On 29/09/20 13:01, 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
Hi Pavel, I'm still seeing failures in "make check-block": https://gitlab.com/bonzini/qemu/-/jobs/769653852 Paolo > v6 changes: > - removed passing err variable without checking it's value after > v5 changes: > - disabled reverse debugging tests for gitlab-based testing > due to the unidentified timeout problem > v4 changes: > - added VM snapshot creation on gdb connect (suggested by Alex Bennée) > - removed useless calls to error_free > - updated poll interrupt processing > - minor changes > v3 changes: > - rebased to support the new build system > - bumped avocado framework version for using fixed remote gdb client > v2 changes: > - rebased to the latest upstream version > - fixed replaying of the POLL interrupts after the latest debug changes > > --- > > Pavel Dovgaluk (11): > replay: provide an accessor for rr filename > qcow2: 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 > tests/acceptance: add reverse debugging test > > Pavel Dovgalyuk (3): > replay: don't record interrupt poll > migration: introduce icount field for snapshots > replay: create temporary snapshot at debugger connection > > > MAINTAINERS | 2 > accel/tcg/cpu-exec.c | 21 ++ > accel/tcg/translator.c | 1 > block/qapi.c | 18 +- > block/qcow2-snapshot.c | 9 + > block/qcow2.h | 3 > blockdev.c | 10 + > docs/interop/qcow2.txt | 5 > docs/replay.txt | 46 +++++ > exec.c | 8 + > gdbstub.c | 64 ++++++ > hmp-commands-info.hx | 11 + > hmp-commands.hx | 50 +++++ > include/block/snapshot.h | 1 > include/monitor/hmp.h | 4 > include/sysemu/replay.h | 26 +++ > migration/savevm.c | 17 +- > qapi/block-core.json | 11 + > qapi/meson.build | 1 > qapi/misc.json | 18 -- > qapi/qapi-schema.json | 1 > qapi/replay.json | 121 ++++++++++++ > replay/meson.build | 1 > replay/replay-debugging.c | 332 > +++++++++++++++++++++++++++++++++ > replay/replay-events.c | 4 > replay/replay-internal.h | 6 - > replay/replay.c | 22 ++ > softmmu/cpus.c | 19 ++ > stubs/replay.c | 15 + > tests/acceptance/reverse_debugging.py | 208 +++++++++++++++++++++ > tests/qemu-iotests/267.out | 48 ++--- > 31 files changed, 1039 insertions(+), 64 deletions(-) > create mode 100644 qapi/replay.json > create mode 100644 replay/replay-debugging.c > create mode 100644 tests/acceptance/reverse_debugging.py > > -- > Pavel Dovgalyuk >
