Re: What is a capability?
Bill Frantz <[email protected]>
| Newsgroups | gmane.comp.capabilities.general |
|---|---|
| Message-ID | <r422Ps-1075i-8CC8706D78FF4837B16F305F1C444036@Williams-MacBook-Pro.local> |
On 1/8/15 at 4:53 PM, kpreid-M/[email protected] (Kevin Reid) wrote: >KeyKOS is not an object-capability system because the way you >interact with a capability varies depending on the type of the >capability. For example, if my understanding is correct, >capabilities to memory pages are never interacted with by >sending messages to them, but rather by inserting them in page tables. You can call a page key and get a read-only page key. We considered implementing a fetch/store operation, but there was never a compelling use case for it. >Start keys are more ocap-ish, since they are implemented by >application code, but (I am assuming) there is no expectation >of any commonality of protocol or a notion of "selector" >between different start keys. The 32 bit order code is almost always used as a method selector. The 8 bit "data byte" is sometimes used as a facit ID, but most often was ignored. It could be used to reduce the domain (object) count in a system by 256, but that's a hacky optimization. Cheers - Bill ----------------------------------------------------------------------- Bill Frantz | Since the IBM Selectric, keyboards have gotten 408-356-8506 | steadily worse. Now we have touchscreen keyboards. www.pwpconsult.com | Can we make something even worse?