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/MCSection.h"
29#include "llvm/MC/MCSymbolCOFF.h"
30#include "llvm/Support/Casting.h"
31#include "llvm/Support/ErrorHandling.h"
32#include "llvm/Support/MathExtras.h"
33#include "llvm/Support/SMLoc.h"
34#include "llvm/Support/raw_ostream.h"
35#include "llvm/TargetParser/Triple.h"
36#include <algorithm>
37#include <cstdint>
38
39using namespace llvm;
40
41#define DEBUG_TYPE "WinCOFFStreamer"
42
43MCWinCOFFStreamer::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
50void MCWinCOFFStreamer::emitInstToData(const MCInst &Inst,
51 const MCSubtargetInfo &STI) {
52 MCDataFragment *DF = getOrCreateDataFragment();
53
54 SmallVector<MCFixup, 4> Fixups;
55 SmallString<256> Code;
56 getAssembler().getEmitter().encodeInstruction(Inst, CB&: Code, Fixups, STI);
57
58 // Add the fixups and data.
59 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
60 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
61 DF->getFixups().push_back(Elt: Fixups[i]);
62 }
63 DF->setHasInstructions(STI);
64 DF->getContents().append(in_start: Code.begin(), in_end: Code.end());
65}
66
67void MCWinCOFFStreamer::initSections(bool NoExecStack,
68 const MCSubtargetInfo &STI) {
69 // FIXME: this is identical to the ELF one.
70 // This emulates the same behavior of GNU as. This makes it easier
71 // to compare the output as the major sections are in the same order.
72 switchSection(Section: getContext().getObjectFileInfo()->getTextSection());
73 emitCodeAlignment(ByteAlignment: Align(4), STI: &STI);
74
75 switchSection(Section: getContext().getObjectFileInfo()->getDataSection());
76 emitCodeAlignment(ByteAlignment: Align(4), STI: &STI);
77
78 switchSection(Section: getContext().getObjectFileInfo()->getBSSSection());
79 emitCodeAlignment(ByteAlignment: Align(4), STI: &STI);
80
81 switchSection(Section: getContext().getObjectFileInfo()->getTextSection());
82}
83
84void MCWinCOFFStreamer::emitLabel(MCSymbol *S, SMLoc Loc) {
85 auto *Symbol = cast<MCSymbolCOFF>(Val: S);
86 MCObjectStreamer::emitLabel(Symbol, Loc);
87}
88
89void MCWinCOFFStreamer::emitAssemblerFlag(MCAssemblerFlag Flag) {
90 // Let the target do whatever target specific stuff it needs to do.
91 getAssembler().getBackend().handleAssemblerFlag(Flag);
92
93 switch (Flag) {
94 // None of these require COFF specific handling.
95 case MCAF_SyntaxUnified:
96 case MCAF_Code16:
97 case MCAF_Code32:
98 case MCAF_Code64:
99 break;
100 case MCAF_SubsectionsViaSymbols:
101 llvm_unreachable("COFF doesn't support .subsections_via_symbols");
102 }
103}
104
105void MCWinCOFFStreamer::emitThumbFunc(MCSymbol *Func) {
106 llvm_unreachable("not implemented");
107}
108
109bool MCWinCOFFStreamer::emitSymbolAttribute(MCSymbol *S,
110 MCSymbolAttr Attribute) {
111 auto *Symbol = cast<MCSymbolCOFF>(Val: S);
112 getAssembler().registerSymbol(Symbol: *Symbol);
113
114 switch (Attribute) {
115 default: return false;
116 case MCSA_WeakReference:
117 case MCSA_Weak:
118 Symbol->setWeakExternalCharacteristics(COFF::IMAGE_WEAK_EXTERN_SEARCH_ALIAS);
119 Symbol->setExternal(true);
120 break;
121 case MCSA_WeakAntiDep:
122 Symbol->setWeakExternalCharacteristics(COFF::IMAGE_WEAK_EXTERN_ANTI_DEPENDENCY);
123 Symbol->setExternal(true);
124 Symbol->setIsWeakExternal(true);
125 break;
126 case MCSA_Global:
127 Symbol->setExternal(true);
128 break;
129 case MCSA_AltEntry:
130 llvm_unreachable("COFF doesn't support the .alt_entry attribute");
131 }
132
133 return true;
134}
135
136void MCWinCOFFStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
137 llvm_unreachable("not implemented");
138}
139
140void MCWinCOFFStreamer::beginCOFFSymbolDef(MCSymbol const *S) {
141 auto *Symbol = cast<MCSymbolCOFF>(Val: S);
142 if (CurSymbol)
143 Error(Msg: "starting a new symbol definition without completing the "
144 "previous one");
145 CurSymbol = Symbol;
146}
147
148void MCWinCOFFStreamer::emitCOFFSymbolStorageClass(int StorageClass) {
149 if (!CurSymbol) {
150 Error(Msg: "storage class specified outside of symbol definition");
151 return;
152 }
153
154 if (StorageClass & ~COFF::SSC_Invalid) {
155 Error(Msg: "storage class value '" + Twine(StorageClass) +
156 "' out of range");
157 return;
158 }
159
160 getAssembler().registerSymbol(Symbol: *CurSymbol);
161 cast<MCSymbolCOFF>(Val: CurSymbol)->setClass((uint16_t)StorageClass);
162}
163
164void MCWinCOFFStreamer::emitCOFFSymbolType(int Type) {
165 if (!CurSymbol) {
166 Error(Msg: "symbol type specified outside of a symbol definition");
167 return;
168 }
169
170 if (Type & ~0xffff) {
171 Error(Msg: "type value '" + Twine(Type) + "' out of range");
172 return;
173 }
174
175 getAssembler().registerSymbol(Symbol: *CurSymbol);
176 cast<MCSymbolCOFF>(Val: CurSymbol)->setType((uint16_t)Type);
177}
178
179void MCWinCOFFStreamer::endCOFFSymbolDef() {
180 if (!CurSymbol)
181 Error(Msg: "ending symbol definition without starting one");
182 CurSymbol = nullptr;
183}
184
185void MCWinCOFFStreamer::emitCOFFSafeSEH(MCSymbol const *Symbol) {
186 // SafeSEH is a feature specific to 32-bit x86. It does not exist (and is
187 // unnecessary) on all platforms which use table-based exception dispatch.
188 if (getContext().getTargetTriple().getArch() != Triple::x86)
189 return;
190
191 const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Val: Symbol);
192 if (CSymbol->isSafeSEH())
193 return;
194
195 MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection();
196 getAssembler().registerSection(Section&: *SXData);
197 SXData->ensureMinAlignment(MinAlignment: Align(4));
198
199 new MCSymbolIdFragment(Symbol, SXData);
200
201 getAssembler().registerSymbol(Symbol: *Symbol);
202 CSymbol->setIsSafeSEH();
203
204 // The Microsoft linker requires that the symbol type of a handler be
205 // function. Go ahead and oblige it here.
206 CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
207 << COFF::SCT_COMPLEX_TYPE_SHIFT);
208}
209
210void MCWinCOFFStreamer::emitCOFFSymbolIndex(MCSymbol const *Symbol) {
211 MCSection *Sec = getCurrentSectionOnly();
212 getAssembler().registerSection(Section&: *Sec);
213 Sec->ensureMinAlignment(MinAlignment: Align(4));
214
215 new MCSymbolIdFragment(Symbol, getCurrentSectionOnly());
216
217 getAssembler().registerSymbol(Symbol: *Symbol);
218}
219
220void MCWinCOFFStreamer::emitCOFFSectionIndex(const MCSymbol *Symbol) {
221 visitUsedSymbol(Sym: *Symbol);
222 MCDataFragment *DF = getOrCreateDataFragment();
223 const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, Ctx&: getContext());
224 MCFixup Fixup = MCFixup::create(Offset: DF->getContents().size(), Value: SRE, Kind: FK_SecRel_2);
225 DF->getFixups().push_back(Elt: Fixup);
226 DF->getContents().resize(N: DF->getContents().size() + 2, NV: 0);
227}
228
229void MCWinCOFFStreamer::emitCOFFSecRel32(const MCSymbol *Symbol,
230 uint64_t Offset) {
231 visitUsedSymbol(Sym: *Symbol);
232 MCDataFragment *DF = getOrCreateDataFragment();
233 // Create Symbol A for the relocation relative reference.
234 const MCExpr *MCE = MCSymbolRefExpr::create(Symbol, Ctx&: getContext());
235 // Add the constant offset, if given.
236 if (Offset)
237 MCE = MCBinaryExpr::createAdd(
238 LHS: MCE, RHS: MCConstantExpr::create(Value: Offset, Ctx&: getContext()), Ctx&: getContext());
239 // Build the secrel32 relocation.
240 MCFixup Fixup = MCFixup::create(Offset: DF->getContents().size(), Value: MCE, Kind: FK_SecRel_4);
241 // Record the relocation.
242 DF->getFixups().push_back(Elt: Fixup);
243 // Emit 4 bytes (zeros) to the object file.
244 DF->getContents().resize(N: DF->getContents().size() + 4, NV: 0);
245}
246
247void MCWinCOFFStreamer::emitCOFFImgRel32(const MCSymbol *Symbol,
248 int64_t Offset) {
249 visitUsedSymbol(Sym: *Symbol);
250 MCDataFragment *DF = getOrCreateDataFragment();
251 // Create Symbol A for the relocation relative reference.
252 const MCExpr *MCE = MCSymbolRefExpr::create(
253 Symbol, Kind: MCSymbolRefExpr::VK_COFF_IMGREL32, Ctx&: getContext());
254 // Add the constant offset, if given.
255 if (Offset)
256 MCE = MCBinaryExpr::createAdd(
257 LHS: MCE, RHS: MCConstantExpr::create(Value: Offset, Ctx&: getContext()), Ctx&: getContext());
258 // Build the imgrel relocation.
259 MCFixup Fixup = MCFixup::create(Offset: DF->getContents().size(), Value: MCE, Kind: FK_Data_4);
260 // Record the relocation.
261 DF->getFixups().push_back(Elt: Fixup);
262 // Emit 4 bytes (zeros) to the object file.
263 DF->getContents().resize(N: DF->getContents().size() + 4, NV: 0);
264}
265
266void MCWinCOFFStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
267 Align ByteAlignment) {
268 auto *Symbol = cast<MCSymbolCOFF>(Val: S);
269
270 const Triple &T = getContext().getTargetTriple();
271 if (T.isWindowsMSVCEnvironment()) {
272 if (ByteAlignment > 32)
273 report_fatal_error(reason: "alignment is limited to 32-bytes");
274
275 // Round size up to alignment so that we will honor the alignment request.
276 Size = std::max(a: Size, b: ByteAlignment.value());
277 }
278
279 getAssembler().registerSymbol(Symbol: *Symbol);
280 Symbol->setExternal(true);
281 Symbol->setCommon(Size, Alignment: ByteAlignment);
282
283 if (!T.isWindowsMSVCEnvironment() && ByteAlignment > 1) {
284 SmallString<128> Directive;
285 raw_svector_ostream OS(Directive);
286 const MCObjectFileInfo *MFI = getContext().getObjectFileInfo();
287
288 OS << " -aligncomm:\"" << Symbol->getName() << "\","
289 << Log2_32_Ceil(Value: ByteAlignment.value());
290
291 pushSection();
292 switchSection(Section: MFI->getDrectveSection());
293 emitBytes(Data: Directive);
294 popSection();
295 }
296}
297
298void MCWinCOFFStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
299 Align ByteAlignment) {
300 auto *Symbol = cast<MCSymbolCOFF>(Val: S);
301
302 MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
303 pushSection();
304 switchSection(Section);
305 emitValueToAlignment(Alignment: ByteAlignment, Value: 0, ValueSize: 1, MaxBytesToEmit: 0);
306 emitLabel(S: Symbol);
307 Symbol->setExternal(false);
308 emitZeros(NumBytes: Size);
309 popSection();
310}
311
312void MCWinCOFFStreamer::emitWeakReference(MCSymbol *AliasS,
313 const MCSymbol *Symbol) {
314 auto *Alias = cast<MCSymbolCOFF>(Val: AliasS);
315 emitSymbolAttribute(S: Alias, Attribute: MCSA_Weak);
316
317 getAssembler().registerSymbol(Symbol: *Symbol);
318 Alias->setVariableValue(MCSymbolRefExpr::create(
319 Symbol, Kind: MCSymbolRefExpr::VK_WEAKREF, Ctx&: getContext()));
320}
321
322void MCWinCOFFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
323 uint64_t Size, Align ByteAlignment,
324 SMLoc Loc) {
325 llvm_unreachable("not implemented");
326}
327
328void MCWinCOFFStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
329 uint64_t Size, Align ByteAlignment) {
330 llvm_unreachable("not implemented");
331}
332
333// TODO: Implement this if you want to emit .comment section in COFF obj files.
334void MCWinCOFFStreamer::emitIdent(StringRef IdentString) {
335 llvm_unreachable("not implemented");
336}
337
338void MCWinCOFFStreamer::emitWinEHHandlerData(SMLoc Loc) {
339 llvm_unreachable("not implemented");
340}
341
342void MCWinCOFFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
343 const MCSymbolRefExpr *To,
344 uint64_t Count) {
345 // Ignore temporary symbols for now.
346 if (!From->getSymbol().isTemporary() && !To->getSymbol().isTemporary())
347 getAssembler().CGProfile.push_back(x: {.From: From, .To: To, .Count: Count});
348}
349
350void MCWinCOFFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
351 const MCSymbol *S = &SRE->getSymbol();
352 if (getAssembler().registerSymbol(Symbol: *S))
353 cast<MCSymbolCOFF>(Val: S)->setExternal(true);
354}
355
356void MCWinCOFFStreamer::finalizeCGProfile() {
357 for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
358 finalizeCGProfileEntry(SRE&: E.From);
359 finalizeCGProfileEntry(SRE&: E.To);
360 }
361}
362
363void MCWinCOFFStreamer::finishImpl() {
364 finalizeCGProfile();
365
366 MCObjectStreamer::finishImpl();
367}
368
369void MCWinCOFFStreamer::Error(const Twine &Msg) const {
370 getContext().reportError(L: SMLoc(), Msg);
371}
372

source code of llvm/lib/MC/MCWinCOFFStreamer.cpp