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   // FIXME: this is identical to the ELF one.
  71   // This emulates the same behavior of GNU as. This makes it easier
  72   // to compare the output as the major sections are in the same order.
  73   SwitchSection(getContext().getObjectFileInfo()->getTextSection());
  74   EmitCodeAlignment(4);
  75
  76   SwitchSection(getContext().getObjectFileInfo()->getDataSection());
  77   EmitCodeAlignment(4);
  78
  79   SwitchSection(getContext().getObjectFileInfo()->getBSSSection());
  80   EmitCodeAlignment(4);
  81
  82   SwitchSection(getContext().getObjectFileInfo()->getTextSection());
  83 }
  84
  85 void MCWinCOFFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc) {
  86   auto *Symbol = cast<MCSymbolCOFF>(S);
  87   MCObjectStreamer::EmitLabel(Symbol, Loc);
  88 }
  89
  90 void MCWinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
  91   // Let the target do whatever target specific stuff it needs to do.
  92   getAssembler().getBackend().handleAssemblerFlag(Flag);
  93
  94   switch (Flag) {
  95   // None of these require COFF specific handling.
  96   case MCAF_SyntaxUnified:
  97   case MCAF_Code16:
  98   case MCAF_Code32:
  99   case MCAF_Code64:
 100     break;
 101   case MCAF_SubsectionsViaSymbols:
 102     llvm_unreachable("COFF doesn't support .subsections_via_symbols");
 103   }
 104 }
 105
 106 void MCWinCOFFStreamer::EmitThumbFunc(MCSymbol *Func) {
 107   llvm_unreachable("not implemented");
 108 }
 109
 110 bool MCWinCOFFStreamer::EmitSymbolAttribute(MCSymbol *S,
 111                                             MCSymbolAttr Attribute) {
 112   auto *Symbol = cast<MCSymbolCOFF>(S);
 113   getAssembler().registerSymbol(*Symbol);
 114
 115   switch (Attribute) {
 116   default: return false;
 117   case MCSA_WeakReference:
 118   case MCSA_Weak:
 119     Symbol->setIsWeakExternal();
 120     Symbol->setExternal(true);
 121     break;
 122   case MCSA_Global:
 123     Symbol->setExternal(true);
 124     break;
 125   case MCSA_AltEntry:
 126     llvm_unreachable("COFF doesn't support the .alt_entry attribute");
 127   }
 128
 129   return true;
 130 }
 131
 132 void MCWinCOFFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
 133   llvm_unreachable("not implemented");
 134 }
 135
 136 void MCWinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *S) {
 137   auto *Symbol = cast<MCSymbolCOFF>(S);
 138   if (CurSymbol)
 139     Error("starting a new symbol definition without completing the "
 140           "previous one");
 141   CurSymbol = Symbol;
 142 }
 143
 144 void MCWinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
 145   if (!CurSymbol) {
 146     Error("storage class specified outside of symbol definition");
 147     return;
 148   }
 149
 150   if (StorageClass & ~COFF::SSC_Invalid) {
 151     Error("storage class value '" + Twine(StorageClass) +
 152                "' out of range");
 153     return;
 154   }
 155
 156   getAssembler().registerSymbol(*CurSymbol);
 157   cast<MCSymbolCOFF>(CurSymbol)->setClass((uint16_t)StorageClass);
 158 }
 159
 160 void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) {
 161   if (!CurSymbol) {
 162     Error("symbol type specified outside of a symbol definition");
 163     return;
 164   }
 165
 166   if (Type & ~0xffff) {
 167     Error("type value '" + Twine(Type) + "' out of range");
 168     return;
 169   }
 170
 171   getAssembler().registerSymbol(*CurSymbol);
 172   cast<MCSymbolCOFF>(CurSymbol)->setType((uint16_t)Type);
 173 }
 174
 175 void MCWinCOFFStreamer::EndCOFFSymbolDef() {
 176   if (!CurSymbol)
 177     Error("ending symbol definition without starting one");
 178   CurSymbol = nullptr;
 179 }
 180
 181 void MCWinCOFFStreamer::EmitCOFFSafeSEH(MCSymbol const *Symbol) {
 182   // SafeSEH is a feature specific to 32-bit x86.  It does not exist (and is
 183   // unnecessary) on all platforms which use table-based exception dispatch.
 184   if (getContext().getObjectFileInfo()->getTargetTriple().getArch() !=
 185       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().getObjectFileInfo()->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::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
 312                                      uint64_t Size, unsigned ByteAlignment,
 313                                      SMLoc Loc) {
 314   llvm_unreachable("not implemented");
 315 }
 316
 317 void MCWinCOFFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
 318                                        uint64_t Size, unsigned ByteAlignment) {
 319   llvm_unreachable("not implemented");
 320 }
 321
 322 // TODO: Implement this if you want to emit .comment section in COFF obj files.
 323 void MCWinCOFFStreamer::EmitIdent(StringRef IdentString) {
 324   llvm_unreachable("not implemented");
 325 }
 326
 327 void MCWinCOFFStreamer::EmitWinEHHandlerData(SMLoc Loc) {
 328   llvm_unreachable("not implemented");
 329 }
 330
 331 void MCWinCOFFStreamer::FinishImpl() {
 332   MCObjectStreamer::FinishImpl();
 333 }
 334
 335 void MCWinCOFFStreamer::Error(const Twine &Msg) const {
 336   getContext().reportError(SMLoc(), Msg);
 337 }