Hi, Ciro! I found several issues in your command lines.
Ciro Santilli писал 2018-08-08 02:13:
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'
You'll probably need an overlay, it you want this file to be unchanged by VM.
Can you also provide this file for testing? I found only bzImage.
\ -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'
You need to specify rrsnapshot=<name> option for creating the initial VM snapshot. This option creates snapshot at record and loads it at replay. GDB can also use this snapshot for reverse execution.
\ 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.
Right, because there were no checkpoints. The initial one must be created at recording phase.
Pavel Dovgalyuk
