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Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging
From: |
Alex Bennée |
Subject: |
Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging |
Date: |
Tue, 05 Jun 2018 09:47:58 +0100 |
User-agent: |
mu4e 1.1.0; emacs 26.1.50 |
Pavel Dovgalyuk <address@hidden> writes:
>> From: Alex Bennée [mailto:address@hidden
>> Pavel Dovgalyuk <address@hidden> writes:
>>
>> > Ping?
>>
>> I started having a look but I ran into this straight away. First I
>> recorded a boot of the kernel:
>>
>> ./aarch64-softmmu/qemu-system-aarch64 -machine virt,graphics=on,gic-
>> version=3,virtualization=on -cpu cortex-a53 --serial mon:stdio -display none
>> -kernel
>> ../images/aarch64-current-linux-initrd-guest.img -icount
>> shift=7,rr=record,rrfile=replay.bin
>>
>> Then played back:
>>
>> ./aarch64-softmmu/qemu-system-aarch64 -machine virt,graphics=on,gic-
>> version=3,virtualization=on -cpu cortex-a53 --serial mon:stdio -display none
>> -kernel
>> ../images/aarch64-current-linux-initrd-guest.img -icount
>> shift=7,rr=replay,rrfile=replay.bin -
>> s -S
>
> This looks ok, but...
>
>> And did the following on gdb:
>>
>> (gdb) i
>> 0x0000000040000004 in ?? ()
>> => 0x40000004: mov x1, xzr
>> 0x40000008: mov x2, xzr
>> 0x4000000c: mov x3, xzr
>> (gdb)
>> 0x0000000040000008 in ?? ()
>> => 0x40000008: mov x2, xzr
>> 0x4000000c: mov x3, xzr
>> 0x40000010: ldr x4, 0x40000020
>> (gdb)
>> 0x000000004000000c in ?? ()
>> => 0x4000000c: mov x3, xzr
>> 0x40000010: ldr x4, 0x40000020
>> 0x40000014: br x4
>> (gdb)
>> 0x0000000040000010 in ?? ()
>> => 0x40000010: ldr x4, 0x40000020
>> 0x40000014: br x4
>> 0x40000018: .inst 0x44000000 ; undefined
>> (gdb)
>> 0x0000000040000014 in ?? ()
>> => 0x40000014: br x4
>> 0x40000018: .inst 0x44000000 ; undefined
>> 0x4000001c: .inst 0x00000000 ; undefined
>> (gdb) p/x $x4
>> $1 = 0x40080000
>> (gdb) reverse-stepi
>> warning: Remote failure reply: E14
>>
>> Surely this is the simple case and doesn't require any snapshots for
>> block devices as there are none. Am I missing something?
>
> Reverse debugging requires the snapshotting. QEMU can't revert the VM state
> without the snapshots.
> You can try adding an empty qcow2 image to allow snapshotting there.
I suspect a recent patch has broken locking again:
Starting program:
/home/alex/lsrc/qemu/qemu.git/aarch64-softmmu/qemu-system-aarch64 -machine
virt,graphics=on,gic-version=3,virtualization=on -cpu cortex-a53 --serial
mon:stdio -display none -kernel
../images/aarch64-current-linux-initrd-guest.img -icount
shift=7,rr=replay,rrfile=replay.bin,rrsnapshot=debug -drive
file=rr.qcow2,if=none,snapshot,id=rr -s -S
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffd8536700 (LWP 32452)]
[New Thread 0x7fffd5bb3700 (LWP 32453)]
[New Thread 0x7fffd4eab700 (LWP 32454)]
**
ERROR:replay/replay-time.c:49:replay_read_clock: assertion failed: (replay_file
&& replay_mutex_locked())
Once I have the linux-user TCG tests merged I'm planning on focusing on
the system emulation tests and we should be able to add some
record/replay tests to defend the behaviour.
--
Alex Bennée
- Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging, Pavel Dovgalyuk, 2018/06/04
- Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging, Alex Bennée, 2018/06/04
- Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging, Pavel Dovgalyuk, 2018/06/05
- Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging, Alex Bennée, 2018/06/05
- Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging,
Alex Bennée <=
- Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging, Pavel Dovgalyuk, 2018/06/05
- Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging, Alex Bennée, 2018/06/05
- Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging, Pavel Dovgalyuk, 2018/06/06
- Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging, Pavel Dovgalyuk, 2018/06/25
- Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging, Alex Bennée, 2018/06/27