gdb/build-id.c

   1 /* build-id-related functions.
   2
   3    Copyright (C) 1991-2019 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 "gdb_bfd.h"
  23 #include "build-id.h"
  24 #include "common/gdb_vecs.h"
  25 #include "symfile.h"
  26 #include "objfiles.h"
  27 #include "filenames.h"
  28 #include "gdbcore.h"
  29
  30 /* See build-id.h.  */
  31
  32 const struct bfd_build_id *
  33 build_id_bfd_get (bfd *abfd)
  34 {
  35   if (!bfd_check_format (abfd, bfd_object))
  36     return NULL;
  37
  38   if (abfd->build_id != NULL)
  39     return abfd->build_id;
  40
  41   /* No build-id */
  42   return NULL;
  43 }
  44
  45 /* See build-id.h.  */
  46
  47 int
  48 build_id_verify (bfd *abfd, size_t check_len, const bfd_byte *check)
  49 {
  50   const struct bfd_build_id *found;
  51   int retval = 0;
  52
  53   found = build_id_bfd_get (abfd);
  54
  55   if (found == NULL)
  56     warning (_("File \"%s\" has no build-id, file skipped"),
  57              bfd_get_filename (abfd));
  58   else if (found->size != check_len
  59            || memcmp (found->data, check, found->size) != 0)
  60     warning (_("File \"%s\" has a different build-id, file skipped"),
  61              bfd_get_filename (abfd));
  62   else
  63     retval = 1;
  64
  65   return retval;
  66 }
  67
  68 /* Helper for build_id_to_debug_bfd.  LINK is a path to a potential
  69    build-id-based separate debug file, potentially a symlink to the real file.
  70    If the file exists and matches BUILD_ID, return a BFD reference to it.  */
  71
  72 static gdb_bfd_ref_ptr
  73 build_id_to_debug_bfd_1 (const std::string &link, size_t build_id_len,
  74                          const bfd_byte *build_id)
  75 {
  76   if (separate_debug_file_debug)
  77     {
  78       printf_unfiltered (_("  Trying %s..."), link.c_str ());
  79       gdb_flush (gdb_stdout);
  80     }
  81
  82   /* lrealpath() is expensive even for the usually non-existent files.  */
  83   gdb::unique_xmalloc_ptr<char> filename;
  84   if (access (link.c_str (), F_OK) == 0)
  85     filename.reset (lrealpath (link.c_str ()));
  86
  87   if (filename == NULL)
  88     {
  89       if (separate_debug_file_debug)
  90         printf_unfiltered (_(" no, unable to compute real path\n"));
  91
  92       return {};
  93     }
  94
  95   /* We expect to be silent on the non-existing files.  */
  96   gdb_bfd_ref_ptr debug_bfd = gdb_bfd_open (filename.get (), gnutarget, -1);
  97
  98   if (debug_bfd == NULL)
  99     {
 100       if (separate_debug_file_debug)
 101         printf_unfiltered (_(" no, unable to open.\n"));
 102
 103       return {};
 104     }
 105
 106   if (!build_id_verify (debug_bfd.get(), build_id_len, build_id))
 107     {
 108       if (separate_debug_file_debug)
 109         printf_unfiltered (_(" no, build-id does not match.\n"));
 110
 111       return {};
 112     }
 113
 114   if (separate_debug_file_debug)
 115     printf_unfiltered (_(" yes!\n"));
 116
 117   return debug_bfd;
 118 }
 119
 120 /* See build-id.h.  */
 121
 122 gdb_bfd_ref_ptr
 123 build_id_to_debug_bfd (size_t build_id_len, const bfd_byte *build_id)
 124 {
 125   /* Keep backward compatibility so that DEBUG_FILE_DIRECTORY being "" will
 126      cause "/.build-id/..." lookups.  */
 127
 128   std::vector<gdb::unique_xmalloc_ptr<char>> debugdir_vec
 129     = dirnames_to_char_ptr_vec (debug_file_directory);
 130
 131   for (const gdb::unique_xmalloc_ptr<char> &debugdir : debugdir_vec)
 132     {
 133       const gdb_byte *data = build_id;
 134       size_t size = build_id_len;
 135
 136       /* Compute where the file named after the build-id would be.
 137
 138          If debugdir is "/usr/lib/debug" and the build-id is abcdef, this will
 139          give "/usr/lib/debug/.build-id/ab/cdef.debug".  */
 140       std::string link = debugdir.get ();
 141       link += "/.build-id/";
 142
 143       if (size > 0)
 144         {
 145           size--;
 146           string_appendf (link, "%02x/", (unsigned) *data++);
 147         }
 148
 149       while (size-- > 0)
 150         string_appendf (link, "%02x", (unsigned) *data++);
 151
 152       link += ".debug";
 153
 154       gdb_bfd_ref_ptr debug_bfd
 155         = build_id_to_debug_bfd_1 (link, build_id_len, build_id);
 156       if (debug_bfd != NULL)
 157         return debug_bfd;
 158
 159       /* Try to look under the sysroot as well.  If the sysroot is
 160          "/the/sysroot", it will give
 161          "/the/sysroot/usr/lib/debug/.build-id/ab/cdef.debug".
 162
 163          Don't do it if the sysroot is the target system ("target:").  It
 164          could work in theory, but the lrealpath in build_id_to_debug_bfd_1
 165          only works with local paths.  */
 166       if (strcmp (gdb_sysroot, TARGET_SYSROOT_PREFIX) != 0)
 167         {
 168           link = gdb_sysroot + link;
 169           debug_bfd = build_id_to_debug_bfd_1 (link, build_id_len, build_id);
 170           if (debug_bfd != NULL)
 171             return debug_bfd;
 172         }
 173     }
 174
 175   return {};
 176 }
 177
 178 /* See build-id.h.  */
 179
 180 std::string
 181 find_separate_debug_file_by_buildid (struct objfile *objfile)
 182 {
 183   const struct bfd_build_id *build_id;
 184
 185   build_id = build_id_bfd_get (objfile->obfd);
 186   if (build_id != NULL)
 187     {
 188       if (separate_debug_file_debug)
 189         printf_unfiltered (_("\nLooking for separate debug info (build-id) for "
 190                              "%s\n"), objfile_name (objfile));
 191
 192       gdb_bfd_ref_ptr abfd (build_id_to_debug_bfd (build_id->size,
 193                                                    build_id->data));
 194       /* Prevent looping on a stripped .debug file.  */
 195       if (abfd != NULL
 196           && filename_cmp (bfd_get_filename (abfd.get ()),
 197                            objfile_name (objfile)) == 0)
 198         warning (_("\"%s\": separate debug info file has no debug info"),
 199                  bfd_get_filename (abfd.get ()));
 200       else if (abfd != NULL)
 201         return std::string (bfd_get_filename (abfd.get ()));
 202     }
 203
 204   return std::string ();
 205 }