Re: You could do worse than Mach ports

[Ulrich Hobelmann <u.hobelmann@xxxxxx>]

Matthew Dillon wrote:
>     Yes, precisely.  I feel that protection boundaries are better handled
>     by the port agent.  e.g. this is how a typical message is sent:
>
>     SomeMsg blah;
>
>     blah.XXX = ...				/* ... fill in blah ... */
>     code = targetPort->mp_SendMsg(targetPort, &blah);	/* send the message */
>     if (code == EASYNC)				/* async completion?  */
> 	code = waitMsg(&blah);			/* yes, wait */
>     return(code);				/* else sync completion */
>
>
>     For user<->user messaging mp_sendMsg() is simply the target port's
>     message handling function.  Ditto for kernel<->kernel messaging.  
>
>     But for user<->kernel messaging or kernel<->user messaging the 
>     targetPort would be the local representation of the port (not the
>     actual port), and mp_SendMsg() would broker the message to the actual
>     port, doing whatever work is required to deal with the protection
>     boundary.
>
>     Theoretically this means we can write device and VFS driveres that can
>     be compiled up as either user OR kernel modules.  They would see the
>     same API either way and only mp_SendMsg() would change.

Could this be done by dynamic linkage?  So the ELF-symbol mp_SendMsg 
would be translated by the linker, or the in-kernel module loader to the 
right function depending on context.

This makes it easy to unload a module from the kernel und reload it as a 
user process for debugging etc.

Ulrich