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Old 29 June 2016, 16:52   #18
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Join Date: Sep 2007
Location: Rotterdam/Netherlands
Age: 40
Posts: 2,707
Originally Posted by meynaf View Post
Exec itself has many linked lists, in which items can be located anywhere (new tasks, interrupts, etc, can be in memory allocated by any task). But most of it runs in user mode. And programs walking these lists also do. Because it's much faster this way.
Programs don't have any business doing that in most cases.

Originally Posted by Daedalus View Post
Yep, that's fine, but what's to stop another task accessing that memory once it's marked as shared, possibly resulting in corruption? That's not total memory protection when one task can corrupt another's data, even if most memory isn't shared. It just reduces the risk of issues.
The OS can give a receiving task read-only privileges for the received message buffer. If the receiving task wants to reply to the message, it uses it's own buffer, and sends that pointer over. The task that receives the reply then also has read-only privileges for the received buffer.

Originally Posted by ReadOnlyCat View Post
Well, I want memory protection all the time since I am not interested in one unknown program taking the whole machine down because of a stupid bad pointer while I am busy using it.
In my hypothetical OS that would mean that you just never turn memory protection off, at the cost of speed.

Originally Posted by ReadOnlyCat View Post
Keeping programs well behaved is not my job
Yes, it is. Just because the OS doesn't force you to do anything in particular, doesn't mean that you should mess around simply because you can. An OS without memory protection actually forces you to play nice, or your software ends up being crappy.

Originally Posted by ReadOnlyCat View Post
Now, whether memory protection is worth the cost on an underpowered 030 is a valid debate
I think everyone can agree that optional memory protection is useful for development.

Originally Posted by ReadOnlyCat View Post
but then again why would I want to work regularly on such a machine?
Why use an Amiga, then?
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