gdb/build-id.c

   1 /* build-id-related functions.
   2
   3    Copyright (C) 1991-2020 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       printf_unfiltered (_("  Trying %s..."), link.c_str ());
  80       gdb_flush (gdb_stdout);
  81     }
  82
  83   /* lrealpath() is expensive even for the usually non-existent files.  */
  84   gdb::unique_xmalloc_ptr<char> filename;
  85   if (access (link.c_str (), F_OK) == 0)
  86     filename.reset (lrealpath (link.c_str ()));
  87
  88   if (filename == NULL)
  89     {
  90       if (separate_debug_file_debug)
  91         printf_unfiltered (_(" no, unable to compute real path\n"));
  92
  93       return {};
  94     }
  95
  96   /* We expect to be silent on the non-existing files.  */
  97   gdb_bfd_ref_ptr debug_bfd = gdb_bfd_open (filename.get (), gnutarget);
  98
  99   if (debug_bfd == NULL)
 100     {
 101       if (separate_debug_file_debug)
 102         printf_unfiltered (_(" no, unable to open.\n"));
 103
 104       return {};
 105     }
 106
 107   if (!build_id_verify (debug_bfd.get(), build_id_len, build_id))
 108     {
 109       if (separate_debug_file_debug)
 110         printf_unfiltered (_(" no, build-id does not match.\n"));
 111
 112       return {};
 113     }
 114
 115   if (separate_debug_file_debug)
 116     printf_unfiltered (_(" yes!\n"));
 117
 118   return debug_bfd;
 119 }
 120
 121 /* Common code for finding BFDs of a given build-id.  This function
 122    works with both debuginfo files (SUFFIX == ".debug") and executable
 123    files (SUFFIX == "").  */
 124
 125 static gdb_bfd_ref_ptr
 126 build_id_to_bfd_suffix (size_t build_id_len, const bfd_byte *build_id,
 127                         const char *suffix)
 128 {
 129   /* Keep backward compatibility so that DEBUG_FILE_DIRECTORY being "" will
 130      cause "/.build-id/..." lookups.  */
 131
 132   std::vector<gdb::unique_xmalloc_ptr<char>> debugdir_vec
 133     = dirnames_to_char_ptr_vec (debug_file_directory);
 134
 135   for (const gdb::unique_xmalloc_ptr<char> &debugdir : debugdir_vec)
 136     {
 137       const gdb_byte *data = build_id;
 138       size_t size = build_id_len;
 139
 140       /* Compute where the file named after the build-id would be.
 141
 142          If debugdir is "/usr/lib/debug" and the build-id is abcdef, this will
 143          give "/usr/lib/debug/.build-id/ab/cdef.debug".  */
 144       std::string link = debugdir.get ();
 145       link += "/.build-id/";
 146
 147       if (size > 0)
 148         {
 149           size--;
 150           string_appendf (link, "%02x/", (unsigned) *data++);
 151         }
 152
 153       while (size-- > 0)
 154         string_appendf (link, "%02x", (unsigned) *data++);
 155
 156       link += suffix;
 157
 158       gdb_bfd_ref_ptr debug_bfd
 159         = build_id_to_debug_bfd_1 (link, build_id_len, build_id);
 160       if (debug_bfd != NULL)
 161         return debug_bfd;
 162
 163       /* Try to look under the sysroot as well.  If the sysroot is
 164          "/the/sysroot", it will give
 165          "/the/sysroot/usr/lib/debug/.build-id/ab/cdef.debug".
 166
 167          Don't do it if the sysroot is the target system ("target:").  It
 168          could work in theory, but the lrealpath in build_id_to_debug_bfd_1
 169          only works with local paths.  */
 170       if (strcmp (gdb_sysroot, TARGET_SYSROOT_PREFIX) != 0)
 171         {
 172           link = gdb_sysroot + link;
 173           debug_bfd = build_id_to_debug_bfd_1 (link, build_id_len, build_id);
 174           if (debug_bfd != NULL)
 175             return debug_bfd;
 176         }
 177     }
 178
 179   return {};
 180 }
 181
 182 /* See build-id.h.  */
 183
 184 gdb_bfd_ref_ptr
 185 build_id_to_debug_bfd (size_t build_id_len, const bfd_byte *build_id)
 186 {
 187   return build_id_to_bfd_suffix (build_id_len, build_id, ".debug");
 188 }
 189
 190 /* See build-id.h.  */
 191
 192 gdb_bfd_ref_ptr
 193 build_id_to_exec_bfd (size_t build_id_len, const bfd_byte *build_id)
 194 {
 195   return build_id_to_bfd_suffix (build_id_len, build_id, "");
 196 }
 197
 198 /* See build-id.h.  */
 199
 200 std::string
 201 find_separate_debug_file_by_buildid (struct objfile *objfile)
 202 {
 203   const struct bfd_build_id *build_id;
 204
 205   build_id = build_id_bfd_get (objfile->obfd);
 206   if (build_id != NULL)
 207     {
 208       if (separate_debug_file_debug)
 209         printf_unfiltered (_("\nLooking for separate debug info (build-id) for "
 210                              "%s\n"), objfile_name (objfile));
 211
 212       gdb_bfd_ref_ptr abfd (build_id_to_debug_bfd (build_id->size,
 213                                                    build_id->data));
 214       /* Prevent looping on a stripped .debug file.  */
 215       if (abfd != NULL
 216           && filename_cmp (bfd_get_filename (abfd.get ()),
 217                            objfile_name (objfile)) == 0)
 218         warning (_("\"%s\": separate debug info file has no debug info"),
 219                  bfd_get_filename (abfd.get ()));
 220       else if (abfd != NULL)
 221         return std::string (bfd_get_filename (abfd.get ()));
 222     }
 223
 224   return std::string ();
 225 }