RE: [PATCH 14/15] x86/fsgsbase/64: Support legacy behavior when FS/GS updated by ptracer

From: Bae, Chang Seok
Date: Thu Mar 22 2018 - 17:18:01 EST



________________________________________
From: Andy Lutomirski [luto@xxxxxxxxxx]
Sent: Thursday, March 22, 2018 09:53
>>> But your patch doesn't actually do this, since gdb will just do
>>> SETREGS anyway, right?
>> GDB does SETREGS on any exclusive (FS/GS) updates in inferior call.

> This means that your patch has exactly the same effect as the code in
> my git tree, right? Then let's stick with something like what's in my
> git tree, since it's far simpler.

Difference is if flipping FS/GS multiple times, user may check the base from LDT.
But I don't have strong will to keep arguing this; Markus or somebody might
want to say something.

The whole point as I understand is to avoid any regression on legacy ptracers.
If a strong confidence lies on the simple version, let me. My first thought bought
this in fact.

Thanks,
Chang