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// layout.cc -- lay out output file sections for gold
// Copyright (C) 2006-2016 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 <fstream>
#include <utility>
#include <fcntl.h>
#include <fnmatch.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 "gdb-index.h"
#include "compressed_output.h"
#include "reduced_debug_output.h"
#include "object.h"
#include "reloc.h"
#include "descriptors.h"
#include "plugin.h"
#include "incremental.h"
#include "layout.h"
namespace gold
{
// Class Free_list.
// The total number of free lists used.
unsigned int Free_list::num_lists = 0;
// The total number of free list nodes used.
unsigned int Free_list::num_nodes = 0;
// The total number of calls to Free_list::remove.
unsigned int Free_list::num_removes = 0;
// The total number of nodes visited during calls to Free_list::remove.
unsigned int Free_list::num_remove_visits = 0;
// The total number of calls to Free_list::allocate.
unsigned int Free_list::num_allocates = 0;
// The total number of nodes visited during calls to Free_list::allocate.
unsigned int Free_list::num_allocate_visits = 0;
// Initialize the free list. Creates a single free list node that
// describes the entire region of length LEN. If EXTEND is true,
// allocate() is allowed to extend the region beyond its initial
// length.
void
Free_list::init(off_t len, bool extend)
{
this->list_.push_front(Free_list_node(0, len));
this->last_remove_ = this->list_.begin();
this->extend_ = extend;
this->length_ = len;
++Free_list::num_lists;
++Free_list::num_nodes;
}
// Remove a chunk from the free list. Because we start with a single
// node that covers the entire section, and remove chunks from it one
// at a time, we do not need to coalesce chunks or handle cases that
// span more than one free node. We expect to remove chunks from the
// free list in order, and we expect to have only a few chunks of free
// space left (corresponding to files that have changed since the last
// incremental link), so a simple linear list should provide sufficient
// performance.
void
Free_list::remove(off_t start, off_t end)
{
if (start == end)
return;
gold_assert(start < end);
++Free_list::num_removes;
Iterator p = this->last_remove_;
if (p->start_ > start)
p = this->list_.begin();
for (; p != this->list_.end(); ++p)
{
++Free_list::num_remove_visits;
// Find a node that wholly contains the indicated region.
if (p->start_ <= start && p->end_ >= end)
{
// Case 1: the indicated region spans the whole node.
// Add some fuzz to avoid creating tiny free chunks.
if (p->start_ + 3 >= start && p->end_ <= end + 3)
p = this->list_.erase(p);
// Case 2: remove a chunk from the start of the node.
else if (p->start_ + 3 >= start)
p->start_ = end;
// Case 3: remove a chunk from the end of the node.
else if (p->end_ <= end + 3)
p->end_ = start;
// Case 4: remove a chunk from the middle, and split
// the node into two.
else
{
Free_list_node newnode(p->start_, start);
p->start_ = end;
this->list_.insert(p, newnode);
++Free_list::num_nodes;
}
this->last_remove_ = p;
return;
}
}
// Did not find a node containing the given chunk. This could happen
// because a small chunk was already removed due to the fuzz.
gold_debug(DEBUG_INCREMENTAL,
"Free_list::remove(%d,%d) not found",
static_cast<int>(start), static_cast<int>(end));
}
// Allocate a chunk of size LEN from the free list. Returns -1ULL
// if a sufficiently large chunk of free space is not found.
// We use a simple first-fit algorithm.
off_t
Free_list::allocate(off_t len, uint64_t align, off_t minoff)
{
gold_debug(DEBUG_INCREMENTAL,
"Free_list::allocate(%08lx, %d, %08lx)",
static_cast<long>(len), static_cast<int>(align),
static_cast<long>(minoff));
if (len == 0)
return align_address(minoff, align);
++Free_list::num_allocates;
// We usually want to drop free chunks smaller than 4 bytes.
// If we need to guarantee a minimum hole size, though, we need
// to keep track of all free chunks.
const int fuzz = this->min_hole_ > 0 ? 0 : 3;
for (Iterator p = this->list_.begin(); p != this->list_.end(); ++p)
{
++Free_list::num_allocate_visits;
off_t start = p->start_ > minoff ? p->start_ : minoff;
start = align_address(start, align);
off_t end = start + len;
if (end > p->end_ && p->end_ == this->length_ && this->extend_)
{
this->length_ = end;
p->end_ = end;
}
if (end == p->end_ || (end <= p->end_ - this->min_hole_))
{
if (p->start_ + fuzz >= start && p->end_ <= end + fuzz)
this->list_.erase(p);
else if (p->start_ + fuzz >= start)
p->start_ = end;
else if (p->end_ <= end + fuzz)
p->end_ = start;
else
{
Free_list_node newnode(p->start_, start);
p->start_ = end;
this->list_.insert(p, newnode);
++Free_list::num_nodes;
}
return start;
}
}
if (this->extend_)
{
off_t start = align_address(this->length_, align);
this->length_ = start + len;
return start;
}
return -1;
}
// Dump the free list (for debugging).
void
Free_list::dump()
{
gold_info("Free list:\n start end length\n");
for (Iterator p = this->list_.begin(); p != this->list_.end(); ++p)
gold_info(" %08lx %08lx %08lx", static_cast<long>(p->start_),
static_cast<long>(p->end_),
static_cast<long>(p->end_ - p->start_));
}
// Print the statistics for the free lists.
void
Free_list::print_stats()
{
fprintf(stderr, _("%s: total free lists: %u\n"),
program_name, Free_list::num_lists);
fprintf(stderr, _("%s: total free list nodes: %u\n"),
program_name, Free_list::num_nodes);
fprintf(stderr, _("%s: calls to Free_list::remove: %u\n"),
program_name, Free_list::num_removes);
fprintf(stderr, _("%s: nodes visited: %u\n"),
program_name, Free_list::num_remove_visits);
fprintf(stderr, _("%s: calls to Free_list::allocate: %u\n"),
program_name, Free_list::num_allocates);
fprintf(stderr, _("%s: nodes visited: %u\n"),
program_name, Free_list::num_allocate_visits);
}
// A Hash_task computes the MD5 checksum of an array of char.
class Hash_task : public Task
{
public:
Hash_task(Output_file* of,
size_t offset,
size_t size,
unsigned char* dst,
Task_token* final_blocker)
: of_(of), offset_(offset), size_(size), dst_(dst),
final_blocker_(final_blocker)
{ }
void
run(Workqueue*)
{
const unsigned char* iv =
this->of_->get_input_view(this->offset_, this->size_);
md5_buffer(reinterpret_cast<const char*>(iv), this->size_, this->dst_);
this->of_->free_input_view(this->offset_, this->size_, iv);
}
Task_token*
is_runnable()
{ return NULL; }
// Unblock FINAL_BLOCKER_ when done.
void
locks(Task_locker* tl)
{ tl->add(this, this->final_blocker_); }
std::string
get_name() const
{ return "Hash_task"; }
private:
Output_file* of_;
const size_t offset_;
const size_t size_;
unsigned char* const dst_;
Task_token* const final_blocker_;
};
// 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,
const Layout::Data_list& relax_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());
gold_assert(relax_outputs.empty());
}
// 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)
{
// See if any of the input definitions violate the One Definition Rule.
// TODO: if this is too slow, do this as a task, rather than inline.
this->symtab_->detect_odr_violations(task, this->options_.output_file_name());
Layout* layout = this->layout_;
off_t file_size = 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_);
layout->print_to_mapfile(this->mapfile_);
}
Output_file* of;
if (layout->incremental_base() == NULL)
{
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);
}
else
{
of = layout->incremental_base()->output_file();
// Apply the incremental relocations for symbols whose values
// have changed. We do this before we resize the file and start
// writing anything else to it, so that we can read the old
// incremental information from the file before (possibly)
// overwriting it.
if (parameters->incremental_update())
layout->incremental_base()->apply_incremental_relocs(this->symtab_,
this->layout_,
of);
of->resize(file_size);
}
// Queue up the final set of tasks.
gold::queue_final_tasks(this->options_, this->input_objects_,
this->symtab_, 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_(),
relax_output_list_(),
section_headers_(NULL),
tls_segment_(NULL),
relro_segment_(NULL),
interp_segment_(NULL),
increase_relro_(0),
symtab_section_(NULL),
symtab_xindex_(NULL),
dynsym_section_(NULL),
dynsym_xindex_(NULL),
dynamic_section_(NULL),
dynamic_symbol_(NULL),
dynamic_data_(NULL),
eh_frame_section_(NULL),
eh_frame_data_(NULL),
added_eh_frame_data_(false),
eh_frame_hdr_section_(NULL),
gdb_index_data_(NULL),
build_id_note_(NULL),
debug_abbrev_(NULL),
debug_info_(NULL),
group_signatures_(),
output_file_size_(-1),
have_added_input_section_(false),
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),
section_ordering_specified_(false),
unique_segment_for_sections_specified_(false),
incremental_inputs_(NULL),
record_output_section_data_from_script_(false),
script_output_section_data_list_(),
segment_states_(NULL),
relaxation_debug_check_(NULL),
section_order_map_(),
section_segment_map_(),
input_section_position_(),
input_section_glob_(),
incremental_base_(NULL),
free_list_()
{
// 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->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();
}
// For incremental links, record the base file to be modified.
void
Layout::set_incremental_base(Incremental_binary* base)
{
this->incremental_base_ = base;
this->free_list_.init(base->output_file()->filesize(), true);
}
// 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;
}
// These are the debug sections that are actually used by gdb.
// Currently, we've checked versions of gdb up to and including 7.4.
// We only check the part of the name that follows ".debug_" or
// ".zdebug_".
static const char* gdb_sections[] =
{
"abbrev",
"addr", // Fission extension
// "aranges", // not used by gdb as of 7.4
"frame",
"gdb_scripts",
"info",
"types",
"line",
"loc",
"macinfo",
"macro",
// "pubnames", // not used by gdb as of 7.4
// "pubtypes", // not used by gdb as of 7.4
// "gnu_pubnames", // Fission extension
// "gnu_pubtypes", // Fission extension
"ranges",
"str",
"str_offsets",
};
// This is the minimum set of sections needed for line numbers.
static const char* lines_only_debug_sections[] =
{
"abbrev",
// "addr", // Fission extension
// "aranges", // not used by gdb as of 7.4
// "frame",
// "gdb_scripts",
"info",
// "types",
"line",
// "loc",
// "macinfo",
// "macro",
// "pubnames", // not used by gdb as of 7.4
// "pubtypes", // not used by gdb as of 7.4
// "gnu_pubnames", // Fission extension
// "gnu_pubtypes", // Fission extension
// "ranges",
"str",
"str_offsets", // Fission extension
};
// These sections are the DWARF fast-lookup tables, and are not needed
// when building a .gdb_index section.
static const char* gdb_fast_lookup_sections[] =
{
"aranges",
"pubnames",
"gnu_pubnames",
"pubtypes",
"gnu_pubtypes",
};
// Returns whether the given debug section is in the list of
// debug-sections-used-by-some-version-of-gdb. SUFFIX is the
// portion of the name following ".debug_" or ".zdebug_".
static inline bool
is_gdb_debug_section(const char* suffix)
{
// 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(suffix, gdb_sections[i]) == 0)
return true;
return false;
}
// Returns whether the given section is needed for lines-only debugging.
static inline bool
is_lines_only_debug_section(const char* suffix)
{
// 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(suffix, lines_only_debug_sections[i]) == 0)
return true;
return false;
}
// Returns whether the given section is a fast-lookup section that
// will not be needed when building a .gdb_index section.
static inline bool
is_gdb_fast_lookup_section(const char* suffix)
{
// We can do this faster: binary search or a hashtable. But why bother?
for (size_t i = 0;
i < sizeof(gdb_fast_lookup_sections)/sizeof(*gdb_fast_lookup_sections);
++i)
if (strcmp(suffix, gdb_fast_lookup_sections[i]) == 0)
return true;
return false;
}
// 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 (is_prefix_of(".debug", secname));
}
// We may see compressed debug sections in input files. Return TRUE
// if this is the name of a compressed debug section.
bool
is_compressed_debug_section(const char* secname)
{
return (is_prefix_of(".zdebug", secname));
}
std::string
corresponding_uncompressed_section_name(std::string secname)
{
gold_assert(secname[0] == '.' && secname[1] == 'z');
std::string ret(".");
ret.append(secname, 2, std::string::npos);
return ret;
}
// Whether to include this section in the link.
template<int size, bool big_endian>
bool
Layout::include_section(Sized_relobj_file<size, big_endian>*, const char* name,
const elfcpp::Shdr<size, big_endian>& shdr)
{
if (!parameters->options().relocatable()
&& (shdr.get_sh_flags() & elfcpp::SHF_EXCLUDE))
return false;
elfcpp::Elf_Word sh_type = shdr.get_sh_type();
if ((sh_type >= elfcpp::SHT_LOOS && sh_type <= elfcpp::SHT_HIOS)
|| (sh_type >= elfcpp::SHT_LOPROC && sh_type <= elfcpp::SHT_HIPROC))
return parameters->target().should_include_section(sh_type);
switch (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());
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 + 7))
return false;
if (is_prefix_of(".zdebug_", name)
&& !is_lines_only_debug_section(name + 8))
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 + 7))
return false;
if (is_prefix_of(".zdebug_", name)
&& !is_gdb_debug_section(name + 8))
return false;
}
if (parameters->options().gdb_index()
&& (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
{
// When building .gdb_index, we can strip .debug_pubnames,
// .debug_pubtypes, and .debug_aranges sections.
if (is_prefix_of(".debug_", name)
&& is_gdb_fast_lookup_section(name + 7))
return false;
if (is_prefix_of(".zdebug_", name)
&& is_gdb_fast_lookup_section(name + 8))
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;
}
// When we put a .ctors or .dtors section with more than one word into
// a .init_array or .fini_array section, we need to reverse the words
// in the .ctors/.dtors section. This is because .init_array executes
// constructors front to back, where .ctors executes them back to
// front, and vice-versa for .fini_array/.dtors. Although we do want
// to remap .ctors/.dtors into .init_array/.fini_array because it can
// be more efficient, we don't want to change the order in which
// constructors/destructors are run. This set just keeps track of
// these sections which need to be reversed. It is only changed by
// Layout::layout. It should be a private member of Layout, but that
// would require layout.h to #include object.h to get the definition
// of Section_id.
static Unordered_set<Section_id, Section_id_hash> ctors_sections_in_init_array;
// Return whether OBJECT/SHNDX is a .ctors/.dtors section mapped to a
// .init_array/.fini_array section.
bool
Layout::is_ctors_in_init_array(Relobj* relobj, unsigned int shndx) const
{
return (ctors_sections_in_init_array.find(Section_id(relobj, shndx))
!= ctors_sections_in_init_array.end());
}
// 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. ORDER is where this should appear
// in the output sections. IS_RELRO is true for a relro section.
Output_section*
Layout::get_output_section(const char* name, Stringpool::Key name_key,
elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
Output_section_order order, bool is_relro)
{
elfcpp::Elf_Word lookup_type = type;
// For lookup purposes, treat INIT_ARRAY, FINI_ARRAY, and
// PREINIT_ARRAY like PROGBITS. This ensures that we combine
// .init_array, .fini_array, and .preinit_array sections by name
// whatever their type in the input file. We do this because the
// types are not always right in the input files.
if (lookup_type == elfcpp::SHT_INIT_ARRAY
|| lookup_type == elfcpp::SHT_FINI_ARRAY
|| lookup_type == elfcpp::SHT_PREINIT_ARRAY)
lookup_type = elfcpp::SHT_PROGBITS;
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(lookup_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 (lookup_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->type() == elfcpp::SHT_INIT_ARRAY
|| same_name->type() == elfcpp::SHT_FINI_ARRAY
|| same_name->type() == elfcpp::SHT_PREINIT_ARRAY)
&& (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(lookup_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, order, is_relro);
ins.first->second = os;
return os;
}
}
// Returns TRUE iff NAME (an input section from RELOBJ) will
// be mapped to an output section that should be KEPT.
bool
Layout::keep_input_section(const Relobj* relobj, const char* name)
{
if (! this->script_options_->saw_sections_clause())
return false;
Script_sections* ss = this->script_options_->script_sections();
const char* file_name = relobj == NULL ? NULL : relobj->name().c_str();
Output_section** output_section_slot;
Script_sections::Section_type script_section_type;
bool keep;
name = ss->output_section_name(file_name, name, &output_section_slot,
&script_section_type, &keep);
return name != NULL && keep;
}
// Clear the input section flags that should not be copied to the
// output section.
elfcpp::Elf_Xword
Layout::get_output_section_flags(elfcpp::Elf_Xword input_section_flags)
{
// Some flags in the input section should not be automatically
// copied to the output section.
input_section_flags &= ~ (elfcpp::SHF_INFO_LINK
| elfcpp::SHF_GROUP
| elfcpp::SHF_COMPRESSED
| elfcpp::SHF_MERGE
| elfcpp::SHF_STRINGS);
// We only clear the SHF_LINK_ORDER flag in for
// a non-relocatable link.
if (!parameters->options().relocatable())
input_section_flags &= ~elfcpp::SHF_LINK_ORDER;
return input_section_flags;
}
// 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. ORDER is where this section should appear in the output
// sections. IS_RELRO is true for a relro section. 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, Output_section_order order,
bool is_relro)
{
// We should not see any input sections after we have attached
// sections to segments.
gold_assert(!is_input_section || !this->sections_are_attached_);
flags = this->get_output_section_flags(flags);
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;
Script_sections::Section_type script_section_type;
const char* orig_name = name;
bool keep;
name = ss->output_section_name(file_name, name, &output_section_slot,
&script_section_type, &keep);
if (name == NULL)
{
gold_debug(DEBUG_SCRIPT, _("Unable to create output section '%s' "
"because it is not allowed by the "
"SECTIONS clause of the linker script"),
orig_name);
// The SECTIONS clause says to discard this input section.
return NULL;
}
// We can only handle script section types ST_NONE and ST_NOLOAD.
switch (script_section_type)
{
case Script_sections::ST_NONE:
break;
case Script_sections::ST_NOLOAD:
flags &= elfcpp::SHF_ALLOC;
break;
default:
gold_unreachable();
}
// 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,
order, is_relro);
os->set_found_in_sections_clause();
// Special handling for NOLOAD sections.
if (script_section_type == Script_sections::ST_NOLOAD)
{
os->set_is_noload();
// The constructor of Output_section sets addresses of non-ALLOC
// sections to 0 by default. We don't want that for NOLOAD
// sections even if they have no SHF_ALLOC flag.
if ((os->flags() & elfcpp::SHF_ALLOC) == 0
&& os->is_address_valid())
{
gold_assert(os->address() == 0
&& !os->is_offset_valid()
&& !os->is_data_size_valid());
os->reset_address_and_file_offset();
}
}
*output_section_slot = os;
return os;
}
}
// FIXME: Handle SHF_OS_NONCONFORMING somewhere.
size_t len = strlen(name);
std::string uncompressed_name;
// Compressed debug sections should be mapped to the corresponding
// uncompressed section.
if (is_compressed_debug_section(name))
{
uncompressed_name =
corresponding_uncompressed_section_name(std::string(name, len));
name = uncompressed_name.c_str();
len = uncompressed_name.length();
}
// Turn NAME from the name of the input section into the name of the
// output section.
if (is_input_section
&& !this->script_options_->saw_sections_clause()
&& !parameters->options().relocatable())
{
const char *orig_name = name;
name = parameters->target().output_section_name(relobj, name, &len);
if (name == NULL)
name = Layout::output_section_name(relobj, orig_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, order, is_relro);
}
// For incremental links, record the initial fixed layout of a section
// from the base file, and return a pointer to the Output_section.
template<int size, bool big_endian>
Output_section*
Layout::init_fixed_output_section(const char* name,
elfcpp::Shdr<size, big_endian>& shdr)
{
unsigned int sh_type = shdr.get_sh_type();
// We preserve the layout of PROGBITS, NOBITS, INIT_ARRAY, FINI_ARRAY,
// PRE_INIT_ARRAY, and NOTE sections.
// All others will be created from scratch and reallocated.
if (!can_incremental_update(sh_type))
return NULL;
// If we're generating a .gdb_index section, we need to regenerate
// it from scratch.
if (parameters->options().gdb_index()
&& sh_type == elfcpp::SHT_PROGBITS
&& strcmp(name, ".gdb_index") == 0)
return NULL;
typename elfcpp::Elf_types<size>::Elf_Addr sh_addr = shdr.get_sh_addr();
typename elfcpp::Elf_types<size>::Elf_Off sh_offset = shdr.get_sh_offset();
typename elfcpp::Elf_types<size>::Elf_WXword sh_size = shdr.get_sh_size();
typename elfcpp::Elf_types<size>::Elf_WXword sh_flags = shdr.get_sh_flags();
typename elfcpp::Elf_types<size>::Elf_WXword sh_addralign =
shdr.get_sh_addralign();
// Make the output section.
Stringpool::Key name_key;
name = this->namepool_.add(name, true, &name_key);
Output_section* os = this->get_output_section(name, name_key, sh_type,
sh_flags, ORDER_INVALID, false);
os->set_fixed_layout(sh_addr, sh_offset, sh_size, sh_addralign);
if (sh_type != elfcpp::SHT_NOBITS)
this->free_list_.remove(sh_offset, sh_offset + sh_size);
return os;
}
// Return the index by which an input section should be ordered. This
// is used to sort some .text sections, for compatibility with GNU ld.
int
Layout::special_ordering_of_input_section(const char* name)
{
// The GNU linker has some special handling for some sections that
// wind up in the .text section. Sections that start with these
// prefixes must appear first, and must appear in the order listed
// here.
static const char* const text_section_sort[] =
{
".text.unlikely",
".text.exit",
".text.startup",
".text.hot"
};
for (size_t i = 0;
i < sizeof(text_section_sort) / sizeof(text_section_sort[0]);
i++)
if (is_prefix_of(text_section_sort[i], name))
return i;
return -1;
}
// 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_file<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;
elfcpp::Elf_Word sh_type = shdr.get_sh_type();
// In a relocatable link a grouped section must not be combined with
// any other sections.
Output_section* os;
if (parameters->options().relocatable()
&& (shdr.get_sh_flags() & elfcpp::SHF_GROUP) != 0)
{
// Some flags in the input section should not be automatically
// copied to the output section.
elfcpp::Elf_Xword flags = (shdr.get_sh_flags()
& ~ elfcpp::SHF_COMPRESSED);
name = this->namepool_.add(name, true, NULL);
os = this->make_output_section(name, sh_type, flags,
ORDER_INVALID, false);
}
else
{
// Plugins can choose to place one or more subsets of sections in
// unique segments and this is done by mapping these section subsets
// to unique output sections. Check if this section needs to be
// remapped to a unique output section.
Section_segment_map::iterator it
= this->section_segment_map_.find(Const_section_id(object, shndx));
if (it == this->section_segment_map_.end())
{
os = this->choose_output_section(object, name, sh_type,
shdr.get_sh_flags(), true,
ORDER_INVALID, false);
}
else
{
// We know the name of the output section, directly call
// get_output_section here by-passing choose_output_section.
elfcpp::Elf_Xword flags
= this->get_output_section_flags(shdr.get_sh_flags());
const char* os_name = it->second->name;
Stringpool::Key name_key;
os_name = this->namepool_.add(os_name, true, &name_key);
os = this->get_output_section(os_name, name_key, sh_type, flags,
ORDER_INVALID, false);
if (!os->is_unique_segment())
{
os->set_is_unique_segment();
os->set_extra_segment_flags(it->second->flags);
os->set_segment_alignment(it->second->align);
}
}
if (os == NULL)
return NULL;
}
// By default the GNU linker sorts input sections whose names match
// .ctors.*, .dtors.*, .init_array.*, or .fini_array.*. The
// sections are sorted by name. This is used to implement
// constructor priority ordering. We are compatible. When we put
// .ctor sections in .init_array and .dtor sections in .fini_array,
// we must also sort plain .ctor and .dtor sections.
if (!this->script_options_->saw_sections_clause()
&& !parameters->options().relocatable()
&& (is_prefix_of(".ctors.", name)
|| is_prefix_of(".dtors.", name)
|| is_prefix_of(".init_array.", name)
|| is_prefix_of(".fini_array.", name)
|| (parameters->options().ctors_in_init_array()
&& (strcmp(name, ".ctors") == 0
|| strcmp(name, ".dtors") == 0))))
os->set_must_sort_attached_input_sections();
// By default the GNU linker sorts some special text sections ahead
// of others. We are compatible.
if (parameters->options().text_reorder()
&& !this->script_options_->saw_sections_clause()
&& !this->is_section_ordering_specified()
&& !parameters->options().relocatable()
&& Layout::special_ordering_of_input_section(name) >= 0)
os->set_must_sort_attached_input_sections();
// If this is a .ctors or .ctors.* section being mapped to a
// .init_array section, or a .dtors or .dtors.* section being mapped
// to a .fini_array section, we will need to reverse the words if
// there is more than one. Record this section for later. See
// ctors_sections_in_init_array above.
if (!this->script_options_->saw_sections_clause()
&& !parameters->options().relocatable()
&& shdr.get_sh_size() > size / 8
&& (((strcmp(name, ".ctors") == 0
|| is_prefix_of(".ctors.", name))
&& strcmp(os->name(), ".init_array") == 0)
|| ((strcmp(name, ".dtors") == 0
|| is_prefix_of(".dtors.", name))
&& strcmp(os->name(), ".fini_array") == 0)))
ctors_sections_in_init_array.insert(Section_id(object, shndx));
// FIXME: Handle SHF_LINK_ORDER somewhere.
elfcpp::Elf_Xword orig_flags = os->flags();
*off = os->add_input_section(this, object, shndx, name, shdr, reloc_shndx,
this->script_options_->saw_sections_clause());
// If the flags changed, we may have to change the order.
if ((orig_flags & elfcpp::SHF_ALLOC) != 0)
{
orig_flags &= (elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR);
elfcpp::Elf_Xword new_flags =
os->flags() & (elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR);
if (orig_flags != new_flags)
os->set_order(this->default_section_order(os, false));
}
this->have_added_input_section_ = true;
return os;
}
// Maps section SECN to SEGMENT s.
void
Layout::insert_section_segment_map(Const_section_id secn,
Unique_segment_info *s)
{
gold_assert(this->unique_segment_for_sections_specified_);
this->section_segment_map_[secn] = s;
}
// Handle a relocation section when doing a relocatable link.
template<int size, bool big_endian>
Output_section*
Layout::layout_reloc(Sized_relobj_file<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();
// In a relocatable link relocs for a grouped section must not be
// combined with other reloc sections.
Output_section* os;
if (!parameters->options().relocatable()
|| (data_section->flags() & elfcpp::SHF_GROUP) == 0)
os = this->choose_output_section(object, name.c_str(), sh_type,
shdr.get_sh_flags(), false,
ORDER_INVALID, false);
else
{
const char* n = this->namepool_.add(name.c_str(), true, NULL);
os = this->make_output_section(n, sh_type, shdr.get_sh_flags(),
ORDER_INVALID, 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_file<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(),
ORDER_INVALID, 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_file<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
|| shdr.get_sh_type() == elfcpp::SHT_X86_64_UNWIND);
gold_assert((shdr.get_sh_flags() & elfcpp::SHF_ALLOC) != 0);
Output_section* os = this->make_eh_frame_section(object);
if (os == NULL)
return NULL;
gold_assert(this->eh_frame_section_ == os);
elfcpp::Elf_Xword orig_flags = os->flags();
Eh_frame::Eh_frame_section_disposition disp =
Eh_frame::EH_UNRECOGNIZED_SECTION;
if (!parameters->incremental())
{
disp = this->eh_frame_data_->add_ehframe_input_section(object,
symbols,
symbols_size,
symbol_names,
symbol_names_size,
shndx,
reloc_shndx,
reloc_type);
}
if (disp == Eh_frame::EH_OPTIMIZABLE_SECTION)
{
os->update_flags_for_input_section(shdr.get_sh_flags());
// A writable .eh_frame section is a RELRO section.
if ((orig_flags & (elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR))
!= (os->flags() & (elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR)))
{
os->set_is_relro();
os->set_order(ORDER_RELRO);
}
*off = -1;
return os;
}
if (disp == Eh_frame::EH_END_MARKER_SECTION && !this->added_eh_frame_data_)
{
// We found the end marker section, 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 crtbeginT.o winds up at the start of
// the output section.
os->add_output_section_data(this->eh_frame_data_);
this->added_eh_frame_data_ = true;
}
// 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(this, object, shndx, ".eh_frame", shdr,
reloc_shndx, saw_sections_clause);
this->have_added_input_section_ = true;
if ((orig_flags & (elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR))
!= (os->flags() & (elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR)))
os->set_order(this->default_section_order(os, false));
return os;
}
void
Layout::finalize_eh_frame_section()
{
// If we never found an end marker section, we need to add the
// optimized eh sections to the output section now.
if (!parameters->incremental()
&& this->eh_frame_section_ != NULL
&& !this->added_eh_frame_data_)
{
this->eh_frame_section_->add_output_section_data(this->eh_frame_data_);
this->added_eh_frame_data_ = true;
}
}
// Create and return the magic .eh_frame section. Create
// .eh_frame_hdr also if appropriate. OBJECT is the object with the
// input .eh_frame section; it may be NULL.
Output_section*
Layout::make_eh_frame_section(const Relobj* object)
{
// FIXME: On x86_64, this could use SHT_X86_64_UNWIND rather than
// SHT_PROGBITS.
Output_section* os = this->choose_output_section(object, ".eh_frame",
elfcpp::SHT_PROGBITS,
elfcpp::SHF_ALLOC, false,
ORDER_EHFRAME, false);
if (os == NULL)
return NULL;
if (this->eh_frame_section_ == NULL)
{
this->eh_frame_section_ = os;
this->eh_frame_data_ = new Eh_frame();
// For incremental linking, we do not optimize .eh_frame sections
// or create a .eh_frame_hdr section.
if (parameters->options().eh_frame_hdr() && !parameters->incremental())
{
Output_section* hdr_os =
this->choose_output_section(NULL, ".eh_frame_hdr",
elfcpp::SHT_PROGBITS,
elfcpp::SHF_ALLOC, false,
ORDER_EHFRAME, 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_to_nonload(hdr_os,
elfcpp::PF_R);
}
this->eh_frame_data_->set_eh_frame_hdr(hdr_posd);
}
}
}
return os;
}
// Add an exception frame for a PLT. This is called from target code.
void
Layout::add_eh_frame_for_plt(Output_data* plt, const unsigned char* cie_data,
size_t cie_length, const unsigned char* fde_data,
size_t fde_length)
{
if (parameters->incremental())
{
// FIXME: Maybe this could work some day....
return;
}
Output_section* os = this->make_eh_frame_section(NULL);
if (os == NULL)
return;
this->eh_frame_data_->add_ehframe_for_plt(plt, cie_data, cie_length,
fde_data, fde_length);
if (!this->added_eh_frame_data_)
{
os->add_output_section_data(this->eh_frame_data_);
this->added_eh_frame_data_ = true;
}
}
// Scan a .debug_info or .debug_types section, and add summary
// information to the .gdb_index section.
template<int size, bool big_endian>
void
Layout::add_to_gdb_index(bool is_type_unit,
Sized_relobj<size, big_endian>* object,
const unsigned char* symbols,
off_t symbols_size,
unsigned int shndx,
unsigned int reloc_shndx,
unsigned int reloc_type)
{
if (this->gdb_index_data_ == NULL)
{
Output_section* os = this->choose_output_section(NULL, ".gdb_index",
elfcpp::SHT_PROGBITS, 0,
false, ORDER_INVALID,
false);
if (os == NULL)
return;
this->gdb_index_data_ = new Gdb_index(os);
os->add_output_section_data(this->gdb_index_data_);
os->set_after_input_sections();
}
this->gdb_index_data_->scan_debug_info(is_type_unit, object, symbols,
symbols_size, shndx, reloc_shndx,
reloc_type);
}
// 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,
Output_section_order order, bool is_relro)
{
Output_section* os = this->choose_output_section(NULL, name, type, flags,
false, order, is_relro);
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;
}
// Make a new Output_section, and attach it to segments as
// appropriate. ORDER is the order in which this section should
// appear in the output segment. IS_RELRO is true if this is a relro
// (read-only after relocations) section.
Output_section*
Layout::make_output_section(const char* name, elfcpp::Elf_Word type,
elfcpp::Elf_Xword flags,
Output_section_order order, bool is_relro)
{
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
{
// Sometimes .init_array*, .preinit_array* and .fini_array* do
// not have correct section types. Force them here.
if (type == elfcpp::SHT_PROGBITS)
{
if (is_prefix_of(".init_array", name))
type = elfcpp::SHT_INIT_ARRAY;
else if (is_prefix_of(".preinit_array", name))
type = elfcpp::SHT_PREINIT_ARRAY;
else if (is_prefix_of(".fini_array", name))
type = elfcpp::SHT_FINI_ARRAY;
}
// FIXME: const_cast is ugly.
Target* target = const_cast<Target*>(&parameters->target());
os = target->make_output_section(name, type, flags);
}
// With -z relro, we have to recognize the special sections by name.
// There is no other way.
bool is_relro_local = false;
if (!this->script_options_->saw_sections_clause()
&& parameters->options().relro()
&& (flags & elfcpp::SHF_ALLOC) != 0
&& (flags & elfcpp::SHF_WRITE) != 0)
{
if (type == elfcpp::SHT_PROGBITS)
{
if ((flags & elfcpp::SHF_TLS) != 0)
is_relro = true;
else if (strcmp(name, ".data.rel.ro") == 0)
is_relro = true;
else if (strcmp(name, ".data.rel.ro.local") == 0)
{
is_relro = true;
is_relro_local = true;
}
else if (strcmp(name, ".ctors") == 0
|| strcmp(name, ".dtors") == 0
|| strcmp(name, ".jcr") == 0)
is_relro = true;
}
else if (type == elfcpp::SHT_INIT_ARRAY
|| type == elfcpp::SHT_FINI_ARRAY
|| type == elfcpp::SHT_PREINIT_ARRAY)
is_relro = true;
}
if (is_relro)
os->set_is_relro();
if (order == ORDER_INVALID && (flags & elfcpp::SHF_ALLOC) != 0)
order = this->default_section_order(os, is_relro_local);
os->set_order(order);
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()
&& !parameters->options().relocatable()
&& (strcmp(name, ".init_array") == 0
|| strcmp(name, ".fini_array") == 0
|| (!parameters->options().ctors_in_init_array()
&& (strcmp(name, ".ctors") == 0
|| strcmp(name, ".dtors") == 0))))
os->set_may_sort_attached_input_sections();
// The GNU linker by default sorts .text.{unlikely,exit,startup,hot}
// sections before other .text sections. We are compatible. We
// need to know that this might happen before we attach any input
// sections.
if (parameters->options().text_reorder()
&& !this->script_options_->saw_sections_clause()
&& !this->is_section_ordering_specified()
&& !parameters->options().relocatable()
&& strcmp(name, ".text") == 0)
os->set_may_sort_attached_input_sections();
// GNU linker sorts section by name with --sort-section=name.
if (strcmp(parameters->options().sort_section(), "name") == 0)
os->set_must_sort_attached_input_sections();
// 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;
// During a full incremental link, we add patch space to most
// PROGBITS and NOBITS sections. Flag those that may be
// arbitrarily padded.
if ((type == elfcpp::SHT_PROGBITS || type == elfcpp::SHT_NOBITS)
&& order != ORDER_INTERP
&& order != ORDER_INIT
&& order != ORDER_PLT
&& order != ORDER_FINI
&& order != ORDER_RELRO_LAST
&& order != ORDER_NON_RELRO_FIRST
&& strcmp(name, ".eh_frame") != 0
&& strcmp(name, ".ctors") != 0
&& strcmp(name, ".dtors") != 0
&& strcmp(name, ".jcr") != 0)
{
os->set_is_patch_space_allowed();
// Certain sections require "holes" to be filled with
// specific fill patterns. These fill patterns may have
// a minimum size, so we must prevent allocations from the
// free list that leave a hole smaller than the minimum.
if (strcmp(name, ".debug_info") == 0)
os->set_free_space_fill(new Output_fill_debug_info(false));
else if (strcmp(name, ".debug_types") == 0)
os->set_free_space_fill(new Output_fill_debug_info(true));
else if (strcmp(name, ".debug_line") == 0)
os->set_free_space_fill(new Output_fill_debug_line());
}
// 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(&parameters->target(), os);
return os;
}
// Return the default order in which a section should be placed in an
// output segment. This function captures a lot of the ideas in
// ld/scripttempl/elf.sc in the GNU linker. Note that the order of a
// linker created section is normally set when the section is created;
// this function is used for input sections.
Output_section_order
Layout::default_section_order(Output_section* os, bool is_relro_local)
{
gold_assert((os->flags() & elfcpp::SHF_ALLOC) != 0);
bool is_write = (os->flags() & elfcpp::SHF_WRITE) != 0;
bool is_execinstr = (os->flags() & elfcpp::SHF_EXECINSTR) != 0;
bool is_bss = false;
switch (os->type())
{
default:
case elfcpp::SHT_PROGBITS:
break;
case elfcpp::SHT_NOBITS:
is_bss = true;
break;
case elfcpp::SHT_RELA:
case elfcpp::SHT_REL:
if (!is_write)
return ORDER_DYNAMIC_RELOCS;
break;
case elfcpp::SHT_HASH:
case elfcpp::SHT_DYNAMIC:
case elfcpp::SHT_SHLIB:
case elfcpp::SHT_DYNSYM:
case elfcpp::SHT_GNU_HASH:
case elfcpp::SHT_GNU_verdef:
case elfcpp::SHT_GNU_verneed:
case elfcpp::SHT_GNU_versym:
if (!is_write)
return ORDER_DYNAMIC_LINKER;
break;
case elfcpp::SHT_NOTE:
return is_write ? ORDER_RW_NOTE : ORDER_RO_NOTE;
}
if ((os->flags() & elfcpp::SHF_TLS) != 0)
return is_bss ? ORDER_TLS_BSS : ORDER_TLS_DATA;
if (!is_bss && !is_write)
{
if (is_execinstr)
{
if (strcmp(os->name(), ".init") == 0)
return ORDER_INIT;
else if (strcmp(os->name(), ".fini") == 0)
return ORDER_FINI;
}
return is_execinstr ? ORDER_TEXT : ORDER_READONLY;
}
if (os->is_relro())
return is_relro_local ? ORDER_RELRO_LOCAL : ORDER_RELRO;
if (os->is_small_section())
return is_bss ? ORDER_SMALL_BSS : ORDER_SMALL_DATA;
if (os->is_large_section())
return is_bss ? ORDER_LARGE_BSS : ORDER_LARGE_DATA;
return is_bss ? ORDER_BSS : ORDER_DATA;
}
// Attach output sections to segments. This is called after we have
// seen all the input sections.
void
Layout::attach_sections_to_segments(const Target* target)
{
for (Section_list::iterator p = this->section_list_.begin();
p != this->section_list_.end();
++p)
this->attach_section_to_segment(target, *p);
this->sections_are_attached_ = true;
}
// Attach an output section to a segment.
void
Layout::attach_section_to_segment(const Target* target, Output_section* os)
{
if ((os->flags() & elfcpp::SHF_ALLOC) == 0)
this->unattached_section_list_.push_back(os);
else
this->attach_allocated_section_to_segment(target, os);
}
// Attach an allocated output section to a segment.
void
Layout::attach_allocated_section_to_segment(const Target* target,
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);
// If this output section's segment has extra flags that need to be set,
// coming from a linker plugin, do that.
seg_flags |= os->extra_segment_flags();
// Check for --section-start.
uint64_t addr;
bool is_address_set = parameters->options().section_start(os->name(), &addr);
// In general the only thing we really care about for PT_LOAD
// segments is whether or not they are writable or executable,
// 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;
if (!os->is_unique_segment())
{
for (p = this->segment_list_.begin();
p != this->segment_list_.end();
++p)
{
if ((*p)->type() != elfcpp::PT_LOAD)
continue;
if ((*p)->is_unique_segment())
continue;
if (!parameters->options().omagic()
&& ((*p)->flags() & elfcpp::PF_W) != (seg_flags & elfcpp::PF_W))
continue;
if ((target->isolate_execinstr() || parameters->options().rosegment())
&& ((*p)->flags() & elfcpp::PF_X) != (seg_flags & elfcpp::PF_X))
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;
if (is_address_set)
{
if ((*p)->are_addresses_set())
continue;
(*p)->add_initial_output_data(os);
(*p)->update_flags_for_output_section(seg_flags);
(*p)->set_addresses(addr, addr);
break;
}
(*p)->add_output_section_to_load(this, os, seg_flags);
break;
}
}
if (p == this->segment_list_.end()
|| os->is_unique_segment())
{
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_to_load(this, os, seg_flags);
if (is_address_set)
oseg->set_addresses(addr, addr);
// Check if segment should be marked unique. For segments marked
// unique by linker plugins, set the new alignment if specified.
if (os->is_unique_segment())
{
oseg->set_is_unique_segment();
if (os->segment_alignment() != 0)
oseg->set_minimum_p_align(os->segment_alignment());
}
}
// 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_to_nonload(os, seg_flags);
break;
}
}
if (p == this->segment_list_.end())
{
Output_segment* oseg = this->make_output_segment(elfcpp::PT_NOTE,
seg_flags);
oseg->add_output_section_to_nonload(os, seg_flags);
}
}
// 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_to_nonload(os, seg_flags);
}
// 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_to_nonload(os, seg_flags);
}
// If we see a section named .interp, put it into a PT_INTERP
// segment. This seems broken to me, but this is what GNU ld does,
// and glibc expects it.
if (strcmp(os->name(), ".interp") == 0
&& !this->script_options_->saw_phdrs_clause())
{
if (this->interp_segment_ == NULL)
this->make_output_segment(elfcpp::PT_INTERP, seg_flags);
else
gold_warning(_("multiple '.interp' sections in input files "
"may cause confusing PT_INTERP segment"));
this->interp_segment_->add_output_section_to_nonload(os, seg_flags);
}
}
// Make an output section for a script.
Output_section*
Layout::make_output_section_for_script(
const char* name,
Script_sections::Section_type section_type)
{
name = this->namepool_.add(name, false, NULL);
elfcpp::Elf_Xword sh_flags = elfcpp::SHF_ALLOC;
if (section_type == Script_sections::ST_NOLOAD)
sh_flags = 0;
Output_section* os = this->make_output_section(name, elfcpp::SHT_PROGBITS,
sh_flags, ORDER_INVALID,
false);
os->set_found_in_sections_clause();
if (section_type == Script_sections::ST_NOLOAD)
os->set_is_noload();
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,
const Object* obj)
{
if (!seen_gnu_stack)
{
this->input_without_gnu_stack_note_ = true;
if (parameters->options().warn_execstack()
&& parameters->target().is_default_stack_executable())
gold_warning(_("%s: missing .note.GNU-stack section"
" implies executable stack"),
obj->name().c_str());
}
else
{
this->input_with_gnu_stack_note_ = true;
if ((gnu_stack_flags & elfcpp::SHF_EXECINSTR) != 0)
{
this->input_requires_executable_stack_ = true;
if (parameters->options().warn_execstack())
gold_warning(_("%s: requires executable stack"),
obj->name().c_str());
}
}
}
// Create automatic note sections.
void
Layout::create_notes()
{
this->create_gold_note();
this->create_stack_segment();
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, ORDER_RELRO,
true);
// A linker script may discard .dynamic, so check for NULL.
if (this->dynamic_section_ != NULL)
{
this->dynamic_symbol_ =
symtab->define_in_output_data("_DYNAMIC", NULL,
Symbol_table::PREDEFINED,
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 (is_cident(name))
{
const std::string name_string(name);
const std::string start_name(cident_section_start_prefix
+ name_string);
const std::string stop_name(cident_section_stop_prefix
+ name_string);
symtab->define_in_output_data(start_name.c_str(),
NULL, // version
Symbol_table::PREDEFINED,
*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
Symbol_table::PREDEFINED,
*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(const Target* target)
{
Output_segment* best = NULL;
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)
&& (!target->isolate_execinstr()
|| ((*p)->flags() & elfcpp::PF_X) == 0))
{
if (best == NULL || this->segment_precedes(*p, best))
best = *p;
}
}
if (best != NULL)
return best;
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)->restore_states();
// If an input section changes size because of relaxation,
// we need to adjust the section offsets of all input sections.
// after such a section.
if ((*p)->section_offsets_need_adjustment())
(*p)->adjust_section_offsets();
(*p)->reset_address_and_file_offset();
}
// 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();
// Special-case fill output objects are recreated each time through
// the relaxation loop.
this->reset_relax_output();
}
void
Layout::reset_relax_output()
{
for (Data_list::const_iterator p = this->relax_output_list_.begin();
p != this->relax_output_list_.end();
++p)
delete *p;
this->relax_output_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_,
this->relax_output_list_);
// Also enable recording of output section data from scripts.
this->record_output_section_data_from_script_ = true;
}
// If the user set the address of the text segment, that may not be
// compatible with putting the segment headers and file headers into
// that segment. For isolate_execinstr() targets, it's the rodata
// segment rather than text where we might put the headers.
static inline bool
load_seg_unusable_for_headers(const Target* target)
{
const General_options& options = parameters->options();
if (target->isolate_execinstr())
return (options.user_set_Trodata_segment()
&& options.Trodata_segment() % target->abi_pagesize() != 0);
else
return (options.user_set_Ttext()
&& options.Ttext() % target->abi_pagesize() != 0);
}
// 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(target);
if (parameters->options().oformat_enum()
!= General_options::OBJECT_FORMAT_ELF)
load_seg = NULL;
if (load_seg_unusable_for_headers(target))
{
load_seg = NULL;
phdr_seg = NULL;
}
gold_assert(phdr_seg == NULL
|| load_seg != NULL
|| this->script_options_->saw_sections_clause());
// If the address of the load segment we found has been set by
// --section-start rather than by a script, then adjust the VMA and
// LMA downward if possible to include the file and section headers.
uint64_t header_gap = 0;
if (load_seg != NULL
&& load_seg->are_addresses_set()
&& !this->script_options_->saw_sections_clause()
&& !parameters->options().relocatable())
{
file_header->finalize_data_size();
segment_headers->finalize_data_size();
size_t sizeof_headers = (file_header->data_size()
+ segment_headers->data_size());
const uint64_t abi_pagesize = target->abi_pagesize();
uint64_t hdr_paddr = load_seg->paddr() - sizeof_headers;
hdr_paddr &= ~(abi_pagesize - 1);
uint64_t subtract = load_seg->paddr() - hdr_paddr;
if (load_seg->paddr() < subtract || load_seg->vaddr() < subtract)
load_seg = NULL;
else
{
load_seg->set_addresses(load_seg->vaddr() - subtract,
load_seg->paddr() - subtract);
header_gap = subtract - sizeof_headers;
}
}
// Lay out the segment headers.
if (!parameters->options().relocatable())
{
gold_assert(segment_headers != NULL);
if (header_gap != 0 && load_seg != NULL)
{
Output_data_zero_fill* z = new Output_data_zero_fill(header_gap, 1);
load_seg->add_initial_output_data(z);
}
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;
}
// Search the list of patterns and find the postion of the given section
// name in the output section. If the section name matches a glob
// pattern and a non-glob name, then the non-glob position takes
// precedence. Return 0 if no match is found.
unsigned int
Layout::find_section_order_index(const std::string& section_name)
{
Unordered_map<std::string, unsigned int>::iterator map_it;
map_it = this->input_section_position_.find(section_name);
if (map_it != this->input_section_position_.end())
return map_it->second;
// Absolute match failed. Linear search the glob patterns.
std::vector<std::string>::iterator it;
for (it = this->input_section_glob_.begin();
it != this->input_section_glob_.end();
++it)
{
if (fnmatch((*it).c_str(), section_name.c_str(), FNM_NOESCAPE) == 0)
{
map_it = this->input_section_position_.find(*it);
gold_assert(map_it != this->input_section_position_.end());
return map_it->second;
}
}
return 0;
}
// Read the sequence of input sections from the file specified with
// option --section-ordering-file.
void
Layout::read_layout_from_file()
{
const char* filename = parameters->options().section_ordering_file();
std::ifstream in;
std::string line;
in.open(filename);
if (!in)
gold_fatal(_("unable to open --section-ordering-file file %s: %s"),
filename, strerror(errno));
std::getline(in, line); // this chops off the trailing \n, if any
unsigned int position = 1;
this->set_section_ordering_specified();
while (in)
{
if (!line.empty() && line[line.length() - 1] == '\r') // Windows
line.resize(line.length() - 1);
// Ignore comments, beginning with '#'
if (line[0] == '#')
{
std::getline(in, line);
continue;
}
this->input_section_position_[line] = position;
// Store all glob patterns in a vector.
if (is_wildcard_string(line.c_str()))
this->input_section_glob_.push_back(line);
position++;
std::getline(in, line);
}
}
// 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, input_objects, symtab);
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