On Tue, 6 Mar 2012 20:39:02 +0000, Pate, Gene wrote: >By PCFLIH backdoor I mean a routine whose address >replaced the address of the IBM supplied PCFLIH.
That would be a hook or an intercept. "Backdoor" means something else entirely. >The backdoor routine received control every time a >PC interrupt ITYM a program interruption. >occurred and, based on the reason for the PC >interrupt it either emulated the failing instruction >using available instructions and returned control to >the next sequential instruction or passed control to >the IBM supplied PCFLIH routine for it to process >the PC interrupt. I believe that this is also what >the vendor routine being discussed did. That is certainly not what the vendor routine being discussed is alleged to have done. It is alleged to return to the program that was interrupted in supervisor state. It is further alleged that it is relatively easy for any program to exploit this and to get put into supervisor state. -- Tom Marchant ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN
