The Memory Sinkhole [pdf]

Post by MrBuddyCasino » Sat, Aug 08, 2015, 2:46 PM UTC

Post by mschuster91 » Sat, Aug 08, 2015, 4:14 PM UTC

Qantourisc wrote: post #3

I must be missing something: but why did they keep reimplementing this in modern CPU's ? (Or did they remove it from modern CPU's?)

Post by ckv428 » Sat, Aug 08, 2015, 5:20 PM UTC

MrBuddyCasino wrote: post #2

tl;dr: x86 processors have an ancient feature (unused by now) that allows to move the memory window of the APIC registers to an arbitrary address. By moving this window, it is possible to circumvent built-in hardware security checks and access the highly privileged System Management Mode (Ring -2) from Ring 0 Code.

Post by TazeTSchnitzel » Sat, Aug 08, 2015, 6:29 PM UTC

mschuster91 wrote: post #4

Qantourisc wrote: post #3

I must be missing something: but why did they keep reimplementing this in modern CPU's ? (Or did they remove it from modern CPU's?)

Intel did remove it in the modern CPUs after the author alerted them. As for why it stuck around until now: backwards compatibility + that CPUs are rather rarely constructed from scratch, rather evolved upon.