Hi,
> Yes I missed that PatchGuard would eventually check those shadow pages anyway.
> I was already happy to see that my breakpoints were working, and I proceeded
> to the tests
> hoping to have a quick reproduction of the bug.
>
> I implemented a basic mem_access event on the restricting to --X only on the
> original GFN being remapped,
> and switching to hostp2m and singlestepping to escape PatchGuard.
>
> It works, but I end up in a situation where Xen fails at some point, because
> at ~90 tests, it cannot populate the ring anymore:
> INFO:root:==== test 92 ====
> INFO:root:starting drakvuf
> INFO:root:starting Ansible
> INIT
> xen_init_interface
> xc_interface_open
> create logger
> allocating libxc context
> init ring page
> xc: error: Failed to populate ring pfn
> (16 = Device or resource busy): Internal error
> fail to enable monitoring: Device or resource busy
> fail to init xen interface
> CLOSE
> Fail to init vmi
>
> (I updated the Gist:
> https://gist.github.com/mtarral/d99ce5524cfcfb5290eaa05702c3e8e7#file-xen-drakvuf-c)
> What do you think happened ?
> I have a call to xc_domain_setmaxmem with ~0, so it shouldn't happen ?
> https://gist.github.com/mtarral/d99ce5524cfcfb5290eaa05702c3e8e7#file-xen-drakvuf-c-L598
I moved the call to xc_domain_setmaxmem BEFORE xc_monitor_enable.
Which works.
I'm continuing my testing to see if I can reproduce the bug.
Mathieu
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