377 lines
14 KiB
C++
377 lines
14 KiB
C++
// reduced_debug_output.cc -- output reduced debugging information to save space
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// Copyright (C) 2008-2016 Free Software Foundation, Inc.
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// Written by Caleb Howe <cshowe@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 "parameters.h"
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#include "options.h"
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#include "dwarf.h"
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#include "dwarf_reader.h"
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#include "reduced_debug_output.h"
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#include "int_encoding.h"
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#include <vector>
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namespace gold
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{
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// Given a pointer to the beginning of a die and the beginning of the associated
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// abbreviation fills in die_end with the end of the information entry. If
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// successful returns true. Get_die_end also takes a pointer to the end of the
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// buffer containing the die. If die_end would be beyond the end of the
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// buffer, or if an unsupported dwarf form is encountered returns false.
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bool
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Output_reduced_debug_info_section::get_die_end(
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unsigned char* die, unsigned char* abbrev, unsigned char** die_end,
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unsigned char* buffer_end, int address_size, bool is64)
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{
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size_t LEB_size;
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uint64_t LEB_decoded;
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for(;;)
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{
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uint64_t attribute = read_unsigned_LEB_128(abbrev, &LEB_size);
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abbrev += LEB_size;
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elfcpp::DW_FORM form =
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static_cast<elfcpp::DW_FORM>(read_unsigned_LEB_128(abbrev,
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&LEB_size));
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abbrev += LEB_size;
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if (!(attribute || form))
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break;
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if (die >= buffer_end)
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return false;
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switch(form)
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{
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case elfcpp::DW_FORM_flag_present:
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break;
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case elfcpp::DW_FORM_strp:
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case elfcpp::DW_FORM_sec_offset:
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die += is64 ? 8 : 4;
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break;
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case elfcpp::DW_FORM_addr:
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case elfcpp::DW_FORM_ref_addr:
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die += address_size;
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break;
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case elfcpp::DW_FORM_block1:
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die += *die;
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die += 1;
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break;
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case elfcpp::DW_FORM_block2:
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{
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uint16_t block_size;
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block_size = read_from_pointer<16>(&die);
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die += block_size;
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break;
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}
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case elfcpp::DW_FORM_block4:
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{
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uint32_t block_size;
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block_size = read_from_pointer<32>(&die);
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die += block_size;
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break;
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}
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case elfcpp::DW_FORM_block:
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case elfcpp::DW_FORM_exprloc:
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LEB_decoded = read_unsigned_LEB_128(die, &LEB_size);
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die += (LEB_decoded + LEB_size);
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break;
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case elfcpp::DW_FORM_data1:
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case elfcpp::DW_FORM_ref1:
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case elfcpp::DW_FORM_flag:
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die += 1;
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break;
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case elfcpp::DW_FORM_data2:
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case elfcpp::DW_FORM_ref2:
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die += 2;
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break;
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case elfcpp::DW_FORM_data4:
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case elfcpp::DW_FORM_ref4:
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die += 4;
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break;
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case elfcpp::DW_FORM_data8:
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case elfcpp::DW_FORM_ref8:
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case elfcpp::DW_FORM_ref_sig8:
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die += 8;
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break;
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case elfcpp::DW_FORM_ref_udata:
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case elfcpp::DW_FORM_udata:
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read_unsigned_LEB_128(die, &LEB_size);
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die += LEB_size;
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break;
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case elfcpp::DW_FORM_sdata:
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read_signed_LEB_128(die, &LEB_size);
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die += LEB_size;
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break;
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case elfcpp::DW_FORM_string:
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{
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size_t length = strlen(reinterpret_cast<char*>(die));
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die += length + 1;
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break;
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}
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case elfcpp::DW_FORM_indirect:
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case elfcpp::DW_FORM_GNU_addr_index:
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case elfcpp::DW_FORM_GNU_str_index:
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default:
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return false;
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}
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}
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*die_end = die;
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return true;
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}
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void
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Output_reduced_debug_abbrev_section::set_final_data_size()
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{
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if (this->sized_ || this->failed_)
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return;
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uint64_t abbrev_number;
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size_t LEB_size;
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unsigned char* abbrev_data = this->postprocessing_buffer();
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unsigned char* abbrev_end = this->postprocessing_buffer() +
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this->postprocessing_buffer_size();
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this->write_to_postprocessing_buffer();
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while(abbrev_data < abbrev_end)
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{
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uint64_t abbrev_offset = abbrev_data - this->postprocessing_buffer();
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while((abbrev_number = read_unsigned_LEB_128(abbrev_data, &LEB_size)))
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{
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if (abbrev_data >= abbrev_end)
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{
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failed("Debug abbreviations extend beyond .debug_abbrev "
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"section; failed to reduce debug abbreviations");
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return;
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}
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abbrev_data += LEB_size;
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// Together with the abbreviation number these fields make up
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// the header for each abbreviation.
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uint64_t abbrev_type = read_unsigned_LEB_128(abbrev_data, &LEB_size);
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abbrev_data += LEB_size;
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// This would ordinarily be the has_children field of the
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// abbreviation. But it's going to be false after reducing the
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// information, so there's no point in storing it.
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abbrev_data++;
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// Read to the end of the current abbreviation.
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// This is indicated by two zero unsigned LEBs in a row. We don't
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// need to parse the data yet, so we just scan through the data
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// looking for two consecutive 0 bytes indicating the end of the
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// abbreviation.
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unsigned char* current_abbrev;
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for (current_abbrev = abbrev_data;
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current_abbrev[0] || current_abbrev[1];
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current_abbrev++)
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{
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if (current_abbrev >= abbrev_end)
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{
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this->failed(_("Debug abbreviations extend beyond "
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".debug_abbrev section; failed to reduce "
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"debug abbreviations"));
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return;
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}
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}
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// Account for the two nulls and advance to the start of the
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// next abbreviation.
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current_abbrev += 2;
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// We're eliminating every entry except for compile units, so we
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// only need to store abbreviations that describe them
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if (abbrev_type == elfcpp::DW_TAG_compile_unit)
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{
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write_unsigned_LEB_128(&this->data_, ++this->abbrev_count_);
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write_unsigned_LEB_128(&this->data_, abbrev_type);
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// has_children is false for all entries
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this->data_.push_back(0);
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this->abbrev_mapping_[std::make_pair(abbrev_offset,
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abbrev_number)] =
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std::make_pair(abbrev_count_, this->data_.size());
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this->data_.insert(this->data_.end(), abbrev_data,
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current_abbrev);
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}
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abbrev_data = current_abbrev;
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}
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gold_assert(LEB_size == 1);
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abbrev_data += LEB_size;
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}
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// Null terminate the list of abbreviations
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this->data_.push_back(0);
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this->set_data_size(data_.size());
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this->sized_ = true;
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}
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void
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Output_reduced_debug_abbrev_section::do_write(Output_file* of)
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{
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off_t offset = this->offset();
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off_t data_size = this->data_size();
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unsigned char* view = of->get_output_view(offset, data_size);
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if (this->failed_)
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memcpy(view, this->postprocessing_buffer(),
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this->postprocessing_buffer_size());
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else
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memcpy(view, &this->data_.front(), data_size);
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of->write_output_view(offset, data_size, view);
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}
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// Locates the abbreviation with abbreviation_number abbrev_number in the
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// abbreviation table at offset abbrev_offset. abbrev_number is updated with
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// its new abbreviation number and a pointer to the beginning of the
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// abbreviation is returned.
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unsigned char*
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Output_reduced_debug_abbrev_section::get_new_abbrev(
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uint64_t* abbrev_number, uint64_t abbrev_offset)
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{
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set_final_data_size();
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std::pair<uint64_t, uint64_t> abbrev_info =
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this->abbrev_mapping_[std::make_pair(abbrev_offset, *abbrev_number)];
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*abbrev_number = abbrev_info.first;
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return &this->data_[abbrev_info.second];
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}
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void Output_reduced_debug_info_section::set_final_data_size()
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{
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if (this->failed_)
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return;
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unsigned char* debug_info = this->postprocessing_buffer();
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unsigned char* debug_info_end = (this->postprocessing_buffer()
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+ this->postprocessing_buffer_size());
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unsigned char* next_compile_unit;
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this->write_to_postprocessing_buffer();
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while (debug_info < debug_info_end)
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{
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uint32_t compile_unit_start = read_from_pointer<32>(&debug_info);
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// The first 4 bytes of each compile unit determine whether or
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// not we're using dwarf32 or dwarf64. This is not necessarily
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// related to whether the binary is 32 or 64 bits.
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if (compile_unit_start == 0xFFFFFFFF)
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{
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// Technically the size can be up to 96 bits. Rather than handle
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// 96/128 bit integers we just truncate the size at 64 bits.
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if (0 != read_from_pointer<32>(&debug_info))
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{
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this->failed(_("Extremely large compile unit in debug info; "
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"failed to reduce debug info"));
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return;
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}
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const int dwarf64_header_size = sizeof(uint64_t) + sizeof(uint16_t) +
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sizeof(uint64_t) + sizeof(uint8_t);
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if (debug_info + dwarf64_header_size >= debug_info_end)
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{
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this->failed(_("Debug info extends beyond .debug_info section;"
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"failed to reduce debug info"));
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return;
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}
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uint64_t compile_unit_size = read_from_pointer<64>(&debug_info);
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next_compile_unit = debug_info + compile_unit_size;
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uint16_t version = read_from_pointer<16>(&debug_info);
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uint64_t abbrev_offset = read_from_pointer<64>(&debug_info);
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uint8_t address_size = read_from_pointer<8>(&debug_info);
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size_t LEB_size;
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uint64_t abbreviation_number = read_unsigned_LEB_128(debug_info,
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&LEB_size);
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debug_info += LEB_size;
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unsigned char* die_abbrev = this->associated_abbrev_->get_new_abbrev(
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&abbreviation_number, abbrev_offset);
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unsigned char* die_end;
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if (!this->get_die_end(debug_info, die_abbrev, &die_end,
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debug_info_end, address_size, true))
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{
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this->failed(_("Invalid DIE in debug info; "
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"failed to reduce debug info"));
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return;
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}
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insert_into_vector<32>(&this->data_, 0xFFFFFFFF);
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insert_into_vector<32>(&this->data_, 0);
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insert_into_vector<64>(
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&this->data_,
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(11 + get_length_as_unsigned_LEB_128(abbreviation_number)
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+ die_end - debug_info));
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insert_into_vector<16>(&this->data_, version);
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insert_into_vector<64>(&this->data_, 0);
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insert_into_vector<8>(&this->data_, address_size);
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write_unsigned_LEB_128(&this->data_, abbreviation_number);
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this->data_.insert(this->data_.end(), debug_info, die_end);
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}
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else
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{
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const int dwarf32_header_size =
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sizeof(uint16_t) + sizeof(uint32_t) + sizeof(uint8_t);
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if (debug_info + dwarf32_header_size >= debug_info_end)
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{
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this->failed(_("Debug info extends beyond .debug_info section; "
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"failed to reduce debug info"));
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return;
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}
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uint32_t compile_unit_size = compile_unit_start;
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next_compile_unit = debug_info + compile_unit_size;
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uint16_t version = read_from_pointer<16>(&debug_info);
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uint32_t abbrev_offset = read_from_pointer<32>(&debug_info);
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uint8_t address_size = read_from_pointer<8>(&debug_info);
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size_t LEB_size;
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uint64_t abbreviation_number = read_unsigned_LEB_128(debug_info,
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&LEB_size);
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debug_info += LEB_size;
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unsigned char* die_abbrev = this->associated_abbrev_->get_new_abbrev(
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&abbreviation_number, abbrev_offset);
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unsigned char* die_end;
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if (!this->get_die_end(debug_info, die_abbrev, &die_end,
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debug_info_end, address_size, false))
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{
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this->failed(_("Invalid DIE in debug info; "
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"failed to reduce debug info"));
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return;
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}
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insert_into_vector<32>(
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&this->data_,
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(7 + get_length_as_unsigned_LEB_128(abbreviation_number)
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+ die_end - debug_info));
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insert_into_vector<16>(&this->data_, version);
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insert_into_vector<32>(&this->data_, 0);
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insert_into_vector<8>(&this->data_, address_size);
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write_unsigned_LEB_128(&this->data_, abbreviation_number);
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this->data_.insert(this->data_.end(), debug_info, die_end);
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}
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debug_info = next_compile_unit;
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}
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this->set_data_size(data_.size());
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}
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void Output_reduced_debug_info_section::do_write(Output_file* of)
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{
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off_t offset = this->offset();
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off_t data_size = this->data_size();
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unsigned char* view = of->get_output_view(offset, data_size);
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if (this->failed_)
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memcpy(view, this->postprocessing_buffer(),
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this->postprocessing_buffer_size());
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else
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memcpy(view, &this->data_.front(), data_size);
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of->write_output_view(offset, data_size, view);
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}
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} // End namespace gold.
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