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[llvm-objcopy] --add-symbol: fix crash if SHT_SYMTAB does not exist
Exposed by D69041. If SHT_SYMTAB does not exist, ELFObjcopy.cpp:handleArgs will crash due
to a null pointer dereference.
for (const NewSymbolInfo &SI : Config.ELF->SymbolsToAdd) {
...
Obj.SymbolTable->addSymbol(
Fix this by creating .symtab and .strtab on demand in ELFBuilder<ELFT>::readSections,
if --add-symbol is specified.
Reviewed By: grimar
Differential Revision: https://reviews.llvm.org/D69093
llvm-svn: 375105
This commit is contained in:
Fangrui Song
parent
b98a2c3cd3
commit
807a019065
81
test/tools/llvm-objcopy/ELF/add-symbol-no-symtab.test
Normal file
81
test/tools/llvm-objcopy/ELF/add-symbol-no-symtab.test
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@ -0,0 +1,81 @@
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## Test --add-symbol creates .symtab if it does not exist.
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# RUN: yaml2obj --docnum=1 %s -o %t
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## If a non-SHF_ALLOC SHT_STRTAB exists but SHT_SYMTAB does not, create .symtab
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## and set its sh_link to the SHT_STRTAB.
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# RUN: llvm-objcopy --remove-section=.symtab %t %t1
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# RUN: llvm-objcopy --add-symbol='abs1=1' %t1 %t2
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# RUN: llvm-readobj -S %t2 | FileCheck --check-prefix=SEC %s
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# RUN: llvm-readelf -s %t2 | FileCheck %s
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# SEC: Index: 1
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# SEC-NEXT: Name: .strtab
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# SEC-NEXT: Type: SHT_STRTAB
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# SEC: Index: 2
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# SEC-NEXT: Name: .shstrtab
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# SEC-NEXT: Type: SHT_STRTAB
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# SEC: Index: 3
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# SEC-NEXT: Name: .symtab
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# SEC-NEXT: Type: SHT_SYMTAB
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# SEC-NOT: }
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# SEC: Link: 1
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# CHECK: 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
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# CHECK-NEXT: 1: 0000000000000001 0 NOTYPE GLOBAL DEFAULT ABS abs1
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## Don't create .symtab if --add-symbol is not specified.
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# RUN: llvm-objcopy --remove-section=.symtab --remove-section=.strtab %t %t1
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# RUN: llvm-objcopy %t1 %t2
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# RUN: llvm-readobj -S %t2 | FileCheck --implicit-check-not=.symtab /dev/null
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## Check that we create both .strtab and .symtab.
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## We reuse the existing .shstrtab (section names) for symbol names.
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## This may look strange but it works.
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# RUN: llvm-objcopy --add-symbol='abs1=1' %t1 %t2
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# RUN: llvm-readobj -S %t2 | FileCheck --check-prefix=SEC2 %s
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# RUN: llvm-readelf -s %t2 | FileCheck %s
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# SEC2: Index: 1
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# SEC2-NEXT: Name: .shstrtab
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# SEC2-NEXT: Type: SHT_STRTAB
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# SEC2: Index: 2
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# SEC2-NEXT: Name: .symtab
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# SEC2-NEXT: Type: SHT_SYMTAB
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# SEC2-NOT: }
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# SEC2: Link: 1
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--- !ELF
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FileHeader:
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Class: ELFCLASS64
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Data: ELFDATA2LSB
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Type: ET_REL
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Machine: EM_X86_64
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Symbols:
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...
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## Check the created .symtab does not link to .dynstr (SHF_ALLOC).
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# RUN: yaml2obj --docnum=2 %s -o %t
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# RUN: llvm-objcopy --remove-section=.symtab --remove-section=.strtab %t %t1
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# RUN: llvm-objcopy --add-symbol='abs1=1' %t1 %t2
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# RUN: llvm-readobj -S %t2 | FileCheck --check-prefix=SEC3 %s
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# SEC3: Index: 1
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# SEC3-NEXT: Name: .shstrtab
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# SEC3-NEXT: Type: SHT_STRTAB
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# SEC3: Name: .symtab
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# SEC3-NEXT: Type: SHT_SYMTAB
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# SEC3-NOT: }
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# SEC3: Link: 1
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--- !ELF
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FileHeader:
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Class: ELFCLASS64
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Data: ELFDATA2LSB
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Type: ET_DYN
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Machine: EM_X86_64
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DynamicSymbols:
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- Name: dummy
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Binding: STB_GLOBAL
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Symbols:
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...
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@ -263,7 +263,7 @@ static Error linkToBuildIdDir(const CopyConfig &Config, StringRef ToLink,
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static Error splitDWOToFile(const CopyConfig &Config, const Reader &Reader,
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StringRef File, ElfType OutputElfType) {
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auto DWOFile = Reader.create();
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auto DWOFile = Reader.create(false);
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auto OnlyKeepDWOPred = [&DWOFile](const SectionBase &Sec) {
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return onlyKeepDWOPred(*DWOFile, Sec);
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};
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@ -743,7 +743,7 @@ static Error writeOutput(const CopyConfig &Config, Object &Obj, Buffer &Out,
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Error executeObjcopyOnIHex(const CopyConfig &Config, MemoryBuffer &In,
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Buffer &Out) {
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IHexReader Reader(&In);
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std::unique_ptr<Object> Obj = Reader.create();
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std::unique_ptr<Object> Obj = Reader.create(true);
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const ElfType OutputElfType =
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getOutputElfType(Config.OutputArch.getValueOr(MachineInfo()));
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if (Error E = handleArgs(Config, *Obj, Reader, OutputElfType))
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@ -756,7 +756,7 @@ Error executeObjcopyOnRawBinary(const CopyConfig &Config, MemoryBuffer &In,
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uint8_t NewSymbolVisibility =
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Config.ELF->NewSymbolVisibility.getValueOr((uint8_t)ELF::STV_DEFAULT);
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BinaryReader Reader(&In, NewSymbolVisibility);
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std::unique_ptr<Object> Obj = Reader.create();
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std::unique_ptr<Object> Obj = Reader.create(true);
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// Prefer OutputArch (-O<format>) if set, otherwise fallback to BinaryArch
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// (-B<arch>).
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@ -770,7 +770,7 @@ Error executeObjcopyOnRawBinary(const CopyConfig &Config, MemoryBuffer &In,
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Error executeObjcopyOnBinary(const CopyConfig &Config,
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object::ELFObjectFileBase &In, Buffer &Out) {
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ELFReader Reader(&In, Config.ExtractPartition);
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std::unique_ptr<Object> Obj = Reader.create();
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std::unique_ptr<Object> Obj = Reader.create(!Config.SymbolsToAdd.empty());
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// Prefer OutputArch (-O<format>) if set, otherwise infer it from the input.
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const ElfType OutputElfType =
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Config.OutputArch ? getOutputElfType(Config.OutputArch.getValue())
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@ -1527,7 +1527,7 @@ template <class ELFT> void ELFBuilder<ELFT>::readSectionHeaders() {
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}
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}
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template <class ELFT> void ELFBuilder<ELFT>::readSections() {
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template <class ELFT> void ELFBuilder<ELFT>::readSections(bool EnsureSymtab) {
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// If a section index table exists we'll need to initialize it before we
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// initialize the symbol table because the symbol table might need to
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// reference it.
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@ -1540,6 +1540,27 @@ template <class ELFT> void ELFBuilder<ELFT>::readSections() {
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if (Obj.SymbolTable) {
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Obj.SymbolTable->initialize(Obj.sections());
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initSymbolTable(Obj.SymbolTable);
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} else if (EnsureSymtab) {
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// Reuse the existing SHT_STRTAB section if exists.
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StringTableSection *StrTab = nullptr;
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for (auto &Sec : Obj.sections()) {
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if (Sec.Type == ELF::SHT_STRTAB && !(Sec.Flags & SHF_ALLOC)) {
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StrTab = static_cast<StringTableSection *>(&Sec);
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// Prefer .strtab to .shstrtab.
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if (Obj.SectionNames != &Sec)
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break;
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}
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}
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if (!StrTab)
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StrTab = &Obj.addSection<StringTableSection>();
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SymbolTableSection &SymTab = Obj.addSection<SymbolTableSection>();
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SymTab.Name = ".symtab";
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SymTab.Link = StrTab->Index;
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SymTab.initialize(Obj.sections());
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SymTab.addSymbol("", 0, 0, nullptr, 0, 0, 0, 0);
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Obj.SymbolTable = &SymTab;
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}
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// Now that all sections and symbols have been added we can add
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@ -1578,7 +1599,7 @@ template <class ELFT> void ELFBuilder<ELFT>::readSections() {
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" is not a string table");
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}
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template <class ELFT> void ELFBuilder<ELFT>::build() {
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template <class ELFT> void ELFBuilder<ELFT>::build(bool EnsureSymtab) {
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readSectionHeaders();
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findEhdrOffset();
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@ -1597,7 +1618,7 @@ template <class ELFT> void ELFBuilder<ELFT>::build() {
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Obj.Entry = Ehdr.e_entry;
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Obj.Flags = Ehdr.e_flags;
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readSections();
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readSections(EnsureSymtab);
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readProgramHeaders(HeadersFile);
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}
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@ -1605,7 +1626,7 @@ Writer::~Writer() {}
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Reader::~Reader() {}
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std::unique_ptr<Object> BinaryReader::create() const {
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std::unique_ptr<Object> BinaryReader::create(bool /*EnsureSymtab*/) const {
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return BinaryELFBuilder(MemBuf, NewSymbolVisibility).build();
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}
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@ -1635,28 +1656,28 @@ Expected<std::vector<IHexRecord>> IHexReader::parse() const {
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return std::move(Records);
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}
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std::unique_ptr<Object> IHexReader::create() const {
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std::unique_ptr<Object> IHexReader::create(bool /*EnsureSymtab*/) const {
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std::vector<IHexRecord> Records = unwrapOrError(parse());
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return IHexELFBuilder(Records).build();
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}
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std::unique_ptr<Object> ELFReader::create() const {
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std::unique_ptr<Object> ELFReader::create(bool EnsureSymtab) const {
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auto Obj = std::make_unique<Object>();
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if (auto *O = dyn_cast<ELFObjectFile<ELF32LE>>(Bin)) {
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ELFBuilder<ELF32LE> Builder(*O, *Obj, ExtractPartition);
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Builder.build();
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Builder.build(EnsureSymtab);
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return Obj;
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} else if (auto *O = dyn_cast<ELFObjectFile<ELF64LE>>(Bin)) {
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ELFBuilder<ELF64LE> Builder(*O, *Obj, ExtractPartition);
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Builder.build();
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Builder.build(EnsureSymtab);
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return Obj;
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} else if (auto *O = dyn_cast<ELFObjectFile<ELF32BE>>(Bin)) {
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ELFBuilder<ELF32BE> Builder(*O, *Obj, ExtractPartition);
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Builder.build();
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Builder.build(EnsureSymtab);
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return Obj;
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} else if (auto *O = dyn_cast<ELFObjectFile<ELF64BE>>(Bin)) {
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ELFBuilder<ELF64BE> Builder(*O, *Obj, ExtractPartition);
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Builder.build();
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Builder.build(EnsureSymtab);
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return Obj;
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}
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error("invalid file type");
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@ -863,7 +863,7 @@ public:
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class Reader {
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public:
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virtual ~Reader();
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virtual std::unique_ptr<Object> create() const = 0;
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virtual std::unique_ptr<Object> create(bool EnsureSymtab) const = 0;
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};
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using object::Binary;
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@ -926,7 +926,7 @@ private:
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void initGroupSection(GroupSection *GroupSec);
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void initSymbolTable(SymbolTableSection *SymTab);
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void readSectionHeaders();
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void readSections();
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void readSections(bool EnsureSymtab);
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void findEhdrOffset();
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SectionBase &makeSection(const Elf_Shdr &Shdr);
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@ -936,7 +936,7 @@ public:
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: ElfFile(*ElfObj.getELFFile()), Obj(Obj),
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ExtractPartition(ExtractPartition) {}
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void build();
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void build(bool EnsureSymtab);
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};
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class BinaryReader : public Reader {
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@ -946,7 +946,7 @@ class BinaryReader : public Reader {
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public:
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BinaryReader(MemoryBuffer *MB, const uint8_t NewSymbolVisibility)
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: MemBuf(MB), NewSymbolVisibility(NewSymbolVisibility) {}
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std::unique_ptr<Object> create() const override;
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std::unique_ptr<Object> create(bool EnsureSymtab) const override;
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};
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class IHexReader : public Reader {
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@ -968,7 +968,7 @@ class IHexReader : public Reader {
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public:
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IHexReader(MemoryBuffer *MB) : MemBuf(MB) {}
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std::unique_ptr<Object> create() const override;
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std::unique_ptr<Object> create(bool EnsureSymtab) const override;
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};
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class ELFReader : public Reader {
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@ -976,7 +976,7 @@ class ELFReader : public Reader {
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Optional<StringRef> ExtractPartition;
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public:
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std::unique_ptr<Object> create() const override;
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std::unique_ptr<Object> create(bool EnsureSymtab) const override;
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explicit ELFReader(Binary *B, Optional<StringRef> ExtractPartition)
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: Bin(B), ExtractPartition(ExtractPartition) {}
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};
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