[Info-vax] CRTL and RMS vs SSIO

[Stephen Hoffman]

On 2021-10-13 23:57:00 +0000, John Dallman said:

> In article <sjpojk$ctb$1 at dont-email.me>, seaohveh at hoffmanlabs.invalid
> (Stephen Hoffman) wrote:
> 
>> To Simon's comment, how DCL gets mapped into process address space is 
>> just ugly, too. And hard to debug.
> 
> Can someone point me to the documentation on this? It's something I've 
> never encountered.

IDSM.

LOGINOUT activates DCL into P0 space to size it, then performs a 
rundown, allocates the necessary address space in P1 for DCL and for 
its tables, and activates (merges) DCL again.

Other CLIs are activated (merged) directly into P1.

The debugger doesn't know from P1 supervisor code, which leaves you 
with delta, with your own debugging code, breadcrumb debugging, maybe 
the tr_print ring buffers, etc.

#include <vms_macros.h>
…
tr_print(( “hello, world %d”, i ));

There are a few examples of CLIs in older DECUS and probably in 
Freeware open-source listings, not that they're at all common.  
DEC/shell was one of the few products offered.

In L4 or other such operating system designs, I'd tend to assume any 
CLI will either be chained activations with the images, or will be 
operating in a separate process.

This if the hardware lacks a ring for the CLI, or if the OS isn't 
inclined to create a ring for the CLI as VSI is doing with the x86-64 
port.


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