From 57115bb054f20a7e64182c8ffdbef976a914f074 Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Tue, 8 Oct 2013 19:56:13 +0000 Subject: fix PR symtab/15597 This patch fixes gdb PR symtab/15597. The bug is that the .gnu_debugaltlink section includes the build-id of the alt file, but gdb does not use it. This patch fixes the problem by changing gdb to do what it ought to always have done: verify the build id of the file found using the filename in .gnu_debugaltlink; and if that does not match, try to find the correct debug file using the build-id and debug-file-directory. This patch touches BFD. Previously, gdb had its own code for parsing .gnu_debugaltlink; I changed it to use the BFD functions after those were introduced. However, the BFD functions are incorrect -- they assume that .gnu_debugaltlink is formatted like .gnu_debuglink. However, it it is not. Instead, it consists of a file name followed by the build-id -- no alignment, and the build-id is not a CRC. Fixing this properly is a bit of a pain. But, because separate_alt_debug_file_exists just has a FIXME for the build-id case, I did not fix it properly. Instead I introduced a hack. This leaves BFD working just as well as it did before my patch. I'm willing to do something better here but I could use some guidance as to what. It seems that the build-id code in BFD is largely punted on. FWIW gdb is the only user of bfd_get_alt_debug_link_info outside of BFD itself. I moved the build-id logic out of elfread.c and into a new file. This seemed cleanest to me. Writing a test case was a bit of a pain. I added a couple new features to the DWARF assembler to handle this. Built and regtested on x86-64 Fedora 18. * bfd-in2.h: Rebuild. * opncls.c (bfd_get_alt_debug_link_info): Add buildid_len parameter. Change type of buildid_out. Update. (get_alt_debug_link_info_shim): New function. (bfd_follow_gnu_debuglink): Use it. * Makefile.in (SFILES): Add build-id.c. (HFILES_NO_SRCDIR): Add build-id.h. * build-id.c: New file, largely from elfread.c. Modified most functions. * build-id.h: New file. * dwarf2read.c (dwarf2_get_dwz_file): Update for change to bfd_get_alt_debug_link_info. Verify dwz file's build-id. Search for dwz file using build-id. * elfread.c (build_id_bfd_get, build_id_verify) (build_id_to_debug_filename, find_separate_debug_file): Remove. * gdb.dwarf2/dwzbuildid.exp: New file. * lib/dwarf.exp (Dwarf::_section): Add "flags" and "type" parameters. (Dwarf::_defer_output): Change "section" parameter to "section_spec"; update. (Dwarf::gnu_debugaltlink, Dwarf::_note, Dwarf::build_id): New procs. --- gdb/elfread.c | 126 +--------------------------------------------------------- 1 file changed, 1 insertion(+), 125 deletions(-) (limited to 'gdb/elfread.c') diff --git a/gdb/elfread.c b/gdb/elfread.c index 4a3d71312dd..0095ad9731b 100644 --- a/gdb/elfread.c +++ b/gdb/elfread.c @@ -45,6 +45,7 @@ #include "regcache.h" #include "bcache.h" #include "gdb_bfd.h" +#include "build-id.h" extern void _initialize_elfread (void); @@ -1087,131 +1088,6 @@ elf_gnu_ifunc_resolver_return_stop (struct breakpoint *b) update_breakpoint_locations (b, sals, sals_end); } -/* Locate NT_GNU_BUILD_ID from ABFD and return its content. */ - -static const struct elf_build_id * -build_id_bfd_get (bfd *abfd) -{ - if (!bfd_check_format (abfd, bfd_object) - || bfd_get_flavour (abfd) != bfd_target_elf_flavour - || elf_tdata (abfd)->build_id == NULL) - return NULL; - - return elf_tdata (abfd)->build_id; -} - -/* Return if FILENAME has NT_GNU_BUILD_ID matching the CHECK value. */ - -static int -build_id_verify (const char *filename, const struct elf_build_id *check) -{ - bfd *abfd; - const struct elf_build_id *found; - int retval = 0; - - /* We expect to be silent on the non-existing files. */ - abfd = gdb_bfd_open_maybe_remote (filename); - if (abfd == NULL) - return 0; - - found = build_id_bfd_get (abfd); - - if (found == NULL) - warning (_("File \"%s\" has no build-id, file skipped"), filename); - else if (found->size != check->size - || memcmp (found->data, check->data, found->size) != 0) - warning (_("File \"%s\" has a different build-id, file skipped"), - filename); - else - retval = 1; - - gdb_bfd_unref (abfd); - - return retval; -} - -static char * -build_id_to_debug_filename (const struct elf_build_id *build_id) -{ - char *link, *debugdir, *retval = NULL; - VEC (char_ptr) *debugdir_vec; - struct cleanup *back_to; - int ix; - - /* DEBUG_FILE_DIRECTORY/.build-id/ab/cdef */ - link = alloca (strlen (debug_file_directory) + (sizeof "/.build-id/" - 1) + 1 - + 2 * build_id->size + (sizeof ".debug" - 1) + 1); - - /* Keep backward compatibility so that DEBUG_FILE_DIRECTORY being "" will - cause "/.build-id/..." lookups. */ - - debugdir_vec = dirnames_to_char_ptr_vec (debug_file_directory); - back_to = make_cleanup_free_char_ptr_vec (debugdir_vec); - - for (ix = 0; VEC_iterate (char_ptr, debugdir_vec, ix, debugdir); ++ix) - { - size_t debugdir_len = strlen (debugdir); - const gdb_byte *data = build_id->data; - size_t size = build_id->size; - char *s; - - memcpy (link, debugdir, debugdir_len); - s = &link[debugdir_len]; - s += sprintf (s, "/.build-id/"); - if (size > 0) - { - size--; - s += sprintf (s, "%02x", (unsigned) *data++); - } - if (size > 0) - *s++ = '/'; - while (size-- > 0) - s += sprintf (s, "%02x", (unsigned) *data++); - strcpy (s, ".debug"); - - /* lrealpath() is expensive even for the usually non-existent files. */ - if (access (link, F_OK) == 0) - retval = lrealpath (link); - - if (retval != NULL && !build_id_verify (retval, build_id)) - { - xfree (retval); - retval = NULL; - } - - if (retval != NULL) - break; - } - - do_cleanups (back_to); - return retval; -} - -static char * -find_separate_debug_file_by_buildid (struct objfile *objfile) -{ - const struct elf_build_id *build_id; - - build_id = build_id_bfd_get (objfile->obfd); - if (build_id != NULL) - { - char *build_id_name; - - build_id_name = build_id_to_debug_filename (build_id); - /* Prevent looping on a stripped .debug file. */ - if (build_id_name != NULL - && filename_cmp (build_id_name, objfile_name (objfile)) == 0) - { - warning (_("\"%s\": separate debug info file has no debug info"), - build_id_name); - xfree (build_id_name); - } - else if (build_id_name != NULL) - return build_id_name; - } - return NULL; -} - /* Scan and build partial symbols for a symbol file. We have been initialized by a call to elf_symfile_init, which currently does nothing. -- cgit v1.2.1