//===- SyntheticSections.cpp ----------------------------------------------===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // This file contains linker-synthesized sections. // //===----------------------------------------------------------------------===// #include "SyntheticSections.h" #include "InputChunks.h" #include "InputEvent.h" #include "InputGlobal.h" #include "OutputSegment.h" #include "SymbolTable.h" #include "llvm/Support/Path.h" using namespace llvm; using namespace llvm::wasm; namespace lld { namespace wasm { OutStruct out; namespace { // Some synthetic sections (e.g. "name" and "linking") have subsections. // Just like the synthetic sections themselves these need to be created before // they can be written out (since they are preceded by their length). This // class is used to create subsections and then write them into the stream // of the parent section. class SubSection { public: explicit SubSection(uint32_t type) : type(type) {} void writeTo(raw_ostream &to) { os.flush(); writeUleb128(to, type, "subsection type"); writeUleb128(to, body.size(), "subsection size"); to.write(body.data(), body.size()); } private: uint32_t type; std::string body; public: raw_string_ostream os{body}; }; } // namespace void DylinkSection::writeBody() { raw_ostream &os = bodyOutputStream; writeUleb128(os, memSize, "MemSize"); writeUleb128(os, memAlign, "MemAlign"); writeUleb128(os, out.elemSec->numEntries(), "TableSize"); writeUleb128(os, 0, "TableAlign"); writeUleb128(os, symtab->sharedFiles.size(), "Needed"); for (auto *so : symtab->sharedFiles) writeStr(os, llvm::sys::path::filename(so->getName()), "so name"); } uint32_t TypeSection::registerType(const WasmSignature &sig) { auto pair = typeIndices.insert(std::make_pair(sig, types.size())); if (pair.second) { LLVM_DEBUG(llvm::dbgs() << "type " << toString(sig) << "\n"); types.push_back(&sig); } return pair.first->second; } uint32_t TypeSection::lookupType(const WasmSignature &sig) { auto it = typeIndices.find(sig); if (it == typeIndices.end()) { error("type not found: " + toString(sig)); return 0; } return it->second; } void TypeSection::writeBody() { writeUleb128(bodyOutputStream, types.size(), "type count"); for (const WasmSignature *sig : types) writeSig(bodyOutputStream, *sig); } uint32_t ImportSection::getNumImports() const { assert(isSealed); uint32_t numImports = importedSymbols.size() + gotSymbols.size(); if (config->importMemory) ++numImports; if (config->importTable) ++numImports; return numImports; } void ImportSection::addGOTEntry(Symbol *sym) { assert(!isSealed); if (sym->hasGOTIndex()) return; LLVM_DEBUG(dbgs() << "addGOTEntry: " << toString(*sym) << "\n"); sym->setGOTIndex(numImportedGlobals++); gotSymbols.push_back(sym); } void ImportSection::addImport(Symbol *sym) { assert(!isSealed); importedSymbols.emplace_back(sym); if (auto *f = dyn_cast(sym)) f->setFunctionIndex(numImportedFunctions++); else if (auto *g = dyn_cast(sym)) g->setGlobalIndex(numImportedGlobals++); else cast(sym)->setEventIndex(numImportedEvents++); } void ImportSection::writeBody() { raw_ostream &os = bodyOutputStream; writeUleb128(os, getNumImports(), "import count"); if (config->importMemory) { WasmImport import; import.Module = defaultModule; import.Field = "memory"; import.Kind = WASM_EXTERNAL_MEMORY; import.Memory.Flags = 0; import.Memory.Initial = out.memorySec->numMemoryPages; if (out.memorySec->maxMemoryPages != 0 || config->sharedMemory) { import.Memory.Flags |= WASM_LIMITS_FLAG_HAS_MAX; import.Memory.Maximum = out.memorySec->maxMemoryPages; } if (config->sharedMemory) import.Memory.Flags |= WASM_LIMITS_FLAG_IS_SHARED; if (config->is64.getValueOr(false)) import.Memory.Flags |= WASM_LIMITS_FLAG_IS_64; writeImport(os, import); } if (config->importTable) { uint32_t tableSize = config->tableBase + out.elemSec->numEntries(); WasmImport import; import.Module = defaultModule; import.Field = functionTableName; import.Kind = WASM_EXTERNAL_TABLE; import.Table.ElemType = WASM_TYPE_FUNCREF; import.Table.Limits = {0, tableSize, 0}; writeImport(os, import); } for (const Symbol *sym : importedSymbols) { WasmImport import; if (auto *f = dyn_cast(sym)) { import.Field = f->importName ? *f->importName : sym->getName(); import.Module = f->importModule ? *f->importModule : defaultModule; } else if (auto *g = dyn_cast(sym)) { import.Field = g->importName ? *g->importName : sym->getName(); import.Module = g->importModule ? *g->importModule : defaultModule; } else { import.Field = sym->getName(); import.Module = defaultModule; } if (auto *functionSym = dyn_cast(sym)) { import.Kind = WASM_EXTERNAL_FUNCTION; import.SigIndex = out.typeSec->lookupType(*functionSym->signature); } else if (auto *globalSym = dyn_cast(sym)) { import.Kind = WASM_EXTERNAL_GLOBAL; import.Global = *globalSym->getGlobalType(); } else { auto *eventSym = cast(sym); import.Kind = WASM_EXTERNAL_EVENT; import.Event.Attribute = eventSym->getEventType()->Attribute; import.Event.SigIndex = out.typeSec->lookupType(*eventSym->signature); } writeImport(os, import); } for (const Symbol *sym : gotSymbols) { WasmImport import; import.Kind = WASM_EXTERNAL_GLOBAL; import.Global = {WASM_TYPE_I32, true}; if (isa(sym)) import.Module = "GOT.mem"; else import.Module = "GOT.func"; import.Field = sym->getName(); writeImport(os, import); } } void FunctionSection::writeBody() { raw_ostream &os = bodyOutputStream; writeUleb128(os, inputFunctions.size(), "function count"); for (const InputFunction *func : inputFunctions) writeUleb128(os, out.typeSec->lookupType(func->signature), "sig index"); } void FunctionSection::addFunction(InputFunction *func) { if (!func->live) return; uint32_t functionIndex = out.importSec->getNumImportedFunctions() + inputFunctions.size(); inputFunctions.emplace_back(func); func->setFunctionIndex(functionIndex); } void TableSection::writeBody() { uint32_t tableSize = config->tableBase + out.elemSec->numEntries(); raw_ostream &os = bodyOutputStream; writeUleb128(os, 1, "table count"); WasmLimits limits; if (config->growableTable) limits = {0, tableSize, 0}; else limits = {WASM_LIMITS_FLAG_HAS_MAX, tableSize, tableSize}; writeTableType(os, WasmTableType{WASM_TYPE_FUNCREF, limits}); } void MemorySection::writeBody() { raw_ostream &os = bodyOutputStream; bool hasMax = maxMemoryPages != 0 || config->sharedMemory; writeUleb128(os, 1, "memory count"); unsigned flags = 0; if (hasMax) flags |= WASM_LIMITS_FLAG_HAS_MAX; if (config->sharedMemory) flags |= WASM_LIMITS_FLAG_IS_SHARED; if (config->is64.getValueOr(false)) flags |= WASM_LIMITS_FLAG_IS_64; writeUleb128(os, flags, "memory limits flags"); writeUleb128(os, numMemoryPages, "initial pages"); if (hasMax) writeUleb128(os, maxMemoryPages, "max pages"); } void EventSection::writeBody() { raw_ostream &os = bodyOutputStream; writeUleb128(os, inputEvents.size(), "event count"); for (InputEvent *e : inputEvents) { e->event.Type.SigIndex = out.typeSec->lookupType(e->signature); writeEvent(os, e->event); } } void EventSection::addEvent(InputEvent *event) { if (!event->live) return; uint32_t eventIndex = out.importSec->getNumImportedEvents() + inputEvents.size(); LLVM_DEBUG(dbgs() << "addEvent: " << eventIndex << "\n"); event->setEventIndex(eventIndex); inputEvents.push_back(event); } void GlobalSection::assignIndexes() { uint32_t globalIndex = out.importSec->getNumImportedGlobals(); for (InputGlobal *g : inputGlobals) g->setGlobalIndex(globalIndex++); for (Symbol *sym : internalGotSymbols) sym->setGOTIndex(globalIndex++); isSealed = true; } void GlobalSection::addInternalGOTEntry(Symbol *sym) { assert(!isSealed); if (sym->requiresGOT) return; LLVM_DEBUG(dbgs() << "addInternalGOTEntry: " << sym->getName() << " " << toString(sym->kind()) << "\n"); sym->requiresGOT = true; if (auto *F = dyn_cast(sym)) out.elemSec->addEntry(F); internalGotSymbols.push_back(sym); } void GlobalSection::generateRelocationCode(raw_ostream &os) const { unsigned opcode_ptr_const = config->is64.getValueOr(false) ? WASM_OPCODE_I64_CONST : WASM_OPCODE_I32_CONST; unsigned opcode_ptr_add = config->is64.getValueOr(false) ? WASM_OPCODE_I64_ADD : WASM_OPCODE_I32_ADD; for (const Symbol *sym : internalGotSymbols) { if (auto *d = dyn_cast(sym)) { // Get __memory_base writeU8(os, WASM_OPCODE_GLOBAL_GET, "GLOBAL_GET"); writeUleb128(os, WasmSym::memoryBase->getGlobalIndex(), "__memory_base"); // Add the virtual address of the data symbol writeU8(os, opcode_ptr_const, "CONST"); writeSleb128(os, d->getVirtualAddress(), "offset"); } else if (auto *f = dyn_cast(sym)) { if (f->isStub) continue; // Get __table_base writeU8(os, WASM_OPCODE_GLOBAL_GET, "GLOBAL_GET"); writeUleb128(os, WasmSym::tableBase->getGlobalIndex(), "__table_base"); // Add the table index to __table_base writeU8(os, opcode_ptr_const, "CONST"); writeSleb128(os, f->getTableIndex(), "offset"); } else { assert(isa(sym)); continue; } writeU8(os, opcode_ptr_add, "ADD"); writeU8(os, WASM_OPCODE_GLOBAL_SET, "GLOBAL_SET"); writeUleb128(os, sym->getGOTIndex(), "got_entry"); } } void GlobalSection::writeBody() { raw_ostream &os = bodyOutputStream; writeUleb128(os, numGlobals(), "global count"); for (InputGlobal *g : inputGlobals) writeGlobal(os, g->global); // TODO(wvo): when do these need I64_CONST? for (const Symbol *sym : internalGotSymbols) { WasmGlobal global; // In the case of dynamic linking, internal GOT entries // need to be mutable since they get updated to the correct // runtime value during `__wasm_apply_relocs`. bool mutable_ = config->isPic & !sym->isStub; global.Type = {WASM_TYPE_I32, mutable_}; global.InitExpr.Opcode = WASM_OPCODE_I32_CONST; if (auto *d = dyn_cast(sym)) global.InitExpr.Value.Int32 = d->getVirtualAddress(); else if (auto *f = dyn_cast(sym)) global.InitExpr.Value.Int32 = f->isStub ? 0 : f->getTableIndex(); else { assert(isa(sym)); global.InitExpr.Value.Int32 = 0; } writeGlobal(os, global); } for (const DefinedData *sym : dataAddressGlobals) { WasmGlobal global; global.Type = {WASM_TYPE_I32, false}; global.InitExpr.Opcode = WASM_OPCODE_I32_CONST; global.InitExpr.Value.Int32 = sym->getVirtualAddress(); writeGlobal(os, global); } } void GlobalSection::addGlobal(InputGlobal *global) { assert(!isSealed); if (!global->live) return; inputGlobals.push_back(global); } void ExportSection::writeBody() { raw_ostream &os = bodyOutputStream; writeUleb128(os, exports.size(), "export count"); for (const WasmExport &export_ : exports) writeExport(os, export_); } bool StartSection::isNeeded() const { return WasmSym::initMemory != nullptr; } void StartSection::writeBody() { raw_ostream &os = bodyOutputStream; writeUleb128(os, WasmSym::initMemory->getFunctionIndex(), "function index"); } void ElemSection::addEntry(FunctionSymbol *sym) { // Don't add stub functions to the wasm table. The address of all stub // functions should be zero and they should they don't appear in the table. // They only exist so that the calls to missing functions can validate. if (sym->hasTableIndex() || sym->isStub) return; sym->setTableIndex(config->tableBase + indirectFunctions.size()); indirectFunctions.emplace_back(sym); } void ElemSection::writeBody() { raw_ostream &os = bodyOutputStream; writeUleb128(os, 1, "segment count"); writeUleb128(os, 0, "table index"); WasmInitExpr initExpr; if (config->isPic) { initExpr.Opcode = WASM_OPCODE_GLOBAL_GET; initExpr.Value.Global = WasmSym::tableBase->getGlobalIndex(); } else { initExpr.Opcode = WASM_OPCODE_I32_CONST; initExpr.Value.Int32 = config->tableBase; } writeInitExpr(os, initExpr); writeUleb128(os, indirectFunctions.size(), "elem count"); uint32_t tableIndex = config->tableBase; for (const FunctionSymbol *sym : indirectFunctions) { assert(sym->getTableIndex() == tableIndex); writeUleb128(os, sym->getFunctionIndex(), "function index"); ++tableIndex; } } DataCountSection::DataCountSection(ArrayRef segments) : SyntheticSection(llvm::wasm::WASM_SEC_DATACOUNT), numSegments(std::count_if( segments.begin(), segments.end(), [](OutputSegment *const segment) { return !segment->isBss; })) {} void DataCountSection::writeBody() { writeUleb128(bodyOutputStream, numSegments, "data count"); } bool DataCountSection::isNeeded() const { return numSegments && config->sharedMemory; } void LinkingSection::writeBody() { raw_ostream &os = bodyOutputStream; writeUleb128(os, WasmMetadataVersion, "Version"); if (!symtabEntries.empty()) { SubSection sub(WASM_SYMBOL_TABLE); writeUleb128(sub.os, symtabEntries.size(), "num symbols"); for (const Symbol *sym : symtabEntries) { assert(sym->isDefined() || sym->isUndefined()); WasmSymbolType kind = sym->getWasmType(); uint32_t flags = sym->flags; writeU8(sub.os, kind, "sym kind"); writeUleb128(sub.os, flags, "sym flags"); if (auto *f = dyn_cast(sym)) { writeUleb128(sub.os, f->getFunctionIndex(), "index"); if (sym->isDefined() || (flags & WASM_SYMBOL_EXPLICIT_NAME) != 0) writeStr(sub.os, sym->getName(), "sym name"); } else if (auto *g = dyn_cast(sym)) { writeUleb128(sub.os, g->getGlobalIndex(), "index"); if (sym->isDefined() || (flags & WASM_SYMBOL_EXPLICIT_NAME) != 0) writeStr(sub.os, sym->getName(), "sym name"); } else if (auto *e = dyn_cast(sym)) { writeUleb128(sub.os, e->getEventIndex(), "index"); if (sym->isDefined() || (flags & WASM_SYMBOL_EXPLICIT_NAME) != 0) writeStr(sub.os, sym->getName(), "sym name"); } else if (isa(sym)) { writeStr(sub.os, sym->getName(), "sym name"); if (auto *dataSym = dyn_cast(sym)) { writeUleb128(sub.os, dataSym->getOutputSegmentIndex(), "index"); writeUleb128(sub.os, dataSym->getOutputSegmentOffset(), "data offset"); writeUleb128(sub.os, dataSym->getSize(), "data size"); } } else { auto *s = cast(sym); writeUleb128(sub.os, s->section->sectionIndex, "sym section index"); } } sub.writeTo(os); } if (dataSegments.size()) { SubSection sub(WASM_SEGMENT_INFO); writeUleb128(sub.os, dataSegments.size(), "num data segments"); for (const OutputSegment *s : dataSegments) { writeStr(sub.os, s->name, "segment name"); writeUleb128(sub.os, s->alignment, "alignment"); writeUleb128(sub.os, 0, "flags"); } sub.writeTo(os); } if (!initFunctions.empty()) { SubSection sub(WASM_INIT_FUNCS); writeUleb128(sub.os, initFunctions.size(), "num init functions"); for (const WasmInitEntry &f : initFunctions) { writeUleb128(sub.os, f.priority, "priority"); writeUleb128(sub.os, f.sym->getOutputSymbolIndex(), "function index"); } sub.writeTo(os); } struct ComdatEntry { unsigned kind; uint32_t index; }; std::map> comdats; for (const InputFunction *f : out.functionSec->inputFunctions) { StringRef comdat = f->getComdatName(); if (!comdat.empty()) comdats[comdat].emplace_back( ComdatEntry{WASM_COMDAT_FUNCTION, f->getFunctionIndex()}); } for (uint32_t i = 0; i < dataSegments.size(); ++i) { const auto &inputSegments = dataSegments[i]->inputSegments; if (inputSegments.empty()) continue; StringRef comdat = inputSegments[0]->getComdatName(); #ifndef NDEBUG for (const InputSegment *isec : inputSegments) assert(isec->getComdatName() == comdat); #endif if (!comdat.empty()) comdats[comdat].emplace_back(ComdatEntry{WASM_COMDAT_DATA, i}); } if (!comdats.empty()) { SubSection sub(WASM_COMDAT_INFO); writeUleb128(sub.os, comdats.size(), "num comdats"); for (const auto &c : comdats) { writeStr(sub.os, c.first, "comdat name"); writeUleb128(sub.os, 0, "comdat flags"); // flags for future use writeUleb128(sub.os, c.second.size(), "num entries"); for (const ComdatEntry &entry : c.second) { writeU8(sub.os, entry.kind, "entry kind"); writeUleb128(sub.os, entry.index, "entry index"); } } sub.writeTo(os); } } void LinkingSection::addToSymtab(Symbol *sym) { sym->setOutputSymbolIndex(symtabEntries.size()); symtabEntries.emplace_back(sym); } unsigned NameSection::numNamedFunctions() const { unsigned numNames = out.importSec->getNumImportedFunctions(); for (const InputFunction *f : out.functionSec->inputFunctions) if (!f->getName().empty() || !f->getDebugName().empty()) ++numNames; return numNames; } unsigned NameSection::numNamedGlobals() const { unsigned numNames = out.importSec->getNumImportedGlobals(); for (const InputGlobal *g : out.globalSec->inputGlobals) if (!g->getName().empty()) ++numNames; numNames += out.globalSec->internalGotSymbols.size(); return numNames; } // Create the custom "name" section containing debug symbol names. void NameSection::writeBody() { unsigned count = numNamedFunctions(); if (count) { SubSection sub(WASM_NAMES_FUNCTION); writeUleb128(sub.os, count, "name count"); // Function names appear in function index order. As it happens // importedSymbols and inputFunctions are numbered in order with imported // functions coming first. for (const Symbol *s : out.importSec->importedSymbols) { if (auto *f = dyn_cast(s)) { writeUleb128(sub.os, f->getFunctionIndex(), "func index"); writeStr(sub.os, toString(*s), "symbol name"); } } for (const InputFunction *f : out.functionSec->inputFunctions) { if (!f->getName().empty()) { writeUleb128(sub.os, f->getFunctionIndex(), "func index"); if (!f->getDebugName().empty()) { writeStr(sub.os, f->getDebugName(), "symbol name"); } else { writeStr(sub.os, maybeDemangleSymbol(f->getName()), "symbol name"); } } } sub.writeTo(bodyOutputStream); } count = numNamedGlobals(); if (count) { SubSection sub(WASM_NAMES_GLOBAL); writeUleb128(sub.os, count, "name count"); for (const Symbol *s : out.importSec->importedSymbols) { if (auto *g = dyn_cast(s)) { writeUleb128(sub.os, g->getGlobalIndex(), "global index"); writeStr(sub.os, toString(*s), "symbol name"); } } for (const Symbol *s : out.importSec->gotSymbols) { writeUleb128(sub.os, s->getGOTIndex(), "global index"); writeStr(sub.os, toString(*s), "symbol name"); } for (const InputGlobal *g : out.globalSec->inputGlobals) { if (!g->getName().empty()) { writeUleb128(sub.os, g->getGlobalIndex(), "global index"); writeStr(sub.os, maybeDemangleSymbol(g->getName()), "symbol name"); } } for (Symbol *s : out.globalSec->internalGotSymbols) { writeUleb128(sub.os, s->getGOTIndex(), "global index"); writeStr(sub.os, toString(*s), "symbol name"); } sub.writeTo(bodyOutputStream); } } void ProducersSection::addInfo(const WasmProducerInfo &info) { for (auto &producers : {std::make_pair(&info.Languages, &languages), std::make_pair(&info.Tools, &tools), std::make_pair(&info.SDKs, &sDKs)}) for (auto &producer : *producers.first) if (producers.second->end() == llvm::find_if(*producers.second, [&](std::pair seen) { return seen.first == producer.first; })) producers.second->push_back(producer); } void ProducersSection::writeBody() { auto &os = bodyOutputStream; writeUleb128(os, fieldCount(), "field count"); for (auto &field : {std::make_pair("language", languages), std::make_pair("processed-by", tools), std::make_pair("sdk", sDKs)}) { if (field.second.empty()) continue; writeStr(os, field.first, "field name"); writeUleb128(os, field.second.size(), "number of entries"); for (auto &entry : field.second) { writeStr(os, entry.first, "producer name"); writeStr(os, entry.second, "producer version"); } } } void TargetFeaturesSection::writeBody() { SmallVector emitted(features.begin(), features.end()); llvm::sort(emitted); auto &os = bodyOutputStream; writeUleb128(os, emitted.size(), "feature count"); for (auto &feature : emitted) { writeU8(os, WASM_FEATURE_PREFIX_USED, "feature used prefix"); writeStr(os, feature, "feature name"); } } void RelocSection::writeBody() { uint32_t count = sec->getNumRelocations(); assert(sec->sectionIndex != UINT32_MAX); writeUleb128(bodyOutputStream, sec->sectionIndex, "reloc section"); writeUleb128(bodyOutputStream, count, "reloc count"); sec->writeRelocations(bodyOutputStream); } } // namespace wasm } // namespace lld