John, here is some sample Assembler code to switch to System Key 0,
execute the required instructions, and then switch pack to the original
storage key.
IPK , Save Storage Protect Key in R2
SPKA 0 Get System Key 0
... Your Instructions that need Key 0
* If your code needs to modify R2, R2 must be saved and restored before
* executing the following instruction.
SPKA 0(R2) Restore Storage Protect Key
--
Dale R. Smith
"Logic merely enables one to be wrong with authority."
- Doctor Who
On Thu, 30 Aug 2007 12:53:13 -0400, John Woods <[EMAIL PROTECTED]> wrote
:
>I have a C application running in user mode that I would like to have ca
ll
>an assembler subroutine that currently uses the (good old) BALR interfac
e
>to VCADTLKP to see if a disk mode is accessed... I know, I know... but
hey,
>the code works and it does what I want. The only problem, of course, is
>that the C code is running is user mode and the assembler code would
really
>like to be in "( SYSTEM" mode. It's been a long time since I wrote a lo
t
>of CMS code, but I seem to remember that there was a reasonably easy way
to
>flip in and out of SYSTEM mode (I think I need storage key zero as
>well). I know I could restruture everything, but I'm trying to avoid th
at
>if possible. A few lines of assembler would certainly be easier than
>changing a few lines of C because the C application is shared between a
>number of different people... weanies, actually. ;-)
>
>Thanks
>
>John
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