Re: [Kgdb-bugreport] [PATCH] Kill kgdb_serial

From: Amit S. Kale (amitkale_at_emsyssoft.com)
Date: 03/04/04

  • Next message: Amit S. Kale: "Re: kgdb support in vanilla 2.6.2" 
    To: George Anzinger <george@mvista.com>, Tom Rini <trini@kernel.crashing.org>
Date:	Thu, 4 Mar 2004 10:31:00 +0530

    On Thursday 04 Mar 2004 6:04 am, George Anzinger wrote:
    > Tom Rini wrote:
    > > On Wed, Mar 03, 2004 at 04:51:06PM +0100, Pavel Machek wrote:
    > >>Hi!
    > >>
    > >>>>>More precisely:
    > >>>>>http://lkml.org/lkml/2004/2/11/224
    > >>>>
    > >>>>Well, that just says Andrew does not care too much. I think that
    > >>>>having both serial and ethernet support *is* good idea after all... I
    > >>>>have few machines here, some of them do not have serial, and some of
    > >>>>them do not have supported ethernet. It would be nice to use same
    > >>>>kernel on all of them. Also distribution wants to have "debugging
    > >>>>kernel", but does _not_ want to have 10 of them.
    > >>>
    > >>>But unless I'm missing something, supporting eth or 8250 at all times
    > >>>doesn't work right now anyhow, as eth if available will always take
    > >>> over.
    > >>
    > >>Well, that can be fixed. [Probably if kgdbeth= is not passed, ethernet
    > >>interface should not take over. So user selects which one should be
    > >>used by either passing kgdbeth or kgdb8250. That means that 8250
    > >>should not be initialized until user passes kgdb8250=... not sure how
    > >>you'll like that].
    > >
    > > At this point, I'm going to give up on killing kgdb_serial, and pass
    > > along some comments from David Woodhouse on IRC as well (I was talking
    > > about this issue, and the init/main.c change):
    > > (Tartarus == me, dwmw2 == David Woodhouse)
    > >
    > > <Tartarus> dwmw2, the problem is how do you deal with all of the
    > > possibilities of i/o (8250, kgdboe, or other serial) and do you allow
    > > for passing 'gdb' on the command line to result in kgdb not being dropped
    > > into? You can always break in later on of course
    > > <dwmw2> parse command line early for 'gdb=' argument specifying which
    > > i/o device to use. init kgdb core early. init each i/o device as early
    > > as possible for that i/o device. Start the selected i/o device as soon
    > > as it becomes available.
    > > <dwmw2> just like console could, if we looked for console= a little bit
    > > earlier. (forget all the earlyconsole ***, it's not necessary)
    > > <dwmw2> Tartarrus, do the __early_setup() thing to replace __setup() for
    > > selected args. We can use that for console= too.
    > > <dwmw2> since 'console=' on the command line _already_ remembers its
    > > arguments, and starts to use the offending device as soon as it gets
    > > registered with register_console().
    > > <Tartarus> dwmw2, __early_setup() ?
    > > <dwmw2> See __setup("gdb=", gdb_setup_func);
    > > <dwmw2> Replace with __early_setup(...)
    > > <Tartarus> where is __early_setup ?
    > > <dwmw2> before we normally parse the command line
    > > <dwmw2> in my head
    > >
    > > So perhaps someone can take these ideas and fix both problems... :)
    > > (I've got some other stuff I need to work on today).
    >
    > Well, __early_setup could mean the fist setup call and if so that would be
    > what we do in -mm. It is done by putting the code in the first module ld
    > sees, not nice, but it works.

    I would prefer something that modifies start_kernel itself, rather than
    depending on ld. It will split start_kernel command line parsing into early
    parse and late parse, but that's the price we have to pay to do special
    parsing of kgdb arguments. 

    -- 
Amit Kale
EmSysSoft (http://www.emsyssoft.com)
KGDB: Linux Kernel Source Level Debugger (http://kgdb.sourceforge.net)
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