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binutils-gdb/gold/arm.cc

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// arm.cc -- arm target support for gold.
// Copyright 2009 Free Software Foundation, Inc.
// Written by Doug Kwan <dougkwan@google.com> based on the i386 code
// 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 <limits>
#include <cstdio>
#include <string>
#include "elfcpp.h"
#include "parameters.h"
#include "reloc.h"
#include "arm.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 "defstd.h"
namespace
{
using namespace gold;
template<bool big_endian>
class Output_data_plt_arm;
// The arm target class.
//
// This is a very simple port of gold for ARM-EABI. It is intended for
// supporting Android only for the time being. Only these relocation types
// are supported.
//
// R_ARM_NONE
// R_ARM_ABS32
// R_ARM_REL32
// R_ARM_THM_CALL
// R_ARM_COPY
// R_ARM_GLOB_DAT
// R_ARM_BASE_PREL
// R_ARM_JUMP_SLOT
// R_ARM_RELATIVE
// R_ARM_GOTOFF32
// R_ARM_GOT_BREL
// R_ARM_PLT32
// R_ARM_CALL
// R_ARM_JUMP24
// R_ARM_TARGET1
// R_ARM_PREL31
//
// Coming soon (pending patches):
// - Relocation
// - Defining section symbols __exidx_start and __exidx_stop.
// - Support interworking.
// - Mergeing all .ARM.xxx.yyy sections into .ARM.xxx. Currently, they
// are incorrectly merged into an .ARM section.
//
// TODOs:
// - Create a PT_ARM_EXIDX program header for a shared object that
// might throw an exception.
// - Support more relocation types as needed.
// - Make PLTs more flexible for different architecture features like
// Thumb-2 and BE8.
template<bool big_endian>
class Target_arm : public Sized_target<32, big_endian>
{
public:
typedef Output_data_reloc<elfcpp::SHT_REL, true, 32, big_endian>
Reloc_section;
Target_arm()
: Sized_target<32, big_endian>(&arm_info),
got_(NULL), plt_(NULL), got_plt_(NULL), rel_dyn_(NULL),
copy_relocs_(elfcpp::R_ARM_COPY), dynbss_(NULL)
{ }
// Process the relocations to determine unreferenced sections for
// garbage collection.
void
gc_process_relocs(const General_options& options,
Symbol_table* symtab,
Layout* layout,
Sized_relobj<32, big_endian>* 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(const General_options& options,
Symbol_table* symtab,
Layout* layout,
Sized_relobj<32, big_endian>* 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*);
// Return the value to use for a dynamic symbol which requires special
// treatment.
uint64_t
do_dynsym_value(const Symbol*) const;
// Relocate a section.
void
relocate_section(const Relocate_info<32, big_endian>*,
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);
// Scan the relocs during a relocatable link.
void
scan_relocatable_relocs(const General_options& options,
Symbol_table* symtab,
Layout* layout,
Sized_relobj<32, big_endian>* 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<32, big_endian>*,
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<32>::Elf_Addr view_address,
section_size_type view_size,
unsigned char* reloc_view,
section_size_type reloc_view_size);
// Return whether SYM is defined by the ABI.
bool
do_is_defined_by_abi(Symbol* sym) const
{ return strcmp(sym->name(), "__tls_get_addr") == 0; }
// Return the size of the GOT section.
section_size_type
got_size()
{
gold_assert(this->got_ != NULL);
return this->got_->data_size();
}
// Map platform-specific reloc types
static unsigned int
get_real_reloc_type (unsigned int r_type);
private:
// The class which scans relocations.
class Scan
{
public:
Scan()
: issued_non_pic_error_(false)
{ }
inline void
local(const General_options& options, Symbol_table* symtab,
Layout* layout, Target_arm* target,
Sized_relobj<32, big_endian>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rel<32, big_endian>& reloc, unsigned int r_type,
const elfcpp::Sym<32, big_endian>& lsym);
inline void
global(const General_options& options, Symbol_table* symtab,
Layout* layout, Target_arm* target,
Sized_relobj<32, big_endian>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rel<32, big_endian>& reloc, unsigned int r_type,
Symbol* gsym);
private:
static void
unsupported_reloc_local(Sized_relobj<32, big_endian>*,
unsigned int r_type);
static void
unsupported_reloc_global(Sized_relobj<32, big_endian>*,
unsigned int r_type, Symbol*);
void
check_non_pic(Relobj*, unsigned int r_type);
// Almost identical to Symbol::needs_plt_entry except that it also
// handles STT_ARM_TFUNC.
static bool
symbol_needs_plt_entry(const Symbol* sym)
{
// An undefined symbol from an executable does not need a PLT entry.
if (sym->is_undefined() && !parameters->options().shared())
return false;
return (!parameters->doing_static_link()
&& (sym->type() == elfcpp::STT_FUNC
|| sym->type() == elfcpp::STT_ARM_TFUNC)
&& (sym->is_from_dynobj()
|| sym->is_undefined()
|| sym->is_preemptible()));
}
// 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()
{ }
~Relocate()
{ }
// Return whether the static relocation needs to be applied.
inline bool
should_apply_static_reloc(const Sized_symbol<32>* gsym,
int ref_flags,
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, big_endian>*, Target_arm*,
Output_section*, size_t relnum,
const elfcpp::Rel<32, big_endian>&,
unsigned int r_type, const Sized_symbol<32>*,
const Symbol_value<32>*,
unsigned char*, elfcpp::Elf_types<32>::Elf_Addr,
section_size_type);
};
// 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*);
};
// Get the GOT section, creating it if necessary.
Output_data_got<32, big_endian>*
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 a PLT entry for a global symbol.
void
make_plt_entry(Symbol_table*, Layout*, Symbol*);
// Get the PLT section.
const Output_data_plt_arm<big_endian>*
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*);
// Return true if the symbol may need a COPY relocation.
// References from an executable object to non-function symbols
// defined in a dynamic object may need a COPY relocation.
bool
may_need_copy_reloc(Symbol* gsym)
{
return (!parameters->options().shared()
&& gsym->is_from_dynobj()
&& gsym->type() != elfcpp::STT_FUNC
&& gsym->type() != elfcpp::STT_ARM_TFUNC);
}
// Add a potential copy relocation.
void
copy_reloc(Symbol_table* symtab, Layout* layout,
Sized_relobj<32, big_endian>* object,
unsigned int shndx, Output_section* output_section,
Symbol* sym, const elfcpp::Rel<32, big_endian>& reloc)
{
this->copy_relocs_.copy_reloc(symtab, layout,
symtab->get_sized_symbol<32>(sym),
object, shndx, output_section, reloc,
this->rel_dyn_section(layout));
}
// Information about this specific target which we pass to the
// general Target structure.
static const Target::Target_info arm_info;
// The types of GOT entries needed for this platform.
enum Got_type
{
GOT_TYPE_STANDARD = 0 // GOT entry for a regular symbol
};
// The GOT section.
Output_data_got<32, big_endian>* got_;
// The PLT section.
Output_data_plt_arm<big_endian>* plt_;
// The GOT PLT section.
Output_data_space* got_plt_;
// The dynamic reloc section.
Reloc_section* rel_dyn_;
// Relocs saved to avoid a COPY reloc.
Copy_relocs<elfcpp::SHT_REL, 32, big_endian> copy_relocs_;
// Space for variables copied with a COPY reloc.
Output_data_space* dynbss_;
};
template<bool big_endian>
const Target::Target_info Target_arm<big_endian>::arm_info =
{
32, // size
big_endian, // is_big_endian
elfcpp::EM_ARM, // machine_code
false, // has_make_symbol
false, // has_resolve
false, // has_code_fill
true, // is_default_stack_executable
'\0', // wrap_char
"/usr/lib/libc.so.1", // dynamic_linker
0x8000, // default_text_segment_address
0x1000, // abi_pagesize (overridable by -z max-page-size)
0x1000 // common_pagesize (overridable by -z common-page-size)
};
// Get the GOT section, creating it if necessary.
template<bool big_endian>
Output_data_got<32, big_endian>*
Target_arm<big_endian>::got_section(Symbol_table* symtab, Layout* layout)
{
if (this->got_ == NULL)
{
gold_assert(symtab != NULL && layout != NULL);
this->got_ = new Output_data_got<32, big_endian>();
Output_section* os;
os = layout->add_output_section_data(".got", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_WRITE),
this->got_);
os->set_is_relro();
// The old GNU linker creates a .got.plt section. We just
// create another set of data in the .got section. Note that we
// always create a PLT if we create a GOT, although the PLT
// might be empty.
this->got_plt_ = new Output_data_space(4, "** GOT PLT");
os = layout->add_output_section_data(".got", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_WRITE),
this->got_plt_);
os->set_is_relro();
// The first three entries are reserved.
this->got_plt_->set_current_data_size(3 * 4);
// Define _GLOBAL_OFFSET_TABLE_ at the start of the PLT.
symtab->define_in_output_data("_GLOBAL_OFFSET_TABLE_", NULL,
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.
template<bool big_endian>
typename Target_arm<big_endian>::Reloc_section*
Target_arm<big_endian>::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_);
}
return this->rel_dyn_;
}
// A class to handle the PLT data.
template<bool big_endian>
class Output_data_plt_arm : public Output_section_data
{
public:
typedef Output_data_reloc<elfcpp::SHT_REL, true, 32, big_endian>
Reloc_section;
Output_data_plt_arm(Layout*, Output_data_space*);
// Add an entry to the PLT.
void
add_entry(Symbol* gsym);
// Return the .rel.plt section data.
const Reloc_section*
rel_plt() const
{ return this->rel_; }
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:
// Template for the first PLT entry.
static const uint32_t first_plt_entry[5];
// Template for subsequent PLT entries.
static const uint32_t plt_entry[3];
// Set the final size.
void
set_final_data_size()
{
this->set_data_size(sizeof(first_plt_entry)
+ this->count_ * sizeof(plt_entry));
}
// Write out the PLT data.
void
do_write(Output_file*);
// The reloc section.
Reloc_section* rel_;
// The .got.plt section.
Output_data_space* got_plt_;
// The number of PLT entries.
unsigned int count_;
};
// 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.
template<bool big_endian>
Output_data_plt_arm<big_endian>::Output_data_plt_arm(Layout* layout,
Output_data_space* got_plt)
: Output_section_data(4), got_plt_(got_plt), count_(0)
{
this->rel_ = new Reloc_section(false);
layout->add_output_section_data(".rel.plt", elfcpp::SHT_REL,
elfcpp::SHF_ALLOC, this->rel_);
}
template<bool big_endian>
void
Output_data_plt_arm<big_endian>::do_adjust_output_section(Output_section* os)
{
os->set_entsize(0);
}
// Add an entry to the PLT.
template<bool big_endian>
void
Output_data_plt_arm<big_endian>::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_) * sizeof(plt_entry)
+ sizeof(first_plt_entry));
++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);
// Every PLT entry needs a reloc.
gsym->set_needs_dynsym_entry();
this->rel_->add_global(gsym, elfcpp::R_ARM_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.
}
// ARM PLTs.
// FIXME: This is not very flexible. Right now this has only been tested
// on armv5te. If we are to support additional architecture features like
// Thumb-2 or BE8, we need to make this more flexible like GNU ld.
// The first entry in the PLT.
template<bool big_endian>
const uint32_t Output_data_plt_arm<big_endian>::first_plt_entry[5] =
{
0xe52de004, // str lr, [sp, #-4]!
0xe59fe004, // ldr lr, [pc, #4]
0xe08fe00e, // add lr, pc, lr
0xe5bef008, // ldr pc, [lr, #8]!
0x00000000, // &GOT[0] - .
};
// Subsequent entries in the PLT.
template<bool big_endian>
const uint32_t Output_data_plt_arm<big_endian>::plt_entry[3] =
{
0xe28fc600, // add ip, pc, #0xNN00000
0xe28cca00, // add ip, ip, #0xNN000
0xe5bcf000, // ldr pc, [ip, #0xNNN]!
};
// Write out the PLT. This uses the hand-coded instructions above,
// and adjusts them as needed. This is all specified by the arm ELF
// Processor Supplement.
template<bool big_endian>
void
Output_data_plt_arm<big_endian>::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;
elfcpp::Elf_types<32>::Elf_Addr plt_address = this->address();
elfcpp::Elf_types<32>::Elf_Addr got_address = this->got_plt_->address();
// Write first PLT entry. All but the last word are constants.
const size_t num_first_plt_words = (sizeof(first_plt_entry)
/ sizeof(plt_entry[0]));
for (size_t i = 0; i < num_first_plt_words - 1; i++)
elfcpp::Swap<32, big_endian>::writeval(pov + i * 4, first_plt_entry[i]);
// Last word in first PLT entry is &GOT[0] - .
elfcpp::Swap<32, big_endian>::writeval(pov + 16,
got_address - (plt_address + 16));
pov += sizeof(first_plt_entry);
unsigned char* got_pov = got_view;
memset(got_pov, 0, 12);
got_pov += 12;
const int rel_size = elfcpp::Elf_sizes<32>::rel_size;
unsigned int plt_offset = sizeof(first_plt_entry);
unsigned int plt_rel_offset = 0;
unsigned int got_offset = 12;
const unsigned int count = this->count_;
for (unsigned int i = 0;
i < count;
++i,
pov += sizeof(plt_entry),
got_pov += 4,
plt_offset += sizeof(plt_entry),
plt_rel_offset += rel_size,
got_offset += 4)
{
// Set and adjust the PLT entry itself.
int32_t offset = ((got_address + got_offset)
- (plt_address + plt_offset + 8));
gold_assert(offset >= 0 && offset < 0x0fffffff);
uint32_t plt_insn0 = plt_entry[0] | ((offset >> 20) & 0xff);
elfcpp::Swap<32, big_endian>::writeval(pov, plt_insn0);
uint32_t plt_insn1 = plt_entry[1] | ((offset >> 12) & 0xff);
elfcpp::Swap<32, big_endian>::writeval(pov + 4, plt_insn1);
uint32_t plt_insn2 = plt_entry[2] | (offset & 0xfff);
elfcpp::Swap<32, big_endian>::writeval(pov + 8, plt_insn2);
// Set the entry in the GOT.
elfcpp::Swap<32, big_endian>::writeval(got_pov, plt_address);
}
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 a PLT entry for a global symbol.
template<bool big_endian>
void
Target_arm<big_endian>::make_plt_entry(Symbol_table* symtab, Layout* layout,
Symbol* gsym)
{
if (gsym->has_plt_offset())
return;
if (this->plt_ == NULL)
{
// Create the GOT sections first.
this->got_section(symtab, layout);
this->plt_ = new Output_data_plt_arm<big_endian>(layout, this->got_plt_);
layout->add_output_section_data(".plt", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_EXECINSTR),
this->plt_);
}
this->plt_->add_entry(gsym);
}
// Report an unsupported relocation against a local symbol.
template<bool big_endian>
void
Target_arm<big_endian>::Scan::unsupported_reloc_local(
Sized_relobj<32, big_endian>* 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.
template<bool big_endian>
void
Target_arm<big_endian>::Scan::check_non_pic(Relobj* object,
unsigned int r_type)
{
switch (r_type)
{
// These are the relocation types supported by glibc for ARM.
case elfcpp::R_ARM_RELATIVE:
case elfcpp::R_ARM_COPY:
case elfcpp::R_ARM_GLOB_DAT:
case elfcpp::R_ARM_JUMP_SLOT:
case elfcpp::R_ARM_ABS32:
case elfcpp::R_ARM_PC24:
// FIXME: The following 3 types are not supported by Android's dynamic
// linker.
case elfcpp::R_ARM_TLS_DTPMOD32:
case elfcpp::R_ARM_TLS_DTPOFF32:
case elfcpp::R_ARM_TLS_TPOFF32:
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;
object->error(_("requires unsupported dynamic reloc; "
"recompile with -fPIC"));
this->issued_non_pic_error_ = true;
return;
case elfcpp::R_ARM_NONE:
gold_unreachable();
}
}
// Scan a relocation for a local symbol.
// FIXME: This only handles a subset of relocation types used by Android
// on ARM v5te devices.
template<bool big_endian>
inline void
Target_arm<big_endian>::Scan::local(const General_options&,
Symbol_table* symtab,
Layout* layout,
Target_arm* target,
Sized_relobj<32, big_endian>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rel<32, big_endian>& reloc,
unsigned int r_type,
const elfcpp::Sym<32, big_endian>&)
{
r_type = get_real_reloc_type(r_type);
switch (r_type)
{
case elfcpp::R_ARM_NONE:
break;
case elfcpp::R_ARM_ABS32:
// 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_ARM_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());
// If we are to add more other reloc types than R_ARM_ABS32,
// we need to add check_non_pic(object, r_type) here.
rel_dyn->add_local_relative(object, r_sym, elfcpp::R_ARM_RELATIVE,
output_section, data_shndx,
reloc.get_r_offset());
}
break;
case elfcpp::R_ARM_REL32:
case elfcpp::R_ARM_THM_CALL:
case elfcpp::R_ARM_CALL:
case elfcpp::R_ARM_PREL31:
case elfcpp::R_ARM_JUMP24:
case elfcpp::R_ARM_PLT32:
break;
case elfcpp::R_ARM_GOTOFF32:
// We need a GOT section:
target->got_section(symtab, layout);
break;
case elfcpp::R_ARM_BASE_PREL:
// FIXME: What about this?
break;
case elfcpp::R_ARM_GOT_BREL:
{
// The symbol requires a GOT entry.
Output_data_got<32, big_endian>* got =
target->got_section(symtab, layout);
unsigned int r_sym = elfcpp::elf_r_sym<32>(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 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 r_sym = elfcpp::elf_r_sym<32>(reloc.get_r_info());
rel_dyn->add_local_relative(
object, r_sym, elfcpp::R_ARM_RELATIVE, got,
object->local_got_offset(r_sym, GOT_TYPE_STANDARD));
}
}
}
break;
case elfcpp::R_ARM_TARGET1:
// This should have been mapped to another type already.
// Fall through.
case elfcpp::R_ARM_COPY:
case elfcpp::R_ARM_GLOB_DAT:
case elfcpp::R_ARM_JUMP_SLOT:
case elfcpp::R_ARM_RELATIVE:
// These are relocations which should only be seen by the
// dynamic linker, and should never be seen here.
gold_error(_("%s: unexpected reloc %u in object file"),
object->name().c_str(), r_type);
break;
default:
unsupported_reloc_local(object, r_type);
break;
}
}
// Report an unsupported relocation against a global symbol.
template<bool big_endian>
void
Target_arm<big_endian>::Scan::unsupported_reloc_global(
Sized_relobj<32, big_endian>* 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());
}
// Scan a relocation for a global symbol.
// FIXME: This only handles a subset of relocation types used by Android
// on ARM v5te devices.
template<bool big_endian>
inline void
Target_arm<big_endian>::Scan::global(const General_options&,
Symbol_table* symtab,
Layout* layout,
Target_arm* target,
Sized_relobj<32, big_endian>* object,
unsigned int data_shndx,
Output_section* output_section,
const elfcpp::Rel<32, big_endian>& reloc,
unsigned int r_type,
Symbol* gsym)
{
r_type = get_real_reloc_type(r_type);
switch (r_type)
{
case elfcpp::R_ARM_NONE:
break;
case elfcpp::R_ARM_ABS32:
{
// Make a dynamic relocation if necessary.
if (gsym->needs_dynamic_reloc(Symbol::ABSOLUTE_REF))
{
if (target->may_need_copy_reloc(gsym))
{
target->copy_reloc(symtab, layout, object,
data_shndx, output_section, gsym, reloc);
}
else if (gsym->can_use_relative_reloc(false))
{
// If we are to add more other reloc types than R_ARM_ABS32,
// we need to add check_non_pic(object, r_type) here.
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
rel_dyn->add_global_relative(gsym, elfcpp::R_ARM_RELATIVE,
output_section, object,
data_shndx, reloc.get_r_offset());
}
else
{
// If we are to add more other reloc types than R_ARM_ABS32,
// we need to add check_non_pic(object, r_type) here.
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_ARM_REL32:
case elfcpp::R_ARM_PREL31:
{
// Make a dynamic relocation if necessary.
int flags = Symbol::NON_PIC_REF;
if (gsym->needs_dynamic_reloc(flags))
{
if (target->may_need_copy_reloc(gsym))
{
target->copy_reloc(symtab, layout, object,
data_shndx, output_section, gsym, reloc);
}
else
{
check_non_pic(object, r_type);
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_ARM_JUMP24:
case elfcpp::R_ARM_THM_CALL:
case elfcpp::R_ARM_CALL:
{
if (Target_arm<big_endian>::Scan::symbol_needs_plt_entry(gsym))
target->make_plt_entry(symtab, layout, gsym);
// Make a dynamic relocation if necessary.
int flags = Symbol::NON_PIC_REF;
if (gsym->type() == elfcpp::STT_FUNC
|| gsym->type() == elfcpp::STT_ARM_TFUNC)
flags |= Symbol::FUNCTION_CALL;
if (gsym->needs_dynamic_reloc(flags))
{
if (target->may_need_copy_reloc(gsym))
{
target->copy_reloc(symtab, layout, object,
data_shndx, output_section, gsym,
reloc);
}
else
{
check_non_pic(object, r_type);
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_ARM_PLT32:
// If the symbol is fully resolved, this is just a relative
// local 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_ARM_GOTOFF32:
// We need a GOT section.
target->got_section(symtab, layout);
break;
case elfcpp::R_ARM_BASE_PREL:
// FIXME: What about this?
break;
case elfcpp::R_ARM_GOT_BREL:
{
// The symbol requires a GOT entry.
Output_data_got<32, big_endian>* 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
// GOT entry with a dynamic relocation.
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
if (gsym->is_from_dynobj()
|| gsym->is_undefined()
|| gsym->is_preemptible())
got->add_global_with_rel(gsym, GOT_TYPE_STANDARD,
rel_dyn, elfcpp::R_ARM_GLOB_DAT);
else
{
if (got->add_global(gsym, GOT_TYPE_STANDARD))
rel_dyn->add_global_relative(
gsym, elfcpp::R_ARM_RELATIVE, got,
gsym->got_offset(GOT_TYPE_STANDARD));
}
}
}
break;
case elfcpp::R_ARM_TARGET1:
// This should have been mapped to another type already.
// Fall through.
case elfcpp::R_ARM_COPY:
case elfcpp::R_ARM_GLOB_DAT:
case elfcpp::R_ARM_JUMP_SLOT:
case elfcpp::R_ARM_RELATIVE:
// These are relocations which should only be seen by the
// dynamic linker, and should never be seen here.
gold_error(_("%s: unexpected reloc %u in object file"),
object->name().c_str(), r_type);
break;
default:
unsupported_reloc_global(object, r_type, gsym);
break;
}
}
// Process relocations for gc.
template<bool big_endian>
void
Target_arm<big_endian>::gc_process_relocs(const General_options& options,
Symbol_table* symtab,
Layout* layout,
Sized_relobj<32, big_endian>* 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)
{
typedef Target_arm<big_endian> Arm;
typedef typename Target_arm<big_endian>::Scan Scan;
gold::gc_process_relocs<32, big_endian, Arm, elfcpp::SHT_REL, Scan>(
options,
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.
template<bool big_endian>
void
Target_arm<big_endian>::scan_relocs(const General_options& options,
Symbol_table* symtab,
Layout* layout,
Sized_relobj<32, big_endian>* 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)
{
typedef typename Target_arm<big_endian>::Scan Scan;
if (sh_type == elfcpp::SHT_RELA)
{
gold_error(_("%s: unsupported RELA reloc section"),
object->name().c_str());
return;
}
gold::scan_relocs<32, big_endian, Target_arm, elfcpp::SHT_REL, Scan>(
options,
symtab,
layout,
this,
object,
data_shndx,
prelocs,
reloc_count,
output_section,
needs_special_offset_handling,
local_symbol_count,
plocal_symbols);
}
// Finalize the sections.
template<bool big_endian>
void
Target_arm<big_endian>::do_finalize_sections(Layout* layout)
{
// Fill in some more dynamic tags.
Output_data_dynamic* const odyn = layout->dynamic_data();
if (odyn != NULL)
{
if (this->got_plt_ != NULL)
odyn->add_section_address(elfcpp::DT_PLTGOT, this->got_plt_);
if (this->plt_ != NULL)
{
const Output_data* od = this->plt_->rel_plt();
odyn->add_section_size(elfcpp::DT_PLTRELSZ, od);
odyn->add_section_address(elfcpp::DT_JMPREL, od);
odyn->add_constant(elfcpp::DT_PLTREL, elfcpp::DT_REL);
}
if (this->rel_dyn_ != NULL)
{
const Output_data* od = this->rel_dyn_;
odyn->add_section_address(elfcpp::DT_REL, od);
odyn->add_section_size(elfcpp::DT_RELSZ, od);
odyn->add_constant(elfcpp::DT_RELENT,
elfcpp::Elf_sizes<32>::rel_size);
}
if (!parameters->options().shared())
{
// The value of the DT_DEBUG tag is filled in by the dynamic
// linker at run time, and used by the debugger.
odyn->add_constant(elfcpp::DT_DEBUG, 0);
}
}
// 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));
}
// Return whether a direct absolute static relocation needs to be applied.
// In cases where Scan::local() or Scan::global() has created
// a dynamic relocation other than R_ARM_RELATIVE, the addend
// of the relocation is carried in the data, and we must not
// apply the static relocation.
template<bool big_endian>
inline bool
Target_arm<big_endian>::Relocate::should_apply_static_reloc(
const Sized_symbol<32>* gsym,
int ref_flags,
bool is_32bit,
Output_section* output_section)
{
// If the output section is not allocated, then we didn't call
// scan_relocs, we didn't create a dynamic reloc, and we must apply
// the reloc here.
if ((output_section->flags() & elfcpp::SHF_ALLOC) == 0)
return true;
// For local symbols, we will have created a non-RELATIVE dynamic
// relocation only if (a) the output is position independent,
// (b) the relocation is absolute (not pc- or segment-relative), and
// (c) the relocation is not 32 bits wide.
if (gsym == NULL)
return !(parameters->options().output_is_position_independent()
&& (ref_flags & Symbol::ABSOLUTE_REF)
&& !is_32bit);
// For global symbols, we use the same helper routines used in the
// scan pass. If we did not create a dynamic relocation, or if we
// created a RELATIVE dynamic relocation, we should apply the static
// relocation.
bool has_dyn = gsym->needs_dynamic_reloc(ref_flags);
bool is_rel = (ref_flags & Symbol::ABSOLUTE_REF)
&& gsym->can_use_relative_reloc(ref_flags
& Symbol::FUNCTION_CALL);
return !has_dyn || is_rel;
}
// Perform a relocation.
template<bool big_endian>
inline bool
Target_arm<big_endian>::Relocate::relocate(
const Relocate_info<32, big_endian>* /* relinfo */,
Target_arm* /* target */,
Output_section* /* output_section */,
size_t /* relnum */,
const elfcpp::Rel<32, big_endian>& /* rel */,
unsigned int r_type,
const Sized_symbol<32>* /* gsym */,
const Symbol_value<32>* /* psymval */,
unsigned char* /* view */,
elfcpp::Elf_types<32>::Elf_Addr /* address */,
section_size_type /* view_size */ )
{
switch (r_type)
{
case elfcpp::R_ARM_NONE:
break;
default:
gold_unreachable();
}
return true;
}
// Relocate section data.
template<bool big_endian>
void
Target_arm<big_endian>::relocate_section(
const Relocate_info<32, big_endian>* 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<32>::Elf_Addr address,
section_size_type view_size)
{
typedef typename Target_arm<big_endian>::Relocate Arm_relocate;
gold_assert(sh_type == elfcpp::SHT_REL);
gold::relocate_section<32, big_endian, Target_arm, elfcpp::SHT_REL,
Arm_relocate>(
relinfo,
this,
prelocs,
reloc_count,
output_section,
needs_special_offset_handling,
view,
address,
view_size);
}
// Return the size of a relocation while scanning during a relocatable
// link.
template<bool big_endian>
unsigned int
Target_arm<big_endian>::Relocatable_size_for_reloc::get_size_for_reloc(
unsigned int r_type,
Relobj* object)
{
r_type = get_real_reloc_type(r_type);
switch (r_type)
{
case elfcpp::R_ARM_NONE:
return 0;
case elfcpp::R_ARM_ABS32:
case elfcpp::R_ARM_REL32:
case elfcpp::R_ARM_THM_CALL:
case elfcpp::R_ARM_GOTOFF32:
case elfcpp::R_ARM_BASE_PREL:
case elfcpp::R_ARM_GOT_BREL:
case elfcpp::R_ARM_PLT32:
case elfcpp::R_ARM_CALL:
case elfcpp::R_ARM_JUMP24:
case elfcpp::R_ARM_PREL31:
return 4;
case elfcpp::R_ARM_TARGET1:
// This should have been mapped to another type already.
// Fall through.
case elfcpp::R_ARM_COPY:
case elfcpp::R_ARM_GLOB_DAT:
case elfcpp::R_ARM_JUMP_SLOT:
case elfcpp::R_ARM_RELATIVE:
// These are relocations which should only be seen by the
// dynamic linker, and should never be seen here.
gold_error(_("%s: unexpected reloc %u in object file"),
object->name().c_str(), r_type);
return 0;
default:
object->error(_("unsupported reloc %u in object file"), r_type);
return 0;
}
}
// Scan the relocs during a relocatable link.
template<bool big_endian>
void
Target_arm<big_endian>::scan_relocatable_relocs(
const General_options& options,
Symbol_table* symtab,
Layout* layout,
Sized_relobj<32, big_endian>* 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_REL);
typedef gold::Default_scan_relocatable_relocs<elfcpp::SHT_REL,
Relocatable_size_for_reloc> Scan_relocatable_relocs;
gold::scan_relocatable_relocs<32, big_endian, elfcpp::SHT_REL,
Scan_relocatable_relocs>(
options,
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.
template<bool big_endian>
void
Target_arm<big_endian>::relocate_for_relocatable(
const Relocate_info<32, big_endian>* 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<32>::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_REL);
gold::relocate_for_relocatable<32, big_endian, elfcpp::SHT_REL>(
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 symbol 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.
template<bool big_endian>
uint64_t
Target_arm<big_endian>::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();
}
// Map platform-specific relocs to real relocs
//
template<bool big_endian>
unsigned int
Target_arm<big_endian>::get_real_reloc_type (unsigned int r_type)
{
switch (r_type)
{
case elfcpp::R_ARM_TARGET1:
// This is either R_ARM_ABS32 or R_ARM_REL32;
return elfcpp::R_ARM_ABS32;
case elfcpp::R_ARM_TARGET2:
// This can be any reloc type but ususally is R_ARM_GOT_PREL
return elfcpp::R_ARM_GOT_PREL;
default:
return r_type;
}
}
// The selector for arm object files.
template<bool big_endian>
class Target_selector_arm : public Target_selector
{
public:
Target_selector_arm()
: Target_selector(elfcpp::EM_ARM, 32, big_endian,
(big_endian ? "elf32-bigarm" : "elf32-littlearm"))
{ }
Target*
do_instantiate_target()
{ return new Target_arm<big_endian>(); }
};
Target_selector_arm<false> target_selector_arm;
Target_selector_arm<true> target_selector_armbe;
} // End anonymous namespace.
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