2009-05-29 Doug Kwan <dougkwan@google.com>

* gold/arm.cc (Output_data_plt_arm): Forward declaration for new
	template class.
	(class Target_arm): Update comment.
	(Target_arm::Target_arm): Initialize new data members GOT_,
	PLT_, GOT_PLT_, REL_DYN_, COPY_RELOCS_ and DYNBSS_.
	Declare new methods Target_arm::got_section, Target_arm::make_plt_entry
	and Target_arm::rel_dyn_section.
	Declare new_enum Target_arm::Got_type.
	Declare new data members GOT_, PLT_, GOT_PLT_, REL_DYN_, COPY_RELOCS_
	and DYNBSS_.
	Update commments for member do_dynsym_value.
	(Target_arm::got_size, Target_arm::plt_section,
	Target_arm::may_need_copy_reloc and Target_arm::copy_reloc): Define
	new methods inside class defintion.
	(Target_arm::got_section): Define new method.
	(Target_arm::rel_dyn_section): Same.
	(Output_data_plt_arm): New template class.
	(Output_data_plt_arm::Output_data_plt_arm): Define constructor.
	(Output_data_plt_arm:do_adjust_output_section): Define new method.
	(Output_data_plt_arm::add_entry): Same.
	(Output_data_plt_arm::first_plt_entry): Define new
	static data member for PLT instruction template.
	(Output_data_plt_arm::plt_entry): Same.
	(Output_data_plt_arm::do_write): Define new method.
	(Target_arm::make_plt_entry): Same.
	(Target_arm::do_finalize_sections): Same.
	(Target_arm::do_dynsym_value): Same.
This commit is contained in:
Doug Kwan 2009-05-30 00:55:42 +00:00
parent 5a43797524
commit 94cdfcffc3
2 changed files with 457 additions and 8 deletions

View File

@ -1,3 +1,33 @@
2009-05-29 Doug Kwan <dougkwan@google.com>
* gold/arm.cc (Output_data_plt_arm): Forward declaration for new
template class.
(class Target_arm): Update comment.
(Target_arm::Target_arm): Initialize new data members GOT_,
PLT_, GOT_PLT_, REL_DYN_, COPY_RELOCS_ and DYNBSS_.
Declare new methods Target_arm::got_section, Target_arm::make_plt_entry
and Target_arm::rel_dyn_section.
Declare new_enum Target_arm::Got_type.
Declare new data members GOT_, PLT_, GOT_PLT_, REL_DYN_, COPY_RELOCS_
and DYNBSS_.
Update commments for member do_dynsym_value.
(Target_arm::got_size, Target_arm::plt_section,
Target_arm::may_need_copy_reloc and Target_arm::copy_reloc): Define
new methods inside class defintion.
(Target_arm::got_section): Define new method.
(Target_arm::rel_dyn_section): Same.
(Output_data_plt_arm): New template class.
(Output_data_plt_arm::Output_data_plt_arm): Define constructor.
(Output_data_plt_arm:do_adjust_output_section): Define new method.
(Output_data_plt_arm::add_entry): Same.
(Output_data_plt_arm::first_plt_entry): Define new
static data member for PLT instruction template.
(Output_data_plt_arm::plt_entry): Same.
(Output_data_plt_arm::do_write): Define new method.
(Target_arm::make_plt_entry): Same.
(Target_arm::do_finalize_sections): Same.
(Target_arm::do_dynsym_value): Same.
2009-05-28 Doug Kwan <dougkwan@google.com>
* Makefile.am (TARGETSOURCES): Add arm.cc.

View File

@ -48,6 +48,9 @@ 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
@ -72,7 +75,6 @@ using namespace gold;
// R_ARM_PREL31
//
// Coming soon (pending patches):
// - Support for dynamic symbols (GOT, PLT and etc).
// - Local scanner
// - Global scanner
// - Relocation
@ -85,6 +87,8 @@ using namespace gold;
// - 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>
@ -94,7 +98,9 @@ class Target_arm : public Sized_target<32, big_endian>
Reloc_section;
Target_arm()
: Sized_target<32, big_endian>(&arm_info)
: 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
@ -132,7 +138,7 @@ class Target_arm : public Sized_target<32, big_endian>
void
do_finalize_sections(Layout*);
// Return the value to use for a dynamic which requires special
// Return the value to use for a dynamic symbol which requires special
// treatment.
uint64_t
do_dynsym_value(const Symbol*) const;
@ -185,6 +191,14 @@ class Target_arm : public Sized_target<32, big_endian>
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);
@ -256,9 +270,80 @@ class Target_arm : public Sized_target<32, big_endian>
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);
}
// 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>
@ -278,6 +363,300 @@ const Target::Target_info Target_arm<big_endian>::arm_info =
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>
@ -436,9 +815,44 @@ Target_arm<big_endian>::scan_relocs(const General_options& options,
template<bool big_endian>
void
Target_arm<big_endian>::do_finalize_sections(Layout* /* layout */)
Target_arm<big_endian>::do_finalize_sections(Layout* layout)
{
gold_unreachable ();
// 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));
}
// Perform a relocation.
@ -621,12 +1035,17 @@ Target_arm<big_endian>::relocate_for_relocatable(
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
Target_arm<big_endian>::do_dynsym_value(const Symbol* gsym) const
{
gold_unreachable ();
return 0;
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