[PATCH 3/5] Add support for LZO-compressed kernels

Albin Tonnerre
2009-07-22T14:01:40Z

This is the first part of the lzo patch
The lzo compressor is worse than gzip at compression, but faster at
extraction. Here are some figures for an ARM board I'm working on:

Uncompressed size: 3.24Mo
gzip 1.61Mo 0.72s
lzo 1.75Mo 0.48s

So for a compression ratio that is still relatively close to gzip, it's
much faster to extract, at least in that case.

This version applies to kernel 2.6.31-rc3

This part contains:
- Makefile routine to support lzo compression
- Fixes to the existing lzo compressor so that it can be used in
compressed kernels
- wrapper around the existing lzo1x_decompress, as it only extracts one
block at a time, while we need to extract a whole file here
- config dialog for kernel compression

Signed-off-by: Albin Tonnerre <albin.tonnerre@free-electrons.com>
---
include/linux/decompress/unlzo.h | 10 +++
init/Kconfig | 18 ++++-
lib/decompress_unlzo.c | 138 ++++++++++++++++++++++++++++++++++++++
lib/lzo/lzo1x_decompress.c | 9 ++-
scripts/Makefile.lib | 5 ++
5 files changed, 173 insertions(+), 7 deletions(-)
create mode 100644 include/linux/decompress/unlzo.h
create mode 100644 lib/decompress_unlzo.c

diff --git a/include/linux/decompress/unlzo.h b/include/linux/decompress/unlzo.h
new file mode 100644
index 0000000..d1925ea
--- /dev/null
+++ b/include/linux/decompress/unlzo.h
@@ -0,0 +1,10 @@
+#ifndef DECOMPRESS_UNLZO_H
+#define DECOMPRESS_UNLZO_H
+
+int unlzo(unsigned char *inbuf, int len,
+ int(*fill)(void*, unsigned int),
+ int(*flush)(void*, unsigned int),
+ unsigned char *output,
+ int *pos,
+ void(*error)(char *x));
+#endif
diff --git a/init/Kconfig b/init/Kconfig
index 1ce05a4..66281fb 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -115,10 +115,13 @@ config HAVE_KERNEL_BZIP2
config HAVE_KERNEL_LZMA
bool

+config HAVE_KERNEL_LZO
+ bool
+
choice
prompt "Kernel compression mode"
default KERNEL_GZIP
- depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
+ depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
help
The linux kernel is a kind of self-extracting executable.
Several compression algorithms are available, which differ
@@ -141,9 +144,8 @@ config KERNEL_GZIP
bool "Gzip"
depends on HAVE_KERNEL_GZIP
help
- The old and tried gzip compression. Its compression ratio is
- the poorest among the 3 choices; however its speed (both
- compression and decompression) is the fastest.
+ The old and tried gzip compression. It provides a good balance
+ between compression ration and decompression speed.

config KERNEL_BZIP2
bool "Bzip2"
@@ -164,6 +166,14 @@ config KERNEL_LZMA
two. Compression is slowest. The kernel size is about 33%
smaller with LZMA in comparison to gzip.

+config KERNEL_LZO
+ bool "LZO"
+ depends on HAVE_KERNEL_LZO
+ help
+ Its compression ratio is the poorest among the 4. The kernel
+ size is about about 10% bigger than gzip; however its speed
+ (both compression and decompression) is the fastest.
+
endchoice

config SWAP
diff --git a/lib/decompress_unlzo.c b/lib/decompress_unlzo.c
new file mode 100644
index 0000000..d908b35
--- /dev/null
+++ b/lib/decompress_unlzo.c
@@ -0,0 +1,138 @@
+/*
+ * LZO decompressor for the Linux kernel. Code borrowed from the lzo
+ * implementation by Markus Franz Xaver Johannes Oberhumer.
+ *
+ * Linux kernel adaptation:
+ * Copyright (C) 2009
+ * Albin Tonnerre, Free Electrons <albin.tonnerre@free-electrons.com>
+ *
+ * Original code:
+ * Copyright (C) 1996-2005 Markus Franz Xaver Johannes Oberhumer
+ * All Rights Reserved.
+ *
+ * lzop and the LZO library are free software; you can redistribute them
+ * and/or modify them under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 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; see the file COPYING.
+ * If not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Markus F.X.J. Oberhumer
+ * <markus@oberhumer.com>
+ * http://www.oberhumer.com/opensource/lzop/
+ */
+
+#ifdef STATIC
+#include "lzo/lzo1x_decompress.c"
+#endif
+
+#include <linux/lzo.h>
+#include <linux/decompress/mm.h>
+#include <linux/decompress/unlzo.h>
+
+#include <linux/compiler.h>
+#include <linux/types.h>
+#include <asm/unaligned.h>
+
+static const unsigned char lzop_magic[] =
+ { 0x89, 0x4c, 0x5a, 0x4f, 0x00, 0x0d, 0x0a, 0x1a, 0x0a };
+
+#define BLOCK_SIZE (256*1024l)
+#define HEADER_HAS_FILTER 0x00000800L
+
+STATIC inline int INIT parse_header(u8 *input, u8 *skip)
+{
+ int l;
+ u8 *parse = input;
+ u8 level = 0;
+ u16 version;
+
+ /* read magic: 9 first bits */
+ for (l = 0; l < 9; l++) {
+ if (*parse++ != lzop_magic[l])
+ return 0;
+ }
+ /* get version (2bytes), skip library version (2),
+ * 'need to be extracted' version (2) and
+ * method (1) */
+ version = get_unaligned_be16(parse);
+ parse += 7;
+ if (version >= 0x0940)
+ level = *parse++;
+ if (get_unaligned_be32(parse) & HEADER_HAS_FILTER)
+ parse += 8; /* flags + filter info */
+ else
+ parse += 4; /* flags */
+
+ /* skip mode and mtime_low */
+ parse += 8;
+ if (version >= 0x0940)
+ parse += 4; /* skip mtime_high */
+
+ l = *parse++;
+ /* don't care about the file name, and skip checksum */
+ parse += l + 4;
+
+ *skip = parse - input;
+ return 1;
+}
+
+STATIC inline int INIT lzo_decompress(u8 *input, int in_len,
+ int (*fill) (void *, unsigned int),
+ int (*flush) (void *, unsigned int),
+ u8 *output, int *posp,
+ void (*error_fn) (char *x))
+{
+ u8 skip = 0, r = 0;
+ u32 src_len, dst_len;
+ size_t tmp;
+ u8 *in_buf = input;
+ u8 *out_buf = output;
+ int obytes_processed = 0;
+
+ if (!parse_header(input, &skip))
+ error("invalid header");
+
+ in_buf += skip;
+ for (;;) {
+ /* read uncompressed block size */
+ dst_len = get_unaligned_be32(in_buf);
+ in_buf += 4;
+
+ /* exit if last block */
+ if (dst_len == 0)
+ break;
+
+ if (dst_len > BLOCK_SIZE)
+ error("dest len longer than block size");
+
+ /* read compressed block size, and skip block checksum info */
+ src_len = get_unaligned_be32(in_buf);
+ in_buf += 8;
+
+ if (src_len <= 0 || src_len > dst_len)
+ error("file corrupted");
+
+ /* decompress */
+ tmp = dst_len;
+ r = lzo1x_decompress_safe((u8 *) in_buf, src_len, out_buf, &tmp);
+
+ if (r != LZO_E_OK || dst_len != tmp)
+ error("Compressed data violation");
+
+ obytes_processed += dst_len;
+ in_buf += src_len;
+ out_buf += dst_len;
+ }
+ return obytes_processed;
+}
+
+#define decompress lzo_decompress
diff --git a/lib/lzo/lzo1x_decompress.c b/lib/lzo/lzo1x_decompress.c
index 5dc6b29..f2fd098 100644
--- a/lib/lzo/lzo1x_decompress.c
+++ b/lib/lzo/lzo1x_decompress.c
@@ -11,11 +11,13 @@
* Richard Purdie <rpurdie@openedhand.com>
*/

+#ifndef STATIC
#include <linux/module.h>
#include <linux/kernel.h>
-#include <linux/lzo.h>
-#include <asm/byteorder.h>
+#endif
+
#include <asm/unaligned.h>
+#include <linux/lzo.h>
#include "lzodefs.h"

#define HAVE_IP(x, ip_end, ip) ((size_t)(ip_end - ip) < (x))
@@ -244,9 +246,10 @@ lookbehind_overrun:
*out_len = op - out;
return LZO_E_LOOKBEHIND_OVERRUN;
}
-
+#ifndef STATIC
EXPORT_SYMBOL_GPL(lzo1x_decompress_safe);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("LZO1X Decompressor");

+#endif
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 7a77787..7b721d1 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -230,3 +230,8 @@ quiet_cmd_lzma = LZMA $@
cmd_lzma = (cat $(filter-out FORCE,$^) | \
lzma -9 && $(call size_append, $(filter-out FORCE,$^))) > $@ || \
(rm -f $@ ; false)
+
+quiet_cmd_lzo = LZO $@
+cmd_lzo = (cat $(filter-out FORCE,$^) | \
+ lzop -9 && $(call size_append, $(filter-out FORCE,$^))) > $@ || \
+ (rm -f $@ ; false)
--
1.6.0.4