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llvm / llvm-project / lld / refs/heads/master / . / wasm / Driver.cpp
blob: d5d763b0a4ae178c955550c05a6c9591a1668511 [file] [log] [blame]
//===- 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/CommonLinkerContext.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/Parallel.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/TarWriter.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/TargetParser/Host.h"
#include <optional>
#define DEBUG_TYPE "lld"
using namespace llvm;
using namespace llvm::object;
using namespace llvm::opt;
using namespace llvm::sys;
using namespace llvm::wasm;
namespace lld::wasm {
Configuration *config;
Ctx ctx;
void Ctx::reset() {
objectFiles.clear();
stubFiles.clear();
sharedFiles.clear();
bitcodeFiles.clear();
syntheticFunctions.clear();
syntheticGlobals.clear();
syntheticTables.clear();
whyExtractRecords.clear();
isPic = false;
legacyFunctionTable = false;
emitBssSegments = false;
}
namespace {
// Create enum with OPT_xxx values for each option in Options.td
enum {
OPT_INVALID = 0,
#define OPTION(...) LLVM_MAKE_OPT_ID(__VA_ARGS__),
#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;
// True if we are in --start-lib and --end-lib.
bool inLib = false;
std::vector<InputFile *> files;
};
} // anonymous namespace
bool link(ArrayRef<const char *> args, llvm::raw_ostream &stdoutOS,
llvm::raw_ostream &stderrOS, bool exitEarly, bool disableOutput) {
// This driver-specific context will be freed later by unsafeLldMain().
auto *ctx = new CommonLinkerContext;
ctx->e.initialize(stdoutOS, stderrOS, exitEarly, disableOutput);
ctx->e.cleanupCallback = []() { wasm::ctx.reset(); };
ctx->e.logName = args::getFilenameWithoutExe(args[0]);
ctx->e.errorLimitExceededMsg = "too many errors emitted, stopping now (use "
"-error-limit=0 to see all errors)";
config = make<Configuration>();
symtab = make<SymbolTable>();
initLLVM();
LinkerDriver().linkerMain(args);
return errorCount() == 0;
}
// Create prefix string literals used in Options.td
#define PREFIX(NAME, VALUE) \
static constexpr StringLiteral NAME##_init[] = VALUE; \
static constexpr ArrayRef<StringLiteral> NAME(NAME##_init, \
std::size(NAME##_init) - 1);
#include "Options.inc"
#undef PREFIX
// Create table mapping all options defined in Options.td
static constexpr opt::OptTable::Info optInfo[] = {
#define OPTION(PREFIX, NAME, ID, KIND, GROUP, ALIAS, ALIASARGS, FLAGS, \
VISIBILITY, PARAM, HELPTEXT, HELPTEXTSFORVARIANTS, METAVAR, \
VALUES) \
{PREFIX, \
NAME, \
HELPTEXT, \
HELPTEXTSFORVARIANTS, \
METAVAR, \
OPT_##ID, \
opt::Option::KIND##Class, \
PARAM, \
FLAGS, \
VISIBILITY, \
OPT_##GROUP, \
OPT_##ALIAS, \
ALIASARGS, \
VALUES},
#include "Options.inc"
#undef OPTION
};
namespace {
class WasmOptTable : public opt::GenericOptTable {
public:
WasmOptTable() : opt::GenericOptTable(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 std::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 std::nullopt;
}
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);
if (missingCount)
error(Twine(args.getArgString(missingIndex)) + ": missing argument");
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 (std::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<std::pair<MemoryBufferRef, uint64_t>> static getArchiveMembers(
MemoryBufferRef mb) {
std::unique_ptr<Archive> file =
CHECK(Archive::create(mb),
mb.getBufferIdentifier() + ": failed to parse archive");
std::vector<std::pair<MemoryBufferRef, uint64_t>> 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(std::make_pair(mbref, c.getChildOffset()));
}
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) {
std::optional<MemoryBufferRef> buffer = readFile(path);
if (!buffer)
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());
auto members = getArchiveMembers(mbref);
// Handle -whole-archive.
if (inWholeArchive) {
for (const auto &[m, offset] : members) {
auto *object = createObjectFile(m, path, offset);
// 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");
for (const auto &[m, offset] : members) {
auto magic = identify_magic(m.getBuffer());
if (magic == file_magic::wasm_object || magic == file_magic::bitcode)
files.push_back(createObjectFile(m, path, offset, true));
else
warn(path + ": archive member '" + m.getBufferIdentifier() +
"' is neither Wasm object file nor LLVM bitcode");
}
return;
}
case file_magic::bitcode:
case file_magic::wasm_object:
files.push_back(createObjectFile(mbref, "", 0, inLib));
break;
case file_magic::unknown:
if (mbref.getBuffer().starts_with("#STUB")) {
files.push_back(make<StubFile>(mbref));
break;
}
[[fallthrough]];
default:
error("unknown file type: " + mbref.getBufferIdentifier());
}
}
static std::optional<std::string> findFromSearchPaths(StringRef path) {
for (StringRef dir : config->searchPaths)
if (std::optional<std::string> s = findFile(dir, path))
return s;
return std::nullopt;
}
// This is for -l<basename>. We'll look for lib<basename>.a from
// search paths.
static std::optional<std::string> searchLibraryBaseName(StringRef name) {
for (StringRef dir : config->searchPaths) {
// Currently we don't enable dynamic linking at all unless -shared or -pie
// are used, so don't even look for .so files in that case..
if (ctx.isPic && !config->isStatic)
if (std::optional<std::string> s = findFile(dir, "lib" + name + ".so"))
return s;
if (std::optional<std::string> s = findFile(dir, "lib" + name + ".a"))
return s;
}
return std::nullopt;
}
// This is for -l<namespec>.
static std::optional<std::string> searchLibrary(StringRef name) {
if (name.starts_with(":"))
return findFromSearchPaths(name.substr(1));
return searchLibraryBaseName(name);
}
// Add a given library by searching it from input search paths.
void LinkerDriver::addLibrary(StringRef name) {
if (std::optional<std::string> path = searchLibrary(name))
addFile(saver().save(*path));
else
error("unable to find library -l" + name, ErrorTag::LibNotFound, {name});
}
void LinkerDriver::createFiles(opt::InputArgList &args) {
for (auto *arg : args) {
switch (arg->getOption().getID()) {
case OPT_library:
addLibrary(arg->getValue());
break;
case OPT_INPUT:
addFile(arg->getValue());
break;
case OPT_Bstatic:
config->isStatic = true;
break;
case OPT_Bdynamic:
config->isStatic = false;
break;
case OPT_whole_archive:
inWholeArchive = true;
break;
case OPT_no_whole_archive:
inWholeArchive = false;
break;
case OPT_start_lib:
if (inLib)
error("nested --start-lib");
inLib = true;
break;
case OPT_end_lib:
if (!inLib)
error("stray --end-lib");
inLib = 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-dynamic")
return UnresolvedPolicy::ImportDynamic;
if (s == "report-all")
return errorOrWarn;
error("unknown --unresolved-symbols value: " + s);
}
return errorOrWarn;
}
// Parse --build-id or --build-id=<style>. We handle "tree" as a
// synonym for "sha1" because all our hash functions including
// -build-id=sha1 are actually tree hashes for performance reasons.
static std::pair<BuildIdKind, SmallVector<uint8_t, 0>>
getBuildId(opt::InputArgList &args) {
auto *arg = args.getLastArg(OPT_build_id, OPT_build_id_eq);
if (!arg)
return {BuildIdKind::None, {}};
if (arg->getOption().getID() == OPT_build_id)
return {BuildIdKind::Fast, {}};
StringRef s = arg->getValue();
if (s == "fast")
return {BuildIdKind::Fast, {}};
if (s == "sha1" || s == "tree")
return {BuildIdKind::Sha1, {}};
if (s == "uuid")
return {BuildIdKind::Uuid, {}};
if (s.starts_with("0x"))
return {BuildIdKind::Hexstring, parseHex(s.substr(2))};
if (s != "none")
error("unknown --build-id style: " + s);
return {BuildIdKind::None, {}};
}
// 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);
if (args.hasArg(OPT_import_memory_with_name)) {
config->memoryImport =
args.getLastArgValue(OPT_import_memory_with_name).split(",");
} else if (args.hasArg(OPT_import_memory)) {
config->memoryImport =
std::pair<llvm::StringRef, llvm::StringRef>(defaultModule, memoryName);
} else {
config->memoryImport =
std::optional<std::pair<llvm::StringRef, llvm::StringRef>>();
}
if (args.hasArg(OPT_export_memory_with_name)) {
config->memoryExport =
args.getLastArgValue(OPT_export_memory_with_name);
} else if (args.hasArg(OPT_export_memory)) {
config->memoryExport = memoryName;
} else {
config->memoryExport = std::optional<llvm::StringRef>();
}
config->sharedMemory = args.hasArg(OPT_shared_memory);
config->soName = args.getLastArgValue(OPT_soname);
config->importTable = args.hasArg(OPT_import_table);
config->importUndefined = args.hasArg(OPT_import_undefined);
config->ltoo = args::getInteger(args, OPT_lto_O, 2);
if (config->ltoo > 3)
error("invalid optimization level for LTO: " + Twine(config->ltoo));
unsigned ltoCgo =
args::getInteger(args, OPT_lto_CGO, args::getCGOptLevel(config->ltoo));
if (auto level = CodeGenOpt::getLevel(ltoCgo))
config->ltoCgo = *level;
else
error("invalid codegen optimization level for LTO: " + Twine(ltoCgo));
config->ltoPartitions = args::getInteger(args, OPT_lto_partitions, 1);
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);
for (auto *arg : args.filtered(OPT_keep_section))
config->keepSections.insert(arg->getValue());
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_library_path);
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);
config->whyExtract = args.getLastArgValue(OPT_why_extract);
errorHandler().verbose = args.hasArg(OPT_verbose);
LLVM_DEBUG(errorHandler().verbose = true);
config->tableBase = args::getInteger(args, OPT_table_base, 0);
config->globalBase = args::getInteger(args, OPT_global_base, 0);
config->initialHeap = args::getInteger(args, OPT_initial_heap, 0);
config->initialMemory = args::getInteger(args, OPT_initial_memory, 0);
config->maxMemory = args::getInteger(args, OPT_max_memory, 0);
config->noGrowableMemory = args.hasArg(OPT_no_growable_memory);
config->zStackSize =
args::getZOptionValue(args, OPT_z, "stack-size", WasmPageSize);
if (config->maxMemory != 0 && config->noGrowableMemory) {
// Erroring out here is simpler than defining precedence rules.
error("--max-memory is incompatible with --no-growable-memory");
}
// 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 =
std::optional<std::vector<std::string>>(std::vector<std::string>());
for (StringRef s : arg->getValues())
config->features->push_back(std::string(s));
}
if (auto *arg = args.getLastArg(OPT_extra_features)) {
config->extraFeatures =
std::optional<std::vector<std::string>>(std::vector<std::string>());
for (StringRef s : arg->getValues())
config->extraFeatures->push_back(std::string(s));
}
// Legacy --allow-undefined flag which is equivalent to
// --unresolve-symbols=ignore + --import-undefined
if (args.hasArg(OPT_allow_undefined)) {
config->importUndefined = true;
config->unresolvedSymbols = UnresolvedPolicy::Ignore;
}
if (args.hasArg(OPT_print_map))
config->mapFile = "-";
std::tie(config->buildId, config->buildIdVector) = getBuildId(args);
}
// 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() {
ctx.isPic = config->pie || config->shared;
if (ctx.isPic) {
if (config->exportTable)
error("-shared/-pie is incompatible with --export-table");
config->importTable = true;
} else {
// Default table base. Defaults to 1, reserving 0 for the NULL function
// pointer.
if (!config->tableBase)
config->tableBase = 1;
// The default offset for static/global data, for when --global-base is
// not specified on the command line. The precise value of 1024 is
// somewhat arbitrary, and pre-dates wasm-ld (Its the value that
// emscripten used prior to wasm-ld).
if (!config->globalBase && !config->relocatable && !config->stackFirst)
config->globalBase = 1024;
}
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) {
if (config->memoryExport.has_value()) {
error("--export-memory is incompatible with --shared");
}
if (!config->memoryImport.has_value()) {
config->memoryImport =
std::pair<llvm::StringRef, llvm::StringRef>(defaultModule, memoryName);
}
}
// If neither export-memory nor import-memory is specified, default to
// exporting memory under its default name.
if (!config->memoryExport.has_value() && !config->memoryImport.has_value()) {
config->memoryExport = memoryName;
}
}
// 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->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");
if (config->globalBase)
error("-r and --global-base may not by 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->unresolvedSymbols == UnresolvedPolicy::ImportDynamic) {
warn("dynamic imports are not yet stable "
"(--unresolved-symbols=import-dynamic)");
}
}
if (config->bsymbolic && !config->shared) {
warn("-Bsymbolic is only meaningful when combined with -shared");
}
if (ctx.isPic) {
if (config->globalBase)
error("--global-base may not be used with -shared/-pie");
if (config->tableBase)
error("--table-base may not be used with -shared/-pie");
}
}
static const char *getReproduceOption(opt::InputArgList &args) {
if (auto *arg = args.getLastArg(OPT_reproduce))
return arg->getValue();
return getenv("LLD_REPRODUCE");
}
// Force Sym to be entered in the output. Used for -u or equivalent.
static Symbol *handleUndefined(StringRef name, const char *option) {
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->extract();
if (!config->whyExtract.empty())
ctx.whyExtractRecords.emplace_back(option, sym->getFile(), *sym);
}
return sym;
}
static void handleLibcall(StringRef name) {
Symbol *sym = symtab->find(name);
if (sym && sym->isLazy() && isa<BitcodeFile>(sym->getFile())) {
if (!config->whyExtract.empty())
ctx.whyExtractRecords.emplace_back("<libcall>", sym->getFile(), *sym);
cast<LazySymbol>(sym)->extract();
}
}
static void writeWhyExtract() {
if (config->whyExtract.empty())
return;
std::error_code ec;
raw_fd_ostream os(config->whyExtract, ec, sys::fs::OF_None);
if (ec) {
error("cannot open --why-extract= file " + config->whyExtract + ": " +
ec.message());
return;
}
os << "reference\textracted\tsymbol\n";
for (auto &entry : ctx.whyExtractRecords) {
os << std::get<0>(entry) << '\t' << toString(std::get<1>(entry)) << '\t'
<< toString(std::get<2>(entry)) << '\n';
}
}
// Equivalent of demote demoteSharedAndLazySymbols() in the ELF linker
static void demoteLazySymbols() {
for (Symbol *sym : symtab->symbols()) {
if (auto* s = dyn_cast<LazySymbol>(sym)) {
if (s->signature) {
LLVM_DEBUG(llvm::dbgs()
<< "demoting lazy func: " << s->getName() << "\n");
replaceSymbol<UndefinedFunction>(s, s->getName(), std::nullopt,
std::nullopt, WASM_SYMBOL_BINDING_WEAK,
s->getFile(), s->signature);
}
}
}
}
static UndefinedGlobal *
createUndefinedGlobal(StringRef name, llvm::wasm::WasmGlobalType *type) {
auto *sym = cast<UndefinedGlobal>(symtab->addUndefinedGlobal(
name, std::nullopt, std::nullopt, 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.value_or(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"));
bool is64 = config->is64.value_or(false);
if (ctx.isPic) {
WasmSym::stackPointer =
createUndefinedGlobal("__stack_pointer", config->is64.value_or(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/main/DynamicLinking.md
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) {
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>(
is64 ? i64ArgSignature : i32ArgSignature,
"__wasm_init_tls"));
}
if (ctx.isPic ||
config->unresolvedSymbols == UnresolvedPolicy::ImportDynamic) {
// For PIC code, or when dynamically importing addresses, we create
// synthetic functions that apply relocations. These get called from
// __wasm_call_ctors before the user-level constructors.
WasmSym::applyDataRelocs = symtab->addSyntheticFunction(
"__wasm_apply_data_relocs",
WASM_SYMBOL_VISIBILITY_DEFAULT | WASM_SYMBOL_EXPORTED,
make<SyntheticFunction>(nullSignature, "__wasm_apply_data_relocs"));
}
}
static void createOptionalSymbols() {
if (config->relocatable)
return;
WasmSym::dsoHandle = symtab->addOptionalDataSymbol("__dso_handle");
if (!config->shared)
WasmSym::dataEnd = symtab->addOptionalDataSymbol("__data_end");
if (!ctx.isPic) {
WasmSym::stackLow = symtab->addOptionalDataSymbol("__stack_low");
WasmSym::stackHigh = symtab->addOptionalDataSymbol("__stack_high");
WasmSym::globalBase = symtab->addOptionalDataSymbol("__global_base");
WasmSym::heapBase = symtab->addOptionalDataSymbol("__heap_base");
WasmSym::heapEnd = symtab->addOptionalDataSymbol("__heap_end");
WasmSym::definedMemoryBase = symtab->addOptionalDataSymbol("__memory_base");
WasmSym::definedTableBase = symtab->addOptionalDataSymbol("__table_base");
if (config->is64.value_or(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 contain references 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);
}
static void processStubLibrariesPreLTO() {
log("-- processStubLibrariesPreLTO");
for (auto &stub_file : ctx.stubFiles) {
LLVM_DEBUG(llvm::dbgs()
<< "processing stub file: " << stub_file->getName() << "\n");
for (auto [name, deps]: stub_file->symbolDependencies) {
auto* sym = symtab->find(name);
// If the symbol is not present at all (yet), or if it is present but
// undefined, then mark the dependent symbols as used by a regular
// object so they will be preserved and exported by the LTO process.
if (!sym || sym->isUndefined()) {
for (const auto dep : deps) {
auto* needed = symtab->find(dep);
if (needed ) {
needed->isUsedInRegularObj = true;
}
}
}
}
}
}
static void processStubLibraries() {
log("-- processStubLibraries");
bool depsAdded = false;
do {
depsAdded = false;
for (auto &stub_file : ctx.stubFiles) {
LLVM_DEBUG(llvm::dbgs()
<< "processing stub file: " << stub_file->getName() << "\n");
for (auto [name, deps]: stub_file->symbolDependencies) {
auto* sym = symtab->find(name);
if (!sym || !sym->isUndefined()) {
if (sym && sym->traced)
message(toString(stub_file) + ": stub symbol not needed: " + name);
else
LLVM_DEBUG(llvm::dbgs() << "stub symbol not needed: `" << name << "`\n");
continue;
}
// The first stub library to define a given symbol sets this and
// definitions in later stub libraries are ignored.
if (sym->forceImport)
continue; // Already handled
sym->forceImport = true;
if (sym->traced)
message(toString(stub_file) + ": importing " + name);
else
LLVM_DEBUG(llvm::dbgs()
<< toString(stub_file) << ": importing " << name << "\n");
for (const auto dep : deps) {
auto* needed = symtab->find(dep);
if (!needed) {
error(toString(stub_file) + ": undefined symbol: " + dep +
". Required by " + toString(*sym));
} else if (needed->isUndefined()) {
error(toString(stub_file) +
": undefined symbol: " + toString(*needed) +
". Required by " + toString(*sym));
} else {
if (needed->traced)
message(toString(stub_file) + ": exported " + toString(*needed) +
" due to import of " + name);
else
LLVM_DEBUG(llvm::dbgs()
<< "force export: " << toString(*needed) << "\n");
needed->forceExport = true;
if (auto *lazy = dyn_cast<LazySymbol>(needed)) {
depsAdded = true;
lazy->extract();
if (!config->whyExtract.empty())
ctx.whyExtractRecords.emplace_back(stub_file->getName(),
sym->getFile(), *sym);
}
}
}
}
}
} while (depsAdded);
log("-- done processStubLibraries");
}
// 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);
}
// 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, std::nullopt, std::nullopt,
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(ctx.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(ctx.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();
}
});
}
static bool isKnownZFlag(StringRef s) {
// For now, we only support a very limited set of -z flags
return s.starts_with("stack-size=");
}
// Report a warning for an unknown -z option.
static void checkZOptions(opt::InputArgList &args) {
for (auto *arg : args.filtered(OPT_z))
if (!isKnownZFlag(arg->getValue()))
warn("unknown -z value: " + StringRef(arg->getValue()));
}
void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
WasmOptTable parser;
opt::InputArgList args = parser.parse(argsArr.slice(1));
// Interpret these flags early because error()/warn() depend on them.
errorHandler().errorLimit = args::getInteger(args, OPT_error_limit, 20);
errorHandler().fatalWarnings =
args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false);
checkZOptions(args);
// 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 (const char *path = getReproduceOption(args)) {
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());
readConfigs(args);
setConfigs();
createFiles(args);
if (errorCount())
return;
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(), "<internal>");
// 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(), "--export");
Symbol *entrySym = nullptr;
if (!config->relocatable && !config->entry.empty()) {
entrySym = handleUndefined(config->entry, "--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", "<internal>")) {
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");
}
}
}
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 (!ctx.bitcodeFiles.empty())
for (auto *s : lto::LTO::getRuntimeLibcallSymbols())
handleLibcall(s);
if (errorCount())
return;
// We process the stub libraries once beofore LTO to ensure that any possible
// required exports are preserved by the LTO process.
processStubLibrariesPreLTO();
// Do link-time optimization if given files are LLVM bitcode files.
// This compiles bitcode files into real object files.
symtab->compileBitcodeFiles();
if (errorCount())
return;
// The LTO process can generate new undefined symbols, specifically libcall
// functions. Because those symbols might be declared in a stub library we
// need the process the stub libraries once again after LTO to handle all
// undefined symbols, including ones that didn't exist prior to LTO.
processStubLibraries();
writeWhyExtract();
createOptionalSymbols();
// 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 && !ctx.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();
// Any remaining lazy symbols should be demoted to Undefined
demoteLazySymbols();
// 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 lld::wasm