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Re: [Xen-devel] domain_crash_sync vs "plain crash"


Despite SCHED_OP, that I've blacklisted, which one came to mind? 

On Mon, May 7, 2018 at 5:13 AM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
On 07/05/2018 08:09, Jan Beulich wrote:
>>>> On 07.05.18 at 03:06, <charles.fg@xxxxxxxxx> wrote:
>> When I'm performing some hypercalls with some "unexpected" parameters
>> (robustness test) sometimes the guest is explicitly  "killed" by xen
>> calling the domain_crash(), but sometimes the guest just crash without any
>> explicit message on dmesg or logs.
>> Are those "plain crashes" an expected behavior by design on Xen or are they
>> some untreated parameter checking or something else?
> A silent crash is never supposed to happen, but you always need to first
> consider whether the crashing component actually has a way to get
> something out to wherever you monitor its logs. That is, without (physical
> or virtual, depending on component) serial console you're often unlikely to
> actually observe any messages connected to the crash.
> If you can track down a _truly_ silent crash to its origin, submitting a patch
> to make it non-silent would be appreciated.

Alternatively, if you are fuzzing the hypercalls, which it sounds like
you are, then you need to ensure that you blacklist operations such as
SCHEDOP_shutdown and SCHEDOP_poll to avoid the fuzzer hitting legitimate
hypercalls which shut down or block for indefinite periods of time.

Charles F.'. Gonçalves
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