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-rw-r--r--llvm/tools/llvm-objcopy/Object.cpp197
-rw-r--r--llvm/tools/llvm-objcopy/Object.h45
2 files changed, 215 insertions, 27 deletions
diff --git a/llvm/tools/llvm-objcopy/Object.cpp b/llvm/tools/llvm-objcopy/Object.cpp
index b3ad7329bb6..dc77fed988c 100644
--- a/llvm/tools/llvm-objcopy/Object.cpp
+++ b/llvm/tools/llvm-objcopy/Object.cpp
@@ -68,6 +68,10 @@ template <class ELFT> void ELFWriter<ELFT>::writeShdr(const SectionBase &Sec) {
SectionVisitor::~SectionVisitor() {}
+void BinarySectionWriter::visit(const SectionIndexSection &Sec) {
+ error("Cannot write symbol section index table '" + Sec.Name + "' ");
+}
+
void BinarySectionWriter::visit(const SymbolTableSection &Sec) {
error("Cannot write symbol table '" + Sec.Name + "' out to binary");
}
@@ -117,6 +121,29 @@ void StringTableSection::accept(SectionVisitor &Visitor) const {
Visitor.visit(*this);
}
+template <class ELFT>
+void ELFSectionWriter<ELFT>::visit(const SectionIndexSection &Sec) {
+ uint8_t *Buf = Out.getBufferStart() + Sec.Offset;
+ auto *Indexes = reinterpret_cast<typename ELFT::Word *>(Buf);
+ std::copy(std::begin(Sec.Indexes), std::end(Sec.Indexes), Indexes);
+}
+
+void SectionIndexSection::initialize(SectionTableRef SecTable) {
+ Size = 0;
+ setSymTab(SecTable.getSectionOfType<SymbolTableSection>(
+ Link,
+ "Link field value " + Twine(Link) + " in section " + Name + " is invalid",
+ "Link field value " + Twine(Link) + " in section " + Name +
+ " is not a symbol table"));
+ Symbols->setShndxTable(this);
+}
+
+void SectionIndexSection::finalize() { Link = Symbols->Index; }
+
+void SectionIndexSection::accept(SectionVisitor &Visitor) const {
+ Visitor.visit(*this);
+}
+
static bool isValidReservedSectionIndex(uint16_t Index, uint16_t Machine) {
switch (Index) {
case SHN_ABS:
@@ -135,8 +162,12 @@ static bool isValidReservedSectionIndex(uint16_t Index, uint16_t Machine) {
return false;
}
+// Large indexes force us to clarify exactly what this function should do. This
+// function should return the proper value of st_shndx.
uint16_t Symbol::getShndx() const {
if (DefinedIn != nullptr) {
+ if (DefinedIn->Index >= SHN_LORESERVE)
+ return SHN_XINDEX;
return DefinedIn->Index;
}
switch (ShndxType) {
@@ -150,6 +181,7 @@ uint16_t Symbol::getShndx() const {
case SYMBOL_HEXAGON_SCOMMON_2:
case SYMBOL_HEXAGON_SCOMMON_4:
case SYMBOL_HEXAGON_SCOMMON_8:
+ case SYMBOL_XINDEX:
return static_cast<uint16_t>(ShndxType);
}
llvm_unreachable("Symbol with invalid ShndxType encountered");
@@ -164,12 +196,12 @@ void SymbolTableSection::addSymbol(StringRef Name, uint8_t Bind, uint8_t Type,
Sym.Binding = Bind;
Sym.Type = Type;
Sym.DefinedIn = DefinedIn;
- if (DefinedIn == nullptr) {
- if (Shndx >= SHN_LORESERVE)
- Sym.ShndxType = static_cast<SymbolShndxType>(Shndx);
- else
- Sym.ShndxType = SYMBOL_SIMPLE_INDEX;
- }
+ if (DefinedIn != nullptr)
+ DefinedIn->HasSymbol = true;
+ if (Shndx >= SHN_LORESERVE)
+ Sym.ShndxType = static_cast<SymbolShndxType>(Shndx);
+ else
+ Sym.ShndxType = SYMBOL_SIMPLE_INDEX;
Sym.Value = Value;
Sym.Visibility = Visibility;
Sym.Size = Sz;
@@ -179,6 +211,9 @@ void SymbolTableSection::addSymbol(StringRef Name, uint8_t Bind, uint8_t Type,
}
void SymbolTableSection::removeSectionReferences(const SectionBase *Sec) {
+ if (SectionIndexTable == Sec)
+ SectionIndexTable = nullptr;
+
if (SymbolNames == Sec) {
error("String table " + SymbolNames->Name +
" cannot be removed because it is referenced by the symbol table " +
@@ -212,6 +247,7 @@ void SymbolTableSection::localize(
void SymbolTableSection::initialize(SectionTableRef SecTable) {
Size = 0;
+
setStrTab(SecTable.getSectionOfType<StringTableSection>(
Link,
"Symbol table has link index of " + Twine(Link) +
@@ -235,7 +271,17 @@ void SymbolTableSection::finalize() {
Info = MaxLocalIndex + 1;
}
-void SymbolTableSection::addSymbolNames() {
+void SymbolTableSection::prepareForLayout() {
+ // Add all potential section indexes before file layout so that the section
+ // index section has the approprite size.
+ if (SectionIndexTable != nullptr) {
+ for (const auto &Sym : Symbols) {
+ if (Sym->DefinedIn != nullptr && Sym->DefinedIn->Index >= SHN_LORESERVE)
+ SectionIndexTable->addIndex(Sym->DefinedIn->Index);
+ else
+ SectionIndexTable->addIndex(SHN_UNDEF);
+ }
+ }
// Add all of our strings to SymbolNames so that SymbolNames has the right
// size before layout is decided.
for (auto &Sym : Symbols)
@@ -538,12 +584,32 @@ template <class ELFT>
void ELFBuilder<ELFT>::initSymbolTable(SymbolTableSection *SymTab) {
const Elf_Shdr &Shdr = *unwrapOrError(ElfFile.getSection(SymTab->Index));
StringRef StrTabData = unwrapOrError(ElfFile.getStringTableForSymtab(Shdr));
+ ArrayRef<Elf_Word> ShndxData;
- for (const auto &Sym : unwrapOrError(ElfFile.symbols(&Shdr))) {
+ auto Symbols = unwrapOrError(ElfFile.symbols(&Shdr));
+ for (const auto &Sym : Symbols) {
SectionBase *DefSection = nullptr;
StringRef Name = unwrapOrError(Sym.getName(StrTabData));
- if (Sym.st_shndx >= SHN_LORESERVE) {
+ if (Sym.st_shndx == SHN_XINDEX) {
+ if (SymTab->getShndxTable() == nullptr)
+ error("Symbol '" + Name +
+ "' has index SHN_XINDEX but no SHT_SYMTAB_SHNDX section exists.");
+ if (ShndxData.data() == nullptr) {
+ const Elf_Shdr &ShndxSec =
+ *unwrapOrError(ElfFile.getSection(SymTab->getShndxTable()->Index));
+ ShndxData = unwrapOrError(
+ ElfFile.template getSectionContentsAsArray<Elf_Word>(&ShndxSec));
+ if (ShndxData.size() != Symbols.size())
+ error("Symbol section index table does not have the same number of "
+ "entries as the symbol table.");
+ }
+ auto Index = ShndxData[&Sym - Symbols.begin()];
+ DefSection = Obj.sections().getSection(
+ Index,
+ "Symbol '" + Name + "' is defined in invalid section with index " +
+ Twine(Index));
+ } else if (Sym.st_shndx >= SHN_LORESERVE) {
if (!isValidReservedSectionIndex(Sym.st_shndx, Obj.Machine)) {
error(
"Symbol '" + Name +
@@ -583,14 +649,14 @@ void initRelocations(RelocationSection *Relocs, SymbolTableSection *SymbolTable,
}
}
-SectionBase *SectionTableRef::getSection(uint16_t Index, Twine ErrMsg) {
+SectionBase *SectionTableRef::getSection(uint32_t Index, Twine ErrMsg) {
if (Index == SHN_UNDEF || Index > Sections.size())
error(ErrMsg);
return Sections[Index - 1].get();
}
template <class T>
-T *SectionTableRef::getSectionOfType(uint16_t Index, Twine IndexErrMsg,
+T *SectionTableRef::getSectionOfType(uint32_t Index, Twine IndexErrMsg,
Twine TypeErrMsg) {
if (T *Sec = dyn_cast<T>(getSection(Index, IndexErrMsg)))
return Sec;
@@ -634,6 +700,11 @@ SectionBase &ELFBuilder<ELFT>::makeSection(const Elf_Shdr &Shdr) {
Obj.SymbolTable = &SymTab;
return SymTab;
}
+ case SHT_SYMTAB_SHNDX: {
+ auto &ShndxSection = Obj.addSection<SectionIndexSection>();
+ Obj.SectionIndexTable = &ShndxSection;
+ return ShndxSection;
+ }
case SHT_NOBITS:
return Obj.addSection<Section>(Data);
default:
@@ -664,6 +735,10 @@ template <class ELFT> void ELFBuilder<ELFT>::readSectionHeaders() {
Sec.Index = Index++;
}
+ // If we have a SectionIndexTable we need to initialize it before the symbol
+ // table because the symbol table will need it to properly read in symbols.
+ if (Obj.SectionIndexTable)
+ Obj.SectionIndexTable->initialize(Obj.sections());
// Now that all of the sections have been added we can fill out some extra
// details about symbol tables. We need the symbol table filled out before
// any relocations.
@@ -704,12 +779,16 @@ template <class ELFT> void ELFBuilder<ELFT>::build() {
readSectionHeaders();
readProgramHeaders();
+ uint32_t ShstrIndex = Ehdr.e_shstrndx;
+ if (ShstrIndex == SHN_XINDEX)
+ ShstrIndex = unwrapOrError(ElfFile.getSection(0))->sh_link;
+
Obj.SectionNames =
Obj.sections().template getSectionOfType<StringTableSection>(
- Ehdr.e_shstrndx,
- "e_shstrndx field value " + Twine(Ehdr.e_shstrndx) +
+ ShstrIndex,
+ "e_shstrndx field value " + Twine(ShstrIndex) +
" in elf header " + " is invalid",
- "e_shstrndx field value " + Twine(Ehdr.e_shstrndx) +
+ "e_shstrndx field value " + Twine(ShstrIndex) +
" in elf header " + " is not a string table");
}
@@ -780,8 +859,27 @@ template <class ELFT> void ELFWriter<ELFT>::writeEhdr() {
Ehdr.e_shentsize = sizeof(Elf_Shdr);
if (WriteSectionHeaders) {
Ehdr.e_shoff = Obj.SHOffset;
- Ehdr.e_shnum = size(Obj.sections()) + 1;
- Ehdr.e_shstrndx = Obj.SectionNames->Index;
+ // """
+ // If the number of sections is greater than or equal to
+ // SHN_LORESERVE (0xff00), this member has the value zero and the actual
+ // number of section header table entries is contained in the sh_size field
+ // of the section header at index 0.
+ // """
+ auto Shnum = size(Obj.sections()) + 1;
+ if (Shnum >= SHN_LORESERVE)
+ Ehdr.e_shnum = 0;
+ else
+ Ehdr.e_shnum = Shnum;
+ // """
+ // If the section name string table section index is greater than or equal
+ // to SHN_LORESERVE (0xff00), this member has the value SHN_XINDEX (0xffff)
+ // and the actual index of the section name string table section is
+ // contained in the sh_link field of the section header at index 0.
+ // """
+ if (Obj.SectionNames->Index >= SHN_LORESERVE)
+ Ehdr.e_shstrndx = SHN_XINDEX;
+ else
+ Ehdr.e_shstrndx = Obj.SectionNames->Index;
} else {
Ehdr.e_shoff = 0;
Ehdr.e_shnum = 0;
@@ -804,8 +902,17 @@ template <class ELFT> void ELFWriter<ELFT>::writeShdrs() {
Shdr.sh_flags = 0;
Shdr.sh_addr = 0;
Shdr.sh_offset = 0;
- Shdr.sh_size = 0;
- Shdr.sh_link = 0;
+ // See writeEhdr for why we do this.
+ auto Shnum = size(Obj.sections()) + 1;
+ if (Shnum >= SHN_LORESERVE) {
+ Shdr.sh_size = Shnum;
+ } else
+ Shdr.sh_size = 0;
+ // See writeEhdr for why we do this.
+ if (Obj.SectionNames != nullptr && Obj.SectionNames->Index >= SHN_LORESERVE) {
+ Shdr.sh_link = Obj.SectionNames->Index;
+ } else
+ Shdr.sh_link = 0;
Shdr.sh_info = 0;
Shdr.sh_addralign = 0;
Shdr.sh_entsize = 0;
@@ -833,9 +940,10 @@ void Object::removeSections(std::function<bool(const SectionBase &)> ToRemove) {
});
if (SymbolTable != nullptr && ToRemove(*SymbolTable))
SymbolTable = nullptr;
- if (SectionNames != nullptr && ToRemove(*SectionNames)) {
+ if (SectionNames != nullptr && ToRemove(*SectionNames))
SectionNames = nullptr;
- }
+ if (SectionIndexTable != nullptr && ToRemove(*SectionIndexTable))
+ SectionIndexTable = nullptr;
// Now make sure there are no remaining references to the sections that will
// be removed. Sometimes it is impossible to remove a reference so we emit
// an error here instead.
@@ -997,16 +1105,57 @@ template <class ELFT> void ELFWriter<ELFT>::finalize() {
error("Cannot write section header table because section header string "
"table was removed.");
- // Make sure we add the names of all the sections.
+ Obj.sortSections();
+ // We need to assign indexes before we perform layout because we need to know
+ // if we need large indexes or not. We can assign indexes first and check as
+ // we go to see if we will actully need large indexes.
+ bool NeedsLargeIndexes = false;
+ if (size(Obj.sections()) >= SHN_LORESERVE) {
+ uint64_t Index = SHN_LORESERVE;
+ auto Sections = Obj.sections();
+ auto LargeIndexSections =
+ make_range(Sections.begin() + SHN_LORESERVE, Sections.end());
+ for (auto &Sec : LargeIndexSections) {
+ Sec.Index = Index++;
+ if (Sec.HasSymbol) {
+ NeedsLargeIndexes = true;
+ break;
+ }
+ }
+ // TODO: handle case where only one section needs the large index table but
+ // only needs it because the large index table hasn't been removed yet.
+ }
+
+ if (NeedsLargeIndexes) {
+ // This means we definitely need to have a section index table but if
+ // already have one then we should use it instead of making a new one.
+ if (Obj.SymbolTable != nullptr && Obj.SectionIndexTable == nullptr) {
+ auto &Shndx = Obj.addSection<SectionIndexSection>();
+ Obj.SymbolTable->setShndxTable(&Shndx);
+ Shndx.setSymTab(Obj.SymbolTable);
+ }
+ } else {
+ // Since we don't need SectionIndexTable we should remove it and all
+ // references to it.
+ if (Obj.SectionIndexTable != nullptr) {
+ Obj.removeSections(
+ [](const SectionBase &Sec) { return Sec.Type == SHT_SYMTAB_SHNDX; });
+ }
+ }
+
+ // Make sure we add the names of all the sections. Importantly this must be
+ // done after we decide to add or remove SectionIndexes.
if (Obj.SectionNames != nullptr)
for (const auto &Section : Obj.sections()) {
Obj.SectionNames->addString(Section.Name);
}
- // Make sure we add the names of all the symbols.
+
+ // The symbol table does not update all other sections on update. For
+ // instance symbol names are not added as new symbols are added. This means
+ // that some sections, like .strtab, don't yet have their final size.
if (Obj.SymbolTable != nullptr)
- Obj.SymbolTable->addSymbolNames();
+ Obj.SymbolTable->prepareForLayout();
- Obj.sortSections();
assignOffsets();
// Finalize SectionNames first so that we can assign name indexes.
diff --git a/llvm/tools/llvm-objcopy/Object.h b/llvm/tools/llvm-objcopy/Object.h
index 27beafc0ce6..5b99b8b2be2 100644
--- a/llvm/tools/llvm-objcopy/Object.h
+++ b/llvm/tools/llvm-objcopy/Object.h
@@ -35,6 +35,7 @@ class SymbolTableSection;
class RelocationSection;
class DynamicRelocationSection;
class GnuDebugLinkSection;
+class SectionIndexSection;
class Segment;
class Object;
@@ -52,10 +53,10 @@ public:
iterator begin() { return iterator(Sections.data()); }
iterator end() { return iterator(Sections.data() + Sections.size()); }
- SectionBase *getSection(uint16_t Index, Twine ErrMsg);
+ SectionBase *getSection(uint32_t Index, Twine ErrMsg);
template <class T>
- T *getSectionOfType(uint16_t Index, Twine IndexErrMsg, Twine TypeErrMsg);
+ T *getSectionOfType(uint32_t Index, Twine IndexErrMsg, Twine TypeErrMsg);
};
enum ElfType { ELFT_ELF32LE, ELFT_ELF64LE, ELFT_ELF32BE, ELFT_ELF64BE };
@@ -71,6 +72,7 @@ public:
virtual void visit(const RelocationSection &Sec) = 0;
virtual void visit(const DynamicRelocationSection &Sec) = 0;
virtual void visit(const GnuDebugLinkSection &Sec) = 0;
+ virtual void visit(const SectionIndexSection &Sec) = 0;
};
class SectionWriter : public SectionVisitor {
@@ -87,6 +89,7 @@ public:
virtual void visit(const SymbolTableSection &Sec) override = 0;
virtual void visit(const RelocationSection &Sec) override = 0;
virtual void visit(const GnuDebugLinkSection &Sec) override = 0;
+ virtual void visit(const SectionIndexSection &Sec) override = 0;
SectionWriter(FileOutputBuffer &Buf) : Out(Buf) {}
};
@@ -102,6 +105,7 @@ public:
void visit(const SymbolTableSection &Sec) override;
void visit(const RelocationSection &Sec) override;
void visit(const GnuDebugLinkSection &Sec) override;
+ void visit(const SectionIndexSection &Sec) override;
ELFSectionWriter(FileOutputBuffer &Buf) : SectionWriter(Buf) {}
};
@@ -117,6 +121,7 @@ public:
void visit(const SymbolTableSection &Sec) override;
void visit(const RelocationSection &Sec) override;
void visit(const GnuDebugLinkSection &Sec) override;
+ void visit(const SectionIndexSection &Sec) override;
BinarySectionWriter(FileOutputBuffer &Buf) : SectionWriter(Buf) {}
};
@@ -187,6 +192,7 @@ public:
uint64_t HeaderOffset;
uint64_t OriginalOffset;
uint32_t Index;
+ bool HasSymbol = false;
uint64_t Addr = 0;
uint64_t Align = 1;
@@ -323,6 +329,7 @@ enum SymbolShndxType {
SYMBOL_HEXAGON_SCOMMON_2 = ELF::SHN_HEXAGON_SCOMMON_2,
SYMBOL_HEXAGON_SCOMMON_4 = ELF::SHN_HEXAGON_SCOMMON_4,
SYMBOL_HEXAGON_SCOMMON_8 = ELF::SHN_HEXAGON_SCOMMON_8,
+ SYMBOL_XINDEX = ELF::SHN_XINDEX,
};
struct Symbol {
@@ -340,6 +347,33 @@ struct Symbol {
uint16_t getShndx() const;
};
+class SectionIndexSection : public SectionBase {
+ MAKE_SEC_WRITER_FRIEND
+
+private:
+ std::vector<uint32_t> Indexes;
+ SymbolTableSection *Symbols;
+
+public:
+ virtual ~SectionIndexSection() {}
+ void addIndex(uint32_t Index) {
+ Indexes.push_back(Index);
+ Size += 4;
+ }
+ void setSymTab(SymbolTableSection *SymTab) { Symbols = SymTab; }
+ void initialize(SectionTableRef SecTable) override;
+ void finalize() override;
+ void accept(SectionVisitor &Visitor) const override;
+
+ SectionIndexSection() {
+ Name = ".symtab_shndx";
+ OriginalOffset = std::numeric_limits<uint64_t>::max();
+ Align = 4;
+ EntrySize = 4;
+ Type = ELF::SHT_SYMTAB_SHNDX;
+ }
+};
+
class SymbolTableSection : public SectionBase {
MAKE_SEC_WRITER_FRIEND
@@ -348,6 +382,7 @@ class SymbolTableSection : public SectionBase {
protected:
std::vector<std::unique_ptr<Symbol>> Symbols;
StringTableSection *SymbolNames = nullptr;
+ SectionIndexSection *SectionIndexTable = nullptr;
using SymPtr = std::unique_ptr<Symbol>;
@@ -355,7 +390,9 @@ public:
void addSymbol(StringRef Name, uint8_t Bind, uint8_t Type,
SectionBase *DefinedIn, uint64_t Value, uint8_t Visibility,
uint16_t Shndx, uint64_t Sz);
- void addSymbolNames();
+ void prepareForLayout();
+ void setShndxTable(SectionIndexSection *ShndxTable) { SectionIndexTable = ShndxTable; }
+ const SectionBase *getShndxTable() const { return SectionIndexTable; }
const SectionBase *getStrTab() const { return SymbolNames; }
const Symbol *getSymbolByIndex(uint32_t Index) const;
void removeSectionReferences(const SectionBase *Sec) override;
@@ -516,6 +553,7 @@ private:
using Elf_Addr = typename ELFT::Addr;
using Elf_Shdr = typename ELFT::Shdr;
using Elf_Ehdr = typename ELFT::Ehdr;
+ using Elf_Word = typename ELFT::Word;
const ELFFile<ELFT> &ElfFile;
Object &Obj;
@@ -581,6 +619,7 @@ public:
StringTableSection *SectionNames = nullptr;
SymbolTableSection *SymbolTable = nullptr;
+ SectionIndexSection *SectionIndexTable = nullptr;
Object(std::shared_ptr<MemoryBuffer> Data) : OwnedData(Data) {}
virtual ~Object() = default;
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