On: Breaking the x86 Instruction Set: how to find undo...

[vardump]

You don't really need even that.

You just need a set of magic register values, like how CPUID [0] instruction already works.

[0]: http://www.sandpile.org/x86/cpuid.htm

[jevinskie → vardump]

Yup, this was done in this years USENIX with AMD microcode. See the exploits that check for magic register values at [0] and the paper at [1].

[0]: https://github.com/RUB-SysSec/Microcode/tree/master/updates

[1]: http://syssec.rub.de/research/publications/microcode-reversi...