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Commit 5746f055 authored by Jan H. Schönherr's avatar Jan H. Schönherr Committed by Ingo Molnar
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x86/boot: Provide more slack space during decompression 



The current slack space is not enough for LZ4, which has a worst case
overhead of 0.4% for data that cannot be further compressed. With
an LZ4 compressed kernel with an embedded initrd, the output is likely
to overwrite the input.

Increase the slack space to avoid that.

Signed-off-by: default avatarJan H. Schönherr <jschoenh@amazon.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1503842124-29718-1-git-send-email-jschoenh@amazon.de


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent eaa2f87c

arch/x86/boot/header.S

+7 −1
Original line number Diff line number Diff line
@@ -520,8 +520,14 @@ pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr 
# the description in lib/decompressor_xxx.c for specific information.

#

# extra_bytes = (uncompressed_size >> 12) + 65536 + 128

#

# LZ4 is even worse: data that cannot be further compressed grows by 0.4%,

# or one byte per 256 bytes. OTOH, we can safely get rid of the +128 as

# the size-dependent part now grows so fast.

#

# extra_bytes = (uncompressed_size >> 8) + 65536



#define ZO_z_extra_bytes	((ZO_z_output_len >> 12) + 65536 + 128)

#define ZO_z_extra_bytes	((ZO_z_output_len >> 8) + 65536)

#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)