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llvm-mirror/tools/llvm-objcopy/llvm-objcopy.cpp
Paul Semel df343b1764 [llvm-objcopy] Fix null symbol handling 
This fixes the bug where strip-all option was
leading to a malformed outputted ELF file.

Differential Revision: https://reviews.llvm.org/D47414

llvm-svn: 333772
2018-06-01 16:19:46 +00:00

610 lines
21 KiB
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//===- llvm-objcopy.cpp ---------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm-objcopy.h"
#include "Object.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/Object/Binary.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Object/ELFTypes.h"
#include "llvm/Object/Error.h"
#include "llvm/Option/Arg.h"
#include "llvm/Option/ArgList.h"
#include "llvm/Option/Option.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/FileOutputBuffer.h"
#include "llvm/Support/InitLLVM.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <cstdlib>
#include <functional>
#include <iterator>
#include <memory>
#include <string>
#include <system_error>
#include <utility>
using namespace llvm;
using namespace object;
using namespace ELF;
namespace {
enum ObjcopyID {
OBJCOPY_INVALID = 0, // This is not an option ID.
#define OPTION(PREFIX, NAME, ID, KIND, GROUP, ALIAS, ALIASARGS, FLAGS, PARAM, \
HELPTEXT, METAVAR, VALUES) \
OBJCOPY_##ID,
#include "ObjcopyOpts.inc"
#undef OPTION
};
#define PREFIX(NAME, VALUE) const char *const OBJCOPY_##NAME[] = VALUE;
#include "ObjcopyOpts.inc"
#undef PREFIX
static const opt::OptTable::Info ObjcopyInfoTable[] = {
#define OPTION(PREFIX, NAME, ID, KIND, GROUP, ALIAS, ALIASARGS, FLAGS, PARAM, \
HELPTEXT, METAVAR, VALUES) \
{OBJCOPY_##PREFIX, \
NAME, \
HELPTEXT, \
METAVAR, \
OBJCOPY_##ID, \
opt::Option::KIND##Class, \
PARAM, \
FLAGS, \
OBJCOPY_##GROUP, \
OBJCOPY_##ALIAS, \
ALIASARGS, \
VALUES},
#include "ObjcopyOpts.inc"
#undef OPTION
};
class ObjcopyOptTable : public opt::OptTable {
public:
ObjcopyOptTable() : OptTable(ObjcopyInfoTable, true) {}
};
enum StripID {
STRIP_INVALID = 0, // This is not an option ID.
#define OPTION(PREFIX, NAME, ID, KIND, GROUP, ALIAS, ALIASARGS, FLAGS, PARAM, \
HELPTEXT, METAVAR, VALUES) \
STRIP_##ID,
#include "StripOpts.inc"
#undef OPTION
};
#define PREFIX(NAME, VALUE) const char *const STRIP_##NAME[] = VALUE;
#include "StripOpts.inc"
#undef PREFIX
static const opt::OptTable::Info StripInfoTable[] = {
#define OPTION(PREFIX, NAME, ID, KIND, GROUP, ALIAS, ALIASARGS, FLAGS, PARAM, \
HELPTEXT, METAVAR, VALUES) \
{STRIP_##PREFIX, NAME, HELPTEXT, \
METAVAR, STRIP_##ID, opt::Option::KIND##Class, \
PARAM, FLAGS, STRIP_##GROUP, \
STRIP_##ALIAS, ALIASARGS, VALUES},
#include "StripOpts.inc"
#undef OPTION
};
class StripOptTable : public opt::OptTable {
public:
StripOptTable() : OptTable(StripInfoTable, true) {}
};
} // namespace
// The name this program was invoked as.
static StringRef ToolName;
namespace llvm {
LLVM_ATTRIBUTE_NORETURN void error(Twine Message) {
errs() << ToolName << ": " << Message << ".\n";
errs().flush();
exit(1);
}
LLVM_ATTRIBUTE_NORETURN void reportError(StringRef File, std::error_code EC) {
assert(EC);
errs() << ToolName << ": '" << File << "': " << EC.message() << ".\n";
exit(1);
}
LLVM_ATTRIBUTE_NORETURN void reportError(StringRef File, Error E) {
assert(E);
std::string Buf;
raw_string_ostream OS(Buf);
logAllUnhandledErrors(std::move(E), OS, "");
OS.flush();
errs() << ToolName << ": '" << File << "': " << Buf;
exit(1);
}
} // end namespace llvm
struct CopyConfig {
StringRef OutputFilename;
StringRef InputFilename;
StringRef OutputFormat;
StringRef InputFormat;
StringRef BinaryArch;
StringRef SplitDWO;
StringRef AddGnuDebugLink;
std::vector<StringRef> ToRemove;
std::vector<StringRef> Keep;
std::vector<StringRef> OnlyKeep;
std::vector<StringRef> AddSection;
std::vector<StringRef> SymbolsToLocalize;
std::vector<StringRef> SymbolsToGlobalize;
std::vector<StringRef> SymbolsToWeaken;
std::vector<StringRef> SymbolsToRemove;
std::vector<StringRef> SymbolsToKeep;
StringMap<StringRef> SymbolsToRename;
bool StripAll = false;
bool StripAllGNU = false;
bool StripDebug = false;
bool StripSections = false;
bool StripNonAlloc = false;
bool StripDWO = false;
bool StripUnneeded = false;
bool ExtractDWO = false;
bool LocalizeHidden = false;
bool Weaken = false;
bool DiscardAll = false;
bool OnlyKeepDebug = false;
bool KeepFileSymbols = false;
};
using SectionPred = std::function<bool(const SectionBase &Sec)>;
bool IsDWOSection(const SectionBase &Sec) { return Sec.Name.endswith(".dwo"); }
bool OnlyKeepDWOPred(const Object &Obj, const SectionBase &Sec) {
// We can't remove the section header string table.
if (&Sec == Obj.SectionNames)
return false;
// Short of keeping the string table we want to keep everything that is a DWO
// section and remove everything else.
return !IsDWOSection(Sec);
}
std::unique_ptr<Writer> CreateWriter(const CopyConfig &Config, Object &Obj,
StringRef File, ElfType OutputElfType) {
if (Config.OutputFormat == "binary") {
return llvm::make_unique<BinaryWriter>(File, Obj);
}
// Depending on the initial ELFT and OutputFormat we need a different Writer.
switch (OutputElfType) {
case ELFT_ELF32LE:
return llvm::make_unique<ELFWriter<ELF32LE>>(File, Obj,
!Config.StripSections);
case ELFT_ELF64LE:
return llvm::make_unique<ELFWriter<ELF64LE>>(File, Obj,
!Config.StripSections);
case ELFT_ELF32BE:
return llvm::make_unique<ELFWriter<ELF32BE>>(File, Obj,
!Config.StripSections);
case ELFT_ELF64BE:
return llvm::make_unique<ELFWriter<ELF64BE>>(File, Obj,
!Config.StripSections);
}
llvm_unreachable("Invalid output format");
}
void SplitDWOToFile(const CopyConfig &Config, const Reader &Reader,
StringRef File, ElfType OutputElfType) {
auto DWOFile = Reader.create();
DWOFile->removeSections(
[&](const SectionBase &Sec) { return OnlyKeepDWOPred(*DWOFile, Sec); });
auto Writer = CreateWriter(Config, *DWOFile, File, OutputElfType);
Writer->finalize();
Writer->write();
}
// This function handles the high level operations of GNU objcopy including
// handling command line options. It's important to outline certain properties
// we expect to hold of the command line operations. Any operation that "keeps"
// should keep regardless of a remove. Additionally any removal should respect
// any previous removals. Lastly whether or not something is removed shouldn't
// depend a) on the order the options occur in or b) on some opaque priority
// system. The only priority is that keeps/copies overrule removes.
void HandleArgs(const CopyConfig &Config, Object &Obj, const Reader &Reader,
ElfType OutputElfType) {
if (!Config.SplitDWO.empty()) {
SplitDWOToFile(Config, Reader, Config.SplitDWO, OutputElfType);
}
// TODO: update or remove symbols only if there is an option that affects
// them.
if (Obj.SymbolTable) {
Obj.SymbolTable->updateSymbols([&](Symbol &Sym) {
if ((Config.LocalizeHidden &&
(Sym.Visibility == STV_HIDDEN || Sym.Visibility == STV_INTERNAL)) ||
(!Config.SymbolsToLocalize.empty() &&
is_contained(Config.SymbolsToLocalize, Sym.Name)))
Sym.Binding = STB_LOCAL;
if (!Config.SymbolsToGlobalize.empty() &&
is_contained(Config.SymbolsToGlobalize, Sym.Name))
Sym.Binding = STB_GLOBAL;
if (!Config.SymbolsToWeaken.empty() &&
is_contained(Config.SymbolsToWeaken, Sym.Name) &&
Sym.Binding == STB_GLOBAL)
Sym.Binding = STB_WEAK;
if (Config.Weaken && Sym.Binding == STB_GLOBAL &&
Sym.getShndx() != SHN_UNDEF)
Sym.Binding = STB_WEAK;
const auto I = Config.SymbolsToRename.find(Sym.Name);
if (I != Config.SymbolsToRename.end())
Sym.Name = I->getValue();
});
// The purpose of this loop is to mark symbols referenced by sections
// (like GroupSection or RelocationSection). This way, we know which
// symbols are still 'needed' and wich are not.
if (Config.StripUnneeded) {
for (auto &Section : Obj.sections())
Section.markSymbols();
}
Obj.removeSymbols([&](const Symbol &Sym) {
if ((!Config.SymbolsToKeep.empty() &&
is_contained(Config.SymbolsToKeep, Sym.Name)) ||
(Config.KeepFileSymbols && Sym.Type == STT_FILE))
return false;
if (Config.DiscardAll && Sym.Binding == STB_LOCAL &&
Sym.getShndx() != SHN_UNDEF && Sym.Type != STT_FILE &&
Sym.Type != STT_SECTION)
return true;
if (Config.StripAll || Config.StripAllGNU)
return true;
if (!Config.SymbolsToRemove.empty() &&
is_contained(Config.SymbolsToRemove, Sym.Name)) {
return true;
}
if (Config.StripUnneeded && !Sym.Referenced &&
(Sym.Binding == STB_LOCAL || Sym.getShndx() == SHN_UNDEF) &&
Sym.Type != STT_FILE && Sym.Type != STT_SECTION)
return true;
return false;
});
}
SectionPred RemovePred = [](const SectionBase &) { return false; };
// Removes:
if (!Config.ToRemove.empty()) {
RemovePred = [&Config](const SectionBase &Sec) {
return std::find(std::begin(Config.ToRemove), std::end(Config.ToRemove),
Sec.Name) != std::end(Config.ToRemove);
};
}
if (Config.StripDWO || !Config.SplitDWO.empty())
RemovePred = [RemovePred](const SectionBase &Sec) {
return IsDWOSection(Sec) || RemovePred(Sec);
};
if (Config.ExtractDWO)
RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
return OnlyKeepDWOPred(Obj, Sec) || RemovePred(Sec);
};
if (Config.StripAllGNU)
RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
if (RemovePred(Sec))
return true;
if ((Sec.Flags & SHF_ALLOC) != 0)
return false;
if (&Sec == Obj.SectionNames)
return false;
switch (Sec.Type) {
case SHT_SYMTAB:
case SHT_REL:
case SHT_RELA:
case SHT_STRTAB:
return true;
}
return Sec.Name.startswith(".debug");
};
if (Config.StripSections) {
RemovePred = [RemovePred](const SectionBase &Sec) {
return RemovePred(Sec) || (Sec.Flags & SHF_ALLOC) == 0;
};
}
if (Config.StripDebug) {
RemovePred = [RemovePred](const SectionBase &Sec) {
return RemovePred(Sec) || Sec.Name.startswith(".debug");
};
}
if (Config.StripNonAlloc)
RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
if (RemovePred(Sec))
return true;
if (&Sec == Obj.SectionNames)
return false;
return (Sec.Flags & SHF_ALLOC) == 0;
};
if (Config.StripAll)
RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
if (RemovePred(Sec))
return true;
if (&Sec == Obj.SectionNames)
return false;
if (Sec.Name.startswith(".gnu.warning"))
return false;
return (Sec.Flags & SHF_ALLOC) == 0;
};
// Explicit copies:
if (!Config.OnlyKeep.empty()) {
RemovePred = [&Config, RemovePred, &Obj](const SectionBase &Sec) {
// Explicitly keep these sections regardless of previous removes.
if (std::find(std::begin(Config.OnlyKeep), std::end(Config.OnlyKeep),
Sec.Name) != std::end(Config.OnlyKeep))
return false;
// Allow all implicit removes.
if (RemovePred(Sec))
return true;
// Keep special sections.
if (Obj.SectionNames == &Sec)
return false;
if (Obj.SymbolTable == &Sec || Obj.SymbolTable->getStrTab() == &Sec)
return false;
// Remove everything else.
return true;
};
}
if (!Config.Keep.empty()) {
RemovePred = [Config, RemovePred](const SectionBase &Sec) {
// Explicitly keep these sections regardless of previous removes.
if (std::find(std::begin(Config.Keep), std::end(Config.Keep), Sec.Name) !=
std::end(Config.Keep))
return false;
// Otherwise defer to RemovePred.
return RemovePred(Sec);
};
}
// This has to be the last predicate assignment.
// If the option --keep-symbol has been specified
// and at least one of those symbols is present
// (equivalently, the updated symbol table is not empty)
// the symbol table and the string table should not be removed.
if ((!Config.SymbolsToKeep.empty() || Config.KeepFileSymbols) &&
!Obj.SymbolTable->empty()) {
RemovePred = [&Obj, RemovePred](const SectionBase &Sec) {
if (&Sec == Obj.SymbolTable || &Sec == Obj.SymbolTable->getStrTab())
return false;
return RemovePred(Sec);
};
}
Obj.removeSections(RemovePred);
if (!Config.AddSection.empty()) {
for (const auto &Flag : Config.AddSection) {
auto SecPair = Flag.split("=");
auto SecName = SecPair.first;
auto File = SecPair.second;
auto BufOrErr = MemoryBuffer::getFile(File);
if (!BufOrErr)
reportError(File, BufOrErr.getError());
auto Buf = std::move(*BufOrErr);
auto BufPtr = reinterpret_cast<const uint8_t *>(Buf->getBufferStart());
auto BufSize = Buf->getBufferSize();
Obj.addSection<OwnedDataSection>(SecName,
ArrayRef<uint8_t>(BufPtr, BufSize));
}
}
if (!Config.AddGnuDebugLink.empty())
Obj.addSection<GnuDebugLinkSection>(Config.AddGnuDebugLink);
}
std::unique_ptr<Reader> CreateReader(StringRef InputFilename,
ElfType &OutputElfType) {
// Right now we can only read ELF files so there's only one reader;
auto Out = llvm::make_unique<ELFReader>(InputFilename);
// We need to set the default ElfType for output.
OutputElfType = Out->getElfType();
return std::move(Out);
}
void ExecuteElfObjcopy(const CopyConfig &Config) {
ElfType OutputElfType;
auto Reader = CreateReader(Config.InputFilename, OutputElfType);
auto Obj = Reader->create();
auto Writer =
CreateWriter(Config, *Obj, Config.OutputFilename, OutputElfType);
HandleArgs(Config, *Obj, *Reader, OutputElfType);
Writer->finalize();
Writer->write();
}
// ParseObjcopyOptions returns the config and sets the input arguments. If a
// help flag is set then ParseObjcopyOptions will print the help messege and
// exit.
CopyConfig ParseObjcopyOptions(ArrayRef<const char *> ArgsArr) {
ObjcopyOptTable T;
unsigned MissingArgumentIndex, MissingArgumentCount;
llvm::opt::InputArgList InputArgs =
T.ParseArgs(ArgsArr, MissingArgumentIndex, MissingArgumentCount);
if (InputArgs.size() == 0) {
T.PrintHelp(errs(), "llvm-objcopy <input> [ <output> ]", "objcopy tool");
exit(1);
}
if (InputArgs.hasArg(OBJCOPY_help)) {
T.PrintHelp(outs(), "llvm-objcopy <input> [ <output> ]", "objcopy tool");
exit(0);
}
SmallVector<const char *, 2> Positional;
for (auto Arg : InputArgs.filtered(OBJCOPY_UNKNOWN))
error("unknown argument '" + Arg->getAsString(InputArgs) + "'");
for (auto Arg : InputArgs.filtered(OBJCOPY_INPUT))
Positional.push_back(Arg->getValue());
if (Positional.empty())
error("No input file specified");
if (Positional.size() > 2)
error("Too many positional arguments");
CopyConfig Config;
Config.InputFilename = Positional[0];
Config.OutputFilename = Positional[Positional.size() == 1 ? 0 : 1];
Config.InputFormat = InputArgs.getLastArgValue(OBJCOPY_input_target);
Config.OutputFormat = InputArgs.getLastArgValue(OBJCOPY_output_target);
Config.BinaryArch = InputArgs.getLastArgValue(OBJCOPY_binary_architecture);
Config.SplitDWO = InputArgs.getLastArgValue(OBJCOPY_split_dwo);
Config.AddGnuDebugLink = InputArgs.getLastArgValue(OBJCOPY_add_gnu_debuglink);
for (auto Arg : InputArgs.filtered(OBJCOPY_redefine_symbol)) {
if (!StringRef(Arg->getValue()).contains('='))
error("Bad format for --redefine-sym");
auto Old2New = StringRef(Arg->getValue()).split('=');
if (!Config.SymbolsToRename.insert(Old2New).second)
error("Multiple redefinition of symbol " + Old2New.first);
}
for (auto Arg : InputArgs.filtered(OBJCOPY_remove_section))
Config.ToRemove.push_back(Arg->getValue());
for (auto Arg : InputArgs.filtered(OBJCOPY_keep))
Config.Keep.push_back(Arg->getValue());
for (auto Arg : InputArgs.filtered(OBJCOPY_only_keep))
Config.OnlyKeep.push_back(Arg->getValue());
for (auto Arg : InputArgs.filtered(OBJCOPY_add_section))
Config.AddSection.push_back(Arg->getValue());
Config.StripAll = InputArgs.hasArg(OBJCOPY_strip_all);
Config.StripAllGNU = InputArgs.hasArg(OBJCOPY_strip_all_gnu);
Config.StripDebug = InputArgs.hasArg(OBJCOPY_strip_debug);
Config.StripDWO = InputArgs.hasArg(OBJCOPY_strip_dwo);
Config.StripSections = InputArgs.hasArg(OBJCOPY_strip_sections);
Config.StripNonAlloc = InputArgs.hasArg(OBJCOPY_strip_non_alloc);
Config.StripUnneeded = InputArgs.hasArg(OBJCOPY_strip_unneeded);
Config.ExtractDWO = InputArgs.hasArg(OBJCOPY_extract_dwo);
Config.LocalizeHidden = InputArgs.hasArg(OBJCOPY_localize_hidden);
Config.Weaken = InputArgs.hasArg(OBJCOPY_weaken);
Config.DiscardAll = InputArgs.hasArg(OBJCOPY_discard_all);
Config.OnlyKeepDebug = InputArgs.hasArg(OBJCOPY_only_keep_debug);
Config.KeepFileSymbols = InputArgs.hasArg(OBJCOPY_keep_file_symbols);
for (auto Arg : InputArgs.filtered(OBJCOPY_localize_symbol))
Config.SymbolsToLocalize.push_back(Arg->getValue());
for (auto Arg : InputArgs.filtered(OBJCOPY_globalize_symbol))
Config.SymbolsToGlobalize.push_back(Arg->getValue());
for (auto Arg : InputArgs.filtered(OBJCOPY_weaken_symbol))
Config.SymbolsToWeaken.push_back(Arg->getValue());
for (auto Arg : InputArgs.filtered(OBJCOPY_strip_symbol))
Config.SymbolsToRemove.push_back(Arg->getValue());
for (auto Arg : InputArgs.filtered(OBJCOPY_keep_symbol))
Config.SymbolsToKeep.push_back(Arg->getValue());
return Config;
}
// ParseStripOptions returns the config and sets the input arguments. If a
// help flag is set then ParseStripOptions will print the help messege and
// exit.
CopyConfig ParseStripOptions(ArrayRef<const char *> ArgsArr) {
StripOptTable T;
unsigned MissingArgumentIndex, MissingArgumentCount;
llvm::opt::InputArgList InputArgs =
T.ParseArgs(ArgsArr, MissingArgumentIndex, MissingArgumentCount);
if (InputArgs.size() == 0) {
T.PrintHelp(errs(), "llvm-strip <input> [ <output> ]", "strip tool");
exit(1);
}
if (InputArgs.hasArg(STRIP_help)) {
T.PrintHelp(outs(), "llvm-strip <input> [ <output> ]", "strip tool");
exit(0);
}
SmallVector<const char *, 2> Positional;
for (auto Arg : InputArgs.filtered(STRIP_UNKNOWN))
error("unknown argument '" + Arg->getAsString(InputArgs) + "'");
for (auto Arg : InputArgs.filtered(STRIP_INPUT))
Positional.push_back(Arg->getValue());
if (Positional.empty())
error("No input file specified");
if (Positional.size() > 2)
error("Support for multiple input files is not implemented yet");
CopyConfig Config;
Config.InputFilename = Positional[0];
Config.OutputFilename =
InputArgs.getLastArgValue(STRIP_output, Positional[0]);
// Strip debug info only.
Config.StripDebug = InputArgs.hasArg(STRIP_strip_debug);
if (!Config.StripDebug)
Config.StripAll = true;
for (auto Arg : InputArgs.filtered(STRIP_remove_section))
Config.ToRemove.push_back(Arg->getValue());
for (auto Arg : InputArgs.filtered(STRIP_keep_symbol))
Config.SymbolsToKeep.push_back(Arg->getValue());
return Config;
}
int main(int argc, char **argv) {
InitLLVM X(argc, argv);
ToolName = argv[0];
CopyConfig Config;
if (sys::path::stem(ToolName).endswith_lower("strip"))
Config = ParseStripOptions(makeArrayRef(argv + 1, argc));
else
Config = ParseObjcopyOptions(makeArrayRef(argv + 1, argc));
ExecuteElfObjcopy(Config);
}
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