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Re: [PATCH][RFA/RFC] Stack clash mitigation 0/9
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Jeff Law <law at redhat dot com>
- Cc: Segher Boessenkool <segher at kernel dot crashing dot org>, gcc-patches <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 13 Jul 2017 19:32:51 +0200
- Subject: Re: [PATCH][RFA/RFC] Stack clash mitigation 0/9
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- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Thu, Jul 13, 2017 at 11:28:17AM -0600, Jeff Law wrote:
> On 07/12/2017 04:44 PM, Segher Boessenkool wrote:
> > On Tue, Jul 11, 2017 at 03:19:36PM -0600, Jeff Law wrote:
> >> Examples of implicit probes include
> >
> >> 2. ABI mandates that *sp always contain a backchain pointer (ppc)
> >
> > In the ELFv2 ABI a backchain is not required. GCC still always has
> > one afaik. I'll find out more.
> Please do. I was under the impression it was mandated by the earlier
> ABIs as well. If it isn't, then I don't think we can depend on it for
> the older ABIs.
>
> That wouldn't be the end of the world -- it's pretty clear that ppc64le
> is the future and we'd get good code there. I wouldn't lose much sleep
> if ppc32 and ppc64 big endian had a less efficient probing scheme.
?? Segher said in ELFv2 ABI it is not required, so that would mean
it does affect ppc64le and does not affect ppc32 or ppc64.
So, we wouldn't get good code for ppc64le and would get one for ppc32 and
ppc64.
Jakub