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 <pavel.dovga...@ispras.ru> 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 >
