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/Triple.h"
17 #include "llvm/ADT/Twine.h"
18 #include "llvm/BinaryFormat/COFF.h"
19 #include "llvm/MC/MCAsmBackend.h"
20 #include "llvm/MC/MCAssembler.h"
21 #include "llvm/MC/MCCodeEmitter.h"
22 #include "llvm/MC/MCContext.h"
23 #include "llvm/MC/MCExpr.h"
24 #include "llvm/MC/MCFixup.h"
25 #include "llvm/MC/MCFragment.h"
26 #include "llvm/MC/MCObjectFileInfo.h"
27 #include "llvm/MC/MCObjectStreamer.h"
28 #include "llvm/MC/MCObjectWriter.h"
29 #include "llvm/MC/MCSection.h"
30 #include "llvm/MC/MCSymbolCOFF.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 <cstdint>
38
39 using namespace llvm;
40
41 #define DEBUG_TYPE "WinCOFFStreamer"
42
MCWinCOFFStreamer(MCContext & Context,std::unique_ptr<MCAsmBackend> MAB,std::unique_ptr<MCCodeEmitter> CE,std::unique_ptr<MCObjectWriter> OW)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
emitInstToData(const MCInst & Inst,const MCSubtargetInfo & STI)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 raw_svector_ostream VecOS(Code);
57 getAssembler().getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
58
59 // Add the fixups and data.
60 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
61 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
62 DF->getFixups().push_back(Fixups[i]);
63 }
64 DF->setHasInstructions(STI);
65 DF->getContents().append(Code.begin(), Code.end());
66 }
67
initSections(bool NoExecStack,const MCSubtargetInfo & STI)68 void MCWinCOFFStreamer::initSections(bool NoExecStack,
69 const MCSubtargetInfo &STI) {
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(Align(4), &STI);
75
76 switchSection(getContext().getObjectFileInfo()->getDataSection());
77 emitCodeAlignment(Align(4), &STI);
78
79 switchSection(getContext().getObjectFileInfo()->getBSSSection());
80 emitCodeAlignment(Align(4), &STI);
81
82 switchSection(getContext().getObjectFileInfo()->getTextSection());
83 }
84
emitLabel(MCSymbol * S,SMLoc Loc)85 void MCWinCOFFStreamer::emitLabel(MCSymbol *S, SMLoc Loc) {
86 auto *Symbol = cast<MCSymbolCOFF>(S);
87 MCObjectStreamer::emitLabel(Symbol, Loc);
88 }
89
emitAssemblerFlag(MCAssemblerFlag Flag)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
emitThumbFunc(MCSymbol * Func)106 void MCWinCOFFStreamer::emitThumbFunc(MCSymbol *Func) {
107 llvm_unreachable("not implemented");
108 }
109
emitSymbolAttribute(MCSymbol * S,MCSymbolAttr Attribute)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
emitSymbolDesc(MCSymbol * Symbol,unsigned DescValue)132 void MCWinCOFFStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
133 llvm_unreachable("not implemented");
134 }
135
beginCOFFSymbolDef(MCSymbol const * S)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
emitCOFFSymbolStorageClass(int StorageClass)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
emitCOFFSymbolType(int Type)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
endCOFFSymbolDef()175 void MCWinCOFFStreamer::endCOFFSymbolDef() {
176 if (!CurSymbol)
177 Error("ending symbol definition without starting one");
178 CurSymbol = nullptr;
179 }
180
emitCOFFSafeSEH(MCSymbol const * Symbol)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().getTargetTriple().getArch() != Triple::x86)
185 return;
186
187 const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Symbol);
188 if (CSymbol->isSafeSEH())
189 return;
190
191 MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection();
192 getAssembler().registerSection(*SXData);
193 SXData->ensureMinAlignment(Align(4));
194
195 new MCSymbolIdFragment(Symbol, SXData);
196
197 getAssembler().registerSymbol(*Symbol);
198 CSymbol->setIsSafeSEH();
199
200 // The Microsoft linker requires that the symbol type of a handler be
201 // function. Go ahead and oblige it here.
202 CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
203 << COFF::SCT_COMPLEX_TYPE_SHIFT);
204 }
205
emitCOFFSymbolIndex(MCSymbol const * Symbol)206 void MCWinCOFFStreamer::emitCOFFSymbolIndex(MCSymbol const *Symbol) {
207 MCSection *Sec = getCurrentSectionOnly();
208 getAssembler().registerSection(*Sec);
209 Sec->ensureMinAlignment(Align(4));
210
211 new MCSymbolIdFragment(Symbol, getCurrentSectionOnly());
212
213 getAssembler().registerSymbol(*Symbol);
214 }
215
emitCOFFSectionIndex(const MCSymbol * Symbol)216 void MCWinCOFFStreamer::emitCOFFSectionIndex(const MCSymbol *Symbol) {
217 visitUsedSymbol(*Symbol);
218 MCDataFragment *DF = getOrCreateDataFragment();
219 const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
220 MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2);
221 DF->getFixups().push_back(Fixup);
222 DF->getContents().resize(DF->getContents().size() + 2, 0);
223 }
224
emitCOFFSecRel32(const MCSymbol * Symbol,uint64_t Offset)225 void MCWinCOFFStreamer::emitCOFFSecRel32(const MCSymbol *Symbol,
226 uint64_t Offset) {
227 visitUsedSymbol(*Symbol);
228 MCDataFragment *DF = getOrCreateDataFragment();
229 // Create Symbol A for the relocation relative reference.
230 const MCExpr *MCE = MCSymbolRefExpr::create(Symbol, getContext());
231 // Add the constant offset, if given.
232 if (Offset)
233 MCE = MCBinaryExpr::createAdd(
234 MCE, MCConstantExpr::create(Offset, getContext()), getContext());
235 // Build the secrel32 relocation.
236 MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_SecRel_4);
237 // Record the relocation.
238 DF->getFixups().push_back(Fixup);
239 // Emit 4 bytes (zeros) to the object file.
240 DF->getContents().resize(DF->getContents().size() + 4, 0);
241 }
242
emitCOFFImgRel32(const MCSymbol * Symbol,int64_t Offset)243 void MCWinCOFFStreamer::emitCOFFImgRel32(const MCSymbol *Symbol,
244 int64_t Offset) {
245 visitUsedSymbol(*Symbol);
246 MCDataFragment *DF = getOrCreateDataFragment();
247 // Create Symbol A for the relocation relative reference.
248 const MCExpr *MCE = MCSymbolRefExpr::create(
249 Symbol, MCSymbolRefExpr::VK_COFF_IMGREL32, getContext());
250 // Add the constant offset, if given.
251 if (Offset)
252 MCE = MCBinaryExpr::createAdd(
253 MCE, MCConstantExpr::create(Offset, getContext()), getContext());
254 // Build the imgrel relocation.
255 MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_Data_4);
256 // Record the relocation.
257 DF->getFixups().push_back(Fixup);
258 // Emit 4 bytes (zeros) to the object file.
259 DF->getContents().resize(DF->getContents().size() + 4, 0);
260 }
261
emitCommonSymbol(MCSymbol * S,uint64_t Size,Align ByteAlignment)262 void MCWinCOFFStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
263 Align ByteAlignment) {
264 auto *Symbol = cast<MCSymbolCOFF>(S);
265
266 const Triple &T = getContext().getTargetTriple();
267 if (T.isWindowsMSVCEnvironment()) {
268 if (ByteAlignment > 32)
269 report_fatal_error("alignment is limited to 32-bytes");
270
271 // Round size up to alignment so that we will honor the alignment request.
272 Size = std::max(Size, ByteAlignment.value());
273 }
274
275 getAssembler().registerSymbol(*Symbol);
276 Symbol->setExternal(true);
277 Symbol->setCommon(Size, ByteAlignment);
278
279 if (!T.isWindowsMSVCEnvironment() && ByteAlignment > 1) {
280 SmallString<128> Directive;
281 raw_svector_ostream OS(Directive);
282 const MCObjectFileInfo *MFI = getContext().getObjectFileInfo();
283
284 OS << " -aligncomm:\"" << Symbol->getName() << "\","
285 << Log2_32_Ceil(ByteAlignment.value());
286
287 pushSection();
288 switchSection(MFI->getDrectveSection());
289 emitBytes(Directive);
290 popSection();
291 }
292 }
293
emitLocalCommonSymbol(MCSymbol * S,uint64_t Size,Align ByteAlignment)294 void MCWinCOFFStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
295 Align ByteAlignment) {
296 auto *Symbol = cast<MCSymbolCOFF>(S);
297
298 MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
299 pushSection();
300 switchSection(Section);
301 emitValueToAlignment(ByteAlignment, 0, 1, 0);
302 emitLabel(Symbol);
303 Symbol->setExternal(false);
304 emitZeros(Size);
305 popSection();
306 }
307
emitWeakReference(MCSymbol * AliasS,const MCSymbol * Symbol)308 void MCWinCOFFStreamer::emitWeakReference(MCSymbol *AliasS,
309 const MCSymbol *Symbol) {
310 auto *Alias = cast<MCSymbolCOFF>(AliasS);
311 emitSymbolAttribute(Alias, MCSA_Weak);
312
313 getAssembler().registerSymbol(*Symbol);
314 Alias->setVariableValue(MCSymbolRefExpr::create(
315 Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext()));
316 }
317
emitZerofill(MCSection * Section,MCSymbol * Symbol,uint64_t Size,Align ByteAlignment,SMLoc Loc)318 void MCWinCOFFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
319 uint64_t Size, Align ByteAlignment,
320 SMLoc Loc) {
321 llvm_unreachable("not implemented");
322 }
323
emitTBSSSymbol(MCSection * Section,MCSymbol * Symbol,uint64_t Size,Align ByteAlignment)324 void MCWinCOFFStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
325 uint64_t Size, Align ByteAlignment) {
326 llvm_unreachable("not implemented");
327 }
328
329 // TODO: Implement this if you want to emit .comment section in COFF obj files.
emitIdent(StringRef IdentString)330 void MCWinCOFFStreamer::emitIdent(StringRef IdentString) {
331 llvm_unreachable("not implemented");
332 }
333
emitWinEHHandlerData(SMLoc Loc)334 void MCWinCOFFStreamer::emitWinEHHandlerData(SMLoc Loc) {
335 llvm_unreachable("not implemented");
336 }
337
emitCGProfileEntry(const MCSymbolRefExpr * From,const MCSymbolRefExpr * To,uint64_t Count)338 void MCWinCOFFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
339 const MCSymbolRefExpr *To,
340 uint64_t Count) {
341 // Ignore temporary symbols for now.
342 if (!From->getSymbol().isTemporary() && !To->getSymbol().isTemporary())
343 getAssembler().CGProfile.push_back({From, To, Count});
344 }
345
finalizeCGProfileEntry(const MCSymbolRefExpr * & SRE)346 void MCWinCOFFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
347 const MCSymbol *S = &SRE->getSymbol();
348 bool Created;
349 getAssembler().registerSymbol(*S, &Created);
350 if (Created)
351 cast<MCSymbolCOFF>(S)->setExternal(true);
352 }
353
finalizeCGProfile()354 void MCWinCOFFStreamer::finalizeCGProfile() {
355 for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
356 finalizeCGProfileEntry(E.From);
357 finalizeCGProfileEntry(E.To);
358 }
359 }
360
finishImpl()361 void MCWinCOFFStreamer::finishImpl() {
362 finalizeCGProfile();
363
364 MCObjectStreamer::finishImpl();
365 }
366
Error(const Twine & Msg) const367 void MCWinCOFFStreamer::Error(const Twine &Msg) const {
368 getContext().reportError(SMLoc(), Msg);
369 }
370