No, it is a natural result of an implemention which treats setting the A bit as
an abnormal flow (e.g. in microcode as opposed to hardware).
On September 29, 2015 7:11:59 PM PDT, ebied...@xmission.com wrote:
>"H. Peter Anvin" writes:
>
>> On 09/29/2015 06:20 PM, Eric W. Biederman wrote:
>>> Linu
"H. Peter Anvin" writes:
> On 09/29/2015 06:20 PM, Eric W. Biederman wrote:
>> Linus Torvalds writes:
>>
>>> On Tue, Sep 29, 2015 at 1:35 PM, Andy Lutomirski
>>> wrote:
Does anyone know what happens if you stick a non-accessed segment in
the GDT, map the GDT RO, and access it?
On 09/29/2015 06:20 PM, Eric W. Biederman wrote:
> Linus Torvalds writes:
>
>> On Tue, Sep 29, 2015 at 1:35 PM, Andy Lutomirski wrote:
>>>
>>> Does anyone know what happens if you stick a non-accessed segment in
>>> the GDT, map the GDT RO, and access it?
>>
>> You should get a #PF, as you guess
Linus Torvalds writes:
> On Tue, Sep 29, 2015 at 1:35 PM, Andy Lutomirski wrote:
>>
>> Does anyone know what happens if you stick a non-accessed segment in
>> the GDT, map the GDT RO, and access it?
>
> You should get a #PF, as you guess, but go ahead and test it if you
> want to make sure.
I t
On 09/29/2015 11:02 AM, Andy Lutomirski wrote:
> On Tue, Sep 29, 2015 at 10:50 AM, Linus Torvalds
> wrote:
>> On Tue, Sep 29, 2015 at 1:35 PM, Andy Lutomirski wrote:
>>>
>>> Does anyone know what happens if you stick a non-accessed segment in
>>> the GDT, map the GDT RO, and access it?
>>
>> You
On Tue, Sep 29, 2015 at 11:18 AM, H. Peter Anvin wrote:
> SGDT would be easy to use, and it is logical that it is faster since it reads
> an internal register. SIDT does too but unlike the GDT has a secondary limit
> (it can never be larger than 4096 bytes) and so all limits in the range
> 409
Ugh. Didn't realize that.
On September 29, 2015 11:22:04 AM PDT, Andy Lutomirski
wrote:
>On Tue, Sep 29, 2015 at 11:18 AM, H. Peter Anvin wrote:
>> SGDT would be easy to use, and it is logical that it is faster since
>it reads an internal register. SIDT does too but unlike the GDT has a
>seco
SGDT would be easy to use, and it is logical that it is faster since it reads
an internal register. SIDT does too but unlike the GDT has a secondary limit
(it can never be larger than 4096 bytes) and so all limits in the range
4095-65535 are exactly equivalent.
Anything that causes a write to
On Tue, Sep 29, 2015 at 10:50 AM, Linus Torvalds
wrote:
> On Tue, Sep 29, 2015 at 1:35 PM, Andy Lutomirski wrote:
>>
>> Does anyone know what happens if you stick a non-accessed segment in
>> the GDT, map the GDT RO, and access it?
>
> You should get a #PF, as you guess, but go ahead and test it
On Tue, Sep 29, 2015 at 1:35 PM, Andy Lutomirski wrote:
>
> Does anyone know what happens if you stick a non-accessed segment in
> the GDT, map the GDT RO, and access it?
You should get a #PF, as you guess, but go ahead and test it if you
want to make sure.
We do something very similar for the o
On Sep 29, 2015 2:01 AM, "Ingo Molnar" wrote:
>
>
> * Denys Vlasenko wrote:
>
> > On 09/28/2015 09:58 AM, Ingo Molnar wrote:
> > >
> > > * Denys Vlasenko wrote:
> > >
> > >> On 09/26/2015 09:50 PM, H. Peter Anvin wrote:
> > >>> NAK. We really should map the GDT read-only on all 64 bit systems,
* Denys Vlasenko wrote:
> On 09/28/2015 09:58 AM, Ingo Molnar wrote:
> >
> > * Denys Vlasenko wrote:
> >
> >> On 09/26/2015 09:50 PM, H. Peter Anvin wrote:
> >>> NAK. We really should map the GDT read-only on all 64 bit systems,
> >>> since we can't hide the address from SLDT. Same with the
On 09/28/2015 09:58 AM, Ingo Molnar wrote:
>
> * Denys Vlasenko wrote:
>
>> On 09/26/2015 09:50 PM, H. Peter Anvin wrote:
>>> NAK. We really should map the GDT read-only on all 64 bit systems,
>>> since we can't hide the address from SLDT. Same with the IDT.
>>
>> Sorry, I don't understand you
* Denys Vlasenko wrote:
> On 09/26/2015 09:50 PM, H. Peter Anvin wrote:
> > NAK. We really should map the GDT read-only on all 64 bit systems,
> > since we can't hide the address from SLDT. Same with the IDT.
>
> Sorry, I don't understand your point.
So the problem is that right now the SGDT
On 09/26/2015 09:50 PM, H. Peter Anvin wrote:
> NAK. We really should map the GDT read-only on all 64 bit systems,
> since we can't hide the address from SLDT. Same with the IDT.
Sorry, I don't understand your point.
> On September 26, 2015 11:00:40 AM PDT, Denys Vlasenko
> wrote:
>> We have
NAK. We really should map the GDT read-only on all 64 bit systems, since we
can't hide the address from SLDT. Same with the IDT.
On September 26, 2015 11:00:40 AM PDT, Denys Vlasenko
wrote:
>We have our GDT in a page-sized per-cpu structure, gdt_page.
>
>On x86_64 kernel, GDT is 128 bytes - o
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