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

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Date:	Wed, 12 Mar 2014 16:06:45 -0700
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	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 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.

So yes, this does make it all better.

	-hpa


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