[okl4-developer] Direct IPC from OKLinux userland processes toOKL4 services

[Nelson Tam]

Hi all,

On 29/02/2008, at 1:58 PM, Kalamkar, Dhiraj D wrote:

> I am not sure whether OKLinux userland process can access Iguana  
> services directly even after the changes you suggested in OKLinux  
> scheduler. As far as I understand Iguana server and other services  
> are based on Iguana Single Address Space (SAS). i.e. Iguana server  
> and other services work on assumption that they have same virtual to  
> physical mappings for all the threads in Iguana PD (of course with  
> different access rights). As OKLinux user processes are external  
> address spaces (EAS) they can not access iguana services directly.
>
> Of course, after enabling IPC for userland OKLinux process, you can  
> do a raw IPC to any L4 thread and may write services which don’t  
> assume Iguana SAS.


On 29/02/2008, at 2:12 PM, Jorge Torres wrote:

> Yes, one could use L4 native calls, and non SAS based iguana  
> services, like high resolution timers, or driver servers (I guess),


Not all OKL4 services rely on the SAS.  As correctly noted, as long as  
the service doesn't require any sort of shared memory, EAS threads  
would be able to utilise them also.

Which brings me to an earlier question asked by Jorge: how to control  
IPC permissions in L4?  The answer is L4_SecurityControl() (for IPC  
permissions you probably want the wrappers L4_IpcAllow() and cousins).

But as I said before, you shouldn't do this in the OKLinux setup due  
to scheduling reasons.
--
(nt)

Nelson Tam
nelson at ok-labs.com