gdb/build-id.c

   1 /* build-id-related functions.
   2
   3    Copyright (C) 1991-2022 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 "gdbsupport/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       && !bfd_check_format (abfd, bfd_core))
  37     return NULL;
  38
  39   if (abfd->build_id != NULL)
  40     return abfd->build_id;
  41
  42   /* No build-id */
  43   return NULL;
  44 }
  45
  46 /* See build-id.h.  */
  47
  48 int
  49 build_id_verify (bfd *abfd, size_t check_len, const bfd_byte *check)
  50 {
  51   const struct bfd_build_id *found;
  52   int retval = 0;
  53
  54   found = build_id_bfd_get (abfd);
  55
  56   if (found == NULL)
  57     warning (_("File \"%s\" has no build-id, file skipped"),
  58              bfd_get_filename (abfd));
  59   else if (found->size != check_len
  60            || memcmp (found->data, check, found->size) != 0)
  61     warning (_("File \"%s\" has a different build-id, file skipped"),
  62              bfd_get_filename (abfd));
  63   else
  64     retval = 1;
  65
  66   return retval;
  67 }
  68
  69 /* Helper for build_id_to_debug_bfd.  LINK is a path to a potential
  70    build-id-based separate debug file, potentially a symlink to the real file.
  71    If the file exists and matches BUILD_ID, return a BFD reference to it.  */
  72
  73 static gdb_bfd_ref_ptr
  74 build_id_to_debug_bfd_1 (const std::string &link, size_t build_id_len,
  75                          const bfd_byte *build_id)
  76 {
  77   if (separate_debug_file_debug)
  78     {
  79       gdb_printf (gdb_stdlog, _("  Trying %s..."), link.c_str ());
  80       gdb_flush (gdb_stdlog);
  81     }
  82
  83   /* lrealpath() is expensive even for the usually non-existent files.  */
  84   gdb::unique_xmalloc_ptr<char> filename_holder;
  85   const char *filename = nullptr;
  86   if (startswith (link, TARGET_SYSROOT_PREFIX))
  87     filename = link.c_str ();
  88   else if (access (link.c_str (), F_OK) == 0)
  89     {
  90       filename_holder.reset (lrealpath (link.c_str ()));
  91       filename = filename_holder.get ();
  92     }
  93
  94   if (filename == NULL)
  95     {
  96       if (separate_debug_file_debug)
  97         gdb_printf (gdb_stdlog,
  98                     _(" no, unable to compute real path\n"));
  99
 100       return {};
 101     }
 102
 103   /* We expect to be silent on the non-existing files.  */
 104   gdb_bfd_ref_ptr debug_bfd = gdb_bfd_open (filename, gnutarget);
 105
 106   if (debug_bfd == NULL)
 107     {
 108       if (separate_debug_file_debug)
 109         gdb_printf (gdb_stdlog, _(" no, unable to open.\n"));
 110
 111       return {};
 112     }
 113
 114   if (!build_id_verify (debug_bfd.get(), build_id_len, build_id))
 115     {
 116       if (separate_debug_file_debug)
 117         gdb_printf (gdb_stdlog, _(" no, build-id does not match.\n"));
 118
 119       return {};
 120     }
 121
 122   if (separate_debug_file_debug)
 123     gdb_printf (gdb_stdlog, _(" yes!\n"));
 124
 125   return debug_bfd;
 126 }
 127
 128 /* Common code for finding BFDs of a given build-id.  This function
 129    works with both debuginfo files (SUFFIX == ".debug") and executable
 130    files (SUFFIX == "").  */
 131
 132 static gdb_bfd_ref_ptr
 133 build_id_to_bfd_suffix (size_t build_id_len, const bfd_byte *build_id,
 134                         const char *suffix)
 135 {
 136   /* Keep backward compatibility so that DEBUG_FILE_DIRECTORY being "" will
 137      cause "/.build-id/..." lookups.  */
 138
 139   std::vector<gdb::unique_xmalloc_ptr<char>> debugdir_vec
 140     = dirnames_to_char_ptr_vec (debug_file_directory.c_str ());
 141
 142   for (const gdb::unique_xmalloc_ptr<char> &debugdir : debugdir_vec)
 143     {
 144       const gdb_byte *data = build_id;
 145       size_t size = build_id_len;
 146
 147       /* Compute where the file named after the build-id would be.
 148
 149          If debugdir is "/usr/lib/debug" and the build-id is abcdef, this will
 150          give "/usr/lib/debug/.build-id/ab/cdef.debug".  */
 151       std::string link = debugdir.get ();
 152       link += "/.build-id/";
 153
 154       if (size > 0)
 155         {
 156           size--;
 157           string_appendf (link, "%02x/", (unsigned) *data++);
 158         }
 159
 160       while (size-- > 0)
 161         string_appendf (link, "%02x", (unsigned) *data++);
 162
 163       link += suffix;
 164
 165       gdb_bfd_ref_ptr debug_bfd
 166         = build_id_to_debug_bfd_1 (link, build_id_len, build_id);
 167       if (debug_bfd != NULL)
 168         return debug_bfd;
 169
 170       /* Try to look under the sysroot as well.  If the sysroot is
 171          "/the/sysroot", it will give
 172          "/the/sysroot/usr/lib/debug/.build-id/ab/cdef.debug".  */
 173
 174       if (!gdb_sysroot.empty ())
 175         {
 176           link = gdb_sysroot + link;
 177           debug_bfd = build_id_to_debug_bfd_1 (link, build_id_len, build_id);
 178           if (debug_bfd != NULL)
 179             return debug_bfd;
 180         }
 181     }
 182
 183   return {};
 184 }
 185
 186 /* See build-id.h.  */
 187
 188 gdb_bfd_ref_ptr
 189 build_id_to_debug_bfd (size_t build_id_len, const bfd_byte *build_id)
 190 {
 191   return build_id_to_bfd_suffix (build_id_len, build_id, ".debug");
 192 }
 193
 194 /* See build-id.h.  */
 195
 196 gdb_bfd_ref_ptr
 197 build_id_to_exec_bfd (size_t build_id_len, const bfd_byte *build_id)
 198 {
 199   return build_id_to_bfd_suffix (build_id_len, build_id, "");
 200 }
 201
 202 /* See build-id.h.  */
 203
 204 std::string
 205 find_separate_debug_file_by_buildid (struct objfile *objfile)
 206 {
 207   const struct bfd_build_id *build_id;
 208
 209   build_id = build_id_bfd_get (objfile->obfd.get ());
 210   if (build_id != NULL)
 211     {
 212       if (separate_debug_file_debug)
 213         gdb_printf (gdb_stdlog,
 214                     _("\nLooking for separate debug info (build-id) for "
 215                       "%s\n"), objfile_name (objfile));
 216
 217       gdb_bfd_ref_ptr abfd (build_id_to_debug_bfd (build_id->size,
 218                                                    build_id->data));
 219       /* Prevent looping on a stripped .debug file.  */
 220       if (abfd != NULL
 221           && filename_cmp (bfd_get_filename (abfd.get ()),
 222                            objfile_name (objfile)) == 0)
 223         warning (_("\"%s\": separate debug info file has no debug info"),
 224                  bfd_get_filename (abfd.get ()));
 225       else if (abfd != NULL)
 226         return std::string (bfd_get_filename (abfd.get ()));
 227     }
 228
 229   return std::string ();
 230 }