On 05/31/2020 02:06 AM, jim stephens via cctalk wrote:
On 5/30/2020 11:15 PM, Eric Smith via cctalk wrote:
On 05/29/2020 02:38 PM, Noel Chiappa via cctalk wrote:
<snip>
Low-level machines did not even have storage protection
keys, and on the /40 and /50 (I think) it was an option,
although I'd guess almost any /50 had it installed.
Our /50 had it and I have never seen any indication in the
documentation for the hardware that
indicated that it was an option.
I don't think that either MVT or MFT would have been very
stable without it. I certainly spent a lot of time
studying how to get around it, and am responsible for a
couple of SPIE patches in the MVT product
from exploits trying to get into supervisor mode to muck
with such.
Yes, the SPIE call as supplied from IBM was surely the
security hole big enough for 5 ocean liners abreast to steam
right through! Everybody had to patch that, and the patch
was fairly simple. But, it was a clear indication of how
LITTLE IBM thought about security. Of course, they were
thinking about banks where 3 teams reviewed code before it
ever ran on the machine, not universities where kids would
try all sorts of mischief.
Yes, I know supervisor state isn't tied to the storage
keys, but that was the way I went to
try to circumvent the storage keys.
Oh, once you have the P bit set to zero, you can do
anything, such as changing the storage protection key of
your own program.
Jon
