llvm/lib/MC/MCWinCOFFStreamer.cpp

   1 //===- llvm/MC/MCWinCOFFStreamer.cpp --------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file contains an implementation of a Windows COFF object file streamer.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/MC/MCWinCOFFStreamer.h"
  14 #include "llvm/ADT/SmallString.h"
  15 #include "llvm/ADT/SmallVector.h"
  16 #include "llvm/ADT/Twine.h"
  17 #include "llvm/BinaryFormat/COFF.h"
  18 #include "llvm/MC/MCAsmBackend.h"
  19 #include "llvm/MC/MCAssembler.h"
  20 #include "llvm/MC/MCCodeEmitter.h"
  21 #include "llvm/MC/MCContext.h"
  22 #include "llvm/MC/MCExpr.h"
  23 #include "llvm/MC/MCFixup.h"
  24 #include "llvm/MC/MCFragment.h"
  25 #include "llvm/MC/MCObjectFileInfo.h"
  26 #include "llvm/MC/MCObjectStreamer.h"
  27 #include "llvm/MC/MCObjectWriter.h"
  28 #include "llvm/MC/MCSectionCOFF.h"
  29 #include "llvm/MC/MCSymbolCOFF.h"
  30 #include "llvm/MC/MCTargetOptions.h"
  31 #include "llvm/MC/MCWinCOFFObjectWriter.h"
  32 #include "llvm/Support/Casting.h"
  33 #include "llvm/Support/ErrorHandling.h"
  34 #include "llvm/Support/MathExtras.h"
  35 #include "llvm/Support/SMLoc.h"
  36 #include "llvm/Support/raw_ostream.h"
  37 #include "llvm/TargetParser/Triple.h"
  38 #include <algorithm>
  39 #include <cstdint>
  40
  41 using namespace llvm;
  42
  43 #define DEBUG_TYPE "WinCOFFStreamer"
  44
  45 MCWinCOFFStreamer::MCWinCOFFStreamer(MCContext &Context,
  46                                      std::unique_ptr<MCAsmBackend> MAB,
  47                                      std::unique_ptr<MCCodeEmitter> CE,
  48                                      std::unique_ptr<MCObjectWriter> OW)
  49     : MCObjectStreamer(Context, std::move(MAB), std::move(OW), std::move(CE)),
  50       CurSymbol(nullptr) {
  51   auto *TO = Context.getTargetOptions();
  52   if (TO && TO->MCIncrementalLinkerCompatible)
  53     getWriter().setIncrementalLinkerCompatible(true);
  54 }
  55
  56 WinCOFFObjectWriter &MCWinCOFFStreamer::getWriter() {
  57   return static_cast<WinCOFFObjectWriter &>(getAssembler().getWriter());
  58 }
  59
  60 void MCWinCOFFStreamer::emitInstToData(const MCInst &Inst,
  61                                        const MCSubtargetInfo &STI) {
  62   MCDataFragment *DF = getOrCreateDataFragment();
  63
  64   SmallVector<MCFixup, 4> Fixups;
  65   SmallString<256> Code;
  66   getAssembler().getEmitter().encodeInstruction(Inst, Code, Fixups, STI);
  67
  68   // Add the fixups and data.
  69   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
  70     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
  71     DF->getFixups().push_back(Fixups[i]);
  72   }
  73   DF->setHasInstructions(STI);
  74   DF->getContents().append(Code.begin(), Code.end());
  75 }
  76
  77 void MCWinCOFFStreamer::initSections(bool NoExecStack,
  78                                      const MCSubtargetInfo &STI) {
  79   // FIXME: this is identical to the ELF one.
  80   // This emulates the same behavior of GNU as. This makes it easier
  81   // to compare the output as the major sections are in the same order.
  82   switchSection(getContext().getObjectFileInfo()->getTextSection());
  83   emitCodeAlignment(Align(4), &STI);
  84
  85   switchSection(getContext().getObjectFileInfo()->getDataSection());
  86   emitCodeAlignment(Align(4), &STI);
  87
  88   switchSection(getContext().getObjectFileInfo()->getBSSSection());
  89   emitCodeAlignment(Align(4), &STI);
  90
  91   switchSection(getContext().getObjectFileInfo()->getTextSection());
  92 }
  93
  94 void MCWinCOFFStreamer::changeSection(MCSection *Section, uint32_t Subsection) {
  95   changeSectionImpl(Section, Subsection);
  96   // Ensure that the first and the second symbols relative to the section are
  97   // the section symbol and the COMDAT symbol.
  98   getAssembler().registerSymbol(*Section->getBeginSymbol());
  99   if (auto *Sym = cast<MCSectionCOFF>(Section)->getCOMDATSymbol())
 100     getAssembler().registerSymbol(*Sym);
 101 }
 102
 103 void MCWinCOFFStreamer::emitLabel(MCSymbol *S, SMLoc Loc) {
 104   auto *Symbol = cast<MCSymbolCOFF>(S);
 105   MCObjectStreamer::emitLabel(Symbol, Loc);
 106 }
 107
 108 void MCWinCOFFStreamer::emitAssemblerFlag(MCAssemblerFlag Flag) {
 109   // Let the target do whatever target specific stuff it needs to do.
 110   getAssembler().getBackend().handleAssemblerFlag(Flag);
 111
 112   switch (Flag) {
 113   // None of these require COFF specific handling.
 114   case MCAF_SyntaxUnified:
 115   case MCAF_Code16:
 116   case MCAF_Code32:
 117   case MCAF_Code64:
 118     break;
 119   case MCAF_SubsectionsViaSymbols:
 120     llvm_unreachable("COFF doesn't support .subsections_via_symbols");
 121   }
 122 }
 123
 124 void MCWinCOFFStreamer::emitThumbFunc(MCSymbol *Func) {
 125   llvm_unreachable("not implemented");
 126 }
 127
 128 bool MCWinCOFFStreamer::emitSymbolAttribute(MCSymbol *S,
 129                                             MCSymbolAttr Attribute) {
 130   auto *Symbol = cast<MCSymbolCOFF>(S);
 131   getAssembler().registerSymbol(*Symbol);
 132
 133   switch (Attribute) {
 134   default: return false;
 135   case MCSA_WeakReference:
 136   case MCSA_Weak:
 137     Symbol->setWeakExternalCharacteristics(COFF::IMAGE_WEAK_EXTERN_SEARCH_ALIAS);
 138     Symbol->setExternal(true);
 139     break;
 140   case MCSA_WeakAntiDep:
 141     Symbol->setWeakExternalCharacteristics(COFF::IMAGE_WEAK_EXTERN_ANTI_DEPENDENCY);
 142     Symbol->setExternal(true);
 143     Symbol->setIsWeakExternal(true);
 144     break;
 145   case MCSA_Global:
 146     Symbol->setExternal(true);
 147     break;
 148   case MCSA_AltEntry:
 149     llvm_unreachable("COFF doesn't support the .alt_entry attribute");
 150   }
 151
 152   return true;
 153 }
 154
 155 void MCWinCOFFStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
 156   llvm_unreachable("not implemented");
 157 }
 158
 159 void MCWinCOFFStreamer::beginCOFFSymbolDef(MCSymbol const *S) {
 160   auto *Symbol = cast<MCSymbolCOFF>(S);
 161   if (CurSymbol)
 162     Error("starting a new symbol definition without completing the "
 163           "previous one");
 164   CurSymbol = Symbol;
 165 }
 166
 167 void MCWinCOFFStreamer::emitCOFFSymbolStorageClass(int StorageClass) {
 168   if (!CurSymbol) {
 169     Error("storage class specified outside of symbol definition");
 170     return;
 171   }
 172
 173   if (StorageClass & ~COFF::SSC_Invalid) {
 174     Error("storage class value '" + Twine(StorageClass) +
 175                "' out of range");
 176     return;
 177   }
 178
 179   getAssembler().registerSymbol(*CurSymbol);
 180   cast<MCSymbolCOFF>(CurSymbol)->setClass((uint16_t)StorageClass);
 181 }
 182
 183 void MCWinCOFFStreamer::emitCOFFSymbolType(int Type) {
 184   if (!CurSymbol) {
 185     Error("symbol type specified outside of a symbol definition");
 186     return;
 187   }
 188
 189   if (Type & ~0xffff) {
 190     Error("type value '" + Twine(Type) + "' out of range");
 191     return;
 192   }
 193
 194   getAssembler().registerSymbol(*CurSymbol);
 195   cast<MCSymbolCOFF>(CurSymbol)->setType((uint16_t)Type);
 196 }
 197
 198 void MCWinCOFFStreamer::endCOFFSymbolDef() {
 199   if (!CurSymbol)
 200     Error("ending symbol definition without starting one");
 201   CurSymbol = nullptr;
 202 }
 203
 204 void MCWinCOFFStreamer::emitCOFFSafeSEH(MCSymbol const *Symbol) {
 205   // SafeSEH is a feature specific to 32-bit x86.  It does not exist (and is
 206   // unnecessary) on all platforms which use table-based exception dispatch.
 207   if (getContext().getTargetTriple().getArch() != Triple::x86)
 208     return;
 209
 210   const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Symbol);
 211   if (CSymbol->isSafeSEH())
 212     return;
 213
 214   MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection();
 215   changeSection(SXData);
 216   SXData->ensureMinAlignment(Align(4));
 217
 218   insert(getContext().allocFragment<MCSymbolIdFragment>(Symbol));
 219   getAssembler().registerSymbol(*Symbol);
 220   CSymbol->setIsSafeSEH();
 221
 222   // The Microsoft linker requires that the symbol type of a handler be
 223   // function. Go ahead and oblige it here.
 224   CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
 225                    << COFF::SCT_COMPLEX_TYPE_SHIFT);
 226 }
 227
 228 void MCWinCOFFStreamer::emitCOFFSymbolIndex(MCSymbol const *Symbol) {
 229   MCSection *Sec = getCurrentSectionOnly();
 230   Sec->ensureMinAlignment(Align(4));
 231
 232   insert(getContext().allocFragment<MCSymbolIdFragment>(Symbol));
 233   getAssembler().registerSymbol(*Symbol);
 234 }
 235
 236 void MCWinCOFFStreamer::emitCOFFSectionIndex(const MCSymbol *Symbol) {
 237   visitUsedSymbol(*Symbol);
 238   MCDataFragment *DF = getOrCreateDataFragment();
 239   const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
 240   MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2);
 241   DF->getFixups().push_back(Fixup);
 242   DF->getContents().resize(DF->getContents().size() + 2, 0);
 243 }
 244
 245 void MCWinCOFFStreamer::emitCOFFSecRel32(const MCSymbol *Symbol,
 246                                          uint64_t Offset) {
 247   visitUsedSymbol(*Symbol);
 248   MCDataFragment *DF = getOrCreateDataFragment();
 249   // Create Symbol A for the relocation relative reference.
 250   const MCExpr *MCE = MCSymbolRefExpr::create(Symbol, getContext());
 251   // Add the constant offset, if given.
 252   if (Offset)
 253     MCE = MCBinaryExpr::createAdd(
 254         MCE, MCConstantExpr::create(Offset, getContext()), getContext());
 255   // Build the secrel32 relocation.
 256   MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_SecRel_4);
 257   // Record the relocation.
 258   DF->getFixups().push_back(Fixup);
 259   // Emit 4 bytes (zeros) to the object file.
 260   DF->getContents().resize(DF->getContents().size() + 4, 0);
 261 }
 262
 263 void MCWinCOFFStreamer::emitCOFFImgRel32(const MCSymbol *Symbol,
 264                                          int64_t Offset) {
 265   visitUsedSymbol(*Symbol);
 266   MCDataFragment *DF = getOrCreateDataFragment();
 267   // Create Symbol A for the relocation relative reference.
 268   const MCExpr *MCE = MCSymbolRefExpr::create(
 269       Symbol, MCSymbolRefExpr::VK_COFF_IMGREL32, getContext());
 270   // Add the constant offset, if given.
 271   if (Offset)
 272     MCE = MCBinaryExpr::createAdd(
 273         MCE, MCConstantExpr::create(Offset, getContext()), getContext());
 274   // Build the imgrel relocation.
 275   MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_Data_4);
 276   // Record the relocation.
 277   DF->getFixups().push_back(Fixup);
 278   // Emit 4 bytes (zeros) to the object file.
 279   DF->getContents().resize(DF->getContents().size() + 4, 0);
 280 }
 281
 282 void MCWinCOFFStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
 283                                          Align ByteAlignment) {
 284   auto *Symbol = cast<MCSymbolCOFF>(S);
 285
 286   const Triple &T = getContext().getTargetTriple();
 287   if (T.isWindowsMSVCEnvironment()) {
 288     if (ByteAlignment > 32)
 289       report_fatal_error("alignment is limited to 32-bytes");
 290
 291     // Round size up to alignment so that we will honor the alignment request.
 292     Size = std::max(Size, ByteAlignment.value());
 293   }
 294
 295   getAssembler().registerSymbol(*Symbol);
 296   Symbol->setExternal(true);
 297   Symbol->setCommon(Size, ByteAlignment);
 298
 299   if (!T.isWindowsMSVCEnvironment() && ByteAlignment > 1) {
 300     SmallString<128> Directive;
 301     raw_svector_ostream OS(Directive);
 302     const MCObjectFileInfo *MFI = getContext().getObjectFileInfo();
 303
 304     OS << " -aligncomm:\"" << Symbol->getName() << "\","
 305        << Log2_32_Ceil(ByteAlignment.value());
 306
 307     pushSection();
 308     switchSection(MFI->getDrectveSection());
 309     emitBytes(Directive);
 310     popSection();
 311   }
 312 }
 313
 314 void MCWinCOFFStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
 315                                               Align ByteAlignment) {
 316   auto *Symbol = cast<MCSymbolCOFF>(S);
 317
 318   MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
 319   pushSection();
 320   switchSection(Section);
 321   emitValueToAlignment(ByteAlignment, 0, 1, 0);
 322   emitLabel(Symbol);
 323   Symbol->setExternal(false);
 324   emitZeros(Size);
 325   popSection();
 326 }
 327
 328 void MCWinCOFFStreamer::emitWeakReference(MCSymbol *AliasS,
 329                                           const MCSymbol *Symbol) {
 330   auto *Alias = cast<MCSymbolCOFF>(AliasS);
 331   emitSymbolAttribute(Alias, MCSA_Weak);
 332
 333   getAssembler().registerSymbol(*Symbol);
 334   Alias->setVariableValue(MCSymbolRefExpr::create(
 335       Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext()));
 336 }
 337
 338 void MCWinCOFFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
 339                                      uint64_t Size, Align ByteAlignment,
 340                                      SMLoc Loc) {
 341   llvm_unreachable("not implemented");
 342 }
 343
 344 void MCWinCOFFStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
 345                                        uint64_t Size, Align ByteAlignment) {
 346   llvm_unreachable("not implemented");
 347 }
 348
 349 // TODO: Implement this if you want to emit .comment section in COFF obj files.
 350 void MCWinCOFFStreamer::emitIdent(StringRef IdentString) {
 351   llvm_unreachable("not implemented");
 352 }
 353
 354 void MCWinCOFFStreamer::emitWinEHHandlerData(SMLoc Loc) {
 355   llvm_unreachable("not implemented");
 356 }
 357
 358 void MCWinCOFFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
 359                                            const MCSymbolRefExpr *To,
 360                                            uint64_t Count) {
 361   // Ignore temporary symbols for now.
 362   if (!From->getSymbol().isTemporary() && !To->getSymbol().isTemporary())
 363     getWriter().getCGProfile().push_back({From, To, Count});
 364 }
 365
 366 void MCWinCOFFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
 367   const MCSymbol *S = &SRE->getSymbol();
 368   if (getAssembler().registerSymbol(*S))
 369     cast<MCSymbolCOFF>(S)->setExternal(true);
 370 }
 371
 372 void MCWinCOFFStreamer::finishImpl() {
 373   MCAssembler &Asm = getAssembler();
 374   if (Asm.getWriter().getEmitAddrsigSection()) {
 375     // Register the section.
 376     switchSection(Asm.getContext().getCOFFSection(".llvm_addrsig",
 377                                                   COFF::IMAGE_SCN_LNK_REMOVE));
 378   }
 379   if (!Asm.getWriter().getCGProfile().empty()) {
 380     for (auto &E : Asm.getWriter().getCGProfile()) {
 381       finalizeCGProfileEntry(E.From);
 382       finalizeCGProfileEntry(E.To);
 383     }
 384     switchSection(Asm.getContext().getCOFFSection(".llvm.call-graph-profile",
 385                                                   COFF::IMAGE_SCN_LNK_REMOVE));
 386   }
 387
 388   MCObjectStreamer::finishImpl();
 389 }
 390
 391 void MCWinCOFFStreamer::Error(const Twine &Msg) const {
 392   getContext().reportError(SMLoc(), Msg);
 393 }