Date: Tue, 24 Nov 1998 09:35:37 +1030 From: Greg Lehey <grog@lemis.com> To: Joel Ray Holveck <joelh@gnu.org> Cc: SysAdmin <sa@ns.online.samara.ru>, freebsd-hackers@FreeBSD.ORG Subject: Re: breakpoint on i/o in kernel Message-ID: <19981124093537.R430@freebie.lemis.com> In-Reply-To: <86iug6mcnq.fsf@detlev.UUCP>; from Joel Ray Holveck on Mon, Nov 23, 1998 at 01:28:41PM -0600 References: <AAnyMMsCYR@ns.online.samara.ru> <19981123205619.Q430@freebie.lemis.com> <86iug6mcnq.fsf@detlev.UUCP>
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On Monday, 23 November 1998 at 13:28:41 -0600, Joel Ray Holveck wrote: >>> I need breakpoint on i/o in kernel >>> How doing this in ddb, or exist another way ? >> Well, the syntax is: >> b <address> >> <address> can be a hex value or an expression, possibly symbolic. Are >> you asking which address to choose? Then you need to say what you >> want to do. > > I think he's asking for an I/O breakpoint, not an address breakpoint; > eg, break whenever a particular I/O port is accessed. Ah, that could be. > I don't know what CPUs have instrumentation for this. All i386 architectures, in varying degrees. > To the best of my knowledge, neither DDB nor GDB have any hooks to > handle this. Correct. > (It might theoretically be possible with GDB using a semicomplex > series of isteps and tests, but it would slow down your system > possibly hundredfold.) The correct thing to do would be to implement I/O (and memory access) breakpoints, not kludge it. I look at it once, and the code turned my stomach. I once wrote a kernel debugger (for BSD/386) which implemented these features. I've been meaning to do it ever since for FreeBSD, but I still haven't got round to it. > I generally recommend another method of debugging than I/O > breakpoints. That's a workaround, not a solution. I/O breakpoints are really useful. Greg -- See complete headers for address, home page and phone numbers finger grog@lemis.com for PGP public key To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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