🚀 go-pugleaf

In article <8906010339.AA12100@jade.berkeley.edu> 451061@upttawa.BITNET (Valentin Pepeleat) writes:

> Deven Corzine <deven@rpi.edu> writes in
> Message-ID: <DEVEN.89May30030703@daniel.rpi.edu>

> > Ah, but you see...  it basically operates on the assumption that
> > there is not only a single address space, but no memory protection
> > as well...

> Ridiculous! Memory protection merely prevents tasks from overwriting
> each other. It does not prevent them from reading each other's
> address space. And by declaring memory to be public, writing in each
> other's space is allowed too.  Read protected memory is useful only
> in multi-user systems.

In some contexts, memory protection DOES mean read-protection as well
as write.  It's implementation-defined, really.  Regardless, the
message passing system _depends_ on absence of memory protection.
Read AND write.  (consider ReplyMsg)  And don't count on MEMF_PUBLIC
ever being meaningful...

> If you have separate address spaces, then you can not read and write
> each other's address space. You share data only by sending messages.
> That is very icky, very Unix-like.

That is very clean.  Reading and writing others' address spaces is
"icky".  Shared memory is often a clumsy method of IPC.  Besides,
shared memory COULD very well be implemented, ON REQUEST, with read-
and write-procted, separately addressed, paged memory.  Stop mixing
the issues.

Deven
--
shadow@[128.113.10.2]   <shadow@pawl.rpi.edu> Deven T. Corzine (518) 272-5847
shadow@[128.113.10.201] <shadow@acm.rpi.edu>  2346 15th St.    Pi-Rho America
deven@rpitsmts.bitnet   <userfxb6@rpitsmts>   Troy, NY 12180-2306  <<tionen>>
"Simple things should be simple and complex things should be possible." - A.K.