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      1 //===- lib/MC/MCContext.cpp - Machine Code Context ------------------------===//
      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/MCContext.h"
     11 #include "llvm/ADT/SmallString.h"
     12 #include "llvm/ADT/Twine.h"
     13 #include "llvm/MC/MCAssembler.h"
     14 #include "llvm/MC/MCAsmInfo.h"
     15 #include "llvm/MC/MCDwarf.h"
     16 #include "llvm/MC/MCLabel.h"
     17 #include "llvm/MC/MCObjectFileInfo.h"
     18 #include "llvm/MC/MCRegisterInfo.h"
     19 #include "llvm/MC/MCSectionCOFF.h"
     20 #include "llvm/MC/MCSectionELF.h"
     21 #include "llvm/MC/MCSectionMachO.h"
     22 #include "llvm/MC/MCStreamer.h"
     23 #include "llvm/MC/MCSymbolCOFF.h"
     24 #include "llvm/MC/MCSymbolELF.h"
     25 #include "llvm/MC/MCSymbolMachO.h"
     26 #include "llvm/Support/COFF.h"
     27 #include "llvm/Support/ELF.h"
     28 #include "llvm/Support/ErrorHandling.h"
     29 #include "llvm/Support/FileSystem.h"
     30 #include "llvm/Support/MemoryBuffer.h"
     31 #include "llvm/Support/Signals.h"
     32 #include "llvm/Support/SourceMgr.h"
     33 #include <map>
     34 
     35 using namespace llvm;
     36 
     37 MCContext::MCContext(const MCAsmInfo *mai, const MCRegisterInfo *mri,
     38                      const MCObjectFileInfo *mofi, const SourceMgr *mgr,
     39                      bool DoAutoReset)
     40     : SrcMgr(mgr), MAI(mai), MRI(mri), MOFI(mofi), Allocator(),
     41       Symbols(Allocator), UsedNames(Allocator),
     42       CurrentDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0), DwarfLocSeen(false),
     43       GenDwarfForAssembly(false), GenDwarfFileNumber(0), DwarfVersion(4),
     44       AllowTemporaryLabels(true), DwarfCompileUnitID(0),
     45       AutoReset(DoAutoReset), HadError(false) {
     46 
     47   std::error_code EC = llvm::sys::fs::current_path(CompilationDir);
     48   if (EC)
     49     CompilationDir.clear();
     50 
     51   SecureLogFile = getenv("AS_SECURE_LOG_FILE");
     52   SecureLog = nullptr;
     53   SecureLogUsed = false;
     54 
     55   if (SrcMgr && SrcMgr->getNumBuffers())
     56     MainFileName =
     57         SrcMgr->getMemoryBuffer(SrcMgr->getMainFileID())->getBufferIdentifier();
     58 }
     59 
     60 MCContext::~MCContext() {
     61   if (AutoReset)
     62     reset();
     63 
     64   // NOTE: The symbols are all allocated out of a bump pointer allocator,
     65   // we don't need to free them here.
     66 }
     67 
     68 //===----------------------------------------------------------------------===//
     69 // Module Lifetime Management
     70 //===----------------------------------------------------------------------===//
     71 
     72 void MCContext::reset() {
     73   // Call the destructors so the fragments are freed
     74   COFFAllocator.DestroyAll();
     75   ELFAllocator.DestroyAll();
     76   MachOAllocator.DestroyAll();
     77 
     78   MCSubtargetAllocator.DestroyAll();
     79   UsedNames.clear();
     80   Symbols.clear();
     81   SectionSymbols.clear();
     82   Allocator.Reset();
     83   Instances.clear();
     84   CompilationDir.clear();
     85   MainFileName.clear();
     86   MCDwarfLineTablesCUMap.clear();
     87   SectionsForRanges.clear();
     88   MCGenDwarfLabelEntries.clear();
     89   DwarfDebugFlags = StringRef();
     90   DwarfCompileUnitID = 0;
     91   CurrentDwarfLoc = MCDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0);
     92 
     93   MachOUniquingMap.clear();
     94   ELFUniquingMap.clear();
     95   COFFUniquingMap.clear();
     96 
     97   NextID.clear();
     98   AllowTemporaryLabels = true;
     99   DwarfLocSeen = false;
    100   GenDwarfForAssembly = false;
    101   GenDwarfFileNumber = 0;
    102 
    103   HadError = false;
    104 }
    105 
    106 //===----------------------------------------------------------------------===//
    107 // Symbol Manipulation
    108 //===----------------------------------------------------------------------===//
    109 
    110 MCSymbol *MCContext::getOrCreateSymbol(const Twine &Name) {
    111   SmallString<128> NameSV;
    112   StringRef NameRef = Name.toStringRef(NameSV);
    113 
    114   assert(!NameRef.empty() && "Normal symbols cannot be unnamed!");
    115 
    116   MCSymbol *&Sym = Symbols[NameRef];
    117   if (!Sym)
    118     Sym = createSymbol(NameRef, false, false);
    119 
    120   return Sym;
    121 }
    122 
    123 MCSymbolELF *MCContext::getOrCreateSectionSymbol(const MCSectionELF &Section) {
    124   MCSymbolELF *&Sym = SectionSymbols[&Section];
    125   if (Sym)
    126     return Sym;
    127 
    128   StringRef Name = Section.getSectionName();
    129 
    130   MCSymbol *&OldSym = Symbols[Name];
    131   if (OldSym && OldSym->isUndefined()) {
    132     Sym = cast<MCSymbolELF>(OldSym);
    133     return Sym;
    134   }
    135 
    136   auto NameIter = UsedNames.insert(std::make_pair(Name, true)).first;
    137   Sym = new (&*NameIter, *this) MCSymbolELF(&*NameIter, /*isTemporary*/ false);
    138 
    139   if (!OldSym)
    140     OldSym = Sym;
    141 
    142   return Sym;
    143 }
    144 
    145 MCSymbol *MCContext::getOrCreateFrameAllocSymbol(StringRef FuncName,
    146                                                  unsigned Idx) {
    147   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
    148                            "$frame_escape_" + Twine(Idx));
    149 }
    150 
    151 MCSymbol *MCContext::getOrCreateParentFrameOffsetSymbol(StringRef FuncName) {
    152   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
    153                            "$parent_frame_offset");
    154 }
    155 
    156 MCSymbol *MCContext::getOrCreateLSDASymbol(StringRef FuncName) {
    157   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + "__ehtable$" +
    158                            FuncName);
    159 }
    160 
    161 MCSymbol *MCContext::createSymbolImpl(const StringMapEntry<bool> *Name,
    162                                       bool IsTemporary) {
    163   if (MOFI) {
    164     switch (MOFI->getObjectFileType()) {
    165     case MCObjectFileInfo::IsCOFF:
    166       return new (Name, *this) MCSymbolCOFF(Name, IsTemporary);
    167     case MCObjectFileInfo::IsELF:
    168       return new (Name, *this) MCSymbolELF(Name, IsTemporary);
    169     case MCObjectFileInfo::IsMachO:
    170       return new (Name, *this) MCSymbolMachO(Name, IsTemporary);
    171     }
    172   }
    173   return new (Name, *this) MCSymbol(MCSymbol::SymbolKindUnset, Name,
    174                                     IsTemporary);
    175 }
    176 
    177 MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix,
    178                                   bool CanBeUnnamed) {
    179   if (CanBeUnnamed && !UseNamesOnTempLabels)
    180     return createSymbolImpl(nullptr, true);
    181 
    182   // Determine whether this is an user writter assembler temporary or normal
    183   // label, if used.
    184   bool IsTemporary = CanBeUnnamed;
    185   if (AllowTemporaryLabels && !IsTemporary)
    186     IsTemporary = Name.startswith(MAI->getPrivateGlobalPrefix());
    187 
    188   SmallString<128> NewName = Name;
    189   bool AddSuffix = AlwaysAddSuffix;
    190   unsigned &NextUniqueID = NextID[Name];
    191   for (;;) {
    192     if (AddSuffix) {
    193       NewName.resize(Name.size());
    194       raw_svector_ostream(NewName) << NextUniqueID++;
    195     }
    196     auto NameEntry = UsedNames.insert(std::make_pair(NewName, true));
    197     if (NameEntry.second) {
    198       // Ok, we found a name. Have the MCSymbol object itself refer to the copy
    199       // of the string that is embedded in the UsedNames entry.
    200       return createSymbolImpl(&*NameEntry.first, IsTemporary);
    201     }
    202     assert(IsTemporary && "Cannot rename non-temporary symbols");
    203     AddSuffix = true;
    204   }
    205   llvm_unreachable("Infinite loop");
    206 }
    207 
    208 MCSymbol *MCContext::createTempSymbol(const Twine &Name, bool AlwaysAddSuffix,
    209                                       bool CanBeUnnamed) {
    210   SmallString<128> NameSV;
    211   raw_svector_ostream(NameSV) << MAI->getPrivateGlobalPrefix() << Name;
    212   return createSymbol(NameSV, AlwaysAddSuffix, CanBeUnnamed);
    213 }
    214 
    215 MCSymbol *MCContext::createLinkerPrivateTempSymbol() {
    216   SmallString<128> NameSV;
    217   raw_svector_ostream(NameSV) << MAI->getLinkerPrivateGlobalPrefix() << "tmp";
    218   return createSymbol(NameSV, true, false);
    219 }
    220 
    221 MCSymbol *MCContext::createTempSymbol(bool CanBeUnnamed) {
    222   return createTempSymbol("tmp", true, CanBeUnnamed);
    223 }
    224 
    225 unsigned MCContext::NextInstance(unsigned LocalLabelVal) {
    226   MCLabel *&Label = Instances[LocalLabelVal];
    227   if (!Label)
    228     Label = new (*this) MCLabel(0);
    229   return Label->incInstance();
    230 }
    231 
    232 unsigned MCContext::GetInstance(unsigned LocalLabelVal) {
    233   MCLabel *&Label = Instances[LocalLabelVal];
    234   if (!Label)
    235     Label = new (*this) MCLabel(0);
    236   return Label->getInstance();
    237 }
    238 
    239 MCSymbol *MCContext::getOrCreateDirectionalLocalSymbol(unsigned LocalLabelVal,
    240                                                        unsigned Instance) {
    241   MCSymbol *&Sym = LocalSymbols[std::make_pair(LocalLabelVal, Instance)];
    242   if (!Sym)
    243     Sym = createTempSymbol(false);
    244   return Sym;
    245 }
    246 
    247 MCSymbol *MCContext::createDirectionalLocalSymbol(unsigned LocalLabelVal) {
    248   unsigned Instance = NextInstance(LocalLabelVal);
    249   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
    250 }
    251 
    252 MCSymbol *MCContext::getDirectionalLocalSymbol(unsigned LocalLabelVal,
    253                                                bool Before) {
    254   unsigned Instance = GetInstance(LocalLabelVal);
    255   if (!Before)
    256     ++Instance;
    257   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
    258 }
    259 
    260 MCSymbol *MCContext::lookupSymbol(const Twine &Name) const {
    261   SmallString<128> NameSV;
    262   StringRef NameRef = Name.toStringRef(NameSV);
    263   return Symbols.lookup(NameRef);
    264 }
    265 
    266 //===----------------------------------------------------------------------===//
    267 // Section Management
    268 //===----------------------------------------------------------------------===//
    269 
    270 MCSectionMachO *MCContext::getMachOSection(StringRef Segment, StringRef Section,
    271                                            unsigned TypeAndAttributes,
    272                                            unsigned Reserved2, SectionKind Kind,
    273                                            const char *BeginSymName) {
    274 
    275   // We unique sections by their segment/section pair.  The returned section
    276   // may not have the same flags as the requested section, if so this should be
    277   // diagnosed by the client as an error.
    278 
    279   // Form the name to look up.
    280   SmallString<64> Name;
    281   Name += Segment;
    282   Name.push_back(',');
    283   Name += Section;
    284 
    285   // Do the lookup, if we have a hit, return it.
    286   MCSectionMachO *&Entry = MachOUniquingMap[Name];
    287   if (Entry)
    288     return Entry;
    289 
    290   MCSymbol *Begin = nullptr;
    291   if (BeginSymName)
    292     Begin = createTempSymbol(BeginSymName, false);
    293 
    294   // Otherwise, return a new section.
    295   return Entry = new (MachOAllocator.Allocate()) MCSectionMachO(
    296              Segment, Section, TypeAndAttributes, Reserved2, Kind, Begin);
    297 }
    298 
    299 void MCContext::renameELFSection(MCSectionELF *Section, StringRef Name) {
    300   StringRef GroupName;
    301   if (const MCSymbol *Group = Section->getGroup())
    302     GroupName = Group->getName();
    303 
    304   unsigned UniqueID = Section->getUniqueID();
    305   ELFUniquingMap.erase(
    306       ELFSectionKey{Section->getSectionName(), GroupName, UniqueID});
    307   auto I = ELFUniquingMap.insert(std::make_pair(
    308                                      ELFSectionKey{Name, GroupName, UniqueID},
    309                                      Section))
    310                .first;
    311   StringRef CachedName = I->first.SectionName;
    312   const_cast<MCSectionELF *>(Section)->setSectionName(CachedName);
    313 }
    314 
    315 MCSectionELF *MCContext::createELFRelSection(StringRef Name, unsigned Type,
    316                                              unsigned Flags, unsigned EntrySize,
    317                                              const MCSymbolELF *Group,
    318                                              const MCSectionELF *Associated) {
    319   StringMap<bool>::iterator I;
    320   bool Inserted;
    321   std::tie(I, Inserted) = ELFRelSecNames.insert(std::make_pair(Name, true));
    322 
    323   return new (ELFAllocator.Allocate())
    324       MCSectionELF(I->getKey(), Type, Flags, SectionKind::getReadOnly(),
    325                    EntrySize, Group, true, nullptr, Associated);
    326 }
    327 
    328 MCSectionELF *MCContext::getELFSection(StringRef Section, unsigned Type,
    329                                        unsigned Flags, unsigned EntrySize,
    330                                        StringRef Group, unsigned UniqueID,
    331                                        const char *BeginSymName) {
    332   MCSymbolELF *GroupSym = nullptr;
    333   if (!Group.empty())
    334     GroupSym = cast<MCSymbolELF>(getOrCreateSymbol(Group));
    335 
    336   return getELFSection(Section, Type, Flags, EntrySize, GroupSym, UniqueID,
    337                        BeginSymName, nullptr);
    338 }
    339 
    340 MCSectionELF *MCContext::getELFSection(StringRef Section, unsigned Type,
    341                                        unsigned Flags, unsigned EntrySize,
    342                                        const MCSymbolELF *GroupSym,
    343                                        unsigned UniqueID,
    344                                        const char *BeginSymName,
    345                                        const MCSectionELF *Associated) {
    346   StringRef Group = "";
    347   if (GroupSym)
    348     Group = GroupSym->getName();
    349   // Do the lookup, if we have a hit, return it.
    350   auto IterBool = ELFUniquingMap.insert(
    351       std::make_pair(ELFSectionKey{Section, Group, UniqueID}, nullptr));
    352   auto &Entry = *IterBool.first;
    353   if (!IterBool.second)
    354     return Entry.second;
    355 
    356   StringRef CachedName = Entry.first.SectionName;
    357 
    358   SectionKind Kind;
    359   if (Flags & ELF::SHF_EXECINSTR)
    360     Kind = SectionKind::getText();
    361   else
    362     Kind = SectionKind::getReadOnly();
    363 
    364   MCSymbol *Begin = nullptr;
    365   if (BeginSymName)
    366     Begin = createTempSymbol(BeginSymName, false);
    367 
    368   MCSectionELF *Result = new (ELFAllocator.Allocate())
    369       MCSectionELF(CachedName, Type, Flags, Kind, EntrySize, GroupSym, UniqueID,
    370                    Begin, Associated);
    371   Entry.second = Result;
    372   return Result;
    373 }
    374 
    375 MCSectionELF *MCContext::createELFGroupSection(const MCSymbolELF *Group) {
    376   MCSectionELF *Result = new (ELFAllocator.Allocate())
    377       MCSectionELF(".group", ELF::SHT_GROUP, 0, SectionKind::getReadOnly(), 4,
    378                    Group, ~0, nullptr, nullptr);
    379   return Result;
    380 }
    381 
    382 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
    383                                          unsigned Characteristics,
    384                                          SectionKind Kind,
    385                                          StringRef COMDATSymName, int Selection,
    386                                          const char *BeginSymName) {
    387   MCSymbol *COMDATSymbol = nullptr;
    388   if (!COMDATSymName.empty()) {
    389     COMDATSymbol = getOrCreateSymbol(COMDATSymName);
    390     COMDATSymName = COMDATSymbol->getName();
    391   }
    392 
    393   // Do the lookup, if we have a hit, return it.
    394   COFFSectionKey T{Section, COMDATSymName, Selection};
    395   auto IterBool = COFFUniquingMap.insert(std::make_pair(T, nullptr));
    396   auto Iter = IterBool.first;
    397   if (!IterBool.second)
    398     return Iter->second;
    399 
    400   MCSymbol *Begin = nullptr;
    401   if (BeginSymName)
    402     Begin = createTempSymbol(BeginSymName, false);
    403 
    404   StringRef CachedName = Iter->first.SectionName;
    405   MCSectionCOFF *Result = new (COFFAllocator.Allocate()) MCSectionCOFF(
    406       CachedName, Characteristics, COMDATSymbol, Selection, Kind, Begin);
    407 
    408   Iter->second = Result;
    409   return Result;
    410 }
    411 
    412 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
    413                                          unsigned Characteristics,
    414                                          SectionKind Kind,
    415                                          const char *BeginSymName) {
    416   return getCOFFSection(Section, Characteristics, Kind, "", 0, BeginSymName);
    417 }
    418 
    419 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section) {
    420   COFFSectionKey T{Section, "", 0};
    421   auto Iter = COFFUniquingMap.find(T);
    422   if (Iter == COFFUniquingMap.end())
    423     return nullptr;
    424   return Iter->second;
    425 }
    426 
    427 MCSectionCOFF *MCContext::getAssociativeCOFFSection(MCSectionCOFF *Sec,
    428                                                     const MCSymbol *KeySym) {
    429   // Return the normal section if we don't have to be associative.
    430   if (!KeySym)
    431     return Sec;
    432 
    433   // Make an associative section with the same name and kind as the normal
    434   // section.
    435   unsigned Characteristics =
    436       Sec->getCharacteristics() | COFF::IMAGE_SCN_LNK_COMDAT;
    437   return getCOFFSection(Sec->getSectionName(), Characteristics, Sec->getKind(),
    438                         KeySym->getName(),
    439                         COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
    440 }
    441 
    442 MCSubtargetInfo &MCContext::getSubtargetCopy(const MCSubtargetInfo &STI) {
    443   return *new (MCSubtargetAllocator.Allocate()) MCSubtargetInfo(STI);
    444 }
    445 
    446 //===----------------------------------------------------------------------===//
    447 // Dwarf Management
    448 //===----------------------------------------------------------------------===//
    449 
    450 /// getDwarfFile - takes a file name an number to place in the dwarf file and
    451 /// directory tables.  If the file number has already been allocated it is an
    452 /// error and zero is returned and the client reports the error, else the
    453 /// allocated file number is returned.  The file numbers may be in any order.
    454 unsigned MCContext::getDwarfFile(StringRef Directory, StringRef FileName,
    455                                  unsigned FileNumber, unsigned CUID) {
    456   MCDwarfLineTable &Table = MCDwarfLineTablesCUMap[CUID];
    457   return Table.getFile(Directory, FileName, FileNumber);
    458 }
    459 
    460 /// isValidDwarfFileNumber - takes a dwarf file number and returns true if it
    461 /// currently is assigned and false otherwise.
    462 bool MCContext::isValidDwarfFileNumber(unsigned FileNumber, unsigned CUID) {
    463   const SmallVectorImpl<MCDwarfFile> &MCDwarfFiles = getMCDwarfFiles(CUID);
    464   if (FileNumber == 0 || FileNumber >= MCDwarfFiles.size())
    465     return false;
    466 
    467   return !MCDwarfFiles[FileNumber].Name.empty();
    468 }
    469 
    470 /// Remove empty sections from SectionStartEndSyms, to avoid generating
    471 /// useless debug info for them.
    472 void MCContext::finalizeDwarfSections(MCStreamer &MCOS) {
    473   SectionsForRanges.remove_if(
    474       [&](MCSection *Sec) { return !MCOS.mayHaveInstructions(*Sec); });
    475 }
    476 
    477 //===----------------------------------------------------------------------===//
    478 // Error Reporting
    479 //===----------------------------------------------------------------------===//
    480 
    481 void MCContext::reportError(SMLoc Loc, const Twine &Msg) {
    482   HadError = true;
    483 
    484   // If we have a source manager use it. Otherwise just use the generic
    485   // report_fatal_error().
    486   if (!SrcMgr)
    487     report_fatal_error(Msg, false);
    488 
    489   // Use the source manager to print the message.
    490   SrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
    491 }
    492 
    493 void MCContext::reportFatalError(SMLoc Loc, const Twine &Msg) {
    494   reportError(Loc, Msg);
    495 
    496   // If we reached here, we are failing ungracefully. Run the interrupt handlers
    497   // to make sure any special cleanups get done, in particular that we remove
    498   // files registered with RemoveFileOnSignal.
    499   sys::RunInterruptHandlers();
    500   exit(1);
    501 }
    502