Date: Tue, 25 Sep 2001 18:34:55 +0200 From: Bernd Walter <ticso@mail.cicely.de> To: Bakul Shah <bakul@bitblocks.com> Cc: Bernd Walter <ticso@mail.cicely.de>, hackers@FreeBSD.ORG Subject: Re: VM Corruption - stumped, anyone have any ideas? Message-ID: <20010925183455.A29324@cicely20.cicely.de> In-Reply-To: <200109251610.MAA18919@warspite.cnchost.com>; from bakul@bitblocks.com on Tue, Sep 25, 2001 at 09:10:21AM -0700 References: <20010925095607.B27615@cicely20.cicely.de> <200109251610.MAA18919@warspite.cnchost.com>
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On Tue, Sep 25, 2001 at 09:10:21AM -0700, Bakul Shah wrote: > > > FWIW, in a Unix port we did I remember putting the user > > > struct *above* the kernel stack. The stack grew down so you > > > hit the red zone (the guard pages) without clobbering the > > > user struct. Since struct user _ended_ on a page boundary, > > > its size was needed at locore.s assembly time but that was a > > > small price to pay for the added safety. > > > > I don't think a guard page can help here, because the page fault > > handler needs a working stack. > > You can't continue if you run out of the stack in any case > but the issue is what happens when you run off the end of the > stack. In the FreeBSD case you trash the user struct and > discover this problem in a very indirect way and possibly > after trashing god-knows-what-else. No Doubt about it. But you missed my point completely. Nevertheless PHK already explained why it still help. -- B.Walter COSMO-Project http://www.cosmo-project.de ticso@cicely.de Usergroup info@cosmo-project.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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