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// x86_64.cc -- x86_64 target support 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 <cstring>
#include "elfcpp.h"
#include "dwarf.h"
#include "parameters.h"
#include "reloc.h"
#include "x86_64.h"
#include "object.h"
#include "symtab.h"
#include "layout.h"
#include "output.h"
#include "copy-relocs.h"
#include "target.h"
#include "target-reloc.h"
#include "target-select.h"
#include "tls.h"
#include "freebsd.h"
#include "nacl.h"
#include "gc.h"
#include "icf.h"
namespace
{
using namespace gold;
// A class to handle the .got.plt section.
class Output_data_got_plt_x86_64 : public Output_section_data_build
{
public:
Output_data_got_plt_x86_64(Layout* layout)
: Output_section_data_build(8),
layout_(layout)
{ }
Output_data_got_plt_x86_64(Layout* layout, off_t data_size)
: Output_section_data_build(data_size, 8),
layout_(layout)
{ }
protected:
// Write out the PLT data.
void
do_write(Output_file*);
// Write to a map file.
void
do_print_to_mapfile(Mapfile* mapfile) const
{ mapfile->print_output_data(this, "** GOT PLT"); }
private:
// A pointer to the Layout class, so that we can find the .dynamic
// section when we write out the GOT PLT section.
Layout* layout_;
};
// A class to handle the PLT data.
// This is an abstract base class that handles most of the linker details
// but does not know the actual contents of PLT entries. The derived
// classes below fill in those details.
template<int size>
class Output_data_plt_x86_64 : public Output_section_data
{
public:
typedef Output_data_reloc<elfcpp::SHT_RELA, true, size, false> Reloc_section;
Output_data_plt_x86_64(Layout* layout, uint64_t addralign,
Output_data_got<64, false>* got,
Output_data_got_plt_x86_64* got_plt,
Output_data_space* got_irelative)
: Output_section_data(addralign), tlsdesc_rel_(NULL),
irelative_rel_(NULL), got_(got), got_plt_(got_plt),
got_irelative_(got_irelative), count_(0), irelative_count_(0),
tlsdesc_got_offset_(-1U), free_list_()
{ this->init(layout); }
Output_data_plt_x86_64(Layout* layout, uint64_t plt_entry_size,
Output_data_got<64, false>* got,
Output_data_got_plt_x86_64* got_plt,
Output_data_space* got_irelative,
unsigned int plt_count)
: Output_section_data((plt_count + 1) * plt_entry_size,
plt_entry_size, false),
tlsdesc_rel_(NULL), irelative_rel_(NULL), got_(got),
got_plt_(got_plt), got_irelative_(got_irelative), count_(plt_count),
irelative_count_(0), tlsdesc_got_offset_(-1U), free_list_()
{
this->init(layout);
// Initialize the free list and reserve the first entry.
this->free_list_.init((plt_count + 1) * plt_entry_size, false);
this->free_list_.remove(0, plt_entry_size);
}
// Initialize the PLT section.
void
init(Layout* layout);
// Add an entry to the PLT.
void
add_entry(Symbol_table*, Layout*, Symbol* gsym);
// Add an entry to the PLT for a local STT_GNU_IFUNC symbol.
unsigned int
add_local_ifunc_entry(Symbol_table* symtab, Layout*,
Sized_relobj_file<size, false>* relobj,
unsigned int local_sym_index);
// Add the relocation for a PLT entry.
void
add_relocation(Symbol_table*, Layout*, Symbol* gsym,
unsigned int got_offset);
// Add the reserved TLSDESC_PLT entry to the PLT.
void
reserve_tlsdesc_entry(unsigned int got_offset)
{ this->tlsdesc_got_offset_ = got_offset; }
// Return true if a TLSDESC_PLT entry has been reserved.
bool
has_tlsdesc_entry() const
{ return this->tlsdesc_got_offset_ != -1U; }
// Return the GOT offset for the reserved TLSDESC_PLT entry.
unsigned int
get_tlsdesc_got_offset() const
{ return this->tlsdesc_got_offset_; }
// Return the offset of the reserved TLSDESC_PLT entry.
unsigned int
get_tlsdesc_plt_offset() const
{
return ((this->count_ + this->irelative_count_ + 1)
* this->get_plt_entry_size());
}
// Return the .rela.plt section data.
Reloc_section*
rela_plt()
{ return this->rel_; }
// Return where the TLSDESC relocations should go.
Reloc_section*
rela_tlsdesc(Layout*);
// Return where the IRELATIVE relocations should go in the PLT
// relocations.
Reloc_section*
rela_irelative(Symbol_table*, Layout*);
// Return whether we created a section for IRELATIVE relocations.
bool
has_irelative_section() const
{ return this->irelative_rel_ != NULL; }
// Return the number of PLT entries.
unsigned int
entry_count() const
{ return this->count_ + this->irelative_count_; }
// Return the offset of the first non-reserved PLT entry.
unsigned int
first_plt_entry_offset()
{ return this->get_plt_entry_size(); }
// Return the size of a PLT entry.
unsigned int
get_plt_entry_size() const
{ return this->do_get_plt_entry_size(); }
// Reserve a slot in the PLT for an existing symbol in an incremental update.
void
reserve_slot(unsigned int plt_index)
{
this->free_list_.remove((plt_index + 1) * this->get_plt_entry_size(),
(plt_index + 2) * this->get_plt_entry_size());
}
// Return the PLT address to use for a global symbol.
uint64_t
address_for_global(const Symbol*);
// Return the PLT address to use for a local symbol.
uint64_t
address_for_local(const Relobj*, unsigned int symndx);
// Add .eh_frame information for the PLT.
void
add_eh_frame(Layout* layout)
{ this->do_add_eh_frame(layout); }
protected:
// Fill in the first PLT entry.
void
fill_first_plt_entry(unsigned char* pov,
typename elfcpp::Elf_types<size>::Elf_Addr got_address,
typename elfcpp::Elf_types<size>::Elf_Addr plt_address)
{ this->do_fill_first_plt_entry(pov, got_address, plt_address); }
// Fill in a normal PLT entry. Returns the offset into the entry that
// should be the initial GOT slot value.
unsigned int
fill_plt_entry(unsigned char* pov,
typename elfcpp::Elf_types<size>::Elf_Addr got_address,
typename elfcpp::Elf_types<size>::Elf_Addr plt_address,
unsigned int got_offset,
unsigned int plt_offset,
unsigned int plt_index)
{
return this->do_fill_plt_entry(pov, got_address, plt_address,
got_offset, plt_offset, plt_index);
}
// Fill in the reserved TLSDESC PLT entry.
void
fill_tlsdesc_entry(unsigned char* pov,
typename elfcpp::Elf_types<size>::Elf_Addr got_address,
typename elfcpp::Elf_types<size>::Elf_Addr plt_address,
typename elfcpp::Elf_types<size>::Elf_Addr got_base,
unsigned int tlsdesc_got_offset,
unsigned int plt_offset)
{
this->do_fill_tlsdesc_entry(pov, got_address, plt_address, got_base,
tlsdesc_got_offset, plt_offset);
}
virtual unsigned int
do_get_plt_entry_size() const = 0;
virtual void
do_fill_first_plt_entry(unsigned char* pov,
typename elfcpp::Elf_types<size>::Elf_Addr got_addr,
typename elfcpp::Elf_types<size>::Elf_Addr plt_addr)
= 0;
virtual unsigned int
do_fill_plt_entry(unsigned char* pov,
typename elfcpp::Elf_types<size>::Elf_Addr got_address,
typename elfcpp::Elf_types<size>::Elf_Addr plt_address,
unsigned int got_offset,
unsigned int plt_offset,
unsigned int plt_index) = 0;
virtual void
do_fill_tlsdesc_entry(unsigned char* pov,
typename elfcpp::Elf_types<size>::Elf_Addr got_address,
typename elfcpp::Elf_types<size>::Elf_Addr plt_address,
typename elfcpp::Elf_types<size>::Elf_Addr got_base,
unsigned int tlsdesc_got_offset,
unsigned int plt_offset) = 0;
virtual void
do_add_eh_frame(Layout* layout) = 0;
void
do_adjust_output_section(Output_section* os);
// Write to a map file.
void
do_print_to_mapfile(Mapfile* mapfile) const
{ mapfile->print_output_data(this, _("** PLT")); }
// The CIE of the .eh_frame unwind information for the PLT.
static const int plt_eh_frame_cie_size = 16;
static const unsigned char plt_eh_frame_cie[plt_eh_frame_cie_size];
private:
// Set the final size.
void
set_final_data_size();
// Write out the PLT data.
void
do_write(Output_file*);
// The reloc section.
Reloc_section* rel_;
// The TLSDESC relocs, if necessary. These must follow the regular
// PLT relocs.
Reloc_section* tlsdesc_rel_;
// The IRELATIVE relocs, if necessary. These must follow the
// regular PLT relocations and the TLSDESC relocations.
Reloc_section* irelative_rel_;
// The .got section.
Output_data_got<64, false>* got_;
// The .got.plt section.
Output_data_got_plt_x86_64* got_plt_;
// The part of the .got.plt section used for IRELATIVE relocs.
Output_data_space* got_irelative_;
// The number of PLT entries.
unsigned int count_;
// Number of PLT entries with R_X86_64_IRELATIVE relocs. These
// follow the regular PLT entries.
unsigned int irelative_count_;
// Offset of the reserved TLSDESC_GOT entry when needed.
unsigned int tlsdesc_got_offset_;
// List of available regions within the section, for incremental
// update links.
Free_list free_list_;
};
template<int size>
class Output_data_plt_x86_64_standard : public Output_data_plt_x86_64<size>
{
public:
Output_data_plt_x86_64_standard(Layout* layout,
Output_data_got<64, false>* got,
Output_data_got_plt_x86_64* got_plt,
Output_data_space* got_irelative)
: Output_data_plt_x86_64<size>(layout, plt_entry_size,
got, got_plt, got_irelative)
{ }
Output_data_plt_x86_64_standard(Layout* layout,
Output_data_got<64, false>* got,
Output_data_got_plt_x86_64* got_plt,
Output_data_space* got_irelative,
unsigned int plt_count)
: Output_data_plt_x86_64<size>(layout, plt_entry_size,
got, got_plt, got_irelative,
plt_count)
{ }
protected:
virtual unsigned int
do_get_plt_entry_size() const
{ return plt_entry_size; }
virtual void
do_add_eh_frame(Layout* layout)
{
layout->add_eh_frame_for_plt(this,
this->plt_eh_frame_cie,
this->plt_eh_frame_cie_size,
plt_eh_frame_fde,
plt_eh_frame_fde_size);
}
virtual void
do_fill_first_plt_entry(unsigned char* pov,
typename elfcpp::Elf_types<size>::Elf_Addr got_addr,
typename elfcpp::Elf_types<size>::Elf_Addr plt_addr);
virtual unsigned int
do_fill_plt_entry(unsigned char* pov,
typename elfcpp::Elf_types<size>::Elf_Addr got_address,
typename elfcpp::Elf_types<size>::Elf_Addr plt_address,
unsigned int got_offset,
unsigned int plt_offset,
unsigned int plt_index);
virtual void
do_fill_tlsdesc_entry(unsigned char* pov,
typename elfcpp::Elf_types<size>::Elf_Addr got_address,
typename elfcpp::Elf_types<size>::Elf_Addr plt_address,
typename elfcpp::Elf_types<size>::Elf_Addr got_base,
unsigned int tlsdesc_got_offset,
unsigned int plt_offset);
private:
// The size of an entry in the PLT.
static const int plt_entry_size = 16;
// The first entry in the PLT.
// From the AMD64 ABI: "Unlike Intel386 ABI, this ABI uses the same
// procedure linkage table for both programs and shared objects."
static const unsigned char first_plt_entry[plt_entry_size];
// Other entries in the PLT for an executable.
static const unsigned char plt_entry[plt_entry_size];
// The reserved TLSDESC entry in the PLT for an executable.
static const unsigned char tlsdesc_plt_entry[plt_entry_size];
// The .eh_frame unwind information for the PLT.
static const int plt_eh_frame_fde_size = 32;
static const unsigned char plt_eh_frame_fde[plt_eh_frame_fde_size];
};
template<int size>
class Lazy_view
{
public:
Lazy_view(Sized_relobj_file<size, false>* object, unsigned int data_shndx)
: object_(object), data_shndx_(data_shndx), view_(NULL), view_size_(0)
{ }
inline unsigned char
operator[](size_t offset)
{
if (this->view_ == NULL)
this->view_ = this->object_->section_contents(this->data_shndx_,
&this->view_size_,
true);
if (offset >= this->view_size_)
return 0;
return this->view_[offset];
}
private:
Sized_relobj_file<size, false>* object_;
unsigned int data_shndx_;
const unsigned char* view_;
section_size_type view_size_;
};
// The x86_64 target class.
// See the ABI at
// http://www.x86-64.org/documentation/abi.pdf
// TLS info comes from
// http://people.redhat.com/drepper/tls.pdf
// http://www.lsd.ic.unicamp.br/~oliva/writeups/TLS/RFC-TLSDESC-x86.txt
template<int size>
class Target_x86_64 : public Sized_target<size, false>
{
public:
// In the x86_64 ABI (p 68), it says "The AMD64 ABI architectures
// uses only Elf64_Rela relocation entries with explicit addends."
typedef Output_data_reloc<elfcpp::SHT_RELA, true, size, false> Reloc_section;
Target_x86_64(const Target::Target_info* info = &x86_64_info)
: Sized_target<size, false>(info),
got_(NULL), plt_(NULL), got_plt_(NULL), got_irelative_(NULL),
got_tlsdesc_(NULL), global_offset_table_(NULL), rela_dyn_(NULL),
rela_irelative_(NULL), copy_relocs_(elfcpp::R_X86_64_COPY),
got_mod_index_offset_(-1U), tlsdesc_reloc_info_(),
tls_base_symbol_defined_(false)
{ }
// Hook for a new output section.
void
do_new_output_section(Output_section*) const;
// Scan the relocations to look for symbol adjustments.
void
gc_process_relocs(Symbol_table* symtab,
Layout* layout,
Sized_relobj_file<size, false>* object,
unsigned int data_shndx,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
Output_section* output_section,
bool needs_special_offset_handling,
size_t local_symbol_count,
const unsigned char* plocal_symbols);
// Scan the relocations to look for symbol adjustments.
void
scan_relocs(Symbol_table* symtab,
Layout* layout,
Sized_relobj_file<size, false>* object,
unsigned int data_shndx,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
Output_section* output_section,
bool needs_special_offset_handling,
size_t local_symbol_count,
const unsigned char* plocal_symbols);
// Finalize the sections.
void
do_finalize_sections(Layout*, const Input_objects*, Symbol_table*);
// Return the value to use for a dynamic which requires special
// treatment.
uint64_t
do_dynsym_value(const Symbol*) const;
// Relocate a section.
void
relocate_section(const Relocate_info<size, false>*,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
Output_section* output_section,
bool needs_special_offset_handling,
unsigned char* view,
typename elfcpp::Elf_types<size>::Elf_Addr view_address,
section_size_type view_size,
const Reloc_symbol_changes*);
// Scan the relocs during a relocatable link.
void
scan_relocatable_relocs(Symbol_table* symtab,
Layout* layout,
Sized_relobj_file<size, false>* object,
unsigned int data_shndx,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
Output_section* output_section,
bool needs_special_offset_handling,
size_t local_symbol_count,
const unsigned char* plocal_symbols,
Relocatable_relocs*);
// Scan the relocs for --emit-relocs.
void
emit_relocs_scan(Symbol_table* symtab,
Layout* layout,
Sized_relobj_file<size, false>* object,
unsigned int data_shndx,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
Output_section* output_section,
bool needs_special_offset_handling,
size_t local_symbol_count,
const unsigned char* plocal_syms,
Relocatable_relocs* rr);
// Emit relocations for a section.
void
relocate_relocs(
const Relocate_info<size, false>*,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
Output_section* output_section,
typename elfcpp::Elf_types<size>::Elf_Off offset_in_output_section,
unsigned char* view,
typename elfcpp::Elf_types<size>::Elf_Addr view_address,
section_size_type view_size,
unsigned char* reloc_view,
section_size_type reloc_view_size);
// Return a string used to fill a code section with nops.
std::string
do_code_fill(section_size_type length) const;
// Return whether SYM is defined by the ABI.
bool
do_is_defined_by_abi(const Symbol* sym) const
{ return strcmp(sym->name(), "__tls_get_addr") == 0; }
// Return the symbol index to use for a target specific relocation.
// The only target specific relocation is R_X86_64_TLSDESC for a
// local symbol, which is an absolute reloc.
unsigned int
do_reloc_symbol_index(void*, unsigned int r_type) const
{
gold_assert(r_type == elfcpp::R_X86_64_TLSDESC);
return 0;
}
// Return the addend to use for a target specific relocation.
uint64_t
do_reloc_addend(void* arg, unsigned int r_type, uint64_t addend) const;
// Return the PLT section.
uint64_t
do_plt_address_for_global(const Symbol* gsym) const
{ return this->plt_section()->address_for_global(gsym); }
uint64_t
do_plt_address_for_local(const Relobj* relobj, unsigned int symndx) const
{ return this->plt_section()->address_for_local(relobj, symndx); }
// This function should be defined in targets that can use relocation
// types to determine (implemented in local_reloc_may_be_function_pointer
// and global_reloc_may_be_function_pointer)
// if a function's pointer is taken. ICF uses this in safe mode to only
// fold those functions whose pointer is defintely not taken. For x86_64
// pie binaries, safe ICF cannot be done by looking at relocation types.
bool
do_can_check_for_function_pointers() const
{ return !parameters->options().pie(); }
// Return the base for a DW_EH_PE_datarel encoding.
uint64_t
do_ehframe_datarel_base() const;
// Adjust -fsplit-stack code which calls non-split-stack code.
void
do_calls_non_split(Relobj* object, unsigned int shndx,
section_offset_type fnoffset, section_size_type fnsize,
const unsigned char* prelocs, size_t reloc_count,
unsigned char* view, section_size_type view_size,
std::string* from, std::string* to) const;
// Return the size of the GOT section.
section_size_type
got_size() const
{
gold_assert(this->got_ != NULL);
return this->got_->data_size();
}
// Return the number of entries in the GOT.
unsigned int
got_entry_count() const
{
if (this->got_ == NULL)
return 0;
return this->got_size() / 8;
}
// Return the number of entries in the PLT.
unsigned int
plt_entry_count() const;
// Return the offset of the first non-reserved PLT entry.
unsigned int
first_plt_entry_offset() const;
// Return the size of each PLT entry.
unsigned int
plt_entry_size() const;
// Return the size of each GOT entry.
unsigned int
got_entry_size() const
{ return 8; };
// Create the GOT section for an incremental update.
Output_data_got_base*
init_got_plt_for_update(Symbol_table* symtab,
Layout* layout,
unsigned int got_count,
unsigned int plt_count);
// Reserve a GOT entry for a local symbol, and regenerate any
// necessary dynamic relocations.
void
reserve_local_got_entry(unsigned int got_index,
Sized_relobj<size, false>* obj,
unsigned int r_sym,
unsigned int got_type);
// Reserve a GOT entry for a global symbol, and regenerate any
// necessary dynamic relocations.
void
reserve_global_got_entry(unsigned int got_index, Symbol* gsym,
unsigned int got_type);
// Register an existing PLT entry for a global symbol.
void
register_global_plt_entry(Symbol_table*, Layout*, unsigned int plt_index,
Symbol* gsym);
// Force a COPY relocation for a given symbol.
void
emit_copy_reloc(Symbol_table*, Symbol*, Output_section*, off_t);
// Apply an incremental relocation.
void
apply_relocation(const Relocate_info<size, false>* relinfo,
typename elfcpp::Elf_types<size>::Elf_Addr r_offset,
unsigned int r_type,
typename elfcpp::Elf_types<size>::Elf_Swxword r_addend,
const Symbol* gsym,
unsigned char* view,
typename elfcpp::Elf_types<size>::Elf_Addr address,
section_size_type view_size);
// Add a new reloc argument, returning the index in the vector.
size_t
add_tlsdesc_info(Sized_relobj_file<size, false>* object, unsigned int r_sym)
{
this->tlsdesc_reloc_info_.push_back(Tlsdesc_info(object, r_sym));
return this->tlsdesc_reloc_info_.size() - 1;
}
Output_data_plt_x86_64<size>*
make_data_plt(Layout* layout,
Output_data_got<64, false>* got,
Output_data_got_plt_x86_64* got_plt,
Output_data_space* got_irelative)
{
return this->do_make_data_plt(layout, got, got_plt, got_irelative);
}
Output_data_plt_x86_64<size>*
make_data_plt(Layout* layout,
Output_data_got<64, false>* got,
Output_data_got_plt_x86_64* got_plt,
Output_data_space* got_irelative,
unsigned int plt_count)
{
return this->do_make_data_plt(layout, got, got_plt, got_irelative,
plt_count);
}
virtual Output_data_plt_x86_64<size>*
do_make_data_plt(Layout* layout,
Output_data_got<64, false>* got,
Output_data_got_plt_x86_64* got_plt,
Output_data_space* got_irelative)
{
return new Output_data_plt_x86_64_standard<size>(layout, got, got_plt,
got_irelative);
}
virtual Output_data_plt_x86_64<size>*
do_make_data_plt(Layout* layout,
Output_data_got<64, false>* got,
Output_data_got_plt_x86_64* got_plt,
Output_data_space* got_irelative,
unsigned int plt_count)
{
return new Output_data_plt_x86_64_standard<size>(layout, got, got_plt,
got_irelative,
plt_count);
}
private:
// The class which scans relocations.
class Scan
{
public:
Scan()
: issued_non_pic_error_(false)
{ }
static inline int
get_reference_flags(unsigned int r_type);
inline void
local(Symbol_table* symtab, Layout* layout, Target_x86_64* target,
Sized_relobj_file<size, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rela<size, false>& reloc, unsigned int r_type,
const elfcpp::Sym<size, false>& lsym,
bool is_discarded);
inline void
global(Symbol_table* symtab, Layout* layout, Target_x86_64* target,
Sized_relobj_file<size, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rela<size, false>& reloc, unsigned int r_type,
Symbol* gsym);
inline bool
local_reloc_may_be_function_pointer(Symbol_table* symtab, Layout* layout,
Target_x86_64* target,
Sized_relobj_file<size, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rela<size, false>& reloc,
unsigned int r_type,
const elfcpp::Sym<size, false>& lsym);
inline bool
global_reloc_may_be_function_pointer(Symbol_table* symtab, Layout* layout,
Target_x86_64* target,
Sized_relobj_file<size, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rela<size, false>& reloc,
unsigned int r_type,
Symbol* gsym);
private:
static void
unsupported_reloc_local(Sized_relobj_file<size, false>*,
unsigned int r_type);
static void
unsupported_reloc_global(Sized_relobj_file<size, false>*,
unsigned int r_type, Symbol*);
void
check_non_pic(Relobj*, unsigned int r_type, Symbol*);
inline bool
possible_function_pointer_reloc(unsigned int r_type);
bool
reloc_needs_plt_for_ifunc(Sized_relobj_file<size, false>*,
unsigned int r_type);
// Whether we have issued an error about a non-PIC compilation.
bool issued_non_pic_error_;
};
// The class which implements relocation.
class Relocate
{
public:
Relocate()
: skip_call_tls_get_addr_(false)
{ }
~Relocate()
{
if (this->skip_call_tls_get_addr_)
{
// FIXME: This needs to specify the location somehow.
gold_error(_("missing expected TLS relocation"));
}
}
// Do a relocation. Return false if the caller should not issue
// any warnings about this relocation.
inline bool
relocate(const Relocate_info<size, false>*, unsigned int,
Target_x86_64*, Output_section*, size_t, const unsigned char*,
const Sized_symbol<size>*, const Symbol_value<size>*,
unsigned char*, typename elfcpp::Elf_types<size>::Elf_Addr,
section_size_type);
private:
// Do a TLS relocation.
inline void
relocate_tls(const Relocate_info<size, false>*, Target_x86_64*,
size_t relnum, const elfcpp::Rela<size, false>&,
unsigned int r_type, const Sized_symbol<size>*,
const Symbol_value<size>*,
unsigned char*, typename elfcpp::Elf_types<size>::Elf_Addr,
section_size_type);
// Do a TLS General-Dynamic to Initial-Exec transition.
inline void
tls_gd_to_ie(const Relocate_info<size, false>*, size_t relnum,
const elfcpp::Rela<size, false>&, unsigned int r_type,
typename elfcpp::Elf_types<size>::Elf_Addr value,
unsigned char* view,
typename elfcpp::Elf_types<size>::Elf_Addr,
section_size_type view_size);
// Do a TLS General-Dynamic to Local-Exec transition.
inline void
tls_gd_to_le(const Relocate_info<size, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rela<size, false>&, unsigned int r_type,
typename elfcpp::Elf_types<size>::Elf_Addr value,
unsigned char* view,
section_size_type view_size);
// Do a TLSDESC-style General-Dynamic to Initial-Exec transition.
inline void
tls_desc_gd_to_ie(const Relocate_info<size, false>*, size_t relnum,
const elfcpp::Rela<size, false>&, unsigned int r_type,
typename elfcpp::Elf_types<size>::Elf_Addr value,
unsigned char* view,
typename elfcpp::Elf_types<size>::Elf_Addr,
section_size_type view_size);
// Do a TLSDESC-style General-Dynamic to Local-Exec transition.
inline void
tls_desc_gd_to_le(const Relocate_info<size, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rela<size, false>&, unsigned int r_type,
typename elfcpp::Elf_types<size>::Elf_Addr value,
unsigned char* view,
section_size_type view_size);
// Do a TLS Local-Dynamic to Local-Exec transition.
inline void
tls_ld_to_le(const Relocate_info<size, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rela<size, false>&, unsigned int r_type,
typename elfcpp::Elf_types<size>::Elf_Addr value,
unsigned char* view,
section_size_type view_size);
// Do a TLS Initial-Exec to Local-Exec transition.
static inline void
tls_ie_to_le(const Relocate_info<size, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rela<size, false>&, unsigned int r_type,
typename elfcpp::Elf_types<size>::Elf_Addr value,
unsigned char* view,
section_size_type view_size);
// This is set if we should skip the next reloc, which should be a
// PLT32 reloc against ___tls_get_addr.
bool skip_call_tls_get_addr_;
};
// Check if relocation against this symbol is a candidate for
// conversion from
// mov foo@GOTPCREL(%rip), %reg
// to lea foo(%rip), %reg.
template<class View_type>
static inline bool
can_convert_mov_to_lea(const Symbol* gsym, unsigned int r_type,
size_t r_offset, View_type* view)
{
gold_assert(gsym != NULL);
// We cannot do the conversion unless it's one of these relocations.
if (r_type != elfcpp::R_X86_64_GOTPCREL
&& r_type != elfcpp::R_X86_64_GOTPCRELX
&& r_type != elfcpp::R_X86_64_REX_GOTPCRELX)
return false;
// We cannot convert references to IFUNC symbols, or to symbols that
// are not local to the current module.
if (gsym->type() == elfcpp::STT_GNU_IFUNC
|| gsym->is_undefined ()
|| gsym->is_from_dynobj()
|| gsym->is_preemptible())
return false;
// If we are building a shared object and the symbol is protected, we may
// need to go through the GOT.
if (parameters->options().shared()
&& gsym->visibility() == elfcpp::STV_PROTECTED)
return false;
// We cannot convert references to the _DYNAMIC symbol.
if (strcmp(gsym->name(), "_DYNAMIC") == 0)
return false;
// Check for a MOV opcode.
return (*view)[r_offset - 2] == 0x8b;
}
// Convert
// callq *foo@GOTPCRELX(%rip) to
// addr32 callq foo
// and jmpq *foo@GOTPCRELX(%rip) to
// jmpq foo
// nop
template<class View_type>
static inline bool
can_convert_callq_to_direct(const Symbol* gsym, unsigned int r_type,
size_t r_offset, View_type* view)
{
gold_assert(gsym != NULL);
// We cannot do the conversion unless it's a GOTPCRELX relocation.
if (r_type != elfcpp::R_X86_64_GOTPCRELX)
return false;
// We cannot convert references to IFUNC symbols, or to symbols that
// are not local to the current module.
if (gsym->type() == elfcpp::STT_GNU_IFUNC
|| gsym->is_undefined ()
|| gsym->is_from_dynobj()
|| gsym->is_preemptible())
return false;
// Check for a CALLQ or JMPQ opcode.
return ((*view)[r_offset - 2] == 0xff
&& ((*view)[r_offset - 1] == 0x15
|| (*view)[r_offset - 1] == 0x25));
}
// Adjust TLS relocation type based on the options and whether this
// is a local symbol.
static tls::Tls_optimization
optimize_tls_reloc(bool is_final, int r_type);
// Get the GOT section, creating it if necessary.
Output_data_got<64, false>*
got_section(Symbol_table*, Layout*);
// Get the GOT PLT section.
Output_data_got_plt_x86_64*
got_plt_section() const
{
gold_assert(this->got_plt_ != NULL);
return this->got_plt_;
}
// Get the GOT section for TLSDESC entries.
Output_data_got<64, false>*
got_tlsdesc_section() const
{
gold_assert(this->got_tlsdesc_ != NULL);
return this->got_tlsdesc_;
}
// Create the PLT section.
void
make_plt_section(Symbol_table* symtab, Layout* layout);
// Create a PLT entry for a global symbol.
void
make_plt_entry(Symbol_table*, Layout*, Symbol*);
// Create a PLT entry for a local STT_GNU_IFUNC symbol.
void
make_local_ifunc_plt_entry(Symbol_table*, Layout*,
Sized_relobj_file<size, false>* relobj,
unsigned int local_sym_index);
// Define the _TLS_MODULE_BASE_ symbol in the TLS segment.
void
define_tls_base_symbol(Symbol_table*, Layout*);
// Create the reserved PLT and GOT entries for the TLS descriptor resolver.
void
reserve_tlsdesc_entries(Symbol_table* symtab, Layout* layout);
// Create a GOT entry for the TLS module index.
unsigned int
got_mod_index_entry(Symbol_table* symtab, Layout* layout,
Sized_relobj_file<size, false>* object);
// Get the PLT section.
Output_data_plt_x86_64<size>*
plt_section() const
{
gold_assert(this->plt_ != NULL);
return this->plt_;
}
// Get the dynamic reloc section, creating it if necessary.
Reloc_section*
rela_dyn_section(Layout*);
// Get the section to use for TLSDESC relocations.
Reloc_section*
rela_tlsdesc_section(Layout*) const;
// Get the section to use for IRELATIVE relocations.
Reloc_section*
rela_irelative_section(Layout*);
// Add a potential copy relocation.
void
copy_reloc(Symbol_table* symtab, Layout* layout,
Sized_relobj_file<size, false>* object,
unsigned int shndx, Output_section* output_section,
Symbol* sym, const elfcpp::Rela<size, false>& reloc)
{
unsigned int r_type = elfcpp::elf_r_type<size>(reloc.get_r_info());
this->copy_relocs_.copy_reloc(symtab, layout,
symtab->get_sized_symbol<size>(sym),
object, shndx, output_section,
r_type, reloc.get_r_offset(),
reloc.get_r_addend(),
this->rela_dyn_section(layout));
}
// Information about this specific target which we pass to the
// general Target structure.
static const Target::Target_info x86_64_info;
// The types of GOT entries needed for this platform.
// These values are exposed to the ABI in an incremental link.
// Do not renumber existing values without changing the version
// number of the .gnu_incremental_inputs section.
enum Got_type
{
GOT_TYPE_STANDARD = 0, // GOT entry for a regular symbol
GOT_TYPE_TLS_OFFSET = 1, // GOT entry for TLS offset
GOT_TYPE_TLS_PAIR = 2, // GOT entry for TLS module/offset pair
GOT_TYPE_TLS_DESC = 3 // GOT entry for TLS_DESC pair
};
// This type is used as the argument to the target specific
// relocation routines. The only target specific reloc is
// R_X86_64_TLSDESC against a local symbol.
struct Tlsdesc_info
{
Tlsdesc_info(Sized_relobj_file<size, false>* a_object, unsigned int a_r_sym)
: object(a_object), r_sym(a_r_sym)
{ }
// The object in which the local symbol is defined.
Sized_relobj_file<size, false>* object;
// The local symbol index in the object.
unsigned int r_sym;
};
// The GOT section.
Output_data_got<64, false>* got_;
// The PLT section.
Output_data_plt_x86_64<size>* plt_;
// The GOT PLT section.
Output_data_got_plt_x86_64* got_plt_;
// The GOT section for IRELATIVE relocations.
Output_data_space* got_irelative_;
// The GOT section for TLSDESC relocations.
Output_data_got<64, false>* got_tlsdesc_;
// The _GLOBAL_OFFSET_TABLE_ symbol.
Symbol* global_offset_table_;
// The dynamic reloc section.
Reloc_section* rela_dyn_;
// The section to use for IRELATIVE relocs.
Reloc_section* rela_irelative_;
// Relocs saved to avoid a COPY reloc.
Copy_relocs<elfcpp::SHT_RELA, size, false> copy_relocs_;
// Offset of the GOT entry for the TLS module index.
unsigned int got_mod_index_offset_;
// We handle R_X86_64_TLSDESC against a local symbol as a target
// specific relocation. Here we store the object and local symbol
// index for the relocation.
std::vector<Tlsdesc_info> tlsdesc_reloc_info_;
// True if the _TLS_MODULE_BASE_ symbol has been defined.
bool tls_base_symbol_defined_;
};
template<>
const Target::Target_info Target_x86_64<64>::x86_64_info =
{
64, // size
false, // is_big_endian
elfcpp::EM_X86_64, // machine_code
false, // has_make_symbol
false, // has_resolve
true, // has_code_fill
true, // is_default_stack_executable
true, // can_icf_inline_merge_sections
'\0', // wrap_char
"/lib/ld64.so.1", // program interpreter
0x400000, // default_text_segment_address
0x1000, // abi_pagesize (overridable by -z max-page-size)
0x1000, // common_pagesize (overridable by -z common-page-size)
false, // isolate_execinstr
0, // rosegment_gap
elfcpp::SHN_UNDEF, // small_common_shndx
elfcpp::SHN_X86_64_LCOMMON, // large_common_shndx
0, // small_common_section_flags
elfcpp::SHF_X86_64_LARGE, // large_common_section_flags
NULL, // attributes_section
NULL, // attributes_vendor
"_start", // entry_symbol_name
32, // hash_entry_size
};
template<>
const Target::Target_info Target_x86_64<32>::x86_64_info =
{
32, // size
false, // is_big_endian
elfcpp::EM_X86_64, // machine_code
false, // has_make_symbol
false, // has_resolve
true, // has_code_fill
true, // is_default_stack_executable
true, // can_icf_inline_merge_sections
'\0', // wrap_char
"/libx32/ldx32.so.1", // program interpreter
0x400000, // default_text_segment_address
0x1000, // abi_pagesize (overridable by -z max-page-size)
0x1000, // common_pagesize (overridable by -z common-page-size)
false, // isolate_execinstr
0, // rosegment_gap
elfcpp::SHN_UNDEF, // small_common_shndx
elfcpp::SHN_X86_64_LCOMMON, // large_common_shndx
0, // small_common_section_flags
elfcpp::SHF_X86_64_LARGE, // large_common_section_flags
NULL, // attributes_section
NULL, // attributes_vendor
"_start", // entry_symbol_name
32, // hash_entry_size
};
// This is called when a new output section is created. This is where
// we handle the SHF_X86_64_LARGE.
template<int size>
void
Target_x86_64<size>::do_new_output_section(Output_section* os) const
{
if ((os->flags() & elfcpp::SHF_X86_64_LARGE) != 0)
os->set_is_large_section();
}
// Get the GOT section, creating it if necessary.
template<int size>
Output_data_got<64, false>*
Target_x86_64<size>::got_section(Symbol_table* symtab, Layout* layout)
{
if (this->got_ == NULL)
{
gold_assert(symtab != NULL && layout != NULL);
// When using -z now, we can treat .got.plt as a relro section.
// Without -z now, it is modified after program startup by lazy
// PLT relocations.
bool is_got_plt_relro = parameters->options().now();
Output_section_order got_order = (is_got_plt_relro
? ORDER_RELRO
: ORDER_RELRO_LAST);
Output_section_order got_plt_order = (is_got_plt_relro
? ORDER_RELRO
: ORDER_NON_RELRO_FIRST);
this->got_ = new Output_data_got<64, false>();
layout->add_output_section_data(".got", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_WRITE),
this->got_, got_order, true);
this->got_plt_ = new Output_data_got_plt_x86_64(layout);
layout->add_output_section_data(".got.plt", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_WRITE),
this->got_plt_, got_plt_order,
is_got_plt_relro);
// The first three entries are reserved.
this->got_plt_->set_current_data_size(3 * 8);
if (!is_got_plt_relro)
{
// Those bytes can go into the relro segment.
layout->increase_relro(3 * 8);
}
// Define _GLOBAL_OFFSET_TABLE_ at the start of the PLT.
this->global_offset_table_ =
symtab->define_in_output_data("_GLOBAL_OFFSET_TABLE_", NULL,
Symbol_table::PREDEFINED,
this->got_plt_,
0, 0, elfcpp::STT_OBJECT,
elfcpp::STB_LOCAL,
elfcpp::STV_HIDDEN, 0,
false, false);
// If there are any IRELATIVE relocations, they get GOT entries
// in .got.plt after the jump slot entries.
this->got_irelative_ = new Output_data_space(8, "** GOT IRELATIVE PLT");
layout->add_output_section_data(".got.plt", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_WRITE),
this->got_irelative_,
got_plt_order, is_got_plt_relro);
// If there are any TLSDESC relocations, they get GOT entries in
// .got.plt after the jump slot and IRELATIVE entries.
this->got_tlsdesc_ = new Output_data_got<64, false>();
layout->add_output_section_data(".got.plt", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_WRITE),
this->got_tlsdesc_,
got_plt_order, is_got_plt_relro);
}
return this->got_;
}
// Get the dynamic reloc section, creating it if necessary.
template<int size>
typename Target_x86_64<size>::Reloc_section*
Target_x86_64<size>::rela_dyn_section(Layout* layout)
{
if (this->rela_dyn_ == NULL)
{
gold_assert(layout != NULL);
this->rela_dyn_ = new Reloc_section(parameters->options().combreloc());
layout->add_output_section_data(".rela.dyn", elfcpp::SHT_RELA,
elfcpp::SHF_ALLOC, this->rela_dyn_,
ORDER_DYNAMIC_RELOCS, false);
}
return this->rela_dyn_;
}
// Get the section to use for IRELATIVE relocs, creating it if
// necessary. These go in .rela.dyn, but only after all other dynamic
// relocations. They need to follow the other dynamic relocations so
// that they can refer to global variables initialized by those
// relocs.
template<int size>
typename Target_x86_64<size>::Reloc_section*
Target_x86_64<size>::rela_irelative_section(Layout* layout)
{
if (this->rela_irelative_ == NULL)
{
// Make sure we have already created the dynamic reloc section.
this->rela_dyn_section(layout);
this->rela_irelative_ = new Reloc_section(false);
layout->add_output_section_data(".rela.dyn", elfcpp::SHT_RELA,
elfcpp::SHF_ALLOC, this->rela_irelative_,
ORDER_DYNAMIC_RELOCS, false);
gold_assert(this->rela_dyn_->output_section()
== this->rela_irelative_->output_section());
}
return this->rela_irelative_;
}
// Write the first three reserved words of the .got.plt section.
// The remainder of the section is written while writing the PLT
// in Output_data_plt_i386::do_write.
void
Output_data_got_plt_x86_64::do_write(Output_file* of)
{
// The first entry in the GOT is the address of the .dynamic section
// aka the PT_DYNAMIC segment. The next two entries are reserved.
// We saved space for them when we created the section in
// Target_x86_64::got_section.
const off_t got_file_offset = this->offset();
gold_assert(this->data_size() >= 24);
unsigned char* const got_view = of->get_output_view(got_file_offset, 24);
Output_section* dynamic = this->layout_->dynamic_section();
uint64_t dynamic_addr = dynamic == NULL ? 0 : dynamic->address();
elfcpp::Swap<64, false>::writeval(got_view, dynamic_addr);
memset(got_view + 8, 0, 16);
of->write_output_view(got_file_offset, 24, got_view);
}
// Initialize the PLT section.
template<int size>
void
Output_data_plt_x86_64<size>::init(Layout* layout)
{
this->rel_ = new Reloc_section(false);
layout->add_output_section_data(".rela.plt", elfcpp::SHT_RELA,
elfcpp::SHF_ALLOC, this->rel_,
ORDER_DYNAMIC_PLT_RELOCS, false);
}
template<int size>
void
Output_data_plt_x86_64<size>::do_adjust_output_section(Output_section* os)
{
os->set_entsize(this->get_plt_entry_size());
}
// Add an entry to the PLT.
template<int size>
void
Output_data_plt_x86_64<size>::add_entry(Symbol_table* symtab, Layout* layout,
Symbol* gsym)
{
gold_assert(!gsym->has_plt_offset());
unsigned int plt_index;
off_t plt_offset;
section_offset_type got_offset;
unsigned int* pcount;
unsigned int offset;
unsigned int reserved;
Output_section_data_build* got;
if (gsym->type() == elfcpp::STT_GNU_IFUNC
&& gsym->can_use_relative_reloc(false))
{
pcount = &this->irelative_count_;
offset = 0;
reserved = 0;
got = this->got_irelative_;
}
else
{
pcount = &this->count_;
offset = 1;
reserved = 3;
got = this->got_plt_;
}
if (!this->is_data_size_valid())
{
// Note that when setting the PLT offset for a non-IRELATIVE
// entry we skip the initial reserved PLT entry.
plt_index = *pcount + offset;
plt_offset = plt_index * this->get_plt_entry_size();
++*pcount;
got_offset = (plt_index - offset + reserved) * 8;
gold_assert(got_offset == got->current_data_size());
// Every PLT entry needs a GOT entry which points back to the PLT
// entry (this will be changed by the dynamic linker, normally
// lazily when the function is called).
got->set_current_data_size(got_offset + 8);
}
else
{
// FIXME: This is probably not correct for IRELATIVE relocs.
// For incremental updates, find an available slot.
plt_offset = this->free_list_.allocate(this->get_plt_entry_size(),
this->get_plt_entry_size(), 0);
if (plt_offset == -1)
gold_fallback(_("out of patch space (PLT);"
" relink with --incremental-full"));
// The GOT and PLT entries have a 1-1 correspondance, so the GOT offset
// can be calculated from the PLT index, adjusting for the three
// reserved entries at the beginning of the GOT.
plt_index = plt_offset / this->get_plt_entry_size() - 1;
got_offset = (plt_index - offset + reserved) * 8;
}
gsym->set_plt_offset(plt_offset);
// Every PLT entry needs a reloc.
this->add_relocation(symtab, layout, gsym, got_offset);
// Note that we don't need to save the symbol. The contents of the
// PLT are independent of which symbols are used. The symbols only
// appear in the relocations.
}
// Add an entry to the PLT for a local STT_GNU_IFUNC symbol. Return
// the PLT offset.
template<int size>
unsigned int
Output_data_plt_x86_64<size>::add_local_ifunc_entry(
Symbol_table* symtab,
Layout* layout,
Sized_relobj_file<size, false>* relobj,
unsigned int local_sym_index)
{
unsigned int plt_offset = this->irelative_count_ * this->get_plt_entry_size();
++this->irelative_count_;
section_offset_type got_offset = this->got_irelative_->current_data_size();
// Every PLT entry needs a GOT entry which points back to the PLT
// entry.
this->got_irelative_->set_current_data_size(got_offset + 8);
// Every PLT entry needs a reloc.
Reloc_section* rela = this->rela_irelative(symtab, layout);
rela->add_symbolless_local_addend(relobj, local_sym_index,
elfcpp::R_X86_64_IRELATIVE,
this->got_irelative_, got_offset, 0);
return plt_offset;
}
// Add the relocation for a PLT entry.
template<int size>
void
Output_data_plt_x86_64<size>::add_relocation(Symbol_table* symtab,
Layout* layout,
Symbol* gsym,
unsigned int got_offset)
{
if (gsym->type() == elfcpp::STT_GNU_IFUNC
&& gsym->can_use_relative_reloc(false))
{
Reloc_section* rela = this->rela_irelative(symtab, layout);
rela->add_symbolless_global_addend(gsym, elfcpp::R_X86_64_IRELATIVE,
this->got_irelative_, got_offset, 0);
}
else
{
gsym->set_needs_dynsym_entry();
this->rel_->add_global(gsym, elfcpp::R_X86_64_JUMP_SLOT, this->got_plt_,
got_offset, 0);
}
}
// Return where the TLSDESC relocations should go, creating it if
// necessary. These follow the JUMP_SLOT relocations.
template<int size>
typename Output_data_plt_x86_64<size>::Reloc_section*
Output_data_plt_x86_64<size>::rela_tlsdesc(Layout* layout)
{
if (this->tlsdesc_rel_ == NULL)
{
this->tlsdesc_rel_ = new Reloc_section(false);
layout->add_output_section_data(".rela.plt", elfcpp::SHT_RELA,
elfcpp::SHF_ALLOC, this->tlsdesc_rel_,
ORDER_DYNAMIC_PLT_RELOCS, false);
gold_assert(this->tlsdesc_rel_->output_section()
== this->rel_->output_section());
}
return this->tlsdesc_rel_;
}
// Return where the IRELATIVE relocations should go in the PLT. These
// follow the JUMP_SLOT and the TLSDESC relocations.
template<int size>
typename Output_data_plt_x86_64<size>::Reloc_section*
Output_data_plt_x86_64<size>::rela_irelative(Symbol_table* symtab,
Layout* layout)
{
if (this->irelative_rel_ == NULL)
{
// Make sure we have a place for the TLSDESC relocations, in
// case we see any later on.
this->rela_tlsdesc(layout);
this->irelative_rel_ = new Reloc_section(false);
layout->add_output_section_data(".rela.plt", elfcpp::SHT_RELA,
elfcpp::SHF_ALLOC, this->irelative_rel_,
ORDER_DYNAMIC_PLT_RELOCS, false);
gold_assert(this->irelative_rel_->output_section()
== this->rel_->output_section());
if (parameters->doing_static_link())
{
// A statically linked executable will only have a .rela.plt
// section to hold R_X86_64_IRELATIVE relocs for
// STT_GNU_IFUNC symbols. The library will use these
// symbols to locate the IRELATIVE relocs at program startup
// time.
symtab->define_in_output_data("__rela_iplt_start", NULL,
Symbol_table::PREDEFINED,
this->irelative_rel_, 0, 0,
elfcpp::STT_NOTYPE, elfcpp::STB_GLOBAL,
elfcpp::STV_HIDDEN, 0, false, true);
symtab->define_in_output_data("__rela_iplt_end", NULL,
Symbol_table::PREDEFINED,
this->irelative_rel_, 0, 0,
elfcpp::STT_NOTYPE, elfcpp::STB_GLOBAL,
elfcpp::STV_HIDDEN, 0, true, true);
}
}
return this->irelative_rel_;
}
// Return the PLT address to use for a global symbol.
template<int size>
uint64_t
Output_data_plt_x86_64<size>::address_for_global(const Symbol* gsym)
{
uint64_t offset = 0;
if (gsym->type() == elfcpp::STT_GNU_IFUNC
&& gsym->can_use_relative_reloc(false))
offset = (this->count_ + 1) * this->get_plt_entry_size();
return this->address() + offset + gsym->plt_offset();
}
// Return the PLT address to use for a local symbol. These are always
// IRELATIVE relocs.
template<int size>
uint64_t
Output_data_plt_x86_64<size>::address_for_local(const Relobj* object,
unsigned int r_sym)
{
return (this->address()
+ (this->count_ + 1) * this->get_plt_entry_size()
+ object->local_plt_offset(r_sym));
}
// Set the final size.
template<int size>
void
Output_data_plt_x86_64<size>::set_final_data_size()
{
unsigned int count = this->count_ + this->irelative_count_;
if (this->has_tlsdesc_entry())
++count;
this->set_data_size((count + 1) * this->get_plt_entry_size());
}
// The first entry in the PLT for an executable.
template<int size>
const unsigned char
Output_data_plt_x86_64_standard<size>::first_plt_entry[plt_entry_size] =
{
// From AMD64 ABI Draft 0.98, page 76
0xff, 0x35, // pushq contents of memory address
0, 0, 0, 0, // replaced with address of .got + 8
0xff, 0x25, // jmp indirect
0, 0, 0, 0, // replaced with address of .got + 16
0x90, 0x90, 0x90, 0x90 // noop (x4)
};
template<int size>
void
Output_data_plt_x86_64_standard<size>::do_fill_first_plt_entry(
unsigned char* pov,
typename elfcpp::Elf_types<size>::Elf_Addr got_address,
typename elfcpp::Elf_types<size>::Elf_Addr plt_address)
{
memcpy(pov, first_plt_entry, plt_entry_size);
// We do a jmp relative to the PC at the end of this instruction.
elfcpp::Swap_unaligned<32, false>::writeval(pov + 2,
(got_address + 8
- (plt_address + 6)));
elfcpp::Swap<32, false>::writeval(pov + 8,
(got_address + 16
- (plt_address + 12)));
}
// Subsequent entries in the PLT for an executable.
template<int size>
const unsigned char
Output_data_plt_x86_64_standard<size>::plt_entry[plt_entry_size] =
{
// From AMD64 ABI Draft 0.98, page 76
0xff, 0x25, // jmpq indirect
0, 0, 0, 0, // replaced with address of symbol in .got
0x68, // pushq immediate
0, 0, 0, 0, // replaced with offset into relocation table
0xe9, // jmpq relative
0, 0, 0, 0 // replaced with offset to start of .plt
};
template<int size>
unsigned int
Output_data_plt_x86_64_standard<size>::do_fill_plt_entry(
unsigned char* pov,
typename elfcpp::Elf_types<size>::Elf_Addr got_address,
typename elfcpp::Elf_types<size>::Elf_Addr plt_address,
unsigned int got_offset,
unsigned int plt_offset,
unsigned int plt_index)
{
// Check PC-relative offset overflow in PLT entry.
uint64_t plt_got_pcrel_offset = (got_address + got_offset
- (plt_address + plt_offset + 6));
if (Bits<32>::has_overflow(plt_got_pcrel_offset))
gold_error(_("PC-relative offset overflow in PLT entry %d"),
plt_index + 1);
memcpy(pov, plt_entry, plt_entry_size);
elfcpp::Swap_unaligned<32, false>::writeval(pov + 2,
plt_got_pcrel_offset);
elfcpp::Swap_unaligned<32, false>::writeval(pov + 7, plt_index);
elfcpp::Swap<32, false>::writeval(pov + 12,
- (plt_offset + plt_entry_size));
return 6;
}
// The reserved TLSDESC entry in the PLT for an executable.
template<int size>
const unsigned char
Output_data_plt_x86_64_standard<size>::tlsdesc_plt_entry[plt_entry_size] =
{
// From Alexandre Oliva, "Thread-Local Storage Descriptors for IA32
// and AMD64/EM64T", Version 0.9.4 (2005-10-10).
0xff, 0x35, // pushq x(%rip)
0, 0, 0, 0, // replaced with address of linkmap GOT entry (at PLTGOT + 8)
0xff, 0x25, // jmpq *y(%rip)
0, 0, 0, 0, // replaced with offset of reserved TLSDESC_GOT entry
0x0f, 0x1f, // nop
0x40, 0
};
template<int size>
void
Output_data_plt_x86_64_standard<size>::do_fill_tlsdesc_entry(
unsigned char* pov,
typename elfcpp::Elf_types<size>::Elf_Addr got_address,
typename elfcpp::Elf_types<size>::Elf_Addr plt_address,
typename elfcpp::Elf_types<size>::Elf_Addr got_base,
unsigned int tlsdesc_got_offset,
unsigned int plt_offset)
{
memcpy(pov, tlsdesc_plt_entry, plt_entry_size);
elfcpp::Swap_unaligned<32, false>::writeval(pov + 2,
(got_address + 8
- (plt_address + plt_offset
+ 6)));
elfcpp::Swap_unaligned<32, false>::writeval(pov + 8,
(got_base
+ tlsdesc_got_offset
- (plt_address + plt_offset
+ 12)));
}
// The .eh_frame unwind information for the PLT.
template<int size>
const unsigned char
Output_data_plt_x86_64<size>::plt_eh_frame_cie[plt_eh_frame_cie_size] =
{
1, // CIE version.
'z', // Augmentation: augmentation size included.
'R', // Augmentation: FDE encoding included.
'\0', // End of augmentation string.
1, // Code alignment factor.
0x78, // Data alignment factor.
16, // Return address column.
1, // Augmentation size.
(elfcpp::DW_EH_PE_pcrel // FDE encoding.
| elfcpp::DW_EH_PE_sdata4),
elfcpp::DW_CFA_def_cfa, 7, 8, // DW_CFA_def_cfa: r7 (rsp) ofs 8.
elfcpp::DW_CFA_offset + 16, 1,// DW_CFA_offset: r16 (rip) at cfa-8.
elfcpp::DW_CFA_nop, // Align to 16 bytes.
elfcpp::DW_CFA_nop
};
template<int size>
const unsigned char
Output_data_plt_x86_64_standard<size>::plt_eh_frame_fde[plt_eh_frame_fde_size] =
{
0, 0, 0, 0, // Replaced with offset to .plt.
0, 0, 0, 0, // Replaced with size of .plt.
0, // Augmentation size.
elfcpp::DW_CFA_def_cfa_offset, 16, // DW_CFA_def_cfa_offset: 16.
elfcpp::DW_CFA_advance_loc + 6, // Advance 6 to __PLT__ + 6.
elfcpp::DW_CFA_def_cfa_offset, 24, // DW_CFA_def_cfa_offset: 24.
elfcpp::DW_CFA_advance_loc + 10, // Advance 10 to __PLT__ + 16.
elfcpp::DW_CFA_def_cfa_expression, // DW_CFA_def_cfa_expression.
11, // Block length.
elfcpp::DW_OP_breg7, 8, // Push %rsp + 8.
elfcpp::DW_OP_breg16, 0, // Push %rip.
elfcpp::DW_OP_lit15, // Push 0xf.
elfcpp::DW_OP_and, // & (%rip & 0xf).
elfcpp::DW_OP_lit11, // Push 0xb.
elfcpp::DW_OP_ge, // >= ((%rip & 0xf) >= 0xb)
elfcpp::DW_OP_lit3, // Push 3.
elfcpp::DW_OP_shl, // << (((%rip & 0xf) >= 0xb) << 3)
elfcpp::DW_OP_plus, // + ((((%rip&0xf)>=0xb)<<3)+%rsp+8
elfcpp::DW_CFA_nop, // Align to 32 bytes.
elfcpp::DW_CFA_nop,
elfcpp::DW_CFA_nop,
elfcpp::DW_CFA_nop
};
// Write out the PLT. This uses the hand-coded instructions above,
// and adjusts them as needed. This is specified by the AMD64 ABI.
template<int size>
void
Output_data_plt_x86_64<size>::do_write(Output_file* of)
{
const off_t offset = this->offset();
const section_size_type oview_size =
convert_to_section_size_type(this->data_size());
unsigned char* const oview = of->get_output_view(offset, oview_size);
const off_t got_file_offset = this->got_plt_->offset();
gold_assert(parameters->incremental_update()
|| (got_file_offset + this->got_plt_->data_size()
== this->got_irelative_->offset()));
const section_size_type got_size =
convert_to_section_size_type(this->got_plt_->data_size()
+ this->got_irelative_->data_size());
unsigned char* const got_view = of->get_output_view(got_file_offset,
got_size);
unsigned char* pov = oview;
// The base address of the .plt section.
typename elfcpp::Elf_types<size>::Elf_Addr plt_address = this->address();
// The base address of the .got section.
typename elfcpp::Elf_types<size>::Elf_Addr got_base = this->got_->address();
// The base address of the PLT portion of the .got section,
// which is where the GOT pointer will point, and where the
// three reserved GOT entries are located.
typename elfcpp::Elf_types<size>::Elf_Addr got_address
= this->got_plt_->address();
this->fill_first_plt_entry(pov, got_address, plt_address);
pov += this->get_plt_entry_size();
// The first three entries in the GOT are reserved, and are written
// by Output_data_got_plt_x86_64::do_write.
unsigned char* got_pov = got_view + 24;
unsigned int plt_offset = this->get_plt_entry_size();
unsigned int got_offset = 24;
const unsigned int count = this->count_ + this->irelative_count_;
for (unsigned int plt_index = 0;
plt_index < count;
++plt_index,
pov += this->get_plt_entry_size(),
got_pov += 8,
plt_offset += this->get_plt_entry_size(),
got_offset += 8)
{
// Set and adjust the PLT entry itself.
unsigned int lazy_offset = this->fill_plt_entry(pov,
got_address, plt_address,
got_offset, plt_offset,
plt_index);
// Set the entry in the GOT.
elfcpp::Swap<64, false>::writeval(got_pov,
plt_address + plt_offset + lazy_offset);
}
if (this->has_tlsdesc_entry())
{
// Set and adjust the reserved TLSDESC PLT entry.
unsigned int tlsdesc_got_offset = this->get_tlsdesc_got_offset();
this->fill_tlsdesc_entry(pov, got_address, plt_address, got_base,
tlsdesc_got_offset, plt_offset);
pov += this->get_plt_entry_size();
}
gold_assert(static_cast<section_size_type>(pov - oview) == oview_size);
gold_assert(static_cast<section_size_type>(got_pov - got_view) == got_size);
of->write_output_view(offset, oview_size, oview);
of->write_output_view(got_file_offset, got_size, got_view);
}
// Create the PLT section.
template<int size>
void
Target_x86_64<size>::make_plt_section(Symbol_table* symtab, Layout* layout)
{
if (this->plt_ == NULL)
{
// Create the GOT sections first.
this->got_section(symtab, layout);
this->plt_ = this->make_data_plt(layout, this->got_, this->got_plt_,
this->got_irelative_);
// Add unwind information if requested.
if (parameters->options().ld_generated_unwind_info())
this->plt_->add_eh_frame(layout);
layout->add_output_section_data(".plt", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_EXECINSTR),
this->plt_, ORDER_PLT, false);
// Make the sh_info field of .rela.plt point to .plt.
Output_section* rela_plt_os = this->plt_->rela_plt()->output_section();
rela_plt_os->set_info_section(this->plt_->output_section());
}
}
// Return the section for TLSDESC relocations.
template<int size>
typename Target_x86_64<size>::Reloc_section*
Target_x86_64<size>::rela_tlsdesc_section(Layout* layout) const
{
return this->plt_section()->rela_tlsdesc(layout);
}
// Create a PLT entry for a global symbol.
template<int size>
void
Target_x86_64<size>::make_plt_entry(Symbol_table* symtab, Layout* layout,
Symbol* gsym)
{
if (gsym->has_plt_offset())
return;
if (this->plt_ == NULL)
this->make_plt_section(symtab, layout);
this->plt_->add_entry(symtab, layout, gsym);
}
// Make a PLT entry for a local STT_GNU_IFUNC symbol.
template<int size>
void
Target_x86_64<size>::make_local_ifunc_plt_entry(
Symbol_table* symtab, Layout* layout,
Sized_relobj_file<size, false>* relobj,
unsigned int local_sym_index)
{
if (relobj->local_has_plt_offset(local_sym_index))
return;
if (this->plt_ == NULL)
this->make_plt_section(symtab, layout);
unsigned int plt_offset = this->plt_->add_local_ifunc_entry(symtab, layout,
relobj,
local_sym_index);
relobj->set_local_plt_offset(local_sym_index, plt_offset);
}
// Return the number of entries in the PLT.
template<int size>
unsigned int
Target_x86_64<size>::plt_entry_count() const
{
if (this->plt_ == NULL)
return 0;
return this->plt_->entry_count();
}
// Return the offset of the first non-reserved PLT entry.
template<int size>
unsigned int
Target_x86_64<size>::first_plt_entry_offset() const
{
if (this->plt_ == NULL)
return 0;
return this->plt_->first_plt_entry_offset();
}
// Return the size of each PLT entry.
template<int size>
unsigned int
Target_x86_64<size>::plt_entry_size() const
{
if (this->plt_ == NULL)
return 0;
return this->plt_->get_plt_entry_size();
}
// Create the GOT and PLT sections for an incremental update.
template<int size>
Output_data_got_base*
Target_x86_64<size>::init_got_plt_for_update(Symbol_table* symtab,
Layout* layout,
unsigned int got_count,
unsigned int plt_count)
{
gold_assert(this->got_ == NULL);
this->got_ = new Output_data_got<64, false>(got_count * 8);
layout->add_output_section_data(".got", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_WRITE),
this->got_, ORDER_RELRO_LAST,
true);
// Add the three reserved entries.
this->got_plt_ = new Output_data_got_plt_x86_64(layout, (plt_count + 3) * 8);
layout->add_output_section_data(".got.plt", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_WRITE),
this->got_plt_, ORDER_NON_RELRO_FIRST,
false);
// Define _GLOBAL_OFFSET_TABLE_ at the start of the PLT.
this->global_offset_table_ =
symtab->define_in_output_data("_GLOBAL_OFFSET_TABLE_", NULL,
Symbol_table::PREDEFINED,
this->got_plt_,
0, 0, elfcpp::STT_OBJECT,
elfcpp::STB_LOCAL,
elfcpp::STV_HIDDEN, 0,
false, false);
// If there are any TLSDESC relocations, they get GOT entries in
// .got.plt after the jump slot entries.
// FIXME: Get the count for TLSDESC entries.
this->got_tlsdesc_ = new Output_data_got<64, false>(0);
layout->add_output_section_data(".got.plt", elfcpp::SHT_PROGBITS,
elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,
this->got_tlsdesc_,
ORDER_NON_RELRO_FIRST, false);
// If there are any IRELATIVE relocations, they get GOT entries in
// .got.plt after the jump slot and TLSDESC entries.
this->got_irelative_ = new Output_data_space(0, 8, "** GOT IRELATIVE PLT");
layout->add_output_section_data(".got.plt", elfcpp::SHT_PROGBITS,
elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,
this->got_irelative_,
ORDER_NON_RELRO_FIRST, false);
// Create the PLT section.
this->plt_ = this->make_data_plt(layout, this->got_,
this->got_plt_,
this->got_irelative_,
plt_count);
// Add unwind information if requested.
if (parameters->options().ld_generated_unwind_info())
this->plt_->add_eh_frame(layout);
layout->add_output_section_data(".plt", elfcpp::SHT_PROGBITS,
elfcpp::SHF_ALLOC | elfcpp::SHF_EXECINSTR,
this->plt_, ORDER_PLT, false);
// Make the sh_info field of .rela.plt point to .plt.
Output_section* rela_plt_os = this->plt_->rela_plt()->output_section();
rela_plt_os->set_info_section(this->plt_->output_section());
// Create the rela_dyn section.
this->rela_dyn_section(layout);
return this->got_;
}
// Reserve a GOT entry for a local symbol, and regenerate any
// necessary dynamic relocations.
template<int size>
void
Target_x86_64<size>::reserve_local_got_entry(
unsigned int got_index,
Sized_relobj<size, false>* obj,
unsigned int r_sym,
unsigned int got_type)
{
unsigned int got_offset = got_index * 8;
Reloc_section* rela_dyn = this->rela_dyn_section(NULL);
this->got_->reserve_local(got_index, obj, r_sym, got_type);
switch (got_type)
{
case GOT_TYPE_STANDARD:
if (parameters->options().output_is_position_independent())
rela_dyn->add_local_relative(obj, r_sym, elfcpp::R_X86_64_RELATIVE,
this->got_, got_offset, 0, false);
break;
case GOT_TYPE_TLS_OFFSET:
rela_dyn->add_local(obj, r_sym, elfcpp::R_X86_64_TPOFF64,
this->got_, got_offset, 0);
break;
case GOT_TYPE_TLS_PAIR:
this->got_->reserve_slot(got_index + 1);
rela_dyn->add_local(obj, r_sym, elfcpp::R_X86_64_DTPMOD64,
this->got_, got_offset, 0);
break;
case GOT_TYPE_TLS_DESC:
gold_fatal(_("TLS_DESC not yet supported for incremental linking"));
// this->got_->reserve_slot(got_index + 1);
// rela_dyn->add_target_specific(elfcpp::R_X86_64_TLSDESC, arg,
// this->got_, got_offset, 0);
break;
default:
gold_unreachable();
}
}
// Reserve a GOT entry for a global symbol, and regenerate any
// necessary dynamic relocations.
template<int size>
void
Target_x86_64<size>::reserve_global_got_entry(unsigned int got_index,
Symbol* gsym,
unsigned int got_type)
{
unsigned int got_offset = got_index * 8;
Reloc_section* rela_dyn = this->rela_dyn_section(NULL);
this->got_->reserve_global(got_index, gsym, got_type);
switch (got_type)
{
case GOT_TYPE_STANDARD:
if (!gsym->final_value_is_known())
{
if (gsym->is_from_dynobj()
|| gsym->is_undefined()
|| gsym->is_preemptible()
|| gsym->type() == elfcpp::STT_GNU_IFUNC)
rela_dyn->add_global(gsym, elfcpp::R_X86_64_GLOB_DAT,
this->got_, got_offset, 0);
else
rela_dyn->add_global_relative(gsym, elfcpp::R_X86_64_RELATIVE,
this->got_, got_offset, 0, false);
}
break;
case GOT_TYPE_TLS_OFFSET:
rela_dyn->add_global_relative(gsym, elfcpp::R_X86_64_TPOFF64,
this->got_, got_offset, 0, false);
break;
case GOT_TYPE_TLS_PAIR:
this->got_->reserve_slot(got_index + 1);
rela_dyn->add_global_relative(gsym, elfcpp::R_X86_64_DTPMOD64,
this->got_, got_offset, 0, false);
rela_dyn->add_global_relative(gsym, elfcpp::R_X86_64_DTPOFF64,
this->got_, got_offset + 8, 0, false);
break;
case GOT_TYPE_TLS_DESC:
this->got_->reserve_slot(got_index + 1);
rela_dyn->add_global_relative(gsym, elfcpp::R_X86_64_TLSDESC,
this->got_, got_offset, 0, false);
break;
default:
gold_unreachable();
}
}
// Register an existing PLT entry for a global symbol.
template<int size>
void
Target_x86_64<size>::register_global_plt_entry(Symbol_table* symtab,
Layout* layout,
unsigned int plt_index,
Symbol* gsym)
{
gold_assert(this->plt_ != NULL);
gold_assert(!gsym->has_plt_offset());
this->plt_->reserve_slot(plt_index);
gsym->set_plt_offset((plt_index + 1) * this->plt_entry_size());
unsigned int got_offset = (plt_index + 3) * 8;
this->plt_->add_relocation(symtab, layout, gsym, got_offset);
}
// Force a COPY relocation for a given symbol.
template<int size>
void
Target_x86_64<size>::emit_copy_reloc(
Symbol_table* symtab, Symbol* sym, Output_section* os, off_t offset)
{
this->copy_relocs_.emit_copy_reloc(symtab,
symtab->get_sized_symbol<size>(sym),
os,
offset,
this->rela_dyn_section(NULL));
}
// Define the _TLS_MODULE_BASE_ symbol in the TLS segment.
template<int size>
void
Target_x86_64<size>::define_tls_base_symbol(Symbol_table* symtab,
Layout* layout)
{
if (this->tls_base_symbol_defined_)
return;
Output_segment* tls_segment = layout->tls_segment();
if (tls_segment != NULL)
{
bool is_exec = parameters->options().output_is_executable();
symtab->define_in_output_segment("_TLS_MODULE_BASE_", NULL,
Symbol_table::PREDEFINED,
tls_segment, 0, 0,
elfcpp::STT_TLS,
elfcpp::STB_LOCAL,
elfcpp::STV_HIDDEN, 0,
(is_exec
? Symbol::SEGMENT_END
: Symbol::SEGMENT_START),
true);
}
this->tls_base_symbol_defined_ = true;
}
// Create the reserved PLT and GOT entries for the TLS descriptor resolver.
template<int size>
void
Target_x86_64<size>::reserve_tlsdesc_entries(Symbol_table* symtab,
Layout* layout)
{
if (this->plt_ == NULL)
this->make_plt_section(symtab, layout);
if (!this->plt_->has_tlsdesc_entry())
{
// Allocate the TLSDESC_GOT entry.
Output_data_got<64, false>* got = this->got_section(symtab, layout);
unsigned int got_offset = got->add_constant(0);
// Allocate the TLSDESC_PLT entry.
this->plt_->reserve_tlsdesc_entry(got_offset);
}
}
// Create a GOT entry for the TLS module index.
template<int size>
unsigned int
Target_x86_64<size>::got_mod_index_entry(Symbol_table* symtab, Layout* layout,
Sized_relobj_file<size, false>* object)
{
if (this->got_mod_index_offset_ == -1U)
{
gold_assert(symtab != NULL && layout != NULL && object != NULL);
Reloc_section* rela_dyn = this->rela_dyn_section(layout);
Output_data_got<64, false>* got = this->got_section(symtab, layout);
unsigned int got_offset = got->add_constant(0);
rela_dyn->add_local(object, 0, elfcpp::R_X86_64_DTPMOD64, got,
got_offset, 0);
got->add_constant(0);
this->got_mod_index_offset_ = got_offset;
}
return this->got_mod_index_offset_;
}
// Optimize the TLS relocation type based on what we know about the
// symbol. IS_FINAL is true if the final address of this symbol is
// known at link time.
template<int size>
tls::Tls_optimization
Target_x86_64<size>::optimize_tls_reloc(bool is_final, int r_type)
{
// If we are generating a shared library, then we can't do anything
// in the linker.
if (parameters->options().shared())
return tls::TLSOPT_NONE;
switch (r_type)
{
case elfcpp::R_X86_64_TLSGD:
case elfcpp::R_X86_64_GOTPC32_TLSDESC:
case elfcpp::R_X86_64_TLSDESC_CALL:
// These are General-Dynamic which permits fully general TLS
// access. Since we know that we are generating an executable,
// we can convert this to Initial-Exec. If we also know that
// this is a local symbol, we can further switch to Local-Exec.
if (is_final)
return tls::TLSOPT_TO_LE;
return tls::TLSOPT_TO_IE;
case elfcpp::R_X86_64_TLSLD:
// This is Local-Dynamic, which refers to a local symbol in the
// dynamic TLS block. Since we know that we generating an
// executable, we can switch to Local-Exec.
return tls::TLSOPT_TO_LE;
case elfcpp::R_X86_64_DTPOFF32:
case elfcpp::R_X86_64_DTPOFF64:
// Another Local-Dynamic reloc.
return tls::TLSOPT_TO_LE;
case elfcpp::R_X86_64_GOTTPOFF:
// These are Initial-Exec relocs which get the thread offset
// from the GOT. If we know that we are linking against the
// local symbol, we can switch to Local-Exec, which links the
// thread offset into the instruction.
if (is_final)
return tls::TLSOPT_TO_LE;
return tls::TLSOPT_NONE;
case elfcpp::R_X86_64_TPOFF32:
// When we already have Local-Exec, there is nothing further we
// can do.
return tls::TLSOPT_NONE;
default:
gold_unreachable();
}
}
// Get the Reference_flags for a particular relocation.
template<int size>
int
Target_x86_64<size>::Scan::get_reference_flags(unsigned int r_type)
{
switch (r_type)
{
case elfcpp::R_X86_64_NONE:
case elfcpp::R_X86_64_GNU_VTINHERIT:
case elfcpp::R_X86_64_GNU_VTENTRY:
case elfcpp::R_X86_64_GOTPC32:
case elfcpp::R_X86_64_GOTPC64:
// No symbol reference.
return 0;
case elfcpp::R_X86_64_64:
case elfcpp::R_X86_64_32:
case elfcpp::R_X86_64_32S:
case elfcpp::R_X86_64_16:
case elfcpp::R_X86_64_8:
return Symbol::ABSOLUTE_REF;
case elfcpp::R_X86_64_PC64:
case elfcpp::R_X86_64_PC32:
case elfcpp::R_X86_64_PC32_BND:
case elfcpp::R_X86_64_PC16:
case elfcpp::R_X86_64_PC8:
case elfcpp::R_X86_64_GOTOFF64:
return Symbol::RELATIVE_REF;
case elfcpp::R_X86_64_PLT32:
case elfcpp::R_X86_64_PLT32_BND:
case elfcpp::R_X86_64_PLTOFF64:
return Symbol::FUNCTION_CALL | Symbol::RELATIVE_REF;
case elfcpp::R_X86_64_GOT64:
case elfcpp::R_X86_64_GOT32:
case elfcpp::R_X86_64_GOTPCREL64:
case elfcpp::R_X86_64_GOTPCREL:
case elfcpp::R_X86_64_GOTPCRELX:
case elfcpp::R_X86_64_REX_GOTPCRELX:
case elfcpp::R_X86_64_GOTPLT64:
// Absolute in GOT.
return Symbol::ABSOLUTE_REF;
case elfcpp::R_X86_64_TLSGD: // Global-dynamic
case elfcpp::R_X86_64_GOTPC32_TLSDESC: // Global-dynamic (from ~oliva url)
case elfcpp::R_X86_64_TLSDESC_CALL:
case elfcpp::R_X86_64_TLSLD: // Local-dynamic
case elfcpp::R_X86_64_DTPOFF32:
case elfcpp::R_X86_64_DTPOFF64:
case elfcpp::R_X86_64_GOTTPOFF: // Initial-exec
case elfcpp::R_X86_64_TPOFF32: // Local-exec
return Symbol::TLS_REF;
case elfcpp::R_X86_64_COPY:
case elfcpp::R_X86_64_GLOB_DAT:
case elfcpp::R_X86_64_JUMP_SLOT:
case elfcpp::R_X86_64_RELATIVE:
case elfcpp::R_X86_64_IRELATIVE:
case elfcpp::R_X86_64_TPOFF64:
case elfcpp::R_X86_64_DTPMOD64:
case elfcpp::R_X86_64_TLSDESC:
case elfcpp::R_X86_64_SIZE32:
case elfcpp::R_X86_64_SIZE64:
default:
// Not expected. We will give an error later.
return 0;
}
}
// Report an unsupported relocation against a local symbol.
template<int size>
void
Target_x86_64<size>::Scan::unsupported_reloc_local(
Sized_relobj_file<size, false>* object,
unsigned int r_type)
{
gold_error(_("%s: unsupported reloc %u against local symbol"),
object->name().c_str(), r_type);
}
// We are about to emit a dynamic relocation of type R_TYPE. If the
// dynamic linker does not support it, issue an error. The GNU linker
// only issues a non-PIC error for an allocated read-only section.
// Here we know the section is allocated, but we don't know that it is
// read-only. But we check for all the relocation types which the
// glibc dynamic linker supports, so it seems appropriate to issue an
// error even if the section is not read-only. If GSYM is not NULL,
// it is the symbol the relocation is against; if it is NULL, the
// relocation is against a local symbol.
template<int size>
void
Target_x86_64<size>::Scan::check_non_pic(Relobj* object, unsigned int r_type,
Symbol* gsym)
{
switch (r_type)
{
// These are the relocation types supported by glibc for x86_64
// which should always work.
case elfcpp::R_X86_64_RELATIVE:
case elfcpp::R_X86_64_IRELATIVE:
case elfcpp::R_X86_64_GLOB_DAT:
case elfcpp::R_X86_64_JUMP_SLOT:
case elfcpp::R_X86_64_DTPMOD64:
case elfcpp::R_X86_64_DTPOFF64:
case elfcpp::R_X86_64_TPOFF64:
case elfcpp::R_X86_64_64:
case elfcpp::R_X86_64_COPY:
return;
// glibc supports these reloc types, but they can overflow.
case elfcpp::R_X86_64_PC32:
case elfcpp::R_X86_64_PC32_BND:
// A PC relative reference is OK against a local symbol or if
// the symbol is defined locally.
if (gsym == NULL
|| (!gsym->is_from_dynobj()
&& !gsym->is_undefined()
&& !gsym->is_preemptible()))
return;
/* Fall through. */
case elfcpp::R_X86_64_32:
// R_X86_64_32 is OK for x32.
if (size == 32 && r_type == elfcpp::R_X86_64_32)
return;
if (this->issued_non_pic_error_)
return;
gold_assert(parameters->options().output_is_position_independent());
if (gsym == NULL)
object->error(_("requires dynamic R_X86_64_32 reloc which may "
"overflow at runtime; recompile with -fPIC"));
else
{
const char *r_name;
switch (r_type)
{
case elfcpp::R_X86_64_32:
r_name = "R_X86_64_32";
break;
case elfcpp::R_X86_64_PC32:
r_name = "R_X86_64_PC32";
break;
case elfcpp::R_X86_64_PC32_BND:
r_name = "R_X86_64_PC32_BND";
break;
default:
gold_unreachable();
break;
}
object->error(_("requires dynamic %s reloc against '%s' "
"which may overflow at runtime; recompile "
"with -fPIC"),
r_name, gsym->name());
}
this->issued_non_pic_error_ = true;
return;
default:
// This prevents us from issuing more than one error per reloc
// section. But we can still wind up issuing more than one
// error per object file.
if (this->issued_non_pic_error_)
return;
gold_assert(parameters->options().output_is_position_independent());
object->error(_("requires unsupported dynamic reloc %u; "
"recompile with -fPIC"),
r_type);
this->issued_non_pic_error_ = true;
return;
case elfcpp::R_X86_64_NONE:
gold_unreachable();
}
}
// Return whether we need to make a PLT entry for a relocation of the
// given type against a STT_GNU_IFUNC symbol.
template<int size>
bool
Target_x86_64<size>::Scan::reloc_needs_plt_for_ifunc(
Sized_relobj_file<size, false>* object,
unsigned int r_type)
{
int flags = Scan::get_reference_flags(r_type);
if (flags & Symbol::TLS_REF)
gold_error(_("%s: unsupported TLS reloc %u for IFUNC symbol"),
object->name().c_str(), r_type);
return flags != 0;
}
// Scan a relocation for a local symbol.
template<int size>
inline void
Target_x86_64<size>::Scan::local(Symbol_table* symtab,
Layout* layout,
Target_x86_64<size>* target,
Sized_relobj_file<size, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rela<size, false>& reloc,
unsigned int r_type,
const elfcpp::Sym<size, false>& lsym,
bool is_discarded)
{
if (is_discarded)
return;
// A local STT_GNU_IFUNC symbol may require a PLT entry.
bool is_ifunc = lsym.get_st_type() == elfcpp::STT_GNU_IFUNC;
if (is_ifunc && this->reloc_needs_plt_for_ifunc(object, r_type))
{
unsigned int r_sym = elfcpp::elf_r_sym<size>(reloc.get_r_info());
target->make_local_ifunc_plt_entry(symtab, layout, object, r_sym);
}
switch (r_type)
{
case elfcpp::R_X86_64_NONE:
case elfcpp::R_X86_64_GNU_VTINHERIT:
case elfcpp::R_X86_64_GNU_VTENTRY:
break;
case elfcpp::R_X86_64_64:
// If building a shared library (or a position-independent
// executable), we need to create a dynamic relocation for this
// location. The relocation applied at link time will apply the
// link-time value, so we flag the location with an
// R_X86_64_RELATIVE relocation so the dynamic loader can
// relocate it easily.
if (parameters->options().output_is_position_independent())
{
unsigned int r_sym = elfcpp::elf_r_sym<size>(reloc.get_r_info());
Reloc_section* rela_dyn = target->rela_dyn_section(layout);
rela_dyn->add_local_relative(object, r_sym,
(size == 32
? elfcpp::R_X86_64_RELATIVE64
: elfcpp::R_X86_64_RELATIVE),
output_section, data_shndx,
reloc.get_r_offset(),
reloc.get_r_addend(), is_ifunc);
}
break;
case elfcpp::R_X86_64_32:
case elfcpp::R_X86_64_32S:
case elfcpp::R_X86_64_16:
case elfcpp::R_X86_64_8:
// If building a shared library (or a position-independent
// executable), we need to create a dynamic relocation for this
// location. We can't use an R_X86_64_RELATIVE relocation
// because that is always a 64-bit relocation.
if (parameters->options().output_is_position_independent())
{
// Use R_X86_64_RELATIVE relocation for R_X86_64_32 under x32.
if (size == 32 && r_type == elfcpp::R_X86_64_32)
{
unsigned int r_sym = elfcpp::elf_r_sym<size>(reloc.get_r_info());
Reloc_section* rela_dyn = target->rela_dyn_section(layout);
rela_dyn->add_local_relative(object, r_sym,
elfcpp::R_X86_64_RELATIVE,
output_section, data_shndx,
reloc.get_r_offset(),
reloc.get_r_addend(), is_ifunc);
break;
}
this->check_non_pic(object, r_type, NULL);
Reloc_section* rela_dyn = target->rela_dyn_section(layout);
unsigned int r_sym = elfcpp::elf_r_sym<size>(reloc.get_r_info());
if (lsym.get_st_type() != elfcpp::STT_SECTION)
rela_dyn->add_local(object, r_sym, r_type, output_section,
data_shndx, reloc.get_r_offset(),
reloc.get_r_addend());
else
{
gold_assert(lsym.get_st_value() == 0);
unsigned int shndx = lsym.get_st_shndx();
bool is_ordinary;
shndx = object->adjust_sym_shndx(r_sym, shndx,
&is_ordinary);
if (!is_ordinary)
object->error(_("section symbol %u has bad shndx %u"),
r_sym, shndx);
else
rela_dyn->add_local_section(object, shndx,
r_type, output_section,
data_shndx, reloc.get_r_offset(),
reloc.get_r_addend());
}
}
break;
case elfcpp::R_X86_64_PC64:
case elfcpp::R_X86_64_PC32:
case elfcpp::R_X86_64_PC32_BND:
case elfcpp::R_X86_64_PC16:
case elfcpp::R_X86_64_PC8:
break;
case elfcpp::R_X86_64_PLT32:
case elfcpp::R_X86_64_PLT32_BND:
// Since we know this is a local symbol, we can handle this as a
// PC32 reloc.
break;
case elfcpp::R_X86_64_GOTPC32:
case elfcpp::R_X86_64_GOTOFF64:
case elfcpp::R_X86_64_GOTPC64:
case elfcpp::R_X86_64_PLTOFF64:
// We need a GOT section.
target->got_section(symtab, layout);
// For PLTOFF64, we'd normally want a PLT section, but since we
// know this is a local symbol, no PLT is needed.
break;
case elfcpp::R_X86_64_GOT64:
case elfcpp::R_X86_64_GOT32:
case elfcpp::R_X86_64_GOTPCREL64:
case elfcpp::R_X86_64_GOTPCREL:
case elfcpp::R_X86_64_GOTPCRELX:
case elfcpp::R_X86_64_REX_GOTPCRELX:
case elfcpp::R_X86_64_GOTPLT64:
{
// The symbol requires a GOT section.
Output_data_got<64, false>* got = target->got_section(symtab, layout);
// If the relocation symbol isn't IFUNC,
// and is local, then we will convert
// mov foo@GOTPCREL(%rip), %reg
// to lea foo(%rip), %reg.
// in Relocate::relocate.
if ((r_type == elfcpp::R_X86_64_GOTPCREL
|| r_type == elfcpp::R_X86_64_GOTPCRELX
|| r_type == elfcpp::R_X86_64_REX_GOTPCRELX)
&& reloc.get_r_offset() >= 2
&& !is_ifunc)
{
section_size_type stype;
const unsigned char* view = object->section_contents(data_shndx,
&stype, true);
if (view[reloc.get_r_offset() - 2] == 0x8b)
break;
}
// The symbol requires a GOT entry.
unsigned int r_sym = elfcpp::elf_r_sym<size>(reloc.get_r_info());
// For a STT_GNU_IFUNC symbol we want the PLT offset. That
// lets function pointers compare correctly with shared
// libraries. Otherwise we would need an IRELATIVE reloc.
bool is_new;
if (is_ifunc)
is_new = got->add_local_plt(object, r_sym, GOT_TYPE_STANDARD);
else
is_new = got->add_local(object, r_sym, GOT_TYPE_STANDARD);
if (is_new)
{
// If we are generating a shared object, we need to add a
// dynamic relocation for this symbol's GOT entry.
if (parameters->options().output_is_position_independent())
{
Reloc_section* rela_dyn = target->rela_dyn_section(layout);
// R_X86_64_RELATIVE assumes a 64-bit relocation.
if (r_type != elfcpp::R_X86_64_GOT32)
{
unsigned int got_offset =
object->local_got_offset(r_sym, GOT_TYPE_STANDARD);
rela_dyn->add_local_relative(object, r_sym,
elfcpp::R_X86_64_RELATIVE,
got, got_offset, 0, is_ifunc);
}
else
{
this->check_non_pic(object, r_type, NULL);
gold_assert(lsym.get_st_type() != elfcpp::STT_SECTION);
rela_dyn->add_local(
object, r_sym, r_type, got,
object->local_got_offset(r_sym, GOT_TYPE_STANDARD), 0);
}
}
}
// For GOTPLT64, we'd normally want a PLT section, but since
// we know this is a local symbol, no PLT is needed.
}
break;
case elfcpp::R_X86_64_COPY:
case elfcpp::R_X86_64_GLOB_DAT:
case elfcpp::R_X86_64_JUMP_SLOT:
case elfcpp::R_X86_64_RELATIVE:
case elfcpp::R_X86_64_IRELATIVE:
// These are outstanding tls relocs, which are unexpected when linking
case elfcpp::R_X86_64_TPOFF64:
case elfcpp::R_X86_64_DTPMOD64:
case elfcpp::R_X86_64_TLSDESC:
gold_error(_("%s: unexpected reloc %u in object file"),
object->name().c_str(), r_type);
break;
// These are initial tls relocs, which are expected when linking
case elfcpp::R_X86_64_TLSGD: // Global-dynamic
case elfcpp::R_X86_64_GOTPC32_TLSDESC: // Global-dynamic (from ~oliva url)
case elfcpp::R_X86_64_TLSDESC_CALL:
case elfcpp::R_X86_64_TLSLD: // Local-dynamic
case elfcpp::R_X86_64_DTPOFF32:
case elfcpp::R_X86_64_DTPOFF64:
case elfcpp::R_X86_64_GOTTPOFF: // Initial-exec
case elfcpp::R_X86_64_TPOFF32: // Local-exec
{
bool output_is_shared = parameters->options().shared();
const tls::Tls_optimization optimized_type
= Target_x86_64<size>::optimize_tls_reloc(!output_is_shared,
r_type);
switch (r_type)
{
case elfcpp::R_X86_64_TLSGD: // General-dynamic
if (optimized_type == tls::TLSOPT_NONE)
{
// Create a pair of GOT entries for the module index and
// dtv-relative offset.
Output_data_got<64, false>* got
= target->got_section(symtab, layout);
unsigned int r_sym = elfcpp::elf_r_sym<size>(reloc.get_r_info());
unsigned int shndx = lsym.get_st_shndx();
bool is_ordinary;
shndx = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary);
if (!is_ordinary)
object->error(_("local symbol %u has bad shndx %u"),
r_sym, shndx);
else
got->add_local_pair_with_rel(object, r_sym,
shndx,
GOT_TYPE_TLS_PAIR,
target->rela_dyn_section(layout),
elfcpp::R_X86_64_DTPMOD64);
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_local(object, r_type);
break;
case elfcpp::R_X86_64_GOTPC32_TLSDESC:
target->define_tls_base_symbol(symtab, layout);
if (optimized_type == tls::TLSOPT_NONE)
{
// Create reserved PLT and GOT entries for the resolver.
target->reserve_tlsdesc_entries(symtab, layout);
// Generate a double GOT entry with an
// R_X86_64_TLSDESC reloc. The R_X86_64_TLSDESC reloc
// is resolved lazily, so the GOT entry needs to be in
// an area in .got.plt, not .got. Call got_section to
// make sure the section has been created.
target->got_section(symtab, layout);
Output_data_got<64, false>* got = target->got_tlsdesc_section();
unsigned int r_sym = elfcpp::elf_r_sym<size>(reloc.get_r_info());
if (!object->local_has_got_offset(r_sym, GOT_TYPE_TLS_DESC))
{
unsigned int got_offset = got->add_constant(0);
got->add_constant(0);
object->set_local_got_offset(r_sym, GOT_TYPE_TLS_DESC,
got_offset);
Reloc_section* rt = target->rela_tlsdesc_section(layout);
// We store the arguments we need in a vector, and
// use the index into the vector as the parameter
// to pass to the target specific routines.
uintptr_t intarg = target->add_tlsdesc_info(object, r_sym);
void* arg = reinterpret_cast<void*>(intarg);
rt->add_target_specific(elfcpp::