Date: Thu, 10 Jan 2002 09:31:24 -0700 From: Nate Williams <nate@yogotech.com> To: Bruce Evans <bde@zeta.org.au> Cc: Nate Williams <nate@yogotech.com>, Daniel Eischen <eischen@pcnet1.pcnet.com>, Dan Eischen <eischen@vigrid.com>, Peter Wemm <peter@wemm.org>, Archie Cobbs <archie@dellroad.org>, Alfred Perlstein <bright@mu.org>, <arch@FreeBSD.ORG> Subject: Re: Request for review: getcontext, setcontext, etc Message-ID: <15421.49628.630456.688977@caddis.yogotech.com> In-Reply-To: <20020110141330.M10745-100000@gamplex.bde.org> References: <15420.58839.954146.527043@caddis.yogotech.com> <20020110141330.M10745-100000@gamplex.bde.org>
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> > > > Assuming I used followed things up with 'fnsave', will the exception be > > > > triggered by a frstor, and thus the exception will be correctly reported > > > > by the thread triggering the exception? > > > > > > Only on broken systems. > > > > Why is reporting a SIGFPE considered broken? This is a valid exception, > > and it should be reported. > > Because the SIGFPE is for the broken context-switching code and not for > the program. Ok, let's try again. How can I make sure that a SIGFPE that occur due to a FPU operation is properly reported using fsave/frestor? (I've asked this before, but apparently not in a way that made sense.) Here's a snippet again. fldz fld1 fdiv %st,%st(1) # 1.0 / 0.0 (should cause a SIGFPE exception) fsave #fooLocation // Mumble mumble other code to choose a new thread frstor #barLocation Questions * Would 'thread 1' get a SIGFPE before the fsave instruction? (Yes, No, maybe) * If above is maybe, would it get the SIGFPE after a frstor #fooLocation? * If answer to both is NO, how do I make sure that the context of the fdiv receives a SIGFPE? Can I use a different operation? Can I add instructions to cause this to work correctly? > > > See Appendix C of the Intel MMX manual (1997 version at least) for more > > > details. > > > > I don't have the MXX manual, just the x86/87 programming manuals for x86 > > (X <= 3). > > Same here, except I also have the 486 manual and a web browser :-). Ahh, these manuals are online. Thanks for the URL. :) Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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