In preparation to enable -Wimplicit-fallthrough for Clang, fix multiple
warnings by explicitly adding multiple break statements instead of
letting the code fall through to the next case, and by replacing a
number of /* fall through */ comments with the new pseudo-keyword
macro fallthrough.
Notice that Clang doesn't recognize /* Fall through */ comments as
implicit fall-through markings.
Link: https://github.com/KSPP/linux/issues/115
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
This reverts commit 6a9dc5fd61 ("lib: Revert use of fallthrough
pseudo-keyword in lib/")
Now that we can build arch/powerpc/boot/ free of -Wimplicit-fallthrough,
re-enable these fixes for lib/.
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://github.com/ClangBuiltLinux/linux/issues/236
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
The following build error for powerpc64 was reported by Nathan Chancellor:
"$ scripts/config --file arch/powerpc/configs/powernv_defconfig -e KERNEL_XZ
$ make -skj"$(nproc)" ARCH=powerpc CROSS_COMPILE=powerpc64le-linux- distclean powernv_defconfig zImage
...
In file included from arch/powerpc/boot/../../../lib/decompress_unxz.c:234,
from arch/powerpc/boot/decompress.c:38:
arch/powerpc/boot/../../../lib/xz/xz_dec_stream.c: In function 'dec_main':
arch/powerpc/boot/../../../lib/xz/xz_dec_stream.c:586:4: error: 'fallthrough' undeclared (first use in this function)
586 | fallthrough;
| ^~~~~~~~~~~
This will end up affecting distribution configurations such as Debian
and OpenSUSE according to my testing. I am not sure what the solution
is, the PowerPC wrapper does not set -D__KERNEL__ so I am not sure
that compiler_attributes.h can be safely included."
In order to avoid these sort of problems, it seems that the best
solution is to use /* fall through */ comments instead of the
fallthrough pseudo-keyword macro in lib/, for now.
Reported-by: Nathan Chancellor <natechancellor@gmail.com>
Fixes: df561f6688 ("treewide: Use fallthrough pseudo-keyword")
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-and-tested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
These changes are necessary to get the build to work in the preboot
environment, and to get reasonable performance:
- Remove a double definition of the CHECK_F macro when the zstd
library is amalgamated.
- Switch ZSTD_copy8() to __builtin_memcpy(), because in the preboot
environment on x86 gcc can't inline `memcpy()` otherwise.
- Limit the gcc hack in ZSTD_wildcopy() to the broken gcc version. See
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81388.
ZSTD_copy8() and ZSTD_wildcopy() are in the core of the zstd hot loop.
So outlining these calls to memcpy(), and having an extra branch are very
detrimental to performance.
Signed-off-by: Nick Terrell <terrelln@fb.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200730190841.2071656-2-nickrterrell@gmail.com
Currently, compiler_types.h #defines __inline as inline (and further
#defines inline to automatically attach some attributes), so this does
not change functionality. It serves as preparation for removing the
#define of __inline.
While at it, also remove the __attribute__((unused)) - it's already
included in the definition of the inline macro, and "open-coded"
__attribute__(()) should be avoided.
Since commit a95b37e20d (kbuild: get <linux/compiler_types.h> out of
<linux/kconfig.h>), compiler_types.h is automatically included by all
kernel C code - i.e., the definition of inline including the unused
attribute is guaranteed to be in effect whenever ZSTD_STATIC is
expanded.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Add SPDX license identifiers to all Make/Kconfig files which:
- Have no license information of any form
These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:
GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
In preparation to enabling -Wimplicit-fallthrough, mark switch
cases where we are expecting to fall through.
This patch fixes the following warnings:
lib/zstd/bitstream.h:261:30: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/zstd/bitstream.h:262:30: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/zstd/bitstream.h:263:30: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/zstd/bitstream.h:264:30: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/zstd/bitstream.h:265:30: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/zstd/compress.c:3183:16: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/zstd/decompress.c:1770:18: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/zstd/decompress.c:2376:15: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/zstd/decompress.c:2404:15: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/zstd/decompress.c:2435:16: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/zstd/huf_compress.c: In function ‘HUF_compress1X_usingCTable’:
lib/zstd/huf_compress.c:535:5: warning: this statement may fall through [-Wimplicit-fallthrough=]
if (sizeof((stream)->bitContainer) * 8 < HUF_TABLELOG_MAX * 4 + 7) \
^
lib/zstd/huf_compress.c:558:54: note: in expansion of macro ‘HUF_FLUSHBITS_2’
case 3: HUF_encodeSymbol(&bitC, ip[n + 2], CTable); HUF_FLUSHBITS_2(&bitC);
^~~~~~~~~~~~~~~
lib/zstd/huf_compress.c:559:2: note: here
case 2: HUF_encodeSymbol(&bitC, ip[n + 1], CTable); HUF_FLUSHBITS_1(&bitC);
^~~~
lib/zstd/huf_compress.c:531:5: warning: this statement may fall through [-Wimplicit-fallthrough=]
if (sizeof((stream)->bitContainer) * 8 < HUF_TABLELOG_MAX * 2 + 7) \
^
lib/zstd/huf_compress.c:559:54: note: in expansion of macro ‘HUF_FLUSHBITS_1’
case 2: HUF_encodeSymbol(&bitC, ip[n + 1], CTable); HUF_FLUSHBITS_1(&bitC);
^~~~~~~~~~~~~~~
lib/zstd/huf_compress.c:560:2: note: here
case 1: HUF_encodeSymbol(&bitC, ip[n + 0], CTable); HUF_FLUSHBITS(&bitC);
^~~~
AR lib/zstd//built-in.a
Warning level 3 was used: -Wimplicit-fallthrough=3
This patch is part of the ongoing efforts to enabling -Wimplicit-fallthrough.
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Now, Kbuild nicely handles composite objects to avoid multiple
definition.
Makefiles can simply add the same objects multiple times across
composite objects.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Add zstd compression and decompression kernel modules.
zstd offers a wide varity of compression speed and quality trade-offs.
It can compress at speeds approaching lz4, and quality approaching lzma.
zstd decompressions at speeds more than twice as fast as zlib, and
decompression speed remains roughly the same across all compression levels.
The code was ported from the upstream zstd source repository. The
`linux/zstd.h` header was modified to match linux kernel style.
The cross-platform and allocation code was stripped out. Instead zstd
requires the caller to pass a preallocated workspace. The source files
were clang-formatted [1] to match the Linux Kernel style as much as
possible. Otherwise, the code was unmodified. We would like to avoid
as much further manual modification to the source code as possible, so it
will be easier to keep the kernel zstd up to date.
I benchmarked zstd compression as a special character device. I ran zstd
and zlib compression at several levels, as well as performing no
compression, which measure the time spent copying the data to kernel space.
Data is passed to the compresser 4096 B at a time. The benchmark file is
located in the upstream zstd source repository under
`contrib/linux-kernel/zstd_compress_test.c` [2].
I ran the benchmarks on a Ubuntu 14.04 VM with 2 cores and 4 GiB of RAM.
The VM is running on a MacBook Pro with a 3.1 GHz Intel Core i7 processor,
16 GB of RAM, and a SSD. I benchmarked using `silesia.tar` [3], which is
211,988,480 B large. Run the following commands for the benchmark:
sudo modprobe zstd_compress_test
sudo mknod zstd_compress_test c 245 0
sudo cp silesia.tar zstd_compress_test
The time is reported by the time of the userland `cp`.
The MB/s is computed with
1,536,217,008 B / time(buffer size, hash)
which includes the time to copy from userland.
The Adjusted MB/s is computed with
1,536,217,088 B / (time(buffer size, hash) - time(buffer size, none)).
The memory reported is the amount of memory the compressor requests.
| Method | Size (B) | Time (s) | Ratio | MB/s | Adj MB/s | Mem (MB) |
|----------|----------|----------|-------|---------|----------|----------|
| none | 11988480 | 0.100 | 1 | 2119.88 | - | - |
| zstd -1 | 73645762 | 1.044 | 2.878 | 203.05 | 224.56 | 1.23 |
| zstd -3 | 66988878 | 1.761 | 3.165 | 120.38 | 127.63 | 2.47 |
| zstd -5 | 65001259 | 2.563 | 3.261 | 82.71 | 86.07 | 2.86 |
| zstd -10 | 60165346 | 13.242 | 3.523 | 16.01 | 16.13 | 13.22 |
| zstd -15 | 58009756 | 47.601 | 3.654 | 4.45 | 4.46 | 21.61 |
| zstd -19 | 54014593 | 102.835 | 3.925 | 2.06 | 2.06 | 60.15 |
| zlib -1 | 77260026 | 2.895 | 2.744 | 73.23 | 75.85 | 0.27 |
| zlib -3 | 72972206 | 4.116 | 2.905 | 51.50 | 52.79 | 0.27 |
| zlib -6 | 68190360 | 9.633 | 3.109 | 22.01 | 22.24 | 0.27 |
| zlib -9 | 67613382 | 22.554 | 3.135 | 9.40 | 9.44 | 0.27 |
I benchmarked zstd decompression using the same method on the same machine.
The benchmark file is located in the upstream zstd repo under
`contrib/linux-kernel/zstd_decompress_test.c` [4]. The memory reported is
the amount of memory required to decompress data compressed with the given
compression level. If you know the maximum size of your input, you can
reduce the memory usage of decompression irrespective of the compression
level.
| Method | Time (s) | MB/s | Adjusted MB/s | Memory (MB) |
|----------|----------|---------|---------------|-------------|
| none | 0.025 | 8479.54 | - | - |
| zstd -1 | 0.358 | 592.15 | 636.60 | 0.84 |
| zstd -3 | 0.396 | 535.32 | 571.40 | 1.46 |
| zstd -5 | 0.396 | 535.32 | 571.40 | 1.46 |
| zstd -10 | 0.374 | 566.81 | 607.42 | 2.51 |
| zstd -15 | 0.379 | 559.34 | 598.84 | 4.61 |
| zstd -19 | 0.412 | 514.54 | 547.77 | 8.80 |
| zlib -1 | 0.940 | 225.52 | 231.68 | 0.04 |
| zlib -3 | 0.883 | 240.08 | 247.07 | 0.04 |
| zlib -6 | 0.844 | 251.17 | 258.84 | 0.04 |
| zlib -9 | 0.837 | 253.27 | 287.64 | 0.04 |
Tested in userland using the test-suite in the zstd repo under
`contrib/linux-kernel/test/UserlandTest.cpp` [5] by mocking the kernel
functions. Fuzz tested using libfuzzer [6] with the fuzz harnesses under
`contrib/linux-kernel/test/{RoundTripCrash.c,DecompressCrash.c}` [7] [8]
with ASAN, UBSAN, and MSAN. Additionaly, it was tested while testing the
BtrFS and SquashFS patches coming next.
[1] https://clang.llvm.org/docs/ClangFormat.html
[2] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/zstd_compress_test.c
[3] http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia
[4] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/zstd_decompress_test.c
[5] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/test/UserlandTest.cpp
[6] http://llvm.org/docs/LibFuzzer.html
[7] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/test/RoundTripCrash.c
[8] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/test/DecompressCrash.c
zstd source repository: https://github.com/facebook/zstd
Signed-off-by: Nick Terrell <terrelln@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
Gustavo A. R. Silva
Nick Desaulniers
Nick Terrell
Rasmus Villemoes
Thomas Gleixner
Gustavo A. R. Silva
Masahiro Yamada