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Subject[PATCH v3] doc/oops-tracing: add Code: decode info
From: Randy Dunlap <randy.dunlap@oracle.com>

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: Randy Dunlap <randy.dunlap@oracle.com>
---
Documentation/oops-tracing.txt | 14 ++++++++++++
scripts/decodecode | 47 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 61 insertions(+)

--- linux-2.6.22-rc5.orig/Documentation/oops-tracing.txt
+++ linux-2.6.22-rc5/Documentation/oops-tracing.txt
@@ -86,6 +86,20 @@ stuff are the values reported by the Oop
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
--- /dev/null
+++ linux-2.6.22-rc5/scripts/decodecode
@@ -0,0 +1,47 @@
+#!/bin/sh
+# Disassemble the Code: line in Linux oopses
+# usage: decodecode < oops.file
+
+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 [ $marker -ne 0 ]; then
+ beforemark=${code:0:$((marker - 1))}
+ echo -n " .byte 0x" > $T.s
+ echo $beforemark | sed -e 's/ /,0x/g' >> $T.s
+ as -o $T.o $T.s
+ objdump -S $T.o
+ rm $T.o $T.s
+
+# and fix code at-and-after marker
+ code=${code:$marker}
+fi
+
+code=`echo $code | sed -e 's/ [<(]/ /;s/[>)] / /;s/ /,0x/g'`
+echo -n " .byte 0x" > $T.s
+echo $code >> $T.s
+as -o $T.o $T.s
+objdump -S $T.o
+rm $T.o $T.s
-
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