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llvm-capstone/lld/wasm/InputFiles.cpp
Andy Wingo 6339382807 [WebAssembly] Add support for table linking to wasm-ld 
This patch adds support to wasm-ld for linking multiple table references
together, in a manner similar to wasm globals. The indirect function
table is synthesized as needed.

To manage the transitional period in which the compiler doesn't yet
produce TABLE_NUMBER relocations and doesn't residualize table symbols,
the linker will detect object files which have table imports or
definitions, but no table symbols. In that case it will synthesize
symbols for the defined and imported tables.

As a change, relocatable objects are now written with table symbols,
which can cause symbol renumbering in some of the tests. If no object
file requires an indirect function table, none will be written to the
file. Note that for legacy ObjFile inputs, this test is conservative: as
we don't have relocs for each use of the indirecy function table, we
just assume that any incoming indirect function table should be
propagated to the output.

Differential Revision: https://reviews.llvm.org/D91870
2021-01-18 16:57:18 +01:00

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//===- InputFiles.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
//
//===----------------------------------------------------------------------===//
#include "InputFiles.h"
#include "Config.h"
#include "InputChunks.h"
#include "InputEvent.h"
#include "InputGlobal.h"
#include "InputTable.h"
#include "OutputSegment.h"
#include "SymbolTable.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/Memory.h"
#include "lld/Common/Reproduce.h"
#include "llvm/Object/Binary.h"
#include "llvm/Object/Wasm.h"
#include "llvm/Support/TarWriter.h"
#include "llvm/Support/raw_ostream.h"
#define DEBUG_TYPE "lld"
using namespace llvm;
using namespace llvm::object;
using namespace llvm::wasm;
namespace lld {
// Returns a string in the format of "foo.o" or "foo.a(bar.o)".
std::string toString(const wasm::InputFile *file) {
if (!file)
return "<internal>";
if (file->archiveName.empty())
return std::string(file->getName());
return (file->archiveName + "(" + file->getName() + ")").str();
}
namespace wasm {
void InputFile::checkArch(Triple::ArchType arch) const {
bool is64 = arch == Triple::wasm64;
if (is64 && !config->is64.hasValue()) {
fatal(toString(this) +
": must specify -mwasm64 to process wasm64 object files");
} else if (config->is64.getValueOr(false) != is64) {
fatal(toString(this) +
": wasm32 object file can't be linked in wasm64 mode");
}
}
std::unique_ptr<llvm::TarWriter> tar;
Optional<MemoryBufferRef> readFile(StringRef path) {
log("Loading: " + path);
auto mbOrErr = MemoryBuffer::getFile(path);
if (auto ec = mbOrErr.getError()) {
error("cannot open " + path + ": " + ec.message());
return None;
}
std::unique_ptr<MemoryBuffer> &mb = *mbOrErr;
MemoryBufferRef mbref = mb->getMemBufferRef();
make<std::unique_ptr<MemoryBuffer>>(std::move(mb)); // take MB ownership
if (tar)
tar->append(relativeToRoot(path), mbref.getBuffer());
return mbref;
}
InputFile *createObjectFile(MemoryBufferRef mb, StringRef archiveName) {
file_magic magic = identify_magic(mb.getBuffer());
if (magic == file_magic::wasm_object) {
std::unique_ptr<Binary> bin =
CHECK(createBinary(mb), mb.getBufferIdentifier());
auto *obj = cast<WasmObjectFile>(bin.get());
if (obj->isSharedObject())
return make<SharedFile>(mb);
return make<ObjFile>(mb, archiveName);
}
if (magic == file_magic::bitcode)
return make<BitcodeFile>(mb, archiveName);
fatal("unknown file type: " + mb.getBufferIdentifier());
}
void ObjFile::dumpInfo() const {
log("info for: " + toString(this) +
"\n Symbols : " + Twine(symbols.size()) +
"\n Function Imports : " + Twine(wasmObj->getNumImportedFunctions()) +
"\n Global Imports : " + Twine(wasmObj->getNumImportedGlobals()) +
"\n Event Imports : " + Twine(wasmObj->getNumImportedEvents()) +
"\n Table Imports : " + Twine(wasmObj->getNumImportedTables()));
}
// Relocations contain either symbol or type indices. This function takes a
// relocation and returns relocated index (i.e. translates from the input
// symbol/type space to the output symbol/type space).
uint32_t ObjFile::calcNewIndex(const WasmRelocation &reloc) const {
if (reloc.Type == R_WASM_TYPE_INDEX_LEB) {
assert(typeIsUsed[reloc.Index]);
return typeMap[reloc.Index];
}
const Symbol *sym = symbols[reloc.Index];
if (auto *ss = dyn_cast<SectionSymbol>(sym))
sym = ss->getOutputSectionSymbol();
return sym->getOutputSymbolIndex();
}
// Relocations can contain addend for combined sections. This function takes a
// relocation and returns updated addend by offset in the output section.
uint64_t ObjFile::calcNewAddend(const WasmRelocation &reloc) const {
switch (reloc.Type) {
case R_WASM_MEMORY_ADDR_LEB:
case R_WASM_MEMORY_ADDR_LEB64:
case R_WASM_MEMORY_ADDR_SLEB64:
case R_WASM_MEMORY_ADDR_SLEB:
case R_WASM_MEMORY_ADDR_REL_SLEB:
case R_WASM_MEMORY_ADDR_REL_SLEB64:
case R_WASM_MEMORY_ADDR_I32:
case R_WASM_MEMORY_ADDR_I64:
case R_WASM_MEMORY_ADDR_TLS_SLEB:
case R_WASM_FUNCTION_OFFSET_I32:
case R_WASM_FUNCTION_OFFSET_I64:
return reloc.Addend;
case R_WASM_SECTION_OFFSET_I32:
return getSectionSymbol(reloc.Index)->section->outputOffset + reloc.Addend;
default:
llvm_unreachable("unexpected relocation type");
}
}
// Calculate the value we expect to find at the relocation location.
// This is used as a sanity check before applying a relocation to a given
// location. It is useful for catching bugs in the compiler and linker.
uint64_t ObjFile::calcExpectedValue(const WasmRelocation &reloc) const {
switch (reloc.Type) {
case R_WASM_TABLE_INDEX_I32:
case R_WASM_TABLE_INDEX_I64:
case R_WASM_TABLE_INDEX_SLEB:
case R_WASM_TABLE_INDEX_SLEB64: {
const WasmSymbol &sym = wasmObj->syms()[reloc.Index];
return tableEntries[sym.Info.ElementIndex];
}
case R_WASM_TABLE_INDEX_REL_SLEB: {
const WasmSymbol &sym = wasmObj->syms()[reloc.Index];
return tableEntriesRel[sym.Info.ElementIndex];
}
case R_WASM_MEMORY_ADDR_LEB:
case R_WASM_MEMORY_ADDR_LEB64:
case R_WASM_MEMORY_ADDR_SLEB:
case R_WASM_MEMORY_ADDR_SLEB64:
case R_WASM_MEMORY_ADDR_REL_SLEB:
case R_WASM_MEMORY_ADDR_REL_SLEB64:
case R_WASM_MEMORY_ADDR_I32:
case R_WASM_MEMORY_ADDR_I64:
case R_WASM_MEMORY_ADDR_TLS_SLEB: {
const WasmSymbol &sym = wasmObj->syms()[reloc.Index];
if (sym.isUndefined())
return 0;
const WasmSegment &segment =
wasmObj->dataSegments()[sym.Info.DataRef.Segment];
if (segment.Data.Offset.Opcode == WASM_OPCODE_I32_CONST)
return segment.Data.Offset.Value.Int32 + sym.Info.DataRef.Offset +
reloc.Addend;
else if (segment.Data.Offset.Opcode == WASM_OPCODE_I64_CONST)
return segment.Data.Offset.Value.Int64 + sym.Info.DataRef.Offset +
reloc.Addend;
else
llvm_unreachable("unknown init expr opcode");
}
case R_WASM_FUNCTION_OFFSET_I32:
case R_WASM_FUNCTION_OFFSET_I64: {
const WasmSymbol &sym = wasmObj->syms()[reloc.Index];
InputFunction *f =
functions[sym.Info.ElementIndex - wasmObj->getNumImportedFunctions()];
return f->getFunctionInputOffset() + f->getFunctionCodeOffset() +
reloc.Addend;
}
case R_WASM_SECTION_OFFSET_I32:
return reloc.Addend;
case R_WASM_TYPE_INDEX_LEB:
return reloc.Index;
case R_WASM_FUNCTION_INDEX_LEB:
case R_WASM_GLOBAL_INDEX_LEB:
case R_WASM_GLOBAL_INDEX_I32:
case R_WASM_EVENT_INDEX_LEB:
case R_WASM_TABLE_NUMBER_LEB: {
const WasmSymbol &sym = wasmObj->syms()[reloc.Index];
return sym.Info.ElementIndex;
}
default:
llvm_unreachable("unknown relocation type");
}
}
// Translate from the relocation's index into the final linked output value.
uint64_t ObjFile::calcNewValue(const WasmRelocation &reloc, uint64_t tombstone) const {
const Symbol* sym = nullptr;
if (reloc.Type != R_WASM_TYPE_INDEX_LEB) {
sym = symbols[reloc.Index];
// We can end up with relocations against non-live symbols. For example
// in debug sections. We return a tombstone value in debug symbol sections
// so this will not produce a valid range conflicting with ranges of actual
// code. In other sections we return reloc.Addend.
if ((isa<FunctionSymbol>(sym) || isa<DataSymbol>(sym)) && !sym->isLive())
return tombstone ? tombstone : reloc.Addend;
}
switch (reloc.Type) {
case R_WASM_TABLE_INDEX_I32:
case R_WASM_TABLE_INDEX_I64:
case R_WASM_TABLE_INDEX_SLEB:
case R_WASM_TABLE_INDEX_SLEB64:
case R_WASM_TABLE_INDEX_REL_SLEB: {
if (!getFunctionSymbol(reloc.Index)->hasTableIndex())
return 0;
uint32_t index = getFunctionSymbol(reloc.Index)->getTableIndex();
if (reloc.Type == R_WASM_TABLE_INDEX_REL_SLEB)
index -= config->tableBase;
return index;
}
case R_WASM_MEMORY_ADDR_LEB:
case R_WASM_MEMORY_ADDR_LEB64:
case R_WASM_MEMORY_ADDR_SLEB:
case R_WASM_MEMORY_ADDR_SLEB64:
case R_WASM_MEMORY_ADDR_REL_SLEB:
case R_WASM_MEMORY_ADDR_REL_SLEB64:
case R_WASM_MEMORY_ADDR_I32:
case R_WASM_MEMORY_ADDR_I64: {
if (isa<UndefinedData>(sym) || sym->isUndefWeak())
return 0;
auto D = cast<DefinedData>(sym);
// Treat non-TLS relocation against symbols that live in the TLS segment
// like TLS relocations. This beaviour exists to support older object
// files created before we introduced TLS relocations.
// TODO(sbc): Remove this legacy behaviour one day. This will break
// backward compat with old object files built with `-fPIC`.
if (D->segment && D->segment->outputSeg->name == ".tdata")
return D->getOutputSegmentOffset() + reloc.Addend;
return D->getVirtualAddress() + reloc.Addend;
}
case R_WASM_MEMORY_ADDR_TLS_SLEB:
if (isa<UndefinedData>(sym) || sym->isUndefWeak())
return 0;
// TLS relocations are relative to the start of the TLS output segment
return cast<DefinedData>(sym)->getOutputSegmentOffset() + reloc.Addend;
case R_WASM_TYPE_INDEX_LEB:
return typeMap[reloc.Index];
case R_WASM_FUNCTION_INDEX_LEB:
return getFunctionSymbol(reloc.Index)->getFunctionIndex();
case R_WASM_GLOBAL_INDEX_LEB:
case R_WASM_GLOBAL_INDEX_I32:
if (auto gs = dyn_cast<GlobalSymbol>(sym))
return gs->getGlobalIndex();
return sym->getGOTIndex();
case R_WASM_EVENT_INDEX_LEB:
return getEventSymbol(reloc.Index)->getEventIndex();
case R_WASM_FUNCTION_OFFSET_I32:
case R_WASM_FUNCTION_OFFSET_I64: {
auto *f = cast<DefinedFunction>(sym);
return f->function->outputOffset +
(f->function->getFunctionCodeOffset() + reloc.Addend);
}
case R_WASM_SECTION_OFFSET_I32:
return getSectionSymbol(reloc.Index)->section->outputOffset + reloc.Addend;
case R_WASM_TABLE_NUMBER_LEB:
return getTableSymbol(reloc.Index)->getTableNumber();
default:
llvm_unreachable("unknown relocation type");
}
}
template <class T>
static void setRelocs(const std::vector<T *> &chunks,
const WasmSection *section) {
if (!section)
return;
ArrayRef<WasmRelocation> relocs = section->Relocations;
assert(llvm::is_sorted(
relocs, [](const WasmRelocation &r1, const WasmRelocation &r2) {
return r1.Offset < r2.Offset;
}));
assert(llvm::is_sorted(chunks, [](InputChunk *c1, InputChunk *c2) {
return c1->getInputSectionOffset() < c2->getInputSectionOffset();
}));
auto relocsNext = relocs.begin();
auto relocsEnd = relocs.end();
auto relocLess = [](const WasmRelocation &r, uint32_t val) {
return r.Offset < val;
};
for (InputChunk *c : chunks) {
auto relocsStart = std::lower_bound(relocsNext, relocsEnd,
c->getInputSectionOffset(), relocLess);
relocsNext = std::lower_bound(
relocsStart, relocsEnd, c->getInputSectionOffset() + c->getInputSize(),
relocLess);
c->setRelocations(ArrayRef<WasmRelocation>(relocsStart, relocsNext));
}
}
// Since LLVM 12, we expect that if an input file defines or uses a table, it
// declares the tables using symbols and records each use with a relocation.
// This way when the linker combines inputs, it can collate the tables used by
// the inputs, assigning them distinct table numbers, and renumber all the uses
// as appropriate. At the same time, the linker has special logic to build the
// indirect function table if it is needed.
//
// However, object files produced by LLVM 11 and earlier neither write table
// symbols nor record relocations, and yet still use tables via call_indirect,
// and via function pointer bitcasts. We can detect these object files, as they
// declare tables as imports or define them locally, but don't have table
// symbols. synthesizeTableSymbols serves as a shim when loading these older
// input files, defining the missing symbols to allow the indirect function
// table to be built.
//
// Table uses in these older files won't be relocated, as they have no
// relocations. In practice this isn't a problem, as these object files
// typically just declare a single table named __indirect_function_table and
// having table number 0, so relocation would be idempotent anyway.
void ObjFile::synthesizeTableSymbols() {
uint32_t tableNumber = 0;
const WasmGlobalType *globalType = nullptr;
const WasmEventType *eventType = nullptr;
const WasmSignature *signature = nullptr;
if (wasmObj->getNumImportedTables()) {
for (const auto &import : wasmObj->imports()) {
if (import.Kind == WASM_EXTERNAL_TABLE) {
auto *info = make<WasmSymbolInfo>();
info->Name = import.Field;
info->Kind = WASM_SYMBOL_TYPE_TABLE;
info->ImportModule = import.Module;
info->ImportName = import.Field;
info->Flags = WASM_SYMBOL_UNDEFINED;
info->Flags |= WASM_SYMBOL_NO_STRIP;
info->ElementIndex = tableNumber++;
LLVM_DEBUG(dbgs() << "Synthesizing symbol for table import: "
<< info->Name << "\n");
auto *wasmSym = make<WasmSymbol>(*info, globalType, &import.Table,
eventType, signature);
symbols.push_back(createUndefined(*wasmSym, false));
// Because there are no TABLE_NUMBER relocs in this case, we can't
// compute accurate liveness info; instead, just mark the symbol as
// always live.
symbols.back()->markLive();
}
}
}
for (const auto &table : tables) {
auto *info = make<llvm::wasm::WasmSymbolInfo>();
// Empty name.
info->Kind = WASM_SYMBOL_TYPE_TABLE;
info->Flags = WASM_SYMBOL_BINDING_LOCAL;
info->Flags |= WASM_SYMBOL_VISIBILITY_HIDDEN;
info->Flags |= WASM_SYMBOL_NO_STRIP;
info->ElementIndex = tableNumber++;
LLVM_DEBUG(dbgs() << "Synthesizing symbol for table definition: "
<< info->Name << "\n");
auto *wasmSym = make<WasmSymbol>(*info, globalType, &table->getType(),
eventType, signature);
symbols.push_back(createDefined(*wasmSym));
// Mark live, for the same reasons as for imported tables.
symbols.back()->markLive();
}
}
void ObjFile::parse(bool ignoreComdats) {
// Parse a memory buffer as a wasm file.
LLVM_DEBUG(dbgs() << "Parsing object: " << toString(this) << "\n");
std::unique_ptr<Binary> bin = CHECK(createBinary(mb), toString(this));
auto *obj = dyn_cast<WasmObjectFile>(bin.get());
if (!obj)
fatal(toString(this) + ": not a wasm file");
if (!obj->isRelocatableObject())
fatal(toString(this) + ": not a relocatable wasm file");
bin.release();
wasmObj.reset(obj);
checkArch(obj->getArch());
// Build up a map of function indices to table indices for use when
// verifying the existing table index relocations
uint32_t totalFunctions =
wasmObj->getNumImportedFunctions() + wasmObj->functions().size();
tableEntriesRel.resize(totalFunctions);
tableEntries.resize(totalFunctions);
for (const WasmElemSegment &seg : wasmObj->elements()) {
int64_t offset;
if (seg.Offset.Opcode == WASM_OPCODE_I32_CONST)
offset = seg.Offset.Value.Int32;
else if (seg.Offset.Opcode == WASM_OPCODE_I64_CONST)
offset = seg.Offset.Value.Int64;
else
fatal(toString(this) + ": invalid table elements");
for (size_t index = 0; index < seg.Functions.size(); index++) {
auto functionIndex = seg.Functions[index];
tableEntriesRel[functionIndex] = index;
tableEntries[functionIndex] = offset + index;
}
}
ArrayRef<StringRef> comdats = wasmObj->linkingData().Comdats;
for (StringRef comdat : comdats) {
bool isNew = ignoreComdats || symtab->addComdat(comdat);
keptComdats.push_back(isNew);
}
uint32_t sectionIndex = 0;
// Bool for each symbol, true if called directly. This allows us to implement
// a weaker form of signature checking where undefined functions that are not
// called directly (i.e. only address taken) don't have to match the defined
// function's signature. We cannot do this for directly called functions
// because those signatures are checked at validation times.
// See https://bugs.llvm.org/show_bug.cgi?id=40412
std::vector<bool> isCalledDirectly(wasmObj->getNumberOfSymbols(), false);
for (const SectionRef &sec : wasmObj->sections()) {
const WasmSection &section = wasmObj->getWasmSection(sec);
// Wasm objects can have at most one code and one data section.
if (section.Type == WASM_SEC_CODE) {
assert(!codeSection);
codeSection = &section;
} else if (section.Type == WASM_SEC_DATA) {
assert(!dataSection);
dataSection = &section;
} else if (section.Type == WASM_SEC_CUSTOM) {
auto *customSec = make<InputSection>(section, this);
customSec->discarded = isExcludedByComdat(customSec);
customSections.emplace_back(customSec);
customSections.back()->setRelocations(section.Relocations);
customSectionsByIndex[sectionIndex] = customSections.back();
}
sectionIndex++;
// Scans relocations to determine if a function symbol is called directly.
for (const WasmRelocation &reloc : section.Relocations)
if (reloc.Type == R_WASM_FUNCTION_INDEX_LEB)
isCalledDirectly[reloc.Index] = true;
}
typeMap.resize(getWasmObj()->types().size());
typeIsUsed.resize(getWasmObj()->types().size(), false);
// Populate `Segments`.
for (const WasmSegment &s : wasmObj->dataSegments()) {
auto* seg = make<InputSegment>(s, this);
seg->discarded = isExcludedByComdat(seg);
segments.emplace_back(seg);
}
setRelocs(segments, dataSection);
// Populate `Functions`.
ArrayRef<WasmFunction> funcs = wasmObj->functions();
ArrayRef<uint32_t> funcTypes = wasmObj->functionTypes();
ArrayRef<WasmSignature> types = wasmObj->types();
functions.reserve(funcs.size());
for (size_t i = 0, e = funcs.size(); i != e; ++i) {
auto* func = make<InputFunction>(types[funcTypes[i]], &funcs[i], this);
func->discarded = isExcludedByComdat(func);
functions.emplace_back(func);
}
setRelocs(functions, codeSection);
// Populate `Tables`.
for (const WasmTable &t : wasmObj->tables())
tables.emplace_back(make<InputTable>(t, this));
// Populate `Globals`.
for (const WasmGlobal &g : wasmObj->globals())
globals.emplace_back(make<InputGlobal>(g, this));
// Populate `Events`.
for (const WasmEvent &e : wasmObj->events())
events.emplace_back(make<InputEvent>(types[e.Type.SigIndex], e, this));
// Populate `Symbols` based on the symbols in the object.
symbols.reserve(wasmObj->getNumberOfSymbols());
bool haveTableSymbol = false;
for (const SymbolRef &sym : wasmObj->symbols()) {
const WasmSymbol &wasmSym = wasmObj->getWasmSymbol(sym.getRawDataRefImpl());
if (wasmSym.isTypeTable())
haveTableSymbol = true;
if (wasmSym.isDefined()) {
// createDefined may fail if the symbol is comdat excluded in which case
// we fall back to creating an undefined symbol
if (Symbol *d = createDefined(wasmSym)) {
symbols.push_back(d);
continue;
}
}
size_t idx = symbols.size();
symbols.push_back(createUndefined(wasmSym, isCalledDirectly[idx]));
}
// As a stopgap measure while implementing table support, if the object file
// has table definitions or imports but no table symbols, synthesize symbols
// for those tables. Mark as NO_STRIP to ensure they reach the output file,
// even if there are no TABLE_NUMBER relocs against them.
if (!haveTableSymbol)
synthesizeTableSymbols();
}
bool ObjFile::isExcludedByComdat(InputChunk *chunk) const {
uint32_t c = chunk->getComdat();
if (c == UINT32_MAX)
return false;
return !keptComdats[c];
}
FunctionSymbol *ObjFile::getFunctionSymbol(uint32_t index) const {
return cast<FunctionSymbol>(symbols[index]);
}
GlobalSymbol *ObjFile::getGlobalSymbol(uint32_t index) const {
return cast<GlobalSymbol>(symbols[index]);
}
EventSymbol *ObjFile::getEventSymbol(uint32_t index) const {
return cast<EventSymbol>(symbols[index]);
}
TableSymbol *ObjFile::getTableSymbol(uint32_t index) const {
return cast<TableSymbol>(symbols[index]);
}
SectionSymbol *ObjFile::getSectionSymbol(uint32_t index) const {
return cast<SectionSymbol>(symbols[index]);
}
DataSymbol *ObjFile::getDataSymbol(uint32_t index) const {
return cast<DataSymbol>(symbols[index]);
}
Symbol *ObjFile::createDefined(const WasmSymbol &sym) {
StringRef name = sym.Info.Name;
uint32_t flags = sym.Info.Flags;
switch (sym.Info.Kind) {
case WASM_SYMBOL_TYPE_FUNCTION: {
InputFunction *func =
functions[sym.Info.ElementIndex - wasmObj->getNumImportedFunctions()];
if (sym.isBindingLocal())
return make<DefinedFunction>(name, flags, this, func);
if (func->discarded)
return nullptr;
return symtab->addDefinedFunction(name, flags, this, func);
}
case WASM_SYMBOL_TYPE_DATA: {
InputSegment *seg = segments[sym.Info.DataRef.Segment];
auto offset = sym.Info.DataRef.Offset;
auto size = sym.Info.DataRef.Size;
if (sym.isBindingLocal())
return make<DefinedData>(name, flags, this, seg, offset, size);
if (seg->discarded)
return nullptr;
return symtab->addDefinedData(name, flags, this, seg, offset, size);
}
case WASM_SYMBOL_TYPE_GLOBAL: {
InputGlobal *global =
globals[sym.Info.ElementIndex - wasmObj->getNumImportedGlobals()];
if (sym.isBindingLocal())
return make<DefinedGlobal>(name, flags, this, global);
return symtab->addDefinedGlobal(name, flags, this, global);
}
case WASM_SYMBOL_TYPE_SECTION: {
InputSection *section = customSectionsByIndex[sym.Info.ElementIndex];
assert(sym.isBindingLocal());
// Need to return null if discarded here? data and func only do that when
// binding is not local.
if (section->discarded)
return nullptr;
return make<SectionSymbol>(flags, section, this);
}
case WASM_SYMBOL_TYPE_EVENT: {
InputEvent *event =
events[sym.Info.ElementIndex - wasmObj->getNumImportedEvents()];
if (sym.isBindingLocal())
return make<DefinedEvent>(name, flags, this, event);
return symtab->addDefinedEvent(name, flags, this, event);
}
case WASM_SYMBOL_TYPE_TABLE: {
InputTable *table =
tables[sym.Info.ElementIndex - wasmObj->getNumImportedTables()];
if (sym.isBindingLocal())
return make<DefinedTable>(name, flags, this, table);
return symtab->addDefinedTable(name, flags, this, table);
}
}
llvm_unreachable("unknown symbol kind");
}
Symbol *ObjFile::createUndefined(const WasmSymbol &sym, bool isCalledDirectly) {
StringRef name = sym.Info.Name;
uint32_t flags = sym.Info.Flags | WASM_SYMBOL_UNDEFINED;
switch (sym.Info.Kind) {
case WASM_SYMBOL_TYPE_FUNCTION:
if (sym.isBindingLocal())
return make<UndefinedFunction>(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.Signature, isCalledDirectly);
return symtab->addUndefinedFunction(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.Signature, isCalledDirectly);
case WASM_SYMBOL_TYPE_DATA:
if (sym.isBindingLocal())
return make<UndefinedData>(name, flags, this);
return symtab->addUndefinedData(name, flags, this);
case WASM_SYMBOL_TYPE_GLOBAL:
if (sym.isBindingLocal())
return make<UndefinedGlobal>(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.GlobalType);
return symtab->addUndefinedGlobal(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.GlobalType);
case WASM_SYMBOL_TYPE_TABLE:
if (sym.isBindingLocal())
return make<UndefinedTable>(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.TableType);
return symtab->addUndefinedTable(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.TableType);
case WASM_SYMBOL_TYPE_SECTION:
llvm_unreachable("section symbols cannot be undefined");
}
llvm_unreachable("unknown symbol kind");
}
void ArchiveFile::parse() {
// Parse a MemoryBufferRef as an archive file.
LLVM_DEBUG(dbgs() << "Parsing library: " << toString(this) << "\n");
file = CHECK(Archive::create(mb), toString(this));
// Read the symbol table to construct Lazy symbols.
int count = 0;
for (const Archive::Symbol &sym : file->symbols()) {
symtab->addLazy(this, &sym);
++count;
}
LLVM_DEBUG(dbgs() << "Read " << count << " symbols\n");
}
void ArchiveFile::addMember(const Archive::Symbol *sym) {
const Archive::Child &c =
CHECK(sym->getMember(),
"could not get the member for symbol " + sym->getName());
// Don't try to load the same member twice (this can happen when members
// mutually reference each other).
if (!seen.insert(c.getChildOffset()).second)
return;
LLVM_DEBUG(dbgs() << "loading lazy: " << sym->getName() << "\n");
LLVM_DEBUG(dbgs() << "from archive: " << toString(this) << "\n");
MemoryBufferRef mb =
CHECK(c.getMemoryBufferRef(),
"could not get the buffer for the member defining symbol " +
sym->getName());
InputFile *obj = createObjectFile(mb, getName());
symtab->addFile(obj);
}
static uint8_t mapVisibility(GlobalValue::VisibilityTypes gvVisibility) {
switch (gvVisibility) {
case GlobalValue::DefaultVisibility:
return WASM_SYMBOL_VISIBILITY_DEFAULT;
case GlobalValue::HiddenVisibility:
case GlobalValue::ProtectedVisibility:
return WASM_SYMBOL_VISIBILITY_HIDDEN;
}
llvm_unreachable("unknown visibility");
}
static Symbol *createBitcodeSymbol(const std::vector<bool> &keptComdats,
const lto::InputFile::Symbol &objSym,
BitcodeFile &f) {
StringRef name = saver.save(objSym.getName());
uint32_t flags = objSym.isWeak() ? WASM_SYMBOL_BINDING_WEAK : 0;
flags |= mapVisibility(objSym.getVisibility());
int c = objSym.getComdatIndex();
bool excludedByComdat = c != -1 && !keptComdats[c];
if (objSym.isUndefined() || excludedByComdat) {
flags |= WASM_SYMBOL_UNDEFINED;
if (objSym.isExecutable())
return symtab->addUndefinedFunction(name, None, None, flags, &f, nullptr,
true);
return symtab->addUndefinedData(name, flags, &f);
}
if (objSym.isExecutable())
return symtab->addDefinedFunction(name, flags, &f, nullptr);
return symtab->addDefinedData(name, flags, &f, nullptr, 0, 0);
}
bool BitcodeFile::doneLTO = false;
void BitcodeFile::parse() {
if (doneLTO) {
error(toString(this) + ": attempt to add bitcode file after LTO.");
return;
}
obj = check(lto::InputFile::create(MemoryBufferRef(
mb.getBuffer(), saver.save(archiveName + mb.getBufferIdentifier()))));
Triple t(obj->getTargetTriple());
if (!t.isWasm()) {
error(toString(this) + ": machine type must be wasm32 or wasm64");
return;
}
checkArch(t.getArch());
std::vector<bool> keptComdats;
for (StringRef s : obj->getComdatTable())
keptComdats.push_back(symtab->addComdat(s));
for (const lto::InputFile::Symbol &objSym : obj->symbols())
symbols.push_back(createBitcodeSymbol(keptComdats, objSym, *this));
}
} // namespace wasm
} // namespace lld
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