Andrew,

My apologies if my logic is flawed or what I am describing is convoluted -
I am a student doing research into Xen and trying my best to grasp what is
going on, also my ASM is subpar. I have read a paper on system call
interception (
https://hal.inria.fr/inria-00431031/PDF/Technical_Report_Syscall_Interception.pdf
) - page 10 describes disabling fast system calls by commenting out some
code in the do_set_trap_table() function and logging the calls along with
other guest info. My concern is that this may be a dated methodology as the
paper was written in 2009 but also that this will only work for x86 and not
x86_64 systems; including possible loss of performance since fast calls
tend to run better on x86 series processor systems. My goal is to identify
when a guest makes a hypercall requesting HYPERVISOR_......grant_table_op(),
 mmu_update(), set_trap_table(), essentially I would love to be able to
say...if trapcode = xxx printk("Hypercall xxx\n") has occurred but I am
unsure what would be a good route to do something like that.

Thanks,
D'Mita

On Fri, Feb 6, 2015 at 10:23 AM, Andrew Cooper <andrew.coop...@citrix.com>
wrote:

>  On 06/02/15 15:17, D'Mita Levy wrote:
>
> Andrew,
>
>  Thanks for your help. I am trying to log the following hypercalls to
> dmesg as they come in:
>
>   -HYPERVISOR_grant_table_op()
>
> - HYPERVISOR_mmu_update()
>
> - HYPERVISOR_set_trap_table()
>
> Are there single handlers for these as well?
>
>
> The hypercall_table in arch/x86/x86_64/entry.S is the function pointer
> dispatch table, and is indexed by hypercall number.
>
> ~Andrew
>



-- 
D'Mita Levy
Cyber Fellow, Applied Research Center
Florida International University
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