From ad47854627f76c7959ae1a7ae59c9fcda38091c5 Mon Sep 17 00:00:00 2001 From: "Guillermo E. Martinez via Libabigail" Date: Wed, 7 Sep 2022 18:40:42 -0500 Subject: [PATCH] ctf-reader: Lookup debug info for symbols in a non default archive member 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 Signed-off-by: Dodji Seketeli --- src/abg-ctf-reader.cc | 74 +++++++++++++++++++++++++++++++++++++------ 1 file changed, 64 insertions(+), 10 deletions(-) diff --git a/src/abg-ctf-reader.cc b/src/abg-ctf-reader.cc index 71808f9a..e307fcd7 100644 --- a/src/abg-ctf-reader.cc +++ b/src/abg-ctf-reader.cc @@ -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(); @@ -1248,19 +1303,17 @@ 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) - continue; + 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);