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27d2927107
In the debugging mode of self comparison induced by the invocation of
"abidw --debug-abidiff <binary>", it's useful to be able to ensure the
following invariant:
The pointer value of the canonical type of a type T that is
serialized into abixml with the id string "type-id-12" (for
instance) must keep the same canonical type pointer value when
that abixml file is de-serialized back into memory. This is
possible mainly because libabigail stays loaded in memory all the
time during both serialization and de-serialization.
This patch adds support for detecting when that invariant is not
respected.
In other words it detects when the type build from de-serializing the
type which id is "type-id-12" (for instance) has a canonical type
which pointer value is different from the pointer value of the
canonical type (of the type) that was serialized as having the type id
"type-id-12".
This is done in three phases.
The first phase happens in the code of abidw itself; after the abixml
is written on disk, another file called the "typeid file" is written
on disk as well. That later file contains a set of records; each
record associates a "type id string" (like the type IDs that appear in
the abixml file) to the pointer value of the canonical type that
matches that type id string. That file is thus now available for
manual inspection during a later debugger session. This is done by
invoking the new function write_canonical_type_ids.
The second phase appears right before abixml loading time. The typeid
file is read back and the association "type-id string" <-> is stored
in a hash map that is returned by
environment::get_type_id_canonical_type_map(). This is done by
invoking the new function load_canonical_type_ids.
The third phase happens right after the canonicalization (triggered in
the abixml reader) of a type coming from abixml, corresponding to a
given type id. It checks if the pointer value of the canonicalization
type just computed is the same as the one associated to that type id
in the map returned by environment::get_type_id_canonical_type_map.
This is a way of verifying the "stability" of a canonical type during
its serialization and de-serialization to and from abixml and it's
done as part of "abidw --debug-abidiff <binary>".
Just as an example, here is the kind of error output that I am getting
on a real life debugging session on a binary that exhibits self
comparison error:
$ abidw --debug-abidiff -d <some-binary>
error: problem detected with type 'typedef Vmalloc_t' from second corpus
error: canonical type for type 'typedef Vmalloc_t' of type-id 'type-id-179' changed from '1a083e8' to '21369b8'
[...]
$
From this output, I see that the first type for which libabigail
exhibits an instability on the pointer value of the canonical type is
the type 'typedef Vmalloc_t'. In other words, when that type is saved
to abixml, the type we read back is different. This needs further
debugging but at least it pinpoints exactly what type we are seeing
the core issue on first. This is of a tremendous help in the root
cause analysis needed to understand why the self comparison is
failing.
* include/abg-ir.h (environment::get_type_id_canonical_type_map):
Declare new data member.
* src/abg-ir.cc (environment::priv::type_id_canonical_type_map_):
Define new data member.
(environment::get_type_id_canonical_type_map): Define new method.
* include/abg-reader.h (load_canonical_type_ids): Declare new
function.
* src/abg-reader.cc (read_context::m_pointer_type_id_map):
Define new data member.
(read_context::{get_pointer_type_id_map,
maybe_check_abixml_canonical_type_stability}): Define new methods.
(read_context::{maybe_canonicalize_type,
perform_late_type_canonicalizing}): Invoke
maybe_perform_self_comparison_canonical_type_check after
canonicalization to perform canonicalization type stability
checking.
(build_type): Associate the pointer value for the newly built type
with the type id string identifying it in the abixml. Once the
abixml representation is dropped from memory and we are about to
perform type canonicalization, we can still know what the type id
of a given type coming from abixml was; it's thus possible to
verify that the canonical type associated to that type id is the
same as the one stored in the typeid file.
(read_type_id_string): Define new static function.
(load_canonical_type_ids): Define new function.
* include/abg-writer.h (write_canonical_type_ids): Likewise.
* src/abg-writer.cc (write_canonical_type_ids): Define new
function overloads.
* tools/abidw.cc (options::type_id_file_path): New data member.
(load_corpus_and_write_abixml): Write and read back the typeid
file.
Signed-off-by: Dodji Seketeli <dodji@redhat.com>
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|---|---|---|
| .. | ||
| .gitignore | ||
| abicompat.cc | ||
| abidiff.cc | ||
| abidw.cc | ||
| abilint.cc | ||
| abipkgdiff.cc | ||
| abisym.cc | ||
| binilint.cc | ||
| fedabipkgdiff | ||
| kmidiff.cc | ||
| Makefile.am | ||