linux-kernel - Re: [git pull] drm: previous pull req + 1.

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: <1245719079.4017.25.camel@pasglop>
Date:	Tue, 23 Jun 2009 11:04:39 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Thomas Hellström <thomas@...pmail.org>,
	Dave Airlie <airlied@...ux.ie>,
	Alex Deucher <alexdeucher@...il.com>,
	Andrew Lutomirski <luto@....edu>, dri-devel@...ts.sf.net,
	Jerome Glisse <jglisse@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [git pull] drm: previous pull req + 1.

On Mon, 2009-06-22 at 17:24 -0700, Linus Torvalds wrote:
> 
> On Tue, 23 Jun 2009, Benjamin Herrenschmidt wrote:
> > 
> > As far as I can remember, all fbdev operations are done under the
> > console semaphore.
> 
> Yeah, and some of them are horribly broken (ie copying data from user 
> space while doing it - causing horrible things like VC switching latencies 
> and invisible printk's if an oops happens during the op).
> 
> Or maybe that got fixed. 

Well, it does rely on userspace behaving.. ie, no accel ops are done by
the kernel in KD_GRAPHICS and userspace is -supposed- to switch to
KD_GRAPHICS before touching the fb.

In fact, nowdays, we do have the infrastructure to be smart and enforce
that. IE. Instead of using a boring remap_page_ranges() in fb_mmap() we
could use a fault handler. When in KD_TEXT, we fail them, when in
KD_GRAPHICS, we service them, and we unmap_mapping_range() when
switching. Something like that...

Dunno how that interacts with the new DRM thingy though.

Cheers,
Ben.

--
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/