Newsgroups: comp.arch
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Is the Intel memory model safe from NO-ONE ?!?
Message-ID: <1988May12.162207.16764@utzoo.uucp>
Organization: U of Toronto Zoology
References: <353@cf-cm.UUCP> <3095@edm.UUCP>, <20618@think.UUCP>
Date: Thu, 12 May 88 16:22:07 GMT

> ... it traps into SUPERVISOR mode, even though the program
> that executed the divide instruction was running in USER mode.  Why
> should a zero-divide need to be handled by the protected kernel,
> rather than simply trapping to a user handler?

Probably because practically every machine in existence routes *all*
traps and interrupts to the kernel, which can pass them on to the user
if it pleases.  I know of no machine, offhand, whose hardware has any
notion of a "user handler".
-- 
NASA is to spaceflight as            |  Henry Spencer @ U of Toronto Zoology
the Post Office is to mail.          | {ihnp4,decvax,uunet!mnetor}!utzoo!henry