gdb/dwarf-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 "dwarf-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 "dwarf-index-write.h"
  29 #include "dwarf2read.h"
  30 #include "objfiles.h"
  31 #include "gdbsupport/selftest.h"
  32 #include <string>
  33 #include <stdlib.h>
  34
  35 /* When set to true, show debug messages about the index cache.  */
  36 static bool debug_index_cache = false;
  37
  38 /* The index cache directory, used for "set/show index-cache directory".  */
  39 static char *index_cache_directory = NULL;
  40
  41 /* See dwarf-index.cache.h.  */
  42 index_cache global_index_cache;
  43
  44 /* set/show index-cache commands.  */
  45 static cmd_list_element *set_index_cache_prefix_list;
  46 static cmd_list_element *show_index_cache_prefix_list;
  47
  48 /* Default destructor of index_cache_resource.  */
  49 index_cache_resource::~index_cache_resource () = default;
  50
  51 /* See dwarf-index-cache.h.  */
  52
  53 void
  54 index_cache::set_directory (std::string dir)
  55 {
  56   gdb_assert (!dir.empty ());
  57
  58   m_dir = std::move (dir);
  59
  60   if (debug_index_cache)
  61     printf_unfiltered ("index cache: now using directory %s\n", m_dir.c_str ());
  62 }
  63
  64 /* See dwarf-index-cache.h.  */
  65
  66 void
  67 index_cache::enable ()
  68 {
  69   if (debug_index_cache)
  70     printf_unfiltered ("index cache: enabling (%s)\n", m_dir.c_str ());
  71
  72   m_enabled = true;
  73 }
  74
  75 /* See dwarf-index-cache.h.  */
  76
  77 void
  78 index_cache::disable ()
  79 {
  80   if (debug_index_cache)
  81     printf_unfiltered ("index cache: disabling\n");
  82
  83   m_enabled = false;
  84 }
  85
  86 /* See dwarf-index-cache.h.  */
  87
  88 void
  89 index_cache::store (struct dwarf2_per_objfile *dwarf2_per_objfile)
  90 {
  91   objfile *obj = dwarf2_per_objfile->objfile;
  92
  93   if (!enabled ())
  94     return;
  95
  96   /* Get build id of objfile.  */
  97   const bfd_build_id *build_id = build_id_bfd_get (obj->obfd);
  98   if (build_id == nullptr)
  99     {
 100       if (debug_index_cache)
 101         printf_unfiltered ("index cache: objfile %s has no build id\n",
 102                            objfile_name (obj));
 103       return;
 104     }
 105
 106   std::string build_id_str = build_id_to_string (build_id);
 107
 108   /* Get build id of dwz file, if present.  */
 109   gdb::optional<std::string> dwz_build_id_str;
 110   const dwz_file *dwz = dwarf2_get_dwz_file (dwarf2_per_objfile);
 111   const char *dwz_build_id_ptr = NULL;
 112
 113   if (dwz != nullptr)
 114     {
 115       const bfd_build_id *dwz_build_id = build_id_bfd_get (dwz->dwz_bfd.get ());
 116
 117       if (dwz_build_id == nullptr)
 118         {
 119           if (debug_index_cache)
 120             printf_unfiltered ("index cache: dwz objfile %s has no build id\n",
 121                                dwz->filename ());
 122           return;
 123         }
 124
 125       dwz_build_id_str = build_id_to_string (dwz_build_id);
 126       dwz_build_id_ptr = dwz_build_id_str->c_str ();
 127     }
 128
 129   if (m_dir.empty ())
 130     {
 131       warning (_("The index cache directory name is empty, skipping store."));
 132       return;
 133     }
 134
 135   try
 136     {
 137       /* Try to create the containing directory.  */
 138       if (!mkdir_recursive (m_dir.c_str ()))
 139         {
 140           warning (_("index cache: could not make cache directory: %s"),
 141                    safe_strerror (errno));
 142           return;
 143         }
 144
 145       if (debug_index_cache)
 146         printf_unfiltered ("index cache: 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 (dwarf2_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       if (debug_index_cache)
 158         printf_unfiltered ("index cache: couldn't store index cache for objfile "
 159                            "%s: %s", objfile_name (obj), except.what ());
 160     }
 161 }
 162
 163 #if HAVE_SYS_MMAN_H
 164
 165 /* Hold the resources for an mmapped index file.  */
 166
 167 struct index_cache_resource_mmap final : public index_cache_resource
 168 {
 169   /* Try to mmap FILENAME.  Throw an exception on failure, including if the
 170      file doesn't exist. */
 171   index_cache_resource_mmap (const char *filename)
 172     : mapping (mmap_file (filename))
 173   {}
 174
 175   scoped_mmap mapping;
 176 };
 177
 178 /* See dwarf-index-cache.h.  */
 179
 180 gdb::array_view<const gdb_byte>
 181 index_cache::lookup_gdb_index (const bfd_build_id *build_id,
 182                                std::unique_ptr<index_cache_resource> *resource)
 183 {
 184   if (!enabled ())
 185     return {};
 186
 187   if (m_dir.empty ())
 188     {
 189       warning (_("The index cache directory name is empty, skipping cache "
 190                  "lookup."));
 191       return {};
 192     }
 193
 194   /* Compute where we would expect a gdb index file for this build id to be.  */
 195   std::string filename = make_index_filename (build_id, INDEX4_SUFFIX);
 196
 197   try
 198     {
 199       if (debug_index_cache)
 200         printf_unfiltered ("index cache: trying to read %s\n",
 201                            filename.c_str ());
 202
 203       /* Try to map that file.  */
 204       index_cache_resource_mmap *mmap_resource
 205         = new index_cache_resource_mmap (filename.c_str ());
 206
 207       /* Yay, it worked!  Hand the resource to the caller.  */
 208       resource->reset (mmap_resource);
 209
 210       return gdb::array_view<const gdb_byte>
 211           ((const gdb_byte *) mmap_resource->mapping.get (),
 212            mmap_resource->mapping.size ());
 213     }
 214   catch (const gdb_exception_error &except)
 215     {
 216       if (debug_index_cache)
 217         printf_unfiltered ("index cache: couldn't read %s: %s\n",
 218                            filename.c_str (), except.what ());
 219     }
 220
 221   return {};
 222 }
 223
 224 #else /* !HAVE_SYS_MMAN_H */
 225
 226 /* See dwarf-index-cache.h.  This is a no-op on unsupported systems.  */
 227
 228 gdb::array_view<const gdb_byte>
 229 index_cache::lookup_gdb_index (const bfd_build_id *build_id,
 230                                std::unique_ptr<index_cache_resource> *resource)
 231 {
 232   return {};
 233 }
 234
 235 #endif
 236
 237 /* See dwarf-index-cache.h.  */
 238
 239 std::string
 240 index_cache::make_index_filename (const bfd_build_id *build_id,
 241                                   const char *suffix) const
 242 {
 243   std::string build_id_str = build_id_to_string (build_id);
 244
 245   return m_dir + SLASH_STRING + build_id_str + suffix;
 246 }
 247
 248 /* "set index-cache" handler.  */
 249
 250 static void
 251 set_index_cache_command (const char *arg, int from_tty)
 252 {
 253   printf_unfiltered (_("\
 254 Missing arguments.  See \"help set index-cache\" for help.\n"));
 255 }
 256
 257 /* True when we are executing "show index-cache".  This is used to improve the
 258    printout a little bit.  */
 259 static bool in_show_index_cache_command = false;
 260
 261 /* "show index-cache" handler.  */
 262
 263 static void
 264 show_index_cache_command (const char *arg, int from_tty)
 265 {
 266   /* Note that we are executing "show index-cache".  */
 267   auto restore_flag = make_scoped_restore (&in_show_index_cache_command, true);
 268
 269   /* Call all "show index-cache" subcommands.  */
 270   cmd_show_list (show_index_cache_prefix_list, from_tty, "");
 271
 272   printf_unfiltered ("\n");
 273   printf_unfiltered
 274     (_("The index cache is currently %s.\n"),
 275      global_index_cache.enabled () ? _("enabled") : _("disabled"));
 276 }
 277
 278 /* "set index-cache on" handler.  */
 279
 280 static void
 281 set_index_cache_on_command (const char *arg, int from_tty)
 282 {
 283   global_index_cache.enable ();
 284 }
 285
 286 /* "set index-cache off" handler.  */
 287
 288 static void
 289 set_index_cache_off_command (const char *arg, int from_tty)
 290 {
 291   global_index_cache.disable ();
 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 (gdb_abspath (index_cache_directory));
 302   xfree (index_cache_directory);
 303   index_cache_directory = abs.release ();
 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_unfiltered ("\n");
 320     }
 321
 322   printf_unfiltered (_("%s  Cache hits (this session): %u\n"),
 323                      indent, global_index_cache.n_hits ());
 324   printf_unfiltered (_("%sCache misses (this session): %u\n"),
 325                      indent, global_index_cache.n_misses ());
 326 }
 327
 328 void
 329 _initialize_index_cache ()
 330 {
 331   /* Set the default index cache directory.  */
 332   std::string cache_dir = get_standard_cache_dir ();
 333   if (!cache_dir.empty ())
 334     {
 335       index_cache_directory = xstrdup (cache_dir.c_str ());
 336       global_index_cache.set_directory (std::move (cache_dir));
 337     }
 338   else
 339     warning (_("Couldn't determine a path for the index cache directory."));
 340
 341   /* set index-cache */
 342   add_prefix_cmd ("index-cache", class_files, set_index_cache_command,
 343                   _("Set index-cache options."), &set_index_cache_prefix_list,
 344                   "set index-cache ", false, &setlist);
 345
 346   /* show index-cache */
 347   add_prefix_cmd ("index-cache", class_files, show_index_cache_command,
 348                   _("Show index-cache options."), &show_index_cache_prefix_list,
 349                   "show index-cache ", false, &showlist);
 350
 351   /* set index-cache on */
 352   add_cmd ("on", class_files, set_index_cache_on_command,
 353            _("Enable the index cache."), &set_index_cache_prefix_list);
 354
 355   /* set index-cache off */
 356   add_cmd ("off", class_files, set_index_cache_off_command,
 357            _("Disable the index cache."), &set_index_cache_prefix_list);
 358
 359   /* set index-cache directory */
 360   add_setshow_filename_cmd ("directory", class_files, &index_cache_directory,
 361                             _("Set the directory of the index cache."),
 362                             _("Show the directory of the index cache."),
 363                             NULL,
 364                             set_index_cache_directory_command, NULL,
 365                             &set_index_cache_prefix_list,
 366                             &show_index_cache_prefix_list);
 367
 368   /* show index-cache stats */
 369   add_cmd ("stats", class_files, show_index_cache_stats_command,
 370            _("Show some stats about the index cache."),
 371            &show_index_cache_prefix_list);
 372
 373   /* set debug index-cache */
 374   add_setshow_boolean_cmd ("index-cache", class_maintenance,
 375                            &debug_index_cache,
 376                            _("Set display of index-cache debug messages."),
 377                            _("Show display of index-cache debug messages."),
 378                            _("\
 379 When non-zero, debugging output for the index cache is displayed."),
 380                             NULL, NULL,
 381                             &setdebuglist, &showdebuglist);
 382 }