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| author | Nick Terrell <terrelln@fb.com> | 2020-07-30 21:08:38 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2020-07-31 11:49:08 +0200 |
| commit | 0fe4f4ef8cc8e15a8f29f08f4be6128395f125f6 (patch) | |
| tree | 8d232b77e48c68b061254cf7eae412bde867a074 /arch | |
| parent | usr: Add support for zstd compressed initramfs (diff) | |
| download | linux-0fe4f4ef8cc8e15a8f29f08f4be6128395f125f6.tar.xz linux-0fe4f4ef8cc8e15a8f29f08f4be6128395f125f6.zip | |
x86: Bump ZO_z_extra_bytes margin for zstd
Bump the ZO_z_extra_bytes margin for zstd.
Zstd needs 3 bytes per 128 KB, and has a 22 byte fixed overhead.
Zstd needs to maintain 128 KB of space at all times, since that is
the maximum block size. See the comments regarding in-place
decompression added in lib/decompress_unzstd.c for details.
The existing code is written so that all the compression algorithms use
the same ZO_z_extra_bytes. It is taken to be the maximum of the growth
rate plus the maximum fixed overhead. The comments just above this diff
state that:
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/20200730190841.2071656-6-nickrterrell@gmail.com
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/boot/header.S | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S index 735ad7f21ab0..6dbd7e9f74c9 100644 --- a/arch/x86/boot/header.S +++ b/arch/x86/boot/header.S @@ -539,8 +539,14 @@ pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr # the size-dependent part now grows so fast. # # extra_bytes = (uncompressed_size >> 8) + 65536 +# +# ZSTD compressed data grows by at most 3 bytes per 128K, and only has a 22 +# byte fixed overhead but has a maximum block size of 128K, so it needs a +# larger margin. +# +# extra_bytes = (uncompressed_size >> 8) + 131072 -#define ZO_z_extra_bytes ((ZO_z_output_len >> 8) + 65536) +#define ZO_z_extra_bytes ((ZO_z_output_len >> 8) + 131072) #if ZO_z_output_len > ZO_z_input_len # define ZO_z_extract_offset (ZO_z_output_len + ZO_z_extra_bytes - \ ZO_z_input_len) |