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   llvm_unreachable("not implemented");
  92 }
  93
  94 void MCWinCOFFStreamer::EmitThumbFunc(MCSymbol *Func) {
  95   llvm_unreachable("not implemented");
  96 }
  97
  98 bool MCWinCOFFStreamer::EmitSymbolAttribute(MCSymbol *S,
  99                                             MCSymbolAttr Attribute) {
 100   auto *Symbol = cast<MCSymbolCOFF>(S);
 101   getAssembler().registerSymbol(*Symbol);
 102
 103   switch (Attribute) {
 104   default: return false;
 105   case MCSA_WeakReference:
 106   case MCSA_Weak:
 107     Symbol->setIsWeakExternal();
 108     Symbol->setExternal(true);
 109     break;
 110   case MCSA_Global:
 111     Symbol->setExternal(true);
 112     break;
 113   case MCSA_AltEntry:
 114     llvm_unreachable("COFF doesn't support the .alt_entry attribute");
 115   }
 116
 117   return true;
 118 }
 119
 120 void MCWinCOFFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
 121   llvm_unreachable("not implemented");
 122 }
 123
 124 void MCWinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *S) {
 125   auto *Symbol = cast<MCSymbolCOFF>(S);
 126   if (CurSymbol)
 127     Error("starting a new symbol definition without completing the "
 128           "previous one");
 129   CurSymbol = Symbol;
 130 }
 131
 132 void MCWinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
 133   if (!CurSymbol) {
 134     Error("storage class specified outside of symbol definition");
 135     return;
 136   }
 137
 138   if (StorageClass & ~COFF::SSC_Invalid) {
 139     Error("storage class value '" + Twine(StorageClass) +
 140                "' out of range");
 141     return;
 142   }
 143
 144   getAssembler().registerSymbol(*CurSymbol);
 145   cast<MCSymbolCOFF>(CurSymbol)->setClass((uint16_t)StorageClass);
 146 }
 147
 148 void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) {
 149   if (!CurSymbol) {
 150     Error("symbol type specified outside of a symbol definition");
 151     return;
 152   }
 153
 154   if (Type & ~0xffff) {
 155     Error("type value '" + Twine(Type) + "' out of range");
 156     return;
 157   }
 158
 159   getAssembler().registerSymbol(*CurSymbol);
 160   cast<MCSymbolCOFF>(CurSymbol)->setType((uint16_t)Type);
 161 }
 162
 163 void MCWinCOFFStreamer::EndCOFFSymbolDef() {
 164   if (!CurSymbol)
 165     Error("ending symbol definition without starting one");
 166   CurSymbol = nullptr;
 167 }
 168
 169 void MCWinCOFFStreamer::EmitCOFFSafeSEH(MCSymbol const *Symbol) {
 170   // SafeSEH is a feature specific to 32-bit x86.  It does not exist (and is
 171   // unnecessary) on all platforms which use table-based exception dispatch.
 172   if (getContext().getObjectFileInfo()->getTargetTriple().getArch() !=
 173       Triple::x86)
 174     return;
 175
 176   const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Symbol);
 177   if (CSymbol->isSafeSEH())
 178     return;
 179
 180   MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection();
 181   getAssembler().registerSection(*SXData);
 182   if (SXData->getAlignment() < 4)
 183     SXData->setAlignment(4);
 184
 185   new MCSymbolIdFragment(Symbol, SXData);
 186
 187   getAssembler().registerSymbol(*Symbol);
 188   CSymbol->setIsSafeSEH();
 189
 190   // The Microsoft linker requires that the symbol type of a handler be
 191   // function. Go ahead and oblige it here.
 192   CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
 193                    << COFF::SCT_COMPLEX_TYPE_SHIFT);
 194 }
 195
 196 void MCWinCOFFStreamer::EmitCOFFSymbolIndex(MCSymbol const *Symbol) {
 197   MCSection *Sec = getCurrentSectionOnly();
 198   getAssembler().registerSection(*Sec);
 199   if (Sec->getAlignment() < 4)
 200     Sec->setAlignment(4);
 201
 202   new MCSymbolIdFragment(Symbol, getCurrentSectionOnly());
 203
 204   getAssembler().registerSymbol(*Symbol);
 205 }
 206
 207 void MCWinCOFFStreamer::EmitCOFFSectionIndex(const MCSymbol *Symbol) {
 208   visitUsedSymbol(*Symbol);
 209   MCDataFragment *DF = getOrCreateDataFragment();
 210   const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
 211   MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2);
 212   DF->getFixups().push_back(Fixup);
 213   DF->getContents().resize(DF->getContents().size() + 2, 0);
 214 }
 215
 216 void MCWinCOFFStreamer::EmitCOFFSecRel32(const MCSymbol *Symbol,
 217                                          uint64_t Offset) {
 218   visitUsedSymbol(*Symbol);
 219   MCDataFragment *DF = getOrCreateDataFragment();
 220   // Create Symbol A for the relocation relative reference.
 221   const MCExpr *MCE = MCSymbolRefExpr::create(Symbol, getContext());
 222   // Add the constant offset, if given.
 223   if (Offset)
 224     MCE = MCBinaryExpr::createAdd(
 225         MCE, MCConstantExpr::create(Offset, getContext()), getContext());
 226   // Build the secrel32 relocation.
 227   MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_SecRel_4);
 228   // Record the relocation.
 229   DF->getFixups().push_back(Fixup);
 230   // Emit 4 bytes (zeros) to the object file.
 231   DF->getContents().resize(DF->getContents().size() + 4, 0);
 232 }
 233
 234 void MCWinCOFFStreamer::EmitCOFFImgRel32(const MCSymbol *Symbol,
 235                                          int64_t Offset) {
 236   visitUsedSymbol(*Symbol);
 237   MCDataFragment *DF = getOrCreateDataFragment();
 238   // Create Symbol A for the relocation relative reference.
 239   const MCExpr *MCE = MCSymbolRefExpr::create(
 240       Symbol, MCSymbolRefExpr::VK_COFF_IMGREL32, getContext());
 241   // Add the constant offset, if given.
 242   if (Offset)
 243     MCE = MCBinaryExpr::createAdd(
 244         MCE, MCConstantExpr::create(Offset, getContext()), getContext());
 245   // Build the imgrel relocation.
 246   MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_Data_4);
 247   // Record the relocation.
 248   DF->getFixups().push_back(Fixup);
 249   // Emit 4 bytes (zeros) to the object file.
 250   DF->getContents().resize(DF->getContents().size() + 4, 0);
 251 }
 252
 253 void MCWinCOFFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
 254                                          unsigned ByteAlignment) {
 255   auto *Symbol = cast<MCSymbolCOFF>(S);
 256
 257   const Triple &T = getContext().getObjectFileInfo()->getTargetTriple();
 258   if (T.isWindowsMSVCEnvironment()) {
 259     if (ByteAlignment > 32)
 260       report_fatal_error("alignment is limited to 32-bytes");
 261
 262     // Round size up to alignment so that we will honor the alignment request.
 263     Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
 264   }
 265
 266   getAssembler().registerSymbol(*Symbol);
 267   Symbol->setExternal(true);
 268   Symbol->setCommon(Size, ByteAlignment);
 269
 270   if (!T.isWindowsMSVCEnvironment() && ByteAlignment > 1) {
 271     SmallString<128> Directive;
 272     raw_svector_ostream OS(Directive);
 273     const MCObjectFileInfo *MFI = getContext().getObjectFileInfo();
 274
 275     OS << " -aligncomm:\"" << Symbol->getName() << "\","
 276        << Log2_32_Ceil(ByteAlignment);
 277
 278     PushSection();
 279     SwitchSection(MFI->getDrectveSection());
 280     EmitBytes(Directive);
 281     PopSection();
 282   }
 283 }
 284
 285 void MCWinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
 286                                               unsigned ByteAlignment) {
 287   auto *Symbol = cast<MCSymbolCOFF>(S);
 288
 289   MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
 290   PushSection();
 291   SwitchSection(Section);
 292   EmitValueToAlignment(ByteAlignment, 0, 1, 0);
 293   EmitLabel(Symbol);
 294   Symbol->setExternal(false);
 295   EmitZeros(Size);
 296   PopSection();
 297 }
 298
 299 void MCWinCOFFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
 300                                      uint64_t Size, unsigned ByteAlignment,
 301                                      SMLoc Loc) {
 302   llvm_unreachable("not implemented");
 303 }
 304
 305 void MCWinCOFFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
 306                                        uint64_t Size, unsigned ByteAlignment) {
 307   llvm_unreachable("not implemented");
 308 }
 309
 310 // TODO: Implement this if you want to emit .comment section in COFF obj files.
 311 void MCWinCOFFStreamer::EmitIdent(StringRef IdentString) {
 312   llvm_unreachable("not implemented");
 313 }
 314
 315 void MCWinCOFFStreamer::EmitWinEHHandlerData(SMLoc Loc) {
 316   llvm_unreachable("not implemented");
 317 }
 318
 319 void MCWinCOFFStreamer::FinishImpl() {
 320   MCObjectStreamer::FinishImpl();
 321 }
 322
 323 void MCWinCOFFStreamer::Error(const Twine &Msg) const {
 324   getContext().reportError(SMLoc(), Msg);
 325 }