Re: [PATCH v7 00/14] Reverse debugging

[Paolo Bonzini]

On 03/10/20 19:12, Pavel Dovgalyuk wrote:
> GDB remote protocol supports reverse debugging of the targets.
> It includes 'reverse step' and 'reverse continue' operations.
> The first one finds the previous step of the execution,
> and the second one is intended to stop at the last breakpoint that
> would happen when the program is executed normally.
> 
> Reverse debugging is possible in the replay mode, when at least
> one snapshot was created at the record or replay phase.
> QEMU can use these snapshots for travelling back in time with GDB.
> 
> Running the execution in replay mode allows using GDB reverse debugging
> commands:
>  - reverse-stepi (or rsi): Steps one instruction to the past.
>    QEMU loads on of the prior snapshots and proceeds to the desired
>    instruction forward. When that step is reaches, execution stops.
>  - reverse-continue (or rc): Runs execution "backwards".
>    QEMU tries to find breakpoint or watchpoint by loaded prior snapshot
>    and replaying the execution. Then QEMU loads snapshots again and
>    replays to the latest breakpoint. When there are no breakpoints in
>    the examined section of the execution, QEMU finds one more snapshot
>    and tries again. After the first snapshot is processed, execution
>    stops at this snapshot.
> 
> The set of patches include the following modifications:
>  - gdbstub update for reverse debugging support
>  - functions that automatically perform reverse step and reverse
>    continue operations
>  - hmp/qmp commands for manipulating the replay process
>  - improvement of the snapshotting for saving the execution step
>    in the snapshot parameters
>  - avocado-based acceptance tests for reverse debugging
> 
> The patches are available in the repository:
> https://github.com/ispras/qemu/tree/rr-200901
> 
> v7 changes:
>  - updated snapshot info output format
>  - fixed qcow2 snapshot-related tests

Sorry, I'm still seeing a failure

timeout 15  /home/travis/build/bonzini/qemu/build/qemu-system-aarch64 -monitor 
none -display none -chardev file,path=memory-replay.out,id=output -icount 
shift=5,rr=replay,rrfile=record.bin  -M virt -cpu max -display none 
-semihosting-config enable=on,target=native,chardev=output -kernel memory

qemu-system-aarch64: terminating on signal 15 from pid 38312 (timeout)

https://travis-ci.com/gitlab/bonzini/qemu/jobs/395029273

Paolo