Messages in this thread | | | Date | Wed, 1 Apr 2020 11:33:10 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v4 6/8] x86: bump ZO_z_extra_bytes margin for zstd |
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On Tue, Mar 31, 2020 at 10:39:11PM -0700, Nick Terrell wrote: > From: Nick Terrell <terrelln@fb.com> > > 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. > > Reviewed-by: Kees Cook <keescook@chromium.org> > Tested-by: Sedat Dilek <sedat.dilek@gmail.com> > Signed-off-by: Nick Terrell <terrelln@fb.com> > --- > arch/x86/boot/header.S | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S > index 97d9b6d6c1af..b820875c5c95 100644 > --- a/arch/x86/boot/header.S > +++ b/arch/x86/boot/header.S > @@ -536,8 +536,14 @@ 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) > --
So why is this change unconditional if only this compression alg. needs it?
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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