From owner-freebsd-alpha Tue Dec 18 12:10: 5 2001 Delivered-To: freebsd-alpha@freebsd.org Received: from k6.locore.ca (k6.locore.ca [198.96.117.170]) by hub.freebsd.org (Postfix) with ESMTP id DDA4F37B405; Tue, 18 Dec 2001 12:10:01 -0800 (PST) Received: (from jake@localhost) by k6.locore.ca (8.11.6/8.11.6) id fBIKD8851812; Tue, 18 Dec 2001 15:13:08 -0500 (EST) (envelope-from jake) Date: Tue, 18 Dec 2001 15:13:08 -0500 From: Jake Burkholder To: Andrew Gallatin Cc: John Baldwin , alpha@FreeBSD.ORG Subject: Re: mdproc flags in KSE Message-ID: <20011218151308.M39205@locore.ca> References: <15391.37056.22312.225550@grasshopper.cs.duke.edu> <20011218145413.L39205@locore.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <20011218145413.L39205@locore.ca>; from jake@locore.ca on Tue, Dec 18, 2001 at 02:54:13PM -0500 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 > > > Also, what are the single stepping fields used for exactly (details, not just > > > "to implement single stepping :)"). Is the osf_sigtramp just setup once for > > > > Single-stepping -- no clue. > > My take on this is that alpha doesn't have a hardware single stepping > flag like i386 (correct me if I'm wrong). So the only way to implement > single stepping is to replace the next instruction to be executed with > a breakpoint each time. You need 2 because of branches, both paths > need to have a breakpoint poked in. This is inherently evil. > > Sparc64 needs the same kind of support. > > Where this goes depends a lot on how debugging works in multithreaded > processes. ie, do we allow single stepping 2 threads from the same > process simultaneously. > To answer your question, they're used to hold the opcodes and addresses of the instructions that were replaced with breakpoints, so they can be put back once the breakpoints have done their job. Jake To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-alpha" in the body of the message