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// i386.cc -- i386 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 "i386.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"
namespace
{
using namespace gold;
// A class to handle the .got.plt section.
class Output_data_got_plt_i386 : public Output_section_data_build
{
public:
Output_data_got_plt_i386(Layout* layout)
: Output_section_data_build(4),
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.
class Output_data_plt_i386 : public Output_section_data
{
public:
typedef Output_data_reloc<elfcpp::SHT_REL, true, 32, false> Reloc_section;
Output_data_plt_i386(Layout*, uint64_t addralign,
Output_data_got_plt_i386*, Output_data_space*);
// 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*, Layout*,
Sized_relobj_file<32, false>* relobj,
unsigned int local_sym_index);
// Return the .rel.plt section data.
Reloc_section*
rel_plt() const
{ return this->rel_; }
// Return where the TLS_DESC relocations should go.
Reloc_section*
rel_tls_desc(Layout*);
// Return where the IRELATIVE relocations should go.
Reloc_section*
rel_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(); }
// 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 the first PLT entry, given the pointer to the PLT section data
// and the runtime address of the GOT.
void
fill_first_plt_entry(unsigned char* pov,
elfcpp::Elf_types<32>::Elf_Addr got_address)
{ this->do_fill_first_plt_entry(pov, got_address); }
// Fill a normal PLT entry, given the pointer to the entry's data in the
// section, the runtime address of the GOT, the offset into the GOT of
// the corresponding slot, the offset into the relocation section of the
// corresponding reloc, and the offset of this entry within the whole
// PLT. Return the offset from this PLT entry's runtime address that
// should be used to compute the initial value of the GOT slot.
unsigned int
fill_plt_entry(unsigned char* pov,
elfcpp::Elf_types<32>::Elf_Addr got_address,
unsigned int got_offset,
unsigned int plt_offset,
unsigned int plt_rel_offset)
{
return this->do_fill_plt_entry(pov, got_address, got_offset,
plt_offset, plt_rel_offset);
}
virtual unsigned int
do_get_plt_entry_size() const = 0;
virtual void
do_fill_first_plt_entry(unsigned char* pov,
elfcpp::Elf_types<32>::Elf_Addr got_address) = 0;
virtual unsigned int
do_fill_plt_entry(unsigned char* pov,
elfcpp::Elf_types<32>::Elf_Addr got_address,
unsigned int got_offset,
unsigned int plt_offset,
unsigned int plt_rel_offset) = 0;
virtual void
do_add_eh_frame(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 .eh_frame unwind information for the PLT.
// The CIE is common across variants of the PLT format.
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()
{
this->set_data_size((this->count_ + this->irelative_count_ + 1)
* this->get_plt_entry_size());
}
// Write out the PLT data.
void
do_write(Output_file*);
// We keep a list of global STT_GNU_IFUNC symbols, each with its
// offset in the GOT.
struct Global_ifunc
{
Symbol* sym;
unsigned int got_offset;
};
// We keep a list of local STT_GNU_IFUNC symbols, each with its
// offset in the GOT.
struct Local_ifunc
{
Sized_relobj_file<32, false>* object;
unsigned int local_sym_index;
unsigned int got_offset;
};
// The reloc section.
Reloc_section* rel_;
// The TLS_DESC relocations, if necessary. These must follow the
// regular PLT relocs.
Reloc_section* tls_desc_rel_;
// The IRELATIVE relocations, if necessary. These must follow the
// regular relocatoins and the TLS_DESC relocations.
Reloc_section* irelative_rel_;
// The .got.plt section.
Output_data_got_plt_i386* 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_386_IRELATIVE relocs. These follow
// the regular PLT entries.
unsigned int irelative_count_;
// Global STT_GNU_IFUNC symbols.
std::vector<Global_ifunc> global_ifuncs_;
// Local STT_GNU_IFUNC symbols.
std::vector<Local_ifunc> local_ifuncs_;
};
// This is an abstract class for the standard PLT layout.
// The derived classes below handle the actual PLT contents
// for the executable (non-PIC) and shared-library (PIC) cases.
// The unwind information is uniform across those two, so it's here.
class Output_data_plt_i386_standard : public Output_data_plt_i386
{
public:
Output_data_plt_i386_standard(Layout* layout,
Output_data_got_plt_i386* got_plt,
Output_data_space* got_irelative)
: Output_data_plt_i386(layout, plt_entry_size, got_plt, got_irelative)
{ }
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, plt_eh_frame_cie, plt_eh_frame_cie_size,
plt_eh_frame_fde, plt_eh_frame_fde_size);
}
// The size of an entry in the PLT.
static const int plt_entry_size = 16;
// 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];
};
// Actually fill the PLT contents for an executable (non-PIC).
class Output_data_plt_i386_exec : public Output_data_plt_i386_standard
{
public:
Output_data_plt_i386_exec(Layout* layout,
Output_data_got_plt_i386* got_plt,
Output_data_space* got_irelative)
: Output_data_plt_i386_standard(layout, got_plt, got_irelative)
{ }
protected:
virtual void
do_fill_first_plt_entry(unsigned char* pov,
elfcpp::Elf_types<32>::Elf_Addr got_address);
virtual unsigned int
do_fill_plt_entry(unsigned char* pov,
elfcpp::Elf_types<32>::Elf_Addr got_address,
unsigned int got_offset,
unsigned int plt_offset,
unsigned int plt_rel_offset);
private:
// The first entry in the PLT for an executable.
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];
};
// Actually fill the PLT contents for a shared library (PIC).
class Output_data_plt_i386_dyn : public Output_data_plt_i386_standard
{
public:
Output_data_plt_i386_dyn(Layout* layout,
Output_data_got_plt_i386* got_plt,
Output_data_space* got_irelative)
: Output_data_plt_i386_standard(layout, got_plt, got_irelative)
{ }
protected:
virtual void
do_fill_first_plt_entry(unsigned char* pov, elfcpp::Elf_types<32>::Elf_Addr);
virtual unsigned int
do_fill_plt_entry(unsigned char* pov,
elfcpp::Elf_types<32>::Elf_Addr,
unsigned int got_offset,
unsigned int plt_offset,
unsigned int plt_rel_offset);
private:
// The first entry in the PLT for a shared object.
static const unsigned char first_plt_entry[plt_entry_size];
// Other entries in the PLT for a shared object.
static const unsigned char plt_entry[plt_entry_size];
};
// The i386 target class.
// TLS info comes from
// http://people.redhat.com/drepper/tls.pdf
// http://www.lsd.ic.unicamp.br/~oliva/writeups/TLS/RFC-TLSDESC-x86.txt
class Target_i386 : public Sized_target<32, false>
{
public:
typedef Output_data_reloc<elfcpp::SHT_REL, true, 32, false> Reloc_section;
Target_i386(const Target::Target_info* info = &i386_info)
: Sized_target<32, false>(info),
got_(NULL), plt_(NULL), got_plt_(NULL), got_irelative_(NULL),
got_tlsdesc_(NULL), global_offset_table_(NULL), rel_dyn_(NULL),
rel_irelative_(NULL), copy_relocs_(elfcpp::R_386_COPY),
got_mod_index_offset_(-1U), tls_base_symbol_defined_(false)
{ }
// Process the relocations to determine unreferenced sections for
// garbage collection.
void
gc_process_relocs(Symbol_table* symtab,
Layout* layout,
Sized_relobj_file<32, 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<32, 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<32, 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,
elfcpp::Elf_types<32>::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<32, 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<32, 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<32, false>*,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
Output_section* output_section,
elfcpp::Elf_types<32>::Elf_Off offset_in_output_section,
unsigned char* view,
elfcpp::Elf_types<32>::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 whether a symbol name implies a local label. The UnixWare
// 2.1 cc generates temporary symbols that start with .X, so we
// recognize them here. FIXME: do other SVR4 compilers also use .X?.
// If so, we should move the .X recognition into
// Target::do_is_local_label_name.
bool
do_is_local_label_name(const char* name) const
{
if (name[0] == '.' && name[1] == 'X')
return true;
return Target::do_is_local_label_name(name);
}
// Return the PLT address to use for a global symbol.
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); }
// We can tell whether we take the address of a function.
inline bool
do_can_check_for_function_pointers() const
{ return true; }
// Return the base for a DW_EH_PE_datarel encoding.
uint64_t
do_ehframe_datarel_base() const;
// Return whether SYM is call to a non-split function.
bool
do_is_call_to_non_split(const Symbol* sym, const unsigned char*,
const unsigned char*, section_size_type) 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() / 4;
}
// 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;
protected:
// Instantiate the plt_ member.
// This chooses the right PLT flavor for an executable or a shared object.
Output_data_plt_i386*
make_data_plt(Layout* layout,
Output_data_got_plt_i386* got_plt,
Output_data_space* got_irelative,
bool dyn)
{ return this->do_make_data_plt(layout, got_plt, got_irelative, dyn); }
virtual Output_data_plt_i386*
do_make_data_plt(Layout* layout,
Output_data_got_plt_i386* got_plt,
Output_data_space* got_irelative,
bool dyn)
{
if (dyn)
return new Output_data_plt_i386_dyn(layout, got_plt, got_irelative);
else
return new Output_data_plt_i386_exec(layout, got_plt, got_irelative);
}
private:
// The class which scans relocations.
struct Scan
{
static inline int
get_reference_flags(unsigned int r_type);
inline void
local(Symbol_table* symtab, Layout* layout, Target_i386* target,
Sized_relobj_file<32, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rel<32, false>& reloc, unsigned int r_type,
const elfcpp::Sym<32, false>& lsym,
bool is_discarded);
inline void
global(Symbol_table* symtab, Layout* layout, Target_i386* target,
Sized_relobj_file<32, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rel<32, false>& reloc, unsigned int r_type,
Symbol* gsym);
inline bool
local_reloc_may_be_function_pointer(Symbol_table* symtab, Layout* layout,
Target_i386* target,
Sized_relobj_file<32, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rel<32, false>& reloc,
unsigned int r_type,
const elfcpp::Sym<32, false>& lsym);
inline bool
global_reloc_may_be_function_pointer(Symbol_table* symtab, Layout* layout,
Target_i386* target,
Sized_relobj_file<32, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rel<32, false>& reloc,
unsigned int r_type,
Symbol* gsym);
inline bool
possible_function_pointer_reloc(unsigned int r_type);
bool
reloc_needs_plt_for_ifunc(Sized_relobj_file<32, false>*,
unsigned int r_type);
static void
unsupported_reloc_local(Sized_relobj_file<32, false>*, unsigned int r_type);
static void
unsupported_reloc_global(Sized_relobj_file<32, false>*, unsigned int r_type,
Symbol*);
};
// The class which implements relocation.
class Relocate
{
public:
Relocate()
: skip_call_tls_get_addr_(false),
local_dynamic_type_(LOCAL_DYNAMIC_NONE)
{ }
~Relocate()
{
if (this->skip_call_tls_get_addr_)
{
// FIXME: This needs to specify the location somehow.
gold_error(_("missing expected TLS relocation"));
}
}
// Return whether the static relocation needs to be applied.
inline bool
should_apply_static_reloc(const Sized_symbol<32>* gsym,
unsigned int r_type,
bool is_32bit,
Output_section* output_section);
// Do a relocation. Return false if the caller should not issue
// any warnings about this relocation.
inline bool
relocate(const Relocate_info<32, false>*, unsigned int,
Target_i386*, Output_section*, size_t, const unsigned char*,
const Sized_symbol<32>*, const Symbol_value<32>*,
unsigned char*, elfcpp::Elf_types<32>::Elf_Addr,
section_size_type);
private:
// Do a TLS relocation.
inline void
relocate_tls(const Relocate_info<32, false>*, Target_i386* target,
size_t relnum, const elfcpp::Rel<32, false>&,
unsigned int r_type, const Sized_symbol<32>*,
const Symbol_value<32>*,
unsigned char*, elfcpp::Elf_types<32>::Elf_Addr,
section_size_type);
// Do a TLS General-Dynamic to Initial-Exec transition.
inline void
tls_gd_to_ie(const Relocate_info<32, false>*, size_t relnum,
const elfcpp::Rel<32, false>&, unsigned int r_type,
elfcpp::Elf_types<32>::Elf_Addr value,
unsigned char* view,
section_size_type view_size);
// Do a TLS General-Dynamic to Local-Exec transition.
inline void
tls_gd_to_le(const Relocate_info<32, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rel<32, false>&, unsigned int r_type,
elfcpp::Elf_types<32>::Elf_Addr value,
unsigned char* view,
section_size_type view_size);
// Do a TLS_GOTDESC or TLS_DESC_CALL General-Dynamic to Initial-Exec
// transition.
inline void
tls_desc_gd_to_ie(const Relocate_info<32, false>*, size_t relnum,
const elfcpp::Rel<32, false>&, unsigned int r_type,
elfcpp::Elf_types<32>::Elf_Addr value,
unsigned char* view,
section_size_type view_size);
// Do a TLS_GOTDESC or TLS_DESC_CALL General-Dynamic to Local-Exec
// transition.
inline void
tls_desc_gd_to_le(const Relocate_info<32, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rel<32, false>&, unsigned int r_type,
elfcpp::Elf_types<32>::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<32, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rel<32, false>&, unsigned int r_type,
elfcpp::Elf_types<32>::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<32, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rel<32, false>&, unsigned int r_type,
elfcpp::Elf_types<32>::Elf_Addr value,
unsigned char* view,
section_size_type view_size);
// We need to keep track of which type of local dynamic relocation
// we have seen, so that we can optimize R_386_TLS_LDO_32 correctly.
enum Local_dynamic_type
{
LOCAL_DYNAMIC_NONE,
LOCAL_DYNAMIC_SUN,
LOCAL_DYNAMIC_GNU
};
// 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_;
// The type of local dynamic relocation we have seen in the section
// being relocated, if any.
Local_dynamic_type local_dynamic_type_;
};
// A class for inquiring about properties of a relocation,
// used while scanning relocs during a relocatable link and
// garbage collection.
class Classify_reloc :
public gold::Default_classify_reloc<elfcpp::SHT_REL, 32, false>
{
public:
typedef Reloc_types<elfcpp::SHT_REL, 32, false>::Reloc Reltype;
// Return the explicit addend of the relocation (return 0 for SHT_REL).
static elfcpp::Elf_types<32>::Elf_Swxword
get_r_addend(const Reltype*)
{ return 0; }
// Return the size of the addend of the relocation (only used for SHT_REL).
static unsigned int
get_size_for_reloc(unsigned int, Relobj*);
};
// 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);
// Check if relocation against this symbol is a candidate for
// conversion from
// mov foo@GOT(%reg), %reg
// to
// lea foo@GOTOFF(%reg), %reg.
static bool
can_convert_mov_to_lea(const Symbol* gsym)
{
gold_assert(gsym != NULL);
return (gsym->type() != elfcpp::STT_GNU_IFUNC
&& !gsym->is_undefined ()
&& !gsym->is_from_dynobj()
&& !gsym->is_preemptible()
&& (!parameters->options().shared()
|| (gsym->visibility() != elfcpp::STV_DEFAULT
&& gsym->visibility() != elfcpp::STV_PROTECTED)
|| parameters->options().Bsymbolic())
&& strcmp(gsym->name(), "_DYNAMIC") != 0);
}
// Get the GOT section, creating it if necessary.
Output_data_got<32, false>*
got_section(Symbol_table*, Layout*);
// Get the GOT PLT section.
Output_data_got_plt_i386*
got_plt_section() const
{
gold_assert(this->got_plt_ != NULL);
return this->got_plt_;
}
// Get the GOT section for TLSDESC entries.
Output_data_got<32, 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<32, 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 a GOT entry for the TLS module index.
unsigned int
got_mod_index_entry(Symbol_table* symtab, Layout* layout,
Sized_relobj_file<32, false>* object);
// Get the PLT section.
Output_data_plt_i386*
plt_section() const
{
gold_assert(this->plt_ != NULL);
return this->plt_;
}
// Get the dynamic reloc section, creating it if necessary.
Reloc_section*
rel_dyn_section(Layout*);
// Get the section to use for TLS_DESC relocations.
Reloc_section*
rel_tls_desc_section(Layout*) const;
// Get the section to use for IRELATIVE relocations.
Reloc_section*
rel_irelative_section(Layout*);
// Add a potential copy relocation.
void
copy_reloc(Symbol_table* symtab, Layout* layout,
Sized_relobj_file<32, false>* object,
unsigned int shndx, Output_section* output_section,
Symbol* sym, const elfcpp::Rel<32, false>& reloc)
{
unsigned int r_type = elfcpp::elf_r_type<32>(reloc.get_r_info());
this->copy_relocs_.copy_reloc(symtab, layout,
symtab->get_sized_symbol<32>(sym),
object, shndx, output_section,
r_type, reloc.get_r_offset(), 0,
this->rel_dyn_section(layout));
}
// Information about this specific target which we pass to the
// general Target structure.
static const Target::Target_info i386_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_NOFFSET = 1, // GOT entry for negative TLS offset
GOT_TYPE_TLS_OFFSET = 2, // GOT entry for positive TLS offset
GOT_TYPE_TLS_PAIR = 3, // GOT entry for TLS module/offset pair
GOT_TYPE_TLS_DESC = 4 // GOT entry for TLS_DESC pair
};
// The GOT section.
Output_data_got<32, false>* got_;
// The PLT section.
Output_data_plt_i386* plt_;
// The GOT PLT section.
Output_data_got_plt_i386* got_plt_;
// The GOT section for IRELATIVE relocations.
Output_data_space* got_irelative_;
// The GOT section for TLSDESC relocations.
Output_data_got<32, false>* got_tlsdesc_;
// The _GLOBAL_OFFSET_TABLE_ symbol.
Symbol* global_offset_table_;
// The dynamic reloc section.
Reloc_section* rel_dyn_;
// The section to use for IRELATIVE relocs.
Reloc_section* rel_irelative_;
// Relocs saved to avoid a COPY reloc.
Copy_relocs<elfcpp::SHT_REL, 32, false> copy_relocs_;
// Offset of the GOT entry for the TLS module index.
unsigned int got_mod_index_offset_;
// True if the _TLS_MODULE_BASE_ symbol has been defined.
bool tls_base_symbol_defined_;
};
const Target::Target_info Target_i386::i386_info =
{
32, // size
false, // is_big_endian
elfcpp::EM_386, // 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
"/usr/lib/libc.so.1", // dynamic_linker
0x08048000, // 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_UNDEF, // large_common_shndx
0, // small_common_section_flags
0, // large_common_section_flags
NULL, // attributes_section
NULL, // attributes_vendor
"_start", // entry_symbol_name
32, // hash_entry_size
};
// Get the GOT section, creating it if necessary.
Output_data_got<32, false>*
Target_i386::got_section(Symbol_table* symtab, Layout* layout)
{
if (this->got_ == NULL)
{
gold_assert(symtab != NULL && layout != NULL);
this->got_ = new Output_data_got<32, false>();
// 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);
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_i386(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 * 4);
if (!is_got_plt_relro)
{
// Those bytes can go into the relro segment.
layout->increase_relro(3 * 4);
}
// 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 relocations.
this->got_irelative_ = new Output_data_space(4, "** 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 entries.
this->got_tlsdesc_ = new Output_data_got<32, 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.
Target_i386::Reloc_section*
Target_i386::rel_dyn_section(Layout* layout)
{
if (this->rel_dyn_ == NULL)
{
gold_assert(layout != NULL);
this->rel_dyn_ = new Reloc_section(parameters->options().combreloc());
layout->add_output_section_data(".rel.dyn", elfcpp::SHT_REL,
elfcpp::SHF_ALLOC, this->rel_dyn_,
ORDER_DYNAMIC_RELOCS, false);
}
return this->rel_dyn_;
}
// Get the section to use for IRELATIVE relocs, creating it if
// necessary. These go in .rel.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.
Target_i386::Reloc_section*
Target_i386::rel_irelative_section(Layout* layout)
{
if (this->rel_irelative_ == NULL)
{
// Make sure we have already create the dynamic reloc section.
this->rel_dyn_section(layout);
this->rel_irelative_ = new Reloc_section(false);
layout->add_output_section_data(".rel.dyn", elfcpp::SHT_REL,
elfcpp::SHF_ALLOC, this->rel_irelative_,
ORDER_DYNAMIC_RELOCS, false);
gold_assert(this->rel_dyn_->output_section()
== this->rel_irelative_->output_section());
}
return this->rel_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_i386::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_i386::got_section.
const off_t got_file_offset = this->offset();
gold_assert(this->data_size() >= 12);
unsigned char* const got_view = of->get_output_view(got_file_offset, 12);
Output_section* dynamic = this->layout_->dynamic_section();
uint32_t dynamic_addr = dynamic == NULL ? 0 : dynamic->address();
elfcpp::Swap<32, false>::writeval(got_view, dynamic_addr);
memset(got_view + 4, 0, 8);
of->write_output_view(got_file_offset, 12, got_view);
}
// Create the PLT section. The ordinary .got section is an argument,
// since we need to refer to the start. We also create our own .got
// section just for PLT entries.
Output_data_plt_i386::Output_data_plt_i386(Layout* layout,
uint64_t addralign,
Output_data_got_plt_i386* got_plt,
Output_data_space* got_irelative)
: Output_section_data(addralign),
tls_desc_rel_(NULL), irelative_rel_(NULL), got_plt_(got_plt),
got_irelative_(got_irelative), count_(0), irelative_count_(0),
global_ifuncs_(), local_ifuncs_()
{
this->rel_ = new Reloc_section(false);
layout->add_output_section_data(".rel.plt", elfcpp::SHT_REL,
elfcpp::SHF_ALLOC, this->rel_,
ORDER_DYNAMIC_PLT_RELOCS, false);
}
void
Output_data_plt_i386::do_adjust_output_section(Output_section* os)
{
// UnixWare sets the entsize of .plt to 4, and so does the old GNU
// linker, and so do we.
os->set_entsize(4);
}
// Add an entry to the PLT.
void
Output_data_plt_i386::add_entry(Symbol_table* symtab, Layout* layout,
Symbol* gsym)
{
gold_assert(!gsym->has_plt_offset());
// Every PLT entry needs a reloc.
if (gsym->type() == elfcpp::STT_GNU_IFUNC
&& gsym->can_use_relative_reloc(false))
{
gsym->set_plt_offset(this->irelative_count_ * this->get_plt_entry_size());
++this->irelative_count_;
section_offset_type got_offset =
this->got_irelative_->current_data_size();
this->got_irelative_->set_current_data_size(got_offset + 4);
Reloc_section* rel = this->rel_irelative(symtab, layout);
rel->add_symbolless_global_addend(gsym, elfcpp::R_386_IRELATIVE,
this->got_irelative_, got_offset);
struct Global_ifunc gi;
gi.sym = gsym;
gi.got_offset = got_offset;
this->global_ifuncs_.push_back(gi);
}
else
{
// When setting the PLT offset we skip the initial reserved PLT
// entry.
gsym->set_plt_offset((this->count_ + 1) * this->get_plt_entry_size());
++this->count_;
section_offset_type got_offset = this->got_plt_->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).
this->got_plt_->set_current_data_size(got_offset + 4);
gsym->set_needs_dynsym_entry();
this->rel_->add_global(gsym, elfcpp::R_386_JUMP_SLOT, this->got_plt_,
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.
unsigned int
Output_data_plt_i386::add_local_ifunc_entry(
Symbol_table* symtab,
Layout* layout,
Sized_relobj_file<32, 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 + 4);
// Every PLT entry needs a reloc.
Reloc_section* rel = this->rel_irelative(symtab, layout);
rel->add_symbolless_local_addend(relobj, local_sym_index,
elfcpp::R_386_IRELATIVE,
this->got_irelative_, got_offset);
struct Local_ifunc li;
li.object = relobj;
li.local_sym_index = local_sym_index;
li.got_offset = got_offset;
this->local_ifuncs_.push_back(li);
return plt_offset;
}
// Return where the TLS_DESC relocations should go, creating it if
// necessary. These follow the JUMP_SLOT relocations.
Output_data_plt_i386::Reloc_section*
Output_data_plt_i386::rel_tls_desc(Layout* layout)
{
if (this->tls_desc_rel_ == NULL)
{
this->tls_desc_rel_ = new Reloc_section(false);
layout->add_output_section_data(".rel.plt", elfcpp::SHT_REL,
elfcpp::SHF_ALLOC, this->tls_desc_rel_,
ORDER_DYNAMIC_PLT_RELOCS, false);
gold_assert(this->tls_desc_rel_->output_section()
== this->rel_->output_section());
}
return this->tls_desc_rel_;
}
// Return where the IRELATIVE relocations should go in the PLT. These
// follow the JUMP_SLOT and TLS_DESC relocations.
Output_data_plt_i386::Reloc_section*
Output_data_plt_i386::rel_irelative(Symbol_table* symtab, Layout* layout)
{
if (this->irelative_rel_ == NULL)
{
// Make sure we have a place for the TLS_DESC relocations, in
// case we see any later on.
this->rel_tls_desc(layout);
this->irelative_rel_ = new Reloc_section(false);
layout->add_output_section_data(".rel.plt", elfcpp::SHT_REL,
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 .rel.plt
// section to hold R_386_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("__rel_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("__rel_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.
uint64_t
Output_data_plt_i386::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.
uint64_t
Output_data_plt_i386::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));
}
// The first entry in the PLT for an executable.
const unsigned char Output_data_plt_i386_exec::first_plt_entry[plt_entry_size] =
{
0xff, 0x35, // pushl contents of memory address
0, 0, 0, 0, // replaced with address of .got + 4
0xff, 0x25, // jmp indirect
0, 0, 0, 0, // replaced with address of .got + 8
0, 0, 0, 0 // unused
};
void
Output_data_plt_i386_exec::do_fill_first_plt_entry(
unsigned char* pov,
elfcpp::Elf_types<32>::Elf_Addr got_address)
{
memcpy(pov, first_plt_entry, plt_entry_size);
elfcpp::Swap_unaligned<32, false>::writeval(pov + 2, got_address + 4);
elfcpp::Swap<32, false>::writeval(pov + 8, got_address + 8);
}
// The first entry in the PLT for a shared object.
const unsigned char Output_data_plt_i386_dyn::first_plt_entry[plt_entry_size] =
{
0xff, 0xb3, 4, 0, 0, 0, // pushl 4(%ebx)
0xff, 0xa3, 8, 0, 0, 0, // jmp *8(%ebx)
0, 0, 0, 0 // unused
};
void
Output_data_plt_i386_dyn::do_fill_first_plt_entry(
unsigned char* pov,
elfcpp::Elf_types<32>::Elf_Addr)
{
memcpy(pov, first_plt_entry, plt_entry_size);
}
// Subsequent entries in the PLT for an executable.
const unsigned char Output_data_plt_i386_exec::plt_entry[plt_entry_size] =
{
0xff, 0x25, // jmp indirect
0, 0, 0, 0, // replaced with address of symbol in .got
0x68, // pushl immediate
0, 0, 0, 0, // replaced with offset into relocation table
0xe9, // jmp relative
0, 0, 0, 0 // replaced with offset to start of .plt
};
unsigned int
Output_data_plt_i386_exec::do_fill_plt_entry(
unsigned char* pov,
elfcpp::Elf_types<32>::Elf_Addr got_address,
unsigned int got_offset,
unsigned int plt_offset,
unsigned int plt_rel_offset)
{
memcpy(pov, plt_entry, plt_entry_size);
elfcpp::Swap_unaligned<32, false>::writeval(pov + 2,
got_address + got_offset);
elfcpp::Swap_unaligned<32, false>::writeval(pov + 7, plt_rel_offset);
elfcpp::Swap<32, false>::writeval(pov + 12, - (plt_offset + 12 + 4));
return 6;
}
// Subsequent entries in the PLT for a shared object.
const unsigned char Output_data_plt_i386_dyn::plt_entry[plt_entry_size] =
{
0xff, 0xa3, // jmp *offset(%ebx)
0, 0, 0, 0, // replaced with offset of symbol in .got
0x68, // pushl immediate
0, 0, 0, 0, // replaced with offset into relocation table
0xe9, // jmp relative
0, 0, 0, 0 // replaced with offset to start of .plt
};
unsigned int
Output_data_plt_i386_dyn::do_fill_plt_entry(unsigned char* pov,
elfcpp::Elf_types<32>::Elf_Addr,
unsigned int got_offset,
unsigned int plt_offset,
unsigned int plt_rel_offset)
{
memcpy(pov, plt_entry, plt_entry_size);
elfcpp::Swap_unaligned<32, false>::writeval(pov + 2, got_offset);
elfcpp::Swap_unaligned<32, false>::writeval(pov + 7, plt_rel_offset);
elfcpp::Swap<32, false>::writeval(pov + 12, - (plt_offset + 12 + 4));
return 6;
}
// The .eh_frame unwind information for the PLT.
const unsigned char
Output_data_plt_i386::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.
0x7c, // Data alignment factor.
8, // Return address column.
1, // Augmentation size.
(elfcpp::DW_EH_PE_pcrel // FDE encoding.
| elfcpp::DW_EH_PE_sdata4),
elfcpp::DW_CFA_def_cfa, 4, 4, // DW_CFA_def_cfa: r4 (esp) ofs 4.
elfcpp::DW_CFA_offset + 8, 1, // DW_CFA_offset: r8 (eip) at cfa-4.
elfcpp::DW_CFA_nop, // Align to 16 bytes.
elfcpp::DW_CFA_nop
};
const unsigned char
Output_data_plt_i386_standard::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, 8, // DW_CFA_def_cfa_offset: 8.
elfcpp::DW_CFA_advance_loc + 6, // Advance 6 to __PLT__ + 6.
elfcpp::DW_CFA_def_cfa_offset, 12, // DW_CFA_def_cfa_offset: 12.
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_breg4, 4, // Push %esp + 4.
elfcpp::DW_OP_breg8, 0, // Push %eip.
elfcpp::DW_OP_lit15, // Push 0xf.
elfcpp::DW_OP_and, // & (%eip & 0xf).
elfcpp::DW_OP_lit11, // Push 0xb.
elfcpp::DW_OP_ge, // >= ((%eip & 0xf) >= 0xb)
elfcpp::DW_OP_lit2, // Push 2.
elfcpp::DW_OP_shl, // << (((%eip & 0xf) >= 0xb) << 2)
elfcpp::DW_OP_plus, // + ((((%eip&0xf)>=0xb)<<2)+%esp+4
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 all specified by the i386 ELF
// Processor Supplement.
void
Output_data_plt_i386::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;
elfcpp::Elf_types<32>::Elf_Addr plt_address = this->address();
elfcpp::Elf_types<32>::Elf_Addr got_address = this->got_plt_->address();
this->fill_first_plt_entry(pov, got_address);
pov += this->get_plt_entry_size();
// The first three entries in the GOT are reserved, and are written
// by Output_data_got_plt_i386::do_write.
unsigned char* got_pov = got_view + 12;
const int rel_size = elfcpp::Elf_sizes<32>::rel_size;
unsigned int plt_offset = this->get_plt_entry_size();
unsigned int plt_rel_offset = 0;
unsigned int got_offset = 12;
const unsigned int count = this->count_ + this->irelative_count_;
for (unsigned int i = 0;
i < count;
++i,
pov += this->get_plt_entry_size(),
got_pov += 4,
plt_offset += this->get_plt_entry_size(),
plt_rel_offset += rel_size,
got_offset += 4)
{
// Set and adjust the PLT entry itself.
unsigned int lazy_offset = this->fill_plt_entry(pov,
got_address,
got_offset,
plt_offset,
plt_rel_offset);
// Set the entry in the GOT.
elfcpp::Swap<32, false>::writeval(got_pov,
plt_address + plt_offset + lazy_offset);
}
// If any STT_GNU_IFUNC symbols have PLT entries, we need to change
// the GOT to point to the actual symbol value, rather than point to
// the PLT entry. That will let the dynamic linker call the right
// function when resolving IRELATIVE relocations.
unsigned char* got_irelative_view = got_view + this->got_plt_->data_size();
for (std::vector<Global_ifunc>::const_iterator p =
this->global_ifuncs_.begin();
p != this->global_ifuncs_.end();
++p)
{
const Sized_symbol<32>* ssym =
static_cast<const Sized_symbol<32>*>(p->sym);
elfcpp::Swap<32, false>::writeval(got_irelative_view + p->got_offset,
ssym->value());
}
for (std::vector<Local_ifunc>::const_iterator p =
this->local_ifuncs_.begin();
p != this->local_ifuncs_.end();
++p)
{
const Symbol_value<32>* psymval =
p->object->local_symbol(p->local_sym_index);
elfcpp::Swap<32, false>::writeval(got_irelative_view + p->got_offset,
psymval->value(p->object, 0));
}
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.
void
Target_i386::make_plt_section(Symbol_table* symtab, Layout* layout)
{
if (this->plt_ == NULL)
{
// Create the GOT sections first.
this->got_section(symtab, layout);
const bool dyn = parameters->options().output_is_position_independent();
this->plt_ = this->make_data_plt(layout,
this->got_plt_,
this->got_irelative_,
dyn);
// 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 .rel.plt point to .plt.
Output_section* rel_plt_os = this->plt_->rel_plt()->output_section();
rel_plt_os->set_info_section(this->plt_->output_section());
}
}
// Create a PLT entry for a global symbol.
void
Target_i386::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.
void
Target_i386::make_local_ifunc_plt_entry(Symbol_table* symtab, Layout* layout,
Sized_relobj_file<32, 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.
unsigned int
Target_i386::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.
unsigned int
Target_i386::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.
unsigned int
Target_i386::plt_entry_size() const
{
if (this->plt_ == NULL)
return 0;
return this->plt_->get_plt_entry_size();
}
// Get the section to use for TLS_DESC relocations.
Target_i386::Reloc_section*
Target_i386::rel_tls_desc_section(Layout* layout) const
{
return this->plt_section()->rel_tls_desc(layout);
}
// Define the _TLS_MODULE_BASE_ symbol in the TLS segment.
void
Target_i386::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 a GOT entry for the TLS module index.
unsigned int
Target_i386::got_mod_index_entry(Symbol_table* symtab, Layout* layout,
Sized_relobj_file<32, false>* object)
{
if (this->got_mod_index_offset_ == -1U)
{
gold_assert(symtab != NULL && layout != NULL && object != NULL);
Reloc_section* rel_dyn = this->rel_dyn_section(layout);
Output_data_got<32, false>* got = this->got_section(symtab, layout);
unsigned int got_offset = got->add_constant(0);
rel_dyn->add_local(object, 0, elfcpp::R_386_TLS_DTPMOD32, got,
got_offset);
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.
tls::Tls_optimization
Target_i386::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_386_TLS_GD:
case elfcpp::R_386_TLS_GOTDESC:
case elfcpp::R_386_TLS_DESC_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_386_TLS_LDM:
// 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_386_TLS_LDO_32:
// Another type of Local-Dynamic relocation.
return tls::TLSOPT_TO_LE;
case elfcpp::R_386_TLS_IE:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_IE_32:
// 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_386_TLS_LE:
case elfcpp::R_386_TLS_LE_32:
// 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.
int
Target_i386::Scan::get_reference_flags(unsigned int r_type)
{
switch (r_type)
{
case elfcpp::R_386_NONE:
case elfcpp::R_386_GNU_VTINHERIT:
case elfcpp::R_386_GNU_VTENTRY:
case elfcpp::R_386_GOTPC:
// No symbol reference.
return 0;
case elfcpp::R_386_32:
case elfcpp::R_386_16:
case elfcpp::R_386_8:
return Symbol::ABSOLUTE_REF;
case elfcpp::R_386_PC32:
case elfcpp::R_386_PC16:
case elfcpp::R_386_PC8:
case elfcpp::R_386_GOTOFF:
return Symbol::RELATIVE_REF;
case elfcpp::R_386_PLT32:
return Symbol::FUNCTION_CALL | Symbol::RELATIVE_REF;
case elfcpp::R_386_GOT32:
case elfcpp::R_386_GOT32X:
// Absolute in GOT.
return Symbol::ABSOLUTE_REF;
case elfcpp::R_386_TLS_GD: // Global-dynamic
case elfcpp::R_386_TLS_GOTDESC: // Global-dynamic (from ~oliva url)
case elfcpp::R_386_TLS_DESC_CALL:
case elfcpp::R_386_TLS_LDM: // Local-dynamic
case elfcpp::R_386_TLS_LDO_32: // Alternate local-dynamic
case elfcpp::R_386_TLS_IE: // Initial-exec
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_LE: // Local-exec
case elfcpp::R_386_TLS_LE_32:
return Symbol::TLS_REF;
case elfcpp::R_386_COPY:
case elfcpp::R_386_GLOB_DAT:
case elfcpp::R_386_JUMP_SLOT:
case elfcpp::R_386_RELATIVE:
case elfcpp::R_386_IRELATIVE:
case elfcpp::R_386_TLS_TPOFF:
case elfcpp::R_386_TLS_DTPMOD32:
case elfcpp::R_386_TLS_DTPOFF32:
case elfcpp::R_386_TLS_TPOFF32:
case elfcpp::R_386_TLS_DESC:
case elfcpp::R_386_32PLT:
case elfcpp::R_386_TLS_GD_32:
case elfcpp::R_386_TLS_GD_PUSH:
case elfcpp::R_386_TLS_GD_CALL:
case elfcpp::R_386_TLS_GD_POP:
case elfcpp::R_386_TLS_LDM_32:
case elfcpp::R_386_TLS_LDM_PUSH:
case elfcpp::R_386_TLS_LDM_CALL:
case elfcpp::R_386_TLS_LDM_POP:
case elfcpp::R_386_USED_BY_INTEL_200:
default:
// Not expected. We will give an error later.
return 0;
}
}
// Report an unsupported relocation against a local symbol.
void
Target_i386::Scan::unsupported_reloc_local(Sized_relobj_file<32, false>* object,
unsigned int r_type)
{
gold_error(_("%s: unsupported reloc %u against local symbol"),
object->name().c_str(), r_type);
}
// Return whether we need to make a PLT entry for a relocation of a
// given type against a STT_GNU_IFUNC symbol.
bool
Target_i386::Scan::reloc_needs_plt_for_ifunc(
Sized_relobj_file<32, 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.
inline void
Target_i386::Scan::local(Symbol_table* symtab,
Layout* layout,
Target_i386* target,
Sized_relobj_file<32, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rel<32, false>& reloc,
unsigned int r_type,
const elfcpp::Sym<32, false>& lsym,
bool is_discarded)
{
if (is_discarded)
return;
// A local STT_GNU_IFUNC symbol may require a PLT entry.
if (lsym.get_st_type() == elfcpp::STT_GNU_IFUNC
&& this->reloc_needs_plt_for_ifunc(object, r_type))
{
unsigned int r_sym = elfcpp::elf_r_sym<32>(reloc.get_r_info());
target->make_local_ifunc_plt_entry(symtab, layout, object, r_sym);
}
switch (r_type)
{
case elfcpp::R_386_NONE:
case elfcpp::R_386_GNU_VTINHERIT:
case elfcpp::R_386_GNU_VTENTRY:
break;
case elfcpp::R_386_32:
// 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_386_RELATIVE relocation so the dynamic loader can
// relocate it easily.
if (parameters->options().output_is_position_independent())
{
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
unsigned int r_sym = elfcpp::elf_r_sym<32>(reloc.get_r_info());
rel_dyn->add_local_relative(object, r_sym, elfcpp::R_386_RELATIVE,
output_section, data_shndx,
reloc.get_r_offset());
}
break;
case elfcpp::R_386_16:
case elfcpp::R_386_8:
// If building a shared library (or a position-independent
// executable), we need to create a dynamic relocation for
// this location. Because the addend needs to remain in the
// data section, we need to be careful not to apply this
// relocation statically.
if (parameters->options().output_is_position_independent())
{
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
unsigned int r_sym = elfcpp::elf_r_sym<32>(reloc.get_r_info());
if (lsym.get_st_type() != elfcpp::STT_SECTION)
rel_dyn->add_local(object, r_sym, r_type, output_section,
data_shndx, reloc.get_r_offset());
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
rel_dyn->add_local_section(object, shndx,
r_type, output_section,
data_shndx, reloc.get_r_offset());
}
}
break;
case elfcpp::R_386_PC32:
case elfcpp::R_386_PC16:
case elfcpp::R_386_PC8:
break;
case elfcpp::R_386_PLT32:
// Since we know this is a local symbol, we can handle this as a
// PC32 reloc.
break;
case elfcpp::R_386_GOTOFF:
case elfcpp::R_386_GOTPC:
// We need a GOT section.
target->got_section(symtab, layout);
break;
case elfcpp::R_386_GOT32:
case elfcpp::R_386_GOT32X:
{
// We need GOT section.
Output_data_got<32, false>* got = target->got_section(symtab, layout);
// If the relocation symbol isn't IFUNC,
// and is local, then we will convert
// mov foo@GOT(%reg), %reg
// to
// lea foo@GOTOFF(%reg), %reg
// in Relocate::relocate.
if (reloc.get_r_offset() >= 2
&& lsym.get_st_type() != elfcpp::STT_GNU_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;
}
// Otherwise, the symbol requires a GOT entry.
unsigned int r_sym = elfcpp::elf_r_sym<32>(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 (lsym.get_st_type() == elfcpp::STT_GNU_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 RELATIVE relocation for this symbol's GOT entry.
if (parameters->options().output_is_position_independent())
{
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
unsigned int got_offset =
object->local_got_offset(r_sym, GOT_TYPE_STANDARD);
rel_dyn->add_local_relative(object, r_sym,
elfcpp::R_386_RELATIVE,
got, got_offset);
}
}
}
break;
// These are relocations which should only be seen by the
// dynamic linker, and should never be seen here.
case elfcpp::R_386_COPY:
case elfcpp::R_386_GLOB_DAT:
case elfcpp::R_386_JUMP_SLOT:
case elfcpp::R_386_RELATIVE:
case elfcpp::R_386_IRELATIVE:
case elfcpp::R_386_TLS_TPOFF:
case elfcpp::R_386_TLS_DTPMOD32:
case elfcpp::R_386_TLS_DTPOFF32:
case elfcpp::R_386_TLS_TPOFF32:
case elfcpp::R_386_TLS_DESC:
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_386_TLS_GD: // Global-dynamic
case elfcpp::R_386_TLS_GOTDESC: // Global-dynamic (from ~oliva url)
case elfcpp::R_386_TLS_DESC_CALL:
case elfcpp::R_386_TLS_LDM: // Local-dynamic
case elfcpp::R_386_TLS_LDO_32: // Alternate local-dynamic
case elfcpp::R_386_TLS_IE: // Initial-exec
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_LE: // Local-exec
case elfcpp::R_386_TLS_LE_32:
{
bool output_is_shared = parameters->options().shared();
const tls::Tls_optimization optimized_type
= Target_i386::optimize_tls_reloc(!output_is_shared, r_type);
switch (r_type)
{
case elfcpp::R_386_TLS_GD: // Global-dynamic
if (optimized_type == tls::TLSOPT_NONE)
{
// Create a pair of GOT entries for the module index and
// dtv-relative offset.
Output_data_got<32, false>* got
= target->got_section(symtab, layout);
unsigned int r_sym = elfcpp::elf_r_sym<32>(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->rel_dyn_section(layout),
elfcpp::R_386_TLS_DTPMOD32);
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_local(object, r_type);
break;
case elfcpp::R_386_TLS_GOTDESC: // Global-dynamic (from ~oliva)
target->define_tls_base_symbol(symtab, layout);
if (optimized_type == tls::TLSOPT_NONE)
{
// Create a double GOT entry with an R_386_TLS_DESC
// reloc. The R_386_TLS_DESC 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<32, false>* got = target->got_tlsdesc_section();
unsigned int r_sym = elfcpp::elf_r_sym<32>(reloc.get_r_info());
if (!object->local_has_got_offset(r_sym, GOT_TYPE_TLS_DESC))
{
unsigned int got_offset = got->add_constant(0);
// The local symbol value is stored in the second
// GOT entry.
got->add_local(object, r_sym, GOT_TYPE_TLS_DESC);
// That set the GOT offset of the local symbol to
// point to the second entry, but we want it to
// point to the first.
object->set_local_got_offset(r_sym, GOT_TYPE_TLS_DESC,
got_offset);
Reloc_section* rt = target->rel_tls_desc_section(layout);
rt->add_absolute(elfcpp::R_386_TLS_DESC, got, got_offset);
}
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_local(object, r_type);
break;
case elfcpp::R_386_TLS_DESC_CALL:
break;
case elfcpp::R_386_TLS_LDM: // Local-dynamic
if (optimized_type == tls::TLSOPT_NONE)
{
// Create a GOT entry for the module index.
target->got_mod_index_entry(symtab, layout, object);
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_local(object, r_type);
break;
case elfcpp::R_386_TLS_LDO_32: // Alternate local-dynamic
break;
case elfcpp::R_386_TLS_IE: // Initial-exec
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_GOTIE:
layout->set_has_static_tls();
if (optimized_type == tls::TLSOPT_NONE)
{
// For the R_386_TLS_IE relocation, we need to create a
// dynamic relocation when building a shared library.
if (r_type == elfcpp::R_386_TLS_IE
&& parameters->options().shared())
{
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
unsigned int r_sym
= elfcpp::elf_r_sym<32>(reloc.get_r_info());
rel_dyn->add_local_relative(object, r_sym,
elfcpp::R_386_RELATIVE,
output_section, data_shndx,
reloc.get_r_offset());
}
// Create a GOT entry for the tp-relative offset.
Output_data_got<32, false>* got
= target->got_section(symtab, layout);
unsigned int r_sym = elfcpp::elf_r_sym<32>(reloc.get_r_info());
unsigned int dyn_r_type = (r_type == elfcpp::R_386_TLS_IE_32
? elfcpp::R_386_TLS_TPOFF32
: elfcpp::R_386_TLS_TPOFF);
unsigned int got_type = (r_type == elfcpp::R_386_TLS_IE_32
? GOT_TYPE_TLS_OFFSET
: GOT_TYPE_TLS_NOFFSET);
got->add_local_with_rel(object, r_sym, got_type,
target->rel_dyn_section(layout),
dyn_r_type);
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_local(object, r_type);
break;
case elfcpp::R_386_TLS_LE: // Local-exec
case elfcpp::R_386_TLS_LE_32:
layout->set_has_static_tls();
if (output_is_shared)
{
// We need to create a dynamic relocation.
gold_assert(lsym.get_st_type() != elfcpp::STT_SECTION);
unsigned int r_sym = elfcpp::elf_r_sym<32>(reloc.get_r_info());
unsigned int dyn_r_type = (r_type == elfcpp::R_386_TLS_LE_32
? elfcpp::R_386_TLS_TPOFF32
: elfcpp::R_386_TLS_TPOFF);
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
rel_dyn->add_local(object, r_sym, dyn_r_type, output_section,
data_shndx, reloc.get_r_offset());
}
break;
default:
gold_unreachable();
}
}
break;
case elfcpp::R_386_32PLT:
case elfcpp::R_386_TLS_GD_32:
case elfcpp::R_386_TLS_GD_PUSH:
case elfcpp::R_386_TLS_GD_CALL:
case elfcpp::R_386_TLS_GD_POP:
case elfcpp::R_386_TLS_LDM_32:
case elfcpp::R_386_TLS_LDM_PUSH:
case elfcpp::R_386_TLS_LDM_CALL:
case elfcpp::R_386_TLS_LDM_POP:
case elfcpp::R_386_USED_BY_INTEL_200:
default:
unsupported_reloc_local(object, r_type);
break;
}
}
// Report an unsupported relocation against a global symbol.
void
Target_i386::Scan::unsupported_reloc_global(
Sized_relobj_file<32, false>* object,
unsigned int r_type,
Symbol* gsym)
{
gold_error(_("%s: unsupported reloc %u against global symbol %s"),
object->name().c_str(), r_type, gsym->demangled_name().c_str());
}
inline bool
Target_i386::Scan::possible_function_pointer_reloc(unsigned int r_type)
{
switch (r_type)
{
case elfcpp::R_386_32:
case elfcpp::R_386_16:
case elfcpp::R_386_8:
case elfcpp::R_386_GOTOFF:
case elfcpp::R_386_GOT32:
case elfcpp::R_386_GOT32X:
{
return true;
}
default:
return false;
}
return false;
}
inline bool
Target_i386::Scan::local_reloc_may_be_function_pointer(
Symbol_table* ,
Layout* ,
Target_i386* ,
Sized_relobj_file<32, false>* ,
unsigned int ,
Output_section* ,
const elfcpp::Rel<32, false>& ,
unsigned int r_type,
const elfcpp::Sym<32, false>&)
{
return possible_function_pointer_reloc(r_type);
}
inline bool
Target_i386::Scan::global_reloc_may_be_function_pointer(
Symbol_table* ,
Layout* ,
Target_i386* ,
Sized_relobj_file<32, false>* ,
unsigned int ,
Output_section* ,
const elfcpp::Rel<32, false>& ,
unsigned int r_type,
Symbol*)
{
return possible_function_pointer_reloc(r_type);
}
// Scan a relocation for a global symbol.
inline void
Target_i386::Scan::global(Symbol_table* symtab,
Layout* layout,
Target_i386* target,
Sized_relobj_file<32, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rel<32, false>& reloc,
unsigned int r_type,
Symbol* gsym)
{
// A STT_GNU_IFUNC symbol may require a PLT entry.
if (gsym->type() == elfcpp::STT_GNU_IFUNC
&& this->reloc_needs_plt_for_ifunc(object, r_type))
target->make_plt_entry(symtab, layout, gsym);
switch (r_type)
{
case elfcpp::R_386_NONE:
case elfcpp::R_386_GNU_VTINHERIT:
case elfcpp::R_386_GNU_VTENTRY:
break;
case elfcpp::R_386_32:
case elfcpp::R_386_16:
case elfcpp::R_386_8:
{
// Make a PLT entry if necessary.
if (gsym->needs_plt_entry())
{
target->make_plt_entry(symtab, layout, gsym);
// Since this is not a PC-relative relocation, we may be
// taking the address of a function. In that case we need to
// set the entry in the dynamic symbol table to the address of
// the PLT entry.
if (gsym->is_from_dynobj() && !parameters->options().shared())
gsym->set_needs_dynsym_value();
}
// Make a dynamic relocation if necessary.
if (gsym->needs_dynamic_reloc(Scan::get_reference_flags(r_type)))
{
if (!parameters->options().output_is_position_independent()
&& gsym->may_need_copy_reloc())
{
target->copy_reloc(symtab, layout, object,
data_shndx, output_section, gsym, reloc);
}
else if (r_type == elfcpp::R_386_32
&& gsym->type() == elfcpp::STT_GNU_IFUNC
&& gsym->can_use_relative_reloc(false)
&& !gsym->is_from_dynobj()
&& !gsym->is_undefined()
&& !gsym->is_preemptible())
{
// Use an IRELATIVE reloc for a locally defined
// STT_GNU_IFUNC symbol. This makes a function
// address in a PIE executable match the address in a
// shared library that it links against.
Reloc_section* rel_dyn = target->rel_irelative_section(layout);
rel_dyn->add_symbolless_global_addend(gsym,
elfcpp::R_386_IRELATIVE,
output_section,
object, data_shndx,
reloc.get_r_offset());
}
else if (r_type == elfcpp::R_386_32
&& gsym->can_use_relative_reloc(false))
{
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
rel_dyn->add_global_relative(gsym, elfcpp::R_386_RELATIVE,
output_section, object,
data_shndx, reloc.get_r_offset());
}
else
{
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
rel_dyn->add_global(gsym, r_type, output_section, object,
data_shndx, reloc.get_r_offset());
}
}
}
break;
case elfcpp::R_386_PC32:
case elfcpp::R_386_PC16:
case elfcpp::R_386_PC8:
{
// Make a PLT entry if necessary.
if (gsym->needs_plt_entry())
{
// These relocations are used for function calls only in
// non-PIC code. For a 32-bit relocation in a shared library,
// we'll need a text relocation anyway, so we can skip the
// PLT entry and let the dynamic linker bind the call directly
// to the target. For smaller relocations, we should use a
// PLT entry to ensure that the call can reach.
if (!parameters->options().shared()
|| r_type != elfcpp::R_386_PC32)
target->make_plt_entry(symtab, layout, gsym);
}
// Make a dynamic relocation if necessary.
if (gsym->needs_dynamic_reloc(Scan::get_reference_flags(r_type)))
{
if (parameters->options().output_is_executable()
&& gsym->may_need_copy_reloc())
{
target->copy_reloc(symtab, layout, object,
data_shndx, output_section, gsym, reloc);
}
else
{
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
rel_dyn->add_global(gsym, r_type, output_section, object,
data_shndx, reloc.get_r_offset());
}
}
}
break;
case elfcpp::R_386_GOT32:
case elfcpp::R_386_GOT32X:
{
// The symbol requires a GOT section.
Output_data_got<32, false>* got = target->got_section(symtab, layout);
// If we convert this from
// mov foo@GOT(%reg), %reg
// to
// lea foo@GOTOFF(%reg), %reg
// in Relocate::relocate, then there is nothing to do here.
if (reloc.get_r_offset() >= 2
&& Target_i386::can_convert_mov_to_lea(gsym))
{
section_size_type stype;
const unsigned char* view = object->section_contents(data_shndx,
&stype, true);
if (view[reloc.get_r_offset() - 2] == 0x8b)
break;
}
if (gsym->final_value_is_known())
{
// For a STT_GNU_IFUNC symbol we want the PLT address.
if (gsym->type() == elfcpp::STT_GNU_IFUNC)
got->add_global_plt(gsym, GOT_TYPE_STANDARD);
else
got->add_global(gsym, GOT_TYPE_STANDARD);
}
else
{
// If this symbol is not fully resolved, we need to add a
// GOT entry with a dynamic relocation.
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
// Use a GLOB_DAT rather than a RELATIVE reloc if:
//
// 1) The symbol may be defined in some other module.
//
// 2) We are building a shared library and this is a
// protected symbol; using GLOB_DAT means that the dynamic
// linker can use the address of the PLT in the main
// executable when appropriate so that function address
// comparisons work.
//
// 3) This is a STT_GNU_IFUNC symbol in position dependent
// code, again so that function address comparisons work.
if (gsym->is_from_dynobj()
|| gsym->is_undefined()
|| gsym->is_preemptible()
|| (gsym->visibility() == elfcpp::STV_PROTECTED
&& parameters->options().shared())
|| (gsym->type() == elfcpp::STT_GNU_IFUNC
&& parameters->options().output_is_position_independent()))
got->add_global_with_rel(gsym, GOT_TYPE_STANDARD,
rel_dyn, elfcpp::R_386_GLOB_DAT);
else
{
// For a STT_GNU_IFUNC symbol we want to write the PLT
// offset into the GOT, so that function pointer
// comparisons work correctly.
bool is_new;
if (gsym->type() != elfcpp::STT_GNU_IFUNC)
is_new = got->add_global(gsym, GOT_TYPE_STANDARD);
else
{
is_new = got->add_global_plt(gsym, GOT_TYPE_STANDARD);
// Tell the dynamic linker to use the PLT address
// when resolving relocations.
if (gsym->is_from_dynobj()
&& !parameters->options().shared())
gsym->set_needs_dynsym_value();
}
if (is_new)
{
unsigned int got_off = gsym->got_offset(GOT_TYPE_STANDARD);
rel_dyn->add_global_relative(gsym, elfcpp::R_386_RELATIVE,
got, got_off);
}
}
}
}
break;
case elfcpp::R_386_PLT32:
// If the symbol is fully resolved, this is just a PC32 reloc.
// Otherwise we need a PLT entry.
if (gsym->final_value_is_known())
break;
// If building a shared library, we can also skip the PLT entry
// if the symbol is defined in the output file and is protected
// or hidden.
if (gsym->is_defined()
&& !gsym->is_from_dynobj()
&& !gsym->is_preemptible())
break;
target->make_plt_entry(symtab, layout, gsym);
break;
case elfcpp::R_386_GOTOFF:
// A GOT-relative reference must resolve locally.
if (!gsym->is_defined())
gold_error(_("%s: relocation R_386_GOTOFF against undefined symbol %s"
" cannot be used when making a shared object"),
object->name().c_str(), gsym->name());
else if (gsym->is_from_dynobj())
gold_error(_("%s: relocation R_386_GOTOFF against external symbol %s"
" cannot be used when making a shared object"),
object->name().c_str(), gsym->name());
else if (gsym->is_preemptible())
gold_error(_("%s: relocation R_386_GOTOFF against preemptible symbol %s"
" cannot be used when making a shared object"),
object->name().c_str(), gsym->name());
// We need a GOT section.
target->got_section(symtab, layout);
break;
case elfcpp::R_386_GOTPC:
// We need a GOT section.
target->got_section(symtab, layout);
break;
// These are relocations which should only be seen by the
// dynamic linker, and should never be seen here.
case elfcpp::R_386_COPY:
case elfcpp::R_386_GLOB_DAT:
case elfcpp::R_386_JUMP_SLOT:
case elfcpp::R_386_RELATIVE:
case elfcpp::R_386_IRELATIVE:
case elfcpp::R_386_TLS_TPOFF:
case elfcpp::R_386_TLS_DTPMOD32:
case elfcpp::R_386_TLS_DTPOFF32:
case elfcpp::R_386_TLS_TPOFF32:
case elfcpp::R_386_TLS_DESC:
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_386_TLS_GD: // Global-dynamic
case elfcpp::R_386_TLS_GOTDESC: // Global-dynamic (from ~oliva url)
case elfcpp::R_386_TLS_DESC_CALL:
case elfcpp::R_386_TLS_LDM: // Local-dynamic
case elfcpp::R_386_TLS_LDO_32: // Alternate local-dynamic
case elfcpp::R_386_TLS_IE: // Initial-exec
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_LE: // Local-exec
case elfcpp::R_386_TLS_LE_32:
{
const bool is_final = gsym->final_value_is_known();
const tls::Tls_optimization optimized_type
= Target_i386::optimize_tls_reloc(is_final, r_type);
switch (r_type)
{
case elfcpp::R_386_TLS_GD: // Global-dynamic
if (optimized_type == tls::TLSOPT_NONE)
{
// Create a pair of GOT entries for the module index and
// dtv-relative offset.
Output_data_got<32, false>* got
= target->got_section(symtab, layout);
got->add_global_pair_with_rel(gsym, GOT_TYPE_TLS_PAIR,
target->rel_dyn_section(layout),
elfcpp::R_386_TLS_DTPMOD32,
elfcpp::R_386_TLS_DTPOFF32);
}
else if (optimized_type == tls::TLSOPT_TO_IE)
{
// Create a GOT entry for the tp-relative offset.
Output_data_got<32, false>* got
= target->got_section(symtab, layout);
got->add_global_with_rel(gsym, GOT_TYPE_TLS_NOFFSET,
target->rel_dyn_section(layout),
elfcpp::R_386_TLS_TPOFF);
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_global(object, r_type, gsym);
break;
case elfcpp::R_386_TLS_GOTDESC: // Global-dynamic (~oliva url)
target->define_tls_base_symbol(symtab, layout);
if (optimized_type == tls::TLSOPT_NONE)
{
// Create a double GOT entry with an R_386_TLS_DESC
// reloc. The R_386_TLS_DESC 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<32, false>* got = target->got_tlsdesc_section();
Reloc_section* rt = target->rel_tls_desc_section(layout);
got->add_global_pair_with_rel(gsym, GOT_TYPE_TLS_DESC, rt,
elfcpp::R_386_TLS_DESC, 0);
}
else if (optimized_type == tls::TLSOPT_TO_IE)
{
// Create a GOT entry for the tp-relative offset.
Output_data_got<32, false>* got
= target->got_section(symtab, layout);
got->add_global_with_rel(gsym, GOT_TYPE_TLS_NOFFSET,
target->rel_dyn_section(layout),
elfcpp::R_386_TLS_TPOFF);
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_global(object, r_type, gsym);
break;
case elfcpp::R_386_TLS_DESC_CALL:
break;
case elfcpp::R_386_TLS_LDM: // Local-dynamic
if (optimized_type == tls::TLSOPT_NONE)
{
// Create a GOT entry for the module index.
target->got_mod_index_entry(symtab, layout, object);
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_global(object, r_type, gsym);
break;
case elfcpp::R_386_TLS_LDO_32: // Alternate local-dynamic
break;
case elfcpp::R_386_TLS_IE: // Initial-exec
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_GOTIE:
layout->set_has_static_tls();
if (optimized_type == tls::TLSOPT_NONE)
{
// For the R_386_TLS_IE relocation, we need to create a
// dynamic relocation when building a shared library.
if (r_type == elfcpp::R_386_TLS_IE
&& parameters->options().shared())
{
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
rel_dyn->add_global_relative(gsym, elfcpp::R_386_RELATIVE,
output_section, object,
data_shndx,
reloc.get_r_offset());
}
// Create a GOT entry for the tp-relative offset.
Output_data_got<32, false>* got
= target->got_section(symtab, layout);
unsigned int dyn_r_type = (r_type == elfcpp::R_386_TLS_IE_32
? elfcpp::R_386_TLS_TPOFF32
: elfcpp::R_386_TLS_TPOFF);
unsigned int got_type = (r_type == elfcpp::R_386_TLS_IE_32
? GOT_TYPE_TLS_OFFSET
: GOT_TYPE_TLS_NOFFSET);
got->add_global_with_rel(gsym, got_type,
target->rel_dyn_section(layout),
dyn_r_type);
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_global(object, r_type, gsym);
break;
case elfcpp::R_386_TLS_LE: // Local-exec
case elfcpp::R_386_TLS_LE_32:
layout->set_has_static_tls();
if (parameters->options().shared())
{
// We need to create a dynamic relocation.
unsigned int dyn_r_type = (r_type == elfcpp::R_386_TLS_LE_32
? elfcpp::R_386_TLS_TPOFF32
: elfcpp::R_386_TLS_TPOFF);
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
rel_dyn->add_global(gsym, dyn_r_type, output_section, object,
data_shndx, reloc.get_r_offset());
}
break;
default:
gold_unreachable();
}
}
break;
case elfcpp::R_386_32PLT:
case elfcpp::R_386_TLS_GD_32:
case elfcpp::R_386_TLS_GD_PUSH:
case elfcpp::R_386_TLS_GD_CALL:
case elfcpp::R_386_TLS_GD_POP:
case elfcpp::R_386_TLS_LDM_32:
case elfcpp::R_386_TLS_LDM_PUSH:
case elfcpp::R_386_TLS_LDM_CALL:
case elfcpp::R_386_TLS_LDM_POP:
case elfcpp::R_386_USED_BY_INTEL_200:
default:
unsupported_reloc_global(object, r_type, gsym);
break;
}
}
// Process relocations for gc.
void
Target_i386::gc_process_relocs(Symbol_table* symtab,
Layout* layout,
Sized_relobj_file<32, false>* object,
unsigned int data_shndx,
unsigned int,
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)
{
gold::gc_process_relocs<32, false, Target_i386, Scan, Classify_reloc>(
symtab,
layout,
this,
object,
data_shndx,
prelocs,
reloc_count,
output_section,
needs_special_offset_handling,
local_symbol_count,
plocal_symbols);
}
// Scan relocations for a section.
void
Target_i386::scan_relocs(Symbol_table* symtab,
Layout* layout,
Sized_relobj_file<32, 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)
{
if (sh_type == elfcpp::SHT_RELA)
{
gold_error(_("%s: unsupported RELA reloc section"),
object->name().c_str());
return;
}
gold::scan_relocs<32, false, Target_i386, Scan, Classify_reloc>(
symtab,
layout,
this,
object,
data_shndx,
prelocs,
reloc_count,
output_section,
needs_special_offset_handling,
local_symbol_count,
plocal_symbols);
}
// Finalize the sections.
void
Target_i386::do_finalize_sections(
Layout* layout,
const Input_objects*,
Symbol_table* symtab)
{
const Reloc_section* rel_plt = (this->plt_ == NULL
? NULL
: this->plt_->rel_plt());
layout->add_target_dynamic_tags(true, this->got_plt_, rel_plt,
this->rel_dyn_, true, false);
// Emit any relocs we saved in an attempt to avoid generating COPY
// relocs.
if (this->copy_relocs_.any_saved_relocs())
this->copy_relocs_.emit(this->rel_dyn_section(layout));
// Set the size of the _GLOBAL_OFFSET_TABLE_ symbol to the size of
// the .got.plt section.
Symbol* sym = this->global_offset_table_;
if (sym != NULL)
{
uint32_t data_size = this->got_plt_->current_data_size();
symtab->get_sized_symbol<32>(sym)->set_symsize(data_size);
}
if (parameters->doing_static_link()
&& (this->plt_ == NULL || !this->plt_->has_irelative_section()))
{
// If linking statically, make sure that the __rel_iplt symbols
// were defined if necessary, even if we didn't create a PLT.
static const Define_symbol_in_segment syms[] =
{
{
"__rel_iplt_start", // name
elfcpp::PT_LOAD, // segment_type
elfcpp::PF_W, // segment_flags_set
elfcpp::PF(0), // segment_flags_clear
0, // value
0, // size
elfcpp::STT_NOTYPE, // type
elfcpp::STB_GLOBAL, // binding
elfcpp::STV_HIDDEN, // visibility
0, // nonvis
Symbol::SEGMENT_START, // offset_from_base
true // only_if_ref
},
{
"__rel_iplt_end", // name
elfcpp::PT_LOAD, // segment_type
elfcpp::PF_W, // segment_flags_set
elfcpp::PF(0), // segment_flags_clear
0, // value
0, // size
elfcpp::STT_NOTYPE, // type
elfcpp::STB_GLOBAL, // binding
elfcpp::STV_HIDDEN, // visibility