From owner-freebsd-alpha Tue Jul 9 15:42:25 2002 Delivered-To: freebsd-alpha@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 794B137B400; Tue, 9 Jul 2002 15:42:22 -0700 (PDT) Received: from canning.wemm.org (canning.wemm.org [192.203.228.65]) by mx1.FreeBSD.org (Postfix) with ESMTP id 3365043E4A; Tue, 9 Jul 2002 15:42:22 -0700 (PDT) (envelope-from peter@wemm.org) Received: from fw.wemm.org (canning.wemm.org [192.203.228.65]) by canning.wemm.org (Postfix) with ESMTP id 086CA2A7D6; Tue, 9 Jul 2002 15:42:22 -0700 (PDT) (envelope-from peter@wemm.org) Received: from overcee.wemm.org (overcee.wemm.org [10.0.0.3]) by fw.wemm.org (Postfix) with ESMTP id A1B444C27C; Tue, 9 Jul 2002 15:42:21 -0700 (PDT) (envelope-from peter@wemm.org) Received: from wemm.org (localhost [127.0.0.1]) by overcee.wemm.org (Postfix) with ESMTP id E98DB3808; Tue, 9 Jul 2002 15:42:21 -0700 (PDT) (envelope-from peter@wemm.org) X-Mailer: exmh version 2.5 07/13/2001 with nmh-1.0.4 To: John Baldwin Cc: alpha@FreeBSD.org Subject: Re: uac flags in the kernel In-Reply-To: Date: Tue, 09 Jul 2002 15:42:21 -0700 From: Peter Wemm Message-Id: <20020709224221.E98DB3808@overcee.wemm.org> Sender: owner-freebsd-alpha@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org John Baldwin wrote: > Ok, I have a couple of questions about the uac (unaligned access check) > flags in the kernel. First, I think they should be a process-wide > property, so we need to move them out of td_md.md_flags and into a > p_md.md_flags or p_md.md_uac or some such. Secondly, why do the > sysarch() syscalls get and set the uac of the parent process? uac works on the parent, because it would be a bit silly to work on itself since it is just about to exit. Actually, I'd like it to behave more like env(1)/ktrace etc. uac ... - operates on parent uac -p nnn ... - operates on process nnn uac ... /bin/sh - execs /bin/sh with specified uac settings. Secondly.. At least one arch (ia64) has part of this as application thread context. ie: ia64 apps can freely toggle alignment the AC bit on and off without making a sysarch() call. Note that the cpu may not allow AC=off to go unpunished so the kernel may have to do a fixup anyway. I thought you'd just love to know about that wrinkle. :-) It would be nice to have a uac that worked similarly across all platforms. I'd like to be able to turn it on and off for x86 as well. Cheers, -Peter -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com "All of this is for nothing if we don't go to the stars" - JMS/B5 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-alpha" in the body of the message