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/ADT/SmallString.h"
  14 #include "llvm/ADT/SmallVector.h"
  15 #include "llvm/ADT/Triple.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/MC/MCWinCOFFStreamer.h"
  31 #include "llvm/Support/Casting.h"
  32 #include "llvm/Support/ErrorHandling.h"
  33 #include "llvm/Support/MathExtras.h"
  34 #include "llvm/Support/SMLoc.h"
  35 #include "llvm/Support/raw_ostream.h"
  36 #include <algorithm>
  37 #include <cassert>
  38 #include <cstdint>
  39
  40 using namespace llvm;
  41
  42 #define DEBUG_TYPE "WinCOFFStreamer"
  43
  44 MCWinCOFFStreamer::MCWinCOFFStreamer(MCContext &Context,
  45                                      std::unique_ptr<MCAsmBackend> MAB,
  46                                      std::unique_ptr<MCCodeEmitter> CE,
  47                                      std::unique_ptr<MCObjectWriter> OW)
  48     : MCObjectStreamer(Context, std::move(MAB), std::move(OW), std::move(CE)),
  49       CurSymbol(nullptr) {}
  50
  51 void MCWinCOFFStreamer::emitInstToData(const MCInst &Inst,
  52                                        const MCSubtargetInfo &STI) {
  53   MCDataFragment *DF = getOrCreateDataFragment();
  54
  55   SmallVector<MCFixup, 4> Fixups;
  56   SmallString<256> Code;
  57   raw_svector_ostream VecOS(Code);
  58   getAssembler().getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
  59
  60   // Add the fixups and data.
  61   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
  62     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
  63     DF->getFixups().push_back(Fixups[i]);
  64   }
  65   DF->setHasInstructions(STI);
  66   DF->getContents().append(Code.begin(), Code.end());
  67 }
  68
  69 void MCWinCOFFStreamer::initSections(bool NoExecStack,
  70                                      const MCSubtargetInfo &STI) {
  71   // FIXME: this is identical to the ELF one.
  72   // This emulates the same behavior of GNU as. This makes it easier
  73   // to compare the output as the major sections are in the same order.
  74   SwitchSection(getContext().getObjectFileInfo()->getTextSection());
  75   emitCodeAlignment(4, &STI);
  76
  77   SwitchSection(getContext().getObjectFileInfo()->getDataSection());
  78   emitCodeAlignment(4, &STI);
  79
  80   SwitchSection(getContext().getObjectFileInfo()->getBSSSection());
  81   emitCodeAlignment(4, &STI);
  82
  83   SwitchSection(getContext().getObjectFileInfo()->getTextSection());
  84 }
  85
  86 void MCWinCOFFStreamer::emitLabel(MCSymbol *S, SMLoc Loc) {
  87   auto *Symbol = cast<MCSymbolCOFF>(S);
  88   MCObjectStreamer::emitLabel(Symbol, Loc);
  89 }
  90
  91 void MCWinCOFFStreamer::emitAssemblerFlag(MCAssemblerFlag Flag) {
  92   // Let the target do whatever target specific stuff it needs to do.
  93   getAssembler().getBackend().handleAssemblerFlag(Flag);
  94
  95   switch (Flag) {
  96   // None of these require COFF specific handling.
  97   case MCAF_SyntaxUnified:
  98   case MCAF_Code16:
  99   case MCAF_Code32:
 100   case MCAF_Code64:
 101     break;
 102   case MCAF_SubsectionsViaSymbols:
 103     llvm_unreachable("COFF doesn't support .subsections_via_symbols");
 104   }
 105 }
 106
 107 void MCWinCOFFStreamer::emitThumbFunc(MCSymbol *Func) {
 108   llvm_unreachable("not implemented");
 109 }
 110
 111 bool MCWinCOFFStreamer::emitSymbolAttribute(MCSymbol *S,
 112                                             MCSymbolAttr Attribute) {
 113   auto *Symbol = cast<MCSymbolCOFF>(S);
 114   getAssembler().registerSymbol(*Symbol);
 115
 116   switch (Attribute) {
 117   default: return false;
 118   case MCSA_WeakReference:
 119   case MCSA_Weak:
 120     Symbol->setIsWeakExternal();
 121     Symbol->setExternal(true);
 122     break;
 123   case MCSA_Global:
 124     Symbol->setExternal(true);
 125     break;
 126   case MCSA_AltEntry:
 127     llvm_unreachable("COFF doesn't support the .alt_entry attribute");
 128   }
 129
 130   return true;
 131 }
 132
 133 void MCWinCOFFStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
 134   llvm_unreachable("not implemented");
 135 }
 136
 137 void MCWinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *S) {
 138   auto *Symbol = cast<MCSymbolCOFF>(S);
 139   if (CurSymbol)
 140     Error("starting a new symbol definition without completing the "
 141           "previous one");
 142   CurSymbol = Symbol;
 143 }
 144
 145 void MCWinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
 146   if (!CurSymbol) {
 147     Error("storage class specified outside of symbol definition");
 148     return;
 149   }
 150
 151   if (StorageClass & ~COFF::SSC_Invalid) {
 152     Error("storage class value '" + Twine(StorageClass) +
 153                "' out of range");
 154     return;
 155   }
 156
 157   getAssembler().registerSymbol(*CurSymbol);
 158   cast<MCSymbolCOFF>(CurSymbol)->setClass((uint16_t)StorageClass);
 159 }
 160
 161 void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) {
 162   if (!CurSymbol) {
 163     Error("symbol type specified outside of a symbol definition");
 164     return;
 165   }
 166
 167   if (Type & ~0xffff) {
 168     Error("type value '" + Twine(Type) + "' out of range");
 169     return;
 170   }
 171
 172   getAssembler().registerSymbol(*CurSymbol);
 173   cast<MCSymbolCOFF>(CurSymbol)->setType((uint16_t)Type);
 174 }
 175
 176 void MCWinCOFFStreamer::EndCOFFSymbolDef() {
 177   if (!CurSymbol)
 178     Error("ending symbol definition without starting one");
 179   CurSymbol = nullptr;
 180 }
 181
 182 void MCWinCOFFStreamer::EmitCOFFSafeSEH(MCSymbol const *Symbol) {
 183   // SafeSEH is a feature specific to 32-bit x86.  It does not exist (and is
 184   // unnecessary) on all platforms which use table-based exception dispatch.
 185   if (getContext().getTargetTriple().getArch() != Triple::x86)
 186     return;
 187
 188   const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Symbol);
 189   if (CSymbol->isSafeSEH())
 190     return;
 191
 192   MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection();
 193   getAssembler().registerSection(*SXData);
 194   if (SXData->getAlignment() < 4)
 195     SXData->setAlignment(Align(4));
 196
 197   new MCSymbolIdFragment(Symbol, SXData);
 198
 199   getAssembler().registerSymbol(*Symbol);
 200   CSymbol->setIsSafeSEH();
 201
 202   // The Microsoft linker requires that the symbol type of a handler be
 203   // function. Go ahead and oblige it here.
 204   CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
 205                    << COFF::SCT_COMPLEX_TYPE_SHIFT);
 206 }
 207
 208 void MCWinCOFFStreamer::EmitCOFFSymbolIndex(MCSymbol const *Symbol) {
 209   MCSection *Sec = getCurrentSectionOnly();
 210   getAssembler().registerSection(*Sec);
 211   if (Sec->getAlignment() < 4)
 212     Sec->setAlignment(Align(4));
 213
 214   new MCSymbolIdFragment(Symbol, getCurrentSectionOnly());
 215
 216   getAssembler().registerSymbol(*Symbol);
 217 }
 218
 219 void MCWinCOFFStreamer::EmitCOFFSectionIndex(const MCSymbol *Symbol) {
 220   visitUsedSymbol(*Symbol);
 221   MCDataFragment *DF = getOrCreateDataFragment();
 222   const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
 223   MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2);
 224   DF->getFixups().push_back(Fixup);
 225   DF->getContents().resize(DF->getContents().size() + 2, 0);
 226 }
 227
 228 void MCWinCOFFStreamer::EmitCOFFSecRel32(const MCSymbol *Symbol,
 229                                          uint64_t Offset) {
 230   visitUsedSymbol(*Symbol);
 231   MCDataFragment *DF = getOrCreateDataFragment();
 232   // Create Symbol A for the relocation relative reference.
 233   const MCExpr *MCE = MCSymbolRefExpr::create(Symbol, getContext());
 234   // Add the constant offset, if given.
 235   if (Offset)
 236     MCE = MCBinaryExpr::createAdd(
 237         MCE, MCConstantExpr::create(Offset, getContext()), getContext());
 238   // Build the secrel32 relocation.
 239   MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_SecRel_4);
 240   // Record the relocation.
 241   DF->getFixups().push_back(Fixup);
 242   // Emit 4 bytes (zeros) to the object file.
 243   DF->getContents().resize(DF->getContents().size() + 4, 0);
 244 }
 245
 246 void MCWinCOFFStreamer::EmitCOFFImgRel32(const MCSymbol *Symbol,
 247                                          int64_t Offset) {
 248   visitUsedSymbol(*Symbol);
 249   MCDataFragment *DF = getOrCreateDataFragment();
 250   // Create Symbol A for the relocation relative reference.
 251   const MCExpr *MCE = MCSymbolRefExpr::create(
 252       Symbol, MCSymbolRefExpr::VK_COFF_IMGREL32, getContext());
 253   // Add the constant offset, if given.
 254   if (Offset)
 255     MCE = MCBinaryExpr::createAdd(
 256         MCE, MCConstantExpr::create(Offset, getContext()), getContext());
 257   // Build the imgrel relocation.
 258   MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_Data_4);
 259   // Record the relocation.
 260   DF->getFixups().push_back(Fixup);
 261   // Emit 4 bytes (zeros) to the object file.
 262   DF->getContents().resize(DF->getContents().size() + 4, 0);
 263 }
 264
 265 void MCWinCOFFStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
 266                                          unsigned ByteAlignment) {
 267   auto *Symbol = cast<MCSymbolCOFF>(S);
 268
 269   const Triple &T = getContext().getTargetTriple();
 270   if (T.isWindowsMSVCEnvironment()) {
 271     if (ByteAlignment > 32)
 272       report_fatal_error("alignment is limited to 32-bytes");
 273
 274     // Round size up to alignment so that we will honor the alignment request.
 275     Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
 276   }
 277
 278   getAssembler().registerSymbol(*Symbol);
 279   Symbol->setExternal(true);
 280   Symbol->setCommon(Size, ByteAlignment);
 281
 282   if (!T.isWindowsMSVCEnvironment() && ByteAlignment > 1) {
 283     SmallString<128> Directive;
 284     raw_svector_ostream OS(Directive);
 285     const MCObjectFileInfo *MFI = getContext().getObjectFileInfo();
 286
 287     OS << " -aligncomm:\"" << Symbol->getName() << "\","
 288        << Log2_32_Ceil(ByteAlignment);
 289
 290     PushSection();
 291     SwitchSection(MFI->getDrectveSection());
 292     emitBytes(Directive);
 293     PopSection();
 294   }
 295 }
 296
 297 void MCWinCOFFStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
 298                                               unsigned ByteAlignment) {
 299   auto *Symbol = cast<MCSymbolCOFF>(S);
 300
 301   MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
 302   PushSection();
 303   SwitchSection(Section);
 304   emitValueToAlignment(ByteAlignment, 0, 1, 0);
 305   emitLabel(Symbol);
 306   Symbol->setExternal(false);
 307   emitZeros(Size);
 308   PopSection();
 309 }
 310
 311 void MCWinCOFFStreamer::emitWeakReference(MCSymbol *AliasS,
 312                                           const MCSymbol *Symbol) {
 313   auto *Alias = cast<MCSymbolCOFF>(AliasS);
 314   emitSymbolAttribute(Alias, MCSA_Weak);
 315
 316   getAssembler().registerSymbol(*Symbol);
 317   Alias->setVariableValue(MCSymbolRefExpr::create(
 318       Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext()));
 319 }
 320
 321 void MCWinCOFFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
 322                                      uint64_t Size, unsigned ByteAlignment,
 323                                      SMLoc Loc) {
 324   llvm_unreachable("not implemented");
 325 }
 326
 327 void MCWinCOFFStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
 328                                        uint64_t Size, unsigned ByteAlignment) {
 329   llvm_unreachable("not implemented");
 330 }
 331
 332 // TODO: Implement this if you want to emit .comment section in COFF obj files.
 333 void MCWinCOFFStreamer::emitIdent(StringRef IdentString) {
 334   llvm_unreachable("not implemented");
 335 }
 336
 337 void MCWinCOFFStreamer::EmitWinEHHandlerData(SMLoc Loc) {
 338   llvm_unreachable("not implemented");
 339 }
 340
 341 void MCWinCOFFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
 342                                            const MCSymbolRefExpr *To,
 343                                            uint64_t Count) {
 344   // Ignore temporary symbols for now.
 345   if (!From->getSymbol().isTemporary() && !To->getSymbol().isTemporary())
 346     getAssembler().CGProfile.push_back({From, To, Count});
 347 }
 348
 349 void MCWinCOFFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
 350   const MCSymbol *S = &SRE->getSymbol();
 351   bool Created;
 352   getAssembler().registerSymbol(*S, &Created);
 353   if (Created)
 354     cast<MCSymbolCOFF>(S)->setExternal(true);
 355 }
 356
 357 void MCWinCOFFStreamer::finalizeCGProfile() {
 358   for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
 359     finalizeCGProfileEntry(E.From);
 360     finalizeCGProfileEntry(E.To);
 361   }
 362 }
 363
 364 void MCWinCOFFStreamer::finishImpl() {
 365   finalizeCGProfile();
 366
 367   MCObjectStreamer::finishImpl();
 368 }
 369
 370 void MCWinCOFFStreamer::Error(const Twine &Msg) const {
 371   getContext().reportError(SMLoc(), Msg);
 372 }