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\n", 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)\n", 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\n");
  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   /* Get build id of objfile.  */
 100   const bfd_build_id *build_id = build_id_bfd_get (obj->obfd);
 101   if (build_id == nullptr)
 102     {
 103       index_cache_debug ("objfile %s has no build id\n",
 104                          objfile_name (obj));
 105       return;
 106     }
 107
 108   std::string build_id_str = build_id_to_string (build_id);
 109
 110   /* Get build id of dwz file, if present.  */
 111   gdb::optional<std::string> dwz_build_id_str;
 112   const dwz_file *dwz = dwarf2_get_dwz_file (per_objfile->per_bfd);
 113   const char *dwz_build_id_ptr = NULL;
 114
 115   if (dwz != nullptr)
 116     {
 117       const bfd_build_id *dwz_build_id = build_id_bfd_get (dwz->dwz_bfd.get ());
 118
 119       if (dwz_build_id == nullptr)
 120         {
 121           index_cache_debug ("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       index_cache_debug ("writing index cache for objfile %s\n",
 147                          objfile_name (obj));
 148
 149       /* Write the index itself to the directory, using the build id as the
 150          filename.  */
 151       write_psymtabs_to_index (per_objfile, m_dir.c_str (),
 152                                build_id_str.c_str (), dwz_build_id_ptr,
 153                                dw_index_kind::GDB_INDEX);
 154     }
 155   catch (const gdb_exception_error &except)
 156     {
 157       index_cache_debug ("couldn't store index cache for objfile "
 158                          "%s: %s", objfile_name (obj), except.what ());
 159     }
 160 }
 161
 162 #if HAVE_SYS_MMAN_H
 163
 164 /* Hold the resources for an mmapped index file.  */
 165
 166 struct index_cache_resource_mmap final : public index_cache_resource
 167 {
 168   /* Try to mmap FILENAME.  Throw an exception on failure, including if the
 169      file doesn't exist. */
 170   index_cache_resource_mmap (const char *filename)
 171     : mapping (mmap_file (filename))
 172   {}
 173
 174   scoped_mmap mapping;
 175 };
 176
 177 /* See dwarf-index-cache.h.  */
 178
 179 gdb::array_view<const gdb_byte>
 180 index_cache::lookup_gdb_index (const bfd_build_id *build_id,
 181                                std::unique_ptr<index_cache_resource> *resource)
 182 {
 183   if (!enabled ())
 184     return {};
 185
 186   if (m_dir.empty ())
 187     {
 188       warning (_("The index cache directory name is empty, skipping cache "
 189                  "lookup."));
 190       return {};
 191     }
 192
 193   /* Compute where we would expect a gdb index file for this build id to be.  */
 194   std::string filename = make_index_filename (build_id, INDEX4_SUFFIX);
 195
 196   try
 197     {
 198       index_cache_debug ("trying to read %s\n",
 199                          filename.c_str ());
 200
 201       /* Try to map that file.  */
 202       index_cache_resource_mmap *mmap_resource
 203         = new index_cache_resource_mmap (filename.c_str ());
 204
 205       /* Yay, it worked!  Hand the resource to the caller.  */
 206       resource->reset (mmap_resource);
 207
 208       return gdb::array_view<const gdb_byte>
 209           ((const gdb_byte *) mmap_resource->mapping.get (),
 210            mmap_resource->mapping.size ());
 211     }
 212   catch (const gdb_exception_error &except)
 213     {
 214       index_cache_debug ("couldn't read %s: %s\n",
 215                          filename.c_str (), except.what ());
 216     }
 217
 218   return {};
 219 }
 220
 221 #else /* !HAVE_SYS_MMAN_H */
 222
 223 /* See dwarf-index-cache.h.  This is a no-op on unsupported systems.  */
 224
 225 gdb::array_view<const gdb_byte>
 226 index_cache::lookup_gdb_index (const bfd_build_id *build_id,
 227                                std::unique_ptr<index_cache_resource> *resource)
 228 {
 229   return {};
 230 }
 231
 232 #endif
 233
 234 /* See dwarf-index-cache.h.  */
 235
 236 std::string
 237 index_cache::make_index_filename (const bfd_build_id *build_id,
 238                                   const char *suffix) const
 239 {
 240   std::string build_id_str = build_id_to_string (build_id);
 241
 242   return m_dir + SLASH_STRING + build_id_str + suffix;
 243 }
 244
 245 /* True when we are executing "show index-cache".  This is used to improve the
 246    printout a little bit.  */
 247 static bool in_show_index_cache_command = false;
 248
 249 /* "show index-cache" handler.  */
 250
 251 static void
 252 show_index_cache_command (const char *arg, int from_tty)
 253 {
 254   /* Note that we are executing "show index-cache".  */
 255   auto restore_flag = make_scoped_restore (&in_show_index_cache_command, true);
 256
 257   /* Call all "show index-cache" subcommands.  */
 258   cmd_show_list (show_index_cache_prefix_list, from_tty);
 259
 260   printf_filtered ("\n");
 261   printf_filtered
 262     (_("The index cache is currently %s.\n"),
 263      global_index_cache.enabled () ? _("enabled") : _("disabled"));
 264 }
 265
 266 /* "set/show index-cache enabled" set callback.  */
 267
 268 static void
 269 set_index_cache_enabled_command (bool value)
 270 {
 271   if (value)
 272     global_index_cache.enable ();
 273   else
 274     global_index_cache.disable ();
 275 }
 276
 277 /* "set/show index-cache enabled" get callback.  */
 278
 279 static bool
 280 get_index_cache_enabled_command ()
 281 {
 282   return global_index_cache.enabled ();
 283 }
 284
 285 /* "set/show index-cache enabled" show callback.  */
 286
 287 static void
 288 show_index_cache_enabled_command (ui_file *stream, int from_tty,
 289                                   cmd_list_element *cmd, const char *value)
 290 {
 291   fprintf_filtered (stream, _("The index cache is %s.\n"), value);
 292 }
 293
 294 /* "set index-cache directory" handler.  */
 295
 296 static void
 297 set_index_cache_directory_command (const char *arg, int from_tty,
 298                                    cmd_list_element *element)
 299 {
 300   /* Make sure the index cache directory is absolute and tilde-expanded.  */
 301   gdb::unique_xmalloc_ptr<char> abs
 302     = gdb_abspath (index_cache_directory.c_str ());
 303   index_cache_directory = abs.get ();
 304   global_index_cache.set_directory (index_cache_directory);
 305 }
 306
 307 /* "show index-cache stats" handler.  */
 308
 309 static void
 310 show_index_cache_stats_command (const char *arg, int from_tty)
 311 {
 312   const char *indent = "";
 313
 314   /* If this command is invoked through "show index-cache", make the display a
 315      bit nicer.  */
 316   if (in_show_index_cache_command)
 317     {
 318       indent = "  ";
 319       printf_filtered ("\n");
 320     }
 321
 322   printf_filtered (_("%s  Cache hits (this session): %u\n"),
 323                    indent, global_index_cache.n_hits ());
 324   printf_filtered (_("%sCache misses (this session): %u\n"),
 325                    indent, global_index_cache.n_misses ());
 326 }
 327
 328 void _initialize_index_cache ();
 329 void
 330 _initialize_index_cache ()
 331 {
 332   /* Set the default index cache directory.  */
 333   std::string cache_dir = get_standard_cache_dir ();
 334   if (!cache_dir.empty ())
 335     {
 336       index_cache_directory = cache_dir;
 337       global_index_cache.set_directory (std::move (cache_dir));
 338     }
 339   else
 340     warning (_("Couldn't determine a path for the index cache directory."));
 341
 342   /* set index-cache */
 343   add_basic_prefix_cmd ("index-cache", class_files,
 344                         _("Set index-cache options."),
 345                         &set_index_cache_prefix_list,
 346                         false, &setlist);
 347
 348   /* show index-cache */
 349   add_prefix_cmd ("index-cache", class_files, show_index_cache_command,
 350                   _("Show index-cache options."), &show_index_cache_prefix_list,
 351                   false, &showlist);
 352
 353   /* set/show index-cache enabled */
 354   set_show_commands setshow_index_cache_enabled_cmds
 355     = add_setshow_boolean_cmd ("enabled", class_files,
 356                                _("Enable the index cache."),
 357                                _("Show whether the index cache is enabled."),
 358                                _("When on, enable the use of the index cache."),
 359                                set_index_cache_enabled_command,
 360                                get_index_cache_enabled_command,
 361                                show_index_cache_enabled_command,
 362                                &set_index_cache_prefix_list,
 363                                &show_index_cache_prefix_list);
 364
 365   /* set index-cache on */
 366   cmd_list_element *set_index_cache_on_cmd
 367     = add_alias_cmd ("on", setshow_index_cache_enabled_cmds.set, class_files,
 368                      false, &set_index_cache_prefix_list);
 369   deprecate_cmd (set_index_cache_on_cmd, "set index-cache enabled on");
 370   set_index_cache_on_cmd->default_args = "on";
 371
 372   /* set index-cache off */
 373   cmd_list_element *set_index_cache_off_cmd
 374     = add_alias_cmd ("off", setshow_index_cache_enabled_cmds.set, class_files,
 375                      false, &set_index_cache_prefix_list);
 376   deprecate_cmd (set_index_cache_off_cmd, "set index-cache enabled off");
 377   set_index_cache_off_cmd->default_args = "off";
 378
 379   /* set index-cache directory */
 380   add_setshow_filename_cmd ("directory", class_files, &index_cache_directory,
 381                             _("Set the directory of the index cache."),
 382                             _("Show the directory of the index cache."),
 383                             NULL,
 384                             set_index_cache_directory_command, NULL,
 385                             &set_index_cache_prefix_list,
 386                             &show_index_cache_prefix_list);
 387
 388   /* show index-cache stats */
 389   add_cmd ("stats", class_files, show_index_cache_stats_command,
 390            _("Show some stats about the index cache."),
 391            &show_index_cache_prefix_list);
 392
 393   /* set debug index-cache */
 394   add_setshow_boolean_cmd ("index-cache", class_maintenance,
 395                            &debug_index_cache,
 396                            _("Set display of index-cache debug messages."),
 397                            _("Show display of index-cache debug messages."),
 398                            _("\
 399 When non-zero, debugging output for the index cache is displayed."),
 400                             NULL, NULL,
 401                             &setdebuglist, &showdebuglist);
 402 }