llvm-project/lld/ELF/OutputSections.h

487 lines
16 KiB
C++

//===- OutputSections.h -----------------------------------------*- C++ -*-===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLD_ELF_OUTPUT_SECTIONS_H
#define LLD_ELF_OUTPUT_SECTIONS_H
#include "lld/Core/LLVM.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Object/ELF.h"
#include "Config.h"
#include <type_traits>
namespace lld {
namespace elf2 {
class SymbolBody;
template <class ELFT> class SymbolTable;
template <class ELFT> class SymbolTableSection;
template <class ELFT> class StringTableSection;
template <class ELFT> class EHInputSection;
template <class ELFT> class InputSection;
template <class ELFT> class InputSectionBase;
template <class ELFT> class MergeInputSection;
template <class ELFT> class MipsReginfoInputSection;
template <class ELFT> class OutputSection;
template <class ELFT> class ObjectFile;
template <class ELFT> class DefinedRegular;
// Flag to force GOT to be in output if we have relocations
// that relies on its address.
extern bool HasGotOffRel;
template <class ELFT>
static inline typename llvm::object::ELFFile<ELFT>::uintX_t
getAddend(const typename llvm::object::ELFFile<ELFT>::Elf_Rel &Rel) {
return 0;
}
template <class ELFT>
static inline typename llvm::object::ELFFile<ELFT>::uintX_t
getAddend(const typename llvm::object::ELFFile<ELFT>::Elf_Rela &Rel) {
return Rel.r_addend;
}
template <class ELFT>
typename llvm::object::ELFFile<ELFT>::uintX_t getSymVA(const SymbolBody &S);
template <class ELFT, bool IsRela>
typename llvm::object::ELFFile<ELFT>::uintX_t
getLocalRelTarget(const ObjectFile<ELFT> &File,
const llvm::object::Elf_Rel_Impl<ELFT, IsRela> &Rel,
typename llvm::object::ELFFile<ELFT>::uintX_t Addend);
bool canBePreempted(const SymbolBody *Body, bool NeedsGot);
template <class ELFT>
bool shouldKeepInSymtab(
const ObjectFile<ELFT> &File, StringRef Name,
const typename llvm::object::ELFFile<ELFT>::Elf_Sym &Sym);
// This represents a section in an output file.
// Different sub classes represent different types of sections. Some contain
// input sections, others are created by the linker.
// The writer creates multiple OutputSections and assign them unique,
// non-overlapping file offsets and VAs.
template <class ELFT> class OutputSectionBase {
public:
typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
OutputSectionBase(StringRef Name, uint32_t sh_type, uintX_t sh_flags);
void setVA(uintX_t VA) { Header.sh_addr = VA; }
uintX_t getVA() const { return Header.sh_addr; }
void setFileOffset(uintX_t Off) { Header.sh_offset = Off; }
void writeHeaderTo(Elf_Shdr *SHdr);
StringRef getName() { return Name; }
virtual void addSection(InputSectionBase<ELFT> *C) {}
unsigned SectionIndex;
// Returns the size of the section in the output file.
uintX_t getSize() const { return Header.sh_size; }
void setSize(uintX_t Val) { Header.sh_size = Val; }
uintX_t getFlags() { return Header.sh_flags; }
uintX_t getFileOff() { return Header.sh_offset; }
uintX_t getAlign() {
// The ELF spec states that a value of 0 means the section has no alignment
// constraits.
return std::max<uintX_t>(Header.sh_addralign, 1);
}
uint32_t getType() { return Header.sh_type; }
void updateAlign(uintX_t Align) {
if (Align > Header.sh_addralign)
Header.sh_addralign = Align;
}
virtual void finalize() {}
virtual void writeTo(uint8_t *Buf) = 0;
virtual ~OutputSectionBase() = default;
protected:
StringRef Name;
Elf_Shdr Header;
};
template <class ELFT> class GotSection final : public OutputSectionBase<ELFT> {
typedef OutputSectionBase<ELFT> Base;
typedef typename Base::uintX_t uintX_t;
public:
GotSection();
void finalize() override;
void writeTo(uint8_t *Buf) override;
void addEntry(SymbolBody *Sym);
bool addDynTlsEntry(SymbolBody *Sym);
bool addCurrentModuleTlsIndex();
bool empty() const { return Entries.empty(); }
uintX_t getEntryAddr(const SymbolBody &B) const;
uintX_t getGlobalDynAddr(const SymbolBody &B) const;
uintX_t getNumEntries() const { return Entries.size(); }
// Returns the symbol which corresponds to the first entry of the global part
// of GOT on MIPS platform. It is required to fill up MIPS-specific dynamic
// table properties.
// Returns nullptr if the global part is empty.
const SymbolBody *getMipsFirstGlobalEntry() const;
// Returns the number of entries in the local part of GOT including
// the number of reserved entries. This method is MIPS-specific.
unsigned getMipsLocalEntriesNum() const;
uint32_t getLocalTlsIndexVA() { return Base::getVA() + LocalTlsIndexOff; }
private:
std::vector<const SymbolBody *> Entries;
uint32_t LocalTlsIndexOff = -1;
};
template <class ELFT>
class GotPltSection final : public OutputSectionBase<ELFT> {
typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
public:
GotPltSection();
void finalize() override;
void writeTo(uint8_t *Buf) override;
void addEntry(SymbolBody *Sym);
bool empty() const;
uintX_t getEntryAddr(const SymbolBody &B) const;
private:
std::vector<const SymbolBody *> Entries;
};
template <class ELFT> class PltSection final : public OutputSectionBase<ELFT> {
typedef OutputSectionBase<ELFT> Base;
typedef typename Base::uintX_t uintX_t;
public:
PltSection();
void finalize() override;
void writeTo(uint8_t *Buf) override;
void addEntry(SymbolBody *Sym);
bool empty() const { return Entries.empty(); }
uintX_t getEntryAddr(const SymbolBody &B) const;
private:
std::vector<std::pair<const SymbolBody *, unsigned>> Entries;
};
template <class ELFT> struct DynamicReloc {
typedef typename llvm::object::ELFFile<ELFT>::Elf_Rel Elf_Rel;
InputSectionBase<ELFT> *C;
const Elf_Rel *RI;
};
template <class ELFT>
class SymbolTableSection final : public OutputSectionBase<ELFT> {
public:
typedef typename llvm::object::ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Sym Elf_Sym;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Sym_Range Elf_Sym_Range;
typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
SymbolTableSection(SymbolTable<ELFT> &Table,
StringTableSection<ELFT> &StrTabSec);
void finalize() override;
void writeTo(uint8_t *Buf) override;
void addLocalSymbol(StringRef Name);
void addSymbol(SymbolBody *Body);
StringTableSection<ELFT> &getStrTabSec() const { return StrTabSec; }
unsigned getNumSymbols() const { return NumVisible + 1; }
ArrayRef<SymbolBody *> getSymbols() const { return Symbols; }
private:
void writeLocalSymbols(uint8_t *&Buf);
void writeGlobalSymbols(uint8_t *Buf);
static uint8_t getSymbolBinding(SymbolBody *Body);
SymbolTable<ELFT> &Table;
StringTableSection<ELFT> &StrTabSec;
std::vector<SymbolBody *> Symbols;
unsigned NumVisible = 0;
unsigned NumLocals = 0;
};
template <class ELFT>
class RelocationSection final : public OutputSectionBase<ELFT> {
typedef typename llvm::object::ELFFile<ELFT>::Elf_Rel Elf_Rel;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Rela Elf_Rela;
typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
public:
RelocationSection(StringRef Name, bool IsRela);
void addReloc(const DynamicReloc<ELFT> &Reloc) { Relocs.push_back(Reloc); }
unsigned getRelocOffset();
void finalize() override;
void writeTo(uint8_t *Buf) override;
bool hasRelocs() const { return !Relocs.empty(); }
bool isRela() const { return IsRela; }
bool Static = false;
private:
bool applyTlsDynamicReloc(SymbolBody *Body, uint32_t Type, Elf_Rel *P,
Elf_Rel *N);
std::vector<DynamicReloc<ELFT>> Relocs;
const bool IsRela;
};
template <class ELFT>
class OutputSection final : public OutputSectionBase<ELFT> {
public:
typedef typename llvm::object::ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Sym Elf_Sym;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Rel Elf_Rel;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Rela Elf_Rela;
typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
OutputSection(StringRef Name, uint32_t sh_type, uintX_t sh_flags);
void addSection(InputSectionBase<ELFT> *C) override;
void writeTo(uint8_t *Buf) override;
private:
std::vector<InputSection<ELFT> *> Sections;
};
template <class ELFT>
class MergeOutputSection final : public OutputSectionBase<ELFT> {
typedef typename OutputSectionBase<ELFT>::uintX_t uintX_t;
bool shouldTailMerge() const;
public:
MergeOutputSection(StringRef Name, uint32_t sh_type, uintX_t sh_flags);
void addSection(InputSectionBase<ELFT> *S) override;
void writeTo(uint8_t *Buf) override;
unsigned getOffset(StringRef Val);
void finalize() override;
private:
llvm::StringTableBuilder Builder{llvm::StringTableBuilder::RAW};
};
// FDE or CIE
template <class ELFT> struct EHRegion {
typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
EHRegion(EHInputSection<ELFT> *S, unsigned Index);
StringRef data() const;
EHInputSection<ELFT> *S;
unsigned Index;
};
template <class ELFT> struct Cie : public EHRegion<ELFT> {
Cie(EHInputSection<ELFT> *S, unsigned Index);
std::vector<EHRegion<ELFT>> Fdes;
};
template <class ELFT>
class EHOutputSection final : public OutputSectionBase<ELFT> {
public:
typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Rel Elf_Rel;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Rela Elf_Rela;
EHOutputSection(StringRef Name, uint32_t sh_type, uintX_t sh_flags);
void writeTo(uint8_t *Buf) override;
template <bool IsRela>
void addSectionAux(
EHInputSection<ELFT> *S,
llvm::iterator_range<const llvm::object::Elf_Rel_Impl<ELFT, IsRela> *>
Rels);
void addSection(InputSectionBase<ELFT> *S) override;
private:
uintX_t readEntryLength(ArrayRef<uint8_t> D);
std::vector<EHInputSection<ELFT> *> Sections;
std::vector<Cie<ELFT>> Cies;
// Maps CIE content + personality to a index in Cies.
llvm::DenseMap<std::pair<StringRef, StringRef>, unsigned> CieMap;
};
template <class ELFT>
class InterpSection final : public OutputSectionBase<ELFT> {
public:
InterpSection();
void writeTo(uint8_t *Buf) override;
};
template <class ELFT>
class StringTableSection final : public OutputSectionBase<ELFT> {
public:
typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
StringTableSection(StringRef Name, bool Dynamic);
void reserve(StringRef S);
size_t addString(StringRef S);
void writeTo(uint8_t *Buf) override;
size_t getSize() const { return Used + Reserved; }
void finalize() override { this->Header.sh_size = getSize(); }
bool isDynamic() const { return Dynamic; }
private:
const bool Dynamic;
std::vector<StringRef> Strings;
size_t Used = 1; // ELF string tables start with a NUL byte, so 1.
size_t Reserved = 0;
};
template <class ELFT>
class HashTableSection final : public OutputSectionBase<ELFT> {
typedef typename llvm::object::ELFFile<ELFT>::Elf_Word Elf_Word;
public:
HashTableSection();
void finalize() override;
void writeTo(uint8_t *Buf) override;
};
// Outputs GNU Hash section. For detailed explanation see:
// https://blogs.oracle.com/ali/entry/gnu_hash_elf_sections
template <class ELFT>
class GnuHashTableSection final : public OutputSectionBase<ELFT> {
typedef typename llvm::object::ELFFile<ELFT>::Elf_Off Elf_Off;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Word Elf_Word;
typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
public:
GnuHashTableSection();
void finalize() override;
void writeTo(uint8_t *Buf) override;
// Adds symbols to the hash table.
// Sorts the input to satisfy GNU hash section requirements.
void addSymbols(std::vector<SymbolBody *> &Symbols);
private:
static unsigned calcNBuckets(unsigned NumHashed);
static unsigned calcMaskWords(unsigned NumHashed);
void writeHeader(uint8_t *&Buf);
void writeBloomFilter(uint8_t *&Buf);
void writeHashTable(uint8_t *Buf);
struct HashedSymbolData {
SymbolBody *Body;
uint32_t Hash;
};
std::vector<HashedSymbolData> HashedSymbols;
unsigned MaskWords;
unsigned NBuckets;
unsigned Shift2;
};
template <class ELFT>
class DynamicSection final : public OutputSectionBase<ELFT> {
typedef OutputSectionBase<ELFT> Base;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Dyn Elf_Dyn;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Rel Elf_Rel;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Rela Elf_Rela;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Sym Elf_Sym;
public:
DynamicSection(SymbolTable<ELFT> &SymTab);
void finalize() override;
void writeTo(uint8_t *Buf) override;
OutputSectionBase<ELFT> *PreInitArraySec = nullptr;
OutputSectionBase<ELFT> *InitArraySec = nullptr;
OutputSectionBase<ELFT> *FiniArraySec = nullptr;
private:
SymbolTable<ELFT> &SymTab;
const SymbolBody *InitSym = nullptr;
const SymbolBody *FiniSym = nullptr;
uint32_t DtFlags = 0;
uint32_t DtFlags1 = 0;
};
template <class ELFT>
class MipsReginfoOutputSection final : public OutputSectionBase<ELFT> {
typedef llvm::object::Elf_Mips_RegInfo<ELFT> Elf_Mips_RegInfo;
public:
MipsReginfoOutputSection();
void writeTo(uint8_t *Buf) override;
void addSection(InputSectionBase<ELFT> *S) override;
private:
uint32_t GprMask = 0;
};
inline uint64_t align(uint64_t Value, uint64_t Align) {
return llvm::RoundUpToAlignment(Value, Align);
}
// All output sections that are hadnled by the linker specially are
// globally accessible. Writer initializes them, so don't use them
// until Writer is initialized.
template <class ELFT> struct Out {
typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
typedef typename llvm::object::ELFFile<ELFT>::Elf_Phdr Elf_Phdr;
static DynamicSection<ELFT> *Dynamic;
static GnuHashTableSection<ELFT> *GnuHashTab;
static GotPltSection<ELFT> *GotPlt;
static GotSection<ELFT> *Got;
static HashTableSection<ELFT> *HashTab;
static InterpSection<ELFT> *Interp;
static OutputSection<ELFT> *Bss;
static OutputSection<ELFT> *MipsRldMap;
static OutputSectionBase<ELFT> *Opd;
static uint8_t *OpdBuf;
static PltSection<ELFT> *Plt;
static RelocationSection<ELFT> *RelaDyn;
static RelocationSection<ELFT> *RelaPlt;
static StringTableSection<ELFT> *DynStrTab;
static StringTableSection<ELFT> *ShStrTab;
static StringTableSection<ELFT> *StrTab;
static SymbolTableSection<ELFT> *DynSymTab;
static SymbolTableSection<ELFT> *SymTab;
static Elf_Phdr *TlsPhdr;
};
template <class ELFT> DynamicSection<ELFT> *Out<ELFT>::Dynamic;
template <class ELFT> GnuHashTableSection<ELFT> *Out<ELFT>::GnuHashTab;
template <class ELFT> GotPltSection<ELFT> *Out<ELFT>::GotPlt;
template <class ELFT> GotSection<ELFT> *Out<ELFT>::Got;
template <class ELFT> HashTableSection<ELFT> *Out<ELFT>::HashTab;
template <class ELFT> InterpSection<ELFT> *Out<ELFT>::Interp;
template <class ELFT> OutputSection<ELFT> *Out<ELFT>::Bss;
template <class ELFT> OutputSection<ELFT> *Out<ELFT>::MipsRldMap;
template <class ELFT> OutputSectionBase<ELFT> *Out<ELFT>::Opd;
template <class ELFT> uint8_t *Out<ELFT>::OpdBuf;
template <class ELFT> PltSection<ELFT> *Out<ELFT>::Plt;
template <class ELFT> RelocationSection<ELFT> *Out<ELFT>::RelaDyn;
template <class ELFT> RelocationSection<ELFT> *Out<ELFT>::RelaPlt;
template <class ELFT> StringTableSection<ELFT> *Out<ELFT>::DynStrTab;
template <class ELFT> StringTableSection<ELFT> *Out<ELFT>::ShStrTab;
template <class ELFT> StringTableSection<ELFT> *Out<ELFT>::StrTab;
template <class ELFT> SymbolTableSection<ELFT> *Out<ELFT>::DynSymTab;
template <class ELFT> SymbolTableSection<ELFT> *Out<ELFT>::SymTab;
template <class ELFT> typename Out<ELFT>::Elf_Phdr *Out<ELFT>::TlsPhdr;
} // namespace elf2
} // namespace lld
#endif // LLD_ELF_OUTPUT_SECTIONS_H