linux-kernel - Re: [PATCH 3/3] x86-64: Rework vsyscall emulation and add vsyscall= parameter

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Message-ID: <4b8d6929-6163-4e25-933c-c875a1857f3a@email.android.com>
Date:	Wed, 10 Aug 2011 17:20:58 -0500
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andrew Lutomirski <luto@....edu>
CC:	x86@...nel.org, Andi Kleen <andi@...stfloor.org>,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	lueckintel@...oo.com, kimwooyoung@...il.com,
	Ingo Molnar <mingo@...e.hu>, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH 3/3] x86-64: Rework vsyscall emulation and add vsyscall= parameter

Andrew Lutomirski <luto@....edu> wrote:

>On Wed, Aug 10, 2011 at 5:14 PM, H. Peter Anvin <hpa@...or.com> wrote:
>> Andrew Lutomirski <luto@....edu> wrote:
>>
>>>On Wed, Aug 10, 2011 at 1:21 PM, H. Peter Anvin <hpa@...or.com>
>wrote:
>>>> On 08/10/2011 10:15 AM, Andy Lutomirski wrote:
>>>>> There are three choices:
>>>>>
>>>>> vsyscall=native: Vsyscalls are native code that issues the
>>>>> corresponding syscalls.
>>>>>
>>>>> vsyscall=emulate (default): Vsyscalls are emulated by instruction
>>>>> fault traps, tested in the bad_area path.  The actual contents of
>>>>> the vsyscall page is the same as the vsyscall=native case except
>>>>> that it's marked NX.  This way programs that make assumptions
>about
>>>>> what the code in the page does will not be confused when they read
>>>>> that code.
>>>>>
>>>>> vsyscall=none: Trying to execute a vsyscall will segfault.
>>>>>
>>>>> Signed-off-by: Andy Lutomirski <luto@....edu>
>>>>
>>>> Hi Andy,
>>>>
>>>> This patch doesn't apply.  What is your baseline for this patch?
>>>
>>>My baseline was a commit that probably only lives in my tree, but the
>>>patches should apply cleanly on top of
>>>c149a665ac488e0dac22a42287f45ad1bda06ff1, which is the current
>>>tip/x86/vdso.
>>>
>>>--Andy
>>
>> Please rebase your patch on the current -linus since it appears to
>have changed since x86/vdso was merged.
>>
>
>Can you double-check?  I think it's the other way around: x86/vdso has
>fixes that should be pushed to Linus.
>
>$ git log tip/x86/vdso ^origin/master --oneline
>c149a66 x86-64: Add vsyscall:emulate_vsyscall trace event
>318f5a2 x86-64: Add user_64bit_mode paravirt op
>5d5791a x86-64, xen: Enable the vvar mapping
>f670bb7 x86-64: Work around gold bug 13023
>9c40818 x86-64: Move the "user" vsyscall segment out of the data
>segment.
>1bdfac1 x86-64: Pad vDSO to a page boundary
>17b0436 Merge commit 'v3.0' into x86/vdso
>
>--Andy

You're right, although coupling it makes the testing harder.
-- 
Sent from my mobile phone. Please excuse my brevity and lack of formatting.
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