292 lines
8.7 KiB
C++
292 lines
8.7 KiB
C++
// copy-relocs.cc -- handle COPY relocations for gold.
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// Copyright (C) 2006-2022 Free Software Foundation, Inc.
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// Written by Ian Lance Taylor <iant@google.com>.
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// This file is part of gold.
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3 of the License, or
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// (at your option) any later version.
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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// MA 02110-1301, USA.
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#include "gold.h"
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#include "symtab.h"
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#include "copy-relocs.h"
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namespace gold
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{
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// Copy_relocs methods.
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// Handle a relocation against a symbol which may force us to generate
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// a COPY reloc.
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template<int sh_type, int size, bool big_endian>
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void
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Copy_relocs<sh_type, size, big_endian>::copy_reloc(
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Symbol_table* symtab,
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Layout* layout,
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Sized_symbol<size>* sym,
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Sized_relobj_file<size, big_endian>* object,
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unsigned int shndx,
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Output_section* output_section,
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unsigned int r_type,
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typename elfcpp::Elf_types<size>::Elf_Addr r_offset,
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typename elfcpp::Elf_types<size>::Elf_Swxword r_addend,
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Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
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{
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if (this->need_copy_reloc(sym, object, shndx))
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this->make_copy_reloc(symtab, layout, sym, object, reloc_section);
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else
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{
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// We may not need a COPY relocation. Save this relocation to
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// possibly be emitted later.
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this->save(sym, object, shndx, output_section,
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r_type, r_offset, r_addend);
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}
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}
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// Return whether we need a COPY reloc for a relocation against SYM.
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// The relocation is begin applied to section SHNDX in OBJECT.
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template<int sh_type, int size, bool big_endian>
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bool
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Copy_relocs<sh_type, size, big_endian>::need_copy_reloc(
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Sized_symbol<size>* sym,
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Sized_relobj_file<size, big_endian>* object,
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unsigned int shndx) const
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{
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if (!parameters->options().copyreloc())
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return false;
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if (sym->symsize() == 0)
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return false;
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// If this is a readonly section, then we need a COPY reloc.
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// Otherwise we can use a dynamic reloc. Note that calling
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// section_flags here can be slow, as the information is not cached;
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// fortunately we shouldn't see too many potential COPY relocs.
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if ((object->section_flags(shndx) & elfcpp::SHF_WRITE) == 0)
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return true;
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return false;
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}
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// Emit a COPY relocation for SYM.
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template<int sh_type, int size, bool big_endian>
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void
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Copy_relocs<sh_type, size, big_endian>::emit_copy_reloc(
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Symbol_table* symtab,
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Sized_symbol<size>* sym,
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Output_data* posd,
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off_t offset,
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Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
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{
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// Define the symbol as being copied.
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symtab->define_with_copy_reloc(sym, posd, offset);
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// Add the COPY relocation to the dynamic reloc section.
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reloc_section->add_global_generic(sym, this->copy_reloc_type_, posd,
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offset, 0);
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}
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// Make a COPY relocation for SYM and emit it.
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template<int sh_type, int size, bool big_endian>
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void
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Copy_relocs<sh_type, size, big_endian>::make_copy_reloc(
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Symbol_table* symtab,
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Layout* layout,
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Sized_symbol<size>* sym,
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Sized_relobj_file<size, big_endian>* object,
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Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
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{
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// We should not be here if -z nocopyreloc is given.
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gold_assert(parameters->options().copyreloc());
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gold_assert(sym->is_from_dynobj());
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// The symbol must not have protected visibility.
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if (sym->is_protected())
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{
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gold_error(_("%s: cannot make copy relocation for "
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"protected symbol '%s', defined in %s"),
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object->name().c_str(),
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sym->name(),
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sym->object()->name().c_str());
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}
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typename elfcpp::Elf_types<size>::Elf_WXword symsize = sym->symsize();
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// There is no defined way to determine the required alignment of
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// the symbol. We know that the symbol is defined in a dynamic
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// object. We start with the alignment of the section in which it
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// is defined; presumably we do not require an alignment larger than
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// that. Then we reduce that alignment if the symbol is not aligned
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// within the section.
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bool is_ordinary;
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unsigned int shndx = sym->shndx(&is_ordinary);
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gold_assert(is_ordinary);
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typename elfcpp::Elf_types<size>::Elf_WXword addralign;
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bool is_readonly = false;
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{
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// Lock the object so we can read from it. This is only called
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// single-threaded from scan_relocs, so it is OK to lock.
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// Unfortunately we have no way to pass in a Task token.
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const Task* dummy_task = reinterpret_cast<const Task*>(-1);
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Object* obj = sym->object();
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Task_lock_obj<Object> tl(dummy_task, obj);
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addralign = obj->section_addralign(shndx);
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if (parameters->options().relro())
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{
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if ((obj->section_flags(shndx) & elfcpp::SHF_WRITE) == 0)
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is_readonly = true;
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else
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{
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// Symbols in .data.rel.ro should also be treated as read-only.
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if (obj->section_name(shndx) == ".data.rel.ro")
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is_readonly = true;
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}
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}
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}
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typename Sized_symbol<size>::Value_type value = sym->value();
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while ((value & (addralign - 1)) != 0)
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addralign >>= 1;
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// Mark the dynamic object as needed for the --as-needed option.
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sym->object()->set_is_needed();
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Output_data_space* dynbss;
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if (is_readonly)
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{
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if (this->dynrelro_ == NULL)
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{
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this->dynrelro_ = new Output_data_space(addralign, "** dynrelro");
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layout->add_output_section_data(".data.rel.ro",
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elfcpp::SHT_PROGBITS,
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elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,
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this->dynrelro_, ORDER_RELRO, false);
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}
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dynbss = this->dynrelro_;
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}
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else
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{
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if (this->dynbss_ == NULL)
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{
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this->dynbss_ = new Output_data_space(addralign, "** dynbss");
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layout->add_output_section_data(".bss",
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elfcpp::SHT_NOBITS,
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elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,
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this->dynbss_, ORDER_BSS, false);
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}
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dynbss = this->dynbss_;
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}
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if (addralign > dynbss->addralign())
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dynbss->set_space_alignment(addralign);
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section_size_type dynbss_size =
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convert_to_section_size_type(dynbss->current_data_size());
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dynbss_size = align_address(dynbss_size, addralign);
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section_size_type offset = dynbss_size;
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dynbss->set_current_data_size(dynbss_size + symsize);
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this->emit_copy_reloc(symtab, sym, dynbss, offset, reloc_section);
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}
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// Save a relocation to possibly be emitted later.
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template<int sh_type, int size, bool big_endian>
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void
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Copy_relocs<sh_type, size, big_endian>::save(
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Symbol* sym,
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Sized_relobj_file<size, big_endian>* object,
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unsigned int shndx,
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Output_section* output_section,
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unsigned int r_type,
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typename elfcpp::Elf_types<size>::Elf_Addr r_offset,
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typename elfcpp::Elf_types<size>::Elf_Swxword r_addend)
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{
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this->entries_.push_back(Copy_reloc_entry(sym, r_type, object, shndx,
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output_section, r_offset,
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r_addend));
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}
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// Emit any saved relocs.
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template<int sh_type, int size, bool big_endian>
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void
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Copy_relocs<sh_type, size, big_endian>::emit(
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Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
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{
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for (typename Copy_reloc_entries::iterator p = this->entries_.begin();
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p != this->entries_.end();
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++p)
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{
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Copy_reloc_entry& entry = *p;
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// If the symbol is no longer defined in a dynamic object, then we
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// emitted a COPY relocation, and we do not want to emit this
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// dynamic relocation.
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if (entry.sym_->is_from_dynobj())
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reloc_section->add_global_generic(entry.sym_, entry.reloc_type_,
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entry.output_section_, entry.relobj_,
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entry.shndx_, entry.address_,
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entry.addend_);
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}
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// We no longer need the saved information.
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this->entries_.clear();
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}
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// Instantiate the templates we need.
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#ifdef HAVE_TARGET_32_LITTLE
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template
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class Copy_relocs<elfcpp::SHT_REL, 32, false>;
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template
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class Copy_relocs<elfcpp::SHT_RELA, 32, false>;
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#endif
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#ifdef HAVE_TARGET_32_BIG
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template
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class Copy_relocs<elfcpp::SHT_REL, 32, true>;
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template
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class Copy_relocs<elfcpp::SHT_RELA, 32, true>;
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#endif
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#ifdef HAVE_TARGET_64_LITTLE
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template
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class Copy_relocs<elfcpp::SHT_REL, 64, false>;
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template
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class Copy_relocs<elfcpp::SHT_RELA, 64, false>;
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#endif
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#ifdef HAVE_TARGET_64_BIG
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template
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class Copy_relocs<elfcpp::SHT_REL, 64, true>;
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template
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class Copy_relocs<elfcpp::SHT_RELA, 64, true>;
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#endif
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} // End namespace gold.
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