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From: "H. Peter Anvin" <>
To: Andy Lutomirski <>
Cc: Cyrill Gorcunov <>, X86 ML <>,
	Andrew Morton <>,
	Sasha Levin <>,
	"" <>,
	Dave Jones <>,
	LKML <>,
	Pavel Emelyanov <>
Subject: Re: [PATCH 3/4] x86,mm: Improve _install_special_mapping and fix x86 vdso naming
Date: Tue, 20 May 2014 11:27:50 -0700
Message-ID: <> (raw)
In-Reply-To: <>

On 05/20/2014 11:24 AM, Andy Lutomirski wrote:
> On Tue, May 20, 2014 at 11:18 AM, H. Peter Anvin <> wrote:
>> On 05/20/2014 11:01 AM, Cyrill Gorcunov wrote:
>>>> This patch should fix this issue, at least.  If there's still a way to
>>>> get a native vdso that doesn't say "[vdso]", please let me know/
>>> Yes, having a native procfs way to detect vdso is much preferred!
>> Is there any path by which we can end up with [vdso] without a leading
>> slash in /proc/self/maps?  Otherwise, why is that not "native"?
> Dunno.  But before this patch the reverse was possible: we can end up
> with a vdso that doesn't say [vdso].

That's a bug, which is being fixed.  We can't go back in time and create
new interfaces on old kernels.

>>>>>   The situation get worse when task was dumped on one kernel and
>>>>> then restored on another kernel where vdso content is different
>>>>> from one save in image -- is such case as I mentioned we need
>>>>> that named vdso proxy which redirect calls to vdso of the system
>>>>> where task is restoring. And when such "restored" task get checkpointed
>>>>> second time we don't dump new living vdso but save only old vdso
>>>>> proxy on disk (detecting it is a different story, in short we
>>>>> inject a unique mark into elf header).
>>>> Yuck.  But I don't know whether the kernel can help much here.
>>> Some prctl which would tell kernel to put vdso at specifed address.
>>> We can live without it for now so not a big deal (yet ;)
>> mremap() will do this for you.
> Except that it's buggy: it doesn't change mm->context.vdso.  For
> 64-bit tasks, the only consumer outside exec was arch_vma_name, and
> this patch removes even that.  For 32-bit tasks, though, it's needed
> for signal delivery.

Again, a bug, let's fix it rather than saying we need a new interface.


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Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-05-19 22:58 [PATCH 0/4] x86,mm: vdso fixes for an OOPS and /proc/PID/maps Andy Lutomirski
2014-05-19 22:58 ` [PATCH 1/4] x86,vdso: Fix an OOPS accessing the hpet mapping w/o an hpet Andy Lutomirski
2014-05-19 22:58 ` [PATCH 2/4] mm,fs: Add vm_ops->name as an alternative to arch_vma_name Andy Lutomirski
2014-05-19 22:58 ` [PATCH 3/4] x86,mm: Improve _install_special_mapping and fix x86 vdso naming Andy Lutomirski
2014-05-20 17:21   ` Cyrill Gorcunov
2014-05-20 17:24     ` Andy Lutomirski
2014-05-20 17:47       ` Cyrill Gorcunov
2014-05-20 17:52         ` Andy Lutomirski
2014-05-20 18:01           ` Cyrill Gorcunov
2014-05-20 18:18             ` H. Peter Anvin
2014-05-20 18:24               ` Andy Lutomirski
2014-05-20 18:27                 ` H. Peter Anvin [this message]
2014-05-20 18:38                   ` Andy Lutomirski
2014-05-20 18:39                 ` Cyrill Gorcunov
2014-05-20 18:37   ` H. Peter Anvin
2014-05-19 22:58 ` [PATCH 4/4] x86,mm: Replace arch_vma_name with vm_ops->name for vsyscalls Andy Lutomirski

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