[Info-vax] What would be involved in moving RMS into kernel mode ?

[Hein RMS van den Heuvel]

On Tuesday, May 2, 2023 at 9:24:03 AM UTC-4, Simon Clubley wrote:
> If the emulated executive mode is a major reason for the kernel overheads 
> we are seeing on x86-64 VMS, what would be involved in moving RMS from 
> executive mode directly into kernel mode ? 

Nah, have a link time option to run RMS in user mode! I'm mostly serious. 
Moving it to kernel mode you still need to probe the RABs, FABs, XABs and anything those point to.
The protection exec or kernel mode offers is minimal. It makes sure that broken user mode doesn't stomp on data block buffers and corrupts the underlying file impacting downstream usage of those files.  Possibly worse, in user mode buggy programs could impact other, shared, users of those files, specially when global buffers are involved.
Well tough luck, write better program, test them better! 
Exec mode RMS might help the testing but when is the last time your programs accidently tried to touch an rms buffer and got an accvio?
It (exec or kernel) mode only protects against accidental data corruption (bugs). 
It doesn't protect against malicious corruption as anyone with write access can overwrite data. 
Regular file protection handles that. Only allow trusted users, or subsystems holding the right identifier, access to critical files.
Admittedly RMS does use CMKRNL for some odd things like borrowing/stealing ENQLM to get out of a tight spot, but in general user mode could be just fine.

fwiw ... back in the day (30 years) ago, while in VMS Engineering I had access to usermode RMS for debugging purposes. It did exists at the time with minimal restrictions. It was rarely - if ever - used. Mostly we worked of crashdumps and 'live' ANAL/SYSTEM to look at the data structures to debug RMS.

Hein.