[PATCHv3 0/9] Support Xen versions up to xen-4.1

[Trapp, Norbert]

Hello Stefan,

> -----Original Message-----
> From: Stefan Bader [mailto:stefan.bader at canonical.com]
> Sent: Monday, September 17, 2012 2:38 PM
> To: Trapp, Norbert
> Cc: Atsushi Kumagai; petr at tesarici.cz; kexec at lists.infradead.org
> Subject: Re: [PATCHv3 0/9] Support Xen versions up to xen-4.1
> 
> On 12.09.2012 16:39, Trapp, Norbert wrote:
> > Hello Atsushi, Petr, Stefan et al.,
> >
> 
> Hi Norbert,
> 
> > When applying the makedumpfile Xen4 patches to the makedumpfile 1.5.0
> > version and using it for a crash file to save just the dom0 and xen pages
> > it again worked splendid in that makedumpfile was much faster than without
> > the Xen4 patches. Alas I had to remove the OFFSET_IN_UNION_INIT(page._domain,
> > "page_info", "domain") call because OFFSET_IN_UNION_INIT was no longer present.
> > It didn't matter much because the call is only needed for makedumpfile -g or when
> > using the /boot/xen-syms file. In the current 1.5.0  makedumpfile.c version you
> > see
> >
> >     OFFSET_INIT(page_info._domain, "page_info", "u").
> >
> > The Xen4 patch modified this because the _domain structure member is in different
> > unions for different version (x86, ia64) and may also not be the first entry in
> > the union depending on the Xen version.
> >
> >     OFFSET_IN_UNION_INIT(page_info._domain, "page_info", "_domain");
> >
> > As an experiment I tried to use
> >
> 
> >     OFFSET_INIT(page_info._domain, "page_info", "domain")
> 
> Just to make sure and since I am a bit lazy: with the Xen patch the page_info
> structure has a member (somewhere) named domain? (or _domain)?
> 

Just to get you on the right track, the struct page_info in the Xen code is meant.
Not the one in the makedumpfile code.

For example in xen-4.1.3/xen/common/kexec.c:
#ifdef __ia64__
    VMCOREINFO_OFFSET_SUB(page_info, u.inuse, _domain);
#else
    VMCOREINFO_OFFSET_SUB(page_info, v.inuse, _domain);
#endif

And the different page_info structures you find in:
xen-4.1.3/xen/include/asm-ia64/mm.h
xen-4.1.3/xen/include/asm-x86/mm.h

And also the structures can be different depending on the Xen version.

> >
> > with makedumpfile 1.5.0. To get the correct offset I had to
> > modify the dwarf_info.c code:
> >
> > --- ../makedumpfile-1.5.0/dwarf_info.c  2012-09-06 07:30:23.000000000 +0200
> > +++ dwarf_info.c        2012-09-12 15:49:23.000000000 +0200
> > @@ -449,8 +449,8 @@
> >  static int
> >  is_anonymous_container(Dwarf_Die *die)
> >  {
> > -       if (dwarf_diename(die))
> > -               return FALSE;
> > +       //if (dwarf_diename(die))
> > +       //      return FALSE;
> >         if (dwarf_tag(die) == DW_TAG_structure_type)
> >                 return TRUE;
> >         if (dwarf_info.cmd != DWARF_INFO_GET_MEMBER_OFFSET_1ST_UNION
> > @@ -495,7 +495,7 @@
> >                  * Descend into anonymous members and search for member
> >                  * there.
> >                  */
> > -               if (!name) {
> > +               if ((!name) || (strcmp(name, dwarf_info.member_name) != 0)) {
> >                         if (!get_die_type(walker, &die_type))
> >                                 continue;
> >                         if (is_anonymous_container(&die_type))
> >
> >
> > This is not a patch but just a description of what I modified for a test.
> > The underlying question is why only the anonymous unions are used and not the
> > ones with a name.
> 
> I made the patch because one element in some anonymous structure/union combo was
> not found in newer kernels and the previous exceptions for such a thing were
> hard coded. But as far as the dwarf info I was looking at the named
> structures/unions were handled and I did not want to modify that case without a
> way to test.
> 
> -Stefan

With kind regards

	Norbert

Norbert Trapp
PBG PDG ES&S SWE OS 6

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