Re: L4-hurd Digest, Vol 6, Issue 12

[Fortes Marcelo]

First of all Thank you Moritz Schulte and Marcus
Brinkmann by patience and explanation.

--- Marcus Brinkmann
<address@hidden> escreveu: > On
Mon, May 12, 2003 at 05:29:29PM -0300, Fortes
> Marcelo wrote:
> > 1) have some server of Hurd running on top of L4?
> > or it needs to be translated to synchronous
> message
> > passing yet?
> 
> So far there are only design concepts, and partial
> implementations of some
> features we will need.  We don't need asynchronous
> messages, but there have
> been other details to be worked out.  Most issues
> have been clarified by
> now (at least roughly), though.  We are far from
> having anything useful
> running on it.
> 
> > 2) Hurd is almost using 100% Pthreads instead
> cthreads
> > in source code how does it impact over you work?
> 
> The Hurd uses cthreads, but people worked on porting
> it over to pthreads. 
> The Hurd on top of L4 will use pthreads.  Pthreads
> will be the only high
> level thread library on the Hurd in the future.
>  
> > 3)There are some ideas of Hurd on top of Mach that
> can
> > be subverted by port it to run on top of L4?
> 
> Is that a question?  Mach IPC is almost network
> transparent, while L4 IPC is
> highly not.  So I guess that getting RPCs over a
> network will be a tad more
> difficult on L4 to get right.  There are other
> things like that, but nothing
> fundamental.
>  
> > 4)About Unix compatibility how much it will be
> > Unix-Like OS running "SCO Unix" binaries for
> exemple?
> 
> We have no interest in running proprietary software
> or having compatibility
> with proprietary systems ourselves.  What could
> happen is GNU/Linux
> compatibility at some time because that would be
> quite easy because we use
> the same tools and glibc.
> In general, L4 seems to allow system call emulation
> by the exception handler.
> So as long as you get exceptions for everything you
> want to emulate, you
> will be, at least conceptionally, be able to do so. 
> This is not different
> from Mach.

  So GNU is an operating system to replace Unix 
The question is not about proprietary or non
proprietary software (AKA: FreeSoftware). it is about
technic compability with Unix (SystemV or BSD
flavours)
becouse hundred of thousands who uses programs to
average Unix and may port it to GNU as a Unix Clone
with full compatibility. I used "SCO Unix" only as an
exemple.
  
> > 5)Can Someone please explain-me about the Hurd
> policy
> > of "user ring 0" or a non root administrator OS
> with
> > full power over the system? icannot understand a
> Unix
> > system with user 100% independent of super user...
> > (maybe i have not understooded this concept)
> 
> I hope you have read the documentation on our web
> site. 
 
  Yes i read it.(but it was not so clear)

> The authentication
> mechanism allows communication between untrusted
> users and untrusted
> servers.  All system functionality is implemented by
> cooperating, but
> independent servers.  Users can add their own
> servers, and use them instead
> the system servers if they want.  This way they can
> change the personality
> of the system without affecting anybody else.  The
> authentication mechanism
> guarantees that a user can not compromise the
> security of the overall system
> or other users in particular while this is done.

 Ok Now i understand that the auth server does the
work of security policy(Thank you Marcus). But the
Superuser is the main user with special privilegies
with auth server?

> User ring 0 is taken by L4.  The Hurd itself does
> not run with any kernel
> priviledges (it runs entirely in user space).
  
  Yes i understand this concept about Servers running
in user space.
  
> However, some components of
> the Hurd needs to run with privileges that a normal
> user doesn't have (like
> the privileges to control arbirtary threads and
> tasks, and to access the
> devices).  This functionality is provided by the
> kernel (Mach had special
> privileged ports, L4 has the rootserver threads).
> 
> Thanks,
> Marcus
> 
  Thank you very much Marcus !!!

  Right now please just two more questions:
1) The actual port to new variants of L4 wroted in C++
gives to entire system the desired performance
expected of an usable Unix-like system? i know about
the super fast IPC, and minimum of system calls into
L4 and non cacheable synchronous messages, and another
different  things between Mach and L4 that does Mach
so slow, running with multi-servers. but performance
is yet a point to use to see as a reasonable thoughts.
  So Hurd on top on new L4 implementations can have a
performance comparated to GNU/Linux, SCO-Unix or
another Unix monolithic kernels for exemple?

2) what about people that works with Hurd on Mach ?
why they dont join to L4 group ant throuw Mach away?
becouse they knows Mach problems.



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