1 //===- SyntheticSections.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 linker-synthesized sections.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "SyntheticSections.h"
14 
15 #include "InputChunks.h"
16 #include "InputElement.h"
17 #include "OutputSegment.h"
18 #include "SymbolTable.h"
19 #include "llvm/Support/Path.h"
20 
21 using namespace llvm;
22 using namespace llvm::wasm;
23 
24 namespace lld {
25 namespace wasm {
26 
27 OutStruct out;
28 
29 namespace {
30 
31 // Some synthetic sections (e.g. "name" and "linking") have subsections.
32 // Just like the synthetic sections themselves these need to be created before
33 // they can be written out (since they are preceded by their length). This
34 // class is used to create subsections and then write them into the stream
35 // of the parent section.
36 class SubSection {
37 public:
38   explicit SubSection(uint32_t type) : type(type) {}
39 
40   void writeTo(raw_ostream &to) {
41     os.flush();
42     writeUleb128(to, type, "subsection type");
43     writeUleb128(to, body.size(), "subsection size");
44     to.write(body.data(), body.size());
45   }
46 
47 private:
48   uint32_t type;
49   std::string body;
50 
51 public:
52   raw_string_ostream os{body};
53 };
54 
55 } // namespace
56 
57 void DylinkSection::writeBody() {
58   raw_ostream &os = bodyOutputStream;
59 
60   writeUleb128(os, memSize, "MemSize");
61   writeUleb128(os, memAlign, "MemAlign");
62   writeUleb128(os, out.elemSec->numEntries(), "TableSize");
63   writeUleb128(os, 0, "TableAlign");
64   writeUleb128(os, symtab->sharedFiles.size(), "Needed");
65   for (auto *so : symtab->sharedFiles)
66     writeStr(os, llvm::sys::path::filename(so->getName()), "so name");
67 }
68 
69 uint32_t TypeSection::registerType(const WasmSignature &sig) {
70   auto pair = typeIndices.insert(std::make_pair(sig, types.size()));
71   if (pair.second) {
72     LLVM_DEBUG(llvm::dbgs() << "type " << toString(sig) << "\n");
73     types.push_back(&sig);
74   }
75   return pair.first->second;
76 }
77 
78 uint32_t TypeSection::lookupType(const WasmSignature &sig) {
79   auto it = typeIndices.find(sig);
80   if (it == typeIndices.end()) {
81     error("type not found: " + toString(sig));
82     return 0;
83   }
84   return it->second;
85 }
86 
87 void TypeSection::writeBody() {
88   writeUleb128(bodyOutputStream, types.size(), "type count");
89   for (const WasmSignature *sig : types)
90     writeSig(bodyOutputStream, *sig);
91 }
92 
93 uint32_t ImportSection::getNumImports() const {
94   assert(isSealed);
95   uint32_t numImports = importedSymbols.size() + gotSymbols.size();
96   if (config->importMemory)
97     ++numImports;
98   return numImports;
99 }
100 
101 void ImportSection::addGOTEntry(Symbol *sym) {
102   assert(!isSealed);
103   if (sym->hasGOTIndex())
104     return;
105   LLVM_DEBUG(dbgs() << "addGOTEntry: " << toString(*sym) << "\n");
106   sym->setGOTIndex(numImportedGlobals++);
107   gotSymbols.push_back(sym);
108 }
109 
110 void ImportSection::addImport(Symbol *sym) {
111   assert(!isSealed);
112   importedSymbols.emplace_back(sym);
113   if (auto *f = dyn_cast<FunctionSymbol>(sym))
114     f->setFunctionIndex(numImportedFunctions++);
115   else if (auto *g = dyn_cast<GlobalSymbol>(sym))
116     g->setGlobalIndex(numImportedGlobals++);
117   else if (auto *e = dyn_cast<EventSymbol>(sym))
118     e->setEventIndex(numImportedEvents++);
119   else
120     cast<TableSymbol>(sym)->setTableNumber(numImportedTables++);
121 }
122 
123 void ImportSection::writeBody() {
124   raw_ostream &os = bodyOutputStream;
125 
126   writeUleb128(os, getNumImports(), "import count");
127 
128   if (config->importMemory) {
129     WasmImport import;
130     import.Module = defaultModule;
131     import.Field = "memory";
132     import.Kind = WASM_EXTERNAL_MEMORY;
133     import.Memory.Flags = 0;
134     import.Memory.Initial = out.memorySec->numMemoryPages;
135     if (out.memorySec->maxMemoryPages != 0 || config->sharedMemory) {
136       import.Memory.Flags |= WASM_LIMITS_FLAG_HAS_MAX;
137       import.Memory.Maximum = out.memorySec->maxMemoryPages;
138     }
139     if (config->sharedMemory)
140       import.Memory.Flags |= WASM_LIMITS_FLAG_IS_SHARED;
141     if (config->is64.getValueOr(false))
142       import.Memory.Flags |= WASM_LIMITS_FLAG_IS_64;
143     writeImport(os, import);
144   }
145 
146   for (const Symbol *sym : importedSymbols) {
147     WasmImport import;
148     if (auto *f = dyn_cast<UndefinedFunction>(sym)) {
149       import.Field = f->importName ? *f->importName : sym->getName();
150       import.Module = f->importModule ? *f->importModule : defaultModule;
151     } else if (auto *g = dyn_cast<UndefinedGlobal>(sym)) {
152       import.Field = g->importName ? *g->importName : sym->getName();
153       import.Module = g->importModule ? *g->importModule : defaultModule;
154     } else if (auto *t = dyn_cast<UndefinedTable>(sym)) {
155       import.Field = t->importName ? *t->importName : sym->getName();
156       import.Module = t->importModule ? *t->importModule : defaultModule;
157     } else {
158       import.Field = sym->getName();
159       import.Module = defaultModule;
160     }
161 
162     if (auto *functionSym = dyn_cast<FunctionSymbol>(sym)) {
163       import.Kind = WASM_EXTERNAL_FUNCTION;
164       import.SigIndex = out.typeSec->lookupType(*functionSym->signature);
165     } else if (auto *globalSym = dyn_cast<GlobalSymbol>(sym)) {
166       import.Kind = WASM_EXTERNAL_GLOBAL;
167       import.Global = *globalSym->getGlobalType();
168     } else if (auto *eventSym = dyn_cast<EventSymbol>(sym)) {
169       import.Kind = WASM_EXTERNAL_EVENT;
170       import.Event.Attribute = eventSym->getEventType()->Attribute;
171       import.Event.SigIndex = out.typeSec->lookupType(*eventSym->signature);
172     } else {
173       auto *tableSym = cast<TableSymbol>(sym);
174       import.Kind = WASM_EXTERNAL_TABLE;
175       import.Table = *tableSym->getTableType();
176     }
177     writeImport(os, import);
178   }
179 
180   for (const Symbol *sym : gotSymbols) {
181     WasmImport import;
182     import.Kind = WASM_EXTERNAL_GLOBAL;
183     import.Global = {WASM_TYPE_I32, true};
184     if (isa<DataSymbol>(sym))
185       import.Module = "GOT.mem";
186     else
187       import.Module = "GOT.func";
188     import.Field = sym->getName();
189     writeImport(os, import);
190   }
191 }
192 
193 void FunctionSection::writeBody() {
194   raw_ostream &os = bodyOutputStream;
195 
196   writeUleb128(os, inputFunctions.size(), "function count");
197   for (const InputFunction *func : inputFunctions)
198     writeUleb128(os, out.typeSec->lookupType(func->signature), "sig index");
199 }
200 
201 void FunctionSection::addFunction(InputFunction *func) {
202   if (!func->live)
203     return;
204   uint32_t functionIndex =
205       out.importSec->getNumImportedFunctions() + inputFunctions.size();
206   inputFunctions.emplace_back(func);
207   func->setFunctionIndex(functionIndex);
208 }
209 
210 void TableSection::writeBody() {
211   raw_ostream &os = bodyOutputStream;
212 
213   writeUleb128(os, inputTables.size(), "table count");
214   for (const InputTable *table : inputTables)
215     writeTableType(os, table->getType());
216 }
217 
218 void TableSection::addTable(InputTable *table) {
219   if (!table->live)
220     return;
221   // Some inputs require that the indirect function table be assigned to table
222   // number 0.
223   if (config->legacyFunctionTable &&
224       isa<DefinedTable>(WasmSym::indirectFunctionTable) &&
225       cast<DefinedTable>(WasmSym::indirectFunctionTable)->table == table) {
226     if (out.importSec->getNumImportedTables()) {
227       // Alack!  Some other input imported a table, meaning that we are unable
228       // to assign table number 0 to the indirect function table.
229       for (const auto *culprit : out.importSec->importedSymbols) {
230         if (isa<UndefinedTable>(culprit)) {
231           error("object file not built with 'reference-types' feature "
232                 "conflicts with import of table " +
233                 culprit->getName() + "by file " + toString(culprit->getFile()));
234           return;
235         }
236       }
237       llvm_unreachable("failed to find conflicting table import");
238     }
239     inputTables.insert(inputTables.begin(), table);
240     return;
241   }
242   inputTables.push_back(table);
243 }
244 
245 void TableSection::assignIndexes() {
246   uint32_t tableNumber = out.importSec->getNumImportedTables();
247   for (InputTable *t : inputTables)
248     t->assignIndex(tableNumber++);
249 }
250 
251 void MemorySection::writeBody() {
252   raw_ostream &os = bodyOutputStream;
253 
254   bool hasMax = maxMemoryPages != 0 || config->sharedMemory;
255   writeUleb128(os, 1, "memory count");
256   unsigned flags = 0;
257   if (hasMax)
258     flags |= WASM_LIMITS_FLAG_HAS_MAX;
259   if (config->sharedMemory)
260     flags |= WASM_LIMITS_FLAG_IS_SHARED;
261   if (config->is64.getValueOr(false))
262     flags |= WASM_LIMITS_FLAG_IS_64;
263   writeUleb128(os, flags, "memory limits flags");
264   writeUleb128(os, numMemoryPages, "initial pages");
265   if (hasMax)
266     writeUleb128(os, maxMemoryPages, "max pages");
267 }
268 
269 void EventSection::writeBody() {
270   raw_ostream &os = bodyOutputStream;
271 
272   writeUleb128(os, inputEvents.size(), "event count");
273   for (InputEvent *e : inputEvents) {
274     WasmEventType type = e->getType();
275     type.SigIndex = out.typeSec->lookupType(e->signature);
276     writeEventType(os, type);
277   }
278 }
279 
280 void EventSection::addEvent(InputEvent *event) {
281   if (!event->live)
282     return;
283   uint32_t eventIndex =
284       out.importSec->getNumImportedEvents() + inputEvents.size();
285   LLVM_DEBUG(dbgs() << "addEvent: " << eventIndex << "\n");
286   event->assignIndex(eventIndex);
287   inputEvents.push_back(event);
288 }
289 
290 void GlobalSection::assignIndexes() {
291   uint32_t globalIndex = out.importSec->getNumImportedGlobals();
292   for (InputGlobal *g : inputGlobals)
293     g->assignIndex(globalIndex++);
294   for (Symbol *sym : internalGotSymbols)
295     sym->setGOTIndex(globalIndex++);
296   isSealed = true;
297 }
298 
299 void GlobalSection::addInternalGOTEntry(Symbol *sym) {
300   assert(!isSealed);
301   if (sym->requiresGOT)
302     return;
303   LLVM_DEBUG(dbgs() << "addInternalGOTEntry: " << sym->getName() << " "
304                     << toString(sym->kind()) << "\n");
305   sym->requiresGOT = true;
306   if (auto *F = dyn_cast<FunctionSymbol>(sym))
307     out.elemSec->addEntry(F);
308   internalGotSymbols.push_back(sym);
309 }
310 
311 void GlobalSection::generateRelocationCode(raw_ostream &os) const {
312   unsigned opcode_ptr_const = config->is64.getValueOr(false)
313                                   ? WASM_OPCODE_I64_CONST
314                                   : WASM_OPCODE_I32_CONST;
315   unsigned opcode_ptr_add = config->is64.getValueOr(false)
316                                 ? WASM_OPCODE_I64_ADD
317                                 : WASM_OPCODE_I32_ADD;
318 
319   for (const Symbol *sym : internalGotSymbols) {
320     if (auto *d = dyn_cast<DefinedData>(sym)) {
321       // Get __memory_base
322       writeU8(os, WASM_OPCODE_GLOBAL_GET, "GLOBAL_GET");
323       writeUleb128(os, WasmSym::memoryBase->getGlobalIndex(), "__memory_base");
324 
325       // Add the virtual address of the data symbol
326       writeU8(os, opcode_ptr_const, "CONST");
327       writeSleb128(os, d->getVirtualAddress(), "offset");
328     } else if (auto *f = dyn_cast<FunctionSymbol>(sym)) {
329       if (f->isStub)
330         continue;
331       // Get __table_base
332       writeU8(os, WASM_OPCODE_GLOBAL_GET, "GLOBAL_GET");
333       writeUleb128(os, WasmSym::tableBase->getGlobalIndex(), "__table_base");
334 
335       // Add the table index to __table_base
336       writeU8(os, opcode_ptr_const, "CONST");
337       writeSleb128(os, f->getTableIndex(), "offset");
338     } else {
339       assert(isa<UndefinedData>(sym));
340       continue;
341     }
342     writeU8(os, opcode_ptr_add, "ADD");
343     writeU8(os, WASM_OPCODE_GLOBAL_SET, "GLOBAL_SET");
344     writeUleb128(os, sym->getGOTIndex(), "got_entry");
345   }
346 }
347 
348 void GlobalSection::writeBody() {
349   raw_ostream &os = bodyOutputStream;
350 
351   writeUleb128(os, numGlobals(), "global count");
352   for (InputGlobal *g : inputGlobals) {
353     writeGlobalType(os, g->getType());
354     writeInitExpr(os, g->getInitExpr());
355   }
356   // TODO(wvo): when do these need I64_CONST?
357   for (const Symbol *sym : internalGotSymbols) {
358     // In the case of dynamic linking, internal GOT entries
359     // need to be mutable since they get updated to the correct
360     // runtime value during `__wasm_apply_global_relocs`.
361     bool mutable_ = config->isPic & !sym->isStub;
362     WasmGlobalType type{WASM_TYPE_I32, mutable_};
363     WasmInitExpr initExpr;
364     initExpr.Opcode = WASM_OPCODE_I32_CONST;
365     if (auto *d = dyn_cast<DefinedData>(sym))
366       initExpr.Value.Int32 = d->getVirtualAddress();
367     else if (auto *f = dyn_cast<FunctionSymbol>(sym))
368       initExpr.Value.Int32 = f->isStub ? 0 : f->getTableIndex();
369     else {
370       assert(isa<UndefinedData>(sym));
371       initExpr.Value.Int32 = 0;
372     }
373     writeGlobalType(os, type);
374     writeInitExpr(os, initExpr);
375   }
376   for (const DefinedData *sym : dataAddressGlobals) {
377     WasmGlobalType type{WASM_TYPE_I32, false};
378     WasmInitExpr initExpr;
379     initExpr.Opcode = WASM_OPCODE_I32_CONST;
380     initExpr.Value.Int32 = sym->getVirtualAddress();
381     writeGlobalType(os, type);
382     writeInitExpr(os, initExpr);
383   }
384 }
385 
386 void GlobalSection::addGlobal(InputGlobal *global) {
387   assert(!isSealed);
388   if (!global->live)
389     return;
390   inputGlobals.push_back(global);
391 }
392 
393 void ExportSection::writeBody() {
394   raw_ostream &os = bodyOutputStream;
395 
396   writeUleb128(os, exports.size(), "export count");
397   for (const WasmExport &export_ : exports)
398     writeExport(os, export_);
399 }
400 
401 bool StartSection::isNeeded() const {
402   return WasmSym::startFunction != nullptr;
403 }
404 
405 void StartSection::writeBody() {
406   raw_ostream &os = bodyOutputStream;
407   writeUleb128(os, WasmSym::startFunction->getFunctionIndex(),
408                "function index");
409 }
410 
411 void ElemSection::addEntry(FunctionSymbol *sym) {
412   // Don't add stub functions to the wasm table.  The address of all stub
413   // functions should be zero and they should they don't appear in the table.
414   // They only exist so that the calls to missing functions can validate.
415   if (sym->hasTableIndex() || sym->isStub)
416     return;
417   sym->setTableIndex(config->tableBase + indirectFunctions.size());
418   indirectFunctions.emplace_back(sym);
419 }
420 
421 void ElemSection::writeBody() {
422   raw_ostream &os = bodyOutputStream;
423 
424   writeUleb128(os, 1, "segment count");
425   writeUleb128(os, 0, "table index");
426   WasmInitExpr initExpr;
427   if (config->isPic) {
428     initExpr.Opcode = WASM_OPCODE_GLOBAL_GET;
429     initExpr.Value.Global = WasmSym::tableBase->getGlobalIndex();
430   } else {
431     initExpr.Opcode = WASM_OPCODE_I32_CONST;
432     initExpr.Value.Int32 = config->tableBase;
433   }
434   writeInitExpr(os, initExpr);
435   writeUleb128(os, indirectFunctions.size(), "elem count");
436 
437   uint32_t tableIndex = config->tableBase;
438   for (const FunctionSymbol *sym : indirectFunctions) {
439     assert(sym->getTableIndex() == tableIndex);
440     writeUleb128(os, sym->getFunctionIndex(), "function index");
441     ++tableIndex;
442   }
443 }
444 
445 DataCountSection::DataCountSection(ArrayRef<OutputSegment *> segments)
446     : SyntheticSection(llvm::wasm::WASM_SEC_DATACOUNT),
447       numSegments(std::count_if(
448           segments.begin(), segments.end(),
449           [](OutputSegment *const segment) { return !segment->isBss; })) {}
450 
451 void DataCountSection::writeBody() {
452   writeUleb128(bodyOutputStream, numSegments, "data count");
453 }
454 
455 bool DataCountSection::isNeeded() const {
456   return numSegments && config->sharedMemory;
457 }
458 
459 void LinkingSection::writeBody() {
460   raw_ostream &os = bodyOutputStream;
461 
462   writeUleb128(os, WasmMetadataVersion, "Version");
463 
464   if (!symtabEntries.empty()) {
465     SubSection sub(WASM_SYMBOL_TABLE);
466     writeUleb128(sub.os, symtabEntries.size(), "num symbols");
467 
468     for (const Symbol *sym : symtabEntries) {
469       assert(sym->isDefined() || sym->isUndefined());
470       WasmSymbolType kind = sym->getWasmType();
471       uint32_t flags = sym->flags;
472 
473       writeU8(sub.os, kind, "sym kind");
474       writeUleb128(sub.os, flags, "sym flags");
475 
476       if (auto *f = dyn_cast<FunctionSymbol>(sym)) {
477         writeUleb128(sub.os, f->getFunctionIndex(), "index");
478         if (sym->isDefined() || (flags & WASM_SYMBOL_EXPLICIT_NAME) != 0)
479           writeStr(sub.os, sym->getName(), "sym name");
480       } else if (auto *g = dyn_cast<GlobalSymbol>(sym)) {
481         writeUleb128(sub.os, g->getGlobalIndex(), "index");
482         if (sym->isDefined() || (flags & WASM_SYMBOL_EXPLICIT_NAME) != 0)
483           writeStr(sub.os, sym->getName(), "sym name");
484       } else if (auto *e = dyn_cast<EventSymbol>(sym)) {
485         writeUleb128(sub.os, e->getEventIndex(), "index");
486         if (sym->isDefined() || (flags & WASM_SYMBOL_EXPLICIT_NAME) != 0)
487           writeStr(sub.os, sym->getName(), "sym name");
488       } else if (auto *t = dyn_cast<TableSymbol>(sym)) {
489         writeUleb128(sub.os, t->getTableNumber(), "table number");
490         if (sym->isDefined() || (flags & WASM_SYMBOL_EXPLICIT_NAME) != 0)
491           writeStr(sub.os, sym->getName(), "sym name");
492       } else if (isa<DataSymbol>(sym)) {
493         writeStr(sub.os, sym->getName(), "sym name");
494         if (auto *dataSym = dyn_cast<DefinedData>(sym)) {
495           writeUleb128(sub.os, dataSym->getOutputSegmentIndex(), "index");
496           writeUleb128(sub.os, dataSym->getOutputSegmentOffset(),
497                        "data offset");
498           writeUleb128(sub.os, dataSym->getSize(), "data size");
499         }
500       } else {
501         auto *s = cast<OutputSectionSymbol>(sym);
502         writeUleb128(sub.os, s->section->sectionIndex, "sym section index");
503       }
504     }
505 
506     sub.writeTo(os);
507   }
508 
509   if (dataSegments.size()) {
510     SubSection sub(WASM_SEGMENT_INFO);
511     writeUleb128(sub.os, dataSegments.size(), "num data segments");
512     for (const OutputSegment *s : dataSegments) {
513       writeStr(sub.os, s->name, "segment name");
514       writeUleb128(sub.os, s->alignment, "alignment");
515       writeUleb128(sub.os, 0, "flags");
516     }
517     sub.writeTo(os);
518   }
519 
520   if (!initFunctions.empty()) {
521     SubSection sub(WASM_INIT_FUNCS);
522     writeUleb128(sub.os, initFunctions.size(), "num init functions");
523     for (const WasmInitEntry &f : initFunctions) {
524       writeUleb128(sub.os, f.priority, "priority");
525       writeUleb128(sub.os, f.sym->getOutputSymbolIndex(), "function index");
526     }
527     sub.writeTo(os);
528   }
529 
530   struct ComdatEntry {
531     unsigned kind;
532     uint32_t index;
533   };
534   std::map<StringRef, std::vector<ComdatEntry>> comdats;
535 
536   for (const InputFunction *f : out.functionSec->inputFunctions) {
537     StringRef comdat = f->getComdatName();
538     if (!comdat.empty())
539       comdats[comdat].emplace_back(
540           ComdatEntry{WASM_COMDAT_FUNCTION, f->getFunctionIndex()});
541   }
542   for (uint32_t i = 0; i < dataSegments.size(); ++i) {
543     const auto &inputSegments = dataSegments[i]->inputSegments;
544     if (inputSegments.empty())
545       continue;
546     StringRef comdat = inputSegments[0]->getComdatName();
547 #ifndef NDEBUG
548     for (const InputSegment *isec : inputSegments)
549       assert(isec->getComdatName() == comdat);
550 #endif
551     if (!comdat.empty())
552       comdats[comdat].emplace_back(ComdatEntry{WASM_COMDAT_DATA, i});
553   }
554 
555   if (!comdats.empty()) {
556     SubSection sub(WASM_COMDAT_INFO);
557     writeUleb128(sub.os, comdats.size(), "num comdats");
558     for (const auto &c : comdats) {
559       writeStr(sub.os, c.first, "comdat name");
560       writeUleb128(sub.os, 0, "comdat flags"); // flags for future use
561       writeUleb128(sub.os, c.second.size(), "num entries");
562       for (const ComdatEntry &entry : c.second) {
563         writeU8(sub.os, entry.kind, "entry kind");
564         writeUleb128(sub.os, entry.index, "entry index");
565       }
566     }
567     sub.writeTo(os);
568   }
569 }
570 
571 void LinkingSection::addToSymtab(Symbol *sym) {
572   sym->setOutputSymbolIndex(symtabEntries.size());
573   symtabEntries.emplace_back(sym);
574 }
575 
576 unsigned NameSection::numNamedFunctions() const {
577   unsigned numNames = out.importSec->getNumImportedFunctions();
578 
579   for (const InputFunction *f : out.functionSec->inputFunctions)
580     if (!f->getName().empty() || !f->getDebugName().empty())
581       ++numNames;
582 
583   return numNames;
584 }
585 
586 unsigned NameSection::numNamedGlobals() const {
587   unsigned numNames = out.importSec->getNumImportedGlobals();
588 
589   for (const InputGlobal *g : out.globalSec->inputGlobals)
590     if (!g->getName().empty())
591       ++numNames;
592 
593   numNames += out.globalSec->internalGotSymbols.size();
594   return numNames;
595 }
596 
597 unsigned NameSection::numNamedDataSegments() const {
598   unsigned numNames = 0;
599 
600   for (const OutputSegment *s : segments)
601     if (!s->name.empty() && !s->isBss)
602       ++numNames;
603 
604   return numNames;
605 }
606 
607 // Create the custom "name" section containing debug symbol names.
608 void NameSection::writeBody() {
609   unsigned count = numNamedFunctions();
610   if (count) {
611     SubSection sub(WASM_NAMES_FUNCTION);
612     writeUleb128(sub.os, count, "name count");
613 
614     // Function names appear in function index order.  As it happens
615     // importedSymbols and inputFunctions are numbered in order with imported
616     // functions coming first.
617     for (const Symbol *s : out.importSec->importedSymbols) {
618       if (auto *f = dyn_cast<FunctionSymbol>(s)) {
619         writeUleb128(sub.os, f->getFunctionIndex(), "func index");
620         writeStr(sub.os, toString(*s), "symbol name");
621       }
622     }
623     for (const InputFunction *f : out.functionSec->inputFunctions) {
624       if (!f->getName().empty()) {
625         writeUleb128(sub.os, f->getFunctionIndex(), "func index");
626         if (!f->getDebugName().empty()) {
627           writeStr(sub.os, f->getDebugName(), "symbol name");
628         } else {
629           writeStr(sub.os, maybeDemangleSymbol(f->getName()), "symbol name");
630         }
631       }
632     }
633     sub.writeTo(bodyOutputStream);
634   }
635 
636   count = numNamedGlobals();
637   if (count) {
638     SubSection sub(WASM_NAMES_GLOBAL);
639     writeUleb128(sub.os, count, "name count");
640 
641     for (const Symbol *s : out.importSec->importedSymbols) {
642       if (auto *g = dyn_cast<GlobalSymbol>(s)) {
643         writeUleb128(sub.os, g->getGlobalIndex(), "global index");
644         writeStr(sub.os, toString(*s), "symbol name");
645       }
646     }
647     for (const Symbol *s : out.importSec->gotSymbols) {
648       writeUleb128(sub.os, s->getGOTIndex(), "global index");
649       writeStr(sub.os, toString(*s), "symbol name");
650     }
651     for (const InputGlobal *g : out.globalSec->inputGlobals) {
652       if (!g->getName().empty()) {
653         writeUleb128(sub.os, g->getAssignedIndex(), "global index");
654         writeStr(sub.os, maybeDemangleSymbol(g->getName()), "symbol name");
655       }
656     }
657     for (Symbol *s : out.globalSec->internalGotSymbols) {
658       writeUleb128(sub.os, s->getGOTIndex(), "global index");
659       if (isa<FunctionSymbol>(s))
660         writeStr(sub.os, "GOT.func.internal." + toString(*s), "symbol name");
661       else
662         writeStr(sub.os, "GOT.data.internal." + toString(*s), "symbol name");
663     }
664 
665     sub.writeTo(bodyOutputStream);
666   }
667 
668   count = numNamedDataSegments();
669   if (count) {
670     SubSection sub(WASM_NAMES_DATA_SEGMENT);
671     writeUleb128(sub.os, count, "name count");
672 
673     for (OutputSegment *s : segments) {
674       if (!s->name.empty() && !s->isBss) {
675         writeUleb128(sub.os, s->index, "global index");
676         writeStr(sub.os, s->name, "segment name");
677       }
678     }
679 
680     sub.writeTo(bodyOutputStream);
681   }
682 }
683 
684 void ProducersSection::addInfo(const WasmProducerInfo &info) {
685   for (auto &producers :
686        {std::make_pair(&info.Languages, &languages),
687         std::make_pair(&info.Tools, &tools), std::make_pair(&info.SDKs, &sDKs)})
688     for (auto &producer : *producers.first)
689       if (producers.second->end() ==
690           llvm::find_if(*producers.second,
691                         [&](std::pair<std::string, std::string> seen) {
692                           return seen.first == producer.first;
693                         }))
694         producers.second->push_back(producer);
695 }
696 
697 void ProducersSection::writeBody() {
698   auto &os = bodyOutputStream;
699   writeUleb128(os, fieldCount(), "field count");
700   for (auto &field :
701        {std::make_pair("language", languages),
702         std::make_pair("processed-by", tools), std::make_pair("sdk", sDKs)}) {
703     if (field.second.empty())
704       continue;
705     writeStr(os, field.first, "field name");
706     writeUleb128(os, field.second.size(), "number of entries");
707     for (auto &entry : field.second) {
708       writeStr(os, entry.first, "producer name");
709       writeStr(os, entry.second, "producer version");
710     }
711   }
712 }
713 
714 void TargetFeaturesSection::writeBody() {
715   SmallVector<std::string, 8> emitted(features.begin(), features.end());
716   llvm::sort(emitted);
717   auto &os = bodyOutputStream;
718   writeUleb128(os, emitted.size(), "feature count");
719   for (auto &feature : emitted) {
720     writeU8(os, WASM_FEATURE_PREFIX_USED, "feature used prefix");
721     writeStr(os, feature, "feature name");
722   }
723 }
724 
725 void RelocSection::writeBody() {
726   uint32_t count = sec->getNumRelocations();
727   assert(sec->sectionIndex != UINT32_MAX);
728   writeUleb128(bodyOutputStream, sec->sectionIndex, "reloc section");
729   writeUleb128(bodyOutputStream, count, "reloc count");
730   sec->writeRelocations(bodyOutputStream);
731 }
732 
733 } // namespace wasm
734 } // namespace lld
735