The main change in this cycle was to add support for ZSTD-compressed

kernel and initrd images.
 
 ZSTD has a very fast decompressor, yet it compresses better than gzip.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-boot-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 boot updates from Ingo Molnar:
 "The main change in this cycle was to add support for ZSTD-compressed
  kernel and initrd images.

  ZSTD has a very fast decompressor, yet it compresses better than gzip"

* tag 'x86-boot-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Documentation: dontdiff: Add zstd compressed files
  .gitignore: Add ZSTD-compressed files
  x86: Add support for ZSTD compressed kernel
  x86: Bump ZO_z_extra_bytes margin for zstd
  usr: Add support for zstd compressed initramfs
  init: Add support for zstd compressed kernel
  lib: Add zstd support to decompress
  lib: Prepare zstd for preboot environment, improve performance
This commit is contained in:
Linus Torvalds 2020-08-03 16:03:23 -07:00
commit c0dfadfed8
21 changed files with 469 additions and 26 deletions

View file

@ -413,6 +413,28 @@ quiet_cmd_xzkern = XZKERN $@
quiet_cmd_xzmisc = XZMISC $@
cmd_xzmisc = cat $(real-prereqs) | $(XZ) --check=crc32 --lzma2=dict=1MiB > $@
# ZSTD
# ---------------------------------------------------------------------------
# Appends the uncompressed size of the data using size_append. The .zst
# format has the size information available at the beginning of the file too,
# but it's in a more complex format and it's good to avoid changing the part
# of the boot code that reads the uncompressed size.
#
# Note that the bytes added by size_append will make the zstd tool think that
# the file is corrupt. This is expected.
#
# zstd uses a maximum window size of 8 MB. zstd22 uses a maximum window size of
# 128 MB. zstd22 is used for kernel compression because it is decompressed in a
# single pass, so zstd doesn't need to allocate a window buffer. When streaming
# decompression is used, like initramfs decompression, zstd22 should likely not
# be used because it would require zstd to allocate a 128 MB buffer.
quiet_cmd_zstd = ZSTD $@
cmd_zstd = { cat $(real-prereqs) | $(ZSTD) -19; $(size_append); } > $@
quiet_cmd_zstd22 = ZSTD22 $@
cmd_zstd22 = { cat $(real-prereqs) | $(ZSTD) -22 --ultra; $(size_append); } > $@
# ASM offsets
# ---------------------------------------------------------------------------