From: Borislav Petkov <bp@xxxxxxx> Subject: scripts/decodecode: add the capability to supply the program counter 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 Link: https://lkml.kernel.org/r/20200930111416.GF6810@xxxxxxx Link: https://lkml.kernel.org/r/20200929113238.GC21110@xxxxxxx Signed-off-by: Borislav Petkov <bp@xxxxxxx> Cc: Marc Zyngier <maz@xxxxxxxxxxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Cc: Rabin Vincent <rabin@xxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- scripts/decodecode | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-) --- a/scripts/decodecode~scripts-decodecode-add-the-capability-to-supply-the-program-counter +++ a/scripts/decodecode @@ -6,6 +6,7 @@ # 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 $T.dis @@ -67,15 +68,19 @@ if [ -z "$ARCH" ]; then esac fi +# Params: (tmp_file, pc_sub) disas() { - ${CROSS_COMPILE}as $AFLAGS -o $1.o $1.s > /dev/null 2>&1 + 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 $1.o + ${CROSS_COMPILE}strip $t.o fi if [ "$ARCH" = "arm64" ]; then @@ -83,11 +88,18 @@ disas() { type=inst fi - ${CROSS_COMPILE}strip $1.o + ${CROSS_COMPILE}strip $t.o fi - ${CROSS_COMPILE}objdump $OBJDUMPFLAGS -S $1.o | \ - grep -v "/tmp\|Disassembly\|\.text\|^$" > $1.dis 2>&1 + 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" "\<"` @@ -95,14 +107,17 @@ 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 + disas $T $pc_sub cat $T.dis >> $T.oo rm -f $T.o $T.s $T.dis @@ -114,7 +129,7 @@ echo =================================== code=`echo $code | sed -e 's/ [<(]/ /;s/[>)] / /;s/ /,0x/g; s/[>)]$//'` echo -n " .$type 0x" > $T.s echo $code >> $T.s -disas $T +disas $T 0 cat $T.dis >> $T.aa # (lines of whole $T.oo) - (lines of $T.aa, i.e. "Code starting") + 3, _
