On 1 December 2010 10:46, Edward Jaffe <[email protected]> wrote:
> You can use an ordinary branch instruction (e.g., BASSM 14,15) to branch to > code above the bar. If you're running enabled, you won't execute for long... > :-D Just how does it fail? Is the PSW instruction address silently truncated upon return from an interrupt as a result of its having been saved in a legacy control block, leading to continued execution at a presumably incorrect address, or is there some active detection and abend? Something else? What if I install the same code at, say 00000000_00123000 and 00000070_00123000, and branch to the above-the-bar code? Yes, I''m sure I could try it, and perhaps there even exists enough non-secret knowledge outside IBM to research it, but since I can't think of a real use for it I'll leave it as a Gedankenexperiment . It is, though, curious that there must be, as Paul Gilmartin points out, quite a bit of infrastructure already there in support of 64-bit addresses. The real PSW is at all times beyond the early stage of IPL a zArch one of 128 bits, and it must be saved and restored properly, as must things like PER addresses in control registers. What remains to be done? Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
