Re: [Qemu-devel] virsh dump (qemu guest memory dump?): KASLR enabled linux guest support

[Wen Congyang]

On 11/09/2016 11:17 AM, Dave Young wrote:
> Drop qiaonuohan, seems the mail address is wrong..
> 
> On 11/09/16 at 11:01am, Dave Young wrote:
>> Hi,
>>
>> Latest linux kernel enabled kaslr to randomiz phys/virt memory
>> addresses, we had some effort to support kexec/kdump so that crash
>> utility can still works in case crashed kernel has kaslr enabled.
>>
>> But according to Dave Anderson virsh dump does not work, quoted messages
>> from Dave below:
>>
>> """
>> with virsh dump, there's no way of even knowing that KASLR
>> has randomized the kernel __START_KERNEL_map region, because there is no
>> virtual address information -- e.g., like "SYMBOL(_stext)" in the kdump
>> vmcoreinfo data to compare against the vmlinux file symbol value.
>> Unless virsh dump can export some basic virtual memory data, which
>> they say it can't, I don't see how KASLR can ever be supported.
>> """
>>
>> I assume virsh dump is using qemu guest memory dump facility so it
>> should be first addressed in qemu. Thus post this query to qemu devel
>> list. If this is not correct please let me know.

IIRC, 'virsh dump --memory-only' uses dump-guest-memory, and 'virsh dump'
uses migration to dump.

I think I should study kaslr first...

Thanks
Wen Congyang

>>
>> Could you qemu dump people make it work? Or we can not support virt dump
>> as long as KASLR being enabled. Latest Fedora kernel has enabled it in 
>> x86_64.
>>
>> Thanks
>> Dave
> 
> 
>