Xen devel - Nov 2011 - any exit function in xen that is similar to exit_kernel?

Hello all,
I added a hypercall "do_greet" that only prints "Hello
world" to do a
small experiment. After it prints the "hello world", I would it to
exit from Xen and stop current process. For instance:
the hypercall is like this:
int do_greet(){
   pirntk("Hello world\n");
   /*then I would it exit from Xen and stop current process that called it.*/
   exit_?? //exit(0) does not work.
}

If a process at the application level calls this hypercall through
privcmd file, I would like it kill this process after the hypercall
prints "Hello world". Then how to do that?
In linux kernel, there is a function exit_kernel, which switch the
kernel address space into the user address space. But I did not find
any similar function in Xen. Any idea? thanks

-- 
     Best Regards,
                                                                 Baozeng Ding
                                                                 OSTG,NFS,ISCAS

On Tue, Nov 29, 2011 at 2:22 PM, Baozeng <sploving1@gmail.com>
wrote:
> Hello all,
> I added a hypercall "do_greet" that only prints "Hello
world" to do a
> small experiment. After it prints the "hello world", I would it
to
> exit from Xen and stop current process. For instance:
> the hypercall is like this:
> int do_greet(){
>   pirntk("Hello world\n");
>   /*then I would it exit from Xen and stop current process that called
it.*/
>   exit_?? //exit(0) does not work.
> }
>
> If a process at the application level calls this hypercall through
> privcmd file, I would like it kill this process after the hypercall
> prints "Hello world". Then how to do that?
A process is a guest kernel-level construct.  Xen doesn''t know
anything about processes; it only knows things about VMs.  You can
easily kill the guest by doing this:
  domain_crash(current->domain);

If you want the process only to be killed, you have to have the guest
kernel do it.

 -George

2011/12/1 George Dunlap
<George.Dunlap@eu.citrix.com>:
> On Tue, Nov 29, 2011 at 2:22 PM, Baozeng <sploving1@gmail.com> wrote:
>> Hello all,
>> I added a hypercall "do_greet" that only prints "Hello
world" to do a
>> small experiment. After it prints the "hello world", I would
it to
>> exit from Xen and stop current process. For instance:
>> the hypercall is like this:
>> int do_greet(){
>>   pirntk("Hello world\n");
>>   /*then I would it exit from Xen and stop current process that called
it.*/
>>   exit_?? //exit(0) does not work.
>> }
>>
>> If a process at the application level calls this hypercall through
>> privcmd file, I would like it kill this process after the hypercall
>> prints "Hello world". Then how to do that?
>
> A process is a guest kernel-level construct.  Xen doesn''t know
> anything about processes; it only knows things about VMs.  You can
> easily kill the guest by doing this:
>  domain_crash(current->domain);
>
> If you want the process only to be killed, you have to have the guest
> kernel do it.
>
Okay. I know. It need first return to the kernel address space. Then
is there any function that can return the kernel address space from
Xen after the hypercall? like this:
 int do_greet(){
    pirntk("Hello world\n");
    /*then I would it exit from Xen to the kernel.*/
    exit_??  // after that CS and EIP should pointer to the kernel
address space.
 }

if there doesnot exiest such function, how can I know which function
switches kernel into  Xen to trigger such hypercall, so that I can
return it by myself. Is it in the entry.S, when int $82 instruction
happen, then the CS and EIP begin to switch point to Xen? thanks
>  -George


-- 
     Best Regards,
                                                                 Baozeng Ding
                                                                 OSTG,NFS,ISCAS

On Thu, 2011-12-01 at 12:55 +0000, Baozeng wrote:
> 2011/12/1 George Dunlap <George.Dunlap@eu.citrix.com>:
> > On Tue, Nov 29, 2011 at 2:22 PM, Baozeng <sploving1@gmail.com>
wrote:
> >> Hello all,
> >> I added a hypercall "do_greet" that only prints
"Hello world" to do a
> >> small experiment. After it prints the "hello world", I
would it to
> >> exit from Xen and stop current process. For instance:
> >> the hypercall is like this:
> >> int do_greet(){
> >>   pirntk("Hello world\n");
> >>   /*then I would it exit from Xen and stop current process that
called it.*/
> >>   exit_?? //exit(0) does not work.
> >> }
> >>
> >> If a process at the application level calls this hypercall through
> >> privcmd file, I would like it kill this process after the
hypercall
> >> prints "Hello world". Then how to do that?
> >
> > A process is a guest kernel-level construct.  Xen doesn''t
know
> > anything about processes; it only knows things about VMs.  You can
> > easily kill the guest by doing this:
> >  domain_crash(current->domain);
> >
> > If you want the process only to be killed, you have to have the guest
> > kernel do it.
> >
> Okay. I know. It need first return to the kernel address space. Then
> is there any function that can return the kernel address space from
> Xen after the hypercall? like this:
>  int do_greet(){
>     pirntk("Hello world\n");
>     /*then I would it exit from Xen to the kernel.*/
>     exit_??  // after that CS and EIP should pointer to the kernel
> address space.
>  }
> 
> if there doesnot exiest such function, how can I know which function
> switches kernel into  Xen to trigger such hypercall, so that I can
> return it by myself. Is it in the entry.S, when int $82 instruction
> happen, then the CS and EIP begin to switch point to Xen? thanks
This is a quite strange thing to want to do. Please can you explain your
end goal (i.e. what problem are you trying to solve with this)? Perhaps
there is a better way.

Ian.