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Re: [PATCH][RFA/RFC] Stack clash mitigation 0/9
- From: Jeff Law <law at redhat dot com>
- To: Jakub Jelinek <jakub 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 11:35:49 -0600
- Subject: Re: [PATCH][RFA/RFC] Stack clash mitigation 0/9
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On 07/13/2017 11:32 AM, Jakub Jelinek wrote:
> 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.
Opps. Mis-read. Got it totally backwards
Not good. Waiting on Segher for clarification, but will start thinking
about better options than punting :-)
jeff