Re: [Crash-utility] Wrong RSS field in ps
----- Original Message -----
On Tue, 4 Aug 2015 16:57:35 -0400 (EDT)
Dave Anderson <anderson(a)redhat.com> wrote:
>
>
> ----- Original Message -----
>
> > > Michael
> >
> > OK, so it would seem to be somewhere in the trail from enumerator_value()
> > into the gdb_command_funnel() via the GNU_GET_DATATYPE req->command in
> > datatype_info().
> >
> > I'm having a hard time provisioning an s390x machine internally at this
time.
> > When I get one, I'll see if the problem has been there all along.
> >
> > Dave
> >
>
> Michael,
>
> I finally got access to an s390x and I see the same thing. In fact it also
> happens on a RHEL6 2.6.32-based kernel, so it appears it's always been an
> issue. I'll look into it tomorrow.
Great, thanks!
Michael
The problem is in gdb-7.6/gdb/symtab.c, in the eval_enum() function that
gets created/added by the crash utility's gdb-7.6.patch:
static void
eval_enum(struct type *type, struct gnu_request *req)
{
register int i;
int len;
int lastval;
len = TYPE_NFIELDS (type);
lastval = 0;
for (i = 0; i < len; i++) {
if (lastval != TYPE_FIELD_BITPOS (type, i)) {
lastval = TYPE_FIELD_BITPOS (type, i);
}
if (STREQ(TYPE_FIELD_NAME(type, i), req->name)) {
req->tagname = "(unknown)";
req->value = lastval;
return;
}
lastval++;
}
}
The function is only used for anonymous (nameless) enums like MM_ANONPAGES.
It simply walks through the enumerator fields and looks for a matching string,
having captured the value of each enumerator in "lastval". This function
hasn't
changed, and has simply been forward-ported with each upgrade of gdb. What has
changed, though, is gdb itself between gdb-7.3.1 and gdb-7.6, which added a new
TYPE_FIELD_ENUMVAL() macro, which should replace the two instances of
TYPE_FIELD_BITPOS() above.
I'm thinking that this is an endian issue, where the generic TYPE_FIELD_BITPOS()
macro works OK for little-endian machines, and probably has always failed for big-endian
machines. I'm provisioning a big-endian ppc64 to verify that. (Although I'm not
sure
what macro should have been used in the older gdb versions that didn't have a
TYPE_FIELD_ENUMVAL()?)
Anyway, that's the resolution -- I'll be updating the gdb-7.6.patch upstream later
today
or tomorrow.
Dave