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