
So that comparing with objdump output from vmlinux can ease pinpointing where the trapping instruction actually is. An example is better than a thousand words: $ PC=0xffffffff8329a927 ./scripts/decodecode < ~/tmp/syz/gfs2.splat [ 477.379104][T23917] Code: 48 83 ec 28 48 89 3c 24 48 89 54 24 08 e8 c1 b4 4a fe 48 8d bb 00 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 97 05 00 00 48 8b 9b 00 01 00 00 48 85 db 0f 84 All code ======== ffffffff8329a8fd: 48 83 ec 28 sub $0x28,%rsp ffffffff8329a901: 48 89 3c 24 mov %rdi,(%rsp) ffffffff8329a905: 48 89 54 24 08 mov %rdx,0x8(%rsp) ffffffff8329a90a: e8 c1 b4 4a fe callq 0xffffffff81745dd0 ffffffff8329a90f: 48 8d bb 00 01 00 00 lea 0x100(%rbx),%rdi ffffffff8329a916: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax ffffffff8329a91d: fc ff df ffffffff8329a920: 48 89 fa mov %rdi,%rdx ffffffff8329a923: 48 c1 ea 03 shr $0x3,%rdx ffffffff8329a927:* 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction ffffffff8329a92b: 0f 85 97 05 00 00 jne 0xffffffff8329aec8 ffffffff8329a931: 48 8b 9b 00 01 00 00 mov 0x100(%rbx),%rbx ffffffff8329a938: 48 85 db test %rbx,%rbx ffffffff8329a93b: 0f .byte 0xf ffffffff8329a93c: 84 .byte 0x84 Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Marc Zyngier <maz@misterjones.org> Cc: Will Deacon <will@kernel.org> Cc: Rabin Vincent <rabin@rab.in> Link: https://lkml.kernel.org/r/20200930111416.GF6810@zn.tnic Link: https://lkml.kernel.org/r/20200929113238.GC21110@zn.tnic Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2.9 KiB
Executable File
#!/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
PC=hex - the PC (program counter) the oops points to
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 $width in
- type=byte ;;
- type=2byte ;;
- type=4byte ;; esac
if [ -z "$ARCH" ]; then
case uname -m
in
aarch64*) ARCH=arm64 ;;
arm*) ARCH=arm ;;
esac
fi
Params: (tmp_file, pc_sub)
disas() { t=$1 pc_sub=$2
${CROSS_COMPILE}as $AFLAGS -o $t.o $t.s > /dev/null 2>&1
if [ "$ARCH" = "arm" ]; then
if [ $width -eq 2 ]; then
OBJDUMPFLAGS="-M force-thumb"
fi
${CROSS_COMPILE}strip $t.o
fi
if [ "$ARCH" = "arm64" ]; then
if [ $width -eq 4 ]; then
type=inst
fi
${CROSS_COMPILE}strip $t.o
fi
if [ $pc_sub -ne 0 ]; then
if [ $PC ]; then
adj_vma=$(( $PC - $pc_sub ))
OBJDUMPFLAGS="$OBJDUMPFLAGS --adjust-vma=$adj_vma"
fi
fi
${CROSS_COMPILE}objdump $OBJDUMPFLAGS -S $t.o | \
grep -v "/tmp\|Disassembly\|\.text\|^$" > $t.dis 2>&1
}
marker=expr index "$code" "\<"
if [ $marker -eq 0 ]; then
marker=expr index "$code" "\("
fi
touch $T.oo
if [ $marker -ne 0 ]; then
# 2 opcode bytes and a single space
pc_sub=$(( $marker / 3 ))
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 $pc_sub
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 0
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