linux-kernel - Re: reboot via bios on X86

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4F832557.6070109@meetinghouse.net>
Date:	Mon, 09 Apr 2012 14:07:19 -0400
From:	Miles Fidelman <mfidelman@...tinghouse.net>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Matthew Garrett <mjg@...hat.com>, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
	peter.chubb@...ta.com.au, michael.d.labriola@...il.com
Subject: Re: reboot via bios on X86_64?

H. Peter Anvin wrote:
> On 04/09/2012 10:26 AM, Miles Fidelman wrote:
>> Thanks for the quick response.
>>
>> Matthew Garrett wrote:
>>> On Mon, Apr 09, 2012 at 11:39:32AM -0400, Miles Fidelman wrote:
>>>
>>>> 1. What's the logic behind this?  Why not enable a bios reboot for 64bit
>>>> kernels?  Is there any reason why the machine_real_restart code wouldn't
>>>> work just as well in 64bit mode?  Anybody know the history?
>>> The bios reboot code requires you to reprogram the CPU to real mode. I
>>> don't think there's any fundamental reason you can't do that from 64-bit
>>> mode, but nobody's ever written that code.
>> That would explain it.  I guess there's a little bit of trickiness
>> involved in setting things up before
>> switching to real mode.
>>
> Actually this code already exists; the difference is that we have to
> return to 32-bit mode first.
ahhh.... ain't things fun when one gets really close to the hardware



-- 
In theory, there is no difference between theory and practice.
In practice, there is.   .... Yogi Berra


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/