Re: [PATCH] x86 : Ensure X86_FLAGS_NT is cleared on syscall entry

[Andy Lutomirski]

On Mon, Sep 29, 2014 at 11:59 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> On Mon, 29 Sep 2014, Andy Lutomirski wrote:
>> Presumably interrupt delivery clears NT.  I haven't spotted where that's
>> documented yet.
>
> Nope, that's unrelated.

If it weren't the case, then we'd be totally screwed.  Fortunately, it
is.  I found it: SDM Volume 3 6.12.1.2 says:

(On calls to exception and interrupt
handlers, the processor also clears the VM, RF, and NT flags in the
EFLAGS register,
after they are saved on the stack.)

--Andy
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