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Commit dcecc6c7 authored by Randy Dunlap's avatar Randy Dunlap Committed by Linus Torvalds
Browse files

doc/oops-tracing: add Code: decode info 



Add info that the Code: bytes line contains <xy> or (wxyz) in some
architecture oops reports and what that means.

Add a script by Andi Kleen that reads the Code: line from an Oops report
file and generates assembly code from the hex bytes.

Signed-off-by: default avatarRandy Dunlap <randy.dunlap@oracle.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 213dd266

Documentation/oops-tracing.txt

+14 −0
Original line number Diff line number Diff line
@@ -86,6 +86,20 @@ stuff are the values reported by the Oops - you can just cut-and-paste 
and do a replace of spaces to "\x" - that's what I do, as I'm too lazy 

to write a program to automate this all).



Alternatively, you can use the shell script in scripts/decodecode.

Its usage is:  decodecode < oops.txt



The hex bytes that follow "Code:" may (in some architectures) have a series

of bytes that precede the current instruction pointer as well as bytes at and

following the current instruction pointer.  In some cases, one instruction

byte or word is surrounded by <> or (), as in "<86>" or "(f00d)".  These

<> or () markings indicate the current instruction pointer.  Example from

i386, split into multiple lines for readability:



Code: f9 0f 8d f9 00 00 00 8d 42 0c e8 dd 26 11 c7 a1 60 ea 2b f9 8b 50 08 a1

64 ea 2b f9 8d 34 82 8b 1e 85 db 74 6d 8b 15 60 ea 2b f9 <8b> 43 04 39 42 54

7e 04 40 89 42 54 8b 43 04 3b 05 00 f6 52 c0



Finally, if you want to see where the code comes from, you can do



	cd /usr/src/linux

scripts/decodecode

0 → 100644
+51 −0
Original line number Diff line number Diff line 
#!/bin/sh

# 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



T=`mktemp`

code=



while read i ; do



case "$i" in

*Code:*)

	code=$i

	;;

esac



done



if [ -z "$code" ]; then

	exit

fi



echo $code

code=`echo $code | sed -e 's/.*Code: //'`



marker=`expr index "$code" "\<"`

if [ $marker -eq 0 ]; then

	marker=`expr index "$code" "\("`

fi



if [ $marker -ne 0 ]; then

	beforemark=`echo "$code" | cut -c-$((${marker} - 1))`

	echo -n "	.byte 0x" > $T.s

	echo $beforemark | sed -e 's/ /,0x/g' >> $T.s

	as $AFLAGS -o $T.o $T.s

	objdump -S $T.o

	rm $T.o $T.s



# and fix code at-and-after marker

	code=`echo "$code" | cut -c$((${marker} + 1))-`

fi



code=`echo $code | sed -e 's/ [<(]/ /;s/[>)] / /;s/ /,0x/g'`

echo -n "	.byte 0x" > $T.s

echo $code >> $T.s

as $AFLAGS -o $T.o $T.s

objdump -S $T.o

rm $T.o $T.s