[Info-vax] RMS and SSIO (again)

[Simon Clubley]

On 2022-01-11, Arne Vajhøj <arne at vajhoej.dk> wrote:
> On 1/11/2022 1:43 PM, Simon Clubley wrote:
>> BTW, am I the only one who thinks it's a pity that stacks don't grow
>> upwards towards higher addresses instead of downwards towards lower
>> addresses, and with a guard page at the top of the space allocated to
>> the stack ?
>> 
>> After all, when using virtual memory, the space allocated to the stack
>> isn't actually allocated from memory until its needed.
>
> I think:
>
> K stack
> E stack
> S stack
> U stack
> unused
> U heap
>
> is more logical than:
>
> stop
> unused
> U stack
> S stack
> E stack
> K stack
> unused
> U heap
>
>:-)
>
> Arne
>

You appear to be thinking in the above diagram that they are all part of
one big stack.

That's not correct because the multiple stacks outside of user space
all have their own allocated address ranges with page protections to match.

Even if they were contiguous, one stack couldn't grow into another stack
and there's no reason why the other non-user stacks couldn't grow upwards
within their own allocated address ranges either.

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.