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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 to us
// and don't try to make effort on our side.
//
//===----------------------------------------------------------------------===//
#include "Driver.h"
#include "Config.h"
#include "Error.h"
#include "ICF.h"
#include "InputFiles.h"
#include "InputSection.h"
#include "LinkerScript.h"
#include "Memory.h"
#include "Strings.h"
#include "SymbolTable.h"
#include "Target.h"
#include "Threads.h"
#include "Writer.h"
#include "lld/Config/Version.h"
#include "lld/Driver/Driver.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Object/Decompressor.h"
#include "llvm/Support/CommandLine.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;
BumpPtrAllocator elf::BAlloc;
StringSaver elf::Saver{BAlloc};
std::vector<SpecificAllocBase *> elf::SpecificAllocBase::Instances;
bool elf::link(ArrayRef<const char *> Args, bool CanExitEarly,
raw_ostream &Error) {
ErrorCount = 0;
ErrorOS = &Error;
Argv0 = Args[0];
Tar = nullptr;
Config = make<Configuration>();
Driver = make<LinkerDriver>();
ScriptConfig = make<ScriptConfiguration>();
Driver->main(Args, CanExitEarly);
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})
.Case("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) {
if (S == "i386pe" || S == "i386pep" || S == "thumb2pe")
error("Windows targets are not supported on the ELF frontend: " + Emul);
else
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<MemoryBufferRef>
LinkerDriver::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 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");
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;
}
// Opens and parses a file. Path has to be resolved already.
// Newly created memory buffers are owned by this driver.
void LinkerDriver::addFile(StringRef Path) {
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:
if (InWholeArchive) {
for (MemoryBufferRef MB : getArchiveMembers(MBRef))
Files.push_back(createObjectFile(MB, Path));
return;
}
Files.push_back(make<ArchiveFile>(MBRef));
return;
case file_magic::elf_shared_object:
if (Config->Relocatable) {
error("attempted static link of dynamic object " + Path);
return;
}
Files.push_back(createSharedFile(MBRef));
return;
default:
if (InLib)
Files.push_back(make<LazyObjectFile>(MBRef));
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);
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->Pie && Config->Shared)
error("-shared and -pie may not be used together");
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 StringRef getString(opt::InputArgList &Args, unsigned Key,
StringRef Default = "") {
if (auto *Arg = Args.getLastArg(Key))
return Arg->getValue();
return Default;
}
static int getInteger(opt::InputArgList &Args, unsigned Key, int Default) {
int V = Default;
if (auto *Arg = Args.getLastArg(Key)) {
StringRef S = Arg->getValue();
if (S.getAsInteger(10, V))
error(Arg->getSpelling() + ": number expected, but got " + S);
}
return V;
}
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;
}
static uint64_t getZOptionValue(opt::InputArgList &Args, StringRef Key,
uint64_t Default) {
for (auto *Arg : Args.filtered(OPT_z)) {
StringRef Value = Arg->getValue();
size_t Pos = Value.find("=");
if (Pos != StringRef::npos && Key == Value.substr(0, Pos)) {
Value = Value.substr(Pos + 1);
uint64_t Result;
if (Value.getAsInteger(0, Result))
error("invalid " + Key + ": " + Value);
return Result;
}
}
return Default;
}
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.
Config->ErrorLimit = getInteger(Args, OPT_error_limit, 20);
// Handle -help
if (Args.hasArg(OPT_help)) {
printHelp(ArgsArr[0]);
return;
}
// GNU linkers disagree here. Though both -version and -v are mentioned
// in help to print the version information, GNU ld just normally exits,
// while gold can continue linking. We are compatible with ld.bfd here.
if (Args.hasArg(OPT_version) || Args.hasArg(OPT_v))
outs() << getLLDVersion() << "\n";
if (Args.hasArg(OPT_version))
return;
Config->ExitEarly = CanExitEarly && !Args.hasArg(OPT_full_shutdown);
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();
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 bool getArg(opt::InputArgList &Args, unsigned K1, unsigned K2,
bool Default) {
if (auto *Arg = Args.getLastArg(K1, K2))
return Arg->getOption().getID() == K1;
return Default;
}
// Determines what we should do if there are remaining unresolved
// symbols after the name resolution.
static UnresolvedPolicy getUnresolvedSymbolPolicy(opt::InputArgList &Args) {
// -noinhibit-exec or -r imply some default values.
if (Args.hasArg(OPT_noinhibit_exec))
return UnresolvedPolicy::WarnAll;
if (Config->Relocatable)
return UnresolvedPolicy::IgnoreAll;
UnresolvedPolicy ErrorOrWarn =
getArg(Args, OPT_error_undef, OPT_warn_undef, 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 getTarget2Option(opt::InputArgList &Args) {
if (auto *Arg = Args.getLastArg(OPT_target2)) {
StringRef S = Arg->getValue();
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 getDiscardOption(opt::InputArgList &Args) {
if (Config->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 StripPolicy getStripOption(opt::InputArgList &Args) {
if (auto *Arg = Args.getLastArg(OPT_strip_all, OPT_strip_debug)) {
if (Arg->getOption().getID() == OPT_strip_all)
return StripPolicy::All;
return StripPolicy::Debug;
}
return StripPolicy::None;
}
static uint64_t parseSectionAddress(StringRef S, opt::Arg *Arg) {
uint64_t VA = 0;
if (S.startswith("0x"))
S = S.drop_front(2);
if (S.getAsInteger(16, VA))
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 getSortKind(opt::InputArgList &Args) {
StringRef S = getString(Args, 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 std::vector<StringRef> getLines(MemoryBufferRef MB) {
SmallVector<StringRef, 0> Arr;
MB.getBuffer().split(Arr, '\n');
std::vector<StringRef> Ret;
for (StringRef S : Arr) {
S = S.trim();
if (!S.empty())
Ret.push_back(S);
}
return Ret;
}
// Initializes Config members by the command line options.
void LinkerDriver::readConfigs(opt::InputArgList &Args) {
for (auto *Arg : Args.filtered(OPT_L))
Config->SearchPaths.push_back(Arg->getValue());
std::vector<StringRef> RPaths;
for (auto *Arg : Args.filtered(OPT_rpath))
RPaths.push_back(Arg->getValue());
if (!RPaths.empty())
Config->RPath = llvm::join(RPaths.begin(), RPaths.end(), ":");
if (auto *Arg = Args.getLastArg(OPT_m)) {
// Parse ELF{32,64}{LE,BE} and CPU type.
StringRef S = Arg->getValue();
std::tie(Config->EKind, Config->EMachine, Config->OSABI) =
parseEmulation(S);
Config->MipsN32Abi = (S == "elf32btsmipn32" || S == "elf32ltsmipn32");
Config->Emulation = S;
}
Config->AllowMultipleDefinition = Args.hasArg(OPT_allow_multiple_definition);
Config->Bsymbolic = Args.hasArg(OPT_Bsymbolic);
Config->BsymbolicFunctions = Args.hasArg(OPT_Bsymbolic_functions);
Config->Demangle = getArg(Args, OPT_demangle, OPT_no_demangle, true);
Config->DisableVerify = Args.hasArg(OPT_disable_verify);
Config->EhFrameHdr = Args.hasArg(OPT_eh_frame_hdr);
Config->EnableNewDtags = !Args.hasArg(OPT_disable_new_dtags);
Config->ExportDynamic =
getArg(Args, OPT_export_dynamic, OPT_no_export_dynamic, false);
Config->FatalWarnings =
getArg(Args, OPT_fatal_warnings, OPT_no_fatal_warnings, false);
Config->GcSections = getArg(Args, OPT_gc_sections, OPT_no_gc_sections, false);
Config->GdbIndex = Args.hasArg(OPT_gdb_index);
Config->ICF = Args.hasArg(OPT_icf);
Config->NoGnuUnique = Args.hasArg(OPT_no_gnu_unique);
Config->NoUndefinedVersion = Args.hasArg(OPT_no_undefined_version);
Config->Nostdlib = Args.hasArg(OPT_nostdlib);
Config->OMagic = Args.hasArg(OPT_omagic);
Config->Pie = getArg(Args, OPT_pie, OPT_nopie, false);
Config->PrintGcSections = Args.hasArg(OPT_print_gc_sections);
Config->Relocatable = Args.hasArg(OPT_relocatable);
Config->DefineCommon = getArg(Args, OPT_define_common, OPT_no_define_common,
!Config->Relocatable);
Config->Discard = getDiscardOption(Args);
Config->SaveTemps = Args.hasArg(OPT_save_temps);
Config->SingleRoRx = Args.hasArg(OPT_no_rosegment);
Config->Shared = Args.hasArg(OPT_shared);
Config->Target1Rel = getArg(Args, OPT_target1_rel, OPT_target1_abs, false);
Config->Threads = getArg(Args, OPT_threads, OPT_no_threads, true);
Config->Trace = Args.hasArg(OPT_trace);
Config->Verbose = Args.hasArg(OPT_verbose);
Config->WarnCommon = Args.hasArg(OPT_warn_common);
Config->DynamicLinker = getString(Args, OPT_dynamic_linker);
Config->Entry = getString(Args, OPT_entry);
Config->Fini = getString(Args, OPT_fini, "_fini");
Config->Init = getString(Args, OPT_init, "_init");
Config->LTOAAPipeline = getString(Args, OPT_lto_aa_pipeline);
Config->LTONewPmPasses = getString(Args, OPT_lto_newpm_passes);
Config->MapFile = getString(Args, OPT_Map);
Config->OutputFile = getString(Args, OPT_o);
Config->SoName = getString(Args, OPT_soname);
Config->Sysroot = getString(Args, OPT_sysroot);
Config->Optimize = getInteger(Args, OPT_O, 1);
Config->LTOO = getInteger(Args, OPT_lto_O, 2);
if (Config->LTOO > 3)
error("invalid optimization level for LTO: " + getString(Args, OPT_lto_O));
Config->LTOPartitions = getInteger(Args, OPT_lto_partitions, 1);
if (Config->LTOPartitions == 0)
error("--lto-partitions: number of threads must be > 0");
Config->ThinLTOJobs = getInteger(Args, OPT_thinlto_jobs, -1u);
if (Config->ThinLTOJobs == 0)
error("--thinlto-jobs: number of threads must be > 0");
Config->ZCombreloc = !hasZOption(Args, "nocombreloc");
Config->ZExecstack = hasZOption(Args, "execstack");
Config->ZNodelete = hasZOption(Args, "nodelete");
Config->ZNow = hasZOption(Args, "now");
Config->ZOrigin = hasZOption(Args, "origin");
Config->ZRelro = !hasZOption(Args, "norelro");
Config->ZStackSize = getZOptionValue(Args, "stack-size", -1);
Config->ZWxneeded = hasZOption(Args, "wxneeded");
Config->OFormatBinary = isOutputFormatBinary(Args);
Config->SectionStartMap = getSectionStartMap(Args);
Config->SortSection = getSortKind(Args);
Config->Target2 = getTarget2Option(Args);
Config->UnresolvedSymbols = getUnresolvedSymbolPolicy(Args);
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;
if (!Config->Relocatable)
Config->Strip = getStripOption(Args);
// Config->Pic is true if we are generating position-independent code.
Config->Pic = Config->Pie || Config->Shared;
if (auto *Arg = Args.getLastArg(OPT_hash_style)) {
StringRef S = Arg->getValue();
if (S == "gnu") {
Config->GnuHash = true;
Config->SysvHash = false;
} else if (S == "both") {
Config->GnuHash = true;
} else if (S != "sysv")
error("unknown hash style: " + S);
}
// Parse --build-id or --build-id=<style>.
if (Args.hasArg(OPT_build_id))
Config->BuildId = BuildIdKind::Fast;
if (auto *Arg = Args.getLastArg(OPT_build_id_eq)) {
StringRef S = Arg->getValue();
if (S == "md5") {
Config->BuildId = BuildIdKind::Md5;
} else if (S == "sha1" || S == "tree") {
Config->BuildId = BuildIdKind::Sha1;
} else if (S == "uuid") {
Config->BuildId = BuildIdKind::Uuid;
} else if (S == "none") {
Config->BuildId = BuildIdKind::None;
} else if (S.startswith("0x")) {
Config->BuildId = BuildIdKind::Hexstring;
Config->BuildIdVector = parseHex(S.substr(2));
} else {
error("unknown --build-id style: " + S);
}
}
for (auto *Arg : Args.filtered(OPT_auxiliary))
Config->AuxiliaryList.push_back(Arg->getValue());
if (!Config->Shared && !Config->AuxiliaryList.empty())
error("-f may not be used without -shared");
for (auto *Arg : Args.filtered(OPT_undefined))
Config->Undefined.push_back(Arg->getValue());
if (auto *Arg = Args.getLastArg(OPT_dynamic_list))
if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
readDynamicList(*Buffer);
if (auto *Arg = Args.getLastArg(OPT_symbol_ordering_file))
if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
Config->SymbolOrderingFile = 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 : getLines(*Buffer))
Config->VersionScriptGlobals.push_back(
{S, /*IsExternCpp*/ false, /*HasWildcard*/ false});
}
for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol))
Config->VersionScriptGlobals.push_back(
{Arg->getValue(), /*IsExternCpp*/ false, /*HasWildcard*/ false});
// Dynamic lists are a simplified linker script that doesn't need the
// "global:" and implicitly ends with a "local:*". Set the variables needed to
// simulate that.
if (Args.hasArg(OPT_dynamic_list) || Args.hasArg(OPT_export_dynamic_symbol)) {
Config->ExportDynamic = true;
if (!Config->Shared)
Config->DefaultSymbolVersion = VER_NDX_LOCAL;
}
if (auto *Arg = Args.getLastArg(OPT_version_script))
if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
readVersionScript(*Buffer);
}
// 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().getID()) {
case OPT_l:
addLibrary(Arg->getValue());
break;
case OPT_INPUT:
addFile(Arg->getValue());
break;
case OPT_alias_script_T:
case OPT_script:
if (Optional<MemoryBufferRef> MB = readFile(Arg->getValue()))
readLinkerScript(*MB);
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 =
getZOptionValue(Args, "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 uint64_t getImageBase(opt::InputArgList &Args) {
// Use default if no -image-base option is given.
// Because we are using "Target" here, this function
// has to be called after the variable is initialized.
auto *Arg = Args.getLastArg(OPT_image_base);
if (!Arg)
return Config->Pic ? 0 : Target->DefaultImageBase;
StringRef S = Arg->getValue();
uint64_t V;
if (S.getAsInteger(0, 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;
}
// 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) {
SymbolTable<ELFT> Symtab;
elf::Symtab<ELFT>::X = &Symtab;
Target = createTarget();
ScriptBase = Script<ELFT>::X = make<LinkerScript<ELFT>>();
Config->Rela =
ELFT::Is64Bits || Config->EMachine == EM_X86_64 || Config->MipsN32Abi;
Config->Mips64EL =
(Config->EMachine == EM_MIPS && Config->EKind == ELF64LEKind);
Config->MaxPageSize = getMaxPageSize(Args);
Config->ImageBase = getImageBase(Args);
// Default output filename is "a.out" by the Unix tradition.
if (Config->OutputFile.empty())
Config->OutputFile = "a.out";
// 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(F);
// 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.
if (Symtab.find(Config->Entry))
Symtab.addUndefined(Config->Entry);
// Return if there were name resolution errors.
if (ErrorCount)
return;
Symtab.scanUndefinedFlags();
Symtab.scanShlibUndefined();
Symtab.scanVersionScript();
Symtab.addCombinedLTOObject();
if (ErrorCount)
return;
for (auto *Arg : Args.filtered(OPT_wrap))
Symtab.wrap(Arg->getValue());
// 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 (elf::ObjectFile<ELFT> *F : Symtab.getObjectFiles())
for (InputSectionBase<ELFT> *S : F->getSections())
if (S && S != &InputSection<ELFT>::Discarded)
Symtab.Sections.push_back(S);
for (BinaryFile *F : Symtab.getBinaryFiles())
for (InputSectionData *S : F->getSections())
Symtab.Sections.push_back(cast<InputSection<ELFT>>(S));
// Do size optimizations: garbage collection and identical code folding.
if (Config->GcSections)
markLive<ELFT>();
if (Config->ICF)
doIcf<ELFT>();
// MergeInputSection::splitIntoPieces needs to be called before
// any call of MergeInputSection::getOffset. Do that.
forEach(Symtab.Sections.begin(), Symtab.Sections.end(),
[](InputSectionBase<ELFT> *S) {
if (!S->Live)
return;
if (Decompressor::isCompressedELFSection(S->Flags, S->Name))
S->uncompress();
if (auto *MS = dyn_cast<MergeInputSection<ELFT>>(S))
MS->splitIntoPieces();
});
// Write the result to the file.
writeResult<ELFT>();
}
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