Re: Dealing with the NMI mess

From: Ingo Molnar
Date: Mon Sep 07 2015 - 03:42:27 EST

* Maciej W. Rozycki <macro@xxxxxxxxxxxxxx> wrote:

> I did some work on this a few years ago, including emulating DR0-7 accesses in
> software down the JTAG handler upon a General Detect fault to keep the kernel
> both happy and away from real debug registers. ;) Yes, you can debug any
> software with this stuff, including the Linux kernel: set instruction and data
> breakpoints, single-step it, poke at all hardware registers, including
> descriptor registers not otherwise accessible (you can set funny modes for
> segments, also in the 64-bit mode), etc. One complication though is you operate
> on physical addresses when poking at memory, you can't ask the CPU's MMU to
> remap them for you (you can walk page tables manually of course, just as the MMU
> would).

Essentially the ICE breakpoint instruction enters SMM mode?


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