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llvm-project/lld/ELF/Driver.cpp

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//===- Driver.cpp ---------------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// The driver drives the entire linking process. It is responsible for
// parsing command line options and doing whatever it is instructed to do.
//
// One notable thing in the LLD's driver when compared to other linkers is
// that the LLD's driver is agnostic on the host operating system.
// Other linkers usually have implicit default values (such as a dynamic
// linker path or library paths) for each host OS.
//
// I don't think implicit default values are useful because they are
// usually explicitly specified by the compiler driver. They can even
// be harmful when you are doing cross-linking. Therefore, in LLD, we
// simply trust the compiler driver to pass all required options and
// don't try to make effort on our side.
//
//===----------------------------------------------------------------------===//
#include "Driver.h"
#include "Config.h"
#include "Filesystem.h"
#include "ICF.h"
#include "InputFiles.h"
#include "InputSection.h"
#include "LinkerScript.h"
#include "OutputSections.h"
#include "ScriptParser.h"
#include "Strings.h"
#include "SymbolTable.h"
#include "Symbols.h"
#include "SyntheticSections.h"
#include "Target.h"
#include "Writer.h"
#include "lld/Common/Args.h"
#include "lld/Common/Driver.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/Memory.h"
#include "lld/Common/Threads.h"
#include "lld/Common/Version.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compression.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/TarWriter.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/raw_ostream.h"
#include <cstdlib>
#include <utility>
using namespace llvm;
using namespace llvm::ELF;
using namespace llvm::object;
using namespace llvm::sys;
using namespace lld;
using namespace lld::elf;
Configuration *elf::Config;
LinkerDriver *elf::Driver;
static void setConfigs();
bool elf::link(ArrayRef<const char *> Args, bool CanExitEarly,
raw_ostream &Error) {
errorHandler().LogName = Args[0];
errorHandler().ErrorLimitExceededMsg =
"too many errors emitted, stopping now (use "
"-error-limit=0 to see all errors)";
errorHandler().ErrorOS = &Error;
errorHandler().ColorDiagnostics = Error.has_colors();
InputSections.clear();
OutputSections.clear();
Tar = nullptr;
BinaryFiles.clear();
BitcodeFiles.clear();
ObjectFiles.clear();
SharedFiles.clear();
Config = make<Configuration>();
Driver = make<LinkerDriver>();
Script = make<LinkerScript>();
Symtab = make<SymbolTable>();
Config->Argv = {Args.begin(), Args.end()};
Driver->main(Args, CanExitEarly);
// 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 (Config->ExitEarly)
exitLld(errorCount() ? 1 : 0);
freeArena();
return !errorCount();
}
// Parses a linker -m option.
static std::tuple<ELFKind, uint16_t, uint8_t> parseEmulation(StringRef Emul) {
uint8_t OSABI = 0;
StringRef S = Emul;
if (S.endswith("_fbsd")) {
S = S.drop_back(5);
OSABI = ELFOSABI_FREEBSD;
}
std::pair<ELFKind, uint16_t> Ret =
StringSwitch<std::pair<ELFKind, uint16_t>>(S)
.Cases("aarch64elf", "aarch64linux", {ELF64LEKind, EM_AARCH64})
.Cases("armelf", "armelf_linux_eabi", {ELF32LEKind, EM_ARM})
.Case("elf32_x86_64", {ELF32LEKind, EM_X86_64})
.Cases("elf32btsmip", "elf32btsmipn32", {ELF32BEKind, EM_MIPS})
.Cases("elf32ltsmip", "elf32ltsmipn32", {ELF32LEKind, EM_MIPS})
.Case("elf32ppc", {ELF32BEKind, EM_PPC})
.Case("elf64btsmip", {ELF64BEKind, EM_MIPS})
.Case("elf64ltsmip", {ELF64LEKind, EM_MIPS})
.Case("elf64ppc", {ELF64BEKind, EM_PPC64})
.Cases("elf_amd64", "elf_x86_64", {ELF64LEKind, EM_X86_64})
.Case("elf_i386", {ELF32LEKind, EM_386})
.Case("elf_iamcu", {ELF32LEKind, EM_IAMCU})
.Default({ELFNoneKind, EM_NONE});
if (Ret.first == ELFNoneKind)
error("unknown emulation: " + Emul);
return std::make_tuple(Ret.first, Ret.second, OSABI);
}
// 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();
bool AddToTar = File->isThin() && Tar;
for (const ErrorOr<Archive::Child> &COrErr : File->children(Err)) {
Archive::Child C =
CHECK(COrErr, MB.getBufferIdentifier() +
": could not get the child of the archive");
MemoryBufferRef MBRef =
CHECK(C.getMemoryBufferRef(),
MB.getBufferIdentifier() +
": could not get the buffer for a child of the archive");
if (AddToTar)
Tar->append(relativeToRoot(check(C.getFullName())), MBRef.getBuffer());
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;
}
// Opens a file and create a file object. Path has to be resolved already.
void LinkerDriver::addFile(StringRef Path, bool WithLOption) {
using namespace sys::fs;
Optional<MemoryBufferRef> Buffer = readFile(Path);
if (!Buffer.hasValue())
return;
MemoryBufferRef MBRef = *Buffer;
if (InBinary) {
Files.push_back(make<BinaryFile>(MBRef));
return;
}
switch (identify_magic(MBRef.getBuffer())) {
case file_magic::unknown:
readLinkerScript(MBRef);
return;
case file_magic::archive: {
// Handle -whole-archive.
if (InWholeArchive) {
for (const auto &P : getArchiveMembers(MBRef))
Files.push_back(createObjectFile(P.first, Path, P.second));
return;
}
std::unique_ptr<Archive> File =
CHECK(Archive::create(MBRef), Path + ": failed to parse archive");
// If an archive file has no symbol table, it is likely that a user
// is attempting LTO and using a default ar command that doesn't
// understand the LLVM bitcode file. It is a pretty common error, so
// we'll handle it as if it had a symbol table.
if (!File->isEmpty() && !File->hasSymbolTable()) {
for (const auto &P : getArchiveMembers(MBRef))
Files.push_back(make<LazyObjFile>(P.first, Path, P.second));
return;
}
// Handle the regular case.
Files.push_back(make<ArchiveFile>(std::move(File)));
return;
}
case file_magic::elf_shared_object:
if (Config->Relocatable) {
error("attempted static link of dynamic object " + Path);
return;
}
// DSOs usually have DT_SONAME tags in their ELF headers, and the
// sonames are used to identify DSOs. But if they are missing,
// they are identified by filenames. We don't know whether the new
// file has a DT_SONAME or not because we haven't parsed it yet.
// Here, we set the default soname for the file because we might
// need it later.
//
// If a file was specified by -lfoo, the directory part is not
// significant, as a user did not specify it. This behavior is
// compatible with GNU.
Files.push_back(
createSharedFile(MBRef, WithLOption ? path::filename(Path) : Path));
return;
default:
if (InLib)
Files.push_back(make<LazyObjFile>(MBRef, "", 0));
else
Files.push_back(createObjectFile(MBRef));
}
}
// Add a given library by searching it from input search paths.
void LinkerDriver::addLibrary(StringRef Name) {
if (Optional<std::string> Path = searchLibrary(Name))
addFile(*Path, /*WithLOption=*/true);
else
error("unable to find library -l" + Name);
}
// 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(opt::InputArgList &Args) {
InitializeAllTargets();
InitializeAllTargetMCs();
InitializeAllAsmPrinters();
InitializeAllAsmParsers();
// Parse and evaluate -mllvm options.
std::vector<const char *> V;
V.push_back("lld (LLVM option parsing)");
for (auto *Arg : Args.filtered(OPT_mllvm))
V.push_back(Arg->getValue());
cl::ParseCommandLineOptions(V.size(), V.data());
}
// Some command line options or some combinations of them are not allowed.
// This function checks for such errors.
static void checkOptions(opt::InputArgList &Args) {
// The MIPS ABI as of 2016 does not support the GNU-style symbol lookup
// table which is a relatively new feature.
if (Config->EMachine == EM_MIPS && Config->GnuHash)
error("the .gnu.hash section is not compatible with the MIPS target.");
if (Config->FixCortexA53Errata843419 && Config->EMachine != EM_AARCH64)
error("--fix-cortex-a53-843419 is only supported on AArch64 targets.");
if (Config->Pie && Config->Shared)
error("-shared and -pie may not be used together");
if (!Config->Shared && !Config->FilterList.empty())
error("-F may not be used without -shared");
if (!Config->Shared && !Config->AuxiliaryList.empty())
error("-f may not be used without -shared");
if (!Config->Relocatable && !Config->DefineCommon)
error("-no-define-common not supported in non relocatable output");
if (Config->Relocatable) {
if (Config->Shared)
error("-r and -shared may not be used together");
if (Config->GcSections)
error("-r and --gc-sections may not be used together");
if (Config->ICF)
error("-r and --icf may not be used together");
if (Config->Pie)
error("-r and -pie may not be used together");
}
}
static const char *getReproduceOption(opt::InputArgList &Args) {
if (auto *Arg = Args.getLastArg(OPT_reproduce))
return Arg->getValue();
return getenv("LLD_REPRODUCE");
}
static bool hasZOption(opt::InputArgList &Args, StringRef Key) {
for (auto *Arg : Args.filtered(OPT_z))
if (Key == Arg->getValue())
return true;
return false;
}
void LinkerDriver::main(ArrayRef<const char *> ArgsArr, bool CanExitEarly) {
ELFOptTable Parser;
opt::InputArgList Args = Parser.parse(ArgsArr.slice(1));
// Interpret this flag early because error() depends on them.
errorHandler().ErrorLimit = args::getInteger(Args, OPT_error_limit, 20);
// Handle -help
if (Args.hasArg(OPT_help)) {
printHelp(ArgsArr[0]);
return;
}
// Handle -v or -version.
//
// A note about "compatible with GNU linkers" message: this is a hack for
// scripts generated by GNU Libtool 2.4.6 (released in February 2014 and
// still the newest version in March 2017) or earlier to recognize LLD as
// a GNU compatible linker. As long as an output for the -v option
// contains "GNU" or "with BFD", they recognize us as GNU-compatible.
//
// This is somewhat ugly hack, but in reality, we had no choice other
// than doing this. Considering the very long release cycle of Libtool,
// it is not easy to improve it to recognize LLD as a GNU compatible
// linker in a timely manner. Even if we can make it, there are still a
// lot of "configure" scripts out there that are generated by old version
// of Libtool. We cannot convince every software developer to migrate to
// the latest version and re-generate scripts. So we have this hack.
if (Args.hasArg(OPT_v) || Args.hasArg(OPT_version))
message(getLLDVersion() + " (compatible with GNU linkers)");
// The behavior of -v or --version is a bit strange, but this is
// needed for compatibility with GNU linkers.
if (Args.hasArg(OPT_v) && !Args.hasArg(OPT_INPUT))
return;
if (Args.hasArg(OPT_version))
return;
Config->ExitEarly = CanExitEarly && !Args.hasArg(OPT_full_shutdown);
errorHandler().ExitEarly = Config->ExitEarly;
if (const char *Path = getReproduceOption(Args)) {
// Note that --reproduce is a debug option so you can ignore it
// if you are trying to understand the whole picture of the code.
Expected<std::unique_ptr<TarWriter>> ErrOrWriter =
TarWriter::create(Path, path::stem(Path));
if (ErrOrWriter) {
Tar = ErrOrWriter->get();
Tar->append("response.txt", createResponseFile(Args));
Tar->append("version.txt", getLLDVersion() + "\n");
make<std::unique_ptr<TarWriter>>(std::move(*ErrOrWriter));
} else {
error(Twine("--reproduce: failed to open ") + Path + ": " +
toString(ErrOrWriter.takeError()));
}
}
readConfigs(Args);
initLLVM(Args);
createFiles(Args);
inferMachineType();
setConfigs();
checkOptions(Args);
if (errorCount())
return;
switch (Config->EKind) {
case ELF32LEKind:
link<ELF32LE>(Args);
return;
case ELF32BEKind:
link<ELF32BE>(Args);
return;
case ELF64LEKind:
link<ELF64LE>(Args);
return;
case ELF64BEKind:
link<ELF64BE>(Args);
return;
default:
llvm_unreachable("unknown Config->EKind");
}
}
static std::string getRpath(opt::InputArgList &Args) {
std::vector<StringRef> V = args::getStrings(Args, OPT_rpath);
return llvm::join(V.begin(), V.end(), ":");
}
// Determines what we should do if there are remaining unresolved
// symbols after the name resolution.
static UnresolvedPolicy getUnresolvedSymbolPolicy(opt::InputArgList &Args) {
if (Args.hasArg(OPT_relocatable))
return UnresolvedPolicy::IgnoreAll;
UnresolvedPolicy ErrorOrWarn = Args.hasFlag(OPT_error_unresolved_symbols,
OPT_warn_unresolved_symbols, true)
? UnresolvedPolicy::ReportError
: UnresolvedPolicy::Warn;
// Process the last of -unresolved-symbols, -no-undefined or -z defs.
for (auto *Arg : llvm::reverse(Args)) {
switch (Arg->getOption().getID()) {
case OPT_unresolved_symbols: {
StringRef S = Arg->getValue();
if (S == "ignore-all" || S == "ignore-in-object-files")
return UnresolvedPolicy::Ignore;
if (S == "ignore-in-shared-libs" || S == "report-all")
return ErrorOrWarn;
error("unknown --unresolved-symbols value: " + S);
continue;
}
case OPT_no_undefined:
return ErrorOrWarn;
case OPT_z:
if (StringRef(Arg->getValue()) == "defs")
return ErrorOrWarn;
continue;
}
}
// -shared implies -unresolved-symbols=ignore-all because missing
// symbols are likely to be resolved at runtime using other DSOs.
if (Config->Shared)
return UnresolvedPolicy::Ignore;
return ErrorOrWarn;
}
static Target2Policy getTarget2(opt::InputArgList &Args) {
StringRef S = Args.getLastArgValue(OPT_target2, "got-rel");
if (S == "rel")
return Target2Policy::Rel;
if (S == "abs")
return Target2Policy::Abs;
if (S == "got-rel")
return Target2Policy::GotRel;
error("unknown --target2 option: " + S);
return Target2Policy::GotRel;
}
static bool isOutputFormatBinary(opt::InputArgList &Args) {
if (auto *Arg = Args.getLastArg(OPT_oformat)) {
StringRef S = Arg->getValue();
if (S == "binary")
return true;
error("unknown --oformat value: " + S);
}
return false;
}
static DiscardPolicy getDiscard(opt::InputArgList &Args) {
if (Args.hasArg(OPT_relocatable))
return DiscardPolicy::None;
auto *Arg =
Args.getLastArg(OPT_discard_all, OPT_discard_locals, OPT_discard_none);
if (!Arg)
return DiscardPolicy::Default;
if (Arg->getOption().getID() == OPT_discard_all)
return DiscardPolicy::All;
if (Arg->getOption().getID() == OPT_discard_locals)
return DiscardPolicy::Locals;
return DiscardPolicy::None;
}
static StringRef getDynamicLinker(opt::InputArgList &Args) {
auto *Arg = Args.getLastArg(OPT_dynamic_linker, OPT_no_dynamic_linker);
if (!Arg || Arg->getOption().getID() == OPT_no_dynamic_linker)
return "";
return Arg->getValue();
}
static StripPolicy getStrip(opt::InputArgList &Args) {
if (Args.hasArg(OPT_relocatable))
return StripPolicy::None;
auto *Arg = Args.getLastArg(OPT_strip_all, OPT_strip_debug);
if (!Arg)
return StripPolicy::None;
if (Arg->getOption().getID() == OPT_strip_all)
return StripPolicy::All;
return StripPolicy::Debug;
}
static uint64_t parseSectionAddress(StringRef S, const opt::Arg &Arg) {
uint64_t VA = 0;
if (S.startswith("0x"))
S = S.drop_front(2);
if (!to_integer(S, VA, 16))
error("invalid argument: " + toString(Arg));
return VA;
}
static StringMap<uint64_t> getSectionStartMap(opt::InputArgList &Args) {
StringMap<uint64_t> Ret;
for (auto *Arg : Args.filtered(OPT_section_start)) {
StringRef Name;
StringRef Addr;
std::tie(Name, Addr) = StringRef(Arg->getValue()).split('=');
Ret[Name] = parseSectionAddress(Addr, *Arg);
}
if (auto *Arg = Args.getLastArg(OPT_Ttext))
Ret[".text"] = parseSectionAddress(Arg->getValue(), *Arg);
if (auto *Arg = Args.getLastArg(OPT_Tdata))
Ret[".data"] = parseSectionAddress(Arg->getValue(), *Arg);
if (auto *Arg = Args.getLastArg(OPT_Tbss))
Ret[".bss"] = parseSectionAddress(Arg->getValue(), *Arg);
return Ret;
}
static SortSectionPolicy getSortSection(opt::InputArgList &Args) {
StringRef S = Args.getLastArgValue(OPT_sort_section);
if (S == "alignment")
return SortSectionPolicy::Alignment;
if (S == "name")
return SortSectionPolicy::Name;
if (!S.empty())
error("unknown --sort-section rule: " + S);
return SortSectionPolicy::Default;
}
static OrphanHandlingPolicy getOrphanHandling(opt::InputArgList &Args) {
StringRef S = Args.getLastArgValue(OPT_orphan_handling, "place");
if (S == "warn")
return OrphanHandlingPolicy::Warn;
if (S == "error")
return OrphanHandlingPolicy::Error;
if (S != "place")
error("unknown --orphan-handling mode: " + S);
return OrphanHandlingPolicy::Place;
}
// 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, std::vector<uint8_t>>
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 == "md5")
return {BuildIdKind::Md5, {}};
if (S == "sha1" || S == "tree")
return {BuildIdKind::Sha1, {}};
if (S == "uuid")
return {BuildIdKind::Uuid, {}};
if (S.startswith("0x"))
return {BuildIdKind::Hexstring, parseHex(S.substr(2))};
if (S != "none")
error("unknown --build-id style: " + S);
return {BuildIdKind::None, {}};
}
static bool getCompressDebugSections(opt::InputArgList &Args) {
StringRef S = Args.getLastArgValue(OPT_compress_debug_sections, "none");
if (S == "none")
return false;
if (S != "zlib")
error("unknown --compress-debug-sections value: " + S);
if (!zlib::isAvailable())
error("--compress-debug-sections: zlib is not available");
return true;
}
static int parseInt(StringRef S, opt::Arg *Arg) {
int V = 0;
if (!to_integer(S, V, 10))
error(Arg->getSpelling() + ": number expected, but got '" + S + "'");
return V;
}
// Initializes Config members by the command line options.
void LinkerDriver::readConfigs(opt::InputArgList &Args) {
Config->AllowMultipleDefinition =
Args.hasArg(OPT_allow_multiple_definition) || hasZOption(Args, "muldefs");
Config->AuxiliaryList = args::getStrings(Args, OPT_auxiliary);
Config->Bsymbolic = Args.hasArg(OPT_Bsymbolic);
Config->BsymbolicFunctions = Args.hasArg(OPT_Bsymbolic_functions);
Config->Chroot = Args.getLastArgValue(OPT_chroot);
Config->CompressDebugSections = getCompressDebugSections(Args);
Config->DefineCommon = Args.hasFlag(OPT_define_common, OPT_no_define_common,
!Args.hasArg(OPT_relocatable));
Config->Demangle = Args.hasFlag(OPT_demangle, OPT_no_demangle, true);
Config->DisableVerify = Args.hasArg(OPT_disable_verify);
Config->Discard = getDiscard(Args);
Config->DynamicLinker = getDynamicLinker(Args);
Config->EhFrameHdr =
Args.hasFlag(OPT_eh_frame_hdr, OPT_no_eh_frame_hdr, false);
Config->EmitRelocs = Args.hasArg(OPT_emit_relocs);
Config->EnableNewDtags = !Args.hasArg(OPT_disable_new_dtags);
Config->Entry = Args.getLastArgValue(OPT_entry);
Config->ExportDynamic =
Args.hasFlag(OPT_export_dynamic, OPT_no_export_dynamic, false);
errorHandler().FatalWarnings =
Args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false);
Config->FilterList = args::getStrings(Args, OPT_filter);
Config->Fini = Args.getLastArgValue(OPT_fini, "_fini");
Config->FixCortexA53Errata843419 = Args.hasArg(OPT_fix_cortex_a53_843419);
Config->GcSections = Args.hasFlag(OPT_gc_sections, OPT_no_gc_sections, false);
Config->GdbIndex = Args.hasFlag(OPT_gdb_index, OPT_no_gdb_index, false);
Config->ICF = Args.hasFlag(OPT_icf_all, OPT_icf_none, false);
Config->ICFData = Args.hasArg(OPT_icf_data);
Config->Init = Args.getLastArgValue(OPT_init, "_init");
Config->LTOAAPipeline = Args.getLastArgValue(OPT_lto_aa_pipeline);
Config->LTONewPmPasses = Args.getLastArgValue(OPT_lto_newpm_passes);
Config->LTOO = args::getInteger(Args, OPT_lto_O, 2);
Config->LTOPartitions = args::getInteger(Args, OPT_lto_partitions, 1);
Config->MapFile = Args.getLastArgValue(OPT_Map);
Config->NoGnuUnique = Args.hasArg(OPT_no_gnu_unique);
Config->MergeArmExidx =
Args.hasFlag(OPT_merge_exidx_entries, OPT_no_merge_exidx_entries, true);
Config->NoUndefinedVersion = Args.hasArg(OPT_no_undefined_version);
Config->NoinhibitExec = Args.hasArg(OPT_noinhibit_exec);
Config->Nostdlib = Args.hasArg(OPT_nostdlib);
Config->OFormatBinary = isOutputFormatBinary(Args);
Config->Omagic = Args.hasFlag(OPT_omagic, OPT_no_omagic, false);
Config->OptRemarksFilename = Args.getLastArgValue(OPT_opt_remarks_filename);
Config->OptRemarksWithHotness = Args.hasArg(OPT_opt_remarks_with_hotness);
Config->Optimize = args::getInteger(Args, OPT_O, 1);
Config->OrphanHandling = getOrphanHandling(Args);
Config->OutputFile = Args.getLastArgValue(OPT_o);
Config->Pie = Args.hasFlag(OPT_pie, OPT_nopie, false);
Config->PrintGcSections =
Args.hasFlag(OPT_print_gc_sections, OPT_no_print_gc_sections, false);
Config->Rpath = getRpath(Args);
Config->Relocatable = Args.hasArg(OPT_relocatable);
Config->SaveTemps = Args.hasArg(OPT_save_temps);
Config->SearchPaths = args::getStrings(Args, OPT_library_path);
Config->SectionStartMap = getSectionStartMap(Args);
Config->Shared = Args.hasArg(OPT_shared);
Config->SingleRoRx = Args.hasArg(OPT_no_rosegment);
Config->SoName = Args.getLastArgValue(OPT_soname);
Config->SortSection = getSortSection(Args);
Config->Strip = getStrip(Args);
Config->Sysroot = Args.getLastArgValue(OPT_sysroot);
Config->Target1Rel = Args.hasFlag(OPT_target1_rel, OPT_target1_abs, false);
Config->Target2 = getTarget2(Args);
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->ThinLTOJobs = args::getInteger(Args, OPT_thinlto_jobs, -1u);
ThreadsEnabled = Args.hasFlag(OPT_threads, OPT_no_threads, true);
Config->Trace = Args.hasArg(OPT_trace);
Config->Undefined = args::getStrings(Args, OPT_undefined);
Config->UnresolvedSymbols = getUnresolvedSymbolPolicy(Args);
Config->Verbose = Args.hasArg(OPT_verbose);
errorHandler().Verbose = Config->Verbose;
Config->WarnCommon = Args.hasArg(OPT_warn_common);
Config->ZCombreloc = !hasZOption(Args, "nocombreloc");
Config->ZExecstack = hasZOption(Args, "execstack");
Config->ZNocopyreloc = hasZOption(Args, "nocopyreloc");
Config->ZNodelete = hasZOption(Args, "nodelete");
Config->ZNodlopen = hasZOption(Args, "nodlopen");
Config->ZNow = hasZOption(Args, "now");
Config->ZOrigin = hasZOption(Args, "origin");
Config->ZRelro = !hasZOption(Args, "norelro");
Config->ZRodynamic = hasZOption(Args, "rodynamic");
Config->ZStackSize = args::getZOptionValue(Args, OPT_z, "stack-size", 0);
Config->ZText = !hasZOption(Args, "notext");
Config->ZWxneeded = hasZOption(Args, "wxneeded");
// Parse LTO plugin-related options for compatibility with gold.
for (auto *Arg : Args.filtered(OPT_plugin_opt, OPT_plugin_opt_eq)) {
StringRef S = Arg->getValue();
if (S == "disable-verify")
Config->DisableVerify = true;
else if (S == "save-temps")
Config->SaveTemps = true;
else if (S.startswith("O"))
Config->LTOO = parseInt(S.substr(1), Arg);
else if (S.startswith("lto-partitions="))
Config->LTOPartitions = parseInt(S.substr(15), Arg);
else if (S.startswith("jobs="))
Config->ThinLTOJobs = parseInt(S.substr(5), Arg);
else if (!S.startswith("/") && !S.startswith("-fresolution=") &&
!S.startswith("-pass-through=") && !S.startswith("mcpu=") &&
!S.startswith("thinlto") && S != "-function-sections" &&
S != "-data-sections")
error(Arg->getSpelling() + ": unknown option: " + S);
}
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 (Config->ThinLTOJobs == 0)
error("--thinlto-jobs: number of threads must be > 0");
// Parse ELF{32,64}{LE,BE} and CPU type.
if (auto *Arg = Args.getLastArg(OPT_m)) {
StringRef S = Arg->getValue();
std::tie(Config->EKind, Config->EMachine, Config->OSABI) =
parseEmulation(S);
Config->MipsN32Abi = (S == "elf32btsmipn32" || S == "elf32ltsmipn32");
Config->Emulation = S;
}
// Parse -hash-style={sysv,gnu,both}.
if (auto *Arg = Args.getLastArg(OPT_hash_style)) {
StringRef S = Arg->getValue();
if (S == "sysv")
Config->SysvHash = true;
else if (S == "gnu")
Config->GnuHash = true;
else if (S == "both")
Config->SysvHash = Config->GnuHash = true;
else
error("unknown -hash-style: " + S);
}
if (Args.hasArg(OPT_print_map))
Config->MapFile = "-";
// --omagic is an option to create old-fashioned executables in which
// .text segments are writable. Today, the option is still in use to
// create special-purpose programs such as boot loaders. It doesn't
// make sense to create PT_GNU_RELRO for such executables.
if (Config->Omagic)
Config->ZRelro = false;
std::tie(Config->BuildId, Config->BuildIdVector) = getBuildId(Args);
if (auto *Arg = Args.getLastArg(OPT_pack_dyn_relocs_eq)) {
StringRef S = Arg->getValue();
if (S == "android")
Config->AndroidPackDynRelocs = true;
else if (S != "none")
error("unknown -pack-dyn-relocs format: " + S);
}
if (auto *Arg = Args.getLastArg(OPT_symbol_ordering_file))
if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
Config->SymbolOrderingFile = args::getLines(*Buffer);
// If --retain-symbol-file is used, we'll keep only the symbols listed in
// the file and discard all others.
if (auto *Arg = Args.getLastArg(OPT_retain_symbols_file)) {
Config->DefaultSymbolVersion = VER_NDX_LOCAL;
if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
for (StringRef S : args::getLines(*Buffer))
Config->VersionScriptGlobals.push_back(
{S, /*IsExternCpp*/ false, /*HasWildcard*/ false});
}
bool HasExportDynamic =
Args.hasFlag(OPT_export_dynamic, OPT_no_export_dynamic, false);
// Parses -dynamic-list and -export-dynamic-symbol. They make some
// symbols private. Note that -export-dynamic takes precedence over them
// as it says all symbols should be exported.
if (!HasExportDynamic) {
for (auto *Arg : Args.filtered(OPT_dynamic_list))
if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
readDynamicList(*Buffer);
for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol))
Config->DynamicList.push_back(
{Arg->getValue(), /*IsExternCpp*/ false, /*HasWildcard*/ false});
}
for (auto *Arg : Args.filtered(OPT_version_script))
if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
readVersionScript(*Buffer);
}
// 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() {
ELFKind Kind = Config->EKind;
uint16_t Machine = Config->EMachine;
// There is an ILP32 ABI for x86-64, although it's not very popular.
// It is called the x32 ABI.
bool IsX32 = (Kind == ELF32LEKind && Machine == EM_X86_64);
Config->CopyRelocs = (Config->Relocatable || Config->EmitRelocs);
Config->Is64 = (Kind == ELF64LEKind || Kind == ELF64BEKind);
Config->IsLE = (Kind == ELF32LEKind || Kind == ELF64LEKind);
Config->Endianness =
Config->IsLE ? support::endianness::little : support::endianness::big;
Config->IsMips64EL = (Kind == ELF64LEKind && Machine == EM_MIPS);
Config->IsRela = Config->Is64 || IsX32 || Config->MipsN32Abi;
Config->Pic = Config->Pie || Config->Shared;
Config->Wordsize = Config->Is64 ? 8 : 4;
}
// Returns a value of "-format" option.
static bool getBinaryOption(StringRef S) {
if (S == "binary")
return true;
if (S == "elf" || S == "default")
return false;
error("unknown -format value: " + S +
" (supported formats: elf, default, binary)");
return false;
}
void LinkerDriver::createFiles(opt::InputArgList &Args) {
for (auto *Arg : Args) {
switch (Arg->getOption().getUnaliasedOption().getID()) {
case OPT_library:
addLibrary(Arg->getValue());
break;
case OPT_INPUT:
addFile(Arg->getValue(), /*WithLOption=*/false);
break;
case OPT_script:
if (Optional<std::string> Path = searchLinkerScript(Arg->getValue())) {
if (Optional<MemoryBufferRef> MB = readFile(*Path))
readLinkerScript(*MB);
break;
}
error(Twine("cannot find linker script ") + Arg->getValue());
break;
case OPT_as_needed:
Config->AsNeeded = true;
break;
case OPT_format:
InBinary = getBinaryOption(Arg->getValue());
break;
case OPT_no_as_needed:
Config->AsNeeded = false;
break;
case OPT_Bstatic:
Config->Static = true;
break;
case OPT_Bdynamic:
Config->Static = false;
break;
case OPT_whole_archive:
InWholeArchive = true;
break;
case OPT_no_whole_archive:
InWholeArchive = false;
break;
case OPT_start_lib:
InLib = true;
break;
case OPT_end_lib:
InLib = false;
break;
}
}
if (Files.empty() && errorCount() == 0)
error("no input files");
}
// If -m <machine_type> was not given, infer it from object files.
void LinkerDriver::inferMachineType() {
if (Config->EKind != ELFNoneKind)
return;
for (InputFile *F : Files) {
if (F->EKind == ELFNoneKind)
continue;
Config->EKind = F->EKind;
Config->EMachine = F->EMachine;
Config->OSABI = F->OSABI;
Config->MipsN32Abi = Config->EMachine == EM_MIPS && isMipsN32Abi(F);
return;
}
error("target emulation unknown: -m or at least one .o file required");
}
// Parse -z max-page-size=<value>. The default value is defined by
// each target.
static uint64_t getMaxPageSize(opt::InputArgList &Args) {
uint64_t Val = args::getZOptionValue(Args, OPT_z, "max-page-size",
Target->DefaultMaxPageSize);
if (!isPowerOf2_64(Val))
error("max-page-size: value isn't a power of 2");
return Val;
}
// Parses -image-base option.
static Optional<uint64_t> getImageBase(opt::InputArgList &Args) {
// Because we are using "Config->MaxPageSize" here, this function has to be
// called after the variable is initialized.
auto *Arg = Args.getLastArg(OPT_image_base);
if (!Arg)
return None;
StringRef S = Arg->getValue();
uint64_t V;
if (!to_integer(S, V)) {
error("-image-base: number expected, but got " + S);
return 0;
}
if ((V % Config->MaxPageSize) != 0)
warn("-image-base: address isn't multiple of page size: " + S);
return V;
}
// Parses `--exclude-libs=lib,lib,...`.
// The library names may be delimited by commas or colons.
static DenseSet<StringRef> getExcludeLibs(opt::InputArgList &Args) {
DenseSet<StringRef> Ret;
for (auto *Arg : Args.filtered(OPT_exclude_libs)) {
StringRef S = Arg->getValue();
for (;;) {
size_t Pos = S.find_first_of(",:");
if (Pos == StringRef::npos)
break;
Ret.insert(S.substr(0, Pos));
S = S.substr(Pos + 1);
}
Ret.insert(S);
}
return Ret;
}
static Optional<StringRef> getArchiveName(InputFile *File) {
if (isa<ArchiveFile>(File))
return File->getName();
if (!File->ArchiveName.empty())
return File->ArchiveName;
return None;
}
// Handles the -exclude-libs option. If a static library file is specified
// by the -exclude-libs option, all public symbols from the archive become
// private unless otherwise specified by version scripts or something.
// A special library name "ALL" means all archive files.
//
// This is not a popular option, but some programs such as bionic libc use it.
template <class ELFT>
static void excludeLibs(opt::InputArgList &Args, ArrayRef<InputFile *> Files) {
DenseSet<StringRef> Libs = getExcludeLibs(Args);
bool All = Libs.count("ALL");
for (InputFile *File : Files)
if (Optional<StringRef> Archive = getArchiveName(File))
if (All || Libs.count(path::filename(*Archive)))
for (Symbol *Sym : File->getSymbols())
if (!Sym->isLocal())
Sym->VersionId = VER_NDX_LOCAL;
}
// Do actual linking. Note that when this function is called,
// all linker scripts have already been parsed.
template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
Target = getTarget();
Config->MaxPageSize = getMaxPageSize(Args);
Config->ImageBase = getImageBase(Args);
// If a -hash-style option was not given, set to a default value,
// which varies depending on the target.
if (!Args.hasArg(OPT_hash_style)) {
if (Config->EMachine == EM_MIPS)
Config->SysvHash = true;
else
Config->SysvHash = Config->GnuHash = true;
}
// Default output filename is "a.out" by the Unix tradition.
if (Config->OutputFile.empty())
Config->OutputFile = "a.out";
// 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;
// Use default entry point name if no name was given via the command
// line nor linker scripts. For some reason, MIPS entry point name is
// different from others.
Config->WarnMissingEntry =
(!Config->Entry.empty() || (!Config->Shared && !Config->Relocatable));
if (Config->Entry.empty() && !Config->Relocatable)
Config->Entry = (Config->EMachine == EM_MIPS) ? "__start" : "_start";
// Handle --trace-symbol.
for (auto *Arg : Args.filtered(OPT_trace_symbol))
Symtab->trace(Arg->getValue());
// 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<ELFT>(F);
// Process -defsym option.
for (auto *Arg : Args.filtered(OPT_defsym)) {
StringRef From;
StringRef To;
std::tie(From, To) = StringRef(Arg->getValue()).split('=');
readDefsym(From, MemoryBufferRef(To, "-defsym"));
}
// Now that we have every file, we can decide if we will need a
// dynamic symbol table.
// We need one if we were asked to export dynamic symbols or if we are
// producing a shared library.
// We also need one if any shared libraries are used and for pie executables
// (probably because the dynamic linker needs it).
Config->HasDynSymTab =
!SharedFiles.empty() || Config->Pic || Config->ExportDynamic;
// Some symbols (such as __ehdr_start) are defined lazily only when there
// are undefined symbols for them, so we add these to trigger that logic.
for (StringRef Sym : Script->ReferencedSymbols)
Symtab->addUndefined<ELFT>(Sym);
// Handle the `--undefined <sym>` options.
for (StringRef S : Config->Undefined)
Symtab->fetchIfLazy<ELFT>(S);
// If an entry symbol is in a static archive, pull out that file now
// to complete the symbol table. After this, no new names except a
// few linker-synthesized ones will be added to the symbol table.
Symtab->fetchIfLazy<ELFT>(Config->Entry);
// Return if there were name resolution errors.
if (errorCount())
return;
// Handle undefined symbols in DSOs.
Symtab->scanShlibUndefined<ELFT>();
// Handle the -exclude-libs option.
if (Args.hasArg(OPT_exclude_libs))
excludeLibs<ELFT>(Args, Files);
// Create ElfHeader early. We need a dummy section in
// addReservedSymbols to mark the created symbols as not absolute.
Out::ElfHeader = make<OutputSection>("", 0, SHF_ALLOC);
Out::ElfHeader->Size = sizeof(typename ELFT::Ehdr);
// We need to create some reserved symbols such as _end. Create them.
if (!Config->Relocatable)
addReservedSymbols<ELFT>();
// Apply version scripts.
Symtab->scanVersionScript();
// Create wrapped symbols for -wrap option.
for (auto *Arg : Args.filtered(OPT_wrap))
Symtab->addSymbolWrap<ELFT>(Arg->getValue());
Symtab->addCombinedLTOObject<ELFT>();
if (errorCount())
return;
// Apply symbol renames for -wrap.
Symtab->applySymbolWrap();
// Now that we have a complete list of input files.
// Beyond this point, no new files are added.
// Aggregate all input sections into one place.
for (InputFile *F : ObjectFiles)
for (InputSectionBase *S : F->getSections())
if (S && S != &InputSection::Discarded)
InputSections.push_back(S);
for (BinaryFile *F : BinaryFiles)
for (InputSectionBase *S : F->getSections())
InputSections.push_back(cast<InputSection>(S));
// We do not want to emit debug sections if --strip-all
// or -strip-debug are given.
if (Config->Strip != StripPolicy::None)
llvm::erase_if(InputSections, [](InputSectionBase *S) {
return S->Name.startswith(".debug") || S->Name.startswith(".zdebug");
});
Config->EFlags = Target->calcEFlags();
if (Config->EMachine == EM_ARM) {
// FIXME: These warnings can be removed when lld only uses these features
// when the input objects have been compiled with an architecture that
// supports them.
if (Config->ARMHasBlx == false)
warn("lld uses blx instruction, no object with architecture supporting "
"feature detected.");
if (Config->ARMJ1J2BranchEncoding == false)
warn("lld uses extended branch encoding, no object with architecture "
"supporting feature detected.");
if (Config->ARMHasMovtMovw == false)
warn("lld may use movt/movw, no object with architecture supporting "
"feature detected.");
}
// This adds a .comment section containing a version string. We have to add it
// before decompressAndMergeSections because the .comment section is a
// mergeable section.
if (!Config->Relocatable)
InputSections.push_back(createCommentSection());
// Do size optimizations: garbage collection, merging of SHF_MERGE sections
// and identical code folding.
markLive<ELFT>();
decompressSections();
mergeSections();
if (Config->ICF)
doIcf<ELFT>();
// Write the result to the file.
writeResult<ELFT>();
}
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