[PATCH v2] scripts: add ARM support to decodecode

[Rabin Vincent]

This patch adds support for decoding ARM oopses to scripts/decodecode.
The following things are handled:

 - ARCH and CROSS_COMPILE environment variables are respected.

 - The Code: in x86 oopses is in bytes, while it is in either words (4
   bytes) or halfwords for ARM.

 - Some versions of ARM objdump refuse to disassemble instructions
   generated by literal constants (".word 0x...").  The workaround is to
   strip the object file first.

 - The faulting instruction is marked (liked so) in ARM, but <like so>
   in x86.

 - ARM mnemonics may include characters such as [] which need to be
   escaped before being passed to sed for the "<- trapping instruction"
   substitution.

Signed-off-by: Rabin Vincent <rabin at rab.in>
---
v2: condensed some sed and grep expressions

 scripts/decodecode |   48 +++++++++++++++++++++++++++++++++++-------------
 1 files changed, 35 insertions(+), 13 deletions(-)

diff --git a/scripts/decodecode b/scripts/decodecode
index 4b00647..8b30cc3 100755
--- a/scripts/decodecode
+++ b/scripts/decodecode
@@ -7,7 +7,7 @@
 # AFLAGS=--32 decodecode < 386.oops
 
 cleanup() {
-	rm -f $T $T.s $T.o $T.oo $T.aa  $T.aaa
+	rm -f $T $T.s $T.o $T.oo $T.aa $T.dis
 	exit 1
 }
 
@@ -39,6 +39,29 @@ 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 $1.s &> /dev/null
+
+	if [ "$ARCH" == "arm" ]; then
+		if [ $width == 2 ]; then
+			OBJDUMPFLAGS="-M force-thumb"
+		fi
+
+		${CROSS_COMPILE}strip $1.o
+	fi
+
+	${CROSS_COMPILE}objdump $OBJDUMPFLAGS -S $1.o | \
+		grep -v "/tmp\|Disassembly\|\.text\|^$" &> $1.dis
+}
+
 marker=`expr index "$code" "\<"`
 if [ $marker -eq 0 ]; then
 	marker=`expr index "$code" "\("`
@@ -49,26 +72,25 @@ if [ $marker -ne 0 ]; then
 	echo All code >> $T.oo
 	echo ======== >> $T.oo
 	beforemark=`echo "$code"`
-	echo -n "	.byte 0x" > $T.s
-	echo $beforemark | sed -e 's/ /,0x/g' | sed -e 's/<//g' | sed -e 's/>//g' >> $T.s
-	as $AFLAGS -o $T.o $T.s &> /dev/null
-	objdump -S $T.o | grep -v "/tmp" | grep -v "Disassembly" | grep -v "\.text" | grep -v "^$" &> $T.ooo
-	cat $T.ooo >> $T.oo
-	rm -f $T.o $T.s  $T.ooo
+	echo -n "	.$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'`
-echo -n "	.byte 0x" > $T.s
+code=`echo $code | sed -e 's/ [<(]/ /;s/[>)] / /;s/ /,0x/g; s/[>)]$//'`
+echo -n "	.$type 0x" > $T.s
 echo $code >> $T.s
-as $AFLAGS -o $T.o $T.s &> /dev/null
-objdump -S $T.o | grep -v "Disassembly" | grep -v "/tmp" | grep -v "\.text" | grep -v "^$" &> $T.aaa
-cat $T.aaa >> $T.aa
+disas $T
+cat $T.dis >> $T.aa
 
-faultline=`cat $T.aaa | head -1 | cut -d":" -f2`
+faultline=`cat $T.dis | head -1 | cut -d":" -f2`
+faultline=`echo "$faultline" | sed -e 's/\[/\\\[/g; s/\]/\\\]/g'`
 
 cat $T.oo | sed -e "s/\($faultline\)/\*\1     <-- trapping instruction/g"
 echo
-- 
1.6.5