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llvm-project/lld/wasm/Driver.cpp

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//===- Driver.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 "lld/Common/Driver.h"
#include "Config.h"
#include "InputChunks.h"
#include "InputElement.h"
#include "MarkLive.h"
#include "SymbolTable.h"
#include "Writer.h"
#include "lld/Common/Args.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/Filesystem.h"
#include "lld/Common/Memory.h"
#include "lld/Common/Reproduce.h"
#include "lld/Common/Strings.h"
#include "lld/Common/Version.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/Object/Wasm.h"
#include "llvm/Option/Arg.h"
#include "llvm/Option/ArgList.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/Parallel.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/TarWriter.h"
#include "llvm/Support/TargetSelect.h"
#define DEBUG_TYPE "lld"
using namespace llvm;
using namespace llvm::object;
using namespace llvm::sys;
using namespace llvm::wasm;
namespace lld {
namespace wasm {
Configuration *config;
namespace {
// Create enum with OPT_xxx values for each option in Options.td
enum {
OPT_INVALID = 0,
#define OPTION(_1, _2, ID, _4, _5, _6, _7, _8, _9, _10, _11, _12) OPT_##ID,
#include "Options.inc"
#undef OPTION
};
// This function is called on startup. We need this for LTO since
// LTO calls LLVM functions to compile bitcode files to native code.
// Technically this can be delayed until we read bitcode files, but
// we don't bother to do lazily because the initialization is fast.
static void initLLVM() {
InitializeAllTargets();
InitializeAllTargetMCs();
InitializeAllAsmPrinters();
InitializeAllAsmParsers();
}
class LinkerDriver {
public:
void linkerMain(ArrayRef<const char *> argsArr);
private:
void createFiles(opt::InputArgList &args);
void addFile(StringRef path);
void addLibrary(StringRef name);
// True if we are in --whole-archive and --no-whole-archive.
bool inWholeArchive = false;
std::vector<InputFile *> files;
};
} // anonymous namespace
bool link(ArrayRef<const char *> args, bool canExitEarly, raw_ostream &stdoutOS,
raw_ostream &stderrOS) {
lld::stdoutOS = &stdoutOS;
lld::stderrOS = &stderrOS;
errorHandler().cleanupCallback = []() { freeArena(); };
errorHandler().logName = args::getFilenameWithoutExe(args[0]);
errorHandler().errorLimitExceededMsg =
"too many errors emitted, stopping now (use "
"-error-limit=0 to see all errors)";
stderrOS.enable_colors(stderrOS.has_colors());
config = make<Configuration>();
symtab = make<SymbolTable>();
initLLVM();
LinkerDriver().linkerMain(args);
// Exit immediately if we don't need to return to the caller.
// This saves time because the overhead of calling destructors
// for all globally-allocated objects is not negligible.
if (canExitEarly)
exitLld(errorCount() ? 1 : 0);
return !errorCount();
}
// Create prefix string literals used in Options.td
#define PREFIX(NAME, VALUE) const char *const NAME[] = VALUE;
#include "Options.inc"
#undef PREFIX
// Create table mapping all options defined in Options.td
static const opt::OptTable::Info optInfo[] = {
#define OPTION(X1, X2, ID, KIND, GROUP, ALIAS, X7, X8, X9, X10, X11, X12) \
{X1, X2, X10, X11, OPT_##ID, opt::Option::KIND##Class, \
X9, X8, OPT_##GROUP, OPT_##ALIAS, X7, X12},
#include "Options.inc"
#undef OPTION
};
namespace {
class WasmOptTable : public llvm::opt::OptTable {
public:
WasmOptTable() : OptTable(optInfo) {}
opt::InputArgList parse(ArrayRef<const char *> argv);
};
} // namespace
// Set color diagnostics according to -color-diagnostics={auto,always,never}
// or -no-color-diagnostics flags.
static void handleColorDiagnostics(opt::InputArgList &args) {
auto *arg = args.getLastArg(OPT_color_diagnostics, OPT_color_diagnostics_eq,
OPT_no_color_diagnostics);
if (!arg)
return;
if (arg->getOption().getID() == OPT_color_diagnostics) {
lld::errs().enable_colors(true);
} else if (arg->getOption().getID() == OPT_no_color_diagnostics) {
lld::errs().enable_colors(false);
} else {
StringRef s = arg->getValue();
if (s == "always")
lld::errs().enable_colors(true);
else if (s == "never")
lld::errs().enable_colors(false);
else if (s != "auto")
error("unknown option: --color-diagnostics=" + s);
}
}
static cl::TokenizerCallback getQuotingStyle(opt::InputArgList &args) {
if (auto *arg = args.getLastArg(OPT_rsp_quoting)) {
StringRef s = arg->getValue();
if (s != "windows" && s != "posix")
error("invalid response file quoting: " + s);
if (s == "windows")
return cl::TokenizeWindowsCommandLine;
return cl::TokenizeGNUCommandLine;
}
if (Triple(sys::getProcessTriple()).isOSWindows())
return cl::TokenizeWindowsCommandLine;
return cl::TokenizeGNUCommandLine;
}
// Find a file by concatenating given paths.
static Optional<std::string> findFile(StringRef path1, const Twine &path2) {
SmallString<128> s;
path::append(s, path1, path2);
if (fs::exists(s))
return std::string(s);
return None;
}
opt::InputArgList WasmOptTable::parse(ArrayRef<const char *> argv) {
SmallVector<const char *, 256> vec(argv.data(), argv.data() + argv.size());
unsigned missingIndex;
unsigned missingCount;
// We need to get the quoting style for response files before parsing all
// options so we parse here before and ignore all the options but
// --rsp-quoting.
opt::InputArgList args = this->ParseArgs(vec, missingIndex, missingCount);
// Expand response files (arguments in the form of @<filename>)
// and then parse the argument again.
cl::ExpandResponseFiles(saver, getQuotingStyle(args), vec);
args = this->ParseArgs(vec, missingIndex, missingCount);
handleColorDiagnostics(args);
for (auto *arg : args.filtered(OPT_UNKNOWN))
error("unknown argument: " + arg->getAsString(args));
return args;
}
// Currently we allow a ".imports" to live alongside a library. This can
// be used to specify a list of symbols which can be undefined at link
// time (imported from the environment. For example libc.a include an
// import file that lists the syscall functions it relies on at runtime.
// In the long run this information would be better stored as a symbol
// attribute/flag in the object file itself.
// See: https://github.com/WebAssembly/tool-conventions/issues/35
static void readImportFile(StringRef filename) {
if (Optional<MemoryBufferRef> buf = readFile(filename))
for (StringRef sym : args::getLines(*buf))
config->allowUndefinedSymbols.insert(sym);
}
// Returns slices of MB by parsing MB as an archive file.
// Each slice consists of a member file in the archive.
std::vector<MemoryBufferRef> static getArchiveMembers(MemoryBufferRef mb) {
std::unique_ptr<Archive> file =
CHECK(Archive::create(mb),
mb.getBufferIdentifier() + ": failed to parse archive");
std::vector<MemoryBufferRef> v;
Error err = Error::success();
for (const Archive::Child &c : file->children(err)) {
MemoryBufferRef mbref =
CHECK(c.getMemoryBufferRef(),
mb.getBufferIdentifier() +
": could not get the buffer for a child of the archive");
v.push_back(mbref);
}
if (err)
fatal(mb.getBufferIdentifier() +
": Archive::children failed: " + toString(std::move(err)));
// Take ownership of memory buffers created for members of thin archives.
for (std::unique_ptr<MemoryBuffer> &mb : file->takeThinBuffers())
make<std::unique_ptr<MemoryBuffer>>(std::move(mb));
return v;
}
void LinkerDriver::addFile(StringRef path) {
Optional<MemoryBufferRef> buffer = readFile(path);
if (!buffer.hasValue())
return;
MemoryBufferRef mbref = *buffer;
switch (identify_magic(mbref.getBuffer())) {
case file_magic::archive: {
SmallString<128> importFile = path;
path::replace_extension(importFile, ".imports");
if (fs::exists(importFile))
readImportFile(importFile.str());
// Handle -whole-archive.
if (inWholeArchive) {
for (MemoryBufferRef &m : getArchiveMembers(mbref)) {
auto *object = createObjectFile(m, path);
// Mark object as live; object members are normally not
// live by default but -whole-archive is designed to treat
// them as such.
object->markLive();
files.push_back(object);
}
return;
}
std::unique_ptr<Archive> file =
CHECK(Archive::create(mbref), path + ": failed to parse archive");
if (!file->isEmpty() && !file->hasSymbolTable()) {
error(mbref.getBufferIdentifier() +
": archive has no index; run ranlib to add one");
}
files.push_back(make<ArchiveFile>(mbref));
return;
}
case file_magic::bitcode:
case file_magic::wasm_object:
files.push_back(createObjectFile(mbref));
break;
default:
error("unknown file type: " + mbref.getBufferIdentifier());
}
}
// Add a given library by searching it from input search paths.
void LinkerDriver::addLibrary(StringRef name) {
for (StringRef dir : config->searchPaths) {
if (Optional<std::string> s = findFile(dir, "lib" + name + ".a")) {
addFile(*s);
return;
}
}
error("unable to find library -l" + name);
}
void LinkerDriver::createFiles(opt::InputArgList &args) {
for (auto *arg : args) {
switch (arg->getOption().getID()) {
case OPT_l:
addLibrary(arg->getValue());
break;
case OPT_INPUT:
addFile(arg->getValue());
break;
case OPT_whole_archive:
inWholeArchive = true;
break;
case OPT_no_whole_archive:
inWholeArchive = false;
break;
}
}
if (files.empty() && errorCount() == 0)
error("no input files");
}
static StringRef getEntry(opt::InputArgList &args) {
auto *arg = args.getLastArg(OPT_entry, OPT_no_entry);
if (!arg) {
if (args.hasArg(OPT_relocatable))
return "";
if (args.hasArg(OPT_shared))
return "__wasm_call_ctors";
return "_start";
}
if (arg->getOption().getID() == OPT_no_entry)
return "";
return arg->getValue();
}
// Determines what we should do if there are remaining unresolved
// symbols after the name resolution.
static UnresolvedPolicy getUnresolvedSymbolPolicy(opt::InputArgList &args) {
UnresolvedPolicy errorOrWarn = args.hasFlag(OPT_error_unresolved_symbols,
OPT_warn_unresolved_symbols, true)
? UnresolvedPolicy::ReportError
: UnresolvedPolicy::Warn;
if (auto *arg = args.getLastArg(OPT_unresolved_symbols)) {
StringRef s = arg->getValue();
if (s == "ignore-all")
return UnresolvedPolicy::Ignore;
if (s == "import-functions")
return UnresolvedPolicy::ImportFuncs;
if (s == "report-all")
return errorOrWarn;
error("unknown --unresolved-symbols value: " + s);
}
// Legacy --allow-undefined flag which is equivalent to
// --unresolve-symbols=ignore-all
if (args.hasArg(OPT_allow_undefined))
return UnresolvedPolicy::ImportFuncs;
return errorOrWarn;
}
// Initializes Config members by the command line options.
static void readConfigs(opt::InputArgList &args) {
config->bsymbolic = args.hasArg(OPT_Bsymbolic);
config->checkFeatures =
args.hasFlag(OPT_check_features, OPT_no_check_features, true);
config->compressRelocations = args.hasArg(OPT_compress_relocations);
config->demangle = args.hasFlag(OPT_demangle, OPT_no_demangle, true);
config->disableVerify = args.hasArg(OPT_disable_verify);
config->emitRelocs = args.hasArg(OPT_emit_relocs);
config->experimentalPic = args.hasArg(OPT_experimental_pic);
config->entry = getEntry(args);
config->exportAll = args.hasArg(OPT_export_all);
config->exportTable = args.hasArg(OPT_export_table);
config->growableTable = args.hasArg(OPT_growable_table);
errorHandler().fatalWarnings =
args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false);
config->importMemory = args.hasArg(OPT_import_memory);
config->sharedMemory = args.hasArg(OPT_shared_memory);
config->importTable = args.hasArg(OPT_import_table);
config->ltoo = args::getInteger(args, OPT_lto_O, 2);
config->ltoPartitions = args::getInteger(args, OPT_lto_partitions, 1);
config->ltoNewPassManager =
args.hasFlag(OPT_no_lto_legacy_pass_manager, OPT_lto_legacy_pass_manager,
LLVM_ENABLE_NEW_PASS_MANAGER);
config->ltoDebugPassManager = args.hasArg(OPT_lto_debug_pass_manager);
config->mapFile = args.getLastArgValue(OPT_Map);
config->optimize = args::getInteger(args, OPT_O, 1);
config->outputFile = args.getLastArgValue(OPT_o);
config->relocatable = args.hasArg(OPT_relocatable);
config->gcSections =
args.hasFlag(OPT_gc_sections, OPT_no_gc_sections, !config->relocatable);
config->mergeDataSegments =
args.hasFlag(OPT_merge_data_segments, OPT_no_merge_data_segments,
!config->relocatable);
config->pie = args.hasFlag(OPT_pie, OPT_no_pie, false);
config->printGcSections =
args.hasFlag(OPT_print_gc_sections, OPT_no_print_gc_sections, false);
config->saveTemps = args.hasArg(OPT_save_temps);
config->searchPaths = args::getStrings(args, OPT_L);
config->shared = args.hasArg(OPT_shared);
config->stripAll = args.hasArg(OPT_strip_all);
config->stripDebug = args.hasArg(OPT_strip_debug);
config->stackFirst = args.hasArg(OPT_stack_first);
config->trace = args.hasArg(OPT_trace);
config->thinLTOCacheDir = args.getLastArgValue(OPT_thinlto_cache_dir);
config->thinLTOCachePolicy = CHECK(
parseCachePruningPolicy(args.getLastArgValue(OPT_thinlto_cache_policy)),
"--thinlto-cache-policy: invalid cache policy");
config->unresolvedSymbols = getUnresolvedSymbolPolicy(args);
errorHandler().verbose = args.hasArg(OPT_verbose);
LLVM_DEBUG(errorHandler().verbose = true);
config->initialMemory = args::getInteger(args, OPT_initial_memory, 0);
config->globalBase = args::getInteger(args, OPT_global_base, 1024);
config->maxMemory = args::getInteger(args, OPT_max_memory, 0);
config->zStackSize =
args::getZOptionValue(args, OPT_z, "stack-size", WasmPageSize);
// Default value of exportDynamic depends on `-shared`
config->exportDynamic =
args.hasFlag(OPT_export_dynamic, OPT_no_export_dynamic, config->shared);
// Parse wasm32/64.
if (auto *arg = args.getLastArg(OPT_m)) {
StringRef s = arg->getValue();
if (s == "wasm32")
config->is64 = false;
else if (s == "wasm64")
config->is64 = true;
else
error("invalid target architecture: " + s);
}
// --threads= takes a positive integer and provides the default value for
// --thinlto-jobs=.
if (auto *arg = args.getLastArg(OPT_threads)) {
StringRef v(arg->getValue());
unsigned threads = 0;
if (!llvm::to_integer(v, threads, 0) || threads == 0)
error(arg->getSpelling() + ": expected a positive integer, but got '" +
arg->getValue() + "'");
parallel::strategy = hardware_concurrency(threads);
config->thinLTOJobs = v;
}
if (auto *arg = args.getLastArg(OPT_thinlto_jobs))
config->thinLTOJobs = arg->getValue();
if (auto *arg = args.getLastArg(OPT_features)) {
config->features =
llvm::Optional<std::vector<std::string>>(std::vector<std::string>());
for (StringRef s : arg->getValues())
config->features->push_back(std::string(s));
}
if (args.hasArg(OPT_print_map))
config->mapFile = "-";
}
// Some Config members do not directly correspond to any particular
// command line options, but computed based on other Config values.
// This function initialize such members. See Config.h for the details
// of these values.
static void setConfigs() {
config->isPic = config->pie || config->shared;
if (config->isPic) {
if (config->exportTable)
error("-shared/-pie is incompatible with --export-table");
config->importTable = true;
}
if (config->relocatable) {
if (config->exportTable)
error("--relocatable is incompatible with --export-table");
if (config->growableTable)
error("--relocatable is incompatible with --growable-table");
// Ignore any --import-table, as it's redundant.
config->importTable = true;
}
if (config->shared) {
config->importMemory = true;
config->unresolvedSymbols = UnresolvedPolicy::ImportFuncs;
}
}
// Some command line options or some combinations of them are not allowed.
// This function checks for such errors.
static void checkOptions(opt::InputArgList &args) {
if (!config->stripDebug && !config->stripAll && config->compressRelocations)
error("--compress-relocations is incompatible with output debug"
" information. Please pass --strip-debug or --strip-all");
if (config->ltoo > 3)
error("invalid optimization level for LTO: " + Twine(config->ltoo));
if (config->ltoPartitions == 0)
error("--lto-partitions: number of threads must be > 0");
if (!get_threadpool_strategy(config->thinLTOJobs))
error("--thinlto-jobs: invalid job count: " + config->thinLTOJobs);
if (config->pie && config->shared)
error("-shared and -pie may not be used together");
if (config->outputFile.empty())
error("no output file specified");
if (config->importTable && config->exportTable)
error("--import-table and --export-table may not be used together");
if (config->relocatable) {
if (!config->entry.empty())
error("entry point specified for relocatable output file");
if (config->gcSections)
error("-r and --gc-sections may not be used together");
if (config->compressRelocations)
error("-r -and --compress-relocations may not be used together");
if (args.hasArg(OPT_undefined))
error("-r -and --undefined may not be used together");
if (config->pie)
error("-r and -pie may not be used together");
if (config->sharedMemory)
error("-r and --shared-memory may not be used together");
}
// To begin to prepare for Module Linking-style shared libraries, start
// warning about uses of `-shared` and related flags outside of Experimental
// mode, to give anyone using them a heads-up that they will be changing.
//
// Also, warn about flags which request explicit exports.
if (!config->experimentalPic) {
// -shared will change meaning when Module Linking is implemented.
if (config->shared) {
warn("creating shared libraries, with -shared, is not yet stable");
}
// -pie will change meaning when Module Linking is implemented.
if (config->pie) {
warn("creating PIEs, with -pie, is not yet stable");
}
}
if (config->bsymbolic && !config->shared) {
warn("-Bsymbolic is only meaningful when combined with -shared");
}
}
// Force Sym to be entered in the output. Used for -u or equivalent.
static Symbol *handleUndefined(StringRef name) {
Symbol *sym = symtab->find(name);
if (!sym)
return nullptr;
// Since symbol S may not be used inside the program, LTO may
// eliminate it. Mark the symbol as "used" to prevent it.
sym->isUsedInRegularObj = true;
if (auto *lazySym = dyn_cast<LazySymbol>(sym))
lazySym->fetch();
return sym;
}
static void handleLibcall(StringRef name) {
Symbol *sym = symtab->find(name);
if (!sym)
return;
if (auto *lazySym = dyn_cast<LazySymbol>(sym)) {
MemoryBufferRef mb = lazySym->getMemberBuffer();
if (isBitcode(mb))
lazySym->fetch();
}
}
static UndefinedGlobal *
createUndefinedGlobal(StringRef name, llvm::wasm::WasmGlobalType *type) {
auto *sym = cast<UndefinedGlobal>(symtab->addUndefinedGlobal(
name, None, None, WASM_SYMBOL_UNDEFINED, nullptr, type));
config->allowUndefinedSymbols.insert(sym->getName());
sym->isUsedInRegularObj = true;
return sym;
}
static InputGlobal *createGlobal(StringRef name, bool isMutable) {
llvm::wasm::WasmGlobal wasmGlobal;
bool is64 = config->is64.getValueOr(false);
wasmGlobal.Type = {uint8_t(is64 ? WASM_TYPE_I64 : WASM_TYPE_I32), isMutable};
wasmGlobal.InitExpr = intConst(0, is64);
wasmGlobal.SymbolName = name;
return make<InputGlobal>(wasmGlobal, nullptr);
}
static GlobalSymbol *createGlobalVariable(StringRef name, bool isMutable) {
InputGlobal *g = createGlobal(name, isMutable);
return symtab->addSyntheticGlobal(name, WASM_SYMBOL_VISIBILITY_HIDDEN, g);
}
static GlobalSymbol *createOptionalGlobal(StringRef name, bool isMutable) {
InputGlobal *g = createGlobal(name, isMutable);
return symtab->addOptionalGlobalSymbol(name, g);
}
// Create ABI-defined synthetic symbols
static void createSyntheticSymbols() {
if (config->relocatable)
return;
static WasmSignature nullSignature = {{}, {}};
static WasmSignature i32ArgSignature = {{}, {ValType::I32}};
static WasmSignature i64ArgSignature = {{}, {ValType::I64}};
static llvm::wasm::WasmGlobalType globalTypeI32 = {WASM_TYPE_I32, false};
static llvm::wasm::WasmGlobalType globalTypeI64 = {WASM_TYPE_I64, false};
static llvm::wasm::WasmGlobalType mutableGlobalTypeI32 = {WASM_TYPE_I32,
true};
static llvm::wasm::WasmGlobalType mutableGlobalTypeI64 = {WASM_TYPE_I64,
true};
WasmSym::callCtors = symtab->addSyntheticFunction(
"__wasm_call_ctors", WASM_SYMBOL_VISIBILITY_HIDDEN,
make<SyntheticFunction>(nullSignature, "__wasm_call_ctors"));
if (config->isPic) {
WasmSym::stackPointer =
createUndefinedGlobal("__stack_pointer", config->is64.getValueOr(false)
? &mutableGlobalTypeI64
: &mutableGlobalTypeI32);
// For PIC code, we import two global variables (__memory_base and
// __table_base) from the environment and use these as the offset at
// which to load our static data and function table.
// See:
// https://github.com/WebAssembly/tool-conventions/blob/master/DynamicLinking.md
bool is64 = config->is64.getValueOr(false);
auto *globalType = is64 ? &globalTypeI64 : &globalTypeI32;
WasmSym::memoryBase = createUndefinedGlobal("__memory_base", globalType);
WasmSym::tableBase = createUndefinedGlobal("__table_base", globalType);
WasmSym::memoryBase->markLive();
WasmSym::tableBase->markLive();
if (is64) {
WasmSym::tableBase32 =
createUndefinedGlobal("__table_base32", &globalTypeI32);
WasmSym::tableBase32->markLive();
} else {
WasmSym::tableBase32 = nullptr;
}
} else {
// For non-PIC code
WasmSym::stackPointer = createGlobalVariable("__stack_pointer", true);
WasmSym::stackPointer->markLive();
}
if (config->sharedMemory && !config->relocatable) {
WasmSym::tlsBase = createGlobalVariable("__tls_base", true);
WasmSym::tlsSize = createGlobalVariable("__tls_size", false);
WasmSym::tlsAlign = createGlobalVariable("__tls_align", false);
WasmSym::initTLS = symtab->addSyntheticFunction(
"__wasm_init_tls", WASM_SYMBOL_VISIBILITY_HIDDEN,
make<SyntheticFunction>(
config->is64.getValueOr(false) ? i64ArgSignature : i32ArgSignature,
"__wasm_init_tls"));
}
}
static void createOptionalSymbols() {
if (config->relocatable)
return;
WasmSym::dsoHandle = symtab->addOptionalDataSymbol("__dso_handle");
if (!config->shared)
WasmSym::dataEnd = symtab->addOptionalDataSymbol("__data_end");
if (!config->isPic) {
WasmSym::globalBase = symtab->addOptionalDataSymbol("__global_base");
WasmSym::heapBase = symtab->addOptionalDataSymbol("__heap_base");
WasmSym::definedMemoryBase = symtab->addOptionalDataSymbol("__memory_base");
WasmSym::definedTableBase = symtab->addOptionalDataSymbol("__table_base");
if (config->is64.getValueOr(false))
WasmSym::definedTableBase32 =
symtab->addOptionalDataSymbol("__table_base32");
}
// For non-shared memory programs we still need to define __tls_base since we
// allow object files built with TLS to be linked into single threaded
// programs, and such object files can contains refernced to this symbol.
//
// However, in this case __tls_base is immutable and points directly to the
// start of the `.tdata` static segment.
//
// __tls_size and __tls_align are not needed in this case since they are only
// needed for __wasm_init_tls (which we do not create in this case).
if (!config->sharedMemory)
WasmSym::tlsBase = createOptionalGlobal("__tls_base", false);
}
// Reconstructs command line arguments so that so that you can re-run
// the same command with the same inputs. This is for --reproduce.
static std::string createResponseFile(const opt::InputArgList &args) {
SmallString<0> data;
raw_svector_ostream os(data);
// Copy the command line to the output while rewriting paths.
for (auto *arg : args) {
switch (arg->getOption().getID()) {
case OPT_reproduce:
break;
case OPT_INPUT:
os << quote(relativeToRoot(arg->getValue())) << "\n";
break;
case OPT_o:
// If -o path contains directories, "lld @response.txt" will likely
// fail because the archive we are creating doesn't contain empty
// directories for the output path (-o doesn't create directories).
// Strip directories to prevent the issue.
os << "-o " << quote(sys::path::filename(arg->getValue())) << "\n";
break;
default:
os << toString(*arg) << "\n";
}
}
return std::string(data.str());
}
// The --wrap option is a feature to rename symbols so that you can write
// wrappers for existing functions. If you pass `-wrap=foo`, all
// occurrences of symbol `foo` are resolved to `wrap_foo` (so, you are
// expected to write `wrap_foo` function as a wrapper). The original
// symbol becomes accessible as `real_foo`, so you can call that from your
// wrapper.
//
// This data structure is instantiated for each -wrap option.
struct WrappedSymbol {
Symbol *sym;
Symbol *real;
Symbol *wrap;
};
static Symbol *addUndefined(StringRef name) {
return symtab->addUndefinedFunction(name, None, None, WASM_SYMBOL_UNDEFINED,
nullptr, nullptr, false);
}
// Handles -wrap option.
//
// This function instantiates wrapper symbols. At this point, they seem
// like they are not being used at all, so we explicitly set some flags so
// that LTO won't eliminate them.
static std::vector<WrappedSymbol> addWrappedSymbols(opt::InputArgList &args) {
std::vector<WrappedSymbol> v;
DenseSet<StringRef> seen;
for (auto *arg : args.filtered(OPT_wrap)) {
StringRef name = arg->getValue();
if (!seen.insert(name).second)
continue;
Symbol *sym = symtab->find(name);
if (!sym)
continue;
Symbol *real = addUndefined(saver.save("__real_" + name));
Symbol *wrap = addUndefined(saver.save("__wrap_" + name));
v.push_back({sym, real, wrap});
// We want to tell LTO not to inline symbols to be overwritten
// because LTO doesn't know the final symbol contents after renaming.
real->canInline = false;
sym->canInline = false;
// Tell LTO not to eliminate these symbols.
sym->isUsedInRegularObj = true;
wrap->isUsedInRegularObj = true;
real->isUsedInRegularObj = false;
}
return v;
}
// Do renaming for -wrap by updating pointers to symbols.
//
// When this function is executed, only InputFiles and symbol table
// contain pointers to symbol objects. We visit them to replace pointers,
// so that wrapped symbols are swapped as instructed by the command line.
static void wrapSymbols(ArrayRef<WrappedSymbol> wrapped) {
DenseMap<Symbol *, Symbol *> map;
for (const WrappedSymbol &w : wrapped) {
map[w.sym] = w.wrap;
map[w.real] = w.sym;
}
// Update pointers in input files.
parallelForEach(symtab->objectFiles, [&](InputFile *file) {
MutableArrayRef<Symbol *> syms = file->getMutableSymbols();
for (size_t i = 0, e = syms.size(); i != e; ++i)
if (Symbol *s = map.lookup(syms[i]))
syms[i] = s;
});
// Update pointers in the symbol table.
for (const WrappedSymbol &w : wrapped)
symtab->wrap(w.sym, w.real, w.wrap);
}
static void splitSections() {
// splitIntoPieces needs to be called on each MergeInputChunk
// before calling finalizeContents().
LLVM_DEBUG(llvm::dbgs() << "splitSections\n");
parallelForEach(symtab->objectFiles, [](ObjFile *file) {
for (InputChunk *seg : file->segments) {
if (auto *s = dyn_cast<MergeInputChunk>(seg))
s->splitIntoPieces();
}
for (InputChunk *sec : file->customSections) {
if (auto *s = dyn_cast<MergeInputChunk>(sec))
s->splitIntoPieces();
}
});
}
void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
WasmOptTable parser;
opt::InputArgList args = parser.parse(argsArr.slice(1));
// Handle --help
if (args.hasArg(OPT_help)) {
parser.PrintHelp(lld::outs(),
(std::string(argsArr[0]) + " [options] file...").c_str(),
"LLVM Linker", false);
return;
}
// Handle --version
if (args.hasArg(OPT_version) || args.hasArg(OPT_v)) {
lld::outs() << getLLDVersion() << "\n";
return;
}
// Handle --reproduce
if (auto *arg = args.getLastArg(OPT_reproduce)) {
StringRef path = arg->getValue();
Expected<std::unique_ptr<TarWriter>> errOrWriter =
TarWriter::create(path, path::stem(path));
if (errOrWriter) {
tar = std::move(*errOrWriter);
tar->append("response.txt", createResponseFile(args));
tar->append("version.txt", getLLDVersion() + "\n");
} else {
error("--reproduce: " + toString(errOrWriter.takeError()));
}
}
// Parse and evaluate -mllvm options.
std::vector<const char *> v;
v.push_back("wasm-ld (LLVM option parsing)");
for (auto *arg : args.filtered(OPT_mllvm))
v.push_back(arg->getValue());
cl::ResetAllOptionOccurrences();
cl::ParseCommandLineOptions(v.size(), v.data());
errorHandler().errorLimit = args::getInteger(args, OPT_error_limit, 20);
readConfigs(args);
createFiles(args);
if (errorCount())
return;
setConfigs();
checkOptions(args);
if (errorCount())
return;
if (auto *arg = args.getLastArg(OPT_allow_undefined_file))
readImportFile(arg->getValue());
// Fail early if the output file or map file is not writable. If a user has a
// long link, e.g. due to a large LTO link, they do not wish to run it and
// find that it failed because there was a mistake in their command-line.
if (auto e = tryCreateFile(config->outputFile))
error("cannot open output file " + config->outputFile + ": " + e.message());
if (auto e = tryCreateFile(config->mapFile))
error("cannot open map file " + config->mapFile + ": " + e.message());
if (errorCount())
return;
// Handle --trace-symbol.
for (auto *arg : args.filtered(OPT_trace_symbol))
symtab->trace(arg->getValue());
for (auto *arg : args.filtered(OPT_export_if_defined))
config->exportedSymbols.insert(arg->getValue());
for (auto *arg : args.filtered(OPT_export)) {
config->exportedSymbols.insert(arg->getValue());
config->requiredExports.push_back(arg->getValue());
}
createSyntheticSymbols();
// Add all files to the symbol table. This will add almost all
// symbols that we need to the symbol table.
for (InputFile *f : files)
symtab->addFile(f);
if (errorCount())
return;
// Handle the `--undefined <sym>` options.
for (auto *arg : args.filtered(OPT_undefined))
handleUndefined(arg->getValue());
// Handle the `--export <sym>` options
// This works like --undefined but also exports the symbol if its found
for (auto &iter : config->exportedSymbols)
handleUndefined(iter.first());
Symbol *entrySym = nullptr;
if (!config->relocatable && !config->entry.empty()) {
entrySym = handleUndefined(config->entry);
if (entrySym && entrySym->isDefined())
entrySym->forceExport = true;
else
error("entry symbol not defined (pass --no-entry to suppress): " +
config->entry);
}
// If the user code defines a `__wasm_call_dtors` function, remember it so
// that we can call it from the command export wrappers. Unlike
// `__wasm_call_ctors` which we synthesize, `__wasm_call_dtors` is defined
// by libc/etc., because destructors are registered dynamically with
// `__cxa_atexit` and friends.
if (!config->relocatable && !config->shared &&
!WasmSym::callCtors->isUsedInRegularObj &&
WasmSym::callCtors->getName() != config->entry &&
!config->exportedSymbols.count(WasmSym::callCtors->getName())) {
if (Symbol *callDtors = handleUndefined("__wasm_call_dtors")) {
if (auto *callDtorsFunc = dyn_cast<DefinedFunction>(callDtors)) {
if (callDtorsFunc->signature &&
(!callDtorsFunc->signature->Params.empty() ||
!callDtorsFunc->signature->Returns.empty())) {
error("__wasm_call_dtors must have no argument or return values");
}
WasmSym::callDtors = callDtorsFunc;
} else {
error("__wasm_call_dtors must be a function");
}
}
}
createOptionalSymbols();
if (errorCount())
return;
// Create wrapped symbols for -wrap option.
std::vector<WrappedSymbol> wrapped = addWrappedSymbols(args);
// If any of our inputs are bitcode files, the LTO code generator may create
// references to certain library functions that might not be explicit in the
// bitcode file's symbol table. If any of those library functions are defined
// in a bitcode file in an archive member, we need to arrange to use LTO to
// compile those archive members by adding them to the link beforehand.
//
// We only need to add libcall symbols to the link before LTO if the symbol's
// definition is in bitcode. Any other required libcall symbols will be added
// to the link after LTO when we add the LTO object file to the link.
if (!symtab->bitcodeFiles.empty())
for (auto *s : lto::LTO::getRuntimeLibcallSymbols())
handleLibcall(s);
if (errorCount())
return;
// Do link-time optimization if given files are LLVM bitcode files.
// This compiles bitcode files into real object files.
symtab->addCombinedLTOObject();
if (errorCount())
return;
// Resolve any variant symbols that were created due to signature
// mismatchs.
symtab->handleSymbolVariants();
if (errorCount())
return;
// Apply symbol renames for -wrap.
if (!wrapped.empty())
wrapSymbols(wrapped);
for (auto &iter : config->exportedSymbols) {
Symbol *sym = symtab->find(iter.first());
if (sym && sym->isDefined())
sym->forceExport = true;
}
if (!config->relocatable && !config->isPic) {
// Add synthetic dummies for weak undefined functions. Must happen
// after LTO otherwise functions may not yet have signatures.
symtab->handleWeakUndefines();
}
if (entrySym)
entrySym->setHidden(false);
if (errorCount())
return;
// Split WASM_SEG_FLAG_STRINGS sections into pieces in preparation for garbage
// collection.
splitSections();
// Do size optimizations: garbage collection
markLive();
// Provide the indirect function table if needed.
WasmSym::indirectFunctionTable =
symtab->resolveIndirectFunctionTable(/*required =*/false);
if (errorCount())
return;
// Write the result to the file.
writeResult();
}
} // namespace wasm
} // namespace lld
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