|
-----Original Message----- From: mi400-bounces@xxxxxxxxxxxx [mailto:mi400-bounces@xxxxxxxxxxxx]On Behalf Of Dave McKenzie Sent: Thursday, March 10, 2005 3:57 PM To: MI Programming on the AS400 / iSeries Subject: Re: [MI400] using _pcoptr proc. was: Attention Users of *SYSTEM State Walden H. Leverich wrote: > Steve said: >>Actually, I still dont understand the system state thing. > >> Steve, I think the state/domain rules apply when you're using MI to >> manipulate things. The opcodes check that you've got the appropriate >> "rights" and either allow the operation or throw an exception. In your >> case you're below the MI, I don't think you'll be constrained by those >> restrictions. >No, actually, hardware storage protection is a function of the PowerPC >processor (thus "hardware") and exists at all levels. There are two >protection bits for each 4K page of memory that control what access >(read or write) is allowed in user/system state and problem/privileged >state. see Walden! Our system is unexploitable. the higher level language compiler does add a level of protection to the mix. In an RPG program, you cannot reference any bytes of the space prior to the useable portion. >I looked at the address of a *usrspc, and the codes were 2, meaning >reads and writes were allowed in all states. That's because protection >is at the 4K page level, and the usable part of a *usrspc starts at >offset x200 (which is in the first page of the *usrspc, right after the >header Steve modified). Since user state pgms are allowed to write to >*usrspc's, the first page has to be unprotected. In some future >release, IBM could change the usable part to start at x1000 (the second >page) and protect the first page, thus foiling Steve's exploit. Does that mean I could change the object type of a user space to *pgm? -Steve
As an Amazon Associate we earn from qualifying purchases.
This mailing list archive is Copyright 1997-2024 by midrange.com and David Gibbs as a compilation work. Use of the archive is restricted to research of a business or technical nature. Any other uses are prohibited. Full details are available on our policy page. If you have questions about this, please contact [javascript protected email address].
Operating expenses for this site are earned using the Amazon Associate program and Google Adsense.