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2022-04-08lz4: fix LZ4_decompress_safe_partial read out of boundGuo Xuenan1-2/+6
When partialDecoding, it is EOF if we've either filled the output buffer or can't proceed with reading an offset for following match. In some extreme corner cases when compressed data is suitably corrupted, UAF will occur. As reported by KASAN [1], LZ4_decompress_safe_partial may lead to read out of bound problem during decoding. lz4 upstream has fixed it [2] and this issue has been disscussed here [3] before. current decompression routine was ported from lz4 v1.8.3, bumping lib/lz4 to v1.9.+ is certainly a huge work to be done later, so, we'd better fix it first. [1] https://lore.kernel.org/all/000000000000830d1205cf7f0477@google.com/ [2] https://github.com/lz4/lz4/commit/c5d6f8a8be3927c0bec91bcc58667a6cfad244ad# [3] https://lore.kernel.org/all/CC666AE8-4CA4-4951-B6FB-A2EFDE3AC03B@fb.com/ Link: https://lkml.kernel.org/r/20211111105048.2006070-1-guoxuenan@huawei.com Reported-by: syzbot+63d688f1d899c588fb71@syzkaller.appspotmail.com Signed-off-by: Guo Xuenan <guoxuenan@huawei.com> Reviewed-by: Nick Terrell <terrelln@fb.com> Acked-by: Gao Xiang <hsiangkao@linux.alibaba.com> Cc: Yann Collet <cyan@fb.com> Cc: Chengyang Fan <cy.fan@huawei.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-07-01lz4_decompress: declare LZ4_decompress_safe_withPrefix64k staticRajat Asthana1-1/+1
Declare LZ4_decompress_safe_withPrefix64k as static to fix sparse warning: > warning: symbol 'LZ4_decompress_safe_withPrefix64k' was not declared. > Should it be static? Link: https://lkml.kernel.org/r/20210511154345.610569-1-thisisrast7@gmail.com Signed-off-by: Rajat Asthana <thisisrast7@gmail.com> Reviewed-by: Nick Terrell <terrelln@fb.com> Cc: Gao Xiang <hsiangkao@redhat.com> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-12-15lib/lz4: explicitly support in-place decompressionGao Xiang1-1/+5
LZ4 final literal copy could be overlapped when doing in-place decompression, so it's unsafe to just use memcpy() on an optimized memcpy approach but memmove() instead. Upstream LZ4 has updated this years ago [1] (and the impact is non-sensible [2] plus only a few bytes remain), this commit just synchronizes LZ4 upstream code to the kernel side as well. It can be observed as EROFS in-place decompression failure on specific files when X86_FEATURE_ERMS is unsupported, memcpy() optimization of commit 59daa706fbec ("x86, mem: Optimize memcpy by avoiding memory false dependece") will be enabled then. Currently most modern x86-CPUs support ERMS, these CPUs just use "rep movsb" approach so no problem at all. However, it can still be verified with forcely disabling ERMS feature... arch/x86/lib/memcpy_64.S: ALTERNATIVE_2 "jmp memcpy_orig", "", X86_FEATURE_REP_GOOD, \ - "jmp memcpy_erms", X86_FEATURE_ERMS + "jmp memcpy_orig", X86_FEATURE_ERMS We didn't observe any strange on arm64/arm/x86 platform before since most memcpy() would behave in an increasing address order ("copy upwards" [3]) and it's the correct order of in-place decompression but it really needs an update to memmove() for sure considering it's an undefined behavior according to the standard and some unique optimization already exists in the kernel. [1] https://github.com/lz4/lz4/commit/33cb8518ac385835cc17be9a770b27b40cd0e15b [2] https://github.com/lz4/lz4/pull/717#issuecomment-497818921 [3] https://sourceware.org/bugzilla/show_bug.cgi?id=12518 Link: https://lkml.kernel.org/r/20201122030749.2698994-1-hsiangkao@redhat.com Signed-off-by: Gao Xiang <hsiangkao@redhat.com> Reviewed-by: Nick Terrell <terrelln@fb.com> Cc: Yann Collet <yann.collet.73@gmail.com> Cc: Miao Xie <miaoxie@huawei.com> Cc: Chao Yu <yuchao0@huawei.com> Cc: Li Guifu <bluce.liguifu@huawei.com> Cc: Guo Xuenan <guoxuenan@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-14lz4: fix kernel decompression speedNick Terrell1-9/+9
This patch replaces all memcpy() calls with LZ4_memcpy() which calls __builtin_memcpy() so the compiler can inline it. LZ4 relies heavily on memcpy() with a constant size being inlined. In x86 and i386 pre-boot environments memcpy() cannot be inlined because memcpy() doesn't get defined as __builtin_memcpy(). An equivalent patch has been applied upstream so that the next import won't lose this change [1]. I've measured the kernel decompression speed using QEMU before and after this patch for the x86_64 and i386 architectures. The speed-up is about 10x as shown below. Code Arch Kernel Size Time Speed v5.8 x86_64 11504832 B 148 ms 79 MB/s patch x86_64 11503872 B 13 ms 885 MB/s v5.8 i386 9621216 B 91 ms 106 MB/s patch i386 9620224 B 10 ms 962 MB/s I also measured the time to decompress the initramfs on x86_64, i386, and arm. All three show the same decompression speed before and after, as expected. [1] https://github.com/lz4/lz4/pull/890 Signed-off-by: Nick Terrell <terrelln@fb.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Yann Collet <yann.collet.73@gmail.com> Cc: Gao Xiang <gaoxiang25@huawei.com> Cc: Sven Schmidt <4sschmid@informatik.uni-hamburg.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Arvind Sankar <nivedita@alum.mit.edu> Link: http://lkml.kernel.org/r/20200803194022.2966806-1-nickrterrell@gmail.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-10lib/lz4/lz4_decompress.c: document deliberate use of `&'Joe Perches1-0/+3
This operation was intentional, but tools such as smatch will warn that it might not have been. Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Yann Collet <cyan@fb.com> Cc: Vasily Averin <vvs@virtuozzo.com> Cc: Gao Xiang <hsiangkao@aol.com> Link: http://lkml.kernel.org/r/3bf931c6ea0cae3e23f3485801986859851b4f04.camel@perches.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-10-31lib/lz4: update LZ4 decompressor moduleGao Xiang1-140/+341
Update the LZ4 compression module based on LZ4 v1.8.3 in order for the erofs file system to use the newest LZ4_decompress_safe_partial() which can now decode exactly the nb of bytes requested [1] to take place of the open hacked code in the erofs file system itself. Currently, apart from the erofs file system, no other users use LZ4_decompress_safe_partial, so no worry about the interface. In addition, LZ4 v1.8.x boosts up decompression speed compared to the current code which is based on LZ4 v1.7.3, mainly due to shortcut optimization for the specific common LZ4-sequences [2]. lzbench testdata (tested in kirin710, 8 cores, 4 big cores at 2189Mhz, 2GB DDR RAM at 1622Mhz, with enwik8 testdata [3]): Compressor name Compress. Decompress. Compr. size Ratio Filename memcpy 5004 MB/s 4924 MB/s 100000000 100.00 enwik8 lz4hc 1.7.3 -9 12 MB/s 653 MB/s 42203253 42.20 enwik8 lz4hc 1.8.0 -9 12 MB/s 908 MB/s 42203096 42.20 enwik8 lz4hc 1.8.3 -9 11 MB/s 965 MB/s 42203094 42.20 enwik8 [1] https://github.com/lz4/lz4/issues/566 https://github.com/lz4/lz4/commit/08d347b5b217b011ff7487130b79480d8cfdaeb8 [2] v1.8.1 perf: slightly faster compression and decompression speed https://github.com/lz4/lz4/commit/a31b7058cb97e4393da55e78a77a1c6f0c9ae038 v1.8.2 perf: slightly faster HC compression and decompression speed https://github.com/lz4/lz4/commit/45f8603aae389d34c689d3ff7427b314071ccd2c https://github.com/lz4/lz4/commit/1a191b3f8d26b50a7c1d41590b529ec308d768cd [3] http://mattmahoney.net/dc/textdata.html http://mattmahoney.net/dc/enwik8.zip Link: http://lkml.kernel.org/r/1537181207-21932-1-git-send-email-gaoxiang25@huawei.com Signed-off-by: Gao Xiang <gaoxiang25@huawei.com> Tested-by: Guo Xuenan <guoxuenan@huawei.com> Cc: Colin Ian King <colin.king@canonical.com> Cc: Yann Collet <yann.collet.73@gmail.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Fang Wei <fangwei1@huawei.com> Cc: Chao Yu <yuchao0@huawei.com> Cc: Miao Xie <miaoxie@huawei.com> Cc: Sven Schmidt <4sschmid@informatik.uni-hamburg.de> Cc: Kyungsik Lee <kyungsik.lee@lge.com> Cc: <weidu.du@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-10-03lib/lz4: make arrays static const, reduces object code sizeColin Ian King1-2/+2
Don't populate the read-only arrays dec32table and dec64table on the stack, instead make them both static const. Makes the object code smaller by over 10K bytes: Before: text data bss dec hex filename 31500 0 0 31500 7b0c lib/lz4/lz4_decompress.o After: text data bss dec hex filename 20237 176 0 20413 4fbd lib/lz4/lz4_decompress.o (gcc version 7.2.0 x86_64) Link: http://lkml.kernel.org/r/20170921221939.20820-1-colin.king@canonical.com Signed-off-by: Colin Ian King <colin.king@canonical.com> Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr> Cc: Sven Schmidt <4sschmid@informatik.uni-hamburg.de> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-24lib/lz4: remove back-compat wrappersSven Schmidt1-42/+0
Remove the functions introduced as wrappers for providing backwards compatibility to the prior LZ4 version. They're not needed anymore since there's no callers left. Link: http://lkml.kernel.org/r/1486321748-19085-6-git-send-email-4sschmid@informatik.uni-hamburg.de Signed-off-by: Sven Schmidt <4sschmid@informatik.uni-hamburg.de> Cc: Bongkyu Kim <bongkyu.kim@lge.com> Cc: Rui Salvaterra <rsalvaterra@gmail.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: David S. Miller <davem@davemloft.net> Cc: Anton Vorontsov <anton@enomsg.org> Cc: Colin Cross <ccross@android.com> Cc: Kees Cook <keescook@chromium.org> Cc: Tony Luck <tony.luck@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-24lib: update LZ4 compressor moduleSven Schmidt1-249/+456
Patch series "Update LZ4 compressor module", v7. This patchset updates the LZ4 compression module to a version based on LZ4 v1.7.3 allowing to use the fast compression algorithm aka LZ4 fast which provides an "acceleration" parameter as a tradeoff between high compression ratio and high compression speed. We want to use LZ4 fast in order to support compression in lustre and (mostly, based on that) investigate data reduction techniques in behalf of storage systems. Also, it will be useful for other users of LZ4 compression, as with LZ4 fast it is possible to enable applications to use fast and/or high compression depending on the usecase. For instance, ZRAM is offering a LZ4 backend and could benefit from an updated LZ4 in the kernel. LZ4 homepage: http://www.lz4.org/ LZ4 source repository: https://github.com/lz4/lz4 Source version: 1.7.3 Benchmark (taken from [1], Core i5-4300U @1.9GHz): ----------------|--------------|----------------|---------- Compressor | Compression | Decompression | Ratio ----------------|--------------|----------------|---------- memcpy | 4200 MB/s | 4200 MB/s | 1.000 LZ4 fast 50 | 1080 MB/s | 2650 MB/s | 1.375 LZ4 fast 17 | 680 MB/s | 2220 MB/s | 1.607 LZ4 fast 5 | 475 MB/s | 1920 MB/s | 1.886 LZ4 default | 385 MB/s | 1850 MB/s | 2.101 [1] http://fastcompression.blogspot.de/2015/04/sampling-or-faster-lz4.html [PATCH 1/5] lib: Update LZ4 compressor module [PATCH 2/5] lib/decompress_unlz4: Change module to work with new LZ4 module version [PATCH 3/5] crypto: Change LZ4 modules to work with new LZ4 module version [PATCH 4/5] fs/pstore: fs/squashfs: Change usage of LZ4 to work with new LZ4 version [PATCH 5/5] lib/lz4: Remove back-compat wrappers This patch (of 5): Update the LZ4 kernel module to LZ4 v1.7.3 by Yann Collet. The kernel module is inspired by the previous work by Chanho Min. The updated LZ4 module will not break existing code since the patchset contains appropriate changes. API changes: New method LZ4_compress_fast which differs from the variant available in kernel by the new acceleration parameter, allowing to trade compression ratio for more compression speed and vice versa. LZ4_decompress_fast is the respective decompression method, featuring a very fast decoder (multiple GB/s per core), able to reach RAM speed in multi-core systems. The decompressor allows to decompress data compressed with LZ4 fast as well as the LZ4 HC (high compression) algorithm. Also the useful functions LZ4_decompress_safe_partial and LZ4_compress_destsize were added. The latter reverses the logic by trying to compress as much data as possible from source to dest while the former aims to decompress partial blocks of data. A bunch of streaming functions were also added which allow compressig/decompressing data in multiple steps (so called "streaming mode"). The methods lz4_compress and lz4_decompress_unknownoutputsize are now known as LZ4_compress_default respectivley LZ4_decompress_safe. The old methods will be removed since there's no callers left in the code. [arnd@arndb.de: fix KERNEL_LZ4 support] Link: http://lkml.kernel.org/r/20170208211946.2839649-1-arnd@arndb.de [akpm@linux-foundation.org: simplify] [akpm@linux-foundation.org: fix the simplification] [4sschmid@informatik.uni-hamburg.de: fix performance regressions] Link: http://lkml.kernel.org/r/1486898178-17125-2-git-send-email-4sschmid@informatik.uni-hamburg.de [4sschmid@informatik.uni-hamburg.de: v8] Link: http://lkml.kernel.org/r/1487182598-15351-2-git-send-email-4sschmid@informatik.uni-hamburg.de Link: http://lkml.kernel.org/r/1486321748-19085-2-git-send-email-4sschmid@informatik.uni-hamburg.de Signed-off-by: Sven Schmidt <4sschmid@informatik.uni-hamburg.de> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Cc: Bongkyu Kim <bongkyu.kim@lge.com> Cc: Rui Salvaterra <rsalvaterra@gmail.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: David S. Miller <davem@davemloft.net> Cc: Anton Vorontsov <anton@enomsg.org> Cc: Colin Cross <ccross@android.com> Cc: Kees Cook <keescook@chromium.org> Cc: Tony Luck <tony.luck@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-05-24lz4: fix system halt at boot kernel on x86_64Krzysztof Kolasa1-1/+11
Sometimes, on x86_64, decompression fails with the following error: Decompressing Linux... Decoding failed -- System halted This condition is not needed for a 64bit kernel(from commit d5e7caf): if( ... || (op + COPYLENGTH) > oend) goto _output_error macro LZ4_SECURE_COPY() tests op and does not copy any data when op exceeds the value. added by analogy to lz4_uncompress_unknownoutputsize(...) Signed-off-by: Krzysztof Kolasa <kkolasa@winsoft.pl> Tested-by: Alexander Kuleshov <kuleshovmail@gmail.com> Tested-by: Caleb Jorden <cjorden@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-03-25lib/lz4: Pull out constant tablesRasmus Villemoes1-11/+7
There's no reason to allocate the dec{32,64}table on the stack; it just wastes a bunch of instructions setting them up and, of course, also consumes quite a bit of stack. Using size_t for such small integers is a little excessive. $ scripts/bloat-o-meter /tmp/built-in.o lib/built-in.o add/remove: 2/2 grow/shrink: 2/0 up/down: 1304/-1548 (-244) function old new delta lz4_decompress_unknownoutputsize 55 718 +663 lz4_decompress 55 632 +577 dec64table - 32 +32 dec32table - 32 +32 lz4_uncompress 747 - -747 lz4_uncompress_unknownoutputsize 801 - -801 The now inlined lz4_uncompress functions used to have a stack footprint of 176 bytes (according to -fstack-usage); their inlinees have increased their stack use from 32 bytes to 48 and 80 bytes, respectively. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-03-16LZ4 : fix the data abort issueJeHyeon Yeon1-0/+3
If the part of the compression data are corrupted, or the compression data is totally fake, the memory access over the limit is possible. This is the log from my system usning lz4 decompression. [6502]data abort, halting [6503]r0 0x00000000 r1 0x00000000 r2 0xdcea0ffc r3 0xdcea0ffc [6509]r4 0xb9ab0bfd r5 0xdcea0ffc r6 0xdcea0ff8 r7 0xdce80000 [6515]r8 0x00000000 r9 0x00000000 r10 0x00000000 r11 0xb9a98000 [6522]r12 0xdcea1000 usp 0x00000000 ulr 0x00000000 pc 0x820149bc [6528]spsr 0x400001f3 and the memory addresses of some variables at the moment are ref:0xdcea0ffc, op:0xdcea0ffc, oend:0xdcea1000 As you can see, COPYLENGH is 8bytes, so @ref and @op can access the momory over @oend. Signed-off-by: JeHyeon Yeon <tom.yeon@windriver.com> Reviewed-by: David Sterba <dsterba@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-07-03lz4: add overrun checks to lz4_uncompress_unknownoutputsize()Greg Kroah-Hartman1-1/+5
Jan points out that I forgot to make the needed fixes to the lz4_uncompress_unknownoutputsize() function to mirror the changes done in lz4_decompress() with regards to potential pointer overflows. The only in-kernel user of this function is the zram code, which only takes data from a valid compressed buffer that it made itself, so it's not a big issue. But due to external kernel modules using this function, it's better to be safe here. Reported-by: Jan Beulich <JBeulich@suse.com> Cc: "Don A. Bailey" <donb@securitymouse.com> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-06-27lz4: fix another possible overrunGreg Kroah-Hartman1-1/+3
There is one other possible overrun in the lz4 code as implemented by Linux at this point in time (which differs from the upstream lz4 codebase, but will get synced at in a future kernel release.) As pointed out by Don, we also need to check the overflow in the data itself. While we are at it, replace the odd error return value with just a "simple" -1 value as the return value is never used for anything other than a basic "did this work or not" check. Reported-by: "Don A. Bailey" <donb@securitymouse.com> Reported-by: Willy Tarreau <w@1wt.eu> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-06-23lz4: ensure length does not wrapGreg Kroah-Hartman1-0/+2
Given some pathologically compressed data, lz4 could possibly decide to wrap a few internal variables, causing unknown things to happen. Catch this before the wrapping happens and abort the decompression. Reported-by: "Don A. Bailey" <donb@securitymouse.com> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-09-11lz4: fix compression/decompression signedness mismatchSergey Senozhatsky1-4/+4
LZ4 compression and decompression functions require different in signedness input/output parameters: unsigned char for compression and signed char for decompression. Change decompression API to require "(const) unsigned char *". Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Kyungsik Lee <kyungsik.lee@lge.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Yann Collet <yann.collet.73@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-08-23lib/lz4: correct the LZ4 licenseRichard Laager1-3/+3
The LZ4 code is listed as using the "BSD 2-Clause License". Signed-off-by: Richard Laager <rlaager@wiktel.com> Acked-by: Kyungsik Lee <kyungsik.lee@lge.com> Cc: Chanho Min <chanho.min@lge.com> Cc: Richard Yao <ryao@gentoo.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> [ The 2-clause BSD can be just converted into GPL, but that's rude and pointless, so don't do it - Linus ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-07-09lib: add support for LZ4-compressed kernelKyungsik Lee1-1/+1
Add support for extracting LZ4-compressed kernel images, as well as LZ4-compressed ramdisk images in the kernel boot process. Signed-off-by: Kyungsik Lee <kyungsik.lee@lge.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Borislav Petkov <bp@alien8.de> Cc: Florian Fainelli <florian@openwrt.org> Cc: Yann Collet <yann.collet.73@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-07-09decompressor: add LZ4 decompressor moduleKyungsik Lee1-0/+326
Add support for LZ4 decompression in the Linux Kernel. LZ4 Decompression APIs for kernel are based on LZ4 implementation by Yann Collet. Benchmark Results(PATCH v3) Compiler: Linaro ARM gcc 4.6.2 1. ARMv7, 1.5GHz based board Kernel: linux 3.4 Uncompressed Kernel Size: 14MB Compressed Size Decompression Speed LZO 6.7MB 20.1MB/s, 25.2MB/s(UA) LZ4 7.3MB 29.1MB/s, 45.6MB/s(UA) 2. ARMv7, 1.7GHz based board Kernel: linux 3.7 Uncompressed Kernel Size: 14MB Compressed Size Decompression Speed LZO 6.0MB 34.1MB/s, 52.2MB/s(UA) LZ4 6.5MB 86.7MB/s - UA: Unaligned memory Access support - Latest patch set for LZO applied This patch set is for adding support for LZ4-compressed Kernel. LZ4 is a very fast lossless compression algorithm and it also features an extremely fast decoder [1]. But we have five of decompressors already and one question which does arise, however, is that of where do we stop adding new ones? This issue had been discussed and came to the conclusion [2]. Russell King said that we should have: - one decompressor which is the fastest - one decompressor for the highest compression ratio - one popular decompressor (eg conventional gzip) If we have a replacement one for one of these, then it should do exactly that: replace it. The benchmark shows that an 8% increase in image size vs a 66% increase in decompression speed compared to LZO(which has been known as the fastest decompressor in the Kernel). Therefore the "fast but may not be small" compression title has clearly been taken by LZ4 [3]. [1] http://code.google.com/p/lz4/ [2] http://thread.gmane.org/gmane.linux.kbuild.devel/9157 [3] http://thread.gmane.org/gmane.linux.kbuild.devel/9347 LZ4 homepage: http://fastcompression.blogspot.com/p/lz4.html LZ4 source repository: http://code.google.com/p/lz4/ Signed-off-by: Kyungsik Lee <kyungsik.lee@lge.com> Signed-off-by: Yann Collet <yann.collet.73@gmail.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Borislav Petkov <bp@alien8.de> Cc: Florian Fainelli <florian@openwrt.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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