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Retro68/binutils/gold/layout.cc
Wolfgang Thaller 5d96d8025a add binutils-2.20.1
2012-03-26 21:18:29 +02:00

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// layout.cc -- lay out output file sections for gold
// Copyright 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.
// This file is part of gold.
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
// MA 02110-1301, USA.
#include "gold.h"
#include <cerrno>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <utility>
#include <fcntl.h>
#include <unistd.h>
#include "libiberty.h"
#include "md5.h"
#include "sha1.h"
#include "parameters.h"
#include "options.h"
#include "mapfile.h"
#include "script.h"
#include "script-sections.h"
#include "output.h"
#include "symtab.h"
#include "dynobj.h"
#include "ehframe.h"
#include "compressed_output.h"
#include "reduced_debug_output.h"
#include "reloc.h"
#include "descriptors.h"
#include "plugin.h"
#include "incremental.h"
#include "layout.h"
namespace gold
{
// Layout::Relaxation_debug_check methods.
// Check that sections and special data are in reset states.
// We do not save states for Output_sections and special Output_data.
// So we check that they have not assigned any addresses or offsets.
// clean_up_after_relaxation simply resets their addresses and offsets.
void
Layout::Relaxation_debug_check::check_output_data_for_reset_values(
const Layout::Section_list& sections,
const Layout::Data_list& special_outputs)
{
for(Layout::Section_list::const_iterator p = sections.begin();
p != sections.end();
++p)
gold_assert((*p)->address_and_file_offset_have_reset_values());
for(Layout::Data_list::const_iterator p = special_outputs.begin();
p != special_outputs.end();
++p)
gold_assert((*p)->address_and_file_offset_have_reset_values());
}
// Save information of SECTIONS for checking later.
void
Layout::Relaxation_debug_check::read_sections(
const Layout::Section_list& sections)
{
for(Layout::Section_list::const_iterator p = sections.begin();
p != sections.end();
++p)
{
Output_section* os = *p;
Section_info info;
info.output_section = os;
info.address = os->is_address_valid() ? os->address() : 0;
info.data_size = os->is_data_size_valid() ? os->data_size() : -1;
info.offset = os->is_offset_valid()? os->offset() : -1 ;
this->section_infos_.push_back(info);
}
}
// Verify SECTIONS using previously recorded information.
void
Layout::Relaxation_debug_check::verify_sections(
const Layout::Section_list& sections)
{
size_t i = 0;
for(Layout::Section_list::const_iterator p = sections.begin();
p != sections.end();
++p, ++i)
{
Output_section* os = *p;
uint64_t address = os->is_address_valid() ? os->address() : 0;
off_t data_size = os->is_data_size_valid() ? os->data_size() : -1;
off_t offset = os->is_offset_valid()? os->offset() : -1 ;
if (i >= this->section_infos_.size())
{
gold_fatal("Section_info of %s missing.\n", os->name());
}
const Section_info& info = this->section_infos_[i];
if (os != info.output_section)
gold_fatal("Section order changed. Expecting %s but see %s\n",
info.output_section->name(), os->name());
if (address != info.address
|| data_size != info.data_size
|| offset != info.offset)
gold_fatal("Section %s changed.\n", os->name());
}
}
// Layout_task_runner methods.
// Lay out the sections. This is called after all the input objects
// have been read.
void
Layout_task_runner::run(Workqueue* workqueue, const Task* task)
{
off_t file_size = this->layout_->finalize(this->input_objects_,
this->symtab_,
this->target_,
task);
// Now we know the final size of the output file and we know where
// each piece of information goes.
if (this->mapfile_ != NULL)
{
this->mapfile_->print_discarded_sections(this->input_objects_);
this->layout_->print_to_mapfile(this->mapfile_);
}
Output_file* of = new Output_file(parameters->options().output_file_name());
if (this->options_.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
of->set_is_temporary();
of->open(file_size);
// Queue up the final set of tasks.
gold::queue_final_tasks(this->options_, this->input_objects_,
this->symtab_, this->layout_, workqueue, of);
}
// Layout methods.
Layout::Layout(int number_of_input_files, Script_options* script_options)
: number_of_input_files_(number_of_input_files),
script_options_(script_options),
namepool_(),
sympool_(),
dynpool_(),
signatures_(),
section_name_map_(),
segment_list_(),
section_list_(),
unattached_section_list_(),
special_output_list_(),
section_headers_(NULL),
tls_segment_(NULL),
relro_segment_(NULL),
symtab_section_(NULL),
symtab_xindex_(NULL),
dynsym_section_(NULL),
dynsym_xindex_(NULL),
dynamic_section_(NULL),
dynamic_data_(NULL),
eh_frame_section_(NULL),
eh_frame_data_(NULL),
added_eh_frame_data_(false),
eh_frame_hdr_section_(NULL),
build_id_note_(NULL),
debug_abbrev_(NULL),
debug_info_(NULL),
group_signatures_(),
output_file_size_(-1),
sections_are_attached_(false),
input_requires_executable_stack_(false),
input_with_gnu_stack_note_(false),
input_without_gnu_stack_note_(false),
has_static_tls_(false),
any_postprocessing_sections_(false),
resized_signatures_(false),
have_stabstr_section_(false),
incremental_inputs_(NULL),
record_output_section_data_from_script_(false),
script_output_section_data_list_(),
segment_states_(NULL),
relaxation_debug_check_(NULL)
{
// Make space for more than enough segments for a typical file.
// This is just for efficiency--it's OK if we wind up needing more.
this->segment_list_.reserve(12);
// We expect two unattached Output_data objects: the file header and
// the segment headers.
this->special_output_list_.reserve(2);
// Initialize structure needed for an incremental build.
if (parameters->options().incremental())
this->incremental_inputs_ = new Incremental_inputs;
// The section name pool is worth optimizing in all cases, because
// it is small, but there are often overlaps due to .rel sections.
this->namepool_.set_optimize();
}
// Hash a key we use to look up an output section mapping.
size_t
Layout::Hash_key::operator()(const Layout::Key& k) const
{
return k.first + k.second.first + k.second.second;
}
// Returns whether the given section is in the list of
// debug-sections-used-by-some-version-of-gdb. Currently,
// we've checked versions of gdb up to and including 6.7.1.
static const char* gdb_sections[] =
{ ".debug_abbrev",
// ".debug_aranges", // not used by gdb as of 6.7.1
".debug_frame",
".debug_info",
".debug_line",
".debug_loc",
".debug_macinfo",
// ".debug_pubnames", // not used by gdb as of 6.7.1
".debug_ranges",
".debug_str",
};
static const char* lines_only_debug_sections[] =
{ ".debug_abbrev",
// ".debug_aranges", // not used by gdb as of 6.7.1
// ".debug_frame",
".debug_info",
".debug_line",
// ".debug_loc",
// ".debug_macinfo",
// ".debug_pubnames", // not used by gdb as of 6.7.1
// ".debug_ranges",
".debug_str",
};
static inline bool
is_gdb_debug_section(const char* str)
{
// We can do this faster: binary search or a hashtable. But why bother?
for (size_t i = 0; i < sizeof(gdb_sections)/sizeof(*gdb_sections); ++i)
if (strcmp(str, gdb_sections[i]) == 0)
return true;
return false;
}
static inline bool
is_lines_only_debug_section(const char* str)
{
// We can do this faster: binary search or a hashtable. But why bother?
for (size_t i = 0;
i < sizeof(lines_only_debug_sections)/sizeof(*lines_only_debug_sections);
++i)
if (strcmp(str, lines_only_debug_sections[i]) == 0)
return true;
return false;
}
// Whether to include this section in the link.
template<int size, bool big_endian>
bool
Layout::include_section(Sized_relobj<size, big_endian>*, const char* name,
const elfcpp::Shdr<size, big_endian>& shdr)
{
if (shdr.get_sh_flags() & elfcpp::SHF_EXCLUDE)
return false;
switch (shdr.get_sh_type())
{
case elfcpp::SHT_NULL:
case elfcpp::SHT_SYMTAB:
case elfcpp::SHT_DYNSYM:
case elfcpp::SHT_HASH:
case elfcpp::SHT_DYNAMIC:
case elfcpp::SHT_SYMTAB_SHNDX:
return false;
case elfcpp::SHT_STRTAB:
// Discard the sections which have special meanings in the ELF
// ABI. Keep others (e.g., .stabstr). We could also do this by
// checking the sh_link fields of the appropriate sections.
return (strcmp(name, ".dynstr") != 0
&& strcmp(name, ".strtab") != 0
&& strcmp(name, ".shstrtab") != 0);
case elfcpp::SHT_RELA:
case elfcpp::SHT_REL:
case elfcpp::SHT_GROUP:
// If we are emitting relocations these should be handled
// elsewhere.
gold_assert(!parameters->options().relocatable()
&& !parameters->options().emit_relocs());
return false;
case elfcpp::SHT_PROGBITS:
if (parameters->options().strip_debug()
&& (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
{
if (is_debug_info_section(name))
return false;
}
if (parameters->options().strip_debug_non_line()
&& (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
{
// Debugging sections can only be recognized by name.
if (is_prefix_of(".debug", name)
&& !is_lines_only_debug_section(name))
return false;
}
if (parameters->options().strip_debug_gdb()
&& (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
{
// Debugging sections can only be recognized by name.
if (is_prefix_of(".debug", name)
&& !is_gdb_debug_section(name))
return false;
}
if (parameters->options().strip_lto_sections()
&& !parameters->options().relocatable()
&& (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
{
// Ignore LTO sections containing intermediate code.
if (is_prefix_of(".gnu.lto_", name))
return false;
}
// The GNU linker strips .gnu_debuglink sections, so we do too.
// This is a feature used to keep debugging information in
// separate files.
if (strcmp(name, ".gnu_debuglink") == 0)
return false;
return true;
default:
return true;
}
}
// Return an output section named NAME, or NULL if there is none.
Output_section*
Layout::find_output_section(const char* name) const
{
for (Section_list::const_iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
if (strcmp((*p)->name(), name) == 0)
return *p;
return NULL;
}
// Return an output segment of type TYPE, with segment flags SET set
// and segment flags CLEAR clear. Return NULL if there is none.
Output_segment*
Layout::find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
elfcpp::Elf_Word clear) const
{
for (Segment_list::const_iterator p = this->segment_list_.begin();
p != this->segment_list_.end();
++p)
if (static_cast<elfcpp::PT>((*p)->type()) == type
&& ((*p)->flags() & set) == set
&& ((*p)->flags() & clear) == 0)
return *p;
return NULL;
}
// Return the output section to use for section NAME with type TYPE
// and section flags FLAGS. NAME must be canonicalized in the string
// pool, and NAME_KEY is the key. IS_INTERP is true if this is the
// .interp section. IS_DYNAMIC_LINKER_SECTION is true if this section
// is used by the dynamic linker.
Output_section*
Layout::get_output_section(const char* name, Stringpool::Key name_key,
elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
bool is_interp, bool is_dynamic_linker_section)
{
elfcpp::Elf_Xword lookup_flags = flags;
// Ignoring SHF_WRITE and SHF_EXECINSTR here means that we combine
// read-write with read-only sections. Some other ELF linkers do
// not do this. FIXME: Perhaps there should be an option
// controlling this.
lookup_flags &= ~(elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR);
const Key key(name_key, std::make_pair(type, lookup_flags));
const std::pair<Key, Output_section*> v(key, NULL);
std::pair<Section_name_map::iterator, bool> ins(
this->section_name_map_.insert(v));
if (!ins.second)
return ins.first->second;
else
{
// This is the first time we've seen this name/type/flags
// combination. For compatibility with the GNU linker, we
// combine sections with contents and zero flags with sections
// with non-zero flags. This is a workaround for cases where
// assembler code forgets to set section flags. FIXME: Perhaps
// there should be an option to control this.
Output_section* os = NULL;
if (type == elfcpp::SHT_PROGBITS)
{
if (flags == 0)
{
Output_section* same_name = this->find_output_section(name);
if (same_name != NULL
&& same_name->type() == elfcpp::SHT_PROGBITS
&& (same_name->flags() & elfcpp::SHF_TLS) == 0)
os = same_name;
}
else if ((flags & elfcpp::SHF_TLS) == 0)
{
elfcpp::Elf_Xword zero_flags = 0;
const Key zero_key(name_key, std::make_pair(type, zero_flags));
Section_name_map::iterator p =
this->section_name_map_.find(zero_key);
if (p != this->section_name_map_.end())
os = p->second;
}
}
if (os == NULL)
os = this->make_output_section(name, type, flags, is_interp,
is_dynamic_linker_section);
ins.first->second = os;
return os;
}
}
// Pick the output section to use for section NAME, in input file
// RELOBJ, with type TYPE and flags FLAGS. RELOBJ may be NULL for a
// linker created section. IS_INPUT_SECTION is true if we are
// choosing an output section for an input section found in a input
// file. IS_INTERP is true if this is the .interp section.
// IS_DYNAMIC_LINKER_SECTION is true if this section is used by the
// dynamic linker. This will return NULL if the input section should
// be discarded.
Output_section*
Layout::choose_output_section(const Relobj* relobj, const char* name,
elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
bool is_input_section, bool is_interp,
bool is_dynamic_linker_section)
{
// We should not see any input sections after we have attached
// sections to segments.
gold_assert(!is_input_section || !this->sections_are_attached_);
// Some flags in the input section should not be automatically
// copied to the output section.
flags &= ~ (elfcpp::SHF_INFO_LINK
| elfcpp::SHF_LINK_ORDER
| elfcpp::SHF_GROUP
| elfcpp::SHF_MERGE
| elfcpp::SHF_STRINGS);
if (this->script_options_->saw_sections_clause())
{
// We are using a SECTIONS clause, so the output section is
// chosen based only on the name.
Script_sections* ss = this->script_options_->script_sections();
const char* file_name = relobj == NULL ? NULL : relobj->name().c_str();
Output_section** output_section_slot;
name = ss->output_section_name(file_name, name, &output_section_slot);
if (name == NULL)
{
// The SECTIONS clause says to discard this input section.
return NULL;
}
// If this is an orphan section--one not mentioned in the linker
// script--then OUTPUT_SECTION_SLOT will be NULL, and we do the
// default processing below.
if (output_section_slot != NULL)
{
if (*output_section_slot != NULL)
{
(*output_section_slot)->update_flags_for_input_section(flags);
return *output_section_slot;
}
// We don't put sections found in the linker script into
// SECTION_NAME_MAP_. That keeps us from getting confused
// if an orphan section is mapped to a section with the same
// name as one in the linker script.
name = this->namepool_.add(name, false, NULL);
Output_section* os =
this->make_output_section(name, type, flags, is_interp,
is_dynamic_linker_section);
os->set_found_in_sections_clause();
*output_section_slot = os;
return os;
}
}
// FIXME: Handle SHF_OS_NONCONFORMING somewhere.
// Turn NAME from the name of the input section into the name of the
// output section.
size_t len = strlen(name);
if (is_input_section
&& !this->script_options_->saw_sections_clause()
&& !parameters->options().relocatable())
name = Layout::output_section_name(name, &len);
Stringpool::Key name_key;
name = this->namepool_.add_with_length(name, len, true, &name_key);
// Find or make the output section. The output section is selected
// based on the section name, type, and flags.
return this->get_output_section(name, name_key, type, flags, is_interp,
is_dynamic_linker_section);
}
// Return the output section to use for input section SHNDX, with name
// NAME, with header HEADER, from object OBJECT. RELOC_SHNDX is the
// index of a relocation section which applies to this section, or 0
// if none, or -1U if more than one. RELOC_TYPE is the type of the
// relocation section if there is one. Set *OFF to the offset of this
// input section without the output section. Return NULL if the
// section should be discarded. Set *OFF to -1 if the section
// contents should not be written directly to the output file, but
// will instead receive special handling.
template<int size, bool big_endian>
Output_section*
Layout::layout(Sized_relobj<size, big_endian>* object, unsigned int shndx,
const char* name, const elfcpp::Shdr<size, big_endian>& shdr,
unsigned int reloc_shndx, unsigned int, off_t* off)
{
*off = 0;
if (!this->include_section(object, name, shdr))
return NULL;
Output_section* os;
// In a relocatable link a grouped section must not be combined with
// any other sections.
if (parameters->options().relocatable()
&& (shdr.get_sh_flags() & elfcpp::SHF_GROUP) != 0)
{
name = this->namepool_.add(name, true, NULL);
os = this->make_output_section(name, shdr.get_sh_type(),
shdr.get_sh_flags(), false, false);
}
else
{
os = this->choose_output_section(object, name, shdr.get_sh_type(),
shdr.get_sh_flags(), true, false,
false);
if (os == NULL)
return NULL;
}
// By default the GNU linker sorts input sections whose names match
// .ctor.*, .dtor.*, .init_array.*, or .fini_array.*. The sections
// are sorted by name. This is used to implement constructor
// priority ordering. We are compatible.
if (!this->script_options_->saw_sections_clause()
&& (is_prefix_of(".ctors.", name)
|| is_prefix_of(".dtors.", name)
|| is_prefix_of(".init_array.", name)
|| is_prefix_of(".fini_array.", name)))
os->set_must_sort_attached_input_sections();
// FIXME: Handle SHF_LINK_ORDER somewhere.
*off = os->add_input_section(object, shndx, name, shdr, reloc_shndx,
this->script_options_->saw_sections_clause());
return os;
}
// Handle a relocation section when doing a relocatable link.
template<int size, bool big_endian>
Output_section*
Layout::layout_reloc(Sized_relobj<size, big_endian>* object,
unsigned int,
const elfcpp::Shdr<size, big_endian>& shdr,
Output_section* data_section,
Relocatable_relocs* rr)
{
gold_assert(parameters->options().relocatable()
|| parameters->options().emit_relocs());
int sh_type = shdr.get_sh_type();
std::string name;
if (sh_type == elfcpp::SHT_REL)
name = ".rel";
else if (sh_type == elfcpp::SHT_RELA)
name = ".rela";
else
gold_unreachable();
name += data_section->name();
Output_section* os = this->choose_output_section(object, name.c_str(),
sh_type,
shdr.get_sh_flags(),
false, false, false);
os->set_should_link_to_symtab();
os->set_info_section(data_section);
Output_section_data* posd;
if (sh_type == elfcpp::SHT_REL)
{
os->set_entsize(elfcpp::Elf_sizes<size>::rel_size);
posd = new Output_relocatable_relocs<elfcpp::SHT_REL,
size,
big_endian>(rr);
}
else if (sh_type == elfcpp::SHT_RELA)
{
os->set_entsize(elfcpp::Elf_sizes<size>::rela_size);
posd = new Output_relocatable_relocs<elfcpp::SHT_RELA,
size,
big_endian>(rr);
}
else
gold_unreachable();
os->add_output_section_data(posd);
rr->set_output_data(posd);
return os;
}
// Handle a group section when doing a relocatable link.
template<int size, bool big_endian>
void
Layout::layout_group(Symbol_table* symtab,
Sized_relobj<size, big_endian>* object,
unsigned int,
const char* group_section_name,
const char* signature,
const elfcpp::Shdr<size, big_endian>& shdr,
elfcpp::Elf_Word flags,
std::vector<unsigned int>* shndxes)
{
gold_assert(parameters->options().relocatable());
gold_assert(shdr.get_sh_type() == elfcpp::SHT_GROUP);
group_section_name = this->namepool_.add(group_section_name, true, NULL);
Output_section* os = this->make_output_section(group_section_name,
elfcpp::SHT_GROUP,
shdr.get_sh_flags(),
false, false);
// We need to find a symbol with the signature in the symbol table.
// If we don't find one now, we need to look again later.
Symbol* sym = symtab->lookup(signature, NULL);
if (sym != NULL)
os->set_info_symndx(sym);
else
{
// Reserve some space to minimize reallocations.
if (this->group_signatures_.empty())
this->group_signatures_.reserve(this->number_of_input_files_ * 16);
// We will wind up using a symbol whose name is the signature.
// So just put the signature in the symbol name pool to save it.
signature = symtab->canonicalize_name(signature);
this->group_signatures_.push_back(Group_signature(os, signature));
}
os->set_should_link_to_symtab();
os->set_entsize(4);
section_size_type entry_count =
convert_to_section_size_type(shdr.get_sh_size() / 4);
Output_section_data* posd =
new Output_data_group<size, big_endian>(object, entry_count, flags,
shndxes);
os->add_output_section_data(posd);
}
// Special GNU handling of sections name .eh_frame. They will
// normally hold exception frame data as defined by the C++ ABI
// (http://codesourcery.com/cxx-abi/).
template<int size, bool big_endian>
Output_section*
Layout::layout_eh_frame(Sized_relobj<size, big_endian>* object,
const unsigned char* symbols,
off_t symbols_size,
const unsigned char* symbol_names,
off_t symbol_names_size,
unsigned int shndx,
const elfcpp::Shdr<size, big_endian>& shdr,
unsigned int reloc_shndx, unsigned int reloc_type,
off_t* off)
{
gold_assert(shdr.get_sh_type() == elfcpp::SHT_PROGBITS);
gold_assert((shdr.get_sh_flags() & elfcpp::SHF_ALLOC) != 0);
const char* const name = ".eh_frame";
Output_section* os = this->choose_output_section(object,
name,
elfcpp::SHT_PROGBITS,
elfcpp::SHF_ALLOC,
false, false, false);
if (os == NULL)
return NULL;
if (this->eh_frame_section_ == NULL)
{
this->eh_frame_section_ = os;
this->eh_frame_data_ = new Eh_frame();
if (parameters->options().eh_frame_hdr())
{
Output_section* hdr_os =
this->choose_output_section(NULL,
".eh_frame_hdr",
elfcpp::SHT_PROGBITS,
elfcpp::SHF_ALLOC,
false, false, false);
if (hdr_os != NULL)
{
Eh_frame_hdr* hdr_posd = new Eh_frame_hdr(os,
this->eh_frame_data_);
hdr_os->add_output_section_data(hdr_posd);
hdr_os->set_after_input_sections();
if (!this->script_options_->saw_phdrs_clause())
{
Output_segment* hdr_oseg;
hdr_oseg = this->make_output_segment(elfcpp::PT_GNU_EH_FRAME,
elfcpp::PF_R);
hdr_oseg->add_output_section(hdr_os, elfcpp::PF_R, false);
}
this->eh_frame_data_->set_eh_frame_hdr(hdr_posd);
}
}
}
gold_assert(this->eh_frame_section_ == os);
if (this->eh_frame_data_->add_ehframe_input_section(object,
symbols,
symbols_size,
symbol_names,
symbol_names_size,
shndx,
reloc_shndx,
reloc_type))
{
os->update_flags_for_input_section(shdr.get_sh_flags());
// We found a .eh_frame section we are going to optimize, so now
// we can add the set of optimized sections to the output
// section. We need to postpone adding this until we've found a
// section we can optimize so that the .eh_frame section in
// crtbegin.o winds up at the start of the output section.
if (!this->added_eh_frame_data_)
{
os->add_output_section_data(this->eh_frame_data_);
this->added_eh_frame_data_ = true;
}
*off = -1;
}
else
{
// We couldn't handle this .eh_frame section for some reason.
// Add it as a normal section.
bool saw_sections_clause = this->script_options_->saw_sections_clause();
*off = os->add_input_section(object, shndx, name, shdr, reloc_shndx,
saw_sections_clause);
}
return os;
}
// Add POSD to an output section using NAME, TYPE, and FLAGS. Return
// the output section.
Output_section*
Layout::add_output_section_data(const char* name, elfcpp::Elf_Word type,
elfcpp::Elf_Xword flags,
Output_section_data* posd,
bool is_dynamic_linker_section)
{
Output_section* os = this->choose_output_section(NULL, name, type, flags,
false, false,
is_dynamic_linker_section);
if (os != NULL)
os->add_output_section_data(posd);
return os;
}
// Map section flags to segment flags.
elfcpp::Elf_Word
Layout::section_flags_to_segment(elfcpp::Elf_Xword flags)
{
elfcpp::Elf_Word ret = elfcpp::PF_R;
if ((flags & elfcpp::SHF_WRITE) != 0)
ret |= elfcpp::PF_W;
if ((flags & elfcpp::SHF_EXECINSTR) != 0)
ret |= elfcpp::PF_X;
return ret;
}
// Sometimes we compress sections. This is typically done for
// sections that are not part of normal program execution (such as
// .debug_* sections), and where the readers of these sections know
// how to deal with compressed sections. This routine doesn't say for
// certain whether we'll compress -- it depends on commandline options
// as well -- just whether this section is a candidate for compression.
// (The Output_compressed_section class decides whether to compress
// a given section, and picks the name of the compressed section.)
static bool
is_compressible_debug_section(const char* secname)
{
return (strncmp(secname, ".debug", sizeof(".debug") - 1) == 0);
}
// Make a new Output_section, and attach it to segments as
// appropriate. IS_INTERP is true if this is the .interp section.
// IS_DYNAMIC_LINKER_SECTION is true if this section is used by the
// dynamic linker.
Output_section*
Layout::make_output_section(const char* name, elfcpp::Elf_Word type,
elfcpp::Elf_Xword flags, bool is_interp,
bool is_dynamic_linker_section)
{
Output_section* os;
if ((flags & elfcpp::SHF_ALLOC) == 0
&& strcmp(parameters->options().compress_debug_sections(), "none") != 0
&& is_compressible_debug_section(name))
os = new Output_compressed_section(&parameters->options(), name, type,
flags);
else if ((flags & elfcpp::SHF_ALLOC) == 0
&& parameters->options().strip_debug_non_line()
&& strcmp(".debug_abbrev", name) == 0)
{
os = this->debug_abbrev_ = new Output_reduced_debug_abbrev_section(
name, type, flags);
if (this->debug_info_)
this->debug_info_->set_abbreviations(this->debug_abbrev_);
}
else if ((flags & elfcpp::SHF_ALLOC) == 0
&& parameters->options().strip_debug_non_line()
&& strcmp(".debug_info", name) == 0)
{
os = this->debug_info_ = new Output_reduced_debug_info_section(
name, type, flags);
if (this->debug_abbrev_)
this->debug_info_->set_abbreviations(this->debug_abbrev_);
}
else
{
// FIXME: const_cast is ugly.
Target* target = const_cast<Target*>(&parameters->target());
os = target->make_output_section(name, type, flags);
}
if (is_interp)
os->set_is_interp();
if (is_dynamic_linker_section)
os->set_is_dynamic_linker_section();
parameters->target().new_output_section(os);
this->section_list_.push_back(os);
// The GNU linker by default sorts some sections by priority, so we
// do the same. We need to know that this might happen before we
// attach any input sections.
if (!this->script_options_->saw_sections_clause()
&& (strcmp(name, ".ctors") == 0
|| strcmp(name, ".dtors") == 0
|| strcmp(name, ".init_array") == 0
|| strcmp(name, ".fini_array") == 0))
os->set_may_sort_attached_input_sections();
// With -z relro, we have to recognize the special sections by name.
// There is no other way.
if (!this->script_options_->saw_sections_clause()
&& parameters->options().relro()
&& type == elfcpp::SHT_PROGBITS
&& (flags & elfcpp::SHF_ALLOC) != 0
&& (flags & elfcpp::SHF_WRITE) != 0)
{
if (strcmp(name, ".data.rel.ro") == 0)
os->set_is_relro();
else if (strcmp(name, ".data.rel.ro.local") == 0)
{
os->set_is_relro();
os->set_is_relro_local();
}
}
// Check for .stab*str sections, as .stab* sections need to link to
// them.
if (type == elfcpp::SHT_STRTAB
&& !this->have_stabstr_section_
&& strncmp(name, ".stab", 5) == 0
&& strcmp(name + strlen(name) - 3, "str") == 0)
this->have_stabstr_section_ = true;
// If we have already attached the sections to segments, then we
// need to attach this one now. This happens for sections created
// directly by the linker.
if (this->sections_are_attached_)
this->attach_section_to_segment(os);
return os;
}
// Attach output sections to segments. This is called after we have
// seen all the input sections.
void
Layout::attach_sections_to_segments()
{
for (Section_list::iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
this->attach_section_to_segment(*p);
this->sections_are_attached_ = true;
}
// Attach an output section to a segment.
void
Layout::attach_section_to_segment(Output_section* os)
{
if ((os->flags() & elfcpp::SHF_ALLOC) == 0)
this->unattached_section_list_.push_back(os);
else
this->attach_allocated_section_to_segment(os);
}
// Attach an allocated output section to a segment.
void
Layout::attach_allocated_section_to_segment(Output_section* os)
{
elfcpp::Elf_Xword flags = os->flags();
gold_assert((flags & elfcpp::SHF_ALLOC) != 0);
if (parameters->options().relocatable())
return;
// If we have a SECTIONS clause, we can't handle the attachment to
// segments until after we've seen all the sections.
if (this->script_options_->saw_sections_clause())
return;
gold_assert(!this->script_options_->saw_phdrs_clause());
// This output section goes into a PT_LOAD segment.
elfcpp::Elf_Word seg_flags = Layout::section_flags_to_segment(flags);
bool sort_sections = !this->script_options_->saw_sections_clause();
// In general the only thing we really care about for PT_LOAD
// segments is whether or not they are writable, so that is how we
// search for them. Large data sections also go into their own
// PT_LOAD segment. People who need segments sorted on some other
// basis will have to use a linker script.
Segment_list::const_iterator p;
for (p = this->segment_list_.begin();
p != this->segment_list_.end();
++p)
{
if ((*p)->type() != elfcpp::PT_LOAD)
continue;
if (!parameters->options().omagic()
&& ((*p)->flags() & elfcpp::PF_W) != (seg_flags & elfcpp::PF_W))
continue;
// If -Tbss was specified, we need to separate the data and BSS
// segments.
if (parameters->options().user_set_Tbss())
{
if ((os->type() == elfcpp::SHT_NOBITS)
== (*p)->has_any_data_sections())
continue;
}
if (os->is_large_data_section() && !(*p)->is_large_data_segment())
continue;
(*p)->add_output_section(os, seg_flags, sort_sections);
break;
}
if (p == this->segment_list_.end())
{
Output_segment* oseg = this->make_output_segment(elfcpp::PT_LOAD,
seg_flags);
if (os->is_large_data_section())
oseg->set_is_large_data_segment();
oseg->add_output_section(os, seg_flags, sort_sections);
}
// If we see a loadable SHT_NOTE section, we create a PT_NOTE
// segment.
if (os->type() == elfcpp::SHT_NOTE)
{
// See if we already have an equivalent PT_NOTE segment.
for (p = this->segment_list_.begin();
p != segment_list_.end();
++p)
{
if ((*p)->type() == elfcpp::PT_NOTE
&& (((*p)->flags() & elfcpp::PF_W)
== (seg_flags & elfcpp::PF_W)))
{
(*p)->add_output_section(os, seg_flags, false);
break;
}
}
if (p == this->segment_list_.end())
{
Output_segment* oseg = this->make_output_segment(elfcpp::PT_NOTE,
seg_flags);
oseg->add_output_section(os, seg_flags, false);
}
}
// If we see a loadable SHF_TLS section, we create a PT_TLS
// segment. There can only be one such segment.
if ((flags & elfcpp::SHF_TLS) != 0)
{
if (this->tls_segment_ == NULL)
this->make_output_segment(elfcpp::PT_TLS, seg_flags);
this->tls_segment_->add_output_section(os, seg_flags, false);
}
// If -z relro is in effect, and we see a relro section, we create a
// PT_GNU_RELRO segment. There can only be one such segment.
if (os->is_relro() && parameters->options().relro())
{
gold_assert(seg_flags == (elfcpp::PF_R | elfcpp::PF_W));
if (this->relro_segment_ == NULL)
this->make_output_segment(elfcpp::PT_GNU_RELRO, seg_flags);
this->relro_segment_->add_output_section(os, seg_flags, false);
}
}
// Make an output section for a script.
Output_section*
Layout::make_output_section_for_script(const char* name)
{
name = this->namepool_.add(name, false, NULL);
Output_section* os = this->make_output_section(name, elfcpp::SHT_PROGBITS,
elfcpp::SHF_ALLOC, false,
false);
os->set_found_in_sections_clause();
return os;
}
// Return the number of segments we expect to see.
size_t
Layout::expected_segment_count() const
{
size_t ret = this->segment_list_.size();
// If we didn't see a SECTIONS clause in a linker script, we should
// already have the complete list of segments. Otherwise we ask the
// SECTIONS clause how many segments it expects, and add in the ones
// we already have (PT_GNU_STACK, PT_GNU_EH_FRAME, etc.)
if (!this->script_options_->saw_sections_clause())
return ret;
else
{
const Script_sections* ss = this->script_options_->script_sections();
return ret + ss->expected_segment_count(this);
}
}
// Handle the .note.GNU-stack section at layout time. SEEN_GNU_STACK
// is whether we saw a .note.GNU-stack section in the object file.
// GNU_STACK_FLAGS is the section flags. The flags give the
// protection required for stack memory. We record this in an
// executable as a PT_GNU_STACK segment. If an object file does not
// have a .note.GNU-stack segment, we must assume that it is an old
// object. On some targets that will force an executable stack.
void
Layout::layout_gnu_stack(bool seen_gnu_stack, uint64_t gnu_stack_flags)
{
if (!seen_gnu_stack)
this->input_without_gnu_stack_note_ = true;
else
{
this->input_with_gnu_stack_note_ = true;
if ((gnu_stack_flags & elfcpp::SHF_EXECINSTR) != 0)
this->input_requires_executable_stack_ = true;
}
}
// Create automatic note sections.
void
Layout::create_notes()
{
this->create_gold_note();
this->create_executable_stack_info();
this->create_build_id();
}
// Create the dynamic sections which are needed before we read the
// relocs.
void
Layout::create_initial_dynamic_sections(Symbol_table* symtab)
{
if (parameters->doing_static_link())
return;
this->dynamic_section_ = this->choose_output_section(NULL, ".dynamic",
elfcpp::SHT_DYNAMIC,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_WRITE),
false, false, true);
this->dynamic_section_->set_is_relro();
symtab->define_in_output_data("_DYNAMIC", NULL, this->dynamic_section_, 0, 0,
elfcpp::STT_OBJECT, elfcpp::STB_LOCAL,
elfcpp::STV_HIDDEN, 0, false, false);
this->dynamic_data_ = new Output_data_dynamic(&this->dynpool_);
this->dynamic_section_->add_output_section_data(this->dynamic_data_);
}
// For each output section whose name can be represented as C symbol,
// define __start and __stop symbols for the section. This is a GNU
// extension.
void
Layout::define_section_symbols(Symbol_table* symtab)
{
for (Section_list::const_iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
{
const char* const name = (*p)->name();
if (name[strspn(name,
("0123456789"
"ABCDEFGHIJKLMNOPWRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"_"))]
== '\0')
{
const std::string name_string(name);
const std::string start_name("__start_" + name_string);
const std::string stop_name("__stop_" + name_string);
symtab->define_in_output_data(start_name.c_str(),
NULL, // version
*p,
0, // value
0, // symsize
elfcpp::STT_NOTYPE,
elfcpp::STB_GLOBAL,
elfcpp::STV_DEFAULT,
0, // nonvis
false, // offset_is_from_end
true); // only_if_ref
symtab->define_in_output_data(stop_name.c_str(),
NULL, // version
*p,
0, // value
0, // symsize
elfcpp::STT_NOTYPE,
elfcpp::STB_GLOBAL,
elfcpp::STV_DEFAULT,
0, // nonvis
true, // offset_is_from_end
true); // only_if_ref
}
}
}
// Define symbols for group signatures.
void
Layout::define_group_signatures(Symbol_table* symtab)
{
for (Group_signatures::iterator p = this->group_signatures_.begin();
p != this->group_signatures_.end();
++p)
{
Symbol* sym = symtab->lookup(p->signature, NULL);
if (sym != NULL)
p->section->set_info_symndx(sym);
else
{
// Force the name of the group section to the group
// signature, and use the group's section symbol as the
// signature symbol.
if (strcmp(p->section->name(), p->signature) != 0)
{
const char* name = this->namepool_.add(p->signature,
true, NULL);
p->section->set_name(name);
}
p->section->set_needs_symtab_index();
p->section->set_info_section_symndx(p->section);
}
}
this->group_signatures_.clear();
}
// Find the first read-only PT_LOAD segment, creating one if
// necessary.
Output_segment*
Layout::find_first_load_seg()
{
for (Segment_list::const_iterator p = this->segment_list_.begin();
p != this->segment_list_.end();
++p)
{
if ((*p)->type() == elfcpp::PT_LOAD
&& ((*p)->flags() & elfcpp::PF_R) != 0
&& (parameters->options().omagic()
|| ((*p)->flags() & elfcpp::PF_W) == 0))
return *p;
}
gold_assert(!this->script_options_->saw_phdrs_clause());
Output_segment* load_seg = this->make_output_segment(elfcpp::PT_LOAD,
elfcpp::PF_R);
return load_seg;
}
// Save states of all current output segments. Store saved states
// in SEGMENT_STATES.
void
Layout::save_segments(Segment_states* segment_states)
{
for (Segment_list::const_iterator p = this->segment_list_.begin();
p != this->segment_list_.end();
++p)
{
Output_segment* segment = *p;
// Shallow copy.
Output_segment* copy = new Output_segment(*segment);
(*segment_states)[segment] = copy;
}
}
// Restore states of output segments and delete any segment not found in
// SEGMENT_STATES.
void
Layout::restore_segments(const Segment_states* segment_states)
{
// Go through the segment list and remove any segment added in the
// relaxation loop.
this->tls_segment_ = NULL;
this->relro_segment_ = NULL;
Segment_list::iterator list_iter = this->segment_list_.begin();
while (list_iter != this->segment_list_.end())
{
Output_segment* segment = *list_iter;
Segment_states::const_iterator states_iter =
segment_states->find(segment);
if (states_iter != segment_states->end())
{
const Output_segment* copy = states_iter->second;
// Shallow copy to restore states.
*segment = *copy;
// Also fix up TLS and RELRO segment pointers as appropriate.
if (segment->type() == elfcpp::PT_TLS)
this->tls_segment_ = segment;
else if (segment->type() == elfcpp::PT_GNU_RELRO)
this->relro_segment_ = segment;
++list_iter;
}
else
{
list_iter = this->segment_list_.erase(list_iter);
// This is a segment created during section layout. It should be
// safe to remove it since we should have removed all pointers to it.
delete segment;
}
}
}
// Clean up after relaxation so that sections can be laid out again.
void
Layout::clean_up_after_relaxation()
{
// Restore the segments to point state just prior to the relaxation loop.
Script_sections* script_section = this->script_options_->script_sections();
script_section->release_segments();
this->restore_segments(this->segment_states_);
// Reset section addresses and file offsets
for (Section_list::iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
{
(*p)->reset_address_and_file_offset();
(*p)->restore_states();
}
// Reset special output object address and file offsets.
for (Data_list::iterator p = this->special_output_list_.begin();
p != this->special_output_list_.end();
++p)
(*p)->reset_address_and_file_offset();
// A linker script may have created some output section data objects.
// They are useless now.
for (Output_section_data_list::const_iterator p =
this->script_output_section_data_list_.begin();
p != this->script_output_section_data_list_.end();
++p)
delete *p;
this->script_output_section_data_list_.clear();
}
// Prepare for relaxation.
void
Layout::prepare_for_relaxation()
{
// Create an relaxation debug check if in debugging mode.
if (is_debugging_enabled(DEBUG_RELAXATION))
this->relaxation_debug_check_ = new Relaxation_debug_check();
// Save segment states.
this->segment_states_ = new Segment_states();
this->save_segments(this->segment_states_);
for(Section_list::const_iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
(*p)->save_states();
if (is_debugging_enabled(DEBUG_RELAXATION))
this->relaxation_debug_check_->check_output_data_for_reset_values(
this->section_list_, this->special_output_list_);
// Also enable recording of output section data from scripts.
this->record_output_section_data_from_script_ = true;
}
// Relaxation loop body: If target has no relaxation, this runs only once
// Otherwise, the target relaxation hook is called at the end of
// each iteration. If the hook returns true, it means re-layout of
// section is required.
//
// The number of segments created by a linking script without a PHDRS
// clause may be affected by section sizes and alignments. There is
// a remote chance that relaxation causes different number of PT_LOAD
// segments are created and sections are attached to different segments.
// Therefore, we always throw away all segments created during section
// layout. In order to be able to restart the section layout, we keep
// a copy of the segment list right before the relaxation loop and use
// that to restore the segments.
//
// PASS is the current relaxation pass number.
// SYMTAB is a symbol table.
// PLOAD_SEG is the address of a pointer for the load segment.
// PHDR_SEG is a pointer to the PHDR segment.
// SEGMENT_HEADERS points to the output segment header.
// FILE_HEADER points to the output file header.
// PSHNDX is the address to store the output section index.
off_t inline
Layout::relaxation_loop_body(
int pass,
Target* target,
Symbol_table* symtab,
Output_segment** pload_seg,
Output_segment* phdr_seg,
Output_segment_headers* segment_headers,
Output_file_header* file_header,
unsigned int* pshndx)
{
// If this is not the first iteration, we need to clean up after
// relaxation so that we can lay out the sections again.
if (pass != 0)
this->clean_up_after_relaxation();
// If there is a SECTIONS clause, put all the input sections into
// the required order.
Output_segment* load_seg;
if (this->script_options_->saw_sections_clause())
load_seg = this->set_section_addresses_from_script(symtab);
else if (parameters->options().relocatable())
load_seg = NULL;
else
load_seg = this->find_first_load_seg();
if (parameters->options().oformat_enum()
!= General_options::OBJECT_FORMAT_ELF)
load_seg = NULL;
gold_assert(phdr_seg == NULL
|| load_seg != NULL
|| this->script_options_->saw_sections_clause());
// Lay out the segment headers.
if (!parameters->options().relocatable())
{
gold_assert(segment_headers != NULL);
if (load_seg != NULL)
load_seg->add_initial_output_data(segment_headers);
if (phdr_seg != NULL)
phdr_seg->add_initial_output_data(segment_headers);
}
// Lay out the file header.
if (load_seg != NULL)
load_seg->add_initial_output_data(file_header);
if (this->script_options_->saw_phdrs_clause()
&& !parameters->options().relocatable())
{
// Support use of FILEHDRS and PHDRS attachments in a PHDRS
// clause in a linker script.
Script_sections* ss = this->script_options_->script_sections();
ss->put_headers_in_phdrs(file_header, segment_headers);
}
// We set the output section indexes in set_segment_offsets and
// set_section_indexes.
*pshndx = 1;
// Set the file offsets of all the segments, and all the sections
// they contain.
off_t off;
if (!parameters->options().relocatable())
off = this->set_segment_offsets(target, load_seg, pshndx);
else
off = this->set_relocatable_section_offsets(file_header, pshndx);
// Verify that the dummy relaxation does not change anything.
if (is_debugging_enabled(DEBUG_RELAXATION))
{
if (pass == 0)
this->relaxation_debug_check_->read_sections(this->section_list_);
else
this->relaxation_debug_check_->verify_sections(this->section_list_);
}
*pload_seg = load_seg;
return off;
}
// Finalize the layout. When this is called, we have created all the
// output sections and all the output segments which are based on
// input sections. We have several things to do, and we have to do
// them in the right order, so that we get the right results correctly
// and efficiently.
// 1) Finalize the list of output segments and create the segment
// table header.
// 2) Finalize the dynamic symbol table and associated sections.
// 3) Determine the final file offset of all the output segments.
// 4) Determine the final file offset of all the SHF_ALLOC output
// sections.
// 5) Create the symbol table sections and the section name table
// section.
// 6) Finalize the symbol table: set symbol values to their final
// value and make a final determination of which symbols are going
// into the output symbol table.
// 7) Create the section table header.
// 8) Determine the final file offset of all the output sections which
// are not SHF_ALLOC, including the section table header.
// 9) Finalize the ELF file header.
// This function returns the size of the output file.
off_t
Layout::finalize(const Input_objects* input_objects, Symbol_table* symtab,
Target* target, const Task* task)
{
target->finalize_sections(this);
this->count_local_symbols(task, input_objects);
this->link_stabs_sections();
Output_segment* phdr_seg = NULL;
if (!parameters->options().relocatable() && !parameters->doing_static_link())
{
// There was a dynamic object in the link. We need to create
// some information for the dynamic linker.
// Create the PT_PHDR segment which will hold the program
// headers.
if (!this->script_options_->saw_phdrs_clause())
phdr_seg = this->make_output_segment(elfcpp::PT_PHDR, elfcpp::PF_R);
// Create the dynamic symbol table, including the hash table.
Output_section* dynstr;
std::vector<Symbol*> dynamic_symbols;
unsigned int local_dynamic_count;
Versions versions(*this->script_options()->version_script_info(),
&this->dynpool_);
this->create_dynamic_symtab(input_objects, symtab, &dynstr,
&local_dynamic_count, &dynamic_symbols,
&versions);
// Create the .interp section to hold the name of the
// interpreter, and put it in a PT_INTERP segment.
if (!parameters->options().shared())
this->create_interp(target);
// Finish the .dynamic section to hold the dynamic data, and put
// it in a PT_DYNAMIC segment.
this->finish_dynamic_section(input_objects, symtab);
// We should have added everything we need to the dynamic string
// table.
this->dynpool_.set_string_offsets();
// Create the version sections. We can't do this until the
// dynamic string table is complete.
this->create_version_sections(&versions, symtab, local_dynamic_count,
dynamic_symbols, dynstr);
}
if (this->incremental_inputs_)
{
this->incremental_inputs_->finalize();
this->create_incremental_info_sections();
}
// Create segment headers.
Output_segment_headers* segment_headers =
(parameters->options().relocatable()
? NULL
: new Output_segment_headers(this->segment_list_));
// Lay out the file header.
Output_file_header* file_header
= new Output_file_header(target, symtab, segment_headers,
parameters->options().entry());
this->special_output_list_.push_back(file_header);
if (segment_headers != NULL)
this->special_output_list_.push_back(segment_headers);
// Find approriate places for orphan output sections if we are using
// a linker script.
if (this->script_options_->saw_sections_clause())
this->place_orphan_sections_in_script();
Output_segment* load_seg;
off_t off;
unsigned int shndx;
int pass = 0;
// Take a snapshot of the section layout as needed.
if (target->may_relax())
this->prepare_for_relaxation();
// Run the relaxation loop to lay out sections.
do
{
off = this->relaxation_loop_body(pass, target, symtab, &load_seg,
phdr_seg, segment_headers, file_header,
&shndx);
pass++;
}
while (target->may_relax()
&& target->relax(pass, input_objects, symtab, this));
// Set the file offsets of all the non-data sections we've seen so
// far which don't have to wait for the input sections. We need
// this in order to finalize local symbols in non-allocated
// sections.
off = this->set_section_offsets(off, BEFORE_INPUT_SECTIONS_PASS);
// Set the section indexes of all unallocated sections seen so far,
// in case any of them are somehow referenced by a symbol.
shndx = this->set_section_indexes(shndx);
// Create the symbol table sections.
this->create_symtab_sections(input_objects, symtab, shndx, &off);
if (!parameters->doing_static_link())
this->assign_local_dynsym_offsets(input_objects);
// Process any symbol assignments from a linker script. This must
// be called after the symbol table has been finalized.
this->script_options_->finalize_symbols(symtab, this);
// Create the .shstrtab section.
Output_section* shstrtab_section = this->create_shstrtab();
// Set the file offsets of the rest of the non-data sections which
// don't have to wait for the input sections.
off = this->set_section_offsets(off, BEFORE_INPUT_SECTIONS_PASS);
// Now that all sections have been created, set the section indexes
// for any sections which haven't been done yet.
shndx = this->set_section_indexes(shndx);
// Create the section table header.
this->create_shdrs(shstrtab_section, &off);
// If there are no sections which require postprocessing, we can
// handle the section names now, and avoid a resize later.
if (!this->any_postprocessing_sections_)
off = this->set_section_offsets(off,
STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS);
file_header->set_section_info(this->section_headers_, shstrtab_section);
// Now we know exactly where everything goes in the output file
// (except for non-allocated sections which require postprocessing).
Output_data::layout_complete();
this->output_file_size_ = off;
return off;
}
// Create a note header following the format defined in the ELF ABI.
// NAME is the name, NOTE_TYPE is the type, SECTION_NAME is the name
// of the section to create, DESCSZ is the size of the descriptor.
// ALLOCATE is true if the section should be allocated in memory.
// This returns the new note section. It sets *TRAILING_PADDING to
// the number of trailing zero bytes required.
Output_section*
Layout::create_note(const char* name, int note_type,
const char* section_name, size_t descsz,
bool allocate, size_t* trailing_padding)
{
// Authorities all agree that the values in a .note field should
// be aligned on 4-byte boundaries for 32-bit binaries. However,
// they differ on what the alignment is for 64-bit binaries.
// The GABI says unambiguously they take 8-byte alignment:
// http://sco.com/developers/gabi/latest/ch5.pheader.html#note_section
// Other documentation says alignment should always be 4 bytes:
// http://www.netbsd.org/docs/kernel/elf-notes.html#note-format
// GNU ld and GNU readelf both support the latter (at least as of
// version 2.16.91), and glibc always generates the latter for
// .note.ABI-tag (as of version 1.6), so that's the one we go with
// here.
#ifdef GABI_FORMAT_FOR_DOTNOTE_SECTION // This is not defined by default.
const int size = parameters->target().get_size();
#else
const int size = 32;
#endif
// The contents of the .note section.
size_t namesz = strlen(name) + 1;
size_t aligned_namesz = align_address(namesz, size / 8);
size_t aligned_descsz = align_address(descsz, size / 8);
size_t notehdrsz = 3 * (size / 8) + aligned_namesz;
unsigned char* buffer = new unsigned char[notehdrsz];
memset(buffer, 0, notehdrsz);
bool is_big_endian = parameters->target().is_big_endian();
if (size == 32)
{
if (!is_big_endian)
{
elfcpp::Swap<32, false>::writeval(buffer, namesz);
elfcpp::Swap<32, false>::writeval(buffer + 4, descsz);
elfcpp::Swap<32, false>::writeval(buffer + 8, note_type);
}
else
{
elfcpp::Swap<32, true>::writeval(buffer, namesz);
elfcpp::Swap<32, true>::writeval(buffer + 4, descsz);
elfcpp::Swap<32, true>::writeval(buffer + 8, note_type);
}
}
else if (size == 64)
{
if (!is_big_endian)
{
elfcpp::Swap<64, false>::writeval(buffer, namesz);
elfcpp::Swap<64, false>::writeval(buffer + 8, descsz);
elfcpp::Swap<64, false>::writeval(buffer + 16, note_type);
}
else
{
elfcpp::Swap<64, true>::writeval(buffer, namesz);
elfcpp::Swap<64, true>::writeval(buffer + 8, descsz);
elfcpp::Swap<64, true>::writeval(buffer + 16, note_type);
}
}
else
gold_unreachable();
memcpy(buffer + 3 * (size / 8), name, namesz);
elfcpp::Elf_Xword flags = 0;
if (allocate)
flags = elfcpp::SHF_ALLOC;
Output_section* os = this->choose_output_section(NULL, section_name,
elfcpp::SHT_NOTE,
flags, false, false,
false);
if (os == NULL)
return NULL;
Output_section_data* posd = new Output_data_const_buffer(buffer, notehdrsz,
size / 8,
"** note header");
os->add_output_section_data(posd);
*trailing_padding = aligned_descsz - descsz;
return os;
}
// For an executable or shared library, create a note to record the
// version of gold used to create the binary.
void
Layout::create_gold_note()
{
if (parameters->options().relocatable())
return;
std::string desc = std::string("gold ") + gold::get_version_string();
size_t trailing_padding;
Output_section *os = this->create_note("GNU", elfcpp::NT_GNU_GOLD_VERSION,
".note.gnu.gold-version", desc.size(),
false, &trailing_padding);
if (os == NULL)
return;
Output_section_data* posd = new Output_data_const(desc, 4);
os->add_output_section_data(posd);
if (trailing_padding > 0)
{
posd = new Output_data_zero_fill(trailing_padding, 0);
os->add_output_section_data(posd);
}
}
// Record whether the stack should be executable. This can be set
// from the command line using the -z execstack or -z noexecstack
// options. Otherwise, if any input file has a .note.GNU-stack
// section with the SHF_EXECINSTR flag set, the stack should be
// executable. Otherwise, if at least one input file a
// .note.GNU-stack section, and some input file has no .note.GNU-stack
// section, we use the target default for whether the stack should be
// executable. Otherwise, we don't generate a stack note. When
// generating a object file, we create a .note.GNU-stack section with
// the appropriate marking. When generating an executable or shared
// library, we create a PT_GNU_STACK segment.
void
Layout::create_executable_stack_info()
{
bool is_stack_executable;
if (parameters->options().is_execstack_set())
is_stack_executable = parameters->options().is_stack_executable();
else if (!this->input_with_gnu_stack_note_)
return;
else
{
if (this->input_requires_executable_stack_)
is_stack_executable = true;
else if (this->input_without_gnu_stack_note_)
is_stack_executable =
parameters->target().is_default_stack_executable();
else
is_stack_executable = false;
}
if (parameters->options().relocatable())
{
const char* name = this->namepool_.add(".note.GNU-stack", false, NULL);
elfcpp::Elf_Xword flags = 0;
if (is_stack_executable)
flags |= elfcpp::SHF_EXECINSTR;
this->make_output_section(name, elfcpp::SHT_PROGBITS, flags, false,
false);
}
else
{
if (this->script_options_->saw_phdrs_clause())
return;
int flags = elfcpp::PF_R | elfcpp::PF_W;
if (is_stack_executable)
flags |= elfcpp::PF_X;
this->make_output_segment(elfcpp::PT_GNU_STACK, flags);
}
}
// If --build-id was used, set up the build ID note.
void
Layout::create_build_id()
{
if (!parameters->options().user_set_build_id())
return;
const char* style = parameters->options().build_id();
if (strcmp(style, "none") == 0)
return;
// Set DESCSZ to the size of the note descriptor. When possible,
// set DESC to the note descriptor contents.
size_t descsz;
std::string desc;
if (strcmp(style, "md5") == 0)
descsz = 128 / 8;
else if (strcmp(style, "sha1") == 0)
descsz = 160 / 8;
else if (strcmp(style, "uuid") == 0)
{
const size_t uuidsz = 128 / 8;
char buffer[uuidsz];
memset(buffer, 0, uuidsz);
int descriptor = open_descriptor(-1, "/dev/urandom", O_RDONLY);
if (descriptor < 0)
gold_error(_("--build-id=uuid failed: could not open /dev/urandom: %s"),
strerror(errno));
else
{
ssize_t got = ::read(descriptor, buffer, uuidsz);
release_descriptor(descriptor, true);
if (got < 0)
gold_error(_("/dev/urandom: read failed: %s"), strerror(errno));
else if (static_cast<size_t>(got) != uuidsz)
gold_error(_("/dev/urandom: expected %zu bytes, got %zd bytes"),
uuidsz, got);
}
desc.assign(buffer, uuidsz);
descsz = uuidsz;
}
else if (strncmp(style, "0x", 2) == 0)
{
hex_init();
const char* p = style + 2;
while (*p != '\0')
{
if (hex_p(p[0]) && hex_p(p[1]))
{
char c = (hex_value(p[0]) << 4) | hex_value(p[1]);
desc += c;
p += 2;
}
else if (*p == '-' || *p == ':')
++p;
else
gold_fatal(_("--build-id argument '%s' not a valid hex number"),
style);
}
descsz = desc.size();
}
else
gold_fatal(_("unrecognized --build-id argument '%s'"), style);
// Create the note.
size_t trailing_padding;
Output_section* os = this->create_note("GNU", elfcpp::NT_GNU_BUILD_ID,
".note.gnu.build-id", descsz, true,
&trailing_padding);
if (os == NULL)
return;
if (!desc.empty())
{
// We know the value already, so we fill it in now.
gold_assert(desc.size() == descsz);
Output_section_data* posd = new Output_data_const(desc, 4);
os->add_output_section_data(posd);
if (trailing_padding != 0)
{
posd = new Output_data_zero_fill(trailing_padding, 0);
os->add_output_section_data(posd);
}
}
else
{
// We need to compute a checksum after we have completed the
// link.
gold_assert(trailing_padding == 0);
this->build_id_note_ = new Output_data_zero_fill(descsz, 4);
os->add_output_section_data(this->build_id_note_);
}
}
// If we have both .stabXX and .stabXXstr sections, then the sh_link
// field of the former should point to the latter. I'm not sure who
// started this, but the GNU linker does it, and some tools depend
// upon it.
void
Layout::link_stabs_sections()
{
if (!this->have_stabstr_section_)
return;
for (Section_list::iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
{
if ((*p)->type() != elfcpp::SHT_STRTAB)
continue;
const char* name = (*p)->name();
if (strncmp(name, ".stab", 5) != 0)
continue;
size_t len = strlen(name);
if (strcmp(name + len - 3, "str") != 0)
continue;
std::string stab_name(name, len - 3);
Output_section* stab_sec;
stab_sec = this->find_output_section(stab_name.c_str());
if (stab_sec != NULL)
stab_sec->set_link_section(*p);
}
}
// Create .gnu_incremental_inputs and .gnu_incremental_strtab sections needed
// for the next run of incremental linking to check what has changed.
void
Layout::create_incremental_info_sections()
{
gold_assert(this->incremental_inputs_ != NULL);
// Add the .gnu_incremental_inputs section.
const char *incremental_inputs_name =
this->namepool_.add(".gnu_incremental_inputs", false, NULL);
Output_section* inputs_os =
this->make_output_section(incremental_inputs_name,
elfcpp::SHT_GNU_INCREMENTAL_INPUTS, 0,
false, false);
Output_section_data* posd =
this->incremental_inputs_->create_incremental_inputs_section_data();
inputs_os->add_output_section_data(posd);
// Add the .gnu_incremental_strtab section.
const char *incremental_strtab_name =
this->namepool_.add(".gnu_incremental_strtab", false, NULL);
Output_section* strtab_os = this->make_output_section(incremental_strtab_name,
elfcpp::SHT_STRTAB,
0, false, false);
Output_data_strtab* strtab_data =
new Output_data_strtab(this->incremental_inputs_->get_stringpool());
strtab_os->add_output_section_data(strtab_data);
inputs_os->set_link_section(strtab_data);
}
// Return whether SEG1 should be before SEG2 in the output file. This
// is based entirely on the segment type and flags. When this is
// called the segment addresses has normally not yet been set.
bool
Layout::segment_precedes(const Output_segment* seg1,
const Output_segment* seg2)
{
elfcpp::Elf_Word type1 = seg1->type();
elfcpp::Elf_Word type2 = seg2->type();
// The single PT_PHDR segment is required to precede any loadable
// segment. We simply make it always first.
if (type1 == elfcpp::PT_PHDR)
{
gold_assert(type2 != elfcpp::PT_PHDR);
return true;
}
if (type2 == elfcpp::PT_PHDR)
return false;
// The single PT_INTERP segment is required to precede any loadable
// segment. We simply make it always second.
if (type1 == elfcpp::PT_INTERP)
{
gold_assert(type2 != elfcpp::PT_INTERP);
return true;
}
if (type2 == elfcpp::PT_INTERP)
return false;
// We then put PT_LOAD segments before any other segments.
if (type1 == elfcpp::PT_LOAD && type2 != elfcpp::PT_LOAD)
return true;
if (type2 == elfcpp::PT_LOAD && type1 != elfcpp::PT_LOAD)
return false;
// We put the PT_TLS segment last except for the PT_GNU_RELRO
// segment, because that is where the dynamic linker expects to find
// it (this is just for efficiency; other positions would also work
// correctly).
if (type1 == elfcpp::PT_TLS
&& type2 != elfcpp::PT_TLS
&& type2 != elfcpp::PT_GNU_RELRO)
return false;
if (type2 == elfcpp::PT_TLS
&& type1 != elfcpp::PT_TLS
&& type1 != elfcpp::PT_GNU_RELRO)
return true;
// We put the PT_GNU_RELRO segment last, because that is where the
// dynamic linker expects to find it (as with PT_TLS, this is just
// for efficiency).
if (type1 == elfcpp::PT_GNU_RELRO && type2 != elfcpp::PT_GNU_RELRO)
return false;
if (type2 == elfcpp::PT_GNU_RELRO && type1 != elfcpp::PT_GNU_RELRO)
return true;
const elfcpp::Elf_Word flags1 = seg1->flags();
const elfcpp::Elf_Word flags2 = seg2->flags();
// The order of non-PT_LOAD segments is unimportant. We simply sort
// by the numeric segment type and flags values. There should not
// be more than one segment with the same type and flags.
if (type1 != elfcpp::PT_LOAD)
{
if (type1 != type2)
return type1 < type2;
gold_assert(flags1 != flags2);
return flags1 < flags2;
}
// If the addresses are set already, sort by load address.
if (seg1->are_addresses_set())
{
if (!seg2->are_addresses_set())
return true;
unsigned int section_count1 = seg1->output_section_count();
unsigned int section_count2 = seg2->output_section_count();
if (section_count1 == 0 && section_count2 > 0)
return true;
if (section_count1 > 0 && section_count2 == 0)
return false;
uint64_t paddr1 = seg1->first_section_load_address();
uint64_t paddr2 = seg2->first_section_load_address();
if (paddr1 != paddr2)
return paddr1 < paddr2;
}
else if (seg2->are_addresses_set())
return false;
// A segment which holds large data comes after a segment which does
// not hold large data.
if (seg1->is_large_data_segment())
{
if (!seg2->is_large_data_segment())
return false;
}
else if (seg2->is_large_data_segment())
return true;
// Otherwise, we sort PT_LOAD segments based on the flags. Readonly
// segments come before writable segments. Then writable segments
// with data come before writable segments without data. Then
// executable segments come before non-executable segments. Then
// the unlikely case of a non-readable segment comes before the
// normal case of a readable segment. If there are multiple
// segments with the same type and flags, we require that the
// address be set, and we sort by virtual address and then physical
// address.
if ((flags1 & elfcpp::PF_W) != (flags2 & elfcpp::PF_W))
return (flags1 & elfcpp::PF_W) == 0;
if ((flags1 & elfcpp::PF_W) != 0
&& seg1->has_any_data_sections() != seg2->has_any_data_sections())
return seg1->has_any_data_sections();
if ((flags1 & elfcpp::PF_X) != (flags2 & elfcpp::PF_X))
return (flags1 & elfcpp::PF_X) != 0;
if ((flags1 & elfcpp::PF_R) != (flags2 & elfcpp::PF_R))
return (flags1 & elfcpp::PF_R) == 0;
// We shouldn't get here--we shouldn't create segments which we
// can't distinguish.
gold_unreachable();
}
// Increase OFF so that it is congruent to ADDR modulo ABI_PAGESIZE.
static off_t
align_file_offset(off_t off, uint64_t addr, uint64_t abi_pagesize)
{
uint64_t unsigned_off = off;
uint64_t aligned_off = ((unsigned_off & ~(abi_pagesize - 1))
| (addr & (abi_pagesize - 1)));
if (aligned_off < unsigned_off)
aligned_off += abi_pagesize;
return aligned_off;
}
// Set the file offsets of all the segments, and all the sections they
// contain. They have all been created. LOAD_SEG must be be laid out
// first. Return the offset of the data to follow.
off_t
Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
unsigned int *pshndx)
{
// Sort them into the final order.
std::sort(this->segment_list_.begin(), this->segment_list_.end(),
Layout::Compare_segments());
// Find the PT_LOAD segments, and set their addresses and offsets
// and their section's addresses and offsets.
uint64_t addr;
if (parameters->options().user_set_Ttext())
addr = parameters->options().Ttext();
else if (parameters->options().output_is_position_independent())
addr = 0;
else
addr = target->default_text_segment_address();
off_t off = 0;
// If LOAD_SEG is NULL, then the file header and segment headers
// will not be loadable. But they still need to be at offset 0 in
// the file. Set their offsets now.
if (load_seg == NULL)
{
for (Data_list::iterator p = this->special_output_list_.begin();
p != this->special_output_list_.end();
++p)
{
off = align_address(off, (*p)->addralign());
(*p)->set_address_and_file_offset(0, off);
off += (*p)->data_size();
}
}
const bool check_sections = parameters->options().check_sections();
Output_segment* last_load_segment = NULL;
bool was_readonly = false;
for (Segment_list::iterator p = this->segment_list_.begin();
p != this->segment_list_.end();
++p)
{
if ((*p)->type() == elfcpp::PT_LOAD)
{
if (load_seg != NULL && load_seg != *p)
gold_unreachable();
load_seg = NULL;
bool are_addresses_set = (*p)->are_addresses_set();
if (are_addresses_set)
{
// When it comes to setting file offsets, we care about
// the physical address.
addr = (*p)->paddr();
}
else if (parameters->options().user_set_Tdata()
&& ((*p)->flags() & elfcpp::PF_W) != 0
&& (!parameters->options().user_set_Tbss()
|| (*p)->has_any_data_sections()))
{
addr = parameters->options().Tdata();
are_addresses_set = true;
}
else if (parameters->options().user_set_Tbss()
&& ((*p)->flags() & elfcpp::PF_W) != 0
&& !(*p)->has_any_data_sections())
{
addr = parameters->options().Tbss();
are_addresses_set = true;
}
uint64_t orig_addr = addr;
uint64_t orig_off = off;
uint64_t aligned_addr = 0;
uint64_t abi_pagesize = target->abi_pagesize();
uint64_t common_pagesize = target->common_pagesize();
if (!parameters->options().nmagic()
&& !parameters->options().omagic())
(*p)->set_minimum_p_align(common_pagesize);
if (!are_addresses_set)
{
// If the last segment was readonly, and this one is
// not, then skip the address forward one page,
// maintaining the same position within the page. This
// lets us store both segments overlapping on a single
// page in the file, but the loader will put them on
// different pages in memory.
addr = align_address(addr, (*p)->maximum_alignment());
aligned_addr = addr;
if (was_readonly && ((*p)->flags() & elfcpp::PF_W) != 0)
{
if ((addr & (abi_pagesize - 1)) != 0)
addr = addr + abi_pagesize;
}
off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
}
if (!parameters->options().nmagic()
&& !parameters->options().omagic())
off = align_file_offset(off, addr, abi_pagesize);
else if (load_seg == NULL)
{
// This is -N or -n with a section script which prevents
// us from using a load segment. We need to ensure that
// the file offset is aligned to the alignment of the
// segment. This is because the linker script
// implicitly assumed a zero offset. If we don't align
// here, then the alignment of the sections in the
// linker script may not match the alignment of the
// sections in the set_section_addresses call below,
// causing an error about dot moving backward.
off = align_address(off, (*p)->maximum_alignment());
}
unsigned int shndx_hold = *pshndx;
uint64_t new_addr = (*p)->set_section_addresses(this, false, addr,
&off, pshndx);
// Now that we know the size of this segment, we may be able
// to save a page in memory, at the cost of wasting some
// file space, by instead aligning to the start of a new
// page. Here we use the real machine page size rather than
// the ABI mandated page size.
if (!are_addresses_set && aligned_addr != addr)
{
uint64_t first_off = (common_pagesize
- (aligned_addr
& (common_pagesize - 1)));
uint64_t last_off = new_addr & (common_pagesize - 1);
if (first_off > 0
&& last_off > 0
&& ((aligned_addr & ~ (common_pagesize - 1))
!= (new_addr & ~ (common_pagesize - 1)))
&& first_off + last_off <= common_pagesize)
{
*pshndx = shndx_hold;
addr = align_address(aligned_addr, common_pagesize);
addr = align_address(addr, (*p)->maximum_alignment());
off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
off = align_file_offset(off, addr, abi_pagesize);
new_addr = (*p)->set_section_addresses(this, true, addr,
&off, pshndx);
}
}
addr = new_addr;
if (((*p)->flags() & elfcpp::PF_W) == 0)
was_readonly = true;
// Implement --check-sections. We know that the segments
// are sorted by LMA.
if (check_sections && last_load_segment != NULL)
{
gold_assert(last_load_segment->paddr() <= (*p)->paddr());
if (last_load_segment->paddr() + last_load_segment->memsz()
> (*p)->paddr())
{
unsigned long long lb1 = last_load_segment->paddr();
unsigned long long le1 = lb1 + last_load_segment->memsz();
unsigned long long lb2 = (*p)->paddr();
unsigned long long le2 = lb2 + (*p)->memsz();
gold_error(_("load segment overlap [0x%llx -> 0x%llx] and "
"[0x%llx -> 0x%llx]"),
lb1, le1, lb2, le2);
}
}
last_load_segment = *p;
}
}
// Handle the non-PT_LOAD segments, setting their offsets from their
// section's offsets.
for (Segment_list::iterator p = this->segment_list_.begin();
p != this->segment_list_.end();
++p)
{
if ((*p)->type() != elfcpp::PT_LOAD)
(*p)->set_offset();
}
// Set the TLS offsets for each section in the PT_TLS segment.
if (this->tls_segment_ != NULL)
this->tls_segment_->set_tls_offsets();
return off;
}
// Set the offsets of all the allocated sections when doing a
// relocatable link. This does the same jobs as set_segment_offsets,
// only for a relocatable link.
off_t
Layout::set_relocatable_section_offsets(Output_data* file_header,
unsigned int *pshndx)
{
off_t off = 0;
file_header->set_address_and_file_offset(0, 0);
off += file_header->data_size();
for (Section_list::iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
{
// We skip unallocated sections here, except that group sections
// have to come first.
if (((*p)->flags() & elfcpp::SHF_ALLOC) == 0
&& (*p)->type() != elfcpp::SHT_GROUP)
continue;
off = align_address(off, (*p)->addralign());
// The linker script might have set the address.
if (!(*p)->is_address_valid())
(*p)->set_address(0);
(*p)->set_file_offset(off);
(*p)->finalize_data_size();
off += (*p)->data_size();
(*p)->set_out_shndx(*pshndx);
++*pshndx;
}
return off;
}
// Set the file offset of all the sections not associated with a
// segment.
off_t
Layout::set_section_offsets(off_t off, Layout::Section_offset_pass pass)
{
for (Section_list::iterator p = this->unattached_section_list_.begin();
p != this->unattached_section_list_.end();
++p)
{
// The symtab section is handled in create_symtab_sections.
if (*p == this->symtab_section_)
continue;
// If we've already set the data size, don't set it again.
if ((*p)->is_offset_valid() && (*p)->is_data_size_valid())
continue;
if (pass == BEFORE_INPUT_SECTIONS_PASS
&& (*p)->requires_postprocessing())
{
(*p)->create_postprocessing_buffer();
this->any_postprocessing_sections_ = true;
}
if (pass == BEFORE_INPUT_SECTIONS_PASS
&& (*p)->after_input_sections())
continue;
else if (pass == POSTPROCESSING_SECTIONS_PASS
&& (!(*p)->after_input_sections()
|| (*p)->type() == elfcpp::SHT_STRTAB))
continue;
else if (pass == STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
&& (!(*p)->after_input_sections()
|| (*p)->type() != elfcpp::SHT_STRTAB))
continue;
off = align_address(off, (*p)->addralign());
(*p)->set_file_offset(off);
(*p)->finalize_data_size();
off += (*p)->data_size();
// At this point the name must be set.
if (pass != STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS)
this->namepool_.add((*p)->name(), false, NULL);
}
return off;
}
// Set the section indexes of all the sections not associated with a
// segment.
unsigned int
Layout::set_section_indexes(unsigned int shndx)
{
for (Section_list::iterator p = this->unattached_section_list_.begin();
p != this->unattached_section_list_.end();
++p)
{
if (!(*p)->has_out_shndx())
{
(*p)->set_out_shndx(shndx);
++shndx;
}
}
return shndx;
}
// Set the section addresses according to the linker script. This is
// only called when we see a SECTIONS clause. This returns the
// program segment which should hold the file header and segment
// headers, if any. It will return NULL if they should not be in a
// segment.
Output_segment*
Layout::set_section_addresses_from_script(Symbol_table* symtab)
{
Script_sections* ss = this->script_options_->script_sections();
gold_assert(ss->saw_sections_clause());
return this->script_options_->set_section_addresses(symtab, this);
}
// Place the orphan sections in the linker script.
void
Layout::place_orphan_sections_in_script()
{
Script_sections* ss = this->script_options_->script_sections();
gold_assert(ss->saw_sections_clause());
// Place each orphaned output section in the script.
for (Section_list::iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
{
if (!(*p)->found_in_sections_clause())
ss->place_orphan(*p);
}
}
// Count the local symbols in the regular symbol table and the dynamic
// symbol table, and build the respective string pools.
void
Layout::count_local_symbols(const Task* task,
const Input_objects* input_objects)
{
// First, figure out an upper bound on the number of symbols we'll
// be inserting into each pool. This helps us create the pools with
// the right size, to avoid unnecessary hashtable resizing.
unsigned int symbol_count = 0;
for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
p != input_objects->relobj_end();
++p)
symbol_count += (*p)->local_symbol_count();
// Go from "upper bound" to "estimate." We overcount for two
// reasons: we double-count symbols that occur in more than one
// object file, and we count symbols that are dropped from the
// output. Add it all together and assume we overcount by 100%.
symbol_count /= 2;
// We assume all symbols will go into both the sympool and dynpool.
this->sympool_.reserve(symbol_count);
this->dynpool_.reserve(symbol_count);
for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
p != input_objects->relobj_end();
++p)
{
Task_lock_obj<Object> tlo(task, *p);
(*p)->count_local_symbols(&this->sympool_, &this->dynpool_);
}
}
// Create the symbol table sections. Here we also set the final
// values of the symbols. At this point all the loadable sections are
// fully laid out. SHNUM is the number of sections so far.
void
Layout::create_symtab_sections(const Input_objects* input_objects,
Symbol_table* symtab,
unsigned int shnum,
off_t* poff)
{
int symsize;
unsigned int align;
if (parameters->target().get_size() == 32)
{
symsize = elfcpp::Elf_sizes<32>::sym_size;
align = 4;
}
else if (parameters->target().get_size() == 64)
{
symsize = elfcpp::Elf_sizes<64>::sym_size;
align = 8;
}
else
gold_unreachable();
off_t off = *poff;
off = align_address(off, align);
off_t startoff = off;
// Save space for the dummy symbol at the start of the section. We
// never bother to write this out--it will just be left as zero.
off += symsize;
unsigned int local_symbol_index = 1;
// Add STT_SECTION symbols for each Output section which needs one.
for (Section_list::iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
{
if (!(*p)->needs_symtab_index())
(*p)->set_symtab_index(-1U);
else
{
(*p)->set_symtab_index(local_symbol_index);
++local_symbol_index;
off += symsize;
}
}
for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
p != input_objects->relobj_end();
++p)
{
unsigned int index = (*p)->finalize_local_symbols(local_symbol_index,
off, symtab);
off += (index - local_symbol_index) * symsize;
local_symbol_index = index;
}
unsigned int local_symcount = local_symbol_index;
gold_assert(static_cast<off_t>(local_symcount * symsize) == off - startoff);
off_t dynoff;
size_t dyn_global_index;
size_t dyncount;
if (this->dynsym_section_ == NULL)
{
dynoff = 0;
dyn_global_index = 0;
dyncount = 0;
}
else
{
dyn_global_index = this->dynsym_section_->info();
off_t locsize = dyn_global_index * this->dynsym_section_->entsize();
dynoff = this->dynsym_section_->offset() + locsize;
dyncount = (this->dynsym_section_->data_size() - locsize) / symsize;
gold_assert(static_cast<off_t>(dyncount * symsize)
== this->dynsym_section_->data_size() - locsize);
}
off = symtab->finalize(off, dynoff, dyn_global_index, dyncount,
&this->sympool_, &local_symcount);
if (!parameters->options().strip_all())
{
this->sympool_.set_string_offsets();
const char* symtab_name = this->namepool_.add(".symtab", false, NULL);
Output_section* osymtab = this->make_output_section(symtab_name,
elfcpp::SHT_SYMTAB,
0, false, false);
this->symtab_section_ = osymtab;
Output_section_data* pos = new Output_data_fixed_space(off - startoff,
align,
"** symtab");
osymtab->add_output_section_data(pos);
// We generate a .symtab_shndx section if we have more than
// SHN_LORESERVE sections. Technically it is possible that we
// don't need one, because it is possible that there are no
// symbols in any of sections with indexes larger than
// SHN_LORESERVE. That is probably unusual, though, and it is
// easier to always create one than to compute section indexes
// twice (once here, once when writing out the symbols).
if (shnum >= elfcpp::SHN_LORESERVE)
{
const char* symtab_xindex_name = this->namepool_.add(".symtab_shndx",
false, NULL);
Output_section* osymtab_xindex =
this->make_output_section(symtab_xindex_name,
elfcpp::SHT_SYMTAB_SHNDX, 0, false,
false);
size_t symcount = (off - startoff) / symsize;
this->symtab_xindex_ = new Output_symtab_xindex(symcount);
osymtab_xindex->add_output_section_data(this->symtab_xindex_);
osymtab_xindex->set_link_section(osymtab);
osymtab_xindex->set_addralign(4);
osymtab_xindex->set_entsize(4);
osymtab_xindex->set_after_input_sections();
// This tells the driver code to wait until the symbol table
// has written out before writing out the postprocessing
// sections, including the .symtab_shndx section.
this->any_postprocessing_sections_ = true;
}
const char* strtab_name = this->namepool_.add(".strtab", false, NULL);
Output_section* ostrtab = this->make_output_section(strtab_name,
elfcpp::SHT_STRTAB,
0, false, false);
Output_section_data* pstr = new Output_data_strtab(&this->sympool_);
ostrtab->add_output_section_data(pstr);
osymtab->set_file_offset(startoff);
osymtab->finalize_data_size();
osymtab->set_link_section(ostrtab);
osymtab->set_info(local_symcount);
osymtab->set_entsize(symsize);
*poff = off;
}
}
// Create the .shstrtab section, which holds the names of the
// sections. At the time this is called, we have created all the
// output sections except .shstrtab itself.
Output_section*
Layout::create_shstrtab()
{
// FIXME: We don't need to create a .shstrtab section if we are
// stripping everything.
const char* name = this->namepool_.add(".shstrtab", false, NULL);
Output_section* os = this->make_output_section(name, elfcpp::SHT_STRTAB, 0,
false, false);
// We can't write out this section until we've set all the section
// names, and we don't set the names of compressed output sections
// until relocations are complete.
os->set_after_input_sections();
Output_section_data* posd = new Output_data_strtab(&this->namepool_);
os->add_output_section_data(posd);
return os;
}
// Create the section headers. SIZE is 32 or 64. OFF is the file
// offset.
void
Layout::create_shdrs(const Output_section* shstrtab_section, off_t* poff)
{
Output_section_headers* oshdrs;
oshdrs = new Output_section_headers(this,
&this->segment_list_,
&this->section_list_,
&this->unattached_section_list_,
&this->namepool_,
shstrtab_section);
off_t off = align_address(*poff, oshdrs->addralign());
oshdrs->set_address_and_file_offset(0, off);
off += oshdrs->data_size();
*poff = off;
this->section_headers_ = oshdrs;
}
// Count the allocated sections.
size_t
Layout::allocated_output_section_count() const
{
size_t section_count = 0;
for (Segment_list::const_iterator p = this->segment_list_.begin();
p != this->segment_list_.end();
++p)
section_count += (*p)->output_section_count();
return section_count;
}
// Create the dynamic symbol table.
void
Layout::create_dynamic_symtab(const Input_objects* input_objects,
Symbol_table* symtab,
Output_section **pdynstr,
unsigned int* plocal_dynamic_count,
std::vector<Symbol*>* pdynamic_symbols,
Versions* pversions)
{
// Count all the symbols in the dynamic symbol table, and set the
// dynamic symbol indexes.
// Skip symbol 0, which is always all zeroes.
unsigned int index = 1;
// Add STT_SECTION symbols for each Output section which needs one.
for (Section_list::iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
{
if (!(*p)->needs_dynsym_index())
(*p)->set_dynsym_index(-1U);
else
{
(*p)->set_dynsym_index(index);
++index;
}
}
// Count the local symbols that need to go in the dynamic symbol table,
// and set the dynamic symbol indexes.
for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
p != input_objects->relobj_end();
++p)
{
unsigned int new_index = (*p)->set_local_dynsym_indexes(index);
index = new_index;
}
unsigned int local_symcount = index;
*plocal_dynamic_count = local_symcount;
index = symtab->set_dynsym_indexes(index, pdynamic_symbols,
&this->dynpool_, pversions);
int symsize;
unsigned int align;
const int size = parameters->target().get_size();
if (size == 32)
{
symsize = elfcpp::Elf_sizes<32>::sym_size;
align = 4;
}
else if (size == 64)
{
symsize = elfcpp::Elf_sizes<64>::sym_size;
align = 8;
}
else
gold_unreachable();
// Create the dynamic symbol table section.
Output_section* dynsym = this->choose_output_section(NULL, ".dynsym",
elfcpp::SHT_DYNSYM,
elfcpp::SHF_ALLOC,
false, false, true);
Output_section_data* odata = new Output_data_fixed_space(index * symsize,
align,
"** dynsym");
dynsym->add_output_section_data(odata);
dynsym->set_info(local_symcount);
dynsym->set_entsize(symsize);
dynsym->set_addralign(align);
this->dynsym_section_ = dynsym;
Output_data_dynamic* const odyn = this->dynamic_data_;
odyn->add_section_address(elfcpp::DT_SYMTAB, dynsym);
odyn->add_constant(elfcpp::DT_SYMENT, symsize);
// If there are more than SHN_LORESERVE allocated sections, we
// create a .dynsym_shndx section. It is possible that we don't
// need one, because it is possible that there are no dynamic
// symbols in any of the sections with indexes larger than
// SHN_LORESERVE. This is probably unusual, though, and at this
// time we don't know the actual section indexes so it is
// inconvenient to check.
if (this->allocated_output_section_count() >= elfcpp::SHN_LORESERVE)
{
Output_section* dynsym_xindex =
this->choose_output_section(NULL, ".dynsym_shndx",
elfcpp::SHT_SYMTAB_SHNDX,
elfcpp::SHF_ALLOC,
false, false, true);
this->dynsym_xindex_ = new Output_symtab_xindex(index);
dynsym_xindex->add_output_section_data(this->dynsym_xindex_);
dynsym_xindex->set_link_section(dynsym);
dynsym_xindex->set_addralign(4);
dynsym_xindex->set_entsize(4);
dynsym_xindex->set_after_input_sections();
// This tells the driver code to wait until the symbol table has
// written out before writing out the postprocessing sections,
// including the .dynsym_shndx section.
this->any_postprocessing_sections_ = true;
}
// Create the dynamic string table section.
Output_section* dynstr = this->choose_output_section(NULL, ".dynstr",
elfcpp::SHT_STRTAB,
elfcpp::SHF_ALLOC,
false, false, true);
Output_section_data* strdata = new Output_data_strtab(&this->dynpool_);
dynstr->add_output_section_data(strdata);
dynsym->set_link_section(dynstr);
this->dynamic_section_->set_link_section(dynstr);
odyn->add_section_address(elfcpp::DT_STRTAB, dynstr);
odyn->add_section_size(elfcpp::DT_STRSZ, dynstr);
*pdynstr = dynstr;
// Create the hash tables.
if (strcmp(parameters->options().hash_style(), "sysv") == 0
|| strcmp(parameters->options().hash_style(), "both") == 0)
{
unsigned char* phash;
unsigned int hashlen;
Dynobj::create_elf_hash_table(*pdynamic_symbols, local_symcount,
&phash, &hashlen);
Output_section* hashsec = this->choose_output_section(NULL, ".hash",
elfcpp::SHT_HASH,
elfcpp::SHF_ALLOC,
false, false, true);
Output_section_data* hashdata = new Output_data_const_buffer(phash,
hashlen,
align,
"** hash");
hashsec->add_output_section_data(hashdata);
hashsec->set_link_section(dynsym);
hashsec->set_entsize(4);
odyn->add_section_address(elfcpp::DT_HASH, hashsec);
}
if (strcmp(parameters->options().hash_style(), "gnu") == 0
|| strcmp(parameters->options().hash_style(), "both") == 0)
{
unsigned char* phash;
unsigned int hashlen;
Dynobj::create_gnu_hash_table(*pdynamic_symbols, local_symcount,
&phash, &hashlen);
Output_section* hashsec = this->choose_output_section(NULL, ".gnu.hash",
elfcpp::SHT_GNU_HASH,
elfcpp::SHF_ALLOC,
false, false, true);
Output_section_data* hashdata = new Output_data_const_buffer(phash,
hashlen,
align,
"** hash");
hashsec->add_output_section_data(hashdata);
hashsec->set_link_section(dynsym);
hashsec->set_entsize(4);
odyn->add_section_address(elfcpp::DT_GNU_HASH, hashsec);
}
}
// Assign offsets to each local portion of the dynamic symbol table.
void
Layout::assign_local_dynsym_offsets(const Input_objects* input_objects)
{
Output_section* dynsym = this->dynsym_section_;
gold_assert(dynsym != NULL);
off_t off = dynsym->offset();
// Skip the dummy symbol at the start of the section.
off += dynsym->entsize();
for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
p != input_objects->relobj_end();
++p)
{
unsigned int count = (*p)->set_local_dynsym_offset(off);
off += count * dynsym->entsize();
}
}
// Create the version sections.
void
Layout::create_version_sections(const Versions* versions,
const Symbol_table* symtab,
unsigned int local_symcount,
const std::vector<Symbol*>& dynamic_symbols,
const Output_section* dynstr)
{
if (!versions->any_defs() && !versions->any_needs())
return;
switch (parameters->size_and_endianness())
{
#ifdef HAVE_TARGET_32_LITTLE
case Parameters::TARGET_32_LITTLE:
this->sized_create_version_sections<32, false>(versions, symtab,
local_symcount,
dynamic_symbols, dynstr);
break;
#endif
#ifdef HAVE_TARGET_32_BIG
case Parameters::TARGET_32_BIG:
this->sized_create_version_sections<32, true>(versions, symtab,
local_symcount,
dynamic_symbols, dynstr);
break;
#endif
#ifdef HAVE_TARGET_64_LITTLE
case Parameters::TARGET_64_LITTLE:
this->sized_create_version_sections<64, false>(versions, symtab,
local_symcount,
dynamic_symbols, dynstr);
break;
#endif
#ifdef HAVE_TARGET_64_BIG
case Parameters::TARGET_64_BIG:
this->sized_create_version_sections<64, true>(versions, symtab,
local_symcount,
dynamic_symbols, dynstr);
break;
#endif
default:
gold_unreachable();
}
}
// Create the version sections, sized version.
template<int size, bool big_endian>
void
Layout::sized_create_version_sections(
const Versions* versions,
const Symbol_table* symtab,
unsigned int local_symcount,
const std::vector<Symbol*>& dynamic_symbols,
const Output_section* dynstr)
{
Output_section* vsec = this->choose_output_section(NULL, ".gnu.version",
elfcpp::SHT_GNU_versym,
elfcpp::SHF_ALLOC,
false, false, true);
unsigned char* vbuf;
unsigned int vsize;
versions->symbol_section_contents<size, big_endian>(symtab, &this->dynpool_,
local_symcount,
dynamic_symbols,
&vbuf, &vsize);
Output_section_data* vdata = new Output_data_const_buffer(vbuf, vsize, 2,
"** versions");
vsec->add_output_section_data(vdata);
vsec->set_entsize(2);
vsec->set_link_section(this->dynsym_section_);
Output_data_dynamic* const odyn = this->dynamic_data_;
odyn->add_section_address(elfcpp::DT_VERSYM, vsec);
if (versions->any_defs())
{
Output_section* vdsec;
vdsec= this->choose_output_section(NULL, ".gnu.version_d",
elfcpp::SHT_GNU_verdef,
elfcpp::SHF_ALLOC,
false, false, true);
unsigned char* vdbuf;
unsigned int vdsize;
unsigned int vdentries;
versions->def_section_contents<size, big_endian>(&this->dynpool_, &vdbuf,
&vdsize, &vdentries);
Output_section_data* vddata =
new Output_data_const_buffer(vdbuf, vdsize, 4, "** version defs");
vdsec->add_output_section_data(vddata);
vdsec->set_link_section(dynstr);
vdsec->set_info(vdentries);
odyn->add_section_address(elfcpp::DT_VERDEF, vdsec);
odyn->add_constant(elfcpp::DT_VERDEFNUM, vdentries);
}
if (versions->any_needs())
{
Output_section* vnsec;
vnsec = this->choose_output_section(NULL, ".gnu.version_r",
elfcpp::SHT_GNU_verneed,
elfcpp::SHF_ALLOC,
false, false, true);
unsigned char* vnbuf;
unsigned int vnsize;
unsigned int vnentries;
versions->need_section_contents<size, big_endian>(&this->dynpool_,
&vnbuf, &vnsize,
&vnentries);
Output_section_data* vndata =
new Output_data_const_buffer(vnbuf, vnsize, 4, "** version refs");
vnsec->add_output_section_data(vndata);
vnsec->set_link_section(dynstr);
vnsec->set_info(vnentries);
odyn->add_section_address(elfcpp::DT_VERNEED, vnsec);
odyn->add_constant(elfcpp::DT_VERNEEDNUM, vnentries);
}
}
// Create the .interp section and PT_INTERP segment.
void
Layout::create_interp(const Target* target)
{
const char* interp = parameters->options().dynamic_linker();
if (interp == NULL)
{
interp = target->dynamic_linker();
gold_assert(interp != NULL);
}
size_t len = strlen(interp) + 1;
Output_section_data* odata = new Output_data_const(interp, len, 1);
Output_section* osec = this->choose_output_section(NULL, ".interp",
elfcpp::SHT_PROGBITS,
elfcpp::SHF_ALLOC,
false, true, true);
osec->add_output_section_data(odata);
if (!this->script_options_->saw_phdrs_clause())
{
Output_segment* oseg = this->make_output_segment(elfcpp::PT_INTERP,
elfcpp::PF_R);
oseg->add_output_section(osec, elfcpp::PF_R, false);
}
}
// Finish the .dynamic section and PT_DYNAMIC segment.
void
Layout::finish_dynamic_section(const Input_objects* input_objects,
const Symbol_table* symtab)
{
if (!this->script_options_->saw_phdrs_clause())
{
Output_segment* oseg = this->make_output_segment(elfcpp::PT_DYNAMIC,
(elfcpp::PF_R
| elfcpp::PF_W));
oseg->add_output_section(this->dynamic_section_,
elfcpp::PF_R | elfcpp::PF_W,
false);
}
Output_data_dynamic* const odyn = this->dynamic_data_;
for (Input_objects::Dynobj_iterator p = input_objects->dynobj_begin();
p != input_objects->dynobj_end();
++p)
{
if (!(*p)->is_needed()
&& (*p)->input_file()->options().as_needed())
{
// This dynamic object was linked with --as-needed, but it
// is not needed.
continue;
}
odyn->add_string(elfcpp::DT_NEEDED, (*p)->soname());
}
if (parameters->options().shared())
{
const char* soname = parameters->options().soname();
if (soname != NULL)
odyn->add_string(elfcpp::DT_SONAME, soname);
}
Symbol* sym = symtab->lookup(parameters->options().init());
if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
odyn->add_symbol(elfcpp::DT_INIT, sym);
sym = symtab->lookup(parameters->options().fini());
if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
odyn->add_symbol(elfcpp::DT_FINI, sym);
// Look for .init_array, .preinit_array and .fini_array by checking
// section types.
for(Layout::Section_list::const_iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
switch((*p)->type())
{
case elfcpp::SHT_FINI_ARRAY:
odyn->add_section_address(elfcpp::DT_FINI_ARRAY, *p);
odyn->add_section_size(elfcpp::DT_FINI_ARRAYSZ, *p);
break;
case elfcpp::SHT_INIT_ARRAY:
odyn->add_section_address(elfcpp::DT_INIT_ARRAY, *p);
odyn->add_section_size(elfcpp::DT_INIT_ARRAYSZ, *p);
break;
case elfcpp::SHT_PREINIT_ARRAY:
odyn->add_section_address(elfcpp::DT_PREINIT_ARRAY, *p);
odyn->add_section_size(elfcpp::DT_PREINIT_ARRAYSZ, *p);
break;
default:
break;
}
// Add a DT_RPATH entry if needed.
const General_options::Dir_list& rpath(parameters->options().rpath());
if (!rpath.empty())
{
std::string rpath_val;
for (General_options::Dir_list::const_iterator p = rpath.begin();
p != rpath.end();
++p)
{
if (rpath_val.empty())
rpath_val = p->name();
else
{
// Eliminate duplicates.
General_options::Dir_list::const_iterator q;
for (q = rpath.begin(); q != p; ++q)
if (q->name() == p->name())
break;
if (q == p)
{
rpath_val += ':';
rpath_val += p->name();
}
}
}
odyn->add_string(elfcpp::DT_RPATH, rpath_val);
if (parameters->options().enable_new_dtags())
odyn->add_string(elfcpp::DT_RUNPATH, rpath_val);
}
// Look for text segments that have dynamic relocations.
bool have_textrel = false;
if (!this->script_options_->saw_sections_clause())
{
for (Segment_list::const_iterator p = this->segment_list_.begin();
p != this->segment_list_.end();
++p)
{
if (((*p)->flags() & elfcpp::PF_W) == 0
&& (*p)->dynamic_reloc_count() > 0)
{
have_textrel = true;
break;
}
}
}
else
{
// We don't know the section -> segment mapping, so we are
// conservative and just look for readonly sections with
// relocations. If those sections wind up in writable segments,
// then we have created an unnecessary DT_TEXTREL entry.
for (Section_list::const_iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
{
if (((*p)->flags() & elfcpp::SHF_ALLOC) != 0
&& ((*p)->flags() & elfcpp::SHF_WRITE) == 0
&& ((*p)->dynamic_reloc_count() > 0))
{
have_textrel = true;
break;
}
}
}
// Add a DT_FLAGS entry. We add it even if no flags are set so that
// post-link tools can easily modify these flags if desired.
unsigned int flags = 0;
if (have_textrel)
{
// Add a DT_TEXTREL for compatibility with older loaders.
odyn->add_constant(elfcpp::DT_TEXTREL, 0);
flags |= elfcpp::DF_TEXTREL;
}
if (parameters->options().shared() && this->has_static_tls())
flags |= elfcpp::DF_STATIC_TLS;
if (parameters->options().origin())
flags |= elfcpp::DF_ORIGIN;
if (parameters->options().Bsymbolic())
{
flags |= elfcpp::DF_SYMBOLIC;
// Add DT_SYMBOLIC for compatibility with older loaders.
odyn->add_constant(elfcpp::DT_SYMBOLIC, 0);
}
if (parameters->options().now())
flags |= elfcpp::DF_BIND_NOW;
odyn->add_constant(elfcpp::DT_FLAGS, flags);
flags = 0;
if (parameters->options().initfirst())
flags |= elfcpp::DF_1_INITFIRST;
if (parameters->options().interpose())
flags |= elfcpp::DF_1_INTERPOSE;
if (parameters->options().loadfltr())
flags |= elfcpp::DF_1_LOADFLTR;
if (parameters->options().nodefaultlib())
flags |= elfcpp::DF_1_NODEFLIB;
if (parameters->options().nodelete())
flags |= elfcpp::DF_1_NODELETE;
if (parameters->options().nodlopen())
flags |= elfcpp::DF_1_NOOPEN;
if (parameters->options().nodump())
flags |= elfcpp::DF_1_NODUMP;
if (!parameters->options().shared())
flags &= ~(elfcpp::DF_1_INITFIRST
| elfcpp::DF_1_NODELETE
| elfcpp::DF_1_NOOPEN);
if (parameters->options().origin())
flags |= elfcpp::DF_1_ORIGIN;
if (parameters->options().now())
flags |= elfcpp::DF_1_NOW;
if (flags)
odyn->add_constant(elfcpp::DT_FLAGS_1, flags);
}
// The mapping of input section name prefixes to output section names.
// In some cases one prefix is itself a prefix of another prefix; in
// such a case the longer prefix must come first. These prefixes are
// based on the GNU linker default ELF linker script.
#define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
const Layout::Section_name_mapping Layout::section_name_mapping[] =
{
MAPPING_INIT(".text.", ".text"),
MAPPING_INIT(".ctors.", ".ctors"),
MAPPING_INIT(".dtors.", ".dtors"),
MAPPING_INIT(".rodata.", ".rodata"),
MAPPING_INIT(".data.rel.ro.local", ".data.rel.ro.local"),
MAPPING_INIT(".data.rel.ro", ".data.rel.ro"),
MAPPING_INIT(".data.", ".data"),
MAPPING_INIT(".bss.", ".bss"),
MAPPING_INIT(".tdata.", ".tdata"),
MAPPING_INIT(".tbss.", ".tbss"),
MAPPING_INIT(".init_array.", ".init_array"),
MAPPING_INIT(".fini_array.", ".fini_array"),
MAPPING_INIT(".sdata.", ".sdata"),
MAPPING_INIT(".sbss.", ".sbss"),
// FIXME: In the GNU linker, .sbss2 and .sdata2 are handled
// differently depending on whether it is creating a shared library.
MAPPING_INIT(".sdata2.", ".sdata"),
MAPPING_INIT(".sbss2.", ".sbss"),
MAPPING_INIT(".lrodata.", ".lrodata"),
MAPPING_INIT(".ldata.", ".ldata"),
MAPPING_INIT(".lbss.", ".lbss"),
MAPPING_INIT(".gcc_except_table.", ".gcc_except_table"),
MAPPING_INIT(".gnu.linkonce.d.rel.ro.local.", ".data.rel.ro.local"),
MAPPING_INIT(".gnu.linkonce.d.rel.ro.", ".data.rel.ro"),
MAPPING_INIT(".gnu.linkonce.t.", ".text"),
MAPPING_INIT(".gnu.linkonce.r.", ".rodata"),
MAPPING_INIT(".gnu.linkonce.d.", ".data"),
MAPPING_INIT(".gnu.linkonce.b.", ".bss"),
MAPPING_INIT(".gnu.linkonce.s.", ".sdata"),
MAPPING_INIT(".gnu.linkonce.sb.", ".sbss"),
MAPPING_INIT(".gnu.linkonce.s2.", ".sdata"),
MAPPING_INIT(".gnu.linkonce.sb2.", ".sbss"),
MAPPING_INIT(".gnu.linkonce.wi.", ".debug_info"),
MAPPING_INIT(".gnu.linkonce.td.", ".tdata"),
MAPPING_INIT(".gnu.linkonce.tb.", ".tbss"),
MAPPING_INIT(".gnu.linkonce.lr.", ".lrodata"),
MAPPING_INIT(".gnu.linkonce.l.", ".ldata"),
MAPPING_INIT(".gnu.linkonce.lb.", ".lbss"),
MAPPING_INIT(".ARM.extab.", ".ARM.extab"),
MAPPING_INIT(".gnu.linkonce.armextab.", ".ARM.extab"),
MAPPING_INIT(".ARM.exidx.", ".ARM.exidx"),
MAPPING_INIT(".gnu.linkonce.armexidx.", ".ARM.exidx"),
};
#undef MAPPING_INIT
const int Layout::section_name_mapping_count =
(sizeof(Layout::section_name_mapping)
/ sizeof(Layout::section_name_mapping[0]));
// Choose the output section name to use given an input section name.
// Set *PLEN to the length of the name. *PLEN is initialized to the
// length of NAME.
const char*
Layout::output_section_name(const char* name, size_t* plen)
{
// gcc 4.3 generates the following sorts of section names when it
// needs a section name specific to a function:
// .text.FN
// .rodata.FN
// .sdata2.FN
// .data.FN
// .data.rel.FN
// .data.rel.local.FN
// .data.rel.ro.FN
// .data.rel.ro.local.FN
// .sdata.FN
// .bss.FN
// .sbss.FN
// .tdata.FN
// .tbss.FN
// The GNU linker maps all of those to the part before the .FN,
// except that .data.rel.local.FN is mapped to .data, and
// .data.rel.ro.local.FN is mapped to .data.rel.ro. The sections
// beginning with .data.rel.ro.local are grouped together.
// For an anonymous namespace, the string FN can contain a '.'.
// Also of interest: .rodata.strN.N, .rodata.cstN, both of which the
// GNU linker maps to .rodata.
// The .data.rel.ro sections are used with -z relro. The sections
// are recognized by name. We use the same names that the GNU
// linker does for these sections.
// It is hard to handle this in a principled way, so we don't even
// try. We use a table of mappings. If the input section name is
// not found in the table, we simply use it as the output section
// name.
const Section_name_mapping* psnm = section_name_mapping;
for (int i = 0; i < section_name_mapping_count; ++i, ++psnm)
{
if (strncmp(name, psnm->from, psnm->fromlen) == 0)
{
*plen = psnm->tolen;
return psnm->to;
}
}
return name;
}
// Check if a comdat group or .gnu.linkonce section with the given
// NAME is selected for the link. If there is already a section,
// *KEPT_SECTION is set to point to the existing section and the
// function returns false. Otherwise, OBJECT, SHNDX, IS_COMDAT, and
// IS_GROUP_NAME are recorded for this NAME in the layout object,
// *KEPT_SECTION is set to the internal copy and the function returns
// true.
bool
Layout::find_or_add_kept_section(const std::string& name,
Relobj* object,
unsigned int shndx,
bool is_comdat,
bool is_group_name,
Kept_section** kept_section)
{
// It's normal to see a couple of entries here, for the x86 thunk
// sections. If we see more than a few, we're linking a C++
// program, and we resize to get more space to minimize rehashing.
if (this->signatures_.size() > 4
&& !this->resized_signatures_)
{
reserve_unordered_map(&this->signatures_,
this->number_of_input_files_ * 64);
this->resized_signatures_ = true;
}
Kept_section candidate;
std::pair<Signatures::iterator, bool> ins =
this->signatures_.insert(std::make_pair(name, candidate));
if (kept_section != NULL)
*kept_section = &ins.first->second;
if (ins.second)
{
// This is the first time we've seen this signature.
ins.first->second.set_object(object);
ins.first->second.set_shndx(shndx);
if (is_comdat)
ins.first->second.set_is_comdat();
if (is_group_name)
ins.first->second.set_is_group_name();
return true;
}
// We have already seen this signature.
if (ins.first->second.is_group_name())
{
// We've already seen a real section group with this signature.
// If the kept group is from a plugin object, and we're in the
// replacement phase, accept the new one as a replacement.
if (ins.first->second.object() == NULL
&& parameters->options().plugins()->in_replacement_phase())
{
ins.first->second.set_object(object);
ins.first->second.set_shndx(shndx);
return true;
}
return false;
}
else if (is_group_name)
{
// This is a real section group, and we've already seen a
// linkonce section with this signature. Record that we've seen
// a section group, and don't include this section group.
ins.first->second.set_is_group_name();
return false;
}
else
{
// We've already seen a linkonce section and this is a linkonce
// section. These don't block each other--this may be the same
// symbol name with different section types.
return true;
}
}
// Store the allocated sections into the section list.
void
Layout::get_allocated_sections(Section_list* section_list) const
{
for (Section_list::const_iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
if (((*p)->flags() & elfcpp::SHF_ALLOC) != 0)
section_list->push_back(*p);
}
// Create an output segment.
Output_segment*
Layout::make_output_segment(elfcpp::Elf_Word type, elfcpp::Elf_Word flags)
{
gold_assert(!parameters->options().relocatable());
Output_segment* oseg = new Output_segment(type, flags);
this->segment_list_.push_back(oseg);
if (type == elfcpp::PT_TLS)
this->tls_segment_ = oseg;
else if (type == elfcpp::PT_GNU_RELRO)
this->relro_segment_ = oseg;
return oseg;
}
// Write out the Output_sections. Most won't have anything to write,
// since most of the data will come from input sections which are
// handled elsewhere. But some Output_sections do have Output_data.
void
Layout::write_output_sections(Output_file* of) const
{
for (Section_list::const_iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
{
if (!(*p)->after_input_sections())
(*p)->write(of);
}
}
// Write out data not associated with a section or the symbol table.
void
Layout::write_data(const Symbol_table* symtab, Output_file* of) const
{
if (!parameters->options().strip_all())
{
const Output_section* symtab_section = this->symtab_section_;
for (Section_list::const_iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
{
if ((*p)->needs_symtab_index())
{
gold_assert(symtab_section != NULL);
unsigned int index = (*p)->symtab_index();
gold_assert(index > 0 && index != -1U);
off_t off = (symtab_section->offset()
+ index * symtab_section->entsize());
symtab->write_section_symbol(*p, this->symtab_xindex_, of, off);
}
}
}
const Output_section* dynsym_section = this->dynsym_section_;
for (Section_list::const_iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
{
if ((*p)->needs_dynsym_index())
{
gold_assert(dynsym_section != NULL);
unsigned int index = (*p)->dynsym_index();
gold_assert(index > 0 && index != -1U);
off_t off = (dynsym_section->offset()
+ index * dynsym_section->entsize());
symtab->write_section_symbol(*p, this->dynsym_xindex_, of, off);
}
}
// Write out the Output_data which are not in an Output_section.
for (Data_list::const_iterator p = this->special_output_list_.begin();
p != this->special_output_list_.end();
++p)
(*p)->write(of);
}
// Write out the Output_sections which can only be written after the
// input sections are complete.
void
Layout::write_sections_after_input_sections(Output_file* of)
{
// Determine the final section offsets, and thus the final output
// file size. Note we finalize the .shstrab last, to allow the
// after_input_section sections to modify their section-names before
// writing.
if (this->any_postprocessing_sections_)
{
off_t off = this->output_file_size_;
off = this->set_section_offsets(off, POSTPROCESSING_SECTIONS_PASS);
// Now that we've finalized the names, we can finalize the shstrab.
off =
this->set_section_offsets(off,
STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS);
if (off > this->output_file_size_)
{
of->resize(off);
this->output_file_size_ = off;
}
}
for (Section_list::const_iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
{
if ((*p)->after_input_sections())
(*p)->write(of);
}
this->section_headers_->write(of);
}
// If the build ID requires computing a checksum, do so here, and
// write it out. We compute a checksum over the entire file because
// that is simplest.
void
Layout::write_build_id(Output_file* of) const
{
if (this->build_id_note_ == NULL)
return;
const unsigned char* iv = of->get_input_view(0, this->output_file_size_);
unsigned char* ov = of->get_output_view(this->build_id_note_->offset(),
this->build_id_note_->data_size());
const char* style = parameters->options().build_id();
if (strcmp(style, "sha1") == 0)
{
sha1_ctx ctx;
sha1_init_ctx(&ctx);
sha1_process_bytes(iv, this->output_file_size_, &ctx);
sha1_finish_ctx(&ctx, ov);
}
else if (strcmp(style, "md5") == 0)
{
md5_ctx ctx;
md5_init_ctx(&ctx);
md5_process_bytes(iv, this->output_file_size_, &ctx);
md5_finish_ctx(&ctx, ov);
}
else
gold_unreachable();
of->write_output_view(this->build_id_note_->offset(),
this->build_id_note_->data_size(),
ov);
of->free_input_view(0, this->output_file_size_, iv);
}
// Write out a binary file. This is called after the link is
// complete. IN is the temporary output file we used to generate the
// ELF code. We simply walk through the segments, read them from
// their file offset in IN, and write them to their load address in
// the output file. FIXME: with a bit more work, we could support
// S-records and/or Intel hex format here.
void
Layout::write_binary(Output_file* in) const
{
gold_assert(parameters->options().oformat_enum()
== General_options::OBJECT_FORMAT_BINARY);
// Get the size of the binary file.
uint64_t max_load_address = 0;
for (Segment_list::const_iterator p = this->segment_list_.begin();
p != this->segment_list_.end();
++p)
{
if ((*p)->type() == elfcpp::PT_LOAD && (*p)->filesz() > 0)
{
uint64_t max_paddr = (*p)->paddr() + (*p)->filesz();
if (max_paddr > max_load_address)
max_load_address = max_paddr;
}
}
Output_file out(parameters->options().output_file_name());
out.open(max_load_address);
for (Segment_list::const_iterator p = this->segment_list_.begin();
p != this->segment_list_.end();
++p)
{
if ((*p)->type() == elfcpp::PT_LOAD && (*p)->filesz() > 0)
{
const unsigned char* vin = in->get_input_view((*p)->offset(),
(*p)->filesz());
unsigned char* vout = out.get_output_view((*p)->paddr(),
(*p)->filesz());
memcpy(vout, vin, (*p)->filesz());
out.write_output_view((*p)->paddr(), (*p)->filesz(), vout);
in->free_input_view((*p)->offset(), (*p)->filesz(), vin);
}
}
out.close();
}
// Print the output sections to the map file.
void
Layout::print_to_mapfile(Mapfile* mapfile) const
{
for (Segment_list::const_iterator p = this->segment_list_.begin();
p != this->segment_list_.end();
++p)
(*p)->print_sections_to_mapfile(mapfile);
}
// Print statistical information to stderr. This is used for --stats.
void
Layout::print_stats() const
{
this->namepool_.print_stats("section name pool");
this->sympool_.print_stats("output symbol name pool");
this->dynpool_.print_stats("dynamic name pool");
for (Section_list::const_iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
(*p)->print_merge_stats();
}
// Write_sections_task methods.
// We can always run this task.
Task_token*
Write_sections_task::is_runnable()
{
return NULL;
}
// We need to unlock both OUTPUT_SECTIONS_BLOCKER and FINAL_BLOCKER
// when finished.
void
Write_sections_task::locks(Task_locker* tl)
{
tl->add(this, this->output_sections_blocker_);
tl->add(this, this->final_blocker_);
}
// Run the task--write out the data.
void
Write_sections_task::run(Workqueue*)
{
this->layout_->write_output_sections(this->of_);
}
// Write_data_task methods.
// We can always run this task.
Task_token*
Write_data_task::is_runnable()
{
return NULL;
}
// We need to unlock FINAL_BLOCKER when finished.
void
Write_data_task::locks(Task_locker* tl)
{
tl->add(this, this->final_blocker_);
}
// Run the task--write out the data.
void
Write_data_task::run(Workqueue*)
{
this->layout_->write_data(this->symtab_, this->of_);
}
// Write_symbols_task methods.
// We can always run this task.
Task_token*
Write_symbols_task::is_runnable()
{
return NULL;
}
// We need to unlock FINAL_BLOCKER when finished.
void
Write_symbols_task::locks(Task_locker* tl)
{
tl->add(this, this->final_blocker_);
}
// Run the task--write out the symbols.
void
Write_symbols_task::run(Workqueue*)
{
this->symtab_->write_globals(this->sympool_, this->dynpool_,
this->layout_->symtab_xindex(),
this->layout_->dynsym_xindex(), this->of_);
}
// Write_after_input_sections_task methods.
// We can only run this task after the input sections have completed.
Task_token*
Write_after_input_sections_task::is_runnable()
{
if (this->input_sections_blocker_->is_blocked())
return this->input_sections_blocker_;
return NULL;
}
// We need to unlock FINAL_BLOCKER when finished.
void
Write_after_input_sections_task::locks(Task_locker* tl)
{
tl->add(this, this->final_blocker_);
}
// Run the task.
void
Write_after_input_sections_task::run(Workqueue*)
{
this->layout_->write_sections_after_input_sections(this->of_);
}
// Close_task_runner methods.
// Run the task--close the file.
void
Close_task_runner::run(Workqueue*, const Task*)
{
// If we need to compute a checksum for the BUILD if, we do so here.
this->layout_->write_build_id(this->of_);
// If we've been asked to create a binary file, we do so here.
if (this->options_->oformat_enum() != General_options::OBJECT_FORMAT_ELF)
this->layout_->write_binary(this->of_);
this->of_->close();
}
// Instantiate the templates we need. We could use the configure
// script to restrict this to only the ones for implemented targets.
#ifdef HAVE_TARGET_32_LITTLE
template
Output_section*
Layout::layout<32, false>(Sized_relobj<32, false>* object, unsigned int shndx,
const char* name,
const elfcpp::Shdr<32, false>& shdr,
unsigned int, unsigned int, off_t*);
#endif
#ifdef HAVE_TARGET_32_BIG
template
Output_section*
Layout::layout<32, true>(Sized_relobj<32, true>* object, unsigned int shndx,
const char* name,
const elfcpp::Shdr<32, true>& shdr,
unsigned int, unsigned int, off_t*);
#endif
#ifdef HAVE_TARGET_64_LITTLE
template
Output_section*
Layout::layout<64, false>(Sized_relobj<64, false>* object, unsigned int shndx,
const char* name,
const elfcpp::Shdr<64, false>& shdr,
unsigned int, unsigned int, off_t*);
#endif
#ifdef HAVE_TARGET_64_BIG
template
Output_section*
Layout::layout<64, true>(Sized_relobj<64, true>* object, unsigned int shndx,
const char* name,
const elfcpp::Shdr<64, true>& shdr,
unsigned int, unsigned int, off_t*);
#endif
#ifdef HAVE_TARGET_32_LITTLE
template
Output_section*
Layout::layout_reloc<32, false>(Sized_relobj<32, false>* object,
unsigned int reloc_shndx,
const elfcpp::Shdr<32, false>& shdr,
Output_section* data_section,
Relocatable_relocs* rr);
#endif
#ifdef HAVE_TARGET_32_BIG
template
Output_section*
Layout::layout_reloc<32, true>(Sized_relobj<32, true>* object,
unsigned int reloc_shndx,
const elfcpp::Shdr<32, true>& shdr,
Output_section* data_section,
Relocatable_relocs* rr);
#endif
#ifdef HAVE_TARGET_64_LITTLE
template
Output_section*
Layout::layout_reloc<64, false>(Sized_relobj<64, false>* object,
unsigned int reloc_shndx,
const elfcpp::Shdr<64, false>& shdr,
Output_section* data_section,
Relocatable_relocs* rr);
#endif
#ifdef HAVE_TARGET_64_BIG
template
Output_section*
Layout::layout_reloc<64, true>(Sized_relobj<64, true>* object,
unsigned int reloc_shndx,
const elfcpp::Shdr<64, true>& shdr,
Output_section* data_section,
Relocatable_relocs* rr);
#endif
#ifdef HAVE_TARGET_32_LITTLE
template
void
Layout::layout_group<32, false>(Symbol_table* symtab,
Sized_relobj<32, false>* object,
unsigned int,
const char* group_section_name,
const char* signature,
const elfcpp::Shdr<32, false>& shdr,
elfcpp::Elf_Word flags,
std::vector<unsigned int>* shndxes);
#endif
#ifdef HAVE_TARGET_32_BIG
template
void
Layout::layout_group<32, true>(Symbol_table* symtab,
Sized_relobj<32, true>* object,
unsigned int,
const char* group_section_name,
const char* signature,
const elfcpp::Shdr<32, true>& shdr,
elfcpp::Elf_Word flags,
std::vector<unsigned int>* shndxes);
#endif
#ifdef HAVE_TARGET_64_LITTLE
template
void
Layout::layout_group<64, false>(Symbol_table* symtab,
Sized_relobj<64, false>* object,
unsigned int,
const char* group_section_name,
const char* signature,
const elfcpp::Shdr<64, false>& shdr,
elfcpp::Elf_Word flags,
std::vector<unsigned int>* shndxes);
#endif
#ifdef HAVE_TARGET_64_BIG
template
void
Layout::layout_group<64, true>(Symbol_table* symtab,
Sized_relobj<64, true>* object,
unsigned int,
const char* group_section_name,
const char* signature,
const elfcpp::Shdr<64, true>& shdr,
elfcpp::Elf_Word flags,
std::vector<unsigned int>* shndxes);
#endif
#ifdef HAVE_TARGET_32_LITTLE
template
Output_section*
Layout::layout_eh_frame<32, false>(Sized_relobj<32, false>* object,
const unsigned char* symbols,
off_t symbols_size,
const unsigned char* symbol_names,
off_t symbol_names_size,
unsigned int shndx,
const elfcpp::Shdr<32, false>& shdr,
unsigned int reloc_shndx,
unsigned int reloc_type,
off_t* off);
#endif
#ifdef HAVE_TARGET_32_BIG
template
Output_section*
Layout::layout_eh_frame<32, true>(Sized_relobj<32, true>* object,
const unsigned char* symbols,
off_t symbols_size,
const unsigned char* symbol_names,
off_t symbol_names_size,
unsigned int shndx,
const elfcpp::Shdr<32, true>& shdr,
unsigned int reloc_shndx,
unsigned int reloc_type,
off_t* off);
#endif
#ifdef HAVE_TARGET_64_LITTLE
template
Output_section*
Layout::layout_eh_frame<64, false>(Sized_relobj<64, false>* object,
const unsigned char* symbols,
off_t symbols_size,
const unsigned char* symbol_names,
off_t symbol_names_size,
unsigned int shndx,
const elfcpp::Shdr<64, false>& shdr,
unsigned int reloc_shndx,
unsigned int reloc_type,
off_t* off);
#endif
#ifdef HAVE_TARGET_64_BIG
template
Output_section*
Layout::layout_eh_frame<64, true>(Sized_relobj<64, true>* object,
const unsigned char* symbols,
off_t symbols_size,
const unsigned char* symbol_names,
off_t symbol_names_size,
unsigned int shndx,
const elfcpp::Shdr<64, true>& shdr,
unsigned int reloc_shndx,
unsigned int reloc_type,
off_t* off);
#endif
} // End namespace gold.
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