Date: Tue, 18 Dec 2001 15:13:08 -0500 From: Jake Burkholder <jake@locore.ca> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: John Baldwin <jhb@FreeBSD.ORG>, alpha@FreeBSD.ORG Subject: Re: mdproc flags in KSE Message-ID: <20011218151308.M39205@locore.ca> In-Reply-To: <20011218145413.L39205@locore.ca>; from jake@locore.ca on Tue, Dec 18, 2001 at 02:54:13PM -0500 References: <XFMail.011218100048.jhb@FreeBSD.org> <15391.37056.22312.225550@grasshopper.cs.duke.edu> <20011218145413.L39205@locore.ca>
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> > > 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
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