linux-hardened/scripts/decodecode
Borislav Petkov 18ff44b189 scripts/decodecode: make faulting insn ptr more robust
It can accidentally happen that the faulting insn (the exact instruction
bytes) is repeated a little further on in the trace.  This causes that
same instruction to be tagged twice, see example below.

What we want to do, however, is to track back from the end of the whole
disassembly so many lines as the slice which starts with the faulting
instruction is long.  This leads us to the actual faulting instruction
and *then* we tag it.

While we're at it, we can drop the sed "g" flag because we address only
this one line.

Also, if we point to an instruction which changes decoding depending on
the slice being objdumped, like a Jcc insn, for example, we do not even
tag it as a faulting instruction because the instruction decode changes
in the second slice but we use that second format as a regex on the
fsrst disassembled buffer and more often than not that instruction
doesn't match.

Again, simply tag the line which is deduced from the original "<>"
marking we've received from the kernel.

This also solves the pathologic issue of multiple tagging like this:

  29:*  0f 0b                   ud2         <-- trapping instruction
  2b:*  0f 0b                   ud2         <-- trapping instruction
  2d:*  0f 0b                   ud2         <-- trapping instruction

Double tagging example:

Code: 34 dd 40 30 ad 81 48 c7 c0 80 f6 00 00 48 8b 3c 30 48 01 c6 b8 ff ff ff ff 48 8d 57 f0 48 39 f7 74 2f 49 8b 4c 24 08 48 8b 47 f0 <48> 39 48 08 75 0e eb 2a 66 90 48 8b 40 f0 48 39 48 08 74 1e 48
All code
========
   0:   34 dd                   xor    $0xdd,%al
   2:   40 30 ad 81 48 c7 c0    xor    %bpl,-0x3f38b77f(%rbp)
   9:   80 f6 00                xor    $0x0,%dh
   c:   00 48 8b                add    %cl,-0x75(%rax)
   f:   3c 30                   cmp    $0x30,%al
  11:   48 01 c6                add    %rax,%rsi
  14:   b8 ff ff ff ff          mov    $0xffffffff,%eax
  19:   48 8d 57 f0             lea    -0x10(%rdi),%rdx
  1d:   48 39 f7                cmp    %rsi,%rdi
  20:   74 2f                   je     0x51
  22:   49 8b 4c 24 08          mov    0x8(%r12),%rcx
  27:   48 8b 47 f0             mov    -0x10(%rdi),%rax
  2b:*  48 39 48 08             cmp    %rcx,0x8(%rax)     <-- trapping instruction
  2f:   75 0e                   jne    0x3f
  31:   eb 2a                   jmp    0x5d
  33:   66 90                   xchg   %ax,%ax
  35:   48 8b 40 f0             mov    -0x10(%rax),%rax
  39:*  48 39 48 08             cmp    %rcx,0x8(%rax)     <-- trapping instruction
  3d:   74 1e                   je     0x5d
  3f:   48                      rex.W

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-04-29 15:54:27 -07:00

104 lines
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Executable file

#!/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
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=
while read i ; do
case "$i" in
*Code:*)
code=$i
;;
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
${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