From 315a5ea0a97a5795d1a3e28e9ff42cc2bfc630d7 Mon Sep 17 00:00:00 2001
From: Eugene Syromiatnikov <esyr@redhat.com>
Date: Mon, 26 Jul 2021 22:21:00 +0200
Subject: [PATCH] gen_provides.sh: make microcode header decoding
 endianness-agnostic

Unfortunately, hexdump doesn't support enforcing endianness of printed
fields (or printing of fields out of order, for that matter), and there
is no trivial analogue of dd conv=swab for 4-byte swaps, so we use xxd's
so-called "little-endian mode" to convert the endianness to big endian,
then print fields per-byte with hexdump and process the constructed
0xaabbccdd numbers.  Note that this also swaps the order of the date fields
to mm.dd.yyYY (instead of YYyy.mm.dd).

* gen_provides.sh: Pipe dd, xxd, and xxd -r to swap quad-bytes into big
endian, print them as sequences of bytes to construct the fields
of necessary size.
* microcode_ctl.spec (BuildRequires): Add /usr/bin/xxd.

Resolves: #1880064
Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
---
 gen_provides.sh    | 41 +++++++++++++++++++++++++++++++----------
 microcode_ctl.spec |  4 ++--
 2 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/gen_provides.sh b/gen_provides.sh
index c719694..16abba1 100755
--- a/gen_provides.sh
+++ b/gen_provides.sh
@@ -43,25 +43,43 @@ for f in $(grep -E '/intel-ucode.*/[0-9a-f][0-9a-f]-[0-9a-f][0-9a-f]-[0-9a-f][0-
 
 			# ext_sig, 12 bytes in size
 			IFS=' ' read cpuid pf_mask <<- EOF
-			$(hexdump -s "$skip" -n 8 \
-				-e '"" 1/4 "%08x " 1/4 "%u" "\n"' "$f")
+			$(dd if="$f" ibs=1 skip="$skip" count=8 status=none \
+				| xxd -e -g4 | xxd -r | hexdump -n 8 \
+				-e '"" 4/1 "%02x" " 0x" 4/1 "%02x" "\n"')
 			EOF
+			# Converting values from the constructed %#08x format
+			pf_mask="$((pf_mask))"
 
 			skip="$((skip + 12))"
 			ext_sig_pos="$((ext_sig_pos + 1))"
 		else
 			# Microcode header, 48 bytes, last 3 fields reserved
+			# cksum, ldrver are ignored
 			IFS=' ' read hdrver rev \
-			       date_y date_d date_m \
+			       date_m date_d date_y \
 			       cpuid cksum ldrver \
 			       pf_mask datasz totalsz <<- EOF
-			$(hexdump -s "$skip" -n 36 \
-				-e '"" 1/4 "%u " 1/4 "%#x " \
-			               1/2 "%04x " 1/1 "%02x " 1/1 "%02x " \
-				       1/4 "%08x " 1/4 "%x " 1/4 "%#x " \
-				       1/4 "%u " 1/4 "%u " 1/4 "%u" "\n"' "$f")
+			$(dd if="$f" ibs=1 skip="$skip" count=36 status=none \
+				| xxd -e -g4 | xxd -r | hexdump -n 36 \
+				-e '"0x" 4/1 "%02x" " 0x" 4/1 "%02x" " " \
+			               1/1 "%02x " 1/1 "%02x " 2/1 "%02x" " " \
+				       4/1 "%02x" " 0x" 4/1 "%02x" " 0x" 4/1 "%02x" \
+				       " 0x" 4/1 "%x" \
+				       " 0x" 4/1 "%02x" " 0x" 4/1 "%02x" "\n"')
 			EOF
 
+			# Converting values from the constructed %#08x format
+			rev="$(printf '%#x' "$((rev))")"
+			pf_mask="$((pf_mask))"
+			datasz="$((datasz))"
+			totalsz="$((totalsz))"
+
+			# Skipping files with unexpected hdrver value
+			[ 1 = "$((hdrver))" ] || {
+				echo "$f+$skip@$file_sz: incorrect hdrver $((hdrver))" >&2
+				break
+			}
+
 			[ 0 != "$datasz" ] || datasz=2000
 			[ 0 != "$totalsz" ] || totalsz=2048
 
@@ -80,9 +98,12 @@ for f in $(grep -E '/intel-ucode.*/[0-9a-f][0-9a-f]-[0-9a-f][0-9a-f]-[0-9a-f][0-
 				# ext_sig table header, 20 bytes in size,
 				# last 3 fields are reserved.
 				IFS=' ' read ext_sig_cnt  <<- EOF
-				$(hexdump -s "$skip" -n 4 \
-					-e '"" 1/4 "%u" "\n"' "$f")
+				$(dd if="$f" ibs=1 skip="$skip" count=4 status=none \
+					| xxd -e -g4 | hexdump -n 4 \
+					-e '"0x" 4/1 "%02x" "\n"')
 				EOF
+				# Converting values from the constructed format
+				ext_sig_cnt="$((ext_sig_cnt))"
 
 				skip="$((skip + 20))"
 			else
diff --git a/microcode_ctl.spec b/microcode_ctl.spec
index 09f783b..eeed042 100644
--- a/microcode_ctl.spec
+++ b/microcode_ctl.spec
@@ -124,8 +124,8 @@ Source1002:     gen_updates2.py
 
 ExclusiveArch:  %{ix86} x86_64
 BuildRequires:  systemd-units
-# hexdump is used in gen_provides.sh
-BuildRequires:  coreutils util-linux
+# dd, hexdump, and xxd are used in gen_provides.sh
+BuildRequires:  coreutils util-linux /usr/bin/xxd
 # gen_updates2.py requires python interpreter
 BuildRequires:  /usr/bin/python3
 Requires:       coreutils