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ctf-reader: Lookup debug info for symbols in a non default archive member

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The current mechanism used by the ctf reader for looking for debug
information given a specific Linux symbol is the following: it opens
the dictionary (default) which name matches the binary name being
processed in the current corpus, e.g. `vmlinux' or
`module-name`.ko. However there are symbols and information that are
not located in the default dictionary; this is evident comparing the
symbols in `Module.symvers' file with ABI XML file, so for example,
the ctf reader is expecting to find the information for
`LZ4_decompress_fast' symbol in the CTF `vmlinux' archive member,
because this symbols is defined in `vmlinux' binary:

   0x4c416eb9	LZ4_decompress_fast	vmlinux	EXPORT_SYMBOL

But, it figures out that it is missing. The correct location is
`vmlinux#0' dictionary:

  CTF archive member: vmlinux:
    ...
    Function objects:
    ...

  CTF archive member: vmlinux#0:
    Function objects:
    ...
    LZ4_decompress_fast -> 0x80037400: (kind 5) int (*) (const char *, char *, int) (aligned at 0x8)
    ...

Therefore, ctf reader must be looking for debug information in the
whole archive; fortunately `libctf' provides a fast lookup mechanism
using cache, dictionary references, etc., so the penalty performance
is ~10%.

Now, it make use of `ctf_lookup_by_symbol_name' at first instance
which is in charge to locate symbol information given a symbol name on
either CTF Function or Variable sections; if the symbol isn't found it
tries using `ctf_lookup_variable' to look into the CTF Variable
section; this could happens due to `ld' operating with the
`--ctf-variables' option which makes function types information to
reside in the CTF Variable section.

	* src/abg-ctf-reader.cc (lookup_symbol_in_ctf_archive): New function.
	(process_ctf_archive): Use `lookup_symbol_in_ctf_archive'.

Signed-off-by: Guillermo E. Martinez <guillermo.e.martinez@oracle.com>
Signed-off-by: Dodji Seketeli <dodji@redhat.com>
This commit is contained in:
Guillermo E. Martinez via Libabigail 2022-09-07 18:40:42 -05:00 committed by Dodji Seketeli
parent 2bfea52331
commit ad47854627
1 changed files with 64 additions and 10 deletions
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72
src/abg-ctf-reader.cc
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@ -1204,6 +1204,61 @@ lookup_type(read_context *ctxt, corpus_sptr corp,
return result;
}
/// Given a symbol name, lookup the corresponding CTF information in
/// the default dictionary (CTF archive member provided by the caller)
/// If the search is not success, the looks for the symbol name
/// in _all_ archive members.
///
/// @param ctfa the CTF archive.
/// @param dict the default dictionary to looks for.
/// @param sym_name the symbol name.
/// @param corp the IR corpus.
///
/// Note that if @ref sym_name is found in other than its default dictionary
/// @ref ctf_dict will be updated and it must be explicitly closed by its
/// caller.
///
/// @return a valid CTF type id, if @ref sym_name was found, CTF_ERR otherwise.
static ctf_id_t
lookup_symbol_in_ctf_archive(ctf_archive_t *ctfa, ctf_dict_t **ctf_dict,
const char *sym_name)
{
int ctf_err;
ctf_dict_t *dict = *ctf_dict;
ctf_id_t ctf_type = ctf_lookup_by_symbol_name(dict, sym_name);
if (ctf_type != CTF_ERR)
return ctf_type;
/* Probably --ctf-variables option was used by ld, so symbol type
definition must be found in the CTF Variable section. */
ctf_type = ctf_lookup_variable(dict, sym_name);
/* Not lucky, then, search in whole archive */
if (ctf_type == CTF_ERR)
{
ctf_dict_t *fp;
ctf_next_t *i = NULL;
const char *arcname;
while ((fp = ctf_archive_next(ctfa, &i, &arcname, 1, &ctf_err)) != NULL)
{
if ((ctf_type = ctf_lookup_by_symbol_name (fp, sym_name)) == CTF_ERR)
ctf_type = ctf_lookup_variable(fp, sym_name);
if (ctf_type != CTF_ERR)
{
*ctf_dict = fp;
break;
}
ctf_dict_close(fp);
}
}
return ctf_type;
}
/// Process a CTF archive and create libabigail IR for the types,
/// variables and function declarations found in the archive, iterating
/// over public symbols. The IR is added to the given corpus.
@ -1222,7 +1277,7 @@ process_ctf_archive(read_context *ctxt, corpus_sptr corp)
corp->add(ir_translation_unit);
int ctf_err;
ctf_dict_t *ctf_dict;
ctf_dict_t *ctf_dict, *dict_tmp;
const auto symtab = ctxt->symtab;
symtab_reader::symtab_filter filter = symtab->make_filter();
filter.set_public_symbols();
@ -1248,18 +1303,16 @@ process_ctf_archive(read_context *ctxt, corpus_sptr corp)
abort();
}
dict_tmp = ctf_dict;
for (const auto& symbol : symtab_reader::filtered_symtab(*symtab, filter))
{
std::string sym_name = symbol->get_name();
ctf_id_t ctf_sym_type;
ctf_sym_type = ctf_lookup_variable(ctf_dict, sym_name.c_str());
if (ctf_sym_type == (ctf_id_t) -1
&& !(corp->get_origin() & corpus::LINUX_KERNEL_BINARY_ORIGIN))
// lookup in function objects
ctf_sym_type = ctf_lookup_by_symbol_name(ctf_dict, sym_name.c_str());
if (ctf_sym_type == (ctf_id_t) -1)
ctf_sym_type = lookup_symbol_in_ctf_archive(ctxt->ctfa, &ctf_dict,
sym_name.c_str());
if (ctf_sym_type == CTF_ERR)
continue;
if (ctf_type_kind(ctf_dict, ctf_sym_type) != CTF_K_FUNCTION)
@ -1298,13 +1351,14 @@ process_ctf_archive(read_context *ctxt, corpus_sptr corp)
func_type,
0 /* is_inline */,
location()));
func_declaration->set_symbol(symbol);
add_decl_to_scope(func_declaration,
ir_translation_unit->get_global_scope());
func_declaration->set_is_in_public_symbol_table(true);
ctxt->maybe_add_fn_to_exported_decls(func_declaration.get());
}
ctf_dict = dict_tmp;
}
ctf_dict_close(ctf_dict);