Date: Tue, 09 Jul 2002 15:42:21 -0700 From: Peter Wemm <peter@wemm.org> To: John Baldwin <jhb@FreeBSD.org> Cc: alpha@FreeBSD.org Subject: Re: uac flags in the kernel Message-ID: <20020709224221.E98DB3808@overcee.wemm.org> In-Reply-To: <XFMail.20020709162339.jhb@FreeBSD.org>
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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
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