Re: [Kgdb-bugreport] [PATCH] Kill kgdb_serial
From: George Anzinger
Date: Thu Mar 04 2004 - 17:04:03 EST
Amit S. Kale wrote:
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 shite, 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.
There was some talk along these lines at one point, I don't think anything came
of it. We would like it to be the very first, not just one of the first.
I think modifying the kernel to support this for kgdb is more like the tail
wagging the dog :)
--
George Anzinger george@xxxxxxxxxx
High-res-timers: http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml
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