> Simply attempt the access. We are in violent agreement. I'm not the one asking for the new instruction; I'm one of the ones saying that such an instruction wouldn't solve the TOCTTOU issue.
> If it's a Supervisor function it must page-fix the buffer. No. It needs to copy data into protected storage, but generally that storage can be pageable. > I suppose access methods do all that routinely. With the exception of VSAM local shared resources, the access methods have separate user-side storage for each open ACB/DCB. For VSAM and VTAM, once you get beyond the user's private area, all bets are off. The last time that the code was available for customer scrutiny, there was page fixing of storage related to STARTIO, but I don't recall anything else that was page fixed. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Assembler List [[email protected]] on behalf of Paul Gilmartin [[email protected]] Sent: Sunday, March 6, 2022 2:31 PM To: [email protected] Subject: Re: Testing Address validity On Mar 6, 2022, at 11:55:46, Seymour J Metz wrote: > > Well, if there was a burning need for it then they could add an instruction > that worked like TPROT but took an interrupt instead of a CC 3 for invalid > address. Even if you had it, there would stil be the TOFTTOU issue. > ??? Simply attempt the access. o If it fails, diagnose the interrupt code. o If it succeeds, you're done; no TOFTTOU. (Aren't we back where we started?) If callers intercept the interrupt, they are assuming the responsibility of diagnosing. (The documentation might warn them.) If it's a Supervisor function it must page-fix the buffer. After copying the pointer to protected storage. And ensuring that concurrent tasks don't use overleaping buffers. I suppose access methods do all that routinely. -- gil
