gdb/dwarf2/index-cache.c

   1 /* Caching of GDB/DWARF index files.
   2
   3    Copyright (C) 1994-2020 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 "dwarf2/index-cache.h"
  22
  23 #include "build-id.h"
  24 #include "cli/cli-cmds.h"
  25 #include "command.h"
  26 #include "gdbsupport/scoped_mmap.h"
  27 #include "gdbsupport/pathstuff.h"
  28 #include "dwarf2/index-write.h"
  29 #include "dwarf2/read.h"
  30 #include "dwarf2/dwz.h"
  31 #include "objfiles.h"
  32 #include "gdbsupport/selftest.h"
  33 #include <string>
  34 #include <stdlib.h>
  35
  36 /* When set to true, show debug messages about the index cache.  */
  37 static bool debug_index_cache = false;
  38
  39 /* The index cache directory, used for "set/show index-cache directory".  */
  40 static char *index_cache_directory = NULL;
  41
  42 /* See dwarf-index.cache.h.  */
  43 index_cache global_index_cache;
  44
  45 /* set/show index-cache commands.  */
  46 static cmd_list_element *set_index_cache_prefix_list;
  47 static cmd_list_element *show_index_cache_prefix_list;
  48
  49 /* Default destructor of index_cache_resource.  */
  50 index_cache_resource::~index_cache_resource () = default;
  51
  52 /* See dwarf-index-cache.h.  */
  53
  54 void
  55 index_cache::set_directory (std::string dir)
  56 {
  57   gdb_assert (!dir.empty ());
  58
  59   m_dir = std::move (dir);
  60
  61   if (debug_index_cache)
  62     printf_unfiltered ("index cache: now using directory %s\n", m_dir.c_str ());
  63 }
  64
  65 /* See dwarf-index-cache.h.  */
  66
  67 void
  68 index_cache::enable ()
  69 {
  70   if (debug_index_cache)
  71     printf_unfiltered ("index cache: enabling (%s)\n", m_dir.c_str ());
  72
  73   m_enabled = true;
  74 }
  75
  76 /* See dwarf-index-cache.h.  */
  77
  78 void
  79 index_cache::disable ()
  80 {
  81   if (debug_index_cache)
  82     printf_unfiltered ("index cache: disabling\n");
  83
  84   m_enabled = false;
  85 }
  86
  87 /* See dwarf-index-cache.h.  */
  88
  89 void
  90 index_cache::store (dwarf2_per_objfile *per_objfile)
  91 {
  92   objfile *obj = per_objfile->objfile;
  93
  94   if (!enabled ())
  95     return;
  96
  97   /* Get build id of objfile.  */
  98   const bfd_build_id *build_id = build_id_bfd_get (obj->obfd);
  99   if (build_id == nullptr)
 100     {
 101       if (debug_index_cache)
 102         printf_unfiltered ("index cache: objfile %s has no build id\n",
 103                            objfile_name (obj));
 104       return;
 105     }
 106
 107   std::string build_id_str = build_id_to_string (build_id);
 108
 109   /* Get build id of dwz file, if present.  */
 110   gdb::optional<std::string> dwz_build_id_str;
 111   const dwz_file *dwz = dwarf2_get_dwz_file (per_objfile->per_bfd);
 112   const char *dwz_build_id_ptr = NULL;
 113
 114   if (dwz != nullptr)
 115     {
 116       const bfd_build_id *dwz_build_id = build_id_bfd_get (dwz->dwz_bfd.get ());
 117
 118       if (dwz_build_id == nullptr)
 119         {
 120           if (debug_index_cache)
 121             printf_unfiltered ("index cache: dwz objfile %s has no build id\n",
 122                                dwz->filename ());
 123           return;
 124         }
 125
 126       dwz_build_id_str = build_id_to_string (dwz_build_id);
 127       dwz_build_id_ptr = dwz_build_id_str->c_str ();
 128     }
 129
 130   if (m_dir.empty ())
 131     {
 132       warning (_("The index cache directory name is empty, skipping store."));
 133       return;
 134     }
 135
 136   try
 137     {
 138       /* Try to create the containing directory.  */
 139       if (!mkdir_recursive (m_dir.c_str ()))
 140         {
 141           warning (_("index cache: could not make cache directory: %s"),
 142                    safe_strerror (errno));
 143           return;
 144         }
 145
 146       if (debug_index_cache)
 147         printf_unfiltered ("index cache: writing index cache for objfile %s\n",
 148                            objfile_name (obj));
 149
 150       /* Write the index itself to the directory, using the build id as the
 151          filename.  */
 152       write_psymtabs_to_index (per_objfile, m_dir.c_str (),
 153                                build_id_str.c_str (), dwz_build_id_ptr,
 154                                dw_index_kind::GDB_INDEX);
 155     }
 156   catch (const gdb_exception_error &except)
 157     {
 158       if (debug_index_cache)
 159         printf_unfiltered ("index cache: couldn't store index cache for objfile "
 160                            "%s: %s", objfile_name (obj), except.what ());
 161     }
 162 }
 163
 164 #if HAVE_SYS_MMAN_H
 165
 166 /* Hold the resources for an mmapped index file.  */
 167
 168 struct index_cache_resource_mmap final : public index_cache_resource
 169 {
 170   /* Try to mmap FILENAME.  Throw an exception on failure, including if the
 171      file doesn't exist. */
 172   index_cache_resource_mmap (const char *filename)
 173     : mapping (mmap_file (filename))
 174   {}
 175
 176   scoped_mmap mapping;
 177 };
 178
 179 /* See dwarf-index-cache.h.  */
 180
 181 gdb::array_view<const gdb_byte>
 182 index_cache::lookup_gdb_index (const bfd_build_id *build_id,
 183                                std::unique_ptr<index_cache_resource> *resource)
 184 {
 185   if (!enabled ())
 186     return {};
 187
 188   if (m_dir.empty ())
 189     {
 190       warning (_("The index cache directory name is empty, skipping cache "
 191                  "lookup."));
 192       return {};
 193     }
 194
 195   /* Compute where we would expect a gdb index file for this build id to be.  */
 196   std::string filename = make_index_filename (build_id, INDEX4_SUFFIX);
 197
 198   try
 199     {
 200       if (debug_index_cache)
 201         printf_unfiltered ("index cache: trying to read %s\n",
 202                            filename.c_str ());
 203
 204       /* Try to map that file.  */
 205       index_cache_resource_mmap *mmap_resource
 206         = new index_cache_resource_mmap (filename.c_str ());
 207
 208       /* Yay, it worked!  Hand the resource to the caller.  */
 209       resource->reset (mmap_resource);
 210
 211       return gdb::array_view<const gdb_byte>
 212           ((const gdb_byte *) mmap_resource->mapping.get (),
 213            mmap_resource->mapping.size ());
 214     }
 215   catch (const gdb_exception_error &except)
 216     {
 217       if (debug_index_cache)
 218         printf_unfiltered ("index cache: couldn't read %s: %s\n",
 219                            filename.c_str (), except.what ());
 220     }
 221
 222   return {};
 223 }
 224
 225 #else /* !HAVE_SYS_MMAN_H */
 226
 227 /* See dwarf-index-cache.h.  This is a no-op on unsupported systems.  */
 228
 229 gdb::array_view<const gdb_byte>
 230 index_cache::lookup_gdb_index (const bfd_build_id *build_id,
 231                                std::unique_ptr<index_cache_resource> *resource)
 232 {
 233   return {};
 234 }
 235
 236 #endif
 237
 238 /* See dwarf-index-cache.h.  */
 239
 240 std::string
 241 index_cache::make_index_filename (const bfd_build_id *build_id,
 242                                   const char *suffix) const
 243 {
 244   std::string build_id_str = build_id_to_string (build_id);
 245
 246   return m_dir + SLASH_STRING + build_id_str + suffix;
 247 }
 248
 249 /* True when we are executing "show index-cache".  This is used to improve the
 250    printout a little bit.  */
 251 static bool in_show_index_cache_command = false;
 252
 253 /* "show index-cache" handler.  */
 254
 255 static void
 256 show_index_cache_command (const char *arg, int from_tty)
 257 {
 258   /* Note that we are executing "show index-cache".  */
 259   auto restore_flag = make_scoped_restore (&in_show_index_cache_command, true);
 260
 261   /* Call all "show index-cache" subcommands.  */
 262   cmd_show_list (show_index_cache_prefix_list, from_tty);
 263
 264   printf_unfiltered ("\n");
 265   printf_unfiltered
 266     (_("The index cache is currently %s.\n"),
 267      global_index_cache.enabled () ? _("enabled") : _("disabled"));
 268 }
 269
 270 /* "set index-cache on" handler.  */
 271
 272 static void
 273 set_index_cache_on_command (const char *arg, int from_tty)
 274 {
 275   global_index_cache.enable ();
 276 }
 277
 278 /* "set index-cache off" handler.  */
 279
 280 static void
 281 set_index_cache_off_command (const char *arg, int from_tty)
 282 {
 283   global_index_cache.disable ();
 284 }
 285
 286 /* "set index-cache directory" handler.  */
 287
 288 static void
 289 set_index_cache_directory_command (const char *arg, int from_tty,
 290                                    cmd_list_element *element)
 291 {
 292   /* Make sure the index cache directory is absolute and tilde-expanded.  */
 293   gdb::unique_xmalloc_ptr<char> abs (gdb_abspath (index_cache_directory));
 294   xfree (index_cache_directory);
 295   index_cache_directory = abs.release ();
 296   global_index_cache.set_directory (index_cache_directory);
 297 }
 298
 299 /* "show index-cache stats" handler.  */
 300
 301 static void
 302 show_index_cache_stats_command (const char *arg, int from_tty)
 303 {
 304   const char *indent = "";
 305
 306   /* If this command is invoked through "show index-cache", make the display a
 307      bit nicer.  */
 308   if (in_show_index_cache_command)
 309     {
 310       indent = "  ";
 311       printf_unfiltered ("\n");
 312     }
 313
 314   printf_unfiltered (_("%s  Cache hits (this session): %u\n"),
 315                      indent, global_index_cache.n_hits ());
 316   printf_unfiltered (_("%sCache misses (this session): %u\n"),
 317                      indent, global_index_cache.n_misses ());
 318 }
 319
 320 void _initialize_index_cache ();
 321 void
 322 _initialize_index_cache ()
 323 {
 324   /* Set the default index cache directory.  */
 325   std::string cache_dir = get_standard_cache_dir ();
 326   if (!cache_dir.empty ())
 327     {
 328       index_cache_directory = xstrdup (cache_dir.c_str ());
 329       global_index_cache.set_directory (std::move (cache_dir));
 330     }
 331   else
 332     warning (_("Couldn't determine a path for the index cache directory."));
 333
 334   /* set index-cache */
 335   add_basic_prefix_cmd ("index-cache", class_files,
 336                         _("Set index-cache options."),
 337                         &set_index_cache_prefix_list,
 338                         "set index-cache ", false, &setlist);
 339
 340   /* show index-cache */
 341   add_prefix_cmd ("index-cache", class_files, show_index_cache_command,
 342                   _("Show index-cache options."), &show_index_cache_prefix_list,
 343                   "show index-cache ", false, &showlist);
 344
 345   /* set index-cache on */
 346   add_cmd ("on", class_files, set_index_cache_on_command,
 347            _("Enable the index cache."), &set_index_cache_prefix_list);
 348
 349   /* set index-cache off */
 350   add_cmd ("off", class_files, set_index_cache_off_command,
 351            _("Disable the index cache."), &set_index_cache_prefix_list);
 352
 353   /* set index-cache directory */
 354   add_setshow_filename_cmd ("directory", class_files, &index_cache_directory,
 355                             _("Set the directory of the index cache."),
 356                             _("Show the directory of the index cache."),
 357                             NULL,
 358                             set_index_cache_directory_command, NULL,
 359                             &set_index_cache_prefix_list,
 360                             &show_index_cache_prefix_list);
 361
 362   /* show index-cache stats */
 363   add_cmd ("stats", class_files, show_index_cache_stats_command,
 364            _("Show some stats about the index cache."),
 365            &show_index_cache_prefix_list);
 366
 367   /* set debug index-cache */
 368   add_setshow_boolean_cmd ("index-cache", class_maintenance,
 369                            &debug_index_cache,
 370                            _("Set display of index-cache debug messages."),
 371                            _("Show display of index-cache debug messages."),
 372                            _("\
 373 When non-zero, debugging output for the index cache is displayed."),
 374                             NULL, NULL,
 375                             &setdebuglist, &showdebuglist);
 376 }