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Re: [Qemu-devel] [PATCH v5 00/24] Fixing record/replay and adding revers
From: |
Ciro Santilli |
Subject: |
Re: [Qemu-devel] [PATCH v5 00/24] Fixing record/replay and adding reverse debugging |
Date: |
Wed, 8 Aug 2018 00:13:27 +0100 |
OK, finally got some time to try it out, I'm using
c42634d8e3428cfa60672c3ba89cabefc720cde9 from rr-180725.
Replay works well as far as I can tell, so I moved to the reverse debugging:
/home/ciro/bak/git/linux-kernel-module-cheat/out/x86_
64/buildroot/build/host-qemu-custom.rr/x86_64-softmmu/qemu-system-x86_64 \
-M pc \
-append 'root=/dev/sda nopat console_msg_format=syslog nokaslr norandmaps
printk.devkmsg=on printk.time=y console=ttyS0 - lkmc_eval_base64="
L3JhbmRfY2hlY2sub3V0Oy9wb3dlcm9mZi5vdXQ7"' \
-kernel '/home/ciro/bak/git/linux-kernel-module-cheat/out/x86_
64/buildroot/build/linux-custom.default/arch/x86/boot/bzImage' \
-m '256M' \
-monitor 'telnet::45454,server,nowait' \
-nographic \
-serial mon:stdio \
-smp '1' \
\
-drive 'file=/home/ciro/bak/git/linux-kernel-module-cheat/out/
x86_64/buildroot/images/rootfs.ext2.qcow2,format=qcow2,if=none,id=img-direct'
\
-drive driver=blkreplay,if=none,image=img-direct,id=img-blkreplay \
-device ide-hd,drive=img-blkreplay \
\
-object filter-replay,id=replay,netdev=net0 \
-device rtl8139,netdev=net0 \
-netdev 'user,hostfwd=tcp::45455-:45455,hostfwd=tcp::45456-:22,id=net0' \
\
-icount 'shift=7,rr=record,rrfile=/home/ciro/bak/git/linux-
kernel-module-cheat/out/x86_64/qemu/0/rrfile' \
and replay with:
-icount 'shift=7,rr=replay,rrfile=/home/ciro/bak/git/linux-
kernel-module-cheat/out/x86_64/qemu/0/rrfile' \
-gdb 'tcp::45457' \
-S \
Then, I do
/home/ciro/bak/git/linux-kernel-module-cheat/out/x86_
64/buildroot/host/usr/bin/x86_64-linux-gdb \
-q \
-ex 'add-auto-load-safe-path /home/ciro/bak/git/linux-kernel-module-cheat' \
-ex 'file vmlinux' \
-ex 'target remote localhost:45457' \
-ex 'break start_kernel' \
-ex continue \
-ex 'lx-symbols ../kernel_module-1.0/' \
Then in GDB:
n
n
n
n
reverse-continue
expecting it to return me to start_kernel, but instead it left me in the
same place that I'm at.
I also tried to manually checkpoint from qemu monitor at the very start,
but it didn't change anything.
bzImage at: https://github.com/cirosantilli/linux-kernel-
module-cheat/releases/download/sha-19f4d00f9b13aa67369e32ec7cd351
8950c6f30e/bzImage and docs at: https://github.com/
cirosantilli/linux-kernel-module-cheat/tree/19f4d00f9b13aa67369e32ec7cd351
8950c6f30e#qemu-record-and-replay
On Wed, Jul 25, 2018 at 1:13 PM, Pavel Dovgalyuk <address@hidden>
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:
> - fixes of record/replay caused by the QEMU core changes
> - 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
> - other record/replay fixes
>
> The patches are available in the repository:
> https://github.com/ispras/qemu/tree/rr-180725
>
> v5 changes:
> - multiple fixes of record/replay bugs appeared after QEMU core update
> - changed reverse debugging to 'since 3.1'
>
> v4 changes:
> - changed 'since 2.13' to 'since 3.0' in json (as suggested by Eric Blake)
>
> v3 changes:
> - Fixed PS/2 bug with save/load vm, which caused failures of the replay.
> - Rebased to the new code base.
> - Minor fixes.
>
> v2 changes:
> - documented reverse debugging
> - fixed start vmstate loading in record mode
> - documented qcow2 changes (as suggested by Eric Blake)
> - made icount SnapshotInfo field optional (as suggested by Eric Blake)
> - renamed qmp commands (as suggested by Eric Blake)
> - minor changes
>
> ---
>
> Pavel Dovgalyuk (24):
> block: implement bdrv_snapshot_goto for blkreplay
> replay: disable default snapshot for record/replay
> replay: update docs for record/replay with block devices
> replay: don't drain/flush bdrv queue while RR is working
> replay: finish record/replay before closing the disks
> qcow2: introduce icount field for snapshots
> migration: introduce icount field for snapshots
> replay: introduce info hmp/qmp command
> replay: introduce breakpoint at the specified step
> replay: implement replay-seek command to proceed to the desired step
> replay: flush events when exiting
> timer: remove replay clock probe in deadline calculation
> replay: refine replay-time module
> translator: fix breakpoint processing
> 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
> replay: allow loading any snapshots before recording
> ps2: prevent changing irq state on save and load
> replay: wake up vCPU when replaying
> replay: replay BH for IDE trim operation
> replay: add BH oneshot event for block layer
> slirp: fix ipv6 timers
>
>
> accel/tcg/translator.c | 9 +
> block/blkreplay.c | 8 +
> block/block-backend.c | 3
> block/io.c | 22 +++
> block/qapi.c | 17 ++-
> block/qcow2-snapshot.c | 9 +
> block/qcow2.h | 2
> blockdev.c | 10 ++
> cpus.c | 50 +++++---
> docs/interop/qcow2.txt | 4 +
> docs/replay.txt | 45 +++++++
> exec.c | 6 +
> gdbstub.c | 50 +++++++-
> hmp-commands-info.hx | 14 ++
> hmp-commands.hx | 30 +++++
> hmp.h | 3
> hw/ide/core.c | 3
> hw/input/ps2.c | 8 +
> include/block/snapshot.h | 1
> include/sysemu/replay.h | 24 ++++
> migration/savevm.c | 15 +-
> qapi/block-core.json | 5 +
> qapi/block.json | 3
> qapi/misc.json | 68 +++++++++++
> replay/Makefile.objs | 3
> replay/replay-debugging.c | 287 ++++++++++++++++++++++++++++++
> +++++++++++++++
> replay/replay-events.c | 30 +++--
> replay/replay-internal.h | 11 +-
> replay/replay-snapshot.c | 17 ++-
> replay/replay-time.c | 27 ++--
> replay/replay.c | 36 +++++-
> slirp/ip6_icmp.c | 6 -
> stubs/replay.c | 16 +++
> util/qemu-timer.c | 11 --
> vl.c | 18 ++-
> 35 files changed, 772 insertions(+), 99 deletions(-)
> create mode 100644 replay/replay-debugging.c
>
> --
> Pavel Dovgalyuk
>
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