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llvm-project/lld/COFF/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.
//
//===----------------------------------------------------------------------===//
#include "Config.h"
#include "Driver.h"
#include "Error.h"
#include "InputFiles.h"
#include "SymbolTable.h"
#include "Symbols.h"
#include "Writer.h"
#include "llvm/ADT/Optional.h"
#include "llvm/LibDriver/LibDriver.h"
#include "llvm/Option/Arg.h"
#include "llvm/Option/ArgList.h"
#include "llvm/Option/Option.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <memory>
using namespace llvm;
using namespace llvm::COFF;
using llvm::sys::Process;
using llvm::sys::fs::OpenFlags;
using llvm::sys::fs::file_magic;
using llvm::sys::fs::identify_magic;
namespace lld {
namespace coff {
Configuration *Config;
LinkerDriver *Driver;
void link(llvm::ArrayRef<const char *> Args) {
Configuration C;
LinkerDriver D;
Config = &C;
Driver = &D;
return Driver->link(Args);
}
// Drop directory components and replace extension with ".exe".
static std::string getOutputPath(StringRef Path) {
auto P = Path.find_last_of("\\/");
StringRef S = (P == StringRef::npos) ? Path : Path.substr(P + 1);
return (S.substr(0, S.rfind('.')) + ".exe").str();
}
// Opens a file. Path has to be resolved already.
// Newly created memory buffers are owned by this driver.
MemoryBufferRef LinkerDriver::openFile(StringRef Path) {
auto MBOrErr = MemoryBuffer::getFile(Path);
error(MBOrErr, Twine("Could not open ") + Path);
std::unique_ptr<MemoryBuffer> &MB = *MBOrErr;
MemoryBufferRef MBRef = MB->getMemBufferRef();
OwningMBs.push_back(std::move(MB)); // take ownership
return MBRef;
}
static std::unique_ptr<InputFile> createFile(MemoryBufferRef MB) {
// File type is detected by contents, not by file extension.
file_magic Magic = identify_magic(MB.getBuffer());
if (Magic == file_magic::archive)
return std::unique_ptr<InputFile>(new ArchiveFile(MB));
if (Magic == file_magic::bitcode)
return std::unique_ptr<InputFile>(new BitcodeFile(MB));
if (Config->OutputFile == "")
Config->OutputFile = getOutputPath(MB.getBufferIdentifier());
return std::unique_ptr<InputFile>(new ObjectFile(MB));
}
static bool isDecorated(StringRef Sym) {
return Sym.startswith("_") || Sym.startswith("@") || Sym.startswith("?");
}
// Parses .drectve section contents and returns a list of files
// specified by /defaultlib.
void LinkerDriver::parseDirectives(StringRef S) {
llvm::opt::InputArgList Args = Parser.parse(S);
for (auto *Arg : Args) {
switch (Arg->getOption().getID()) {
case OPT_alternatename:
parseAlternateName(Arg->getValue());
break;
case OPT_defaultlib:
if (Optional<StringRef> Path = findLib(Arg->getValue())) {
MemoryBufferRef MB = openFile(*Path);
Symtab.addFile(createFile(MB));
}
break;
case OPT_export: {
Export E = parseExport(Arg->getValue());
E.Directives = true;
Config->Exports.push_back(E);
break;
}
case OPT_failifmismatch:
checkFailIfMismatch(Arg->getValue());
break;
case OPT_incl:
addUndefined(Arg->getValue());
break;
case OPT_merge:
parseMerge(Arg->getValue());
break;
case OPT_nodefaultlib:
Config->NoDefaultLibs.insert(doFindLib(Arg->getValue()));
break;
case OPT_editandcontinue:
case OPT_guardsym:
case OPT_throwingnew:
break;
default:
error(Twine(Arg->getSpelling()) + " is not allowed in .drectve");
}
}
}
// Find file from search paths. You can omit ".obj", this function takes
// care of that. Note that the returned path is not guaranteed to exist.
StringRef LinkerDriver::doFindFile(StringRef Filename) {
bool hasPathSep = (Filename.find_first_of("/\\") != StringRef::npos);
if (hasPathSep)
return Filename;
bool hasExt = (Filename.find('.') != StringRef::npos);
for (StringRef Dir : SearchPaths) {
SmallString<128> Path = Dir;
llvm::sys::path::append(Path, Filename);
if (llvm::sys::fs::exists(Path.str()))
return Alloc.save(Path.str());
if (!hasExt) {
Path.append(".obj");
if (llvm::sys::fs::exists(Path.str()))
return Alloc.save(Path.str());
}
}
return Filename;
}
// Resolves a file path. This never returns the same path
// (in that case, it returns None).
Optional<StringRef> LinkerDriver::findFile(StringRef Filename) {
StringRef Path = doFindFile(Filename);
bool Seen = !VisitedFiles.insert(Path.lower()).second;
if (Seen)
return None;
return Path;
}
// Find library file from search path.
StringRef LinkerDriver::doFindLib(StringRef Filename) {
// Add ".lib" to Filename if that has no file extension.
bool hasExt = (Filename.find('.') != StringRef::npos);
if (!hasExt)
Filename = Alloc.save(Filename + ".lib");
return doFindFile(Filename);
}
// Resolves a library path. /nodefaultlib options are taken into
// consideration. This never returns the same path (in that case,
// it returns None).
Optional<StringRef> LinkerDriver::findLib(StringRef Filename) {
if (Config->NoDefaultLibAll)
return None;
StringRef Path = doFindLib(Filename);
if (Config->NoDefaultLibs.count(Path))
return None;
bool Seen = !VisitedFiles.insert(Path.lower()).second;
if (Seen)
return None;
return Path;
}
// Parses LIB environment which contains a list of search paths.
void LinkerDriver::addLibSearchPaths() {
Optional<std::string> EnvOpt = Process::GetEnv("LIB");
if (!EnvOpt.hasValue())
return;
StringRef Env = Alloc.save(*EnvOpt);
while (!Env.empty()) {
StringRef Path;
std::tie(Path, Env) = Env.split(';');
SearchPaths.push_back(Path);
}
}
Undefined *LinkerDriver::addUndefined(StringRef Name) {
Undefined *U = Symtab.addUndefined(Name);
Config->GCRoot.insert(U);
return U;
}
// Symbol names are mangled by appending "_" prefix on x86.
StringRef LinkerDriver::mangle(StringRef Sym) {
assert(Config->Machine != IMAGE_FILE_MACHINE_UNKNOWN);
if (Config->Machine == I386)
return Alloc.save("_" + Sym);
return Sym;
}
// Windows specific -- find default entry point name.
StringRef LinkerDriver::findDefaultEntry() {
// User-defined main functions and their corresponding entry points.
static const char *Entries[][2] = {
{"main", "mainCRTStartup"},
{"wmain", "wmainCRTStartup"},
{"WinMain", "WinMainCRTStartup"},
{"wWinMain", "wWinMainCRTStartup"},
};
for (auto E : Entries) {
StringRef Entry = Symtab.findMangle(mangle(E[0]));
if (!Entry.empty() && !isa<Undefined>(Symtab.find(Entry)->Body))
return mangle(E[1]);
}
return "";
}
WindowsSubsystem LinkerDriver::inferSubsystem() {
if (Config->DLL)
return IMAGE_SUBSYSTEM_WINDOWS_GUI;
if (Symtab.findUnderscore("main") || Symtab.findUnderscore("wmain"))
return IMAGE_SUBSYSTEM_WINDOWS_CUI;
if (Symtab.findUnderscore("WinMain") || Symtab.findUnderscore("wWinMain"))
return IMAGE_SUBSYSTEM_WINDOWS_GUI;
return IMAGE_SUBSYSTEM_UNKNOWN;
}
static uint64_t getDefaultImageBase() {
if (Config->is64())
return Config->DLL ? 0x180000000 : 0x140000000;
return Config->DLL ? 0x10000000 : 0x400000;
}
void LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
// If the first command line argument is "/lib", link.exe acts like lib.exe.
// We call our own implementation of lib.exe that understands bitcode files.
if (ArgsArr.size() > 1 && StringRef(ArgsArr[1]).equals_lower("/lib")) {
if (llvm::libDriverMain(ArgsArr.slice(1)) != 0)
error("lib failed");
return;
}
// Needed for LTO.
llvm::InitializeAllTargetInfos();
llvm::InitializeAllTargets();
llvm::InitializeAllTargetMCs();
llvm::InitializeAllAsmParsers();
llvm::InitializeAllAsmPrinters();
llvm::InitializeAllDisassemblers();
// Parse command line options.
llvm::opt::InputArgList Args = Parser.parseLINK(ArgsArr.slice(1));
// Handle /help
if (Args.hasArg(OPT_help)) {
printHelp(ArgsArr[0]);
return;
}
if (Args.filtered_begin(OPT_INPUT) == Args.filtered_end())
error("no input files.");
// Construct search path list.
SearchPaths.push_back("");
for (auto *Arg : Args.filtered(OPT_libpath))
SearchPaths.push_back(Arg->getValue());
addLibSearchPaths();
// Handle /out
if (auto *Arg = Args.getLastArg(OPT_out))
Config->OutputFile = Arg->getValue();
// Handle /verbose
if (Args.hasArg(OPT_verbose))
Config->Verbose = true;
// Handle /force or /force:unresolved
if (Args.hasArg(OPT_force) || Args.hasArg(OPT_force_unresolved))
Config->Force = true;
// Handle /debug
if (Args.hasArg(OPT_debug))
Config->Debug = true;
// Handle /noentry
if (Args.hasArg(OPT_noentry)) {
if (!Args.hasArg(OPT_dll))
error("/noentry must be specified with /dll");
Config->NoEntry = true;
}
// Handle /dll
if (Args.hasArg(OPT_dll)) {
Config->DLL = true;
Config->ManifestID = 2;
}
// Handle /fixed
if (Args.hasArg(OPT_fixed)) {
if (Args.hasArg(OPT_dynamicbase))
error("/fixed must not be specified with /dynamicbase");
Config->Relocatable = false;
Config->DynamicBase = false;
}
// Handle /machine
if (auto *Arg = Args.getLastArg(OPT_machine))
Config->Machine = getMachineType(Arg->getValue());
// Handle /nodefaultlib:<filename>
for (auto *Arg : Args.filtered(OPT_nodefaultlib))
Config->NoDefaultLibs.insert(doFindLib(Arg->getValue()));
// Handle /nodefaultlib
if (Args.hasArg(OPT_nodefaultlib_all))
Config->NoDefaultLibAll = true;
// Handle /base
if (auto *Arg = Args.getLastArg(OPT_base))
parseNumbers(Arg->getValue(), &Config->ImageBase);
// Handle /stack
if (auto *Arg = Args.getLastArg(OPT_stack))
parseNumbers(Arg->getValue(), &Config->StackReserve, &Config->StackCommit);
// Handle /heap
if (auto *Arg = Args.getLastArg(OPT_heap))
parseNumbers(Arg->getValue(), &Config->HeapReserve, &Config->HeapCommit);
// Handle /version
if (auto *Arg = Args.getLastArg(OPT_version))
parseVersion(Arg->getValue(), &Config->MajorImageVersion,
&Config->MinorImageVersion);
// Handle /subsystem
if (auto *Arg = Args.getLastArg(OPT_subsystem))
parseSubsystem(Arg->getValue(), &Config->Subsystem, &Config->MajorOSVersion,
&Config->MinorOSVersion);
// Handle /alternatename
for (auto *Arg : Args.filtered(OPT_alternatename))
parseAlternateName(Arg->getValue());
// Handle /include
for (auto *Arg : Args.filtered(OPT_incl))
addUndefined(Arg->getValue());
// Handle /implib
if (auto *Arg = Args.getLastArg(OPT_implib))
Config->Implib = Arg->getValue();
// Handle /opt
for (auto *Arg : Args.filtered(OPT_opt)) {
std::string Str = StringRef(Arg->getValue()).lower();
SmallVector<StringRef, 1> Vec;
StringRef(Str).split(Vec, ',');
for (StringRef S : Vec) {
if (S == "noref") {
Config->DoGC = false;
Config->DoICF = false;
continue;
}
if (S == "icf" || StringRef(S).startswith("icf=")) {
Config->DoICF = true;
continue;
}
if (S == "noicf") {
Config->DoICF = false;
continue;
}
if (StringRef(S).startswith("lldlto=")) {
StringRef OptLevel = StringRef(S).substr(7);
if (OptLevel.getAsInteger(10, Config->LTOOptLevel) ||
Config->LTOOptLevel > 3)
error("/opt:lldlto: invalid optimization level: " + OptLevel);
continue;
}
if (StringRef(S).startswith("lldltojobs=")) {
StringRef Jobs = StringRef(S).substr(11);
if (Jobs.getAsInteger(10, Config->LTOJobs) || Config->LTOJobs == 0)
error("/opt:lldltojobs: invalid job count: " + Jobs);
continue;
}
if (S != "ref" && S != "lbr" && S != "nolbr")
error(Twine("/opt: unknown option: ") + S);
}
}
// Handle /failifmismatch
for (auto *Arg : Args.filtered(OPT_failifmismatch))
checkFailIfMismatch(Arg->getValue());
// Handle /merge
for (auto *Arg : Args.filtered(OPT_merge))
parseMerge(Arg->getValue());
// Handle /manifest
if (auto *Arg = Args.getLastArg(OPT_manifest_colon))
parseManifest(Arg->getValue());
// Handle /manifestuac
if (auto *Arg = Args.getLastArg(OPT_manifestuac))
parseManifestUAC(Arg->getValue());
// Handle /manifestdependency
if (auto *Arg = Args.getLastArg(OPT_manifestdependency))
Config->ManifestDependency = Arg->getValue();
// Handle /manifestfile
if (auto *Arg = Args.getLastArg(OPT_manifestfile))
Config->ManifestFile = Arg->getValue();
// Handle miscellaneous boolean flags.
if (Args.hasArg(OPT_allowbind_no))
Config->AllowBind = false;
if (Args.hasArg(OPT_allowisolation_no))
Config->AllowIsolation = false;
if (Args.hasArg(OPT_dynamicbase_no))
Config->DynamicBase = false;
if (Args.hasArg(OPT_nxcompat_no))
Config->NxCompat = false;
if (Args.hasArg(OPT_tsaware_no))
Config->TerminalServerAware = false;
if (Args.hasArg(OPT_nosymtab))
Config->WriteSymtab = false;
// Create a list of input files. Files can be given as arguments
// for /defaultlib option.
std::vector<StringRef> Paths;
std::vector<MemoryBufferRef> MBs;
for (auto *Arg : Args.filtered(OPT_INPUT))
if (Optional<StringRef> Path = findFile(Arg->getValue()))
Paths.push_back(*Path);
for (auto *Arg : Args.filtered(OPT_defaultlib))
if (Optional<StringRef> Path = findLib(Arg->getValue()))
Paths.push_back(*Path);
for (StringRef Path : Paths)
MBs.push_back(openFile(Path));
// Windows specific -- Create a resource file containing a manifest file.
if (Config->Manifest == Configuration::Embed) {
std::unique_ptr<MemoryBuffer> MB = createManifestRes();
MBs.push_back(MB->getMemBufferRef());
OwningMBs.push_back(std::move(MB)); // take ownership
}
// Windows specific -- Input files can be Windows resource files (.res files).
// We invoke cvtres.exe to convert resource files to a regular COFF file
// then link the result file normally.
std::vector<MemoryBufferRef> Resources;
auto NotResource = [](MemoryBufferRef MB) {
return identify_magic(MB.getBuffer()) != file_magic::windows_resource;
};
auto It = std::stable_partition(MBs.begin(), MBs.end(), NotResource);
if (It != MBs.end()) {
Resources.insert(Resources.end(), It, MBs.end());
MBs.erase(It, MBs.end());
}
// Read all input files given via the command line. Note that step()
// doesn't read files that are specified by directive sections.
for (MemoryBufferRef MB : MBs)
Symtab.addFile(createFile(MB));
Symtab.step();
// Determine machine type and check if all object files are
// for the same CPU type. Note that this needs to be done before
// any call to mangle().
for (std::unique_ptr<InputFile> &File : Symtab.getFiles()) {
MachineTypes MT = File->getMachineType();
if (MT == IMAGE_FILE_MACHINE_UNKNOWN)
continue;
if (Config->Machine == IMAGE_FILE_MACHINE_UNKNOWN) {
Config->Machine = MT;
continue;
}
if (Config->Machine != MT)
error(Twine(File->getShortName()) + ": machine type " + machineToStr(MT) +
" conflicts with " + machineToStr(Config->Machine));
}
if (Config->Machine == IMAGE_FILE_MACHINE_UNKNOWN) {
llvm::errs() << "warning: /machine is not specified. x64 is assumed.\n";
Config->Machine = AMD64;
}
// Windows specific -- Convert Windows resource files to a COFF file.
if (!Resources.empty()) {
std::unique_ptr<MemoryBuffer> MB = convertResToCOFF(Resources);
Symtab.addFile(createFile(MB->getMemBufferRef()));
OwningMBs.push_back(std::move(MB)); // take ownership
}
// Handle /largeaddressaware
if (Config->is64() || Args.hasArg(OPT_largeaddressaware))
Config->LargeAddressAware = true;
// Handle /highentropyva
if (Config->is64() && !Args.hasArg(OPT_highentropyva_no))
Config->HighEntropyVA = true;
// Handle /entry and /dll
if (auto *Arg = Args.getLastArg(OPT_entry)) {
Config->Entry = addUndefined(mangle(Arg->getValue()));
} else if (Args.hasArg(OPT_dll) && !Config->NoEntry) {
StringRef S = (Config->Machine == I386) ? "__DllMainCRTStartup@12"
: "_DllMainCRTStartup";
Config->Entry = addUndefined(S);
} else if (!Config->NoEntry) {
// Windows specific -- If entry point name is not given, we need to
// infer that from user-defined entry name.
StringRef S = findDefaultEntry();
if (S.empty())
error("entry point must be defined");
Config->Entry = addUndefined(S);
if (Config->Verbose)
llvm::outs() << "Entry name inferred: " << S << "\n";
}
// Handle /export
for (auto *Arg : Args.filtered(OPT_export)) {
Export E = parseExport(Arg->getValue());
if (Config->Machine == I386) {
if (!isDecorated(E.Name))
E.Name = Alloc.save("_" + E.Name);
if (!E.ExtName.empty() && !isDecorated(E.ExtName))
E.ExtName = Alloc.save("_" + E.ExtName);
}
Config->Exports.push_back(E);
}
// Handle /def
if (auto *Arg = Args.getLastArg(OPT_deffile)) {
MemoryBufferRef MB = openFile(Arg->getValue());
// parseModuleDefs mutates Config object.
parseModuleDefs(MB, &Alloc);
}
// Handle /delayload
for (auto *Arg : Args.filtered(OPT_delayload)) {
Config->DelayLoads.insert(StringRef(Arg->getValue()).lower());
if (Config->Machine == I386) {
Config->DelayLoadHelper = addUndefined("___delayLoadHelper2@8");
} else {
Config->DelayLoadHelper = addUndefined("__delayLoadHelper2");
}
}
// Set default image base if /base is not given.
if (Config->ImageBase == uint64_t(-1))
Config->ImageBase = getDefaultImageBase();
Symtab.addRelative(mangle("__ImageBase"), 0);
if (Config->Machine == I386) {
Config->SEHTable = Symtab.addRelative("___safe_se_handler_table", 0);
Config->SEHCount = Symtab.addAbsolute("___safe_se_handler_count", 0);
}
// We do not support /guard:cf (control flow protection) yet.
// Define CFG symbols anyway so that we can link MSVC 2015 CRT.
Symtab.addAbsolute(mangle("__guard_fids_table"), 0);
Symtab.addAbsolute(mangle("__guard_fids_count"), 0);
Symtab.addAbsolute(mangle("__guard_flags"), 0x100);
// Read as much files as we can from directives sections.
Symtab.run();
// Resolve auxiliary symbols until we get a convergence.
// (Trying to resolve a symbol may trigger a Lazy symbol to load a new file.
// A new file may contain a directive section to add new command line options.
// That's why we have to repeat until converge.)
for (;;) {
// Windows specific -- if entry point is not found,
// search for its mangled names.
if (Config->Entry)
Symtab.mangleMaybe(Config->Entry);
// Windows specific -- Make sure we resolve all dllexported symbols.
for (Export &E : Config->Exports) {
if (!E.ForwardTo.empty())
continue;
E.Sym = addUndefined(E.Name);
if (!E.Directives)
Symtab.mangleMaybe(E.Sym);
}
// Add weak aliases. Weak aliases is a mechanism to give remaining
// undefined symbols final chance to be resolved successfully.
for (auto Pair : Config->AlternateNames) {
StringRef From = Pair.first;
StringRef To = Pair.second;
Symbol *Sym = Symtab.find(From);
if (!Sym)
continue;
if (auto *U = dyn_cast<Undefined>(Sym->Body))
if (!U->WeakAlias)
U->WeakAlias = Symtab.addUndefined(To);
}
// Windows specific -- if __load_config_used can be resolved, resolve it.
if (Symtab.findUnderscore("_load_config_used"))
addUndefined(mangle("_load_config_used"));
if (Symtab.queueEmpty())
break;
Symtab.run();
}
// Do LTO by compiling bitcode input files to a set of native COFF files then
// link those files.
Symtab.addCombinedLTOObjects();
// Make sure we have resolved all symbols.
Symtab.reportRemainingUndefines(/*Resolve=*/true);
// Windows specific -- if no /subsystem is given, we need to infer
// that from entry point name.
if (Config->Subsystem == IMAGE_SUBSYSTEM_UNKNOWN) {
Config->Subsystem = inferSubsystem();
if (Config->Subsystem == IMAGE_SUBSYSTEM_UNKNOWN)
error("subsystem must be defined");
}
// Handle /safeseh.
if (Args.hasArg(OPT_safeseh))
for (ObjectFile *File : Symtab.ObjectFiles)
if (!File->SEHCompat)
error("/safeseh: " + File->getName() + " is not compatible with SEH");
// Windows specific -- when we are creating a .dll file, we also
// need to create a .lib file.
if (!Config->Exports.empty() || Config->DLL) {
fixupExports();
writeImportLibrary();
assignExportOrdinals();
}
// Windows specific -- Create a side-by-side manifest file.
if (Config->Manifest == Configuration::SideBySide)
createSideBySideManifest();
// Create a dummy PDB file to satisfy build sytem rules.
if (auto *Arg = Args.getLastArg(OPT_pdb))
createPDB(Arg->getValue());
// Identify unreferenced COMDAT sections.
if (Config->DoGC)
markLive(Symtab.getChunks());
// Identify identical COMDAT sections to merge them.
if (Config->DoICF)
doICF(Symtab.getChunks());
// Write the result.
writeResult(&Symtab);
// Create a symbol map file containing symbol VAs and their names
// to help debugging.
if (auto *Arg = Args.getLastArg(OPT_lldmap)) {
std::error_code EC;
llvm::raw_fd_ostream Out(Arg->getValue(), EC, OpenFlags::F_Text);
error(EC, "Could not create the symbol map");
Symtab.printMap(Out);
}
// Call exit to avoid calling destructors.
exit(0);
}
} // namespace coff
} // namespace lld
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