|
Please do not top post.
On 12/02/15 18:19, D'Mita Levy wrote:
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(),
Âmmu_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.
For something written in 2009, that has aged surprisingly well,
given that it refers to exact snippets of code. It will however
fail to catch any system call made using sysenter or syscall.
However, intercepting system calls in a PV guest is completely
different to intercepting hypercalls, and the described method will
not help you in this case.
My original point still stands. You cannot put a printk in
hypercall handlers such as mmu_update and grant_table_op. Xen will
be completely crippled under the spew of all the logging.
Have you considered using xentrace?
~Andrew
|
