1 //===- lib/MC/MCELFStreamer.cpp - ELF Object Output -----------------------===//
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 assembles .s files and emits ELF .o object files.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "llvm/MC/MCELFStreamer.h"
14 #include "llvm/ADT/SmallString.h"
15 #include "llvm/ADT/SmallVector.h"
16 #include "llvm/BinaryFormat/ELF.h"
17 #include "llvm/MC/MCAsmBackend.h"
18 #include "llvm/MC/MCAsmInfo.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/MCObjectWriter.h"
27 #include "llvm/MC/MCSection.h"
28 #include "llvm/MC/MCSectionELF.h"
29 #include "llvm/MC/MCStreamer.h"
30 #include "llvm/MC/MCSymbol.h"
31 #include "llvm/MC/MCSymbolELF.h"
32 #include "llvm/Support/Casting.h"
33 #include "llvm/Support/ErrorHandling.h"
34 #include "llvm/Support/TargetRegistry.h"
35 #include "llvm/Support/raw_ostream.h"
36 #include <cassert>
37 #include <cstdint>
38
39 using namespace llvm;
40
MCELFStreamer(MCContext & Context,std::unique_ptr<MCAsmBackend> TAB,std::unique_ptr<MCObjectWriter> OW,std::unique_ptr<MCCodeEmitter> Emitter)41 MCELFStreamer::MCELFStreamer(MCContext &Context,
42 std::unique_ptr<MCAsmBackend> TAB,
43 std::unique_ptr<MCObjectWriter> OW,
44 std::unique_ptr<MCCodeEmitter> Emitter)
45 : MCObjectStreamer(Context, std::move(TAB), std::move(OW),
46 std::move(Emitter)) {}
47
isBundleLocked() const48 bool MCELFStreamer::isBundleLocked() const {
49 return getCurrentSectionOnly()->isBundleLocked();
50 }
51
mergeFragment(MCDataFragment * DF,MCDataFragment * EF)52 void MCELFStreamer::mergeFragment(MCDataFragment *DF,
53 MCDataFragment *EF) {
54 MCAssembler &Assembler = getAssembler();
55
56 if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
57 uint64_t FSize = EF->getContents().size();
58
59 if (FSize > Assembler.getBundleAlignSize())
60 report_fatal_error("Fragment can't be larger than a bundle size");
61
62 uint64_t RequiredBundlePadding = computeBundlePadding(
63 Assembler, EF, DF->getContents().size(), FSize);
64
65 if (RequiredBundlePadding > UINT8_MAX)
66 report_fatal_error("Padding cannot exceed 255 bytes");
67
68 if (RequiredBundlePadding > 0) {
69 SmallString<256> Code;
70 raw_svector_ostream VecOS(Code);
71 EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
72 Assembler.writeFragmentPadding(VecOS, *EF, FSize);
73
74 DF->getContents().append(Code.begin(), Code.end());
75 }
76 }
77
78 flushPendingLabels(DF, DF->getContents().size());
79
80 for (unsigned i = 0, e = EF->getFixups().size(); i != e; ++i) {
81 EF->getFixups()[i].setOffset(EF->getFixups()[i].getOffset() +
82 DF->getContents().size());
83 DF->getFixups().push_back(EF->getFixups()[i]);
84 }
85 if (DF->getSubtargetInfo() == nullptr && EF->getSubtargetInfo())
86 DF->setHasInstructions(*EF->getSubtargetInfo());
87 DF->getContents().append(EF->getContents().begin(), EF->getContents().end());
88 }
89
InitSections(bool NoExecStack)90 void MCELFStreamer::InitSections(bool NoExecStack) {
91 MCContext &Ctx = getContext();
92 SwitchSection(Ctx.getObjectFileInfo()->getTextSection());
93 emitCodeAlignment(4);
94
95 if (NoExecStack)
96 SwitchSection(Ctx.getAsmInfo()->getNonexecutableStackSection(Ctx));
97 }
98
emitLabel(MCSymbol * S,SMLoc Loc)99 void MCELFStreamer::emitLabel(MCSymbol *S, SMLoc Loc) {
100 auto *Symbol = cast<MCSymbolELF>(S);
101 MCObjectStreamer::emitLabel(Symbol, Loc);
102
103 const MCSectionELF &Section =
104 static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
105 if (Section.getFlags() & ELF::SHF_TLS)
106 Symbol->setType(ELF::STT_TLS);
107 }
108
emitLabelAtPos(MCSymbol * S,SMLoc Loc,MCFragment * F,uint64_t Offset)109 void MCELFStreamer::emitLabelAtPos(MCSymbol *S, SMLoc Loc, MCFragment *F,
110 uint64_t Offset) {
111 auto *Symbol = cast<MCSymbolELF>(S);
112 MCObjectStreamer::emitLabelAtPos(Symbol, Loc, F, Offset);
113
114 const MCSectionELF &Section =
115 static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
116 if (Section.getFlags() & ELF::SHF_TLS)
117 Symbol->setType(ELF::STT_TLS);
118 }
119
emitAssemblerFlag(MCAssemblerFlag Flag)120 void MCELFStreamer::emitAssemblerFlag(MCAssemblerFlag Flag) {
121 // Let the target do whatever target specific stuff it needs to do.
122 getAssembler().getBackend().handleAssemblerFlag(Flag);
123 // Do any generic stuff we need to do.
124 switch (Flag) {
125 case MCAF_SyntaxUnified: return; // no-op here.
126 case MCAF_Code16: return; // Change parsing mode; no-op here.
127 case MCAF_Code32: return; // Change parsing mode; no-op here.
128 case MCAF_Code64: return; // Change parsing mode; no-op here.
129 case MCAF_SubsectionsViaSymbols:
130 getAssembler().setSubsectionsViaSymbols(true);
131 return;
132 }
133
134 llvm_unreachable("invalid assembler flag!");
135 }
136
137 // If bundle alignment is used and there are any instructions in the section, it
138 // needs to be aligned to at least the bundle size.
setSectionAlignmentForBundling(const MCAssembler & Assembler,MCSection * Section)139 static void setSectionAlignmentForBundling(const MCAssembler &Assembler,
140 MCSection *Section) {
141 if (Section && Assembler.isBundlingEnabled() && Section->hasInstructions() &&
142 Section->getAlignment() < Assembler.getBundleAlignSize())
143 Section->setAlignment(Align(Assembler.getBundleAlignSize()));
144 }
145
changeSection(MCSection * Section,const MCExpr * Subsection)146 void MCELFStreamer::changeSection(MCSection *Section,
147 const MCExpr *Subsection) {
148 MCSection *CurSection = getCurrentSectionOnly();
149 if (CurSection && isBundleLocked())
150 report_fatal_error("Unterminated .bundle_lock when changing a section");
151
152 MCAssembler &Asm = getAssembler();
153 // Ensure the previous section gets aligned if necessary.
154 setSectionAlignmentForBundling(Asm, CurSection);
155 auto *SectionELF = static_cast<const MCSectionELF *>(Section);
156 const MCSymbol *Grp = SectionELF->getGroup();
157 if (Grp)
158 Asm.registerSymbol(*Grp);
159
160 changeSectionImpl(Section, Subsection);
161 Asm.registerSymbol(*Section->getBeginSymbol());
162 }
163
emitWeakReference(MCSymbol * Alias,const MCSymbol * Symbol)164 void MCELFStreamer::emitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
165 getAssembler().registerSymbol(*Symbol);
166 const MCExpr *Value = MCSymbolRefExpr::create(
167 Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext());
168 Alias->setVariableValue(Value);
169 }
170
171 // When GNU as encounters more than one .type declaration for an object it seems
172 // to use a mechanism similar to the one below to decide which type is actually
173 // used in the object file. The greater of T1 and T2 is selected based on the
174 // following ordering:
175 // STT_NOTYPE < STT_OBJECT < STT_FUNC < STT_GNU_IFUNC < STT_TLS < anything else
176 // If neither T1 < T2 nor T2 < T1 according to this ordering, use T2 (the user
177 // provided type).
CombineSymbolTypes(unsigned T1,unsigned T2)178 static unsigned CombineSymbolTypes(unsigned T1, unsigned T2) {
179 for (unsigned Type : {ELF::STT_NOTYPE, ELF::STT_OBJECT, ELF::STT_FUNC,
180 ELF::STT_GNU_IFUNC, ELF::STT_TLS}) {
181 if (T1 == Type)
182 return T2;
183 if (T2 == Type)
184 return T1;
185 }
186
187 return T2;
188 }
189
emitSymbolAttribute(MCSymbol * S,MCSymbolAttr Attribute)190 bool MCELFStreamer::emitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
191 auto *Symbol = cast<MCSymbolELF>(S);
192
193 // Adding a symbol attribute always introduces the symbol, note that an
194 // important side effect of calling registerSymbol here is to register
195 // the symbol with the assembler.
196 getAssembler().registerSymbol(*Symbol);
197
198 // The implementation of symbol attributes is designed to match 'as', but it
199 // leaves much to desired. It doesn't really make sense to arbitrarily add and
200 // remove flags, but 'as' allows this (in particular, see .desc).
201 //
202 // In the future it might be worth trying to make these operations more well
203 // defined.
204 switch (Attribute) {
205 case MCSA_Cold:
206 case MCSA_Extern:
207 case MCSA_LazyReference:
208 case MCSA_Reference:
209 case MCSA_SymbolResolver:
210 case MCSA_PrivateExtern:
211 case MCSA_WeakDefinition:
212 case MCSA_WeakDefAutoPrivate:
213 case MCSA_Invalid:
214 case MCSA_IndirectSymbol:
215 return false;
216
217 case MCSA_NoDeadStrip:
218 // Ignore for now.
219 break;
220
221 case MCSA_ELF_TypeGnuUniqueObject:
222 Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
223 Symbol->setBinding(ELF::STB_GNU_UNIQUE);
224 break;
225
226 case MCSA_Global:
227 // For `.weak x; .global x`, GNU as sets the binding to STB_WEAK while we
228 // traditionally set the binding to STB_GLOBAL. This is error-prone, so we
229 // error on such cases. Note, we also disallow changed binding from .local.
230 if (Symbol->isBindingSet() && Symbol->getBinding() != ELF::STB_GLOBAL)
231 getContext().reportError(getStartTokLoc(),
232 Symbol->getName() +
233 " changed binding to STB_GLOBAL");
234 Symbol->setBinding(ELF::STB_GLOBAL);
235 break;
236
237 case MCSA_WeakReference:
238 case MCSA_Weak:
239 // For `.global x; .weak x`, both MC and GNU as set the binding to STB_WEAK.
240 // We emit a warning for now but may switch to an error in the future.
241 if (Symbol->isBindingSet() && Symbol->getBinding() != ELF::STB_WEAK)
242 getContext().reportWarning(
243 getStartTokLoc(), Symbol->getName() + " changed binding to STB_WEAK");
244 Symbol->setBinding(ELF::STB_WEAK);
245 break;
246
247 case MCSA_Local:
248 if (Symbol->isBindingSet() && Symbol->getBinding() != ELF::STB_LOCAL)
249 getContext().reportError(getStartTokLoc(),
250 Symbol->getName() +
251 " changed binding to STB_LOCAL");
252 Symbol->setBinding(ELF::STB_LOCAL);
253 break;
254
255 case MCSA_ELF_TypeFunction:
256 Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_FUNC));
257 break;
258
259 case MCSA_ELF_TypeIndFunction:
260 Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_GNU_IFUNC));
261 break;
262
263 case MCSA_ELF_TypeObject:
264 Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
265 break;
266
267 case MCSA_ELF_TypeTLS:
268 Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_TLS));
269 break;
270
271 case MCSA_ELF_TypeCommon:
272 // TODO: Emit these as a common symbol.
273 Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
274 break;
275
276 case MCSA_ELF_TypeNoType:
277 Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_NOTYPE));
278 break;
279
280 case MCSA_Protected:
281 Symbol->setVisibility(ELF::STV_PROTECTED);
282 break;
283
284 case MCSA_Hidden:
285 Symbol->setVisibility(ELF::STV_HIDDEN);
286 break;
287
288 case MCSA_Internal:
289 Symbol->setVisibility(ELF::STV_INTERNAL);
290 break;
291
292 case MCSA_AltEntry:
293 llvm_unreachable("ELF doesn't support the .alt_entry attribute");
294
295 case MCSA_LGlobal:
296 llvm_unreachable("ELF doesn't support the .lglobl attribute");
297 }
298
299 return true;
300 }
301
emitCommonSymbol(MCSymbol * S,uint64_t Size,unsigned ByteAlignment)302 void MCELFStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
303 unsigned ByteAlignment) {
304 auto *Symbol = cast<MCSymbolELF>(S);
305 getAssembler().registerSymbol(*Symbol);
306
307 if (!Symbol->isBindingSet())
308 Symbol->setBinding(ELF::STB_GLOBAL);
309
310 Symbol->setType(ELF::STT_OBJECT);
311
312 if (Symbol->getBinding() == ELF::STB_LOCAL) {
313 MCSection &Section = *getAssembler().getContext().getELFSection(
314 ".bss", ELF::SHT_NOBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
315 MCSectionSubPair P = getCurrentSection();
316 SwitchSection(&Section);
317
318 emitValueToAlignment(ByteAlignment, 0, 1, 0);
319 emitLabel(Symbol);
320 emitZeros(Size);
321
322 SwitchSection(P.first, P.second);
323 } else {
324 if(Symbol->declareCommon(Size, ByteAlignment))
325 report_fatal_error("Symbol: " + Symbol->getName() +
326 " redeclared as different type");
327 }
328
329 cast<MCSymbolELF>(Symbol)
330 ->setSize(MCConstantExpr::create(Size, getContext()));
331 }
332
emitELFSize(MCSymbol * Symbol,const MCExpr * Value)333 void MCELFStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
334 cast<MCSymbolELF>(Symbol)->setSize(Value);
335 }
336
emitELFSymverDirective(StringRef AliasName,const MCSymbol * Aliasee)337 void MCELFStreamer::emitELFSymverDirective(StringRef AliasName,
338 const MCSymbol *Aliasee) {
339 getAssembler().Symvers.push_back(
340 MCAssembler::Symver{AliasName, Aliasee, getStartTokLoc()});
341 }
342
emitLocalCommonSymbol(MCSymbol * S,uint64_t Size,unsigned ByteAlignment)343 void MCELFStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
344 unsigned ByteAlignment) {
345 auto *Symbol = cast<MCSymbolELF>(S);
346 // FIXME: Should this be caught and done earlier?
347 getAssembler().registerSymbol(*Symbol);
348 Symbol->setBinding(ELF::STB_LOCAL);
349 emitCommonSymbol(Symbol, Size, ByteAlignment);
350 }
351
emitValueImpl(const MCExpr * Value,unsigned Size,SMLoc Loc)352 void MCELFStreamer::emitValueImpl(const MCExpr *Value, unsigned Size,
353 SMLoc Loc) {
354 if (isBundleLocked())
355 report_fatal_error("Emitting values inside a locked bundle is forbidden");
356 fixSymbolsInTLSFixups(Value);
357 MCObjectStreamer::emitValueImpl(Value, Size, Loc);
358 }
359
emitValueToAlignment(unsigned ByteAlignment,int64_t Value,unsigned ValueSize,unsigned MaxBytesToEmit)360 void MCELFStreamer::emitValueToAlignment(unsigned ByteAlignment,
361 int64_t Value,
362 unsigned ValueSize,
363 unsigned MaxBytesToEmit) {
364 if (isBundleLocked())
365 report_fatal_error("Emitting values inside a locked bundle is forbidden");
366 MCObjectStreamer::emitValueToAlignment(ByteAlignment, Value,
367 ValueSize, MaxBytesToEmit);
368 }
369
emitCGProfileEntry(const MCSymbolRefExpr * From,const MCSymbolRefExpr * To,uint64_t Count)370 void MCELFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
371 const MCSymbolRefExpr *To,
372 uint64_t Count) {
373 getAssembler().CGProfile.push_back({From, To, Count});
374 }
375
emitIdent(StringRef IdentString)376 void MCELFStreamer::emitIdent(StringRef IdentString) {
377 MCSection *Comment = getAssembler().getContext().getELFSection(
378 ".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
379 PushSection();
380 SwitchSection(Comment);
381 if (!SeenIdent) {
382 emitInt8(0);
383 SeenIdent = true;
384 }
385 emitBytes(IdentString);
386 emitInt8(0);
387 PopSection();
388 }
389
fixSymbolsInTLSFixups(const MCExpr * expr)390 void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
391 switch (expr->getKind()) {
392 case MCExpr::Target:
393 cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
394 break;
395 case MCExpr::Constant:
396 break;
397
398 case MCExpr::Binary: {
399 const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
400 fixSymbolsInTLSFixups(be->getLHS());
401 fixSymbolsInTLSFixups(be->getRHS());
402 break;
403 }
404
405 case MCExpr::SymbolRef: {
406 const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
407 switch (symRef.getKind()) {
408 default:
409 return;
410 case MCSymbolRefExpr::VK_GOTTPOFF:
411 case MCSymbolRefExpr::VK_INDNTPOFF:
412 case MCSymbolRefExpr::VK_NTPOFF:
413 case MCSymbolRefExpr::VK_GOTNTPOFF:
414 case MCSymbolRefExpr::VK_TLSCALL:
415 case MCSymbolRefExpr::VK_TLSDESC:
416 case MCSymbolRefExpr::VK_TLSGD:
417 case MCSymbolRefExpr::VK_TLSLD:
418 case MCSymbolRefExpr::VK_TLSLDM:
419 case MCSymbolRefExpr::VK_TPOFF:
420 case MCSymbolRefExpr::VK_TPREL:
421 case MCSymbolRefExpr::VK_DTPOFF:
422 case MCSymbolRefExpr::VK_DTPREL:
423 case MCSymbolRefExpr::VK_PPC_DTPMOD:
424 case MCSymbolRefExpr::VK_PPC_TPREL_LO:
425 case MCSymbolRefExpr::VK_PPC_TPREL_HI:
426 case MCSymbolRefExpr::VK_PPC_TPREL_HA:
427 case MCSymbolRefExpr::VK_PPC_TPREL_HIGH:
428 case MCSymbolRefExpr::VK_PPC_TPREL_HIGHA:
429 case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
430 case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
431 case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
432 case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
433 case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
434 case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
435 case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
436 case MCSymbolRefExpr::VK_PPC_DTPREL_HIGH:
437 case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHA:
438 case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
439 case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
440 case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
441 case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
442 case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
443 case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
444 case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
445 case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
446 case MCSymbolRefExpr::VK_PPC_GOT_TPREL_PCREL:
447 case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
448 case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
449 case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
450 case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
451 case MCSymbolRefExpr::VK_PPC_TLS:
452 case MCSymbolRefExpr::VK_PPC_TLS_PCREL:
453 case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
454 case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
455 case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
456 case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
457 case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_PCREL:
458 case MCSymbolRefExpr::VK_PPC_TLSGD:
459 case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
460 case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
461 case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
462 case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
463 case MCSymbolRefExpr::VK_PPC_TLSLD:
464 break;
465 }
466 getAssembler().registerSymbol(symRef.getSymbol());
467 cast<MCSymbolELF>(symRef.getSymbol()).setType(ELF::STT_TLS);
468 break;
469 }
470
471 case MCExpr::Unary:
472 fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
473 break;
474 }
475 }
476
finalizeCGProfileEntry(const MCSymbolRefExpr * & SRE)477 void MCELFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
478 const MCSymbol *S = &SRE->getSymbol();
479 if (S->isTemporary()) {
480 if (!S->isInSection()) {
481 getContext().reportError(
482 SRE->getLoc(), Twine("Reference to undefined temporary symbol ") +
483 "`" + S->getName() + "`");
484 return;
485 }
486 S = S->getSection().getBeginSymbol();
487 S->setUsedInReloc();
488 SRE =
489 MCSymbolRefExpr::create(S, SRE->getKind(), getContext(), SRE->getLoc());
490 return;
491 }
492 // Not a temporary, referece it as a weak undefined.
493 bool Created;
494 getAssembler().registerSymbol(*S, &Created);
495 if (Created)
496 cast<MCSymbolELF>(S)->setBinding(ELF::STB_WEAK);
497 }
498
finalizeCGProfile()499 void MCELFStreamer::finalizeCGProfile() {
500 for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
501 finalizeCGProfileEntry(E.From);
502 finalizeCGProfileEntry(E.To);
503 }
504 }
505
emitInstToFragment(const MCInst & Inst,const MCSubtargetInfo & STI)506 void MCELFStreamer::emitInstToFragment(const MCInst &Inst,
507 const MCSubtargetInfo &STI) {
508 this->MCObjectStreamer::emitInstToFragment(Inst, STI);
509 MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
510
511 for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
512 fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
513 }
514
515 // A fragment can only have one Subtarget, and when bundling is enabled we
516 // sometimes need to use the same fragment. We give an error if there
517 // are conflicting Subtargets.
CheckBundleSubtargets(const MCSubtargetInfo * OldSTI,const MCSubtargetInfo * NewSTI)518 static void CheckBundleSubtargets(const MCSubtargetInfo *OldSTI,
519 const MCSubtargetInfo *NewSTI) {
520 if (OldSTI && NewSTI && OldSTI != NewSTI)
521 report_fatal_error("A Bundle can only have one Subtarget.");
522 }
523
emitInstToData(const MCInst & Inst,const MCSubtargetInfo & STI)524 void MCELFStreamer::emitInstToData(const MCInst &Inst,
525 const MCSubtargetInfo &STI) {
526 MCAssembler &Assembler = getAssembler();
527 SmallVector<MCFixup, 4> Fixups;
528 SmallString<256> Code;
529 raw_svector_ostream VecOS(Code);
530 Assembler.getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
531
532 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
533 fixSymbolsInTLSFixups(Fixups[i].getValue());
534
535 // There are several possibilities here:
536 //
537 // If bundling is disabled, append the encoded instruction to the current data
538 // fragment (or create a new such fragment if the current fragment is not a
539 // data fragment, or the Subtarget has changed).
540 //
541 // If bundling is enabled:
542 // - If we're not in a bundle-locked group, emit the instruction into a
543 // fragment of its own. If there are no fixups registered for the
544 // instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
545 // MCDataFragment.
546 // - If we're in a bundle-locked group, append the instruction to the current
547 // data fragment because we want all the instructions in a group to get into
548 // the same fragment. Be careful not to do that for the first instruction in
549 // the group, though.
550 MCDataFragment *DF;
551
552 if (Assembler.isBundlingEnabled()) {
553 MCSection &Sec = *getCurrentSectionOnly();
554 if (Assembler.getRelaxAll() && isBundleLocked()) {
555 // If the -mc-relax-all flag is used and we are bundle-locked, we re-use
556 // the current bundle group.
557 DF = BundleGroups.back();
558 CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
559 }
560 else if (Assembler.getRelaxAll() && !isBundleLocked())
561 // When not in a bundle-locked group and the -mc-relax-all flag is used,
562 // we create a new temporary fragment which will be later merged into
563 // the current fragment.
564 DF = new MCDataFragment();
565 else if (isBundleLocked() && !Sec.isBundleGroupBeforeFirstInst()) {
566 // If we are bundle-locked, we re-use the current fragment.
567 // The bundle-locking directive ensures this is a new data fragment.
568 DF = cast<MCDataFragment>(getCurrentFragment());
569 CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
570 }
571 else if (!isBundleLocked() && Fixups.size() == 0) {
572 // Optimize memory usage by emitting the instruction to a
573 // MCCompactEncodedInstFragment when not in a bundle-locked group and
574 // there are no fixups registered.
575 MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
576 insert(CEIF);
577 CEIF->getContents().append(Code.begin(), Code.end());
578 CEIF->setHasInstructions(STI);
579 return;
580 } else {
581 DF = new MCDataFragment();
582 insert(DF);
583 }
584 if (Sec.getBundleLockState() == MCSection::BundleLockedAlignToEnd) {
585 // If this fragment is for a group marked "align_to_end", set a flag
586 // in the fragment. This can happen after the fragment has already been
587 // created if there are nested bundle_align groups and an inner one
588 // is the one marked align_to_end.
589 DF->setAlignToBundleEnd(true);
590 }
591
592 // We're now emitting an instruction in a bundle group, so this flag has
593 // to be turned off.
594 Sec.setBundleGroupBeforeFirstInst(false);
595 } else {
596 DF = getOrCreateDataFragment(&STI);
597 }
598
599 // Add the fixups and data.
600 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
601 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
602 DF->getFixups().push_back(Fixups[i]);
603 }
604 DF->setHasInstructions(STI);
605 DF->getContents().append(Code.begin(), Code.end());
606
607 if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
608 if (!isBundleLocked()) {
609 mergeFragment(getOrCreateDataFragment(&STI), DF);
610 delete DF;
611 }
612 }
613 }
614
emitBundleAlignMode(unsigned AlignPow2)615 void MCELFStreamer::emitBundleAlignMode(unsigned AlignPow2) {
616 assert(AlignPow2 <= 30 && "Invalid bundle alignment");
617 MCAssembler &Assembler = getAssembler();
618 if (AlignPow2 > 0 && (Assembler.getBundleAlignSize() == 0 ||
619 Assembler.getBundleAlignSize() == 1U << AlignPow2))
620 Assembler.setBundleAlignSize(1U << AlignPow2);
621 else
622 report_fatal_error(".bundle_align_mode cannot be changed once set");
623 }
624
emitBundleLock(bool AlignToEnd)625 void MCELFStreamer::emitBundleLock(bool AlignToEnd) {
626 MCSection &Sec = *getCurrentSectionOnly();
627
628 // Sanity checks
629 //
630 if (!getAssembler().isBundlingEnabled())
631 report_fatal_error(".bundle_lock forbidden when bundling is disabled");
632
633 if (!isBundleLocked())
634 Sec.setBundleGroupBeforeFirstInst(true);
635
636 if (getAssembler().getRelaxAll() && !isBundleLocked()) {
637 // TODO: drop the lock state and set directly in the fragment
638 MCDataFragment *DF = new MCDataFragment();
639 BundleGroups.push_back(DF);
640 }
641
642 Sec.setBundleLockState(AlignToEnd ? MCSection::BundleLockedAlignToEnd
643 : MCSection::BundleLocked);
644 }
645
emitBundleUnlock()646 void MCELFStreamer::emitBundleUnlock() {
647 MCSection &Sec = *getCurrentSectionOnly();
648
649 // Sanity checks
650 if (!getAssembler().isBundlingEnabled())
651 report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
652 else if (!isBundleLocked())
653 report_fatal_error(".bundle_unlock without matching lock");
654 else if (Sec.isBundleGroupBeforeFirstInst())
655 report_fatal_error("Empty bundle-locked group is forbidden");
656
657 // When the -mc-relax-all flag is used, we emit instructions to fragments
658 // stored on a stack. When the bundle unlock is emitted, we pop a fragment
659 // from the stack a merge it to the one below.
660 if (getAssembler().getRelaxAll()) {
661 assert(!BundleGroups.empty() && "There are no bundle groups");
662 MCDataFragment *DF = BundleGroups.back();
663
664 // FIXME: Use BundleGroups to track the lock state instead.
665 Sec.setBundleLockState(MCSection::NotBundleLocked);
666
667 // FIXME: Use more separate fragments for nested groups.
668 if (!isBundleLocked()) {
669 mergeFragment(getOrCreateDataFragment(DF->getSubtargetInfo()), DF);
670 BundleGroups.pop_back();
671 delete DF;
672 }
673
674 if (Sec.getBundleLockState() != MCSection::BundleLockedAlignToEnd)
675 getOrCreateDataFragment()->setAlignToBundleEnd(false);
676 } else
677 Sec.setBundleLockState(MCSection::NotBundleLocked);
678 }
679
finishImpl()680 void MCELFStreamer::finishImpl() {
681 // Ensure the last section gets aligned if necessary.
682 MCSection *CurSection = getCurrentSectionOnly();
683 setSectionAlignmentForBundling(getAssembler(), CurSection);
684
685 finalizeCGProfile();
686 emitFrames(nullptr);
687
688 this->MCObjectStreamer::finishImpl();
689 }
690
emitThumbFunc(MCSymbol * Func)691 void MCELFStreamer::emitThumbFunc(MCSymbol *Func) {
692 llvm_unreachable("Generic ELF doesn't support this directive");
693 }
694
emitSymbolDesc(MCSymbol * Symbol,unsigned DescValue)695 void MCELFStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
696 llvm_unreachable("ELF doesn't support this directive");
697 }
698
emitZerofill(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment,SMLoc Loc)699 void MCELFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
700 uint64_t Size, unsigned ByteAlignment,
701 SMLoc Loc) {
702 llvm_unreachable("ELF doesn't support this directive");
703 }
704
emitTBSSSymbol(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)705 void MCELFStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
706 uint64_t Size, unsigned ByteAlignment) {
707 llvm_unreachable("ELF doesn't support this directive");
708 }
709
createELFStreamer(MCContext & Context,std::unique_ptr<MCAsmBackend> && MAB,std::unique_ptr<MCObjectWriter> && OW,std::unique_ptr<MCCodeEmitter> && CE,bool RelaxAll)710 MCStreamer *llvm::createELFStreamer(MCContext &Context,
711 std::unique_ptr<MCAsmBackend> &&MAB,
712 std::unique_ptr<MCObjectWriter> &&OW,
713 std::unique_ptr<MCCodeEmitter> &&CE,
714 bool RelaxAll) {
715 MCELFStreamer *S =
716 new MCELFStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
717 if (RelaxAll)
718 S->getAssembler().setRelaxAll(true);
719 return S;
720 }
721