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
// R_ARM_PREL31
//
// Coming soon (pending patches):
-// - Support for dynamic symbols (GOT, PLT and etc).
// - Local scanner
// - Global scanner
// - Relocation
// - 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>
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
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;
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);
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>
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>
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.
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
projects / deliverable / binutils-gdb.git / commitdiff
