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// compressed_output.cc -- manage compressed debug sections for gold
// Copyright (C) 2007-2015 Free Software Foundation, Inc.
// Written 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 <zlib.h>
#include "parameters.h"
#include "options.h"
#include "compressed_output.h"
namespace gold
{
// Compress UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE. Returns true
// if it successfully compressed, false if it failed for any reason
// (including not having zlib support in the library). If it returns
// true, it allocates memory for the compressed data using new, and
// sets *COMPRESSED_DATA and *COMPRESSED_SIZE to appropriate values.
// It also writes a header before COMPRESSED_DATA: 4 bytes saying
// "ZLIB", and 8 bytes indicating the uncompressed size, in big-endian
// order.
static bool
zlib_compress(const unsigned char* uncompressed_data,
unsigned long uncompressed_size,
unsigned char** compressed_data,
unsigned long* compressed_size)
{
const int header_size = 12;
*compressed_size = uncompressed_size + uncompressed_size / 1000 + 128;
*compressed_data = new unsigned char[*compressed_size + header_size];
int compress_level;
if (parameters->options().optimize() >= 1)
compress_level = 9;
else
compress_level = 1;
int rc = compress2(reinterpret_cast<Bytef*>(*compressed_data) + header_size,
compressed_size,
reinterpret_cast<const Bytef*>(uncompressed_data),
uncompressed_size,
compress_level);
if (rc == Z_OK)
{
memcpy(*compressed_data, "ZLIB", 4);
elfcpp::Swap_unaligned<64, true>::writeval(*compressed_data + 4,
uncompressed_size);
*compressed_size += header_size;
return true;
}
else
{
delete[] *compressed_data;
*compressed_data = NULL;
return false;
}
}
// Decompress COMPRESSED_DATA of size COMPRESSED_SIZE, into a buffer
// UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE. Returns TRUE if it
// decompressed successfully, false if it failed. The buffer, of
// appropriate size, is provided by the caller, and is typically part
// of the memory-mapped output file.
static bool
zlib_decompress(const unsigned char* compressed_data,
unsigned long compressed_size,
unsigned char* uncompressed_data,
unsigned long uncompressed_size)
{
z_stream strm;
int rc;
/* It is possible the section consists of several compressed
buffers concatenated together, so we uncompress in a loop. */
strm.zalloc = NULL;
strm.zfree = NULL;
strm.opaque = NULL;
strm.avail_in = compressed_size;
strm.next_in = const_cast<Bytef*>(compressed_data);
strm.avail_out = uncompressed_size;
rc = inflateInit(&strm);
while (strm.avail_in > 0)
{
if (rc != Z_OK)
return false;
strm.next_out = ((Bytef*) uncompressed_data
+ (uncompressed_size - strm.avail_out));
rc = inflate(&strm, Z_FINISH);
if (rc != Z_STREAM_END)
return false;
rc = inflateReset(&strm);
}
rc = inflateEnd(&strm);
if (rc != Z_OK || strm.avail_out != 0)
return false;
return true;
}
// Read the compression header of a compressed debug section and return
// the uncompressed size.
uint64_t
get_uncompressed_size(const unsigned char* compressed_data,
section_size_type compressed_size)
{
const unsigned int zlib_header_size = 12;
/* Verify the compression header. Currently, we support only zlib
compression, so it should be "ZLIB" followed by the uncompressed
section size, 8 bytes in big-endian order. */
if (compressed_size >= zlib_header_size
&& strncmp(reinterpret_cast<const char*>(compressed_data),
"ZLIB", 4) == 0)
return elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);
return -1ULL;
}
// Decompress a compressed debug section directly into the output file.
bool
decompress_input_section(const unsigned char* compressed_data,
unsigned long compressed_size,
unsigned char* uncompressed_data,
unsigned long uncompressed_size)
{
const unsigned int zlib_header_size = 12;
/* Verify the compression header. Currently, we support only zlib
compression, so it should be "ZLIB" followed by the uncompressed
section size, 8 bytes in big-endian order. */
if (compressed_size >= zlib_header_size
&& strncmp(reinterpret_cast<const char*>(compressed_data),
"ZLIB", 4) == 0)
{
unsigned long uncompressed_size_check =
elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);
gold_assert(uncompressed_size_check == uncompressed_size);
return zlib_decompress(compressed_data + zlib_header_size,
compressed_size - zlib_header_size,
uncompressed_data,
uncompressed_size);
}
return false;
}
// Class Output_compressed_section.
// Set the final data size of a compressed section. This is where
// we actually compress the section data.
void
Output_compressed_section::set_final_data_size()
{
off_t uncompressed_size = this->postprocessing_buffer_size();
// (Try to) compress the data.
unsigned long compressed_size;
unsigned char* uncompressed_data = this->postprocessing_buffer();
// At this point the contents of all regular input sections will
// have been copied into the postprocessing buffer, and relocations
// will have been applied. Now we need to copy in the contents of
// anything other than a regular input section.
this->write_to_postprocessing_buffer();
bool success = false;
if (strcmp(this->options_->compress_debug_sections(), "zlib") == 0)
success = zlib_compress(uncompressed_data, uncompressed_size,
&this->data_, &compressed_size);
if (success)
{
// This converts .debug_foo to .zdebug_foo
this->new_section_name_ = std::string(".z") + (this->name() + 1);
this->set_name(this->new_section_name_.c_str());
this->set_data_size(compressed_size);
}
else
{
gold_warning(_("not compressing section data: zlib error"));
gold_assert(this->data_ == NULL);
this->set_data_size(uncompressed_size);
}
}
// Write out a compressed section. If we couldn't compress, we just
// write it out as normal, uncompressed data.
void
Output_compressed_section::do_write(Output_file* of)
{
off_t offset = this->offset();
off_t data_size = this->data_size();
unsigned char* view = of->get_output_view(offset, data_size);
if (this->data_ == NULL)
memcpy(view, this->postprocessing_buffer(), data_size);
else
memcpy(view, this->data_, data_size);
of->write_output_view(offset, data_size, view);
}
} // End namespace gold.
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