llvm-project/lld/wasm/SyntheticSections.cpp

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//===- 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<FunctionSymbol>(sym))
f->setFunctionIndex(numImportedFunctions++);
else if (auto *g = dyn_cast<GlobalSymbol>(sym))
g->setGlobalIndex(numImportedGlobals++);
else
cast<EventSymbol>(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))
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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<UndefinedFunction>(sym)) {
import.Field = f->importName ? *f->importName : sym->getName();
import.Module = f->importModule ? *f->importModule : defaultModule;
} else if (auto *g = dyn_cast<UndefinedGlobal>(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<FunctionSymbol>(sym)) {
import.Kind = WASM_EXTERNAL_FUNCTION;
import.SigIndex = out.typeSec->lookupType(*functionSym->signature);
} else if (auto *globalSym = dyn_cast<GlobalSymbol>(sym)) {
import.Kind = WASM_EXTERNAL_GLOBAL;
import.Global = *globalSym->getGlobalType();
} else {
auto *eventSym = cast<EventSymbol>(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<DataSymbol>(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, WasmTable{0, 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))
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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<FunctionSymbol>(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<DefinedData>(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<FunctionSymbol>(sym)) {
// 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<UndefinedData>(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;
global.Type = {WASM_TYPE_I32, config->isPic};
global.InitExpr.Opcode = WASM_OPCODE_I32_CONST;
if (auto *d = dyn_cast<DefinedData>(sym))
global.InitExpr.Value.Int32 = d->getVirtualAddress();
else if (auto *f = dyn_cast<FunctionSymbol>(sym))
global.InitExpr.Value.Int32 = f->getTableIndex();
else {
assert(isa<UndefinedData>(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 !config->relocatable && hasInitializedSegments && config->sharedMemory;
}
void StartSection::writeBody() {
raw_ostream &os = bodyOutputStream;
writeUleb128(os, WasmSym::initMemory->getFunctionIndex(), "function index");
}
void ElemSection::addEntry(FunctionSymbol *sym) {
if (sym->hasTableIndex())
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<OutputSegment *> 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<FunctionSymbol>(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<GlobalSymbol>(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<EventSymbol>(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<DataSymbol>(sym)) {
writeStr(sub.os, sym->getName(), "sym name");
if (auto *dataSym = dyn_cast<DefinedData>(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<OutputSectionSymbol>(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<StringRef, std::vector<ComdatEntry>> 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<FunctionSymbol>(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<GlobalSymbol>(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<std::string, std::string> 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<std::string, 8> 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