Hello Norbert,
On Mon, 17 Sep 2012 18:52:57 +0200
"Trapp, Norbert" <norbert.trapp at ts.fujitsu.com> wrote:
> > 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")
Sorry for my carelessness.
However, I still think that to integrate OFFSET_IN_UNION_INIT into OFFSET_INIT
is reasonable. So, please use OFFSET_INIT in v1.5.0 or later.
> >
> > 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.
As for getting the offset, it is necessary to descend into structures/unions even
which are named.
So, I'll modify dwarf_info.c as below in the next version.
diff --git a/dwarf_info.c b/dwarf_info.c
index fb11e49..0c18dd1 100644
--- a/dwarf_info.c
+++ b/dwarf_info.c
@@ -447,10 +447,8 @@ get_dwarf_base_type(Dwarf_Die *die)
}
static int
-is_anonymous_container(Dwarf_Die *die)
+is_container(Dwarf_Die *die)
{
- 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
@@ -492,13 +490,13 @@ search_member(Dwarf_Die *die)
continue;
/*
- * Descend into anonymous members and search for member
+ * Descend into structures/unions 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))
+ if (is_container(&die_type))
if (search_member(&die_type)) {
adjust_member_offset(walker);
return TRUE;
@@ -1047,9 +1045,13 @@ get_member_offset(char *structname, char *membername, int cmd)
dwarf_info.cmd = cmd;
dwarf_info.struct_name = structname;
dwarf_info.struct_size = NOT_FOUND_STRUCTURE;
- dwarf_info.member_name = membername;
dwarf_info.member_offset = NOT_FOUND_STRUCTURE;
+ if (dwarf_info.cmd == DWARF_INFO_GET_MEMBER_OFFSET_1ST_UNION)
+ dwarf_info.member_name = "";
+ else
+ dwarf_info.member_name = membername;
+
if (!get_debug_info())
return FAILED_DWARFINFO;
Thanks
Atsushi Kumagai
