Re: [flickertcb-devel] Crash on "reload CR3 with the kernel's original value"

[Alexander N. <ale...@gm...>]

I'm very sorry for spamming you, but I wanted to add:

When I switched from using the latest flicker code from your git repositry
and instead used version 0.7, I got in a state of kernel panic after a few
minutes

Kernel panic - not syncing: attempted to kill init! exitcode=0x00000007


> drm_kms_helper: panic occured, switching back to text console
>

This was the only thing showing on a black screen. Also go.sh was stuck
trying and failing to output anything from dmesg just before the kernel
panic occured.

I don't know if this happened due to me switching from one flicker version
to another or if it was just random chance, but I thought you should now,
if it means anything to you?

As always, I'm very grateful for any assistance you may send my way.

//Alexander Nilsson


2014-03-15 21:56 GMT+01:00 Alexander Nilsson <ale...@gm...>:

> Hi again!
>
> It appears that the OS now resumes on every try (I can see "top" updating
> in the background) but somehow mouse movements and keyboard input it does
> not seem to register.
>
> So I modified go.sh and added some output from dmesg right after flicker
> session has finished, I got the following output (JPEG):
> https://drive.google.com/file/d/0B5DRLAjJvOKtSXh1LXd1Vm9tV2xFdlJ3RkpYdTJoR0lNLWg4/edit?usp=sharing
>
> I tried to pipe dmesg to a file but that gives me "Input/Output error"
> which as you can see is the same message I get when the script tries to
> enable the other CPUs again.
>
> Oh.. and after a while I get a message that my wifi connection has been
> lost.
>
> Can it be that interrupts are not enabled again after OS resume? Or is it
> something else?
>
> //Alexander Nilsson
>
>
> 2014-03-15 20:31 GMT+01:00 Alexander Nilsson <ale...@gm...>:
>
> Okay so this is interesting, I've installed a new non-pae kernel and now
>> when I try flicker 50% of the time I get a computer freeze (infinite) and
>> the other time I get a short freeze (~1 s) followed by the next echo in
>> go.sh ("Retrieving outputs from Flicker session:") and _then_ infinite
>> freeze! But here's the really interesting part: the marker in my terminal
>> continue to blink after the first 1 s freeze, so the OS appears to be
>> resumed but it does not execute any new commands.
>>
>> I also tried to execute the pal by modifying go.sh to
>>
>> echo -n G > $SYSFSPATH/control ; echo 1 >
>>> /sys/devices/system/cpu/cpu2/online
>>>
>>
>> thinking that maybe the first CPU has locked somehow, but to no avail.
>>
>> I will continue investigating, and perhaps I'll be able to describe the
>> symptoms a bit clearer then, but is this something you have encountered
>> before?
>>
>> //Alexander Nilsson
>>
>>
>> 2014-03-15 17:50 GMT+01:00 Justin King-Lacroix <
>> jus...@cs...>:
>>
>> On AMT: As far as I knew, AMT only worked over the built-in ethernet
>>> port; if the machine you're working on doesn't have one, I see your
>>> predicament. (I don't *think* AMT works over wireless... unless Intel has
>>> written that feature into recent-ish versions of the platform.)
>>>
>>> On the kernel: yeah, I'm pretty sure PAE kernels have 64-bit wide CR3
>>> and paging data structure, so that sounds like a potential source of
>>> problems. (It makes sense for the *buntu variants to all switch to PAE
>>> kernels; a few features are only available in that mode, most importantly
>>> the NX bit.)
>>>
>>> J
>>>
>>>
>>>
>>>
>>> On 15 March 2014 16:41, Alexander Nilsson <ale...@gm...> wrote:
>>>
>>>> Thank you for your quick reply.
>>>>
>>>> Yes it does have AMT but I have not yet managed to get a connection, I
>>>> think it has something to do with the fact that I only have a wifi network
>>>> card (plus a usb ethernet card), I haven't been able to find out if it is
>>>> related or I'm just doing it wrong, I will continue my investigation.
>>>>
>>>> Your reply got me thinking and I investigated further: PAE appears to
>>>> be enabled in my kernel, despite the fact that I specifically installed
>>>> xubuntu in order skip that feature (apparently there was a policy change
>>>> that I was unaware of regarding kernel features in ubuntu versions later
>>>> than 12.10).
>>>>
>>>> I will change kernel and then I will let you now if it's working or not
>>>> after that!
>>>>
>>>> Thanks!
>>>>
>>>> //Alexander Nilsson
>>>>
>>>>
>>>> 2014-03-15 16:08 GMT+01:00 Justin King-Lacroix <
>>>> jus...@cs...>:
>>>>
>>>> "... my machine does not have a serial port...": Does your machine
>>>>> support any remote management spec, like Intel AMT? If so, you can fiddle
>>>>> with the serial port code in Flicker to use that.
>>>>>
>>>>> "... my machine reboots on the following line...":
>>>>> (This following is a total guess, knowing nothing about your
>>>>> environment...)
>>>>> Are you using a 32-bit or 64-bit OS/kernel? The reason is:
>>>>> From memory, CR3 is the page directory pointer. That line looks like
>>>>> it restores 32 bits of CR3; if you're in 64-bit mode, that means the top 64
>>>>> bits are zero, which will result in a triple-fault when attempting to do
>>>>> anything in kernel memory (like, say, execute). A triple-fault causes a CPU
>>>>> reset.
>>>>>
>>>>> </$0.02>
>>>>>
>>>>> J
>>>>>
>>>>>
>>>>>
>>>>>  On 15 March 2014 13:55, Alexander Nilsson <ale...@gm...>wrote:
>>>>>
>>>>>>  Hi once again!
>>>>>>
>>>>>> I'm sorry for spamming you but maybe you know how to investigate the
>>>>>> following problem?
>>>>>>
>>>>>> Whenever I start a PAL my machine reboots. Since my machine does not
>>>>>> have a serial port the only tool I have available for debugging is to put
>>>>>> an infinite loop in the code to see if the computer hangs or reboots.
>>>>>>
>>>>>> By using this approach I now know that my machine reboots on the
>>>>>> following line (in bold) in asm.S (about line 630 and forward):
>>>>>>
>>>>>>     /* reload CR3 with the kernel's original value */
>>>>>>>     movl %esi, %ebx /* start addr of struct cpu_state */
>>>>>>>     movl CPU_STATE_OFFSET_CR3(%ebx), %eax
>>>>>>>     *movl  %eax, %cr3* ; <----------- reboots here
>>>>>>>     SayAsm // print something without touching stack or data
>>>>>>>
>>>>>>
>>>>>> Unfortunately I do not have the skills to figure out what it is
>>>>>> exactly that goes wrong and I was hoping that someone here might know how
>>>>>> to debug this further?
>>>>>>
>>>>>> Thank you for any and all assistance!
>>>>>>
>>>>>> //Alexander Nilsson
>>>>>>
>>>>>>
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>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>