From 39f53acb410c3e303fb25ff823de57eb316515ca Mon Sep 17 00:00:00 2001 From: Aaron Merey Date: Wed, 2 Mar 2022 18:46:14 -0500 Subject: [PATCH] gdb: Add soname to build-id mapping for core files Since commit aa2d5a422 gdb has been able to read executable and shared library build-ids within core files. Expand this functionality so that each core file bfd maintains a map of soname to build-id for each shared library referenced in the core file. This feature may be used to verify that gdb has found the correct shared libraries for core files and to facilitate downloading shared libaries via debuginfod. --- gdb/corelow.c | 11 ++++++ gdb/linux-tdep.c | 24 ++++++++++++- gdb/solib.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++ gdb/solib.h | 20 +++++++++++ 4 files changed, 141 insertions(+), 1 deletion(-) diff --git a/gdb/corelow.c b/gdb/corelow.c index 001c4f147fc..c1148288932 100644 --- a/gdb/corelow.c +++ b/gdb/corelow.c @@ -282,6 +282,17 @@ core_target::build_file_mappings () /* Set target_section fields. */ m_core_file_mappings.emplace_back (start, end, sec); + + /* If this is a bfd of a shared library, record its soname + and build id. */ + if (build_id != nullptr) + { + gdb::unique_xmalloc_ptr soname + = gdb_bfd_read_elf_soname (bfd->filename); + if (soname != nullptr) + set_cbfd_soname_build_id (current_program_space->cbfd, + soname.get (), build_id); + } }); normalize_mem_ranges (&m_core_unavailable_mappings); diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c index d4868902ac3..52cdaae034b 100644 --- a/gdb/linux-tdep.c +++ b/gdb/linux-tdep.c @@ -44,6 +44,7 @@ #include "solib-svr4.h" #include +#include /* This enum represents the values that the user can choose when informing the Linux kernel about which memory mappings will be @@ -1185,6 +1186,22 @@ linux_read_core_file_mappings if (f != descend) warning (_("malformed note - filename area is too big")); + const bfd_build_id *orig_build_id = cbfd->build_id; + std::unordered_map vma_map; + + /* Search for solib build-ids in the core file. Each time one is found, + map the start vma of the corresponding elf header to the build-id. */ + for (bfd_section *sec = cbfd->sections; sec != nullptr; sec = sec->next) + { + cbfd->build_id = nullptr; + + if (sec->flags & SEC_LOAD + && (get_elf_backend_data (cbfd)->elf_backend_core_find_build_id + (cbfd, (bfd_vma) sec->filepos))) + vma_map[sec->vma] = cbfd->build_id; + } + + cbfd->build_id = orig_build_id; pre_loop_cb (count); for (int i = 0; i < count; i++) @@ -1198,8 +1215,13 @@ linux_read_core_file_mappings descdata += addr_size; char * filename = filenames; filenames += strlen ((char *) filenames) + 1; + const bfd_build_id *build_id = nullptr; + auto vma_map_it = vma_map.find (start); + + if (vma_map_it != vma_map.end ()) + build_id = vma_map_it->second; - loop_cb (i, start, end, file_ofs, filename, nullptr); + loop_cb (i, start, end, file_ofs, filename, build_id); } } diff --git a/gdb/solib.c b/gdb/solib.c index 8bcbfa22df1..00e6c7994b3 100644 --- a/gdb/solib.c +++ b/gdb/solib.c @@ -23,6 +23,7 @@ #include #include "symtab.h" #include "bfd.h" +#include "build-id.h" #include "symfile.h" #include "objfiles.h" #include "gdbcore.h" @@ -519,6 +520,55 @@ solib_bfd_open (const char *pathname) return abfd; } +/* Mapping of a core file's shared library sonames to their respective + build-ids. Added to the registries of core file bfds. */ + +typedef std::unordered_map soname_build_id_map; + +/* Key used to associate a soname_build_id_map to a core file bfd. */ + +static const struct bfd_key cbfd_soname_build_id_data_key; + +/* See solib.h. */ + +void +set_cbfd_soname_build_id (gdb_bfd_ref_ptr abfd, + const char *soname, + const bfd_build_id *build_id) +{ + gdb_assert (abfd.get () != nullptr); + gdb_assert (soname != nullptr); + gdb_assert (build_id != nullptr); + + soname_build_id_map *mapptr = cbfd_soname_build_id_data_key.get (abfd.get ()); + + if (mapptr == nullptr) + mapptr = cbfd_soname_build_id_data_key.emplace (abfd.get ()); + + (*mapptr)[soname] = build_id_to_string (build_id); +} + +/* See solib.h. */ + +gdb::unique_xmalloc_ptr +get_cbfd_soname_build_id (gdb_bfd_ref_ptr abfd, const char *soname) +{ + if (abfd.get () == nullptr || soname == nullptr) + return {}; + + soname_build_id_map *mapptr + = cbfd_soname_build_id_data_key.get (abfd.get ()); + + if (mapptr == nullptr) + return {}; + + auto it = mapptr->find (lbasename (soname)); + if (it == mapptr->end ()) + return {}; + + return make_unique_xstrdup (it->second.c_str ()); +} + /* Given a pointer to one of the shared objects in our list of mapped objects, use the recorded name to open a bfd descriptor for the object, build a section table, relocate all the section addresses @@ -1586,6 +1636,43 @@ gdb_bfd_scan_elf_dyntag (const int desired_dyntag, bfd *abfd, CORE_ADDR *ptr, return 0; } +/* See solib.h. */ + +gdb::unique_xmalloc_ptr +gdb_bfd_read_elf_soname (const char *filename) +{ + gdb_bfd_ref_ptr abfd = gdb_bfd_open (filename, gnutarget); + + if (abfd == nullptr) + return {}; + + /* Check that ABFD is an ET_DYN ELF file. */ + if (!bfd_check_format (abfd.get (), bfd_object) + || !(bfd_get_file_flags (abfd.get ()) & DYNAMIC)) + return {}; + + CORE_ADDR idx; + if (!gdb_bfd_scan_elf_dyntag (DT_SONAME, abfd.get (), &idx, nullptr)) + return {}; + + struct bfd_section *dynstr = bfd_get_section_by_name (abfd.get (), ".dynstr"); + int sect_size = bfd_section_size (dynstr); + if (dynstr == nullptr || sect_size <= idx) + return {}; + + /* Read soname from the string table. */ + gdb::byte_vector dynstr_buf; + if (!gdb_bfd_get_full_section_contents (abfd.get (), dynstr, &dynstr_buf)) + return {}; + + /* Ensure soname is null-terminated before returning a copy. */ + char *soname = (char *) dynstr_buf.data () + idx; + if (strnlen (soname, sect_size - idx) == sect_size - idx) + return {}; + + return make_unique_xstrdup (soname); +} + /* Lookup the value for a specific symbol from symbol table. Look up symbol from ABFD. MATCH_SYM is a callback function to determine whether to pick up a symbol. DATA is the input of this callback function. Return NULL diff --git a/gdb/solib.h b/gdb/solib.h index 2258b0ba6a0..cd6c8a81104 100644 --- a/gdb/solib.h +++ b/gdb/solib.h @@ -118,6 +118,12 @@ extern CORE_ADDR gdb_bfd_lookup_symbol_from_symtab (bfd *abfd, extern int gdb_bfd_scan_elf_dyntag (const int desired_dyntag, bfd *abfd, CORE_ADDR *ptr, CORE_ADDR *ptr_addr); +/* If FILENAME refers to an ELF shared object then attempt to return the + string referred to by its DT_SONAME tag. */ + +extern gdb::unique_xmalloc_ptr gdb_bfd_read_elf_soname + (const char *filename); + /* Enable or disable optional solib event breakpoints as appropriate. */ extern void update_solib_breakpoints (void); @@ -126,4 +132,18 @@ extern void update_solib_breakpoints (void); extern void handle_solib_event (void); +/* Associate SONAME with BUILD_ID in ABFD's registry so that it can be + retrieved with get_cbfd_soname_build_id. */ + +extern void set_cbfd_soname_build_id (gdb_bfd_ref_ptr abfd, + const char *soname, + const bfd_build_id *build_id); + +/* If SONAME had a build-id associated with it in ABFD's registry by a + previous call to set_cbfd_soname_build_id then return the build-id + as a NULL-terminated hex string. */ + +extern gdb::unique_xmalloc_ptr get_cbfd_soname_build_id + (gdb_bfd_ref_ptr abfd, const char *soname); + #endif /* SOLIB_H */ -- 2.30.2