[Crash-utility] [PATCH 0/5] crash: Small bundle of fixes for Xen

[Dave Anderson]

----- Original Message -----
> On Thu, Jul 12, 2012 at 03:47:57PM -0400, Dave Anderson wrote:
> >
> >
> > ----- Original Message -----
> > >
> > >
> > > ----- Original Message -----
> > > >
> > > >
> > > > ----- Original Message -----
> > > > > On Thu, Jul 05, 2012 at 05:29:50PM +0200, Daniel Kiper wrote:
> > > > > > On Thu, Jul 05, 2012 at 11:15:29AM -0400, Dave Anderson
> > > > > > wrote:
> > > > > > >
> > > > > > >
> > > > > > > ----- Original Message -----
> > > > > > > > Hi,
> > > > > > > >
> > > > > > > > It looks that Xen support for crash have not been
> > > > > > > > maintained
> > > > > > > > since 2009. I am trying to fix this. Here it is small
> > > > > > > > bundle of fixes:
> > > > > > > >   - xen: Always calculate max_cpus value,
> > > > > > > >   - xen: Read only crash notes for onlined CPUs,
> > > > > > > >   - x86/xen: Read variables from dynamically allocated
> > > > > > > >   per_cpu data,
> > > > > > > >   - xen: Get idle data from alternative source,
> > > > > > > >   - xen: Read data correctly from dynamically allocated
> > > > > > > >   console ring too.
> > > > > > > >
> > > > > > > > Daniel
> > > > > > >
> > > > > > > Daniel,
> > > > > > >
> > > > > > > Can you absolutely confirm that these changes are all
> > > > > > > backwards-compatible?
> > > > > >
> > > > > > I have not done tests with older versions of Xen. However,
> > > > > > I made all patches with backward compatibility in mind.
> > > > > > Anyway,
> > > > > > If you wish I could do tests with let's say Xen Ver. 3.4
> > > > > > and Xen Linux Kernel Ver. 2.6.18 at least.
> > > > >
> > > > > I think Dave is worried about it breaking with the version
> > > > > that is bundled
> > > > > with RHEL5U8?
> > > >
> > > > Correct...
> > > >
> > > > Dave
> > > >
> > >
> > > And as it turns out, it does break RHEL5 xen, at least the
> > > changes
> > > you made for the log command:
> > >
> > >   crash> log
> > >   log: invalid kernel virtual address: 616e69625f64616f  type:
> > >   "conring contents"
> > >   crash>
> > >
> >
> > Daniel,
> >
> > Your patch breaks the RHEL5 xen hypervisor log command because "conring" used
> > to be declared as a statically-sized array:
> >
> >   crash> whatis conring
> >   char conring[16384];
> >   crash>
> >
> > It appears from your patch that "conring" is now declared as a pointer,
> > given that your patch does this:
> >
> > --- crash-6.0.8.orig/xen_hyper_command.c        2012-06-29
> > 16:59:18.000000000 +0200
> > +++ crash-6.0.8/xen_hyper_command.c     2012-07-05
> > 16:22:35.000000000 +0200
> > @@ -590,24 +590,31 @@ xen_hyper_dump_log(void)
> >         ulong conring;
> >         char *buf;
> >         char last;
> > +       uint32_t conring_size;
> >
> > -       conring = symbol_value("conring");
> > +       get_symbol_data("conring", sizeof(ulong), &conring);
> >         get_symbol_data("conringc", sizeof(uint), &conringc);
> >         get_symbol_data("conringp", sizeof(uint), &conringp);
> > ...
> >
> > If I change your patch such that the end result looks like this:
> >
> >         if (get_symbol_type("conring", NULL, NULL) ==
> >         TYPE_CODE_ARRAY)
> >                 conring = symbol_value("conring");
> >         else
> >                 get_symbol_data("conring", sizeof(ulong),
> >                 &conring);
> >
> > it works for RHEL5 xen hypervisor.
> >
> > Does that work for you?
> 
> Thanks. It works. I though that there is an issue with conring symbol too.
> Have you done other tests on RHEL5?

I just did some basic commands, and I didn't see any other problems besides
the log/conring issue.  But I don't really have a good test suite for the Xen
hypervisor options.  And honestly, I've never even seen a "real" hypervisor 
crash dump, I just have a few forced samples.  If you'd like, I can give you a
pointer to a really early RHEL5.2-era (2.6.18-89.el5) xen-syms/vmcore pair
that you can use to verify your changes on if you don't have any dumps of
that era available.

> 
> I discoverd additional crash issue with Xen core dumps. I am working
> on fix for that. I would like to add relevant patch for next release
> of this bundle of patches. I am going to do all tests for new release
> (probably next week). Is it OK for you?
> 
> Daniel

No problem, I'll just wait for your v2 set.

Thanks,
  Dave