path: root/gold/output.cc

// output.cc -- manage the output file for gold

#include "gold.h"

#include <cstdlib>
#include <cerrno>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <algorithm>

#include "object.h"
#include "output.h"

namespace gold
{

// Output_data methods.

Output_data::~Output_data()
{
}

// Set the address and offset.

void
Output_data::set_address(uint64_t addr, off_t off)
{
  this->address_ = addr;
  this->offset_ = off;

  // Let the child class know.
  this->do_set_address(addr, off);
}

// Return the default alignment for a size--32 or 64.

uint64_t
Output_data::default_alignment(int size)
{
  if (size == 32)
    return 4;
  else if (size == 64)
    return 8;
  else
    abort();
}

// Output_data_const methods.

void
Output_data_const::do_write(Output_file* output)
{
  output->write(this->offset(), data_.data(), data_.size());
}

// Output_section_header methods.  This currently assumes that the
// segment and section lists are complete at construction time.

Output_section_headers::Output_section_headers(
    int size,
    bool big_endian,
    const Layout::Segment_list& segment_list,
    const Layout::Section_list& section_list,
    const Stringpool* secnamepool)
  : size_(size),
    big_endian_(big_endian),
    segment_list_(segment_list),
    section_list_(section_list),
    secnamepool_(secnamepool)
{
  // Count all the sections.  Start with 1 for the null section.
  off_t count = 1;
  for (Layout::Segment_list::const_iterator p = segment_list.begin();
       p != segment_list.end();
       ++p)
    count += (*p)->output_section_count();
  count += section_list.size();

  int shdr_size;
  if (size == 32)
    shdr_size = elfcpp::Elf_sizes<32>::shdr_size;
  else if (size == 64)
    shdr_size = elfcpp::Elf_sizes<64>::shdr_size;
  else
    abort();

  this->set_data_size(count * shdr_size);
}

// Write out the section headers.

void
Output_section_headers::do_write(Output_file* of)
{
  if (this->size_ == 32)
    {
      if (this->big_endian_)
	this->do_sized_write<32, true>(of);
      else
	this->do_sized_write<32, false>(of);
    }
  else if (this->size_ == 64)
    {
      if (this->big_endian_)
	this->do_sized_write<64, true>(of);
      else
	this->do_sized_write<64, false>(of);
    }
  else
    abort();
}

template<int size, bool big_endian>
void
Output_section_headers::do_sized_write(Output_file* of)
{
  off_t all_shdrs_size = this->data_size();
  unsigned char* view = of->get_output_view(this->offset(), all_shdrs_size);

  const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
  unsigned char* v = view;

  {
    typename elfcpp::Shdr_write<size, big_endian> oshdr(v);
    oshdr.put_sh_name(0);
    oshdr.put_sh_type(elfcpp::SHT_NULL);
    oshdr.put_sh_flags(0);
    oshdr.put_sh_addr(0);
    oshdr.put_sh_offset(0);
    oshdr.put_sh_size(0);
    oshdr.put_sh_link(0);
    oshdr.put_sh_info(0);
    oshdr.put_sh_addralign(0);
    oshdr.put_sh_entsize(0);
  }

  v += shdr_size;

  for (Layout::Segment_list::const_iterator p = this->segment_list_.begin();
       p != this->segment_list_.end();
       ++p)
    v = (*p)->write_section_headers<size, big_endian>(this->secnamepool_, v);
  for (Layout::Section_list::const_iterator p = this->section_list_.begin();
       p != this->section_list_.end();
       ++p)
    {
      elfcpp::Shdr_write<size, big_endian> oshdr(v);
      (*p)->write_header(this->secnamepool_, &oshdr);
      v += shdr_size;
    }

  of->write_output_view(this->offset(), all_shdrs_size, view);
}

// Output_segment_header methods.

Output_segment_headers::Output_segment_headers(
    int size,
    bool big_endian,
    const Layout::Segment_list& segment_list)
  : size_(size), big_endian_(big_endian), segment_list_(segment_list)
{
  int phdr_size;
  if (size == 32)
    phdr_size = elfcpp::Elf_sizes<32>::phdr_size;
  else if (size == 64)
    phdr_size = elfcpp::Elf_sizes<64>::phdr_size;
  else
    abort();

  this->set_data_size(segment_list.size() * phdr_size);
}

void
Output_segment_headers::do_write(Output_file* of)
{
  if (this->size_ == 32)
    {
      if (this->big_endian_)
	this->do_sized_write<32, true>(of);
      else
	this->do_sized_write<32, false>(of);
    }
  else if (this->size_ == 64)
    {
      if (this->big_endian_)
	this->do_sized_write<64, true>(of);
      else
	this->do_sized_write<64, false>(of);
    }
  else
    abort();
}

template<int size, bool big_endian>
void
Output_segment_headers::do_sized_write(Output_file* of)
{
  const int phdr_size = elfcpp::Elf_sizes<size>::phdr_size;
  off_t all_phdrs_size = this->segment_list_.size() * phdr_size;
  unsigned char* view = of->get_output_view(this->offset(),
					    all_phdrs_size);
  unsigned char* v = view;
  for (Layout::Segment_list::const_iterator p = this->segment_list_.begin();
       p != this->segment_list_.end();
       ++p)
    {
      elfcpp::Phdr_write<size, big_endian> ophdr(v);
      (*p)->write_header(&ophdr);
      v += phdr_size;
    }

  of->write_output_view(this->offset(), all_phdrs_size, view);
}

// Output_file_header methods.

Output_file_header::Output_file_header(int size,
				       bool big_endian,
				       const General_options& options,
				       const Target* target,
				       const Symbol_table* symtab,
				       const Output_segment_headers* osh)
  : size_(size),
    big_endian_(big_endian),
    options_(options),
    target_(target),
    symtab_(symtab),
    segment_header_(osh),
    section_header_(NULL),
    shstrtab_(NULL)
{
  int ehdr_size;
  if (size == 32)
    ehdr_size = elfcpp::Elf_sizes<32>::ehdr_size;
  else if (size == 64)
    ehdr_size = elfcpp::Elf_sizes<64>::ehdr_size;
  else
    abort();

  this->set_data_size(ehdr_size);
}

// Set the section table information for a file header.

void
Output_file_header::set_section_info(const Output_section_headers* shdrs,
				     const Output_section* shstrtab)
{
  this->section_header_ = shdrs;
  this->shstrtab_ = shstrtab;
}

// Write out the file header.

void
Output_file_header::do_write(Output_file* of)
{
  if (this->size_ == 32)
    {
      if (this->big_endian_)
	this->do_sized_write<32, true>(of);
      else
	this->do_sized_write<32, false>(of);
    }
  else if (this->size_ == 64)
    {
      if (this->big_endian_)
	this->do_sized_write<64, true>(of);
      else
	this->do_sized_write<64, false>(of);
    }
  else
    abort();
}

// Write out the file header with appropriate size and endianess.

template<int size, bool big_endian>
void
Output_file_header::do_sized_write(Output_file* of)
{
  assert(this->offset() == 0);

  int ehdr_size = elfcpp::Elf_sizes<size>::ehdr_size;
  unsigned char* view = of->get_output_view(0, ehdr_size);
  elfcpp::Ehdr_write<size, big_endian> oehdr(view);

  unsigned char e_ident[elfcpp::EI_NIDENT];
  memset(e_ident, 0, elfcpp::EI_NIDENT);
  e_ident[elfcpp::EI_MAG0] = elfcpp::ELFMAG0;
  e_ident[elfcpp::EI_MAG1] = elfcpp::ELFMAG1;
  e_ident[elfcpp::EI_MAG2] = elfcpp::ELFMAG2;
  e_ident[elfcpp::EI_MAG3] = elfcpp::ELFMAG3;
  if (size == 32)
    e_ident[elfcpp::EI_CLASS] = elfcpp::ELFCLASS32;
  else if (size == 64)
    e_ident[elfcpp::EI_CLASS] = elfcpp::ELFCLASS64;
  else
    abort();
  e_ident[elfcpp::EI_DATA] = (big_endian
			      ? elfcpp::ELFDATA2MSB
			      : elfcpp::ELFDATA2LSB);
  e_ident[elfcpp::EI_VERSION] = elfcpp::EV_CURRENT;
  // FIXME: Some targets may need to set EI_OSABI and EI_ABIVERSION.
  oehdr.put_e_ident(e_ident);

  elfcpp::ET e_type;
  // FIXME: ET_DYN.
  if (this->options_.is_relocatable())
    e_type = elfcpp::ET_REL;
  else
    e_type = elfcpp::ET_EXEC;
  oehdr.put_e_type(e_type);

  oehdr.put_e_machine(this->target_->machine_code());
  oehdr.put_e_version(elfcpp::EV_CURRENT);

  Symbol* sym = this->symtab_->lookup("_start");
  typename Sized_symbol<size>::Value_type v;
  if (sym == NULL)
    v = 0;
  else
    {
      Sized_symbol<size>* ssym;
      ssym = this->symtab_->get_sized_symbol<size>(sym);
      v = ssym->value();
    }
  oehdr.put_e_entry(v);

  oehdr.put_e_phoff(this->segment_header_->offset());
  oehdr.put_e_shoff(this->section_header_->offset());

  // FIXME: The target needs to set the flags.
  oehdr.put_e_flags(0);

  oehdr.put_e_ehsize(elfcpp::Elf_sizes<size>::ehdr_size);
  oehdr.put_e_phentsize(elfcpp::Elf_sizes<size>::phdr_size);
  oehdr.put_e_phnum(this->segment_header_->data_size()
		     / elfcpp::Elf_sizes<size>::phdr_size);
  oehdr.put_e_shentsize(elfcpp::Elf_sizes<size>::shdr_size);
  oehdr.put_e_shnum(this->section_header_->data_size()
		     / elfcpp::Elf_sizes<size>::shdr_size);
  oehdr.put_e_shstrndx(this->shstrtab_->shndx());

  of->write_output_view(0, ehdr_size, view);
}

// Output_section methods.

// Construct an Output_section.  NAME will point into a Stringpool.

Output_section::Output_section(const char* name, elfcpp::Elf_Word type,
			       elfcpp::Elf_Xword flags, unsigned int shndx)
  : name_(name),
    addralign_(0),
    entsize_(0),
    link_(0),
    info_(0),
    type_(type),
    flags_(flags),
    shndx_(shndx)
{
}

Output_section::~Output_section()
{
}

// Add an input section to an Output_section.  We don't keep track of
// input sections for an Output_section.  Instead, each Object keeps
// track of the Output_section for each of its input sections.

template<int size, bool big_endian>
off_t
Output_section::add_input_section(Object* object, const char* secname,
				  const elfcpp::Shdr<size, big_endian>& shdr)
{
  elfcpp::Elf_Xword addralign = shdr.get_sh_addralign();
  if ((addralign & (addralign - 1)) != 0)
    {
      fprintf(stderr, _("%s: %s: invalid alignment %lu for section \"%s\"\n"),
	      program_name, object->name().c_str(),
	      static_cast<unsigned long>(addralign), secname);
      gold_exit(false);
    }

  if (addralign > this->addralign_)
    this->addralign_ = addralign;

  off_t ssize = this->data_size();
  ssize = (ssize + addralign - 1) &~ (addralign - 1);

  // SHF_TLS/SHT_NOBITS sections are handled specially: they are
  // treated as having no size and taking up no space.  We only use
  // the real size when setting the pt_memsz field of the PT_TLS
  // segment.
  if ((this->flags_ & elfcpp::SHF_TLS) == 0
      || this->type_ != elfcpp::SHT_NOBITS)
    this->set_data_size(ssize + shdr.get_sh_size());

  return ssize;
}

// Write the section header to *OSHDR.

template<int size, bool big_endian>
void
Output_section::write_header(const Stringpool* secnamepool,
			     elfcpp::Shdr_write<size, big_endian>* oshdr) const
{
  oshdr->put_sh_name(secnamepool->get_offset(this->name_));
  oshdr->put_sh_type(this->type_);
  oshdr->put_sh_flags(this->flags_);
  oshdr->put_sh_addr(this->address());
  oshdr->put_sh_offset(this->offset());
  oshdr->put_sh_size(this->data_size());
  oshdr->put_sh_link(this->link_);
  oshdr->put_sh_info(this->info_);
  oshdr->put_sh_addralign(this->addralign_);
  oshdr->put_sh_entsize(this->entsize_);
}

// Output_section_symtab methods.

Output_section_symtab::Output_section_symtab(const char* name, off_t size,
					     unsigned int shndx)
  : Output_section(name, elfcpp::SHT_SYMTAB, 0, shndx)
{
  this->set_data_size(size);
}

// Output_section_strtab methods.

Output_section_strtab::Output_section_strtab(const char* name,
					     Stringpool* contents,
					     unsigned int shndx)
  : Output_section(name, elfcpp::SHT_STRTAB, 0, shndx),
    contents_(contents)
{
  this->set_data_size(contents->get_strtab_size());
}

void
Output_section_strtab::do_write(Output_file* of)
{
  this->contents_->write(of, this->offset());
}

// Output segment methods.

Output_segment::Output_segment(elfcpp::Elf_Word type, elfcpp::Elf_Word flags)
  : output_data_(),
    output_bss_(),
    vaddr_(0),
    paddr_(0),
    memsz_(0),
    align_(0),
    offset_(0),
    filesz_(0),
    type_(type),
    flags_(flags)
{
}

// Add an Output_section to an Output_segment.

void
Output_segment::add_output_section(Output_section* os,
				   elfcpp::Elf_Word seg_flags)
{
  assert((os->flags() & elfcpp::SHF_ALLOC) != 0);

  // Update the segment flags and alignment.
  this->flags_ |= seg_flags;
  uint64_t addralign = os->addralign();
  if (addralign > this->align_)
    this->align_ = addralign;

  Output_segment::Output_data_list* pdl;
  if (os->type() == elfcpp::SHT_NOBITS)
    pdl = &this->output_bss_;
  else
    pdl = &this->output_data_;

  // So that PT_NOTE segments will work correctly, we need to ensure
  // that all SHT_NOTE sections are adjacent.  This will normally
  // happen automatically, because all the SHT_NOTE input sections
  // will wind up in the same output section.  However, it is possible
  // for multiple SHT_NOTE input sections to have different section
  // flags, and thus be in different output sections, but for the
  // different section flags to map into the same segment flags and
  // thus the same output segment.

  // Note that while there may be many input sections in an output
  // section, there are normally only a few output sections in an
  // output segment.  This loop is expected to be fast.

  if (os->type() == elfcpp::SHT_NOTE && !pdl->empty())
    {
      Layout::Data_list::iterator p = pdl->end();
      do
	{
	  --p;
	  if ((*p)->is_section_type(elfcpp::SHT_NOTE))
	    {
	      ++p;
	      pdl->insert(p, os);
	      return;
	    }
	}
      while (p != pdl->begin());
    }

  // Similarly, so that PT_TLS segments will work, we need to group
  // SHF_TLS sections.  An SHF_TLS/SHT_NOBITS section is a special
  // case: we group the SHF_TLS/SHT_NOBITS sections right after the
  // SHF_TLS/SHT_PROGBITS sections.  This lets us set up PT_TLS
  // correctly.
  if ((os->flags() & elfcpp::SHF_TLS) != 0 && !this->output_data_.empty())
    {
      pdl = &this->output_data_;
      bool nobits = os->type() == elfcpp::SHT_NOBITS;
      Layout::Data_list::iterator p = pdl->end();
      do
	{
	  --p;
	  if ((*p)->is_section_flag_set(elfcpp::SHF_TLS)
	      && (nobits || !(*p)->is_section_type(elfcpp::SHT_NOBITS)))
	    {
	      ++p;
	      pdl->insert(p, os);
	      return;
	    }
	}
      while (p != pdl->begin());
    }

  pdl->push_back(os);
}

// Add an Output_data (which is not an Output_section) to the start of
// a segment.

void
Output_segment::add_initial_output_data(Output_data* od)
{
  uint64_t addralign = od->addralign();
  if (addralign > this->align_)
    this->align_ = addralign;

  this->output_data_.push_front(od);
}

// Return the maximum alignment of the Output_data in Output_segment.
// We keep this up to date as we add Output_sections and Output_data.

uint64_t
Output_segment::max_data_align() const
{
  return this->align_;
}

// Set the section addresses for an Output_segment.  ADDR is the
// address and *POFF is the file offset.  Return the address of the
// immediately following segment.  Update *POFF.

uint64_t
Output_segment::set_section_addresses(uint64_t addr, off_t* poff)
{
  assert(this->type_ == elfcpp::PT_LOAD);

  this->vaddr_ = addr;
  this->paddr_ = addr;

  off_t orig_off = *poff;
  this->offset_ = orig_off;

  addr = this->set_section_list_addresses(&this->output_data_, addr, poff);
  this->filesz_ = *poff - orig_off;

  off_t off = *poff;

  uint64_t ret = this->set_section_list_addresses(&this->output_bss_, addr,
						  poff);
  this->memsz_ = *poff - orig_off;

  // Ignore the file offset adjustments made by the BSS Output_data
  // objects.
  *poff = off;

  return ret;
}

// Set the addresses in a list of Output_data structures.

uint64_t
Output_segment::set_section_list_addresses(Output_data_list* pdl,
					   uint64_t addr, off_t* poff)
{
  off_t off = *poff;

  for (Output_data_list::iterator p = pdl->begin();
       p != pdl->end();
       ++p)
    {
      uint64_t addralign = (*p)->addralign();
      addr = (addr + addralign - 1) & ~ (addralign - 1);
      off = (off + addralign - 1) & ~ (addralign - 1);
      (*p)->set_address(addr, off);

      uint64_t size = (*p)->data_size();
      addr += size;
      off += size;
    }

  *poff = off;
  return addr;
}

// For a non-PT_LOAD segment, set the offset from the sections, if
// any.

void
Output_segment::set_offset()
{
  assert(this->type_ != elfcpp::PT_LOAD);

  if (this->output_data_.empty() && this->output_bss_.empty())
    {
      this->vaddr_ = 0;
      this->paddr_ = 0;
      this->memsz_ = 0;
      this->align_ = 0;
      this->offset_ = 0;
      this->filesz_ = 0;
      return;
    }

  const Output_data* first;
  if (this->output_data_.empty())
    first = this->output_bss_.front();
  else
    first = this->output_data_.front();
  this->vaddr_ = first->address();
  this->paddr_ = this->vaddr_;
  this->offset_ = first->offset();

  if (this->output_data_.empty())
    this->filesz_ = 0;
  else
    {
      const Output_data* last_data = this->output_data_.back();
      this->filesz_ = (last_data->address()
		       + last_data->data_size()
		       - this->vaddr_);
    }

  const Output_data* last;
  if (this->output_bss_.empty())
    last = this->output_data_.back();
  else
    last = this->output_bss_.back();
  this->memsz_ = (last->address()
		  + last->data_size()
		  - this->vaddr_);

  // this->align_ was set as we added items.
}

// Return the number of Output_sections in an Output_segment.

unsigned int
Output_segment::output_section_count() const
{
  return (this->output_section_count_list(&this->output_data_)
	  + this->output_section_count_list(&this->output_bss_));
}

// Return the number of Output_sections in an Output_data_list.

unsigned int
Output_segment::output_section_count_list(const Output_data_list* pdl) const
{
  unsigned int count = 0;
  for (Output_data_list::const_iterator p = pdl->begin();
       p != pdl->end();
       ++p)
    {
      if ((*p)->is_section())
	++count;
    }
  return count;
}

// Write the segment data into *OPHDR.

template<int size, bool big_endian>
void
Output_segment::write_header(elfcpp::Phdr_write<size, big_endian>* ophdr) const
{
  ophdr->put_p_type(this->type_);
  ophdr->put_p_offset(this->offset_);
  ophdr->put_p_vaddr(this->vaddr_);
  ophdr->put_p_paddr(this->paddr_);
  ophdr->put_p_filesz(this->filesz_);
  ophdr->put_p_memsz(this->memsz_);
  ophdr->put_p_flags(this->flags_);
  ophdr->put_p_align(this->align_);
}

// Write the section headers into V.

template<int size, bool big_endian>
unsigned char*
Output_segment::write_section_headers(const Stringpool* secnamepool,
				      unsigned char* v) const
{
  v = this->write_section_headers_list<size, big_endian>(secnamepool,
							 &this->output_data_,
							 v);
  v = this->write_section_headers_list<size, big_endian>(secnamepool,
							 &this->output_bss_,
							 v);
  return v;
}

template<int size, bool big_endian>
unsigned char*
Output_segment::write_section_headers_list(const Stringpool* secnamepool,
					   const Output_data_list* pdl,
					   unsigned char* v) const
{
  const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
  for (Output_data_list::const_iterator p = pdl->begin();
       p != pdl->end();
       ++p)
    {
      if ((*p)->is_section())
	{
	  Output_section* ps = static_cast<const Output_section*>(*p);
	  elfcpp::Shdr_write<size, big_endian> oshdr(v);
	  ps->write_header(secnamepool, &oshdr);
	  v += shdr_size;
	}
    }
  return v;
}

// Output_file methods.

Output_file::Output_file(const General_options& options)
  : options_(options),
    name_(options.output_file_name()),
    o_(-1),
    file_size_(0),
    base_(NULL)
{
}

// Open the output file.

void
Output_file::open(off_t file_size)
{
  this->file_size_ = file_size;

  int mode = this->options_.is_relocatable() ? 0666 : 0777;
  int o = ::open(this->name_, O_RDWR | O_CREAT | O_TRUNC, mode);
  if (o < 0)
    {
      fprintf(stderr, _("%s: %s: open: %s\n"),
	      program_name, this->name_, strerror(errno));
      gold_exit(false);
    }
  this->o_ = o;

  // Write out one byte to make the file the right size.
  if (::lseek(o, file_size - 1, SEEK_SET) < 0)
    {
      fprintf(stderr, _("%s: %s: lseek: %s\n"),
	      program_name, this->name_, strerror(errno));
      gold_exit(false);
    }
  char b = 0;
  if (::write(o, &b, 1) != 1)
    {
      fprintf(stderr, _("%s: %s: write: %s\n"),
	      program_name, this->name_, strerror(errno));
      gold_exit(false);
    }

  // Map the file into memory.
  void* base = ::mmap(NULL, file_size, PROT_READ | PROT_WRITE,
		      MAP_SHARED, o, 0);
  if (base == MAP_FAILED)
    {
      fprintf(stderr, _("%s: %s: mmap: %s\n"),
	      program_name, this->name_, strerror(errno));
      gold_exit(false);
    }
  this->base_ = static_cast<unsigned char*>(base);
}

// Close the output file.

void
Output_file::close()
{
  if (::munmap(this->base_, this->file_size_) < 0)
    {
      fprintf(stderr, _("%s: %s: munmap: %s\n"),
	      program_name, this->name_, strerror(errno));
      gold_exit(false);
    }
  this->base_ = NULL;

  if (::close(this->o_) < 0)
    {
      fprintf(stderr, _("%s: %s: close: %s\n"),
	      program_name, this->name_, strerror(errno));
      gold_exit(false);
    }
  this->o_ = -1;
}

// Instantiate the templates we need.  We could use the configure
// script to restrict this to only the ones for implemented targets.

template
off_t
Output_section::add_input_section<32, false>(
    Object* object,
    const char* secname,
    const elfcpp::Shdr<32, false>& shdr);

template
off_t
Output_section::add_input_section<32, true>(
    Object* object,
    const char* secname,
    const elfcpp::Shdr<32, true>& shdr);

template
off_t
Output_section::add_input_section<64, false>(
    Object* object,
    const char* secname,
    const elfcpp::Shdr<64, false>& shdr);

template
off_t
Output_section::add_input_section<64, true>(
    Object* object,
    const char* secname,
    const elfcpp::Shdr<64, true>& shdr);

} // End namespace gold.