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binutils-gdb/gold/x86_64.cc
Sriraman Tallam ce97fa81e0 2010-04-18 Sriraman Tallam <tmsriram@google.com> 
* icf.cc (get_section_contents): Check for preemptible functions.
	Ignore addend when appropriate.
	* symtab.cc (should_add_dynsym_entry): Add new parameter.  Check for
	section folded.
	(add_from_relobj): Check for section folded.
	(set_dynsym_indexes): Fix call to should_add_dynsym_entry.
	* symtab.h (should_add_dynsym_entry): Add new parameter.
	* target-reloc.h (scan_relocs): Check for section folded.
	* x86_64.cc (Target_x86_64::Scan::possible_function_pointer_reloc):
	Check reloc types for function pointers in shared objects.
	* testsuite/Makefile.am (icf_virtual_function_folding_test): New test
	case.
	(icf_preemptible_functions_test): New test case.
	(icf_string_merge_test): New test case.
	* testsuite.Makefile.in: Regenerate.
	* testsuite/icf_safe_so_test.sh: Change to not fold foo_glob and
	bar_glob.  Refactor code.
	* testsuite/icf_preemptible_functions_test.cc: New file.
	* testsuite/icf_preemptible_functions_test.sh: New file.
	* testsuite/icf_string_merge_test.cc: New file.
	* testsuite/icf_string_merge_test.sh: New file.
	* testsuite/icf_virtual_function_folding_test.cc: New file.
	* testsuite/icf_virtual_function_folding_test.sh: New file.
2010-04-20 21:13:30 +00:00

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// x86_64.cc -- x86_64 target support for gold.
// Copyright 2006, 2007, 2008, 2009 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 "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 "gc.h"
#include "icf.h"
namespace
{
using namespace gold;
class Output_data_plt_x86_64;
// 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
class Target_x86_64 : public Target_freebsd<64, 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, 64, false> Reloc_section;
Target_x86_64()
: Target_freebsd<64, false>(&x86_64_info),
got_(NULL), plt_(NULL), got_plt_(NULL), global_offset_table_(NULL),
rela_dyn_(NULL), copy_relocs_(elfcpp::R_X86_64_COPY), dynbss_(NULL),
got_mod_index_offset_(-1U), tlsdesc_reloc_info_(),
tls_base_symbol_defined_(false)
{ }
// 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.
inline bool
can_check_for_function_pointers() const
{ return !parameters->options().pie(); }
// 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<64, 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<64, 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<64, 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<64>::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<64, 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*);
// Relocate a section during a relocatable link.
void
relocate_for_relocatable(const Relocate_info<64, false>*,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
Output_section* output_section,
off_t offset_in_output_section,
const Relocatable_relocs*,
unsigned char* view,
elfcpp::Elf_types<64>::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;
// Adjust -fstack-split code which calls non-stack-split code.
void
do_calls_non_split(Relobj* object, unsigned int shndx,
section_offset_type fnoffset, section_size_type fnsize,
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()
{
gold_assert(this->got_ != NULL);
return this->got_->data_size();
}
// Add a new reloc argument, returning the index in the vector.
size_t
add_tlsdesc_info(Sized_relobj<64, false>* object, unsigned int r_sym)
{
this->tlsdesc_reloc_info_.push_back(Tlsdesc_info(object, r_sym));
return this->tlsdesc_reloc_info_.size() - 1;
}
private:
// The class which scans relocations.
class Scan
{
public:
Scan()
: issued_non_pic_error_(false)
{ }
inline void
local(Symbol_table* symtab, Layout* layout, Target_x86_64* target,
Sized_relobj<64, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rela<64, false>& reloc, unsigned int r_type,
const elfcpp::Sym<64, false>& lsym);
inline void
global(Symbol_table* symtab, Layout* layout, Target_x86_64* target,
Sized_relobj<64, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rela<64, 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<64, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rela<64, false>& reloc,
unsigned int r_type,
const elfcpp::Sym<64, false>& lsym);
inline bool
global_reloc_may_be_function_pointer(Symbol_table* symtab, Layout* layout,
Target_x86_64* target,
Sized_relobj<64, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rela<64, false>& reloc,
unsigned int r_type,
Symbol* gsym);
private:
static void
unsupported_reloc_local(Sized_relobj<64, false>*, unsigned int r_type);
static void
unsupported_reloc_global(Sized_relobj<64, false>*, unsigned int r_type,
Symbol*);
void
check_non_pic(Relobj*, unsigned int r_type);
inline bool
possible_function_pointer_reloc(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), saw_tls_block_reloc_(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<64, false>*, Target_x86_64*, Output_section*,
size_t relnum, const elfcpp::Rela<64, false>&,
unsigned int r_type, const Sized_symbol<64>*,
const Symbol_value<64>*,
unsigned char*, elfcpp::Elf_types<64>::Elf_Addr,
section_size_type);
private:
// Do a TLS relocation.
inline void
relocate_tls(const Relocate_info<64, false>*, Target_x86_64*,
size_t relnum, const elfcpp::Rela<64, false>&,
unsigned int r_type, const Sized_symbol<64>*,
const Symbol_value<64>*,
unsigned char*, elfcpp::Elf_types<64>::Elf_Addr,
section_size_type);
// Do a TLS General-Dynamic to Initial-Exec transition.
inline void
tls_gd_to_ie(const Relocate_info<64, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rela<64, false>&, unsigned int r_type,
elfcpp::Elf_types<64>::Elf_Addr value,
unsigned char* view,
elfcpp::Elf_types<64>::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<64, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rela<64, false>&, unsigned int r_type,
elfcpp::Elf_types<64>::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<64, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rela<64, false>&, unsigned int r_type,
elfcpp::Elf_types<64>::Elf_Addr value,
unsigned char* view,
elfcpp::Elf_types<64>::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<64, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rela<64, false>&, unsigned int r_type,
elfcpp::Elf_types<64>::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<64, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rela<64, false>&, unsigned int r_type,
elfcpp::Elf_types<64>::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<64, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rela<64, false>&, unsigned int r_type,
elfcpp::Elf_types<64>::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_;
// This is set if we see a relocation which could load the address
// of the TLS block. Whether we see such a relocation determines
// how we handle the R_X86_64_DTPOFF32 relocation, which is used
// in debugging sections.
bool saw_tls_block_reloc_;
};
// A class which returns the size required for a relocation type,
// used while scanning relocs during a relocatable link.
class Relocatable_size_for_reloc
{
public:
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);
// 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_space*
got_plt_section() const
{
gold_assert(this->got_plt_ != NULL);
return this->got_plt_;
}
// 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*);
// 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<64, false>* object);
// Get the PLT section.
Output_data_plt_x86_64*
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;
// Add a potential copy relocation.
void
copy_reloc(Symbol_table* symtab, Layout* layout,
Sized_relobj<64, false>* object,
unsigned int shndx, Output_section* output_section,
Symbol* sym, const elfcpp::Rela<64, false>& reloc)
{
this->copy_relocs_.copy_reloc(symtab, layout,
symtab->get_sized_symbol<64>(sym),
object, shndx, output_section,
reloc, 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;
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<64, 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<64, 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* plt_;
// The GOT PLT section.
Output_data_space* got_plt_;
// The _GLOBAL_OFFSET_TABLE_ symbol.
Symbol* global_offset_table_;
// The dynamic reloc section.
Reloc_section* rela_dyn_;
// Relocs saved to avoid a COPY reloc.
Copy_relocs<elfcpp::SHT_RELA, 64, false> copy_relocs_;
// Space for variables copied with a COPY reloc.
Output_data_space* dynbss_;
// 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_;
};
const Target::Target_info Target_x86_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
'\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)
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
};
// This is called when a new output section is created. This is where
// we handle the SHF_X86_64_LARGE.
void
Target_x86_64::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.
Output_data_got<64, false>*
Target_x86_64::got_section(Symbol_table* symtab, Layout* layout)
{
if (this->got_ == NULL)
{
gold_assert(symtab != NULL && layout != NULL);
this->got_ = new Output_data_got<64, false>();
Output_section* os;
os = layout->add_output_section_data(".got", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_WRITE),
this->got_, false, true, true,
false);
this->got_plt_ = new Output_data_space(8, "** GOT PLT");
os = layout->add_output_section_data(".got.plt", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_WRITE),
this->got_plt_, false, false,
false, true);
// The first three entries are reserved.
this->got_plt_->set_current_data_size(3 * 8);
// 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);
}
return this->got_;
}
// Get the dynamic reloc section, creating it if necessary.
Target_x86_64::Reloc_section*
Target_x86_64::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_, true,
false, false, false);
}
return this->rela_dyn_;
}
// A class to handle the PLT data.
class Output_data_plt_x86_64 : public Output_section_data
{
public:
typedef Output_data_reloc<elfcpp::SHT_RELA, true, 64, false> Reloc_section;
Output_data_plt_x86_64(Layout*, Output_data_got<64, false>*,
Output_data_space*);
// Add an entry to the PLT.
void
add_entry(Symbol* gsym);
// 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_ + 1) * plt_entry_size; }
// Return the .rela.plt section data.
const Reloc_section*
rela_plt() const
{ return this->rel_; }
// Return where the TLSDESC relocations should go.
Reloc_section*
rela_tlsdesc(Layout*);
protected:
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")); }
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 unsigned char first_plt_entry[plt_entry_size];
// Other entries in the PLT for an executable.
static unsigned char plt_entry[plt_entry_size];
// The reserved TLSDESC entry in the PLT for an executable.
static unsigned char tlsdesc_plt_entry[plt_entry_size];
// 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 .got section.
Output_data_got<64, false>* got_;
// The .got.plt section.
Output_data_space* got_plt_;
// The number of PLT entries.
unsigned int count_;
// Offset of the reserved TLSDESC_GOT entry when needed.
unsigned int tlsdesc_got_offset_;
};
// 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_x86_64::Output_data_plt_x86_64(Layout* layout,
Output_data_got<64, false>* got,
Output_data_space* got_plt)
: Output_section_data(8), tlsdesc_rel_(NULL), got_(got), got_plt_(got_plt),
count_(0), tlsdesc_got_offset_(-1U)
{
this->rel_ = new Reloc_section(false);
layout->add_output_section_data(".rela.plt", elfcpp::SHT_RELA,
elfcpp::SHF_ALLOC, this->rel_, true,
false, false, false);
}
void
Output_data_plt_x86_64::do_adjust_output_section(Output_section* os)
{
os->set_entsize(plt_entry_size);
}
// Add an entry to the PLT.
void
Output_data_plt_x86_64::add_entry(Symbol* gsym)
{
gold_assert(!gsym->has_plt_offset());
// Note that when setting the PLT offset we skip the initial
// reserved PLT entry.
gsym->set_plt_offset((this->count_ + 1) * 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 + 8);
// Every PLT entry needs a reloc.
gsym->set_needs_dynsym_entry();
this->rel_->add_global(gsym, elfcpp::R_X86_64_JUMP_SLOT, this->got_plt_,
got_offset, 0);
// 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.
}
// Return where the TLSDESC relocations should go, creating it if
// necessary. These follow the JUMP_SLOT relocations.
Output_data_plt_x86_64::Reloc_section*
Output_data_plt_x86_64::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_,
true, false, false, false);
gold_assert(this->tlsdesc_rel_->output_section() ==
this->rel_->output_section());
}
return this->tlsdesc_rel_;
}
// Set the final size.
void
Output_data_plt_x86_64::set_final_data_size()
{
unsigned int count = this->count_;
if (this->has_tlsdesc_entry())
++count;
this->set_data_size((count + 1) * plt_entry_size);
}
// The first entry in the PLT for an executable.
unsigned char Output_data_plt_x86_64::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)
};
// Subsequent entries in the PLT for an executable.
unsigned char Output_data_plt_x86_64::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
};
// The reserved TLSDESC entry in the PLT for an executable.
unsigned char Output_data_plt_x86_64::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
};
// Write out the PLT. This uses the hand-coded instructions above,
// and adjusts them as needed. This is specified by the AMD64 ABI.
void
Output_data_plt_x86_64::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();
const section_size_type got_size =
convert_to_section_size_type(this->got_plt_->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.
elfcpp::Elf_types<64>::Elf_Addr plt_address = this->address();
// The base address of the .got section.
elfcpp::Elf_types<64>::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.
elfcpp::Elf_types<64>::Elf_Addr got_address = this->got_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)));
pov += plt_entry_size;
unsigned char* got_pov = got_view;
memset(got_pov, 0, 24);
got_pov += 24;
unsigned int plt_offset = plt_entry_size;
unsigned int got_offset = 24;
const unsigned int count = this->count_;
for (unsigned int plt_index = 0;
plt_index < count;
++plt_index,
pov += plt_entry_size,
got_pov += 8,
plt_offset += plt_entry_size,
got_offset += 8)
{
// Set and adjust the PLT entry itself.
memcpy(pov, plt_entry, plt_entry_size);
elfcpp::Swap_unaligned<32, false>::writeval(pov + 2,
(got_address + got_offset
- (plt_address + plt_offset
+ 6)));
elfcpp::Swap_unaligned<32, false>::writeval(pov + 7, plt_index);
elfcpp::Swap<32, false>::writeval(pov + 12,
- (plt_offset + plt_entry_size));
// Set the entry in the GOT.
elfcpp::Swap<64, false>::writeval(got_pov, plt_address + plt_offset + 6);
}
if (this->has_tlsdesc_entry())
{
// Set and adjust the reserved TLSDESC PLT entry.
unsigned int tlsdesc_got_offset = this->get_tlsdesc_got_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)));
pov += 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.
void
Target_x86_64::make_plt_section(Symbol_table* symtab, Layout* layout)
{
if (this->plt_ == NULL)
{
// Create the GOT sections first.
this->got_section(symtab, layout);
this->plt_ = new Output_data_plt_x86_64(layout, this->got_,
this->got_plt_);
layout->add_output_section_data(".plt", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_EXECINSTR),
this->plt_, false, false, false, false);
}
}
// Return the section for TLSDESC relocations.
Target_x86_64::Reloc_section*
Target_x86_64::rela_tlsdesc_section(Layout* layout) const
{
return this->plt_section()->rela_tlsdesc(layout);
}
// Create a PLT entry for a global symbol.
void
Target_x86_64::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(gsym);
}
// Define the _TLS_MODULE_BASE_ symbol in the TLS segment.
void
Target_x86_64::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.
void
Target_x86_64::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.
unsigned int
Target_x86_64::got_mod_index_entry(Symbol_table* symtab, Layout* layout,
Sized_relobj<64, 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.
tls::Tls_optimization
Target_x86_64::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();
}
}
// Report an unsupported relocation against a local symbol.
void
Target_x86_64::Scan::unsupported_reloc_local(Sized_relobj<64, 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.
void
Target_x86_64::Scan::check_non_pic(Relobj* object, unsigned int r_type)
{
switch (r_type)
{
// These are the relocation types supported by glibc for x86_64.
case elfcpp::R_X86_64_RELATIVE:
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_32:
case elfcpp::R_X86_64_PC32:
case elfcpp::R_X86_64_COPY:
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; "
"recompile with -fPIC"));
this->issued_non_pic_error_ = true;
return;
case elfcpp::R_X86_64_NONE:
gold_unreachable();
}
}
// Scan a relocation for a local symbol.
inline void
Target_x86_64::Scan::local(Symbol_table* symtab,
Layout* layout,
Target_x86_64* target,
Sized_relobj<64, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rela<64, false>& reloc,
unsigned int r_type,
const elfcpp::Sym<64, false>& lsym)
{
switch (r_type)
{
case elfcpp::R_X86_64_NONE:
case elfcpp::R_386_GNU_VTINHERIT:
case elfcpp::R_386_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<64>(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());
}
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())
{
this->check_non_pic(object, r_type);
Reloc_section* rela_dyn = target->rela_dyn_section(layout);
unsigned int r_sym = elfcpp::elf_r_sym<64>(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_PC16:
case elfcpp::R_X86_64_PC8:
break;
case elfcpp::R_X86_64_PLT32:
// 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_GOTPLT64:
{
// The symbol requires a GOT entry.
Output_data_got<64, false>* got = target->got_section(symtab, layout);
unsigned int r_sym = elfcpp::elf_r_sym<64>(reloc.get_r_info());
if (got->add_local(object, r_sym, GOT_TYPE_STANDARD))
{
// 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)
rela_dyn->add_local_relative(
object, r_sym, elfcpp::R_X86_64_RELATIVE, got,
object->local_got_offset(r_sym, GOT_TYPE_STANDARD), 0);
else
{
this->check_non_pic(object, r_type);
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:
// 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::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<64>(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_rela(object, r_sym,
shndx,
GOT_TYPE_TLS_PAIR,
target->rela_dyn_section(layout),
elfcpp::R_X86_64_DTPMOD64, 0);
}
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.
Output_data_got<64, false>* got
= target->got_section(symtab, layout);
unsigned int r_sym = elfcpp::elf_r_sym<64>(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::R_X86_64_TLSDESC, arg,
got, got_offset, 0);
}
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_local(object, r_type);
break;
case elfcpp::R_X86_64_TLSDESC_CALL:
break;
case elfcpp::R_X86_64_TLSLD: // 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_X86_64_DTPOFF32:
case elfcpp::R_X86_64_DTPOFF64:
break;
case elfcpp::R_X86_64_GOTTPOFF: // Initial-exec
layout->set_has_static_tls();
if (optimized_type == tls::TLSOPT_NONE)
{
// Create a GOT entry for the tp-relative offset.
Output_data_got<64, false>* got
= target->got_section(symtab, layout);
unsigned int r_sym = elfcpp::elf_r_sym<64>(reloc.get_r_info());
got->add_local_with_rela(object, r_sym, GOT_TYPE_TLS_OFFSET,
target->rela_dyn_section(layout),
elfcpp::R_X86_64_TPOFF64);
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_local(object, r_type);
break;
case elfcpp::R_X86_64_TPOFF32: // Local-exec
layout->set_has_static_tls();
if (output_is_shared)
unsupported_reloc_local(object, r_type);
break;
default:
gold_unreachable();
}
}
break;
case elfcpp::R_X86_64_SIZE32:
case elfcpp::R_X86_64_SIZE64:
default:
gold_error(_("%s: unsupported reloc %u against local symbol"),
object->name().c_str(), r_type);
break;
}
}
// Report an unsupported relocation against a global symbol.
void
Target_x86_64::Scan::unsupported_reloc_global(Sized_relobj<64, 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());
}
// Returns true if this relocation type could be that of a function pointer.
inline bool
Target_x86_64::Scan::possible_function_pointer_reloc(unsigned int r_type)
{
switch (r_type)
{
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:
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_GOTPLT64:
{
return true;
}
}
return false;
}
// For safe ICF, scan a relocation for a local symbol to check if it
// corresponds to a function pointer being taken. In that case mark
// the function whose pointer was taken as not foldable.
inline bool
Target_x86_64::Scan::local_reloc_may_be_function_pointer(
Symbol_table* ,
Layout* ,
Target_x86_64* ,
Sized_relobj<64, false>* ,
unsigned int ,
Output_section* ,
const elfcpp::Rela<64, false>& ,
unsigned int r_type,
const elfcpp::Sym<64, false>&)
{
// When building a shared library, do not fold any local symbols as it is
// not possible to distinguish pointer taken versus a call by looking at
// the relocation types.
return (parameters->options().shared()
|| possible_function_pointer_reloc(r_type));
}
// For safe ICF, scan a relocation for a global symbol to check if it
// corresponds to a function pointer being taken. In that case mark
// the function whose pointer was taken as not foldable.
inline bool
Target_x86_64::Scan::global_reloc_may_be_function_pointer(
Symbol_table*,
Layout* ,
Target_x86_64* ,
Sized_relobj<64, false>* ,
unsigned int ,
Output_section* ,
const elfcpp::Rela<64, false>& ,
unsigned int r_type,
Symbol* gsym)
{
// When building a shared library, do not fold symbols whose visibility
// is hidden, internal or protected.
return ((parameters->options().shared()
&& (gsym->visibility() == elfcpp::STV_INTERNAL
|| gsym->visibility() == elfcpp::STV_PROTECTED
|| gsym->visibility() == elfcpp::STV_HIDDEN))
|| possible_function_pointer_reloc(r_type));
}
// Scan a relocation for a global symbol.
inline void
Target_x86_64::Scan::global(Symbol_table* symtab,
Layout* layout,
Target_x86_64* target,
Sized_relobj<64, false>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rela<64, false>& reloc,
unsigned int r_type,
Symbol* gsym)
{
switch (r_type)
{
case elfcpp::R_X86_64_NONE:
case elfcpp::R_386_GNU_VTINHERIT:
case elfcpp::R_386_GNU_VTENTRY:
break;
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:
{
// 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(Symbol::ABSOLUTE_REF))
{
if (gsym->may_need_copy_reloc())
{
target->copy_reloc(symtab, layout, object,
data_shndx, output_section, gsym, reloc);
}
else if (r_type == elfcpp::R_X86_64_64
&& gsym->can_use_relative_reloc(false))
{
Reloc_section* rela_dyn = target->rela_dyn_section(layout);
rela_dyn->add_global_relative(gsym, elfcpp::R_X86_64_RELATIVE,
output_section, object,
data_shndx, reloc.get_r_offset(),
reloc.get_r_addend());
}
else
{
this->check_non_pic(object, r_type);
Reloc_section* rela_dyn = target->rela_dyn_section(layout);
rela_dyn->add_global(gsym, r_type, output_section, object,
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_PC16:
case elfcpp::R_X86_64_PC8:
{
// Make a PLT entry if necessary.
if (gsym->needs_plt_entry())
target->make_plt_entry(symtab, layout, gsym);
// Make a dynamic relocation if necessary.
int flags = Symbol::NON_PIC_REF;
if (gsym->is_func())
flags |= Symbol::FUNCTION_CALL;
if (gsym->needs_dynamic_reloc(flags))
{
if (gsym->may_need_copy_reloc())
{
target->copy_reloc(symtab, layout, object,
data_shndx, output_section, gsym, reloc);
}
else
{
this->check_non_pic(object, r_type);
Reloc_section* rela_dyn = target->rela_dyn_section(layout);
rela_dyn->add_global(gsym, r_type, output_section, object,
data_shndx, reloc.get_r_offset(),
reloc.get_r_addend());
}
}
}
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_GOTPLT64:
{
// The symbol requires a GOT entry.
Output_data_got<64, false>* got = target->got_section(symtab, layout);
if (gsym->final_value_is_known())
got->add_global(gsym, GOT_TYPE_STANDARD);
else
{
// If this symbol is not fully resolved, we need to add a
// dynamic relocation for it.
Reloc_section* rela_dyn = target->rela_dyn_section(layout);
if (gsym->is_from_dynobj()
|| gsym->is_undefined()
|| gsym->is_preemptible())
got->add_global_with_rela(gsym, GOT_TYPE_STANDARD, rela_dyn,
elfcpp::R_X86_64_GLOB_DAT);
else
{
if (got->add_global(gsym, GOT_TYPE_STANDARD))
rela_dyn->add_global_relative(
gsym, elfcpp::R_X86_64_RELATIVE, got,
gsym->got_offset(GOT_TYPE_STANDARD), 0);
}
}
// For GOTPLT64, we also need a PLT entry (but only if the
// symbol is not fully resolved).
if (r_type == elfcpp::R_X86_64_GOTPLT64
&& !gsym->final_value_is_known())
target->make_plt_entry(symtab, layout, gsym);
}
break;
case elfcpp::R_X86_64_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_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 also need a PLT entry (but only if the
// symbol is not fully resolved).
if (r_type == elfcpp::R_X86_64_PLTOFF64
&& !gsym->final_value_is_known())
target->make_plt_entry(symtab, layout, gsym);
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:
// 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 for global()
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
{
const bool is_final = gsym->final_value_is_known();
const tls::Tls_optimization optimized_type
= Target_x86_64::optimize_tls_reloc(is_final, 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);
got->add_global_pair_with_rela(gsym, GOT_TYPE_TLS_PAIR,
target->rela_dyn_section(layout),
elfcpp::R_X86_64_DTPMOD64,
elfcpp::R_X86_64_DTPOFF64);
}
else if (optimized_type == tls::TLSOPT_TO_IE)
{
// Create a GOT entry for the tp-relative offset.
Output_data_got<64, false>* got
= target->got_section(symtab, layout);
got->add_global_with_rela(gsym, GOT_TYPE_TLS_OFFSET,
target->rela_dyn_section(layout),
elfcpp::R_X86_64_TPOFF64);
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_global(object, r_type, gsym);
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);
// Create a double GOT entry with an R_X86_64_TLSDESC reloc.
Output_data_got<64, false>* got
= target->got_section(symtab, layout);
Reloc_section *rt = target->rela_tlsdesc_section(layout);
got->add_global_pair_with_rela(gsym, GOT_TYPE_TLS_DESC, rt,
elfcpp::R_X86_64_TLSDESC, 0);
}
else if (optimized_type == tls::TLSOPT_TO_IE)
{
// Create a GOT entry for the tp-relative offset.
Output_data_got<64, false>* got
= target->got_section(symtab, layout);
got->add_global_with_rela(gsym, GOT_TYPE_TLS_OFFSET,
target->rela_dyn_section(layout),
elfcpp::R_X86_64_TPOFF64);
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_global(object, r_type, gsym);
break;
case elfcpp::R_X86_64_TLSDESC_CALL:
break;
case elfcpp::R_X86_64_TLSLD: // 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_X86_64_DTPOFF32:
case elfcpp::R_X86_64_DTPOFF64:
break;
case elfcpp::R_X86_64_GOTTPOFF: // Initial-exec
layout->set_has_static_tls();
if (optimized_type == tls::TLSOPT_NONE)
{
// Create a GOT entry for the tp-relative offset.
Output_data_got<64, false>* got
= target->got_section(symtab, layout);
got->add_global_with_rela(gsym, GOT_TYPE_TLS_OFFSET,
target->rela_dyn_section(layout),
elfcpp::R_X86_64_TPOFF64);
}
else if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_global(object, r_type, gsym);
break;
case elfcpp::R_X86_64_TPOFF32: // Local-exec
layout->set_has_static_tls();
if (parameters->options().shared())
unsupported_reloc_local(object, r_type);
break;
default:
gold_unreachable();
}
}
break;
case elfcpp::R_X86_64_SIZE32:
case elfcpp::R_X86_64_SIZE64:
default:
gold_error(_("%s: unsupported reloc %u against global symbol %s"),
object->name().c_str(), r_type,
gsym->demangled_name().c_str());
break;
}
}
void
Target_x86_64::gc_process_relocs(Symbol_table* symtab,
Layout* layout,
Sized_relobj<64, 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_REL)
{
return;
}
gold::gc_process_relocs<64, false, Target_x86_64, elfcpp::SHT_RELA,
Target_x86_64::Scan>(
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_x86_64::scan_relocs(Symbol_table* symtab,
Layout* layout,
Sized_relobj<64, 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_REL)
{
gold_error(_("%s: unsupported REL reloc section"),
object->name().c_str());
return;
}
gold::scan_relocs<64, false, Target_x86_64, elfcpp::SHT_RELA,
Target_x86_64::Scan>(
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_x86_64::do_finalize_sections(
Layout* layout,
const Input_objects*,
Symbol_table* symtab)
{
const Reloc_section* rel_plt = (this->plt_ == NULL
? NULL
: this->plt_->rela_plt());
layout->add_target_dynamic_tags(false, this->got_plt_, rel_plt,
this->rela_dyn_, true, false);
// Fill in some more dynamic tags.
Output_data_dynamic* const odyn = layout->dynamic_data();
if (odyn != NULL)
{
if (this->plt_ != NULL
&& this->plt_->output_section() != NULL
&& this->plt_->has_tlsdesc_entry())
{
unsigned int plt_offset = this->plt_->get_tlsdesc_plt_offset();
unsigned int got_offset = this->plt_->get_tlsdesc_got_offset();
this->got_->finalize_data_size();
odyn->add_section_plus_offset(elfcpp::DT_TLSDESC_PLT,
this->plt_, plt_offset);
odyn->add_section_plus_offset(elfcpp::DT_TLSDESC_GOT,
this->got_, got_offset);
}
}
// 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->rela_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)
{
uint64_t data_size = this->got_plt_->current_data_size();
symtab->get_sized_symbol<64>(sym)->set_symsize(data_size);
}
}
// Perform a relocation.
inline bool
Target_x86_64::Relocate::relocate(const Relocate_info<64, false>* relinfo,
Target_x86_64* target,
Output_section*,
size_t relnum,
const elfcpp::Rela<64, false>& rela,
unsigned int r_type,
const Sized_symbol<64>* gsym,
const Symbol_value<64>* psymval,
unsigned char* view,
elfcpp::Elf_types<64>::Elf_Addr address,
section_size_type view_size)
{
if (this->skip_call_tls_get_addr_)
{
if ((r_type != elfcpp::R_X86_64_PLT32
&& r_type != elfcpp::R_X86_64_PC32)
|| gsym == NULL
|| strcmp(gsym->name(), "__tls_get_addr") != 0)
{
gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
_("missing expected TLS relocation"));
}
else
{
this->skip_call_tls_get_addr_ = false;
return false;
}
}
// Pick the value to use for symbols defined in shared objects.
Symbol_value<64> symval;
if (gsym != NULL
&& gsym->use_plt_offset(r_type == elfcpp::R_X86_64_PC64
|| r_type == elfcpp::R_X86_64_PC32
|| r_type == elfcpp::R_X86_64_PC16
|| r_type == elfcpp::R_X86_64_PC8))
{
symval.set_output_value(target->plt_section()->address()
+ gsym->plt_offset());
psymval = &symval;
}
const Sized_relobj<64, false>* object = relinfo->object;
const elfcpp::Elf_Xword addend = rela.get_r_addend();
// Get the GOT offset if needed.
// The GOT pointer points to the end of the GOT section.
// We need to subtract the size of the GOT section to get
// the actual offset to use in the relocation.
bool have_got_offset = false;
unsigned int got_offset = 0;
switch (r_type)
{
case elfcpp::R_X86_64_GOT32:
case elfcpp::R_X86_64_GOT64:
case elfcpp::R_X86_64_GOTPLT64:
case elfcpp::R_X86_64_GOTPCREL:
case elfcpp::R_X86_64_GOTPCREL64:
if (gsym != NULL)
{
gold_assert(gsym->has_got_offset(GOT_TYPE_STANDARD));
got_offset = gsym->got_offset(GOT_TYPE_STANDARD) - target->got_size();
}
else
{
unsigned int r_sym = elfcpp::elf_r_sym<64>(rela.get_r_info());
gold_assert(object->local_has_got_offset(r_sym, GOT_TYPE_STANDARD));
got_offset = (object->local_got_offset(r_sym, GOT_TYPE_STANDARD)
- target->got_size());
}
have_got_offset = true;
break;
default:
break;
}
switch (r_type)
{
case elfcpp::R_X86_64_NONE:
case elfcpp::R_386_GNU_VTINHERIT:
case elfcpp::R_386_GNU_VTENTRY:
break;
case elfcpp::R_X86_64_64:
Relocate_functions<64, false>::rela64(view, object, psymval, addend);
break;
case elfcpp::R_X86_64_PC64:
Relocate_functions<64, false>::pcrela64(view, object, psymval, addend,
address);
break;
case elfcpp::R_X86_64_32:
// FIXME: we need to verify that value + addend fits into 32 bits:
// uint64_t x = value + addend;
// x == static_cast<uint64_t>(static_cast<uint32_t>(x))
// Likewise for other <=32-bit relocations (but see R_X86_64_32S).
Relocate_functions<64, false>::rela32(view, object, psymval, addend);
break;
case elfcpp::R_X86_64_32S:
// FIXME: we need to verify that value + addend fits into 32 bits:
// int64_t x = value + addend; // note this quantity is signed!
// x == static_cast<int64_t>(static_cast<int32_t>(x))
Relocate_functions<64, false>::rela32(view, object, psymval, addend);
break;
case elfcpp::R_X86_64_PC32:
Relocate_functions<64, false>::pcrela32(view, object, psymval, addend,
address);
break;
case elfcpp::R_X86_64_16:
Relocate_functions<64, false>::rela16(view, object, psymval, addend);
break;
case elfcpp::R_X86_64_PC16:
Relocate_functions<64, false>::pcrela16(view, object, psymval, addend,
address);
break;
case elfcpp::R_X86_64_8:
Relocate_functions<64, false>::rela8(view, object, psymval, addend);
break;
case elfcpp::R_X86_64_PC8:
Relocate_functions<64, false>::pcrela8(view, object, psymval, addend,
address);
break;
case elfcpp::R_X86_64_PLT32:
gold_assert(gsym == NULL
|| gsym->has_plt_offset()
|| gsym->final_value_is_known()
|| (gsym->is_defined()
&& !gsym->is_from_dynobj()
&& !gsym->is_preemptible()));
// Note: while this code looks the same as for R_X86_64_PC32, it
// behaves differently because psymval was set to point to
// the PLT entry, rather than the symbol, in Scan::global().
Relocate_functions<64, false>::pcrela32(view, object, psymval, addend,
address);
break;
case elfcpp::R_X86_64_PLTOFF64:
{
gold_assert(gsym);
gold_assert(gsym->has_plt_offset()
|| gsym->final_value_is_known());
elfcpp::Elf_types<64>::Elf_Addr got_address;
got_address = target->got_section(NULL, NULL)->address();
Relocate_functions<64, false>::rela64(view, object, psymval,
addend - got_address);
}
case elfcpp::R_X86_64_GOT32:
gold_assert(have_got_offset);
Relocate_functions<64, false>::rela32(view, got_offset, addend);
break;
case elfcpp::R_X86_64_GOTPC32:
{
gold_assert(gsym);
elfcpp::Elf_types<64>::Elf_Addr value;
value = target->got_plt_section()->address();
Relocate_functions<64, false>::pcrela32(view, value, addend, address);
}
break;
case elfcpp::R_X86_64_GOT64:
// The ABI doc says "Like GOT64, but indicates a PLT entry is needed."
// Since we always add a PLT entry, this is equivalent.
case elfcpp::R_X86_64_GOTPLT64:
gold_assert(have_got_offset);
Relocate_functions<64, false>::rela64(view, got_offset, addend);
break;
case elfcpp::R_X86_64_GOTPC64:
{
gold_assert(gsym);
elfcpp::Elf_types<64>::Elf_Addr value;
value = target->got_plt_section()->address();
Relocate_functions<64, false>::pcrela64(view, value, addend, address);
}
break;
case elfcpp::R_X86_64_GOTOFF64:
{
elfcpp::Elf_types<64>::Elf_Addr value;
value = (psymval->value(object, 0)
- target->got_plt_section()->address());
Relocate_functions<64, false>::rela64(view, value, addend);
}
break;
case elfcpp::R_X86_64_GOTPCREL:
{
gold_assert(have_got_offset);
elfcpp::Elf_types<64>::Elf_Addr value;
value = target->got_plt_section()->address() + got_offset;
Relocate_functions<64, false>::pcrela32(view, value, addend, address);
}
break;
case elfcpp::R_X86_64_GOTPCREL64:
{
gold_assert(have_got_offset);
elfcpp::Elf_types<64>::Elf_Addr value;
value = target->got_plt_section()->address() + got_offset;
Relocate_functions<64, false>::pcrela64(view, value, addend, address);
}
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:
// 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_at_location(relinfo, relnum, rela.get_r_offset(),
_("unexpected reloc %u in object file"),
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
this->relocate_tls(relinfo, target, relnum, rela, r_type, gsym, psymval,
view, address, view_size);
break;
case elfcpp::R_X86_64_SIZE32:
case elfcpp::R_X86_64_SIZE64:
default:
gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
_("unsupported reloc %u"),
r_type);
break;
}
return true;
}
// Perform a TLS relocation.
inline void
Target_x86_64::Relocate::relocate_tls(const Relocate_info<64, false>* relinfo,
Target_x86_64* target,
size_t relnum,
const elfcpp::Rela<64, false>& rela,
unsigned int r_type,
const Sized_symbol<64>* gsym,
const Symbol_value<64>* psymval,
unsigned char* view,
elfcpp::Elf_types<64>::Elf_Addr address,
section_size_type view_size)
{
Output_segment* tls_segment = relinfo->layout->tls_segment();
const Sized_relobj<64, false>* object = relinfo->object;
const elfcpp::Elf_Xword addend = rela.get_r_addend();
elfcpp::Elf_types<64>::Elf_Addr value = psymval->value(relinfo->object, 0);
const bool is_final = (gsym == NULL
? !parameters->options().shared()
: gsym->final_value_is_known());
const tls::Tls_optimization optimized_type
= Target_x86_64::optimize_tls_reloc(is_final, r_type);
switch (r_type)
{
case elfcpp::R_X86_64_TLSGD: // Global-dynamic
this->saw_tls_block_reloc_ = true;
if (optimized_type == tls::TLSOPT_TO_LE)
{
gold_assert(tls_segment != NULL);
this->tls_gd_to_le(relinfo, relnum, tls_segment,
rela, r_type, value, view,
view_size);
break;
}
else
{
unsigned int got_type = (optimized_type == tls::TLSOPT_TO_IE
? GOT_TYPE_TLS_OFFSET
: GOT_TYPE_TLS_PAIR);
unsigned int got_offset;
if (gsym != NULL)
{
gold_assert(gsym->has_got_offset(got_type));
got_offset = gsym->got_offset(got_type) - target->got_size();
}
else
{
unsigned int r_sym = elfcpp::elf_r_sym<64>(rela.get_r_info());
gold_assert(object->local_has_got_offset(r_sym, got_type));
got_offset = (object->local_got_offset(r_sym, got_type)
- target->got_size());
}
if (optimized_type == tls::TLSOPT_TO_IE)
{
gold_assert(tls_segment != NULL);
value = target->got_plt_section()->address() + got_offset;
this->tls_gd_to_ie(relinfo, relnum, tls_segment, rela, r_type,
value, view, address, view_size);
break;
}
else if (optimized_type == tls::TLSOPT_NONE)
{
// Relocate the field with the offset of the pair of GOT
// entries.
value = target->got_plt_section()->address() + got_offset;
Relocate_functions<64, false>::pcrela32(view, value, addend,
address);
break;
}
}
gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
_("unsupported reloc %u"), r_type);
break;
case elfcpp::R_X86_64_GOTPC32_TLSDESC: // Global-dynamic (from ~oliva url)
case elfcpp::R_X86_64_TLSDESC_CALL:
this->saw_tls_block_reloc_ = true;
if (optimized_type == tls::TLSOPT_TO_LE)
{
gold_assert(tls_segment != NULL);
this->tls_desc_gd_to_le(relinfo, relnum, tls_segment,
rela, r_type, value, view,
view_size);
break;
}
else
{
unsigned int got_type = (optimized_type == tls::TLSOPT_TO_IE
? GOT_TYPE_TLS_OFFSET
: GOT_TYPE_TLS_DESC);
unsigned int got_offset;
if (gsym != NULL)
{
gold_assert(gsym->has_got_offset(got_type));
got_offset = gsym->got_offset(got_type) - target->got_size();
}
else
{
unsigned int r_sym = elfcpp::elf_r_sym<64>(rela.get_r_info());
gold_assert(object->local_has_got_offset(r_sym, got_type));
got_offset = (object->local_got_offset(r_sym, got_type)
- target->got_size());
}
if (optimized_type == tls::TLSOPT_TO_IE)
{
gold_assert(tls_segment != NULL);
value = target->got_plt_section()->address() + got_offset;
this->tls_desc_gd_to_ie(relinfo, relnum, tls_segment,
rela, r_type, value, view, address,
view_size);
break;
}
else if (optimized_type == tls::TLSOPT_NONE)
{
if (r_type == elfcpp::R_X86_64_GOTPC32_TLSDESC)
{
// Relocate the field with the offset of the pair of GOT
// entries.
value = target->got_plt_section()->address() + got_offset;
Relocate_functions<64, false>::pcrela32(view, value, addend,
address);
}
break;
}
}
gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
_("unsupported reloc %u"), r_type);
break;
case elfcpp::R_X86_64_TLSLD: // Local-dynamic
this->saw_tls_block_reloc_ = true;
if (optimized_type == tls::TLSOPT_TO_LE)
{
gold_assert(tls_segment != NULL);
this->tls_ld_to_le(relinfo, relnum, tls_segment, rela, r_type,
value, view, view_size);
break;
}
else if (optimized_type == tls::TLSOPT_NONE)
{
// Relocate the field with the offset of the GOT entry for
// the module index.
unsigned int got_offset;
got_offset = (target->got_mod_index_entry(NULL, NULL, NULL)
- target->got_size());
value = target->got_plt_section()->address() + got_offset;
Relocate_functions<64, false>::pcrela32(view, value, addend,
address);
break;
}
gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
_("unsupported reloc %u"), r_type);
break;
case elfcpp::R_X86_64_DTPOFF32:
if (optimized_type == tls::TLSOPT_TO_LE)
{
// This relocation type is used in debugging information.
// In that case we need to not optimize the value. If we
// haven't seen a TLSLD reloc, then we assume we should not
// optimize this reloc.
if (this->saw_tls_block_reloc_)
{
gold_assert(tls_segment != NULL);
value -= tls_segment->memsz();
}
}
Relocate_functions<64, false>::rela32(view, value, addend);
break;
case elfcpp::R_X86_64_DTPOFF64:
if (optimized_type == tls::TLSOPT_TO_LE)
{
// See R_X86_64_DTPOFF32, just above, for why we test this.
if (this->saw_tls_block_reloc_)
{
gold_assert(tls_segment != NULL);
value -= tls_segment->memsz();
}
}
Relocate_functions<64, false>::rela64(view, value, addend);
break;
case elfcpp::R_X86_64_GOTTPOFF: // Initial-exec
if (optimized_type == tls::TLSOPT_TO_LE)
{
gold_assert(tls_segment != NULL);
Target_x86_64::Relocate::tls_ie_to_le(relinfo, relnum, tls_segment,
rela, r_type, value, view,
view_size);
break;
}
else if (optimized_type == tls::TLSOPT_NONE)
{
// Relocate the field with the offset of the GOT entry for
// the tp-relative offset of the symbol.
unsigned int got_offset;
if (gsym != NULL)
{
gold_assert(gsym->has_got_offset(GOT_TYPE_TLS_OFFSET));
got_offset = (gsym->got_offset(GOT_TYPE_TLS_OFFSET)
- target->got_size());
}
else
{
unsigned int r_sym = elfcpp::elf_r_sym<64>(rela.get_r_info());
gold_assert(object->local_has_got_offset(r_sym,
GOT_TYPE_TLS_OFFSET));
got_offset = (object->local_got_offset(r_sym, GOT_TYPE_TLS_OFFSET)
- target->got_size());
}
value = target->got_plt_section()->address() + got_offset;
Relocate_functions<64, false>::pcrela32(view, value, addend, address);
break;
}
gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
_("unsupported reloc type %u"),
r_type);
break;
case elfcpp::R_X86_64_TPOFF32: // Local-exec
value -= tls_segment->memsz();
Relocate_functions<64, false>::rela32(view, value, addend);
break;
}
}
// Do a relocation in which we convert a TLS General-Dynamic to an
// Initial-Exec.
inline void
Target_x86_64::Relocate::tls_gd_to_ie(const Relocate_info<64, false>* relinfo,
size_t relnum,
Output_segment*,
const elfcpp::Rela<64, false>& rela,
unsigned int,
elfcpp::Elf_types<64>::Elf_Addr value,
unsigned char* view,
elfcpp::Elf_types<64>::Elf_Addr address,
section_size_type view_size)
{
// .byte 0x66; leaq foo@tlsgd(%rip),%rdi;
// .word 0x6666; rex64; call __tls_get_addr
// ==> movq %fs:0,%rax; addq x@gottpoff(%rip),%rax
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, -4);
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, 12);
tls::check_tls(relinfo, relnum, rela.get_r_offset(),
(memcmp(view - 4, "\x66\x48\x8d\x3d", 4) == 0));
tls::check_tls(relinfo, relnum, rela.get_r_offset(),
(memcmp(view + 4, "\x66\x66\x48\xe8", 4) == 0));
memcpy(view - 4, "\x64\x48\x8b\x04\x25\0\0\0\0\x48\x03\x05\0\0\0\0", 16);
const elfcpp::Elf_Xword addend = rela.get_r_addend();
Relocate_functions<64, false>::pcrela32(view + 8, value, addend - 8, address);
// The next reloc should be a PLT32 reloc against __tls_get_addr.
// We can skip it.
this->skip_call_tls_get_addr_ = true;
}
// Do a relocation in which we convert a TLS General-Dynamic to a
// Local-Exec.
inline void
Target_x86_64::Relocate::tls_gd_to_le(const Relocate_info<64, false>* relinfo,
size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rela<64, false>& rela,
unsigned int,
elfcpp::Elf_types<64>::Elf_Addr value,
unsigned char* view,
section_size_type view_size)
{
// .byte 0x66; leaq foo@tlsgd(%rip),%rdi;
// .word 0x6666; rex64; call __tls_get_addr
// ==> movq %fs:0,%rax; leaq x@tpoff(%rax),%rax
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, -4);
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, 12);
tls::check_tls(relinfo, relnum, rela.get_r_offset(),
(memcmp(view - 4, "\x66\x48\x8d\x3d", 4) == 0));
tls::check_tls(relinfo, relnum, rela.get_r_offset(),
(memcmp(view + 4, "\x66\x66\x48\xe8", 4) == 0));
memcpy(view - 4, "\x64\x48\x8b\x04\x25\0\0\0\0\x48\x8d\x80\0\0\0\0", 16);
value -= tls_segment->memsz();
Relocate_functions<64, false>::rela32(view + 8, value, 0);
// The next reloc should be a PLT32 reloc against __tls_get_addr.
// We can skip it.
this->skip_call_tls_get_addr_ = true;
}
// Do a TLSDESC-style General-Dynamic to Initial-Exec transition.
inline void
Target_x86_64::Relocate::tls_desc_gd_to_ie(
const Relocate_info<64, false>* relinfo,
size_t relnum,
Output_segment*,
const elfcpp::Rela<64, false>& rela,
unsigned int r_type,
elfcpp::Elf_types<64>::Elf_Addr value,
unsigned char* view,
elfcpp::Elf_types<64>::Elf_Addr address,
section_size_type view_size)
{
if (r_type == elfcpp::R_X86_64_GOTPC32_TLSDESC)
{
// leaq foo@tlsdesc(%rip), %rax
// ==> movq foo@gottpoff(%rip), %rax
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, -3);
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, 4);
tls::check_tls(relinfo, relnum, rela.get_r_offset(),
view[-3] == 0x48 && view[-2] == 0x8d && view[-1] == 0x05);
view[-2] = 0x8b;
const elfcpp::Elf_Xword addend = rela.get_r_addend();
Relocate_functions<64, false>::pcrela32(view, value, addend, address);
}
else
{
// call *foo@tlscall(%rax)
// ==> nop; nop
gold_assert(r_type == elfcpp::R_X86_64_TLSDESC_CALL);
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, 2);
tls::check_tls(relinfo, relnum, rela.get_r_offset(),
view[0] == 0xff && view[1] == 0x10);
view[0] = 0x66;
view[1] = 0x90;
}
}
// Do a TLSDESC-style General-Dynamic to Local-Exec transition.
inline void
Target_x86_64::Relocate::tls_desc_gd_to_le(
const Relocate_info<64, false>* relinfo,
size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rela<64, false>& rela,
unsigned int r_type,
elfcpp::Elf_types<64>::Elf_Addr value,
unsigned char* view,
section_size_type view_size)
{
if (r_type == elfcpp::R_X86_64_GOTPC32_TLSDESC)
{
// leaq foo@tlsdesc(%rip), %rax
// ==> movq foo@tpoff, %rax
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, -3);
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, 4);
tls::check_tls(relinfo, relnum, rela.get_r_offset(),
view[-3] == 0x48 && view[-2] == 0x8d && view[-1] == 0x05);
view[-2] = 0xc7;
view[-1] = 0xc0;
value -= tls_segment->memsz();
Relocate_functions<64, false>::rela32(view, value, 0);
}
else
{
// call *foo@tlscall(%rax)
// ==> nop; nop
gold_assert(r_type == elfcpp::R_X86_64_TLSDESC_CALL);
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, 2);
tls::check_tls(relinfo, relnum, rela.get_r_offset(),
view[0] == 0xff && view[1] == 0x10);
view[0] = 0x66;
view[1] = 0x90;
}
}
inline void
Target_x86_64::Relocate::tls_ld_to_le(const Relocate_info<64, false>* relinfo,
size_t relnum,
Output_segment*,
const elfcpp::Rela<64, false>& rela,
unsigned int,
elfcpp::Elf_types<64>::Elf_Addr,
unsigned char* view,
section_size_type view_size)
{
// leaq foo@tlsld(%rip),%rdi; call __tls_get_addr@plt;
// ... leq foo@dtpoff(%rax),%reg
// ==> .word 0x6666; .byte 0x66; movq %fs:0,%rax ... leaq x@tpoff(%rax),%rdx
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, -3);
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, 9);
tls::check_tls(relinfo, relnum, rela.get_r_offset(),
view[-3] == 0x48 && view[-2] == 0x8d && view[-1] == 0x3d);
tls::check_tls(relinfo, relnum, rela.get_r_offset(), view[4] == 0xe8);
memcpy(view - 3, "\x66\x66\x66\x64\x48\x8b\x04\x25\0\0\0\0", 12);
// The next reloc should be a PLT32 reloc against __tls_get_addr.
// We can skip it.
this->skip_call_tls_get_addr_ = true;
}
// Do a relocation in which we convert a TLS Initial-Exec to a
// Local-Exec.
inline void
Target_x86_64::Relocate::tls_ie_to_le(const Relocate_info<64, false>* relinfo,
size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rela<64, false>& rela,
unsigned int,
elfcpp::Elf_types<64>::Elf_Addr value,
unsigned char* view,
section_size_type view_size)
{
// We need to examine the opcodes to figure out which instruction we
// are looking at.
// movq foo@gottpoff(%rip),%reg ==> movq $YY,%reg
// addq foo@gottpoff(%rip),%reg ==> addq $YY,%reg
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, -3);
tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, 4);
unsigned char op1 = view[-3];
unsigned char op2 = view[-2];
unsigned char op3 = view[-1];
unsigned char reg = op3 >> 3;
if (op2 == 0x8b)
{
// movq
if (op1 == 0x4c)
view[-3] = 0x49;
view[-2] = 0xc7;
view[-1] = 0xc0 | reg;
}
else if (reg == 4)
{
// Special handling for %rsp.
if (op1 == 0x4c)
view[-3] = 0x49;
view[-2] = 0x81;
view[-1] = 0xc0 | reg;
}
else
{
// addq
if (op1 == 0x4c)
view[-3] = 0x4d;
view[-2] = 0x8d;
view[-1] = 0x80 | reg | (reg << 3);
}
value -= tls_segment->memsz();
Relocate_functions<64, false>::rela32(view, value, 0);
}
// Relocate section data.
void
Target_x86_64::relocate_section(
const Relocate_info<64, false>* relinfo,
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<64>::Elf_Addr address,
section_size_type view_size,
const Reloc_symbol_changes* reloc_symbol_changes)
{
gold_assert(sh_type == elfcpp::SHT_RELA);
gold::relocate_section<64, false, Target_x86_64, elfcpp::SHT_RELA,
Target_x86_64::Relocate>(
relinfo,
this,
prelocs,
reloc_count,
output_section,
needs_special_offset_handling,
view,
address,
view_size,
reloc_symbol_changes);
}
// Return the size of a relocation while scanning during a relocatable
// link.
unsigned int
Target_x86_64::Relocatable_size_for_reloc::get_size_for_reloc(
unsigned int r_type,
Relobj* object)
{
switch (r_type)
{
case elfcpp::R_X86_64_NONE:
case elfcpp::R_386_GNU_VTINHERIT:
case elfcpp::R_386_GNU_VTENTRY:
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 0;
case elfcpp::R_X86_64_64:
case elfcpp::R_X86_64_PC64:
case elfcpp::R_X86_64_GOTOFF64:
case elfcpp::R_X86_64_GOTPC64:
case elfcpp::R_X86_64_PLTOFF64:
case elfcpp::R_X86_64_GOT64:
case elfcpp::R_X86_64_GOTPCREL64:
case elfcpp::R_X86_64_GOTPCREL:
case elfcpp::R_X86_64_GOTPLT64:
return 8;
case elfcpp::R_X86_64_32:
case elfcpp::R_X86_64_32S:
case elfcpp::R_X86_64_PC32:
case elfcpp::R_X86_64_PLT32:
case elfcpp::R_X86_64_GOTPC32:
case elfcpp::R_X86_64_GOT32:
return 4;
case elfcpp::R_X86_64_16:
case elfcpp::R_X86_64_PC16:
return 2;
case elfcpp::R_X86_64_8:
case elfcpp::R_X86_64_PC8:
return 1;
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:
// 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:
object->error(_("unexpected reloc %u in object file"), r_type);
return 0;
case elfcpp::R_X86_64_SIZE32:
case elfcpp::R_X86_64_SIZE64:
default:
object->error(_("unsupported reloc %u against local symbol"), r_type);
return 0;
}
}
// Scan the relocs during a relocatable link.
void
Target_x86_64::scan_relocatable_relocs(Symbol_table* symtab,
Layout* layout,
Sized_relobj<64, 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* rr)
{
gold_assert(sh_type == elfcpp::SHT_RELA);
typedef gold::Default_scan_relocatable_relocs<elfcpp::SHT_RELA,
Relocatable_size_for_reloc> Scan_relocatable_relocs;
gold::scan_relocatable_relocs<64, false, elfcpp::SHT_RELA,
Scan_relocatable_relocs>(
symtab,
layout,
object,
data_shndx,
prelocs,
reloc_count,
output_section,
needs_special_offset_handling,
local_symbol_count,
plocal_symbols,
rr);
}
// Relocate a section during a relocatable link.
void
Target_x86_64::relocate_for_relocatable(
const Relocate_info<64, false>* relinfo,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
Output_section* output_section,
off_t offset_in_output_section,
const Relocatable_relocs* rr,
unsigned char* view,
elfcpp::Elf_types<64>::Elf_Addr view_address,
section_size_type view_size,
unsigned char* reloc_view,
section_size_type reloc_view_size)
{
gold_assert(sh_type == elfcpp::SHT_RELA);
gold::relocate_for_relocatable<64, false, elfcpp::SHT_RELA>(
relinfo,
prelocs,
reloc_count,
output_section,
offset_in_output_section,
rr,
view,
view_address,
view_size,
reloc_view,
reloc_view_size);
}
// Return the value to use for a dynamic which requires special
// treatment. This is how we support equality comparisons of function
// pointers across shared library boundaries, as described in the
// processor specific ABI supplement.
uint64_t
Target_x86_64::do_dynsym_value(const Symbol* gsym) const
{
gold_assert(gsym->is_from_dynobj() && gsym->has_plt_offset());
return this->plt_section()->address() + gsym->plt_offset();
}
// Return a string used to fill a code section with nops to take up
// the specified length.
std::string
Target_x86_64::do_code_fill(section_size_type length) const
{
if (length >= 16)
{
// Build a jmpq instruction to skip over the bytes.
unsigned char jmp[5];
jmp[0] = 0xe9;
elfcpp::Swap_unaligned<32, false>::writeval(jmp + 1, length - 5);
return (std::string(reinterpret_cast<char*>(&jmp[0]), 5)
+ std::string(length - 5, '\0'));
}
// Nop sequences of various lengths.
const char nop1[1] = { 0x90 }; // nop
const char nop2[2] = { 0x66, 0x90 }; // xchg %ax %ax
const char nop3[3] = { 0x0f, 0x1f, 0x00 }; // nop (%rax)
const char nop4[4] = { 0x0f, 0x1f, 0x40, 0x00}; // nop 0(%rax)
const char nop5[5] = { 0x0f, 0x1f, 0x44, 0x00, // nop 0(%rax,%rax,1)
0x00 };
const char nop6[6] = { 0x66, 0x0f, 0x1f, 0x44, // nopw 0(%rax,%rax,1)
0x00, 0x00 };
const char nop7[7] = { 0x0f, 0x1f, 0x80, 0x00, // nopl 0L(%rax)
0x00, 0x00, 0x00 };
const char nop8[8] = { 0x0f, 0x1f, 0x84, 0x00, // nopl 0L(%rax,%rax,1)
0x00, 0x00, 0x00, 0x00 };
const char nop9[9] = { 0x66, 0x0f, 0x1f, 0x84, // nopw 0L(%rax,%rax,1)
0x00, 0x00, 0x00, 0x00,
0x00 };
const char nop10[10] = { 0x66, 0x2e, 0x0f, 0x1f, // nopw %cs:0L(%rax,%rax,1)
0x84, 0x00, 0x00, 0x00,
0x00, 0x00 };
const char nop11[11] = { 0x66, 0x66, 0x2e, 0x0f, // data16
0x1f, 0x84, 0x00, 0x00, // nopw %cs:0L(%rax,%rax,1)
0x00, 0x00, 0x00 };
const char nop12[12] = { 0x66, 0x66, 0x66, 0x2e, // data16; data16
0x0f, 0x1f, 0x84, 0x00, // nopw %cs:0L(%rax,%rax,1)
0x00, 0x00, 0x00, 0x00 };
const char nop13[13] = { 0x66, 0x66, 0x66, 0x66, // data16; data16; data16
0x2e, 0x0f, 0x1f, 0x84, // nopw %cs:0L(%rax,%rax,1)
0x00, 0x00, 0x00, 0x00,
0x00 };
const char nop14[14] = { 0x66, 0x66, 0x66, 0x66, // data16; data16; data16
0x66, 0x2e, 0x0f, 0x1f, // data16
0x84, 0x00, 0x00, 0x00, // nopw %cs:0L(%rax,%rax,1)
0x00, 0x00 };
const char nop15[15] = { 0x66, 0x66, 0x66, 0x66, // data16; data16; data16
0x66, 0x66, 0x2e, 0x0f, // data16; data16
0x1f, 0x84, 0x00, 0x00, // nopw %cs:0L(%rax,%rax,1)
0x00, 0x00, 0x00 };
const char* nops[16] = {
NULL,
nop1, nop2, nop3, nop4, nop5, nop6, nop7,
nop8, nop9, nop10, nop11, nop12, nop13, nop14, nop15
};
return std::string(nops[length], length);
}
// Return the addend to use for a target specific relocation. The
// only target specific relocation is R_X86_64_TLSDESC for a local
// symbol. We want to set the addend is the offset of the local
// symbol in the TLS segment.
uint64_t
Target_x86_64::do_reloc_addend(void* arg, unsigned int r_type,
uint64_t) const
{
gold_assert(r_type == elfcpp::R_X86_64_TLSDESC);
uintptr_t intarg = reinterpret_cast<uintptr_t>(arg);
gold_assert(intarg < this->tlsdesc_reloc_info_.size());
const Tlsdesc_info& ti(this->tlsdesc_reloc_info_[intarg]);
const Symbol_value<64>* psymval = ti.object->local_symbol(ti.r_sym);
gold_assert(psymval->is_tls_symbol());
// The value of a TLS symbol is the offset in the TLS segment.
return psymval->value(ti.object, 0);
}
// FNOFFSET in section SHNDX in OBJECT is the start of a function
// compiled with -fstack-split. The function calls non-stack-split
// code. We have to change the function so that it always ensures
// that it has enough stack space to run some random function.
void
Target_x86_64::do_calls_non_split(Relobj* object, unsigned int shndx,
section_offset_type fnoffset,
section_size_type fnsize,
unsigned char* view,
section_size_type view_size,
std::string* from,
std::string* to) const
{
// The function starts with a comparison of the stack pointer and a
// field in the TCB. This is followed by a jump.
// cmp %fs:NN,%rsp
if (this->match_view(view, view_size, fnoffset, "\x64\x48\x3b\x24\x25", 5)
&& fnsize > 9)
{
// We will call __morestack if the carry flag is set after this
// comparison. We turn the comparison into an stc instruction
// and some nops.
view[fnoffset] = '\xf9';
this->set_view_to_nop(view, view_size, fnoffset + 1, 8);
}
// lea NN(%rsp),%r10
// lea NN(%rsp),%r11
else if ((this->match_view(view, view_size, fnoffset,
"\x4c\x8d\x94\x24", 4)
|| this->match_view(view, view_size, fnoffset,
"\x4c\x8d\x9c\x24", 4))
&& fnsize > 8)
{
// This is loading an offset from the stack pointer for a
// comparison. The offset is negative, so we decrease the
// offset by the amount of space we need for the stack. This
// means we will avoid calling __morestack if there happens to
// be plenty of space on the stack already.
unsigned char* pval = view + fnoffset + 4;
uint32_t val = elfcpp::Swap_unaligned<32, false>::readval(pval);
val -= parameters->options().split_stack_adjust_size();
elfcpp::Swap_unaligned<32, false>::writeval(pval, val);
}
else
{
if (!object->has_no_split_stack())
object->error(_("failed to match split-stack sequence at "
"section %u offset %0zx"),
shndx, static_cast<size_t>(fnoffset));
return;
}
// We have to change the function so that it calls
// __morestack_non_split instead of __morestack. The former will
// allocate additional stack space.
*from = "__morestack";
*to = "__morestack_non_split";
}
// The selector for x86_64 object files.
class Target_selector_x86_64 : public Target_selector_freebsd
{
public:
Target_selector_x86_64()
: Target_selector_freebsd(elfcpp::EM_X86_64, 64, false, "elf64-x86-64",
"elf64-x86-64-freebsd")
{ }
Target*
do_instantiate_target()
{ return new Target_x86_64(); }
};
Target_selector_x86_64 target_selector_x86_64;
} // End anonymous namespace.
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