linux-kernel - Re: console font limits

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]

Date:	Thu, 3 May 2007 20:17:48 -0400
From:	Kyle Moffett <mrmacman_g4@....com>
To:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Albert Cahalan <acahalan@...il.com>,
	"Antonino A. Daplas" <adaplas@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>, aeb@....nl
Subject: Re: console font limits

On May 03, 2007, at 16:16:51, Jan Engelhardt wrote:
> On May 3 2007 13:15, H. Peter Anvin wrote:
>> Jan Engelhardt wrote:
>>>
>>>> Put people didn't like that, and disabled text output when the  
>>>> console is in KD_GRAPHICS mode...
>>>
>>> at the cost of not getting the kernel oops, heh.
>>
>> I thought the reason we didn't display text in KD_GRAPHICS mode  
>> was that KD_GRAPHICS might mean "in a completely different mode  
>> that only userspace knows about."
>
> Hrm. Maybe we need a distinction into KD_KGRAPHICS and KD_UGRAPHICS  
> then.

Actually I think the real problem was that "KD_GRAPHICS" got  
overloaded to mean "some userspace program is probably poking at the  
GPU in very direct ways possibly including /dev/mem".  As such it  
really isn't safe at all for the kernel to write stuff to the screen  
in that situation; you could turn a panic()+reboot-after-30-secs into  
an unrecoverable hard PCI bus lockup.  IIRC there were at least a  
couple chipsets which had that problem with X.  If we can implement  
enough APIs for X to do all of its stuff from userspace without iopl 
() or /dev/mem then we could probably bring back the option for  
dumping oopses to screen in KD_GRAPHICS mode, but otherwise it'll  
just cause more headaches.

Cheers,
Kyle Moffett

-
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/