linux-kernel - Re: [x86, vdso] BUG: unable to handle kernel paging request at d34bd000

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Message-ID: <531DFD55.1070000@linux.intel.com>
Date:	Mon, 10 Mar 2014 10:58:45 -0700
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Andy Lutomirski <luto@...capital.net>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Stefani Seibold <stefani@...bold.net>,
	Andreas Brief <Andreas.Brief@...de-schwarz.com>,
	Martin Runge <Martin.Runge@...de-schwarz.com>
Subject: Re: [x86, vdso] BUG: unable to handle kernel paging request at d34bd000

On 03/10/2014 10:52 AM, Andy Lutomirski wrote:
>>
>> Hint: where is your RIP?  Where is the RIP of other processes?
>>
> 
> Whoa there, I'm not suggesting anything nearly that crazy :)
> 
> I'm suggesting changing out the vvar page *for that process*, which is
> not executable.  The actual vdso code already supports this -- from
> userspace's point of view it's the same thing as 'echo acpi_pm >
> /sys/devices/system/clocksource/clocksource0/current_clocksource',
> except that if the actual clocksource is HPET, the hpet page will be
> switched out (presumably with a zero page) while being read.
> 
> Other processes are totally irrelevant, unless they share the same
> struct mm.  (This is why the vvar page can't be in the fixmap for this
> to work.)
> 

I meant "threads" not "processes"...

	-hpa


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