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From: mitchalsup@aol.com (MitchAlsup1)
Newsgroups: comp.arch
Subject: Re: Stacks, was Segments
Date: Sun, 19 Jan 2025 18:28:40 +0000
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On Sun, 19 Jan 2025 16:33:53 +0000, David Brown wrote:
>
> A two-stack setup can be used in C too.  (The C standards don't require
> a stack at all.)  On the AVR microcontroller, it is not uncommon for C
> implementations to work with a dual stack, since it does not have any
> kind of "[SP + n]" or "[SP + r]" addressing modes, but it /does/ have an
> "[Y + n]" addressing mode using an index register.
>
> Two stacks are also pretty much required for FORTH.
>
> The use of a dual stack could also significantly improve the security of
> systems by separating call/return addresses from data.

In My 66000 the code cannot read/write that other stack with LD and ST
instructions. It can only be accessed by ENTER (stores) and EXIT (LDs).
The mapping PTE is marked RWE = 000.

So, while you can still overrun buffers, you cannot damage the call/
return stack or the preserved registers !!