Re: [PATCH] x86-64: Fix TLSDESC relaxation for x32

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Mon, Jan 20, 2020 at 7:38 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 20.01.2020 16:28, H.J. Lu wrote:
> > On Mon, Jan 20, 2020 at 7:18 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>
> >> On 20.01.2020 15:55, H.J. Lu wrote:
> >>> We need to support both sequences for x32.  For both GDesc -> IE/LE
> >>> transitions,
> >>>
> >>> 67 ff 10              call    *x@TLSCALL(%eax)
> >>>
> >>> should relaxed to
> >>>
> >>> 0f 1f 00              nopl    (%rax)
> >>
> >> Since, like it is phrased here, the patch also uses this
> >> unconditionally, I wonder if this is the best choice: Linux,
> >> for example, has a number of cases where it wouldn't use
> >> this NOP form even on 64-bit.
> >>
> >
> > Assembler has been using this 3-byte NOP in 64-bit for
> > a long time.  What other options are you suggesting?
>
> The traditional K8 NOPs (up to three [iirc] 0x66 followed by
> 0x90), and preferably controllable in some way.
>

We have been doing this way for many years.  I don't think
we should change it now.

-- 
H.J.