RE: [PATCH 7/8] Windows gdb: Implement XState (Intel AVX) support

> -----Original Message-----
> From: Hannes Domani <[email protected]>
> Sent: Freitag, 17. Juli 2026 16:50
> To: [email protected]; Schimpe, Christina
> <[email protected]>
> Subject: Re: [PATCH 7/8] Windows gdb: Implement XState (Intel AVX) support
> 
>  Am Freitag, 17. Juli 2026 um 16:16:31 MESZ hat Schimpe, Christina
> <[email protected]> Folgendes geschrieben:
> 
> > > -----Original Message-----
> > > From: Hannes Domani <[email protected]>
> > > Sent: Freitag, 17. Juli 2026 15:47
> > > To: [email protected]; Schimpe, Christina
> > > <[email protected]>
> > > Subject: Re: [PATCH 7/8] Windows gdb: Implement XState (Intel AVX)
> > > support
> > >
> > >  Am Freitag, 17. Juli 2026 um 14:54:59 MESZ hat Schimpe, Christina
> > ><[email protected]> Folgendes geschrieben:
> > >
> > > > Hi Hannes,
> > > >
> > > > Thank you for working on this.
> > > > It appears that this patch uses the same commit message header as
> > > > patch #8. Is it intentional that these are separate commits?
> > >
> > > This one is the gdb part, and #8 is the gdbserver part, that is
> > > stated in the title.
> >
> > Oups, I wonder how I came to that conclusion.  Sorry for that.
> >
> > >
> > > > In any case, IMO, commit messages should not have identical headers.
> > > > Also, this patch seems big enough for a commit message which is
> > > > not header only. :)
> >
> > This part still stands for the commit message. Since it's not only avx
> > registers, I believe it makes sense to share more details here.
> 
> Yes, I will do that.
> 
> 
> > > > Do any AVX-* specific tests pass on Windows now? If so, it would
> > > > be helpful to mention that in the commit message as well.
> > >
> > > I actually planned to add that info, but forgot.
> > >
> > > These tests then pass on Windows:
> > > gdb.arch/i386-avx.exp
> > > gdb.arch/i386-avx512.exp
> >
> > What's the state for SSE  (gdb.arch/i386-sse.exp) ?
> 
> i386-sse.exp works since patch #1, it was only a compile issue of the test
> itself.
> I will mention this in the patch as well.

Thanks.

> 
> > I also saw you introduced some code for PKRU and the shadow stack
> pointer.
> > We have GDB tests for those registers, too:
> > - gdb.arch/i386-pkru.exp
> > - gdb.arch/amd64-shadow-stack*.exp
> 
> For these I just added the equivalent code as is done on Linux, without really
> knowing what they are for.
> 
> i386-pkru.exp tells me:
> 
> (gdb) print have_pkru()
> $1 = 0
> (gdb) PASS: gdb.arch/i386-pkru.exp: probe PKRU support
> UNSUPPORTED: gdb.arch/i386-pkru.exp: processor does not support
> protection key feature.
> 
> Do only certain CPU's have this register?

Most recent CPUs should have it. To be sure you can check if the corresponding bit
is configured in xcr0.
I believe for windows this should be the mask returned by get_xstate_features_mask.

If your cpu does have it, I think you must look at the test in more detail to find out why it's
unsupported. It might need some adaptions for windows.

> 
> And amd64-shadow-stack.exp:
> 
> (gdb) print $pl3_ssp
> $1 = (void *) 0x0
> (gdb) FAIL: gdb.arch/amd64-shadow-stack.exp: test shadow stack support
> 
> No idea if that should work, since Windows is supplying data for the $pl3_ssp
> register.
> 
> 
> Hannes

Without knowing any of the details in windows I believe adding full support for CET shadow
stack might need some more changes. At least for linux, this was the case:
https://inbox.sourceware.org/gdb-patches/[email protected]/

I believe it would be better to handle this in a separate patch-(series).
This also applies for any other register that you add and whose dedicated test does not pass.

Does that make sense to you?

Christina 
Intel Deutschland GmbH

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