[Xen-devel] Re: Compile error in KDB branch when debug=y.

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

Hi John,

Thanks for the patch.
Actually, I noticed it last week when I refreshed the tree to latest and
debug was turned on by default. There are problems running kdb with
debug=y, like:

(XEN) Xen BUG at spinlock.c:23
*** kdb (Fatal Error on cpu:1 vec:6 Invalid Opcode):
ffff828c8011b865: check_lock+3d                  ud2
[1]xkdb>
[1]xkdb> f
(XEN)    [<ffff828c8011b865>] check_lock+0x3d/0x4e
(XEN)    [<ffff828c8011b9eb>] _spin_lock+0x11/0x24
(XEN)    [<ffff828c8015bd5c>] do_settime+0x26/0x87
(XEN)    [<ffff828c8015c1f5>] kdb_time_resume+0x90/0x121
(XEN)    [<ffff828c801d94d4>] kdb_end_session+0x8f/0x298
(XEN)    [<ffff828c801d9e3b>] kdbmain+0x75e/0x867
(XEN)    [<ffff828c801d9fa2>] kdb_keyboard+0x11/0x13
(XEN)    [<ffff828c80128e99>] serial_rx+0x2f/0xd8
(XEN)    [<ffff828c8012a2e7>] serial_rx_interrupt+0xa9/0xbf


So I'd recommend turning it off, even tho I've fixed the build break.  Since
I always have debug=n (with frame_pointer=yes) when I debug,  I've not
looked at any of these issues.

BTW, I've refreshed the tree to latest, so please check it out:
http://xenbits.xensource.com/ext/debuggers.hg

Thanks,
Mukesh


Emre Can Sezer wrote:
> Hi Mukesh,
>
> Got a compile time type mismatch error from debug.c:70 when compiling
> with debug=y.  Below is the single line patch to fix it.
>
> --- xen-unstable/xen/arch/x86/debug.c    2009-02-19 14:27:02.000000000
> -0500
> +++ xen-debug/xen/arch/x86/debug.c    2009-02-18 17:26:09.000000000 -0500
> @@ -67,7 +67,7 @@
>     }
>
> #if XEN_SUBVERSION >= 2             /* xen >= 3.2.x */
> -        mfn = gfn_to_mfn(dp, gfn, &gfntype);
> +        mfn = mfn_x(gfn_to_mfn(dp, gfn, &gfntype));
>     if (p2m_is_readonly(gfntype) && toaddr) {
>         DBGP2("kdb:p2m_is_readonly: gfntype:%x\n", gfntype);
>         return INVALID_MFN;
>
>
> Cheers,
>
> John
>
>
>
> Mukesh Rathor wrote:
>>
>> Hi,
>>
>>  kdb: to debug xen hypervisor, could also debug guests
>>  gdbsx: to debug PV/HVM linux guests
>>
>> The tree is : http://xenbits.xensource.com/ext/debuggers.hg
>>
>> See README-dbg. You'll need to setup serial access for kdb.
>>
>> Thanks,
>> Mukesh
>>
>> >
>> > Hi Dan,
>> >
>> > I'm currently using your version of ssplitd as it is.  I haven't tried
>> > kdb.  For some reason I thought that was for debugging guest domains.
>> > I'll look into it.  As for resurrecting the gdbstub, I'm *NOT* familiar
>> > enough
>> > with it to try it myself. I do have a few people here who might be
>> though.
>> > I'll post something if we get it working.
>> >
>> > Thanks,
>> >
>> > John
>> >
>> > Dan Doucette wrote:
>> >> Hi John,
>> >>
>> >> The patches I submitted quickly fell out of sync with the 3.2 unstable
>> >> branch at the time.  I found a month or so later they stopped working,
>> >> and I didnt have the time to keep them up to date.
>> >> For Xen debugging, have you tried the kdb branch maintained my Mukesh
>> >> Rathor (Oracle)?  I used this a few months ago and it seemed to work.
>> >> The branch is off the mainline, however.  Its usage is documented in
>> >> the xen wiki pages, I believe.
>> >>
>> >> If you would prefer to use gdb, the functionality should be easy to
>> >> resurrect.  There really wasnt much to it.
>> >> I would recommend using my serial port splitter (ssplitd.c), which I
>> >> found easier to use and was complete in its implementation.  I
>> >> submitted all the changes in proper patch form after the posting you
>> >> referenced above, if you are interested.
>> >>
>> >> Dan.
>> >>
>> >>
>> >>
>> >>
>> >> On Wed, Jan 28, 2009 at 10:53 AM, Emre Can Sezer <ecsezer@xxxxxxxx
>> >> <mailto:ecsezer@xxxxxxxx>> wrote:
>> >>
>> >>     I'm trying to debug Xen remotely using serial port.  I followed
>> >>     the instructions on the following post made in this xen-devel
>> list:
>> >>
>> http://lists.xensource.com/archives/html/xen-devel/2007-12/msg00678.html
>> >>
>> >>     I was able to connect gdb but I ran into a problem where even
>> >>     after I clear all the breakpoints, execution traps into gdb with
>> >>     SIGTRAP at restore_all_xen().  This only happens if I set a
>> >>     breakpoint and then try to continue after hitting the break point.
>> >>      If I simply connect gdb but continue without setting any
>> >>     breakpoints, everything is OK.
>> >>
>> >>     The post mentions some stability issues and I haven't seen any
>> >>     follow ups.  Is this still a viable debugging method?  Or is there
>> >>     some other method I should try?
>> >>
>> >>     Thanks in advance,
>> >>
>> >>     John
>> >>
>> >>
>> >>
>> >>
>> >>     _______________________________________________
>> >>     Xen-devel mailing list
>> >>     Xen-devel@xxxxxxxxxxxxxxxxxxx
>> <mailto:Xen-devel@xxxxxxxxxxxxxxxxxxx>
>> >>     http://lists.xensource.com/xen-devel

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