From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pj1-f67.google.com ([209.85.216.67]:54668 "EHLO mail-pj1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731589AbgDAFi7 (ORCPT ); Wed, 1 Apr 2020 01:38:59 -0400 From: Nick Terrell Subject: [PATCH v4 6/8] x86: bump ZO_z_extra_bytes margin for zstd Date: Tue, 31 Mar 2020 22:39:11 -0700 Message-Id: <20200401053913.216783-7-nickrterrell@gmail.com> In-Reply-To: <20200401053913.216783-1-nickrterrell@gmail.com> References: <20200401053913.216783-1-nickrterrell@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Nick Terrell Cc: linux-kernel@vger.kernel.org, Chris Mason , linux-kbuild@vger.kernel.org, x86@kernel.org, gregkh@linuxfoundation.org, Petr Malat , Kees Cook , Kernel Team , Nick Terrell , Adam Borowski , Patrick Williams , rmikey@fb.com, mingo@kernel.org, Patrick Williams , Sedat Dilek From: Nick Terrell 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 Tested-by: Sedat Dilek Signed-off-by: Nick Terrell --- 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) -- 2.26.0