| Message ID | 160006358590.31457.16757371597343007847.stgit@pasha-ThinkPad-X280 (mailing list archive) |
|---|---|
| Headers | show |
| Series | Reverse debugging | expand |
On 14/09/20 08:06, 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. I had queued this, it is a very nice patch series. Unfortunately, the tests failed on gitlab: https://gitlab.com/bonzini/qemu/-/jobs/745795080 Paolo
On 20.09.2020 10:58, Paolo Bonzini wrote: > On 14/09/20 08:06, 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. > > I had queued this, it is a very nice patch series. Unfortunately, the > tests failed on gitlab: > > https://gitlab.com/bonzini/qemu/-/jobs/745795080 There is a strange thing in your environment: 15:49:41 INFO | Downloading/preparing boot image 15:49:42 INFO | Running '/builds/bonzini/qemu/build/qemu-img create -f qcow2 -b /builds/bonzini/qemu/avocado-cache/by_location/d2a8d6b607afec50de14560c064f34ffd99836b2/Fedora-Cloud-Base-31-1.9.x86_64.qcow2 /var/tmp/avocado_tj2janfx/avocado_job_ys7ueohj/04-tests_acceptance_boot_linux.py_BootLinuxX8664.test_pc_q35_kvm/Fedora-Cloud-Base-31-1.9.x86_64-d1ac1224.qcow2' It downloads boot image, but there is no such requirement in the test. And all this stuff consumes most of the time for the test. Pavel Dovgalyuk
On 21.09.2020 09:03, Pavel Dovgalyuk wrote: > On 20.09.2020 10:58, Paolo Bonzini wrote: >> On 14/09/20 08:06, 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. >> >> I had queued this, it is a very nice patch series. Unfortunately, the >> tests failed on gitlab: >> >> https://gitlab.com/bonzini/qemu/-/jobs/745795080 > > There is a strange thing in your environment: > > 15:49:41 INFO | Downloading/preparing boot image > 15:49:42 INFO | Running '/builds/bonzini/qemu/build/qemu-img create -f > qcow2 -b > /builds/bonzini/qemu/avocado-cache/by_location/d2a8d6b607afec50de14560c064f34ffd99836b2/Fedora-Cloud-Base-31-1.9.x86_64.qcow2 > /var/tmp/avocado_tj2janfx/avocado_job_ys7ueohj/04-tests_acceptance_boot_linux.py_BootLinuxX8664.test_pc_q35_kvm/Fedora-Cloud-Base-31-1.9.x86_64-d1ac1224.qcow2' > > > > It downloads boot image, but there is no such requirement in the test. > And all this stuff consumes most of the time for the test. Sorry, that was ok. It was the output from the previous test. For reverse debugging there was a timeout on reading from the socket: result = self._socket.recv(REMOTE_MAX_PACKET_SIZE) Do you have any hint how to debug such a failure in this environment? Pavel Dovgalyuk
On 20.09.2020 10:58, Paolo Bonzini wrote: > On 14/09/20 08:06, 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. > > I had queued this, it is a very nice patch series. Unfortunately, the > tests failed on gitlab: > > https://gitlab.com/bonzini/qemu/-/jobs/745795080 There are other tests that were disabled on gitlab for the unknown reason. https://patchwork.kernel.org/patch/11636515/ https://patchwork.kernel.org/patch/11701681/ The latter is related to machine_rx_gdbsim.py Could it be the same avocado/python/etc issue with socket interaction? Pavel Dovgalyuk
On 9/21/20 8:48 AM, Pavel Dovgalyuk wrote: > On 20.09.2020 10:58, Paolo Bonzini wrote: >> On 14/09/20 08:06, 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. >> >> I had queued this, it is a very nice patch series. Unfortunately, the >> tests failed on gitlab: >> >> https://gitlab.com/bonzini/qemu/-/jobs/745795080 > > There are other tests that were disabled on gitlab for the unknown reason. > > https://patchwork.kernel.org/patch/11636515/ Unrelated. > https://patchwork.kernel.org/patch/11701681/ > > The latter is related to machine_rx_gdbsim.py Unrelated, 'gdbsim' is the name of the machine. It is not using the gdbstub/gdb protocol. > Could it be the same avocado/python/etc issue with socket interaction? Yes, likely... The kludge is to simply add (with an explanation if possible): @skipIf(os.getenv('GITLAB_CI'), 'Running on GitLab') > > > 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 The patches are available in the repository: https://github.com/ispras/qemu/tree/rr-200901 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 (4): replay: don't record interrupt poll migration: introduce icount field for snapshots docs: convert replay.txt to rst 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 | 364 ----------------------------- docs/system/index.rst | 1 docs/system/replay.rst | 410 +++++++++++++++++++++++++++++++++ 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 | 334 +++++++++++++++++++++++++++ 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 | 203 ++++++++++++++++ tests/qemu-iotests/267.out | 48 ++-- 33 files changed, 1401 insertions(+), 428 deletions(-) delete mode 100644 docs/replay.txt create mode 100644 docs/system/replay.rst create mode 100644 qapi/replay.json create mode 100644 replay/replay-debugging.c create mode 100644 tests/acceptance/reverse_debugging.py -- Pavel Dovgalyuk