Re: [PATCH v2] x86: Remove compat vdso support

Andy Lutomirski
2014-03-12T23:43:57Z

On Wed, Mar 12, 2014 at 4:06 PM, H. Peter Anvin <hpa@linux.intel.com> wrote:
> On 03/12/2014 02:49 PM, Andy Lutomirski wrote:
>> On Wed, Mar 12, 2014 at 2:46 PM, Linus Torvalds
>> <torvalds@linux-foundation.org> wrote:
>>> On Wed, Mar 12, 2014 at 2:37 PM, H. Peter Anvin <hpa@linux.intel.com> wrote:
>>>>
>>>> How would that deal with the legacy vsyscall case for x86-64? Just rely
>>>> on the "legacy vsyscall emulation" (which seems to have its own class of
>>>> problems...)?
>>>
>>> It does?
>>>
>>> We *default* to emulation, and have for over two years now (since
>>> v3.4). If there are problems with it, we need to fix those.
>>
>> Even in the non-default "vsyscall=native" case, the vsyscall pages
>> just contains syscalls. It does not need to access the vvar page, the
>> hpet, or anything else that the vdso uses.
>>
>
> Ah, right. I let that detail slip the mind.
>
> I do hear vsyscall=native still being used as a workaround for problems,
> but yes, just making it call the kernel is fine, of course.

Next time you hear that, can you let me know? I haven't heard of any
issues since 3.4 IIRC.

--Andy

>
> So yes, this does make it all better.
>
> -hpa
>
>

--
Andy Lutomirski
AMA Capital Management, LLC