
816 
817   MCSymbol *Alias = getContext().getOrCreateSymbol(AliasName);
818 
819   MCSymbol *Sym = getContext().getOrCreateSymbol(Name);
820 
821   getStreamer().EmitWeakReference(Alias, Sym);
822   return false;
823 }
824 
825 bool ELFAsmParser::ParseDirectiveSubsection(StringRef, SMLoc) {
826   const MCExpr *Subsection = nullptr;
827   if (getLexer().isNot(AsmToken::EndOfStatement)) {
828     if (getParser().parseExpression(Subsection))
829      return true;
830   }
831 
832   if (getLexer().isNot(AsmToken::EndOfStatement))
833     return TokError("unexpected token in directive");
834 
835   Lex();
836 
837   getStreamer().SubSection(Subsection);
838   return false;
839 }
840 
841 namespace llvm {
842 
843 MCAsmParserExtension *createELFAsmParser() {
844   return new ELFAsmParser;
845 }
846 
847 } // end namespace llvm
848