scripts: add decodecode from Linux

The script decodecode can be used to disassemble the 'Code:' line  written
when an exception occurs.

The script is copied from Linux v4.16.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

diff --git a/scripts/decodecode b/scripts/decodecode
new file mode 100755 (executable)
index 0000000..9cef558
--- /dev/null
+++ b/scripts/decodecode
@@ -0,0 +1,125 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# Disassemble the Code: line in Linux oopses
+# usage: decodecode < oops.file
+#
+# options: set env. variable AFLAGS=options to pass options to "as";
+# e.g., to decode an i386 oops on an x86_64 system, use:
+# AFLAGS=--32 decodecode < 386.oops
+
+cleanup() {
+       rm -f $T $T.s $T.o $T.oo $T.aa $T.dis
+       exit 1
+}
+
+die() {
+       echo "$@"
+       exit 1
+}
+
+trap cleanup EXIT
+
+T=`mktemp` || die "cannot create temp file"
+code=
+cont=
+
+while read i ; do
+
+case "$i" in
+*Code:*)
+       code=$i
+       cont=yes
+       ;;
+*)
+       [ -n "$cont" ] && {
+               xdump="$(echo $i | grep '^[[:xdigit:]<>[:space:]]\+$')"
+               if [ -n "$xdump" ]; then
+                       code="$code $xdump"
+               else
+                       cont=
+               fi
+       }
+       ;;
+esac
+
+done
+
+if [ -z "$code" ]; then
+       rm $T
+       exit
+fi
+
+echo $code
+code=`echo $code | sed -e 's/.*Code: //'`
+
+width=`expr index "$code" ' '`
+width=$((($width-1)/2))
+case $width in
+1) type=byte ;;
+2) type=2byte ;;
+4) type=4byte ;;
+esac
+
+disas() {
+       ${CROSS_COMPILE}as $AFLAGS -o $1.o $1.s > /dev/null 2>&1
+
+       if [ "$ARCH" = "arm" ]; then
+               if [ $width -eq 2 ]; then
+                       OBJDUMPFLAGS="-M force-thumb"
+               fi
+
+               ${CROSS_COMPILE}strip $1.o
+       fi
+
+       if [ "$ARCH" = "arm64" ]; then
+               if [ $width -eq 4 ]; then
+                       type=inst
+               fi
+
+               ${CROSS_COMPILE}strip $1.o
+       fi
+
+       ${CROSS_COMPILE}objdump $OBJDUMPFLAGS -S $1.o | \
+               grep -v "/tmp\|Disassembly\|\.text\|^$" > $1.dis 2>&1
+}
+
+marker=`expr index "$code" "\<"`
+if [ $marker -eq 0 ]; then
+       marker=`expr index "$code" "\("`
+fi
+
+touch $T.oo
+if [ $marker -ne 0 ]; then
+       echo All code >> $T.oo
+       echo ======== >> $T.oo
+       beforemark=`echo "$code"`
+       echo -n "       .$type 0x" > $T.s
+       echo $beforemark | sed -e 's/ /,0x/g; s/[<>()]//g' >> $T.s
+       disas $T
+       cat $T.dis >> $T.oo
+       rm -f $T.o $T.s $T.dis
+
+# and fix code at-and-after marker
+       code=`echo "$code" | cut -c$((${marker} + 1))-`
+fi
+echo Code starting with the faulting instruction  > $T.aa
+echo =========================================== >> $T.aa
+code=`echo $code | sed -e 's/ [<(]/ /;s/[>)] / /;s/ /,0x/g; s/[>)]$//'`
+echo -n "      .$type 0x" > $T.s
+echo $code >> $T.s
+disas $T
+cat $T.dis >> $T.aa
+
+# (lines of whole $T.oo) - (lines of $T.aa, i.e. "Code starting") + 3,
+# i.e. the title + the "===..=" line (sed is counting from 1, 0 address is
+# special)
+faultlinenum=$(( $(wc -l $T.oo  | cut -d" " -f1) - \
+                $(wc -l $T.aa  | cut -d" " -f1) + 3))
+
+faultline=`cat $T.dis | head -1 | cut -d":" -f2-`
+faultline=`echo "$faultline" | sed -e 's/\[/\\\[/g; s/\]/\\\]/g'`
+
+cat $T.oo | sed -e "${faultlinenum}s/^\(.*:\)\(.*\)/\1\*\2\t\t<-- trapping instruction/"
+echo
+cat $T.aa
+cleanup