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
MCWinCOFFStreamer(MCContext & Context,std::unique_ptr<MCAsmBackend> MAB,std::unique_ptr<MCCodeEmitter> CE,std::unique_ptr<MCObjectWriter> OW)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
getWriter()56 WinCOFFObjectWriter &MCWinCOFFStreamer::getWriter() {
57 return static_cast<WinCOFFObjectWriter &>(getAssembler().getWriter());
58 }
59
emitInstToData(const MCInst & Inst,const MCSubtargetInfo & STI)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
initSections(bool NoExecStack,const MCSubtargetInfo & STI)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
changeSection(MCSection * Section,uint32_t Subsection)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
emitLabel(MCSymbol * S,SMLoc Loc)103 void MCWinCOFFStreamer::emitLabel(MCSymbol *S, SMLoc Loc) {
104 auto *Symbol = cast<MCSymbolCOFF>(S);
105 MCObjectStreamer::emitLabel(Symbol, Loc);
106 }
107
emitAssemblerFlag(MCAssemblerFlag Flag)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
emitThumbFunc(MCSymbol * Func)124 void MCWinCOFFStreamer::emitThumbFunc(MCSymbol *Func) {
125 llvm_unreachable("not implemented");
126 }
127
emitSymbolAttribute(MCSymbol * S,MCSymbolAttr Attribute)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
emitSymbolDesc(MCSymbol * Symbol,unsigned DescValue)155 void MCWinCOFFStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
156 llvm_unreachable("not implemented");
157 }
158
beginCOFFSymbolDef(MCSymbol const * S)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
emitCOFFSymbolStorageClass(int StorageClass)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
emitCOFFSymbolType(int Type)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
endCOFFSymbolDef()198 void MCWinCOFFStreamer::endCOFFSymbolDef() {
199 if (!CurSymbol)
200 Error("ending symbol definition without starting one");
201 CurSymbol = nullptr;
202 }
203
emitCOFFSafeSEH(MCSymbol const * Symbol)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
emitCOFFSymbolIndex(MCSymbol const * Symbol)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
emitCOFFSectionIndex(const MCSymbol * Symbol)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
emitCOFFSecRel32(const MCSymbol * Symbol,uint64_t Offset)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
emitCOFFImgRel32(const MCSymbol * Symbol,int64_t Offset)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
emitCommonSymbol(MCSymbol * S,uint64_t Size,Align ByteAlignment)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
emitLocalCommonSymbol(MCSymbol * S,uint64_t Size,Align ByteAlignment)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
emitWeakReference(MCSymbol * AliasS,const MCSymbol * Symbol)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
emitZerofill(MCSection * Section,MCSymbol * Symbol,uint64_t Size,Align ByteAlignment,SMLoc Loc)338 void MCWinCOFFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
339 uint64_t Size, Align ByteAlignment,
340 SMLoc Loc) {
341 llvm_unreachable("not implemented");
342 }
343
emitTBSSSymbol(MCSection * Section,MCSymbol * Symbol,uint64_t Size,Align ByteAlignment)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.
emitIdent(StringRef IdentString)350 void MCWinCOFFStreamer::emitIdent(StringRef IdentString) {
351 llvm_unreachable("not implemented");
352 }
353
emitWinEHHandlerData(SMLoc Loc)354 void MCWinCOFFStreamer::emitWinEHHandlerData(SMLoc Loc) {
355 llvm_unreachable("not implemented");
356 }
357
emitCGProfileEntry(const MCSymbolRefExpr * From,const MCSymbolRefExpr * To,uint64_t Count)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
finalizeCGProfileEntry(const MCSymbolRefExpr * & SRE)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
finishImpl()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
Error(const Twine & Msg) const391 void MCWinCOFFStreamer::Error(const Twine &Msg) const {
392 getContext().reportError(SMLoc(), Msg);
393 }
394