Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru> writes:
On 07.09.2020 17:59, Alex Bennée wrote:
Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru> writes:
On 07.09.2020 15:58, Alex Bennée wrote:
Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru> writes:
From: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
This patch adds hmp/qmp commands replay_seek/replay-seek that proceed
the execution to the specified instruction count.
The command automatically loads nearest snapshot and replays the execution
to find the desired instruction count.
Should there be an initial snapshot created at instruction 0? Using a
separate monitor channel:
Right, you can't go to the prior state, when there is no preceding
snapshot available.
It seems creating an initial snapshot automatically would be more user
Please take a look at 'Snapshotting' section of docs/replay.txt.
Reverse debugging is considered to be run with disk image (overlay)
and rrsnapshot option of icount, which allows creating an initial
VM snapshot.
Given that I'm using the block device purely for VM snapshots I think it
would be useful to document the minimal "no disk" approach - i.e. where
the disk is only used for record/replay.
However I'm still having trouble. I can record the trace with:
./qemu-system-aarch64 -cpu cortex-a53 -display none -serial stdio \
-machine virt -kernel zephyr.elf -net none \
-icount
shift=6,align=off,sleep=off,rr=record,rrfile=record.out,rrsnapshot=rrstart \
-drive file=record.qcow2,if=none,id=rr \
-monitor telnet:127.0.0.1:4444 -S
which shows:
(qemu) info snapshots
info snapshots
List of snapshots present on all disks:
ID TAG VM SIZE DATE VM CLOCK
ICOUNT
-- rrstart 653 KiB 2020-09-07 17:12:42 00:00:00.000
0
but do I need a whole separate overlay in the replay case? I thought
supplying snapshot to the drive would prevent the replay case
overwriting what has been recorded but with:
-icount shift=6,align=off,sleep=off,rr=replay,rrfile=record.out \
-drive file=record.qcow2,if=none,id=rr,snapshot
but I get:
(qemu) info snapshots
info snapshots
There is no snapshot available.
so if I drop the ,snapshot from the line I can at least see the snapshot
but continue doesn't seem to work:
(qemu) info snapshots
info snapshots
List of snapshots present on all disks:
ID TAG VM SIZE DATE VM CLOCK
ICOUNT
-- rrstart 653 KiB 2020-09-07 17:12:42 00:00:00.000
0
(qemu) replay_break 190505
replay_break 190505
(qemu) c
c
(qemu) info replay
info replay
Replaying execution 'record.out': instruction count = 0
(qemu)
If I manually loadvm then we get somewhere but replay_seek breaks:
(qemu) loadvm rrstart
loadvm rrstart
(qemu) info replay
info replay
Replaying execution 'record.out': instruction count = 190505
(qemu) replay_seek 190000
replay_seek 190000
snapshotting is disabled
with a crash:
./qemu-system-aarch64 -cpu cortex-a53 -display none -serial stdio -machine
virt -kernel zephyr.elf -net none -icount
shift=6,align=off,sleep=off,rr=replay,rrfile=record.out
-drive file=record.qcow2,if=none,id=rr -monitor telnet:127.0.0.1:4444 -S