ELFHeaderChunks.h

//===- lib/ReaderWriter/ELF/ELFHeaderChunks.h -----------------------------===//
//
//                             The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef LLD_READER_WRITER_ELF_HEADER_CHUNKS_H_
#define LLD_READER_WRITER_ELF_HEADER_CHUNKS_H_

#include "llvm/Object/ELF.h"

#include "llvm/Support/Allocator.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FileOutputBuffer.h"

#include "ELFSegmentChunks.h"

/// \brief An ELFHeader represents the Elf[32/64]_Ehdr structure at the
///        start of an ELF executable file.
namespace lld {
namespace elf {

template<class ELFT>
class ELFHeader : public Chunk<ELFT> {
public:
  typedef llvm::object::Elf_Ehdr_Impl<ELFT> Elf_Ehdr;

  ELFHeader();

  void e_ident(int I, unsigned char C) { _eh.e_ident[I] = C; }
  void e_type(uint16_t type)           { _eh.e_type = type; }
  void e_machine(uint16_t machine)     { _eh.e_machine = machine; }
  void e_version(uint32_t version)     { _eh.e_version = version; }
  void e_entry(int64_t entry)         { _eh.e_entry = entry; }
  void e_phoff(int64_t phoff)         { _eh.e_phoff = phoff; }
  void e_shoff(int64_t shoff)         { _eh.e_shoff = shoff; }
  void e_flags(uint32_t flags)         { _eh.e_flags = flags; }
  void e_ehsize(uint16_t ehsize)       { _eh.e_ehsize = ehsize; }
  void e_phentsize(uint16_t phentsize) { _eh.e_phentsize = phentsize; }
  void e_phnum(uint16_t phnum)         { _eh.e_phnum = phnum; }
  void e_shentsize(uint16_t shentsize) { _eh.e_shentsize = shentsize; }
  void e_shnum(uint16_t shnum)         { _eh.e_shnum = shnum; }
  void e_shstrndx(uint16_t shstrndx)   { _eh.e_shstrndx = shstrndx; }
  uint64_t  fileSize()                 { return sizeof (Elf_Ehdr); }

  static inline bool classof(const Chunk<ELFT> *c) {
    return c->Kind() == Chunk<ELFT>::K_ELFHeader;
  }

  void write(ELFWriter *writer, llvm::FileOutputBuffer &buffer);

  void finalize() { }

private:
  Elf_Ehdr _eh;
};

template<class ELFT>
ELFHeader<ELFT>::ELFHeader()
: Chunk<ELFT>("elfhdr", Chunk<ELFT>::K_ELFHeader) {
  this->_align2 = ELFT::Is64Bits ? 8 : 4;
  this->_fsize = sizeof(Elf_Ehdr);
  this->_msize = sizeof(Elf_Ehdr);
  memset(_eh.e_ident, 0, llvm::ELF::EI_NIDENT);
  e_ident(llvm::ELF::EI_MAG0, 0x7f);
  e_ident(llvm::ELF::EI_MAG1, 'E');
  e_ident(llvm::ELF::EI_MAG2, 'L');
  e_ident(llvm::ELF::EI_MAG3, 'F');
  e_ehsize(sizeof(Elf_Ehdr));
  e_flags(2);
}

template <class ELFT>
void ELFHeader<ELFT>::write(ELFWriter *writer, llvm::FileOutputBuffer &buffer) {
  uint8_t *chunkBuffer = buffer.getBufferStart();
  uint8_t *atomContent = chunkBuffer + this->fileOffset();
  memcpy(atomContent, &_eh, fileSize());
}

/// \brief An ELFProgramHeader represents the Elf[32/64]_Phdr structure at the
///        start of an ELF executable file.
template<class ELFT>
class ELFProgramHeader : public Chunk<ELFT> {
public:
  typedef llvm::object::Elf_Phdr_Impl<ELFT> Elf_Phdr;
  typedef typename std::vector<Elf_Phdr *>::iterator PhIterT;

  /// \brief Find a program header entry, given the type of entry that
  /// we are looking for
  class FindPhdr {
  public:
    FindPhdr(uint64_t type, uint64_t flags, uint64_t flagsClear) 
             : _type(type)
             , _flags(flags)
             , _flagsClear(flagsClear)
    {}

    bool operator()(const Elf_Phdr *j) const { 
      return ((j->p_type == _type) &&
              ((j->p_flags & _flags) == _flags) &&
              (!(j->p_flags & _flagsClear)));
    }
  private:
    uint64_t _type;
    uint64_t _flags;
    uint64_t _flagsClear;
  };

  ELFProgramHeader()
  : Chunk<ELFT>("elfphdr", Chunk<ELFT>::K_ELFProgramHeader) {
    this->_align2 = ELFT::Is64Bits ? 8 : 4;
    resetProgramHeaders();
  }

  bool addSegment(Segment<ELFT> *segment);

  void resetProgramHeaders() {
    _phi = _ph.begin();
  }

  uint64_t  fileSize() {
    return sizeof(Elf_Phdr) * _ph.size();
  }

  static inline bool classof(const Chunk<ELFT> *c) {
    return c->Kind() == Chunk<ELFT>::K_ELFProgramHeader;
  }

  void write(ELFWriter *writer, llvm::FileOutputBuffer &buffer);

  /// \brief find a program header entry in the list of program headers
  PhIterT findProgramHeader(uint64_t type, uint64_t flags, uint64_t flagClear) {
    return std::find_if(_ph.begin(), _ph.end(), 
                        FindPhdr(type, flags, flagClear));
  }

  PhIterT begin() {
    return _ph.begin();
  }

  PhIterT end() {
    return _ph.end();
  }

  void finalize() { }

  int64_t entsize() {
    return sizeof(Elf_Phdr);
  }

  int64_t numHeaders() {
    return _ph.size();
  }

private:
  std::vector<Elf_Phdr *> _ph;
  PhIterT _phi;
  llvm::BumpPtrAllocator  _allocator;
};

template<class ELFT>
bool
ELFProgramHeader<ELFT>::addSegment(Segment<ELFT> *segment) {
  Elf_Phdr *phdr = nullptr;
  bool ret = false;

  for (auto slice : segment->slices()) {
    if (_phi == _ph.end()) {
      phdr = new(_allocator.Allocate<Elf_Phdr>()) Elf_Phdr;
      _ph.push_back(phdr);
      _phi = _ph.end();
      ret = true;
    } else {
      phdr = (*_phi);
      ++_phi;
    }
    phdr->p_type = segment->segmentType();
    phdr->p_offset = slice->fileOffset();
    phdr->p_vaddr = slice->virtualAddr();
    phdr->p_paddr = slice->virtualAddr();
    phdr->p_filesz = slice->fileSize();
    phdr->p_memsz = slice->memSize();
    phdr->p_flags = segment->flags();
    phdr->p_align = (phdr->p_type == llvm::ELF::PT_LOAD) ?
                     segment->pageSize() : slice->align2();
  }
  this->_fsize = fileSize();
  this->_msize = this->_fsize;

  return ret;
}

template <class ELFT>
void ELFProgramHeader<ELFT>::write(ELFWriter *writer,
                                   llvm::FileOutputBuffer &buffer) {
  uint8_t *chunkBuffer = buffer.getBufferStart();
  uint8_t *dest = chunkBuffer + this->fileOffset();
  for (auto phi : _ph) {
    memcpy(dest, phi, sizeof(Elf_Phdr));
    dest += sizeof(Elf_Phdr);
  }
}

/// \brief An ELFSectionHeader represents the Elf[32/64]_Shdr structure
/// at the end of the file
template<class ELFT>
class ELFSectionHeader : public Chunk<ELFT> {
public:
  typedef llvm::object::Elf_Shdr_Impl<ELFT> Elf_Shdr;

  ELFSectionHeader(int32_t order);

  void appendSection(MergedSections<ELFT> *section);
  
  void updateSection(Section<ELFT> *section);
  
  static inline bool classof(const Chunk<ELFT> *c) {
    return c->getChunkKind() == Chunk<ELFT>::K_ELFSectionHeader;
  }
  
  void setStringSection(ELFStringTable<ELFT> *s) {
    _stringSection = s;
  }

  void write(ELFWriter *writer, llvm::FileOutputBuffer &buffer);
  
  void finalize() { }
  
  inline uint16_t fileSize() {
    return sizeof(Elf_Shdr) * _sectionInfo.size();
  }

  inline int64_t entsize() {
    return sizeof(Elf_Shdr);
  }
  
  inline int64_t numHeaders() {
    return _sectionInfo.size();
  }

private:
  ELFStringTable<ELFT> *_stringSection;
  std::vector<Elf_Shdr*>                  _sectionInfo;
  llvm::BumpPtrAllocator                  _sectionAllocate;
};

template<class ELFT>
ELFSectionHeader<ELFT>::ELFSectionHeader(int32_t order) 
  : Chunk<ELFT>("shdr", Chunk<ELFT>::K_ELFSectionHeader) {
  this->_fsize = 0;
  this->_align2 = 8;
  this->setOrder(order);
  // The first element in the list is always NULL
  Elf_Shdr *nullshdr = new (_sectionAllocate.Allocate<Elf_Shdr>()) Elf_Shdr;
  ::memset(nullshdr, 0, sizeof (Elf_Shdr));
  _sectionInfo.push_back(nullshdr);
  this->_fsize += sizeof (Elf_Shdr);
}

template<class ELFT>
void 
ELFSectionHeader<ELFT>::appendSection(MergedSections<ELFT> *section) {
  Elf_Shdr *shdr = new (_sectionAllocate.Allocate<Elf_Shdr>()) Elf_Shdr;
  shdr->sh_name   = _stringSection->addString(section->name());
  shdr->sh_type   = section->type();
  shdr->sh_flags  = section->flags();
  shdr->sh_offset = section->fileOffset();
  shdr->sh_addr   = section->virtualAddr();
  shdr->sh_size   = section->memSize();
  shdr->sh_link   = section->link();
  shdr->sh_info   = section->shinfo();
  shdr->sh_addralign = section->align2();
  shdr->sh_entsize = section->entsize();
  _sectionInfo.push_back(shdr);
}

template<class ELFT>
void 
ELFSectionHeader<ELFT>::updateSection(Section<ELFT> *section) {
  Elf_Shdr *shdr = _sectionInfo[section->ordinal()];
  shdr->sh_type   = section->type();
  shdr->sh_flags  = section->flags();
  shdr->sh_offset = section->fileOffset();
  shdr->sh_addr   = section->virtualAddr();
  shdr->sh_size   = section->fileSize();
  shdr->sh_link   = section->link();
  shdr->sh_info   = section->shinfo();
  shdr->sh_addralign = section->align2();
  shdr->sh_entsize = section->entsize();
}

template <class ELFT>
void ELFSectionHeader<ELFT>::write(ELFWriter *writer,
                                   llvm::FileOutputBuffer &buffer) {
  uint8_t *chunkBuffer = buffer.getBufferStart();
  uint8_t *dest = chunkBuffer + this->fileOffset();
  for (auto shi : _sectionInfo) {
    memcpy(dest, shi, sizeof(Elf_Shdr));
    dest += sizeof(Elf_Shdr);
  }
  _stringSection->write(writer, buffer);
}

} // elf
} // lld

#endif // LLD_READER_WRITER_ELF_HEADER_CHUNKS_H_