1 //===- lib/MC/MCELFStreamer.cpp - ELF Object Output ------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file assembles .s files and emits ELF .o object files.
12 //===----------------------------------------------------------------------===//
14 #include "MCELFStreamer.h"
16 #include "llvm/MC/MCStreamer.h"
17 #include "llvm/MC/MCCodeEmitter.h"
18 #include "llvm/MC/MCELFSymbolFlags.h"
19 #include "llvm/MC/MCExpr.h"
20 #include "llvm/MC/MCInst.h"
21 #include "llvm/MC/MCSection.h"
22 #include "llvm/MC/MCSymbol.h"
23 #include "llvm/MC/MCValue.h"
24 #include "llvm/Support/Debug.h"
25 #include "llvm/Support/ELF.h"
26 #include "llvm/Support/ErrorHandling.h"
27 #include "llvm/Support/raw_ostream.h"
28 #include "llvm/Target/TargetAsmBackend.h"
29 #include "llvm/Target/TargetAsmInfo.h"
33 void MCELFStreamer::InitSections() {
34 // This emulates the same behavior of GNU as. This makes it easier
35 // to compare the output as the major sections are in the same order.
42 void MCELFStreamer::EmitLabel(MCSymbol *Symbol) {
43 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
45 MCObjectStreamer::EmitLabel(Symbol);
47 const MCSectionELF &Section =
48 static_cast<const MCSectionELF&>(Symbol->getSection());
49 MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
50 if (Section.getFlags() & ELF::SHF_TLS)
51 MCELF::SetType(SD, ELF::STT_TLS);
54 void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
56 case MCAF_SyntaxUnified: return; // no-op here.
57 case MCAF_Code16: return; // no-op here.
58 case MCAF_Code32: return; // no-op here.
59 case MCAF_SubsectionsViaSymbols:
60 getAssembler().setSubsectionsViaSymbols(true);
64 assert(0 && "invalid assembler flag!");
67 void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
68 // FIXME: Anything needed here to flag the function as thumb?
71 void MCELFStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
72 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
74 // FIXME: Lift context changes into super class.
75 getAssembler().getOrCreateSymbolData(*Symbol);
76 Symbol->setVariableValue(AddValueSymbols(Value));
79 void MCELFStreamer::ChangeSection(const MCSection *Section) {
80 const MCSymbol *Grp = static_cast<const MCSectionELF *>(Section)->getGroup();
82 getAssembler().getOrCreateSymbolData(*Grp);
83 this->MCObjectStreamer::ChangeSection(Section);
86 void MCELFStreamer::EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
87 getAssembler().getOrCreateSymbolData(*Symbol);
88 MCSymbolData &AliasSD = getAssembler().getOrCreateSymbolData(*Alias);
89 AliasSD.setFlags(AliasSD.getFlags() | ELF_Other_Weakref);
90 const MCExpr *Value = MCSymbolRefExpr::Create(Symbol, getContext());
91 Alias->setVariableValue(Value);
94 void MCELFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
95 MCSymbolAttr Attribute) {
96 // Indirect symbols are handled differently, to match how 'as' handles
97 // them. This makes writing matching .o files easier.
98 if (Attribute == MCSA_IndirectSymbol) {
99 // Note that we intentionally cannot use the symbol data here; this is
100 // important for matching the string table that 'as' generates.
101 IndirectSymbolData ISD;
103 ISD.SectionData = getCurrentSectionData();
104 getAssembler().getIndirectSymbols().push_back(ISD);
108 // Adding a symbol attribute always introduces the symbol, note that an
109 // important side effect of calling getOrCreateSymbolData here is to register
110 // the symbol with the assembler.
111 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
113 // The implementation of symbol attributes is designed to match 'as', but it
114 // leaves much to desired. It doesn't really make sense to arbitrarily add and
115 // remove flags, but 'as' allows this (in particular, see .desc).
117 // In the future it might be worth trying to make these operations more well
120 case MCSA_LazyReference:
122 case MCSA_NoDeadStrip:
123 case MCSA_SymbolResolver:
124 case MCSA_PrivateExtern:
125 case MCSA_WeakDefinition:
126 case MCSA_WeakDefAutoPrivate:
128 case MCSA_ELF_TypeIndFunction:
129 case MCSA_IndirectSymbol:
130 assert(0 && "Invalid symbol attribute for ELF!");
133 case MCSA_ELF_TypeGnuUniqueObject:
138 MCELF::SetBinding(SD, ELF::STB_GLOBAL);
139 SD.setExternal(true);
140 BindingExplicitlySet.insert(Symbol);
143 case MCSA_WeakReference:
145 MCELF::SetBinding(SD, ELF::STB_WEAK);
146 SD.setExternal(true);
147 BindingExplicitlySet.insert(Symbol);
151 MCELF::SetBinding(SD, ELF::STB_LOCAL);
152 SD.setExternal(false);
153 BindingExplicitlySet.insert(Symbol);
156 case MCSA_ELF_TypeFunction:
157 MCELF::SetType(SD, ELF::STT_FUNC);
160 case MCSA_ELF_TypeObject:
161 MCELF::SetType(SD, ELF::STT_OBJECT);
164 case MCSA_ELF_TypeTLS:
165 MCELF::SetType(SD, ELF::STT_TLS);
168 case MCSA_ELF_TypeCommon:
169 MCELF::SetType(SD, ELF::STT_COMMON);
172 case MCSA_ELF_TypeNoType:
173 MCELF::SetType(SD, ELF::STT_NOTYPE);
177 MCELF::SetVisibility(SD, ELF::STV_PROTECTED);
181 MCELF::SetVisibility(SD, ELF::STV_HIDDEN);
185 MCELF::SetVisibility(SD, ELF::STV_INTERNAL);
190 void MCELFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
191 unsigned ByteAlignment) {
192 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
194 if (!BindingExplicitlySet.count(Symbol)) {
195 MCELF::SetBinding(SD, ELF::STB_GLOBAL);
196 SD.setExternal(true);
199 MCELF::SetType(SD, ELF::STT_OBJECT);
201 if (MCELF::GetBinding(SD) == ELF_STB_Local) {
202 const MCSection *Section = getAssembler().getContext().getELFSection(".bss",
206 SectionKind::getBSS());
207 Symbol->setSection(*Section);
209 struct LocalCommon L = {&SD, Size, ByteAlignment};
210 LocalCommons.push_back(L);
212 SD.setCommon(Size, ByteAlignment);
215 SD.setSize(MCConstantExpr::Create(Size, getContext()));
218 void MCELFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
219 // FIXME: Should this be caught and done earlier?
220 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
221 MCELF::SetBinding(SD, ELF::STB_LOCAL);
222 SD.setExternal(false);
223 BindingExplicitlySet.insert(Symbol);
224 // FIXME: ByteAlignment is not needed here, but is required.
225 EmitCommonSymbol(Symbol, Size, 1);
228 void MCELFStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
229 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
231 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
234 void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
235 int64_t Value, unsigned ValueSize,
236 unsigned MaxBytesToEmit) {
237 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
239 if (MaxBytesToEmit == 0)
240 MaxBytesToEmit = ByteAlignment;
241 new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
242 getCurrentSectionData());
244 // Update the maximum alignment on the current section if necessary.
245 if (ByteAlignment > getCurrentSectionData()->getAlignment())
246 getCurrentSectionData()->setAlignment(ByteAlignment);
249 void MCELFStreamer::EmitCodeAlignment(unsigned ByteAlignment,
250 unsigned MaxBytesToEmit) {
251 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
253 if (MaxBytesToEmit == 0)
254 MaxBytesToEmit = ByteAlignment;
255 MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
256 getCurrentSectionData());
257 F->setEmitNops(true);
259 // Update the maximum alignment on the current section if necessary.
260 if (ByteAlignment > getCurrentSectionData()->getAlignment())
261 getCurrentSectionData()->setAlignment(ByteAlignment);
264 // Add a symbol for the file name of this module. This is the second
265 // entry in the module's symbol table (the first being the null symbol).
266 void MCELFStreamer::EmitFileDirective(StringRef Filename) {
267 MCSymbol *Symbol = getAssembler().getContext().GetOrCreateSymbol(Filename);
268 Symbol->setSection(*getCurrentSection());
269 Symbol->setAbsolute();
271 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
273 SD.setFlags(ELF_STT_File | ELF_STB_Local | ELF_STV_Default);
276 void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
277 switch (expr->getKind()) {
278 case MCExpr::Target: llvm_unreachable("Can't handle target exprs yet!");
279 case MCExpr::Constant:
282 case MCExpr::Binary: {
283 const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
284 fixSymbolsInTLSFixups(be->getLHS());
285 fixSymbolsInTLSFixups(be->getRHS());
289 case MCExpr::SymbolRef: {
290 const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
291 switch (symRef.getKind()) {
294 case MCSymbolRefExpr::VK_GOTTPOFF:
295 case MCSymbolRefExpr::VK_INDNTPOFF:
296 case MCSymbolRefExpr::VK_NTPOFF:
297 case MCSymbolRefExpr::VK_GOTNTPOFF:
298 case MCSymbolRefExpr::VK_TLSGD:
299 case MCSymbolRefExpr::VK_TLSLD:
300 case MCSymbolRefExpr::VK_TLSLDM:
301 case MCSymbolRefExpr::VK_TPOFF:
302 case MCSymbolRefExpr::VK_DTPOFF:
303 case MCSymbolRefExpr::VK_ARM_TLSGD:
304 case MCSymbolRefExpr::VK_ARM_TPOFF:
305 case MCSymbolRefExpr::VK_ARM_GOTTPOFF:
308 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(symRef.getSymbol());
309 MCELF::SetType(SD, ELF::STT_TLS);
314 fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
319 void MCELFStreamer::EmitInstToFragment(const MCInst &Inst) {
320 this->MCObjectStreamer::EmitInstToFragment(Inst);
321 MCInstFragment &F = *cast<MCInstFragment>(getCurrentFragment());
323 for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
324 fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
327 void MCELFStreamer::EmitInstToData(const MCInst &Inst) {
328 MCDataFragment *DF = getOrCreateDataFragment();
330 SmallVector<MCFixup, 4> Fixups;
331 SmallString<256> Code;
332 raw_svector_ostream VecOS(Code);
333 getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
336 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
337 fixSymbolsInTLSFixups(Fixups[i].getValue());
339 // Add the fixups and data.
340 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
341 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
342 DF->addFixup(Fixups[i]);
344 DF->getContents().append(Code.begin(), Code.end());
347 void MCELFStreamer::Finish() {
350 for (std::vector<LocalCommon>::const_iterator i = LocalCommons.begin(),
351 e = LocalCommons.end();
353 MCSymbolData *SD = i->SD;
354 uint64_t Size = i->Size;
355 unsigned ByteAlignment = i->ByteAlignment;
356 const MCSymbol &Symbol = SD->getSymbol();
357 const MCSection &Section = Symbol.getSection();
359 MCSectionData &SectData = getAssembler().getOrCreateSectionData(Section);
360 new MCAlignFragment(ByteAlignment, 0, 1, ByteAlignment, &SectData);
362 MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
365 // Update the maximum alignment of the section if necessary.
366 if (ByteAlignment > SectData.getAlignment())
367 SectData.setAlignment(ByteAlignment);
370 this->MCObjectStreamer::Finish();
373 MCStreamer *llvm::createELFStreamer(MCContext &Context, TargetAsmBackend &TAB,
374 raw_ostream &OS, MCCodeEmitter *CE,
375 bool RelaxAll, bool NoExecStack) {
376 MCELFStreamer *S = new MCELFStreamer(Context, TAB, OS, CE);
378 S->getAssembler().setRelaxAll(true);
380 S->getAssembler().setNoExecStack(true);