linux-kernel - Re: [PATCH v2] x86: Remove compat vdso support

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Message-ID: <CALCETrXbgHMPU7in4ThRWyRTw4EN4W9vYOh1RKAiBLFTauxrRQ@mail.gmail.com>
Date:	Wed, 12 Mar 2014 16:43:34 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Stefani Seibold <stefani@...bold.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Dave Jones <davej@...hat.com>,
	Martin Runge <Martin.Runge@...de-schwarz.com>,
	Andreas Brief <Andreas.Brief@...de-schwarz.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2] x86: Remove compat vdso support

On Wed, Mar 12, 2014 at 4:06 PM, H. Peter Anvin <hpa@...ux.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@...ux-foundation.org> wrote:
>>> On Wed, Mar 12, 2014 at 2:37 PM, H. Peter Anvin <hpa@...ux.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
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