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   // If the stream for the .secure_log_unique directive was created free it.
68   delete (raw_ostream *)SecureLog;
69 }
70 
71 //===----------------------------------------------------------------------===//
72 // Module Lifetime Management
73 //===----------------------------------------------------------------------===//
74 
75 void MCContext::reset() {
76   // Call the destructors so the fragments are freed
77   COFFAllocator.DestroyAll();
78   ELFAllocator.DestroyAll();
79   MachOAllocator.DestroyAll();
80 
81   MCSubtargetAllocator.DestroyAll();
82   UsedNames.clear();
83   Symbols.clear();
84   SectionSymbols.clear();
85   Allocator.Reset();
86   Instances.clear();
87   CompilationDir.clear();
88   MainFileName.clear();
89   MCDwarfLineTablesCUMap.clear();
90   SectionsForRanges.clear();
91   MCGenDwarfLabelEntries.clear();
92   DwarfDebugFlags = StringRef();
93   DwarfCompileUnitID = 0;
94   CurrentDwarfLoc = MCDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0);
95 
96   MachOUniquingMap.clear();
97   ELFUniquingMap.clear();
98   COFFUniquingMap.clear();
99 
100   NextID.clear();
101   AllowTemporaryLabels = true;
102   DwarfLocSeen = false;
103   GenDwarfForAssembly = false;
104   GenDwarfFileNumber = 0;
105 
106   HadError = false;
107 }
108 
109 //===----------------------------------------------------------------------===//
110 // Symbol Manipulation
111 //===----------------------------------------------------------------------===//
112 
113 MCSymbol *MCContext::getOrCreateSymbol(const Twine &Name) {
114   SmallString<128> NameSV;
115   StringRef NameRef = Name.toStringRef(NameSV);
116 
117   assert(!NameRef.empty() && "Normal symbols cannot be unnamed!");
118 
119   MCSymbol *&Sym = Symbols[NameRef];
120   if (!Sym)
121     Sym = createSymbol(NameRef, false, false);
122 
123   return Sym;
124 }
125 
126 MCSymbolELF *MCContext::getOrCreateSectionSymbol(const MCSectionELF &Section) {
127   MCSymbolELF *&Sym = SectionSymbols[&Section];
128   if (Sym)
129     return Sym;
130 
131   StringRef Name = Section.getSectionName();
132 
133   MCSymbol *&OldSym = Symbols[Name];
134   if (OldSym && OldSym->isUndefined()) {
135     Sym = cast<MCSymbolELF>(OldSym);
136     return Sym;
137   }
138 
139   auto NameIter = UsedNames.insert(std::make_pair(Name, true)).first;
140   Sym = new (&*NameIter, *this) MCSymbolELF(&*NameIter, /*isTemporary*/ false);
141 
142   if (!OldSym)
143     OldSym = Sym;
144 
145   return Sym;
146 }
147 
148 MCSymbol *MCContext::getOrCreateFrameAllocSymbol(StringRef FuncName,
149                                                  unsigned Idx) {
150   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
151                            "$frame_escape_" + Twine(Idx));
152 }
153 
154 MCSymbol *MCContext::getOrCreateParentFrameOffsetSymbol(StringRef FuncName) {
155   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
156                            "$parent_frame_offset");
157 }
158 
159 MCSymbol *MCContext::getOrCreateLSDASymbol(StringRef FuncName) {
160   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + "__ehtable$" +
161                            FuncName);
162 }
163 
164 MCSymbol *MCContext::createSymbolImpl(const StringMapEntry<bool> *Name,
165                                       bool IsTemporary) {
166   if (MOFI) {
167     switch (MOFI->getObjectFileType()) {
168     case MCObjectFileInfo::IsCOFF:
169       return new (Name, *this) MCSymbolCOFF(Name, IsTemporary);
170     case MCObjectFileInfo::IsELF:
171       return new (Name, *this) MCSymbolELF(Name, IsTemporary);
172     case MCObjectFileInfo::IsMachO:
173       return new (Name, *this) MCSymbolMachO(Name, IsTemporary);
174     }
175   }
176   return new (Name, *this) MCSymbol(MCSymbol::SymbolKindUnset, Name,
177                                     IsTemporary);
178 }
179 
180 MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix,
181                                   bool CanBeUnnamed) {
182   if (CanBeUnnamed && !UseNamesOnTempLabels)
183     return createSymbolImpl(nullptr, true);
184 
185   // Determine whether this is an user writter assembler temporary or normal
186   // label, if used.
187   bool IsTemporary = CanBeUnnamed;
188   if (AllowTemporaryLabels && !IsTemporary)
189     IsTemporary = Name.startswith(MAI->getPrivateGlobalPrefix());
190 
191   SmallString<128> NewName = Name;
192   bool AddSuffix = AlwaysAddSuffix;
193   unsigned &NextUniqueID = NextID[Name];
194   for (;;) {
195     if (AddSuffix) {
196       NewName.resize(Name.size());
197       raw_svector_ostream(NewName) << NextUniqueID++;
198     }
199     auto NameEntry = UsedNames.insert(std::make_pair(NewName, true));
200     if (NameEntry.second) {
201       // Ok, we found a name. Have the MCSymbol object itself refer to the copy
202       // of the string that is embedded in the UsedNames entry.
203       return createSymbolImpl(&*NameEntry.first, IsTemporary);
204     }
205     assert(IsTemporary && "Cannot rename non-temporary symbols");
206     AddSuffix = true;
207   }
208   llvm_unreachable("Infinite loop");
209 }
210 
211 MCSymbol *MCContext::createTempSymbol(const Twine &Name, bool AlwaysAddSuffix,
212                                       bool CanBeUnnamed) {
213   SmallString<128> NameSV;
214   raw_svector_ostream(NameSV) << MAI->getPrivateGlobalPrefix() << Name;
215   return createSymbol(NameSV, AlwaysAddSuffix, CanBeUnnamed);
216 }
217 
218 MCSymbol *MCContext::createLinkerPrivateTempSymbol() {
219   SmallString<128> NameSV;
220   raw_svector_ostream(NameSV) << MAI->getLinkerPrivateGlobalPrefix() << "tmp";
221   return createSymbol(NameSV, true, false);
222 }
223 
224 MCSymbol *MCContext::createTempSymbol(bool CanBeUnnamed) {
225   return createTempSymbol("tmp", true, CanBeUnnamed);
226 }
227 
228 unsigned MCContext::NextInstance(unsigned LocalLabelVal) {
229   MCLabel *&Label = Instances[LocalLabelVal];
230   if (!Label)
231     Label = new (*this) MCLabel(0);
232   return Label->incInstance();
233 }
234 
235 unsigned MCContext::GetInstance(unsigned LocalLabelVal) {
236   MCLabel *&Label = Instances[LocalLabelVal];
237   if (!Label)
238     Label = new (*this) MCLabel(0);
239   return Label->getInstance();
240 }
241 
242 MCSymbol *MCContext::getOrCreateDirectionalLocalSymbol(unsigned LocalLabelVal,
243                                                        unsigned Instance) {
244   MCSymbol *&Sym = LocalSymbols[std::make_pair(LocalLabelVal, Instance)];
245   if (!Sym)
246     Sym = createTempSymbol(false);
247   return Sym;
248 }
249 
250 MCSymbol *MCContext::createDirectionalLocalSymbol(unsigned LocalLabelVal) {
251   unsigned Instance = NextInstance(LocalLabelVal);
252   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
253 }
254 
255 MCSymbol *MCContext::getDirectionalLocalSymbol(unsigned LocalLabelVal,
256                                                bool Before) {
257   unsigned Instance = GetInstance(LocalLabelVal);
258   if (!Before)
259     ++Instance;
260   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
261 }
262 
263 MCSymbol *MCContext::lookupSymbol(const Twine &Name) const {
264   SmallString<128> NameSV;
265   StringRef NameRef = Name.toStringRef(NameSV);
266   return Symbols.lookup(NameRef);
267 }
268 
269 //===----------------------------------------------------------------------===//
270 // Section Management
271 //===----------------------------------------------------------------------===//
272 
273 MCSectionMachO *MCContext::getMachOSection(StringRef Segment, StringRef Section,
274                                            unsigned TypeAndAttributes,
275                                            unsigned Reserved2, SectionKind Kind,
276                                            const char *BeginSymName) {
277 
278   // We unique sections by their segment/section pair.  The returned section
279   // may not have the same flags as the requested section, if so this should be
280   // diagnosed by the client as an error.
281 
282   // Form the name to look up.
283   SmallString<64> Name;
284   Name += Segment;
285   Name.push_back(',');
286   Name += Section;
287 
288   // Do the lookup, if we have a hit, return it.
289   MCSectionMachO *&Entry = MachOUniquingMap[Name];
290   if (Entry)
291     return Entry;
292 
293   MCSymbol *Begin = nullptr;
294   if (BeginSymName)
295     Begin = createTempSymbol(BeginSymName, false);
296 
297   // Otherwise, return a new section.
298   return Entry = new (MachOAllocator.Allocate()) MCSectionMachO(
299              Segment, Section, TypeAndAttributes, Reserved2, Kind, Begin);
300 }
301 
302 void MCContext::renameELFSection(MCSectionELF *Section, StringRef Name) {
303   StringRef GroupName;
304   if (const MCSymbol *Group = Section->getGroup())
305     GroupName = Group->getName();
306 
307   unsigned UniqueID = Section->getUniqueID();
308   ELFUniquingMap.erase(
309       ELFSectionKey{Section->getSectionName(), GroupName, UniqueID});
310   auto I = ELFUniquingMap.insert(std::make_pair(
311                                      ELFSectionKey{Name, GroupName, UniqueID},
312                                      Section))
313                .first;
314   StringRef CachedName = I->first.SectionName;
315   const_cast<MCSectionELF *>(Section)->setSectionName(CachedName);
316 }
317 
318 MCSectionELF *MCContext::createELFRelSection(StringRef Name, unsigned Type,
319                                              unsigned Flags, unsigned EntrySize,
320                                              const MCSymbolELF *Group,
321                                              const MCSectionELF *Associated) {
322   StringMap<bool>::iterator I;
323   bool Inserted;
324   std::tie(I, Inserted) = ELFRelSecNames.insert(std::make_pair(Name, true));
325 
326   return new (ELFAllocator.Allocate())
327       MCSectionELF(I->getKey(), Type, Flags, SectionKind::getReadOnly(),
328                    EntrySize, Group, true, nullptr, Associated);
329 }
330 
331 MCSectionELF *MCContext::getELFSection(StringRef Section, unsigned Type,
332                                        unsigned Flags, unsigned EntrySize,
333                                        StringRef Group, unsigned UniqueID,
334                                        const char *BeginSymName) {
335   MCSymbolELF *GroupSym = nullptr;
336   if (!Group.empty())
337     GroupSym = cast<MCSymbolELF>(getOrCreateSymbol(Group));
338 
339   return getELFSection(Section, Type, Flags, EntrySize, GroupSym, UniqueID,
340                        BeginSymName, nullptr);
341 }
342 
343 MCSectionELF *MCContext::getELFSection(StringRef Section, unsigned Type,
344                                        unsigned Flags, unsigned EntrySize,
345                                        const MCSymbolELF *GroupSym,
346                                        unsigned UniqueID,
347                                        const char *BeginSymName,
348                                        const MCSectionELF *Associated) {
349   StringRef Group = "";
350   if (GroupSym)
351     Group = GroupSym->getName();
352   // Do the lookup, if we have a hit, return it.
353   auto IterBool = ELFUniquingMap.insert(
354       std::make_pair(ELFSectionKey{Section, Group, UniqueID}, nullptr));
355   auto &Entry = *IterBool.first;
356   if (!IterBool.second)
357     return Entry.second;
358 
359   StringRef CachedName = Entry.first.SectionName;
360 
361   SectionKind Kind;
362   if (Flags & ELF::SHF_EXECINSTR)
363     Kind = SectionKind::getText();
364   else
365     Kind = SectionKind::getReadOnly();
366 
367   MCSymbol *Begin = nullptr;
368   if (BeginSymName)
369     Begin = createTempSymbol(BeginSymName, false);
370 
371   MCSectionELF *Result = new (ELFAllocator.Allocate())
372       MCSectionELF(CachedName, Type, Flags, Kind, EntrySize, GroupSym, UniqueID,
373                    Begin, Associated);
374   Entry.second = Result;
375   return Result;
376 }
377 
378 MCSectionELF *MCContext::createELFGroupSection(const MCSymbolELF *Group) {
379   MCSectionELF *Result = new (ELFAllocator.Allocate())
380       MCSectionELF(".group", ELF::SHT_GROUP, 0, SectionKind::getReadOnly(), 4,
381                    Group, ~0, nullptr, nullptr);
382   return Result;
383 }
384 
385 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
386                                          unsigned Characteristics,
387                                          SectionKind Kind,
388                                          StringRef COMDATSymName, int Selection,
389                                          const char *BeginSymName) {
390   MCSymbol *COMDATSymbol = nullptr;
391   if (!COMDATSymName.empty()) {
392     COMDATSymbol = getOrCreateSymbol(COMDATSymName);
393     COMDATSymName = COMDATSymbol->getName();
394   }
395 
396   // Do the lookup, if we have a hit, return it.
397   COFFSectionKey T{Section, COMDATSymName, Selection};
398   auto IterBool = COFFUniquingMap.insert(std::make_pair(T, nullptr));
399   auto Iter = IterBool.first;
400   if (!IterBool.second)
401     return Iter->second;
402 
403   MCSymbol *Begin = nullptr;
404   if (BeginSymName)
405     Begin = createTempSymbol(BeginSymName, false);
406 
407   StringRef CachedName = Iter->first.SectionName;
408   MCSectionCOFF *Result = new (COFFAllocator.Allocate()) MCSectionCOFF(
409       CachedName, Characteristics, COMDATSymbol, Selection, Kind, Begin);
410 
411   Iter->second = Result;
412   return Result;
413 }
414 
415 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
416                                          unsigned Characteristics,
417                                          SectionKind Kind,
418                                          const char *BeginSymName) {
419   return getCOFFSection(Section, Characteristics, Kind, "", 0, BeginSymName);
420 }
421 
422 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section) {
423   COFFSectionKey T{Section, "", 0};
424   auto Iter = COFFUniquingMap.find(T);
425   if (Iter == COFFUniquingMap.end())
426     return nullptr;
427   return Iter->second;
428 }
429 
430 MCSectionCOFF *MCContext::getAssociativeCOFFSection(MCSectionCOFF *Sec,
431                                                     const MCSymbol *KeySym) {
432   // Return the normal section if we don't have to be associative.
433   if (!KeySym)
434     return Sec;
435 
436   // Make an associative section with the same name and kind as the normal
437   // section.
438   unsigned Characteristics =
439       Sec->getCharacteristics() | COFF::IMAGE_SCN_LNK_COMDAT;
440   return getCOFFSection(Sec->getSectionName(), Characteristics, Sec->getKind(),
441                         KeySym->getName(),
442                         COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
443 }
444 
445 MCSubtargetInfo &MCContext::getSubtargetCopy(const MCSubtargetInfo &STI) {
446   return *new (MCSubtargetAllocator.Allocate()) MCSubtargetInfo(STI);
447 }
448 
449 //===----------------------------------------------------------------------===//
450 // Dwarf Management
451 //===----------------------------------------------------------------------===//
452 
453 /// getDwarfFile - takes a file name an number to place in the dwarf file and
454 /// directory tables.  If the file number has already been allocated it is an
455 /// error and zero is returned and the client reports the error, else the
456 /// allocated file number is returned.  The file numbers may be in any order.
457 unsigned MCContext::getDwarfFile(StringRef Directory, StringRef FileName,
458                                  unsigned FileNumber, unsigned CUID) {
459   MCDwarfLineTable &Table = MCDwarfLineTablesCUMap[CUID];
460   return Table.getFile(Directory, FileName, FileNumber);
461 }
462 
463 /// isValidDwarfFileNumber - takes a dwarf file number and returns true if it
464 /// currently is assigned and false otherwise.
465 bool MCContext::isValidDwarfFileNumber(unsigned FileNumber, unsigned CUID) {
466   const SmallVectorImpl<MCDwarfFile> &MCDwarfFiles = getMCDwarfFiles(CUID);
467   if (FileNumber == 0 || FileNumber >= MCDwarfFiles.size())
468     return false;
469 
470   return !MCDwarfFiles[FileNumber].Name.empty();
471 }
472 
473 /// Remove empty sections from SectionStartEndSyms, to avoid generating
474 /// useless debug info for them.
475 void MCContext::finalizeDwarfSections(MCStreamer &MCOS) {
476   SectionsForRanges.remove_if(
477       [&](MCSection *Sec) { return !MCOS.mayHaveInstructions(*Sec); });
478 }
479 
480 //===----------------------------------------------------------------------===//
481 // Error Reporting
482 //===----------------------------------------------------------------------===//
483 
484 void MCContext::reportError(SMLoc Loc, const Twine &Msg) {
485   HadError = true;
486 
487   // If we have a source manager use it. Otherwise just use the generic
488   // report_fatal_error().
489   if (!SrcMgr)
490     report_fatal_error(Msg, false);
491 
492   // Use the source manager to print the message.
493   SrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
494 }
495 
496 void MCContext::reportFatalError(SMLoc Loc, const Twine &Msg) {
497   reportError(Loc, Msg);
498 
499   // If we reached here, we are failing ungracefully. Run the interrupt handlers
500   // to make sure any special cleanups get done, in particular that we remove
501   // files registered with RemoveFileOnSignal.
502   sys::RunInterruptHandlers();
503   exit(1);
504 }
505