RE: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB

[Pavel Dovgalyuk]

Ping.



Pavel Dovgalyuk

> -----Original Message-----
> From: Pavel Dovgalyuk [mailto:address@hidden]
> Sent: Monday, December 23, 2019 12:46 PM
> To: address@hidden
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> Subject: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB
> 
> 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
> 
> The patches are available in the repository:
> https://github.com/ispras/qemu/tree/rr-191223
> 
> ---
> 
> Pavel Dovgaluk (11):
>       replay: provide an accessor for rr filename
>       qcow2: introduce icount field for snapshots
>       migration: introduce icount field for snapshots
>       qapi: introduce replay.json for record/replay-related stuff
>       replay: introduce info hmp/qmp command
>       replay: introduce breakpoint at the specified step
>       replay: implement replay-seek command
>       replay: flush rr queue before loading the vmstate
>       gdbstub: add reverse step support in replay mode
>       gdbstub: add reverse continue support in replay mode
>       replay: describe reverse debugging in docs/replay.txt
> 
> 
>  MAINTAINERS               |    1
>  accel/tcg/translator.c    |    1
>  block/qapi.c              |   18 ++
>  block/qcow2-snapshot.c    |    9 +
>  block/qcow2.h             |    3
>  blockdev.c                |   10 +
>  cpus.c                    |   19 ++-
>  docs/interop/qcow2.txt    |    4 +
>  docs/replay.txt           |   33 +++++
>  exec.c                    |    8 +
>  gdbstub.c                 |   64 ++++++++-
>  hmp-commands-info.hx      |   14 ++
>  hmp-commands.hx           |   53 +++++++
>  include/block/snapshot.h  |    1
>  include/monitor/hmp.h     |    4 +
>  include/sysemu/replay.h   |   24 +++
>  migration/savevm.c        |   17 ++
>  qapi/Makefile.objs        |    2
>  qapi/block-core.json      |    8 +
>  qapi/block.json           |    3
>  qapi/misc.json            |   18 --
>  qapi/qapi-schema.json     |    1
>  qapi/replay.json          |  121 +++++++++++++++++
>  replay/Makefile.objs      |    1
>  replay/replay-debugging.c |  325 
> +++++++++++++++++++++++++++++++++++++++++++++
>  replay/replay-internal.h  |    6 +
>  replay/replay.c           |   22 +++
>  stubs/replay.c            |   10 +
>  28 files changed, 761 insertions(+), 39 deletions(-)
>  create mode 100644 qapi/replay.json
>  create mode 100644 replay/replay-debugging.c
> 
> --
> Pavel Dovgalyuk