gdb/build-id.c

   1 /* build-id-related functions.
   2
   3    Copyright (C) 1991-2015 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "bfd.h"
  22 #include "elf-bfd.h"
  23 #include "gdb_bfd.h"
  24 #include "build-id.h"
  25 #include "gdb_vecs.h"
  26 #include "symfile.h"
  27 #include "objfiles.h"
  28 #include "filenames.h"
  29
  30 /* See build-id.h.  */
  31
  32 const struct elf_build_id *
  33 build_id_bfd_get (bfd *abfd)
  34 {
  35   if (!bfd_check_format (abfd, bfd_object)
  36       || bfd_get_flavour (abfd) != bfd_target_elf_flavour
  37       /* Although this is ELF_specific, it is safe to do in generic
  38          code because it does not rely on any ELF-specific symbols at
  39          link time, and if the ELF code is not available in BFD, then
  40          ABFD will not have the ELF flavour.  */
  41       || elf_tdata (abfd)->build_id == NULL)
  42     return NULL;
  43
  44   return elf_tdata (abfd)->build_id;
  45 }
  46
  47 /* See build-id.h.  */
  48
  49 int
  50 build_id_verify (bfd *abfd, size_t check_len, const bfd_byte *check)
  51 {
  52   const struct elf_build_id *found;
  53   int retval = 0;
  54
  55   found = build_id_bfd_get (abfd);
  56
  57   if (found == NULL)
  58     warning (_("File \"%s\" has no build-id, file skipped"),
  59              bfd_get_filename (abfd));
  60   else if (found->size != check_len
  61            || memcmp (found->data, check, found->size) != 0)
  62     warning (_("File \"%s\" has a different build-id, file skipped"),
  63              bfd_get_filename (abfd));
  64   else
  65     retval = 1;
  66
  67   return retval;
  68 }
  69
  70 /* See build-id.h.  */
  71
  72 bfd *
  73 build_id_to_debug_bfd (size_t build_id_len, const bfd_byte *build_id)
  74 {
  75   char *link, *debugdir;
  76   VEC (char_ptr) *debugdir_vec;
  77   struct cleanup *back_to;
  78   int ix;
  79   bfd *abfd = NULL;
  80
  81   /* DEBUG_FILE_DIRECTORY/.build-id/ab/cdef */
  82   link = alloca (strlen (debug_file_directory) + (sizeof "/.build-id/" - 1) + 1
  83                  + 2 * build_id_len + (sizeof ".debug" - 1) + 1);
  84
  85   /* Keep backward compatibility so that DEBUG_FILE_DIRECTORY being "" will
  86      cause "/.build-id/..." lookups.  */
  87
  88   debugdir_vec = dirnames_to_char_ptr_vec (debug_file_directory);
  89   back_to = make_cleanup_free_char_ptr_vec (debugdir_vec);
  90
  91   for (ix = 0; VEC_iterate (char_ptr, debugdir_vec, ix, debugdir); ++ix)
  92     {
  93       size_t debugdir_len = strlen (debugdir);
  94       const gdb_byte *data = build_id;
  95       size_t size = build_id_len;
  96       char *s;
  97       char *filename = NULL;
  98
  99       memcpy (link, debugdir, debugdir_len);
 100       s = &link[debugdir_len];
 101       s += sprintf (s, "/.build-id/");
 102       if (size > 0)
 103         {
 104           size--;
 105           s += sprintf (s, "%02x", (unsigned) *data++);
 106         }
 107       if (size > 0)
 108         *s++ = '/';
 109       while (size-- > 0)
 110         s += sprintf (s, "%02x", (unsigned) *data++);
 111       strcpy (s, ".debug");
 112
 113       /* lrealpath() is expensive even for the usually non-existent files.  */
 114       if (access (link, F_OK) == 0)
 115         filename = lrealpath (link);
 116
 117       if (filename == NULL)
 118         continue;
 119
 120       /* We expect to be silent on the non-existing files.  */
 121       abfd = gdb_bfd_open_maybe_remote (filename);
 122       if (abfd == NULL)
 123         continue;
 124
 125       if (build_id_verify (abfd, build_id_len, build_id))
 126         break;
 127
 128       gdb_bfd_unref (abfd);
 129       abfd = NULL;
 130     }
 131
 132   do_cleanups (back_to);
 133   return abfd;
 134 }
 135
 136 /* See build-id.h.  */
 137
 138 char *
 139 find_separate_debug_file_by_buildid (struct objfile *objfile)
 140 {
 141   const struct elf_build_id *build_id;
 142
 143   build_id = build_id_bfd_get (objfile->obfd);
 144   if (build_id != NULL)
 145     {
 146       bfd *abfd;
 147
 148       abfd = build_id_to_debug_bfd (build_id->size, build_id->data);
 149       /* Prevent looping on a stripped .debug file.  */
 150       if (abfd != NULL
 151           && filename_cmp (bfd_get_filename (abfd),
 152                            objfile_name (objfile)) == 0)
 153         {
 154           warning (_("\"%s\": separate debug info file has no debug info"),
 155                    bfd_get_filename (abfd));
 156           gdb_bfd_unref (abfd);
 157         }
 158       else if (abfd != NULL)
 159         {
 160           char *result = xstrdup (bfd_get_filename (abfd));
 161
 162           gdb_bfd_unref (abfd);
 163           return result;
 164         }
 165     }
 166   return NULL;
 167 }