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
MCWinCOFFStreamer(MCContext & Context,std::unique_ptr<MCAsmBackend> MAB,std::unique_ptr<MCCodeEmitter> CE,std::unique_ptr<MCObjectWriter> OW)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
emitInstToData(const MCInst & Inst,const MCSubtargetInfo & STI)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
InitSections(bool NoExecStack)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
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 if (SXData->getAlignment() < 4)
194 SXData->setAlignment(Align(4));
195
196 new MCSymbolIdFragment(Symbol, SXData);
197
198 getAssembler().registerSymbol(*Symbol);
199 CSymbol->setIsSafeSEH();
200
201 // The Microsoft linker requires that the symbol type of a handler be
202 // function. Go ahead and oblige it here.
203 CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
204 << COFF::SCT_COMPLEX_TYPE_SHIFT);
205 }
206
EmitCOFFSymbolIndex(MCSymbol const * Symbol)207 void MCWinCOFFStreamer::EmitCOFFSymbolIndex(MCSymbol const *Symbol) {
208 MCSection *Sec = getCurrentSectionOnly();
209 getAssembler().registerSection(*Sec);
210 if (Sec->getAlignment() < 4)
211 Sec->setAlignment(Align(4));
212
213 new MCSymbolIdFragment(Symbol, getCurrentSectionOnly());
214
215 getAssembler().registerSymbol(*Symbol);
216 }
217
EmitCOFFSectionIndex(const MCSymbol * Symbol)218 void MCWinCOFFStreamer::EmitCOFFSectionIndex(const MCSymbol *Symbol) {
219 visitUsedSymbol(*Symbol);
220 MCDataFragment *DF = getOrCreateDataFragment();
221 const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
222 MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2);
223 DF->getFixups().push_back(Fixup);
224 DF->getContents().resize(DF->getContents().size() + 2, 0);
225 }
226
EmitCOFFSecRel32(const MCSymbol * Symbol,uint64_t Offset)227 void MCWinCOFFStreamer::EmitCOFFSecRel32(const MCSymbol *Symbol,
228 uint64_t Offset) {
229 visitUsedSymbol(*Symbol);
230 MCDataFragment *DF = getOrCreateDataFragment();
231 // Create Symbol A for the relocation relative reference.
232 const MCExpr *MCE = MCSymbolRefExpr::create(Symbol, getContext());
233 // Add the constant offset, if given.
234 if (Offset)
235 MCE = MCBinaryExpr::createAdd(
236 MCE, MCConstantExpr::create(Offset, getContext()), getContext());
237 // Build the secrel32 relocation.
238 MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_SecRel_4);
239 // Record the relocation.
240 DF->getFixups().push_back(Fixup);
241 // Emit 4 bytes (zeros) to the object file.
242 DF->getContents().resize(DF->getContents().size() + 4, 0);
243 }
244
EmitCOFFImgRel32(const MCSymbol * Symbol,int64_t Offset)245 void MCWinCOFFStreamer::EmitCOFFImgRel32(const MCSymbol *Symbol,
246 int64_t Offset) {
247 visitUsedSymbol(*Symbol);
248 MCDataFragment *DF = getOrCreateDataFragment();
249 // Create Symbol A for the relocation relative reference.
250 const MCExpr *MCE = MCSymbolRefExpr::create(
251 Symbol, MCSymbolRefExpr::VK_COFF_IMGREL32, getContext());
252 // Add the constant offset, if given.
253 if (Offset)
254 MCE = MCBinaryExpr::createAdd(
255 MCE, MCConstantExpr::create(Offset, getContext()), getContext());
256 // Build the imgrel relocation.
257 MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_Data_4);
258 // Record the relocation.
259 DF->getFixups().push_back(Fixup);
260 // Emit 4 bytes (zeros) to the object file.
261 DF->getContents().resize(DF->getContents().size() + 4, 0);
262 }
263
emitCommonSymbol(MCSymbol * S,uint64_t Size,unsigned ByteAlignment)264 void MCWinCOFFStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
265 unsigned ByteAlignment) {
266 auto *Symbol = cast<MCSymbolCOFF>(S);
267
268 const Triple &T = getContext().getTargetTriple();
269 if (T.isWindowsMSVCEnvironment()) {
270 if (ByteAlignment > 32)
271 report_fatal_error("alignment is limited to 32-bytes");
272
273 // Round size up to alignment so that we will honor the alignment request.
274 Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
275 }
276
277 getAssembler().registerSymbol(*Symbol);
278 Symbol->setExternal(true);
279 Symbol->setCommon(Size, ByteAlignment);
280
281 if (!T.isWindowsMSVCEnvironment() && ByteAlignment > 1) {
282 SmallString<128> Directive;
283 raw_svector_ostream OS(Directive);
284 const MCObjectFileInfo *MFI = getContext().getObjectFileInfo();
285
286 OS << " -aligncomm:\"" << Symbol->getName() << "\","
287 << Log2_32_Ceil(ByteAlignment);
288
289 PushSection();
290 SwitchSection(MFI->getDrectveSection());
291 emitBytes(Directive);
292 PopSection();
293 }
294 }
295
emitLocalCommonSymbol(MCSymbol * S,uint64_t Size,unsigned ByteAlignment)296 void MCWinCOFFStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
297 unsigned ByteAlignment) {
298 auto *Symbol = cast<MCSymbolCOFF>(S);
299
300 MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
301 PushSection();
302 SwitchSection(Section);
303 emitValueToAlignment(ByteAlignment, 0, 1, 0);
304 emitLabel(Symbol);
305 Symbol->setExternal(false);
306 emitZeros(Size);
307 PopSection();
308 }
309
emitWeakReference(MCSymbol * AliasS,const MCSymbol * Symbol)310 void MCWinCOFFStreamer::emitWeakReference(MCSymbol *AliasS,
311 const MCSymbol *Symbol) {
312 auto *Alias = cast<MCSymbolCOFF>(AliasS);
313 emitSymbolAttribute(Alias, MCSA_Weak);
314
315 getAssembler().registerSymbol(*Symbol);
316 Alias->setVariableValue(MCSymbolRefExpr::create(
317 Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext()));
318 }
319
emitZerofill(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment,SMLoc Loc)320 void MCWinCOFFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
321 uint64_t Size, unsigned ByteAlignment,
322 SMLoc Loc) {
323 llvm_unreachable("not implemented");
324 }
325
emitTBSSSymbol(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)326 void MCWinCOFFStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
327 uint64_t Size, unsigned ByteAlignment) {
328 llvm_unreachable("not implemented");
329 }
330
331 // TODO: Implement this if you want to emit .comment section in COFF obj files.
emitIdent(StringRef IdentString)332 void MCWinCOFFStreamer::emitIdent(StringRef IdentString) {
333 llvm_unreachable("not implemented");
334 }
335
EmitWinEHHandlerData(SMLoc Loc)336 void MCWinCOFFStreamer::EmitWinEHHandlerData(SMLoc Loc) {
337 llvm_unreachable("not implemented");
338 }
339
emitCGProfileEntry(const MCSymbolRefExpr * From,const MCSymbolRefExpr * To,uint64_t Count)340 void MCWinCOFFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
341 const MCSymbolRefExpr *To,
342 uint64_t Count) {
343 // Ignore temporary symbols for now.
344 if (!From->getSymbol().isTemporary() && !To->getSymbol().isTemporary())
345 getAssembler().CGProfile.push_back({From, To, Count});
346 }
347
finalizeCGProfileEntry(const MCSymbolRefExpr * & SRE)348 void MCWinCOFFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
349 const MCSymbol *S = &SRE->getSymbol();
350 bool Created;
351 getAssembler().registerSymbol(*S, &Created);
352 if (Created)
353 cast<MCSymbolCOFF>(S)->setExternal(true);
354 }
355
finalizeCGProfile()356 void MCWinCOFFStreamer::finalizeCGProfile() {
357 for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
358 finalizeCGProfileEntry(E.From);
359 finalizeCGProfileEntry(E.To);
360 }
361 }
362
finishImpl()363 void MCWinCOFFStreamer::finishImpl() {
364 finalizeCGProfile();
365
366 MCObjectStreamer::finishImpl();
367 }
368
Error(const Twine & Msg) const369 void MCWinCOFFStreamer::Error(const Twine &Msg) const {
370 getContext().reportError(SMLoc(), Msg);
371 }
372