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Re: [MiNT] Proposal for SLB extension



Hi!

On Mon, Apr 17, 2000 at 10:22:12AM +0200, Julian Reschke wrote:
> The only environment in question would be MiNT with MP enabled.

It seems you haven't read my mails carefully enough. Memory not
Malloc()ed by MiNT at startup (and that includes the GEMDOS variables of
TOS, of course) is _not_ at all protected. Why should it help to run
problematic TSRs before MiNT, if that weren't the case? I already
pointed that out ...

Of course, using a variable which is also _writeable_ by a user
application isn't actually a good idea, as it may impose security risks
(consider an SLB using the basepage address for some access checks).

> Could you elaborate where you want to put that variable? I would guess
> it needs to be in the process' memory space, otherwise  you'll
> probably get a nasty comment from Frank :-)

Why? It just needs to be a variable in memory writeable by the kernel
and readable by user processes. Unfortunately, the current memory
protection model doesn't allow for memory of this kind (supervisor
writeable, user readable), as the MMU trees for supervisor and user mode
are identical.

Thus, a temporary solution would be global memory, with the security
risks noted above. Currently, the kernel's BSS segment is global, thus
using a variable there will do for the moment.


Ciao

Thomas


-- 
Thomas Binder (Gryf @ IRCNet)  gryf@hrzpub.tu-darmstadt.de
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