gdb/dwarf2/index-cache.c

   1 /* Caching of GDB/DWARF index files.
   2
   3    Copyright (C) 1994-2022 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 "dwarf2/index-cache.h"
  22
  23 #include "build-id.h"
  24 #include "cli/cli-cmds.h"
  25 #include "cli/cli-decode.h"
  26 #include "command.h"
  27 #include "gdbsupport/scoped_mmap.h"
  28 #include "gdbsupport/pathstuff.h"
  29 #include "dwarf2/index-write.h"
  30 #include "dwarf2/read.h"
  31 #include "dwarf2/dwz.h"
  32 #include "objfiles.h"
  33 #include "gdbsupport/selftest.h"
  34 #include <string>
  35 #include <stdlib.h>
  36
  37 /* When set to true, show debug messages about the index cache.  */
  38 static bool debug_index_cache = false;
  39
  40 #define index_cache_debug(FMT, ...)                                            \
  41   debug_prefixed_printf_cond_nofunc (debug_index_cache, "index-cache", \
  42                                      FMT, ## __VA_ARGS__)
  43
  44 /* The index cache directory, used for "set/show index-cache directory".  */
  45 static std::string index_cache_directory;
  46
  47 /* See dwarf-index.cache.h.  */
  48 index_cache global_index_cache;
  49
  50 /* set/show index-cache commands.  */
  51 static cmd_list_element *set_index_cache_prefix_list;
  52 static cmd_list_element *show_index_cache_prefix_list;
  53
  54 /* Default destructor of index_cache_resource.  */
  55 index_cache_resource::~index_cache_resource () = default;
  56
  57 /* See dwarf-index-cache.h.  */
  58
  59 void
  60 index_cache::set_directory (std::string dir)
  61 {
  62   gdb_assert (!dir.empty ());
  63
  64   m_dir = std::move (dir);
  65
  66   index_cache_debug ("now using directory %s", m_dir.c_str ());
  67 }
  68
  69 /* See dwarf-index-cache.h.  */
  70
  71 void
  72 index_cache::enable ()
  73 {
  74   index_cache_debug ("enabling (%s)", m_dir.c_str ());
  75
  76   m_enabled = true;
  77 }
  78
  79 /* See dwarf-index-cache.h.  */
  80
  81 void
  82 index_cache::disable ()
  83 {
  84   index_cache_debug ("disabling");
  85
  86   m_enabled = false;
  87 }
  88
  89 /* See dwarf-index-cache.h.  */
  90
  91 void
  92 index_cache::store (dwarf2_per_objfile *per_objfile)
  93 {
  94   objfile *obj = per_objfile->objfile;
  95
  96   if (!enabled ())
  97     return;
  98
  99   /* If the objfile does not correspond to an actual file, skip it.  */
 100   if ((obj->flags & OBJF_NOT_FILENAME) != 0)
 101     return;
 102
 103   /* Get build id of objfile.  */
 104   const bfd_build_id *build_id = build_id_bfd_get (obj->obfd);
 105   if (build_id == nullptr)
 106     {
 107       index_cache_debug ("objfile %s has no build id",
 108                          objfile_name (obj));
 109       return;
 110     }
 111
 112   std::string build_id_str = build_id_to_string (build_id);
 113
 114   /* Get build id of dwz file, if present.  */
 115   gdb::optional<std::string> dwz_build_id_str;
 116   const dwz_file *dwz = dwarf2_get_dwz_file (per_objfile->per_bfd);
 117   const char *dwz_build_id_ptr = NULL;
 118
 119   if (dwz != nullptr)
 120     {
 121       const bfd_build_id *dwz_build_id = build_id_bfd_get (dwz->dwz_bfd.get ());
 122
 123       if (dwz_build_id == nullptr)
 124         {
 125           index_cache_debug ("dwz objfile %s has no build id",
 126                              dwz->filename ());
 127           return;
 128         }
 129
 130       dwz_build_id_str = build_id_to_string (dwz_build_id);
 131       dwz_build_id_ptr = dwz_build_id_str->c_str ();
 132     }
 133
 134   if (m_dir.empty ())
 135     {
 136       warning (_("The index cache directory name is empty, skipping store."));
 137       return;
 138     }
 139
 140   try
 141     {
 142       /* Try to create the containing directory.  */
 143       if (!mkdir_recursive (m_dir.c_str ()))
 144         {
 145           warning (_("index cache: could not make cache directory: %s"),
 146                    safe_strerror (errno));
 147           return;
 148         }
 149
 150       index_cache_debug ("writing index cache for objfile %s",
 151                          objfile_name (obj));
 152
 153       /* Write the index itself to the directory, using the build id as the
 154          filename.  */
 155       write_dwarf_index (per_objfile, m_dir.c_str (),
 156                          build_id_str.c_str (), dwz_build_id_ptr,
 157                          dw_index_kind::GDB_INDEX);
 158     }
 159   catch (const gdb_exception_error &except)
 160     {
 161       index_cache_debug ("couldn't store index cache for objfile %s: %s",
 162                          objfile_name (obj), except.what ());
 163     }
 164 }
 165
 166 #if HAVE_SYS_MMAN_H
 167
 168 /* Hold the resources for an mmapped index file.  */
 169
 170 struct index_cache_resource_mmap final : public index_cache_resource
 171 {
 172   /* Try to mmap FILENAME.  Throw an exception on failure, including if the
 173      file doesn't exist. */
 174   index_cache_resource_mmap (const char *filename)
 175     : mapping (mmap_file (filename))
 176   {}
 177
 178   scoped_mmap mapping;
 179 };
 180
 181 /* See dwarf-index-cache.h.  */
 182
 183 gdb::array_view<const gdb_byte>
 184 index_cache::lookup_gdb_index (const bfd_build_id *build_id,
 185                                std::unique_ptr<index_cache_resource> *resource)
 186 {
 187   if (!enabled ())
 188     return {};
 189
 190   if (m_dir.empty ())
 191     {
 192       warning (_("The index cache directory name is empty, skipping cache "
 193                  "lookup."));
 194       return {};
 195     }
 196
 197   /* Compute where we would expect a gdb index file for this build id to be.  */
 198   std::string filename = make_index_filename (build_id, INDEX4_SUFFIX);
 199
 200   try
 201     {
 202       index_cache_debug ("trying to read %s",
 203                          filename.c_str ());
 204
 205       /* Try to map that file.  */
 206       index_cache_resource_mmap *mmap_resource
 207         = new index_cache_resource_mmap (filename.c_str ());
 208
 209       /* Yay, it worked!  Hand the resource to the caller.  */
 210       resource->reset (mmap_resource);
 211
 212       return gdb::array_view<const gdb_byte>
 213           ((const gdb_byte *) mmap_resource->mapping.get (),
 214            mmap_resource->mapping.size ());
 215     }
 216   catch (const gdb_exception_error &except)
 217     {
 218       index_cache_debug ("couldn't read %s: %s",
 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   gdb_printf ("\n");
 265   gdb_printf
 266     (_("The index cache is currently %s.\n"),
 267      global_index_cache.enabled () ? _("enabled") : _("disabled"));
 268 }
 269
 270 /* "set/show index-cache enabled" set callback.  */
 271
 272 static void
 273 set_index_cache_enabled_command (bool value)
 274 {
 275   if (value)
 276     global_index_cache.enable ();
 277   else
 278     global_index_cache.disable ();
 279 }
 280
 281 /* "set/show index-cache enabled" get callback.  */
 282
 283 static bool
 284 get_index_cache_enabled_command ()
 285 {
 286   return global_index_cache.enabled ();
 287 }
 288
 289 /* "set/show index-cache enabled" show callback.  */
 290
 291 static void
 292 show_index_cache_enabled_command (ui_file *stream, int from_tty,
 293                                   cmd_list_element *cmd, const char *value)
 294 {
 295   gdb_printf (stream, _("The index cache is %s.\n"), value);
 296 }
 297
 298 /* "set index-cache directory" handler.  */
 299
 300 static void
 301 set_index_cache_directory_command (const char *arg, int from_tty,
 302                                    cmd_list_element *element)
 303 {
 304   /* Make sure the index cache directory is absolute and tilde-expanded.  */
 305   index_cache_directory = gdb_abspath (index_cache_directory.c_str ());
 306   global_index_cache.set_directory (index_cache_directory);
 307 }
 308
 309 /* "show index-cache stats" handler.  */
 310
 311 static void
 312 show_index_cache_stats_command (const char *arg, int from_tty)
 313 {
 314   const char *indent = "";
 315
 316   /* If this command is invoked through "show index-cache", make the display a
 317      bit nicer.  */
 318   if (in_show_index_cache_command)
 319     {
 320       indent = "  ";
 321       gdb_printf ("\n");
 322     }
 323
 324   gdb_printf (_("%s  Cache hits (this session): %u\n"),
 325               indent, global_index_cache.n_hits ());
 326   gdb_printf (_("%sCache misses (this session): %u\n"),
 327               indent, global_index_cache.n_misses ());
 328 }
 329
 330 void _initialize_index_cache ();
 331 void
 332 _initialize_index_cache ()
 333 {
 334   /* Set the default index cache directory.  */
 335   std::string cache_dir = get_standard_cache_dir ();
 336   if (!cache_dir.empty ())
 337     {
 338       index_cache_directory = cache_dir;
 339       global_index_cache.set_directory (std::move (cache_dir));
 340     }
 341   else
 342     warning (_("Couldn't determine a path for the index cache directory."));
 343
 344   /* set index-cache */
 345   add_basic_prefix_cmd ("index-cache", class_files,
 346                         _("Set index-cache options."),
 347                         &set_index_cache_prefix_list,
 348                         false, &setlist);
 349
 350   /* show index-cache */
 351   add_prefix_cmd ("index-cache", class_files, show_index_cache_command,
 352                   _("Show index-cache options."), &show_index_cache_prefix_list,
 353                   false, &showlist);
 354
 355   /* set/show index-cache enabled */
 356   set_show_commands setshow_index_cache_enabled_cmds
 357     = add_setshow_boolean_cmd ("enabled", class_files,
 358                                _("Enable the index cache."),
 359                                _("Show whether the index cache is enabled."),
 360                                _("When on, enable the use of the index cache."),
 361                                set_index_cache_enabled_command,
 362                                get_index_cache_enabled_command,
 363                                show_index_cache_enabled_command,
 364                                &set_index_cache_prefix_list,
 365                                &show_index_cache_prefix_list);
 366
 367   /* set index-cache on */
 368   cmd_list_element *set_index_cache_on_cmd
 369     = add_alias_cmd ("on", setshow_index_cache_enabled_cmds.set, class_files,
 370                      false, &set_index_cache_prefix_list);
 371   deprecate_cmd (set_index_cache_on_cmd, "set index-cache enabled on");
 372   set_index_cache_on_cmd->default_args = "on";
 373
 374   /* set index-cache off */
 375   cmd_list_element *set_index_cache_off_cmd
 376     = add_alias_cmd ("off", setshow_index_cache_enabled_cmds.set, class_files,
 377                      false, &set_index_cache_prefix_list);
 378   deprecate_cmd (set_index_cache_off_cmd, "set index-cache enabled off");
 379   set_index_cache_off_cmd->default_args = "off";
 380
 381   /* set index-cache directory */
 382   add_setshow_filename_cmd ("directory", class_files, &index_cache_directory,
 383                             _("Set the directory of the index cache."),
 384                             _("Show the directory of the index cache."),
 385                             NULL,
 386                             set_index_cache_directory_command, NULL,
 387                             &set_index_cache_prefix_list,
 388                             &show_index_cache_prefix_list);
 389
 390   /* show index-cache stats */
 391   add_cmd ("stats", class_files, show_index_cache_stats_command,
 392            _("Show some stats about the index cache."),
 393            &show_index_cache_prefix_list);
 394
 395   /* set debug index-cache */
 396   add_setshow_boolean_cmd ("index-cache", class_maintenance,
 397                            &debug_index_cache,
 398                            _("Set display of index-cache debug messages."),
 399                            _("Show display of index-cache debug messages."),
 400                            _("\
 401 When non-zero, debugging output for the index cache is displayed."),
 402                             NULL, NULL,
 403                             &setdebuglist, &showdebuglist);
 404 }