Re: [Fedora-xen] [Xen-devel] How to log system calls from a PV DomU under Xen
ranjith krishnan <ranjithkrishnan1(a)gmail.com> wrote:
Bumping up.
Can somebody give me some pointers. Would help me a lot.
Thanks,
Ranjith
On Tue, Jul 16, 2013 at 1:34 AM, ranjith krishnan <
ranjithkrishnan1(a)gmail.com> wrote:
> Hello,
>
> I was posting a couple weeks back here, asking questions about
getting
> DomUs working in Xen when installing Xen from source.
>
> Well, I have managed to get things working. Currently my setup is
like
> this now.
> Xen 4.2.2, installed from source,
> Fedora 18 Dom0 x86_64, Debian 6 PV DomU x86_64, and Ubuntu 12.04 HVM
DomU
> x86_64.
> My processor has Intel VT-X enabled.
>
> I used xl/xm to create DomUs. I was unable to get virt-manager
working to
> create guests.
> I faced a similar problem with Xen 4.1 and Fedora 17 earlier.
>
> As the next step in my project, I want to log some system call
> information.
>
> Basically, every time a system call is made in my PV DomU, I just
want to
> print a line like "System call made from DomU, systemcall id = xx".
That is
> all I need for now.
>
> I have some questions regarding the same.
> 1. This might be a stupid question, but here goes.
> After I modify source code, should I do the whole compilation/install
> process to see my changes.
> ie. should i do "make and install xen, tools and stubdom" or will
"make
> and install xen" suffice ?
>
> 2. How is the system call flow happening in Xen?
> Where in the code is the system call being intercepted by the
hypervisor
> for a PV DomU. ?
>
> I found some information from this paper,
>
http://hal.archives-ouvertes.fr/docs/00/43/10/31/PDF/Technical_Report_Sys...
>
> but still am not clear about the whole picture.
>
> Is there documentation available explaining for how system calls are
> handled in Xen ?
> The Xen code is quite large, and I am sorry to say I get lost reading
it
> without some kind of knowledge.
>
> 3. How to log data?
> I see printk statements in the code. Are printk statements tied to a
> certain logging level ? Should I add "loglvl=all guest_loglvl=all" to
my
> Dom0 grub to see the output from printk statements ?
> Also, which output file should I be seeing for my scenario?
> /var/log/xen/xend.log ?
>
> I apologize for the long email.
> Please take some time out and kindly reply.
>
>
> --
> Ranjith krishnan
>
Xentrace and xenalyze are your friends for this.