| Message ID | 159316678008.10508.6615172353109944370.stgit@pasha-ThinkPad-X280 (mailing list archive) |
|---|---|
| Headers | show |
| Series | Reverse debugging | expand |
Ping. On 26.06.2020 13:19, 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 > > Acceptance tests intended to use the version of avocado framework, that > will be released after 25.06.20, because it includes significant > fixes of the remote GDB protocol. > > The patches are available in the repository: > https://github.com/ispras/qemu/tree/rr-200626 > > --- > > Pavel Dovgaluk (13): > replay: provide an accessor for rr filename > qcow2: introduce icount field for snapshots > migration: introduce icount field for snapshots > iotests: update snapshot test for new output format > 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 > tests/acceptance: add reverse debugging test > > > 0 files changed > > -- > Pavel Dovgalyuk >
Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru> writes:
> Ping.
I started going through this and then ran into some merge conflicts. Are
all the pre-requisite patches now merged via Paolo's tree?
On 06.07.2020 22:55, Alex Bennée wrote: > > Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru> writes: > >> Ping. > > I started going through this and then ran into some merge conflicts. Are > all the pre-requisite patches now merged via Paolo's tree? > Yes, everything is merged. I pulled the latest master minute ago and got no conflicts with the patches. Pavel Dovgalyuk
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 Acceptance tests intended to use the version of avocado framework, that will be released after 25.06.20, because it includes significant fixes of the remote GDB protocol. The patches are available in the repository: https://github.com/ispras/qemu/tree/rr-200626 --- Pavel Dovgaluk (13): replay: provide an accessor for rr filename qcow2: introduce icount field for snapshots migration: introduce icount field for snapshots iotests: update snapshot test for new output format 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 tests/acceptance: add reverse debugging test 0 files changed -- Pavel Dovgalyuk