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