Dailydave mailing list archives
Re: luckily, there are no dumb questions (dan () geer org)
From: Philippe Langlois <philippelanglois () free fr>
Date: Fri, 8 Jun 2007 12:58:00 +0200
If I recall well, LSE/OS used all four rings, and ring 1 and 2 can be used to run drivers, and then ring 3 for users. LSE/OS was described as a "nano kernel", and used a state machine hardware (using the hardware context switch). Quite interesting project :) Sources: http://sourceforge.net/projects/lseos/ Docs & presentations: http://lseos.sourceforge.net/ Best, Philippe. On 08 Jun 2007, at 00:59, johnny cache wrote:
Wouldn't a better question be: "how is it that -no- mainstream OS uses more than 2 rings on x86?" Or "How come nobody uses x86 segmentation(by default)?" I think the simple answer is that most operating system developers view these features as baggage that have no analogy on other platforms and therefore are to be avoided. Segmentation (by-and-large) got the axe on 64-bit x86 chips. Who's to say 4-rings wasn't next on the chopping block? If the features have been there and haven't been used in over a decade, its probably not a good idea to dust them off and start depending on them now. Writing an OS that made effective use of all 4 rings would not only be difficult, forward compatability on more "sane" CPUs is almost certain not to happen. Just my 2c. -jcDate: Thu, 07 Jun 2007 15:30:58 -0400 From: dan () geer org Subject: [Dailydave] luckily, there are no dumb questions Luckily, there are no dumb questions or this would likely be one. How is it so that MS Windows uses only Rings 0 & 3? An engineering answer, a marketing answer, and/or an historical answer would be welcome. Don't know why I never thought to ask before, but I'm asking now. (And if I'm really wrong, please tell me what uses 1|2.)_______________________________________________ Dailydave mailing list Dailydave () lists immunitysec com http://lists.immunitysec.com/mailman/listinfo/dailydave
_______________________________________________ Dailydave mailing list Dailydave () lists immunitysec com http://lists.immunitysec.com/mailman/listinfo/dailydave
Current thread:
- Re: luckily, there are no dumb questions (dan () geer org) johnny cache (Jun 07)
- Re: luckily, there are no dumb questions (dan () geer org) Ed Schaller (Jun 08)
- Re: luckily, there are no dumb questions (dan () geer org) Philippe Langlois (Jun 08)