11 Jan 2007 22:41
memory safety bug!
Michael Hicks <mwh <at> cs.umd.edu>
2007-01-11 21:41:26 GMT
2007-01-11 21:41:26 GMT
Looks like memory safety is a concern for NASA too: http://www.spaceref.com/news/viewnews.html?id=1185 -Mike
12 Jan 2007 00:05
Re: memory safety bug!
David Hopwood <david.nospam.hopwood <at> blueyonder.co.uk>
2007-01-11 23:05:20 GMT
2007-01-11 23:05:20 GMT
[cross-posted from the Cyclone mailing list to the Erlang list] Michael Hicks wrote: > Looks like memory safety is a concern for NASA too: > > http://www.spaceref.com/news/viewnews.html?id=1185 "We think that the failure was due to a software load we sent up in June of last year. This software tried to synch up two flight processors. Two addresses were incorrect - two memory addresses were over written. As the geometry evolved, we drove the [solar] arrays against a hard stop and the spacecraft went into safe mode. The radiator for the battery pointed at the sun, the temperature went up, and battery failed. But this should be treated as preliminary." The discussion below assumes that this brief description is accurate, as far as it goes. It sounds like memory safety would have been necessary, but not sufficient to avoid mission failure. Memory-safety doesn't prevent run-time errors [*]; it only turns them into "nicer" fault behaviour, for example an exception or a trap to an emergency handler. So what would probably have happened in a memory-safe language is that spacecraft would have gone into safe mode earlier, as a result of whatever fault caused the "two memory addresses [to be] overwritten". However, no memory would have been corrupted as a result of this fault. Upgrading software in flight is always, and foreseeably, a risky operation. What is needed to recover from this kind of situation is a 'downgrade' facility as well as memory safety. By downgrade, I mean a facility that allows the system to go back to a previous state and software configuration in case an upgrade fails. An example of a language that provides this is Erlang (see section 3.8(Continue reading)
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