Date: Fri, 9 Jul 2004 10:54:54 -0400 (EDT) From: Robert Watson <rwatson@FreeBSD.org> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: current@FreeBSD.org Subject: Re: ethercons updated for -CURRENT Message-ID: <Pine.NEB.3.96L.1040709105253.60816L-100000@fledge.watson.org> In-Reply-To: <16622.45106.992924.734398@grasshopper.cs.duke.edu>
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On Fri, 9 Jul 2004, Andrew Gallatin wrote: > For what its worth, Darwin has this for their KDP ethernet debugging. > To receive something, the debugger provides a buffer and specifies a > timeout. The driver keeps the same memory mapped for DMA, and just > copies into the provided void *buffer. There is also a polled transmit > routine, where the driver does not return until the outgoing packet has > been DMA'ed. In both cases, the driver is not allowed to allocate > memory, or do anything which can block. > > One thing that's always concerned me is how do they ensure the driver is > not in the middle of a "normal" transmit or recv when the debugger is > entered.. I have a lot of concerns about ensuring likely correctness of the model, including reentrancy, consistent hardware state, packets destined for the debugger wandering around the stack, etc. It strikes me that it's likely the network kernel debugging pieces work most of the time, and likely work especially well if you're not debugging the network stack :-). My guess would be that over time, Apple will start preferring (if they don't already) firewire debugging simply because it will become available earlier, work in more sticky situations, etc. Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Principal Research Scientist, McAfee Research
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