Re: x86-64: Maintain 16-byte stack alignment

[Andy Lutomirski]

On Tue, Jan 10, 2017 at 9:05 AM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Tue, Jan 10, 2017 at 6:39 AM, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote:
>>
>> BTW this is with Debian gcc 4.7.2 which does not allow an 8-byte
>> stack alignment as attempted by the Makefile:
>
> I'm pretty sure we have random asm code that may not maintain a
> sus16-byte stack alignment when it calls other code (including, in some
> cases, calling C code).

I suspect so.

If we change this, changing pt_regs might make sense but is kind of
weird.  It also needs to be tested with and without frame pointers.

>
> So I'm not at all convinced that this is a good idea. We shouldn't
> expect 16-byte alignment to be something trustworthy.
>
>                  Linus



-- 
Andy Lutomirski
AMA Capital Management, LLC