From: Nick Terrell <nickrterrell@gmail.com>
To: Nick Terrell <terrelln@fb.com>
Cc: linux-kernel@vger.kernel.org, Chris Mason <clm@fb.com>,
linux-kbuild@vger.kernel.org, x86@kernel.org,
gregkh@linuxfoundation.org, Petr Malat <oss@malat.biz>,
Kees Cook <keescook@chromium.org>,
Kernel Team <Kernel-team@fb.com>,
Nick Terrell <nickrterrell@gmail.com>,
Adam Borowski <kilobyte@angband.pl>,
Patrick Williams <patrickw3@fb.com>,
rmikey@fb.com, mingo@kernel.org,
Patrick Williams <patrick@stwcx.xyz>,
Sedat Dilek <sedat.dilek@gmail.com>
Subject: [PATCH v4 6/8] x86: bump ZO_z_extra_bytes margin for zstd
Date: Tue, 31 Mar 2020 22:39:11 -0700 [thread overview]
Message-ID: <20200401053913.216783-7-nickrterrell@gmail.com> (raw)
In-Reply-To: <20200401053913.216783-1-nickrterrell@gmail.com>
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>
---
| 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--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
next prev parent reply other threads:[~2020-04-01 5:39 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-01 5:39 [PATCH v4 0/8] Add support for ZSTD-compressed kernel and initramfs Nick Terrell
2020-04-01 5:39 ` [PATCH v4 1/8] lib: prepare zstd for preboot environment Nick Terrell
2020-04-01 5:39 ` [PATCH v4 2/8] lib: prepare xxhash " Nick Terrell
2020-04-01 5:39 ` [PATCH v4 3/8] lib: add zstd support to decompress Nick Terrell
2020-04-01 5:39 ` [PATCH v4 4/8] init: add support for zstd compressed kernel Nick Terrell
2020-04-01 5:39 ` [PATCH v4 5/8] usr: add support for zstd compressed initramfs Nick Terrell
2020-04-01 5:39 ` Nick Terrell [this message]
2020-04-01 9:33 ` [PATCH v4 6/8] x86: bump ZO_z_extra_bytes margin for zstd Borislav Petkov
2020-04-01 17:33 ` Nick Terrell
2020-04-02 15:58 ` Borislav Petkov
2020-04-02 20:25 ` Nick Terrell
2020-04-03 10:19 ` Borislav Petkov
2020-04-06 10:47 ` Sedat Dilek
2020-04-01 5:39 ` [PATCH v4 7/8] x86: Add support for ZSTD compressed kernel Nick Terrell
2020-04-01 5:39 ` [PATCH v4 8/8] .gitignore: add ZSTD-compressed files Nick Terrell
2020-04-01 10:59 ` [PATCH v4 0/8] Add support for ZSTD-compressed kernel and initramfs Gabriel C
2020-04-01 17:36 ` Sedat Dilek
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