gdb/dwarf-index-cache.c

   1 /* Caching of GDB/DWARF index files.
   2
   3    Copyright (C) 1994-2018 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 "common/scoped_mmap.h"
  27 #include "common/pathstuff.h"
  28 #include "dwarf-index-write.h"
  29 #include "dwarf2read.h"
  30 #include "objfiles.h"
  31 #include "selftest.h"
  32 #include <string>
  33 #include <stdlib.h>
  34
  35 /* When set to 1, show debug messages about the index cache.  */
  36 static int debug_index_cache = 0;
  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   const bfd_build_id *build_id = build_id_bfd_get (obj->obfd);
  97   if (build_id == nullptr)
  98     {
  99       if (debug_index_cache)
 100         printf_unfiltered ("index cache: objfile %s has no build id\n",
 101                            objfile_name (obj));
 102       return;
 103     }
 104
 105   if (m_dir.empty ())
 106     {
 107       warning (_("The index cache directory name is empty, skipping store."));
 108       return;
 109     }
 110
 111   std::string build_id_str = build_id_to_string (build_id);
 112
 113   TRY
 114     {
 115       /* Try to create the containing directory.  */
 116       if (!mkdir_recursive (m_dir.c_str ()))
 117         {
 118           warning (_("index cache: could not make cache directory: %s\n"),
 119                    safe_strerror (errno));
 120           return;
 121         }
 122
 123       if (debug_index_cache)
 124         printf_unfiltered ("index cache: writing index cache for objfile %s\n",
 125                          objfile_name (obj));
 126
 127       /* Write the index itself to the directory, using the build id as the
 128          filename.  */
 129       write_psymtabs_to_index (dwarf2_per_objfile, m_dir.c_str (),
 130                                build_id_str.c_str (), dw_index_kind::GDB_INDEX);
 131     }
 132   CATCH (except, RETURN_MASK_ERROR)
 133     {
 134       if (debug_index_cache)
 135         printf_unfiltered ("index cache: couldn't store index cache for objfile "
 136                          "%s: %s", objfile_name (obj), except.message);
 137     }
 138   END_CATCH
 139 }
 140
 141 #if HAVE_SYS_MMAN_H
 142
 143 /* Hold the resources for an mmapped index file.  */
 144
 145 struct index_cache_resource_mmap final : public index_cache_resource
 146 {
 147   /* Try to mmap FILENAME.  Throw an exception on failure, including if the
 148      file doesn't exist. */
 149   index_cache_resource_mmap (const char *filename)
 150     : mapping (mmap_file (filename))
 151   {}
 152
 153   scoped_mmap mapping;
 154 };
 155
 156 /* See dwarf-index-cache.h.  */
 157
 158 gdb::array_view<const gdb_byte>
 159 index_cache::lookup_gdb_index (const bfd_build_id *build_id,
 160                                std::unique_ptr<index_cache_resource> *resource)
 161 {
 162   if (!enabled ())
 163     return {};
 164
 165   if (m_dir.empty ())
 166     {
 167       warning (_("The index cache directory name is empty, skipping cache "
 168                  "lookup."));
 169       return {};
 170     }
 171
 172   /* Compute where we would expect a gdb index file for this build id to be.  */
 173   std::string filename = make_index_filename (build_id, INDEX4_SUFFIX);
 174
 175   TRY
 176     {
 177       if (debug_index_cache)
 178         printf_unfiltered ("index cache: trying to read %s\n",
 179                            filename.c_str ());
 180
 181       /* Try to map that file.  */
 182       index_cache_resource_mmap *mmap_resource
 183         = new index_cache_resource_mmap (filename.c_str ());
 184
 185       /* Yay, it worked!  Hand the resource to the caller.  */
 186       resource->reset (mmap_resource);
 187
 188       return gdb::array_view<const gdb_byte>
 189           ((const gdb_byte *) mmap_resource->mapping.get (),
 190            mmap_resource->mapping.size ());
 191     }
 192   CATCH (except, RETURN_MASK_ERROR)
 193     {
 194       if (debug_index_cache)
 195         printf_unfiltered ("index cache: couldn't read %s: %s\n",
 196                          filename.c_str (), except.message);
 197     }
 198   END_CATCH
 199
 200   return {};
 201 }
 202
 203 #else /* !HAVE_SYS_MMAN_H */
 204
 205 /* See dwarf-index-cache.h.  This is a no-op on unsupported systems.  */
 206
 207 gdb::array_view<const gdb_byte>
 208 index_cache::lookup_gdb_index (const bfd_build_id *build_id,
 209                                std::unique_ptr<index_cache_resource> *resource)
 210 {
 211   return {};
 212 }
 213
 214 #endif
 215
 216 /* See dwarf-index-cache.h.  */
 217
 218 std::string
 219 index_cache::make_index_filename (const bfd_build_id *build_id,
 220                                   const char *suffix) const
 221 {
 222   std::string build_id_str = build_id_to_string (build_id);
 223
 224   return m_dir + SLASH_STRING + build_id_str + suffix;
 225 }
 226
 227 /* "set index-cache" handler.  */
 228
 229 static void
 230 set_index_cache_command (const char *arg, int from_tty)
 231 {
 232   printf_unfiltered (_("\
 233 Missing arguments.  See \"help set index-cache\" for help.\n"));
 234 }
 235
 236 /* True when we are executing "show index-cache".  This is used to improve the
 237    printout a little bit.  */
 238 static bool in_show_index_cache_command = false;
 239
 240 /* "show index-cache" handler.  */
 241
 242 static void
 243 show_index_cache_command (const char *arg, int from_tty)
 244 {
 245   /* Note that we are executing "show index-cache".  */
 246   auto restore_flag = make_scoped_restore (&in_show_index_cache_command, true);
 247
 248   /* Call all "show index-cache" subcommands.  */
 249   cmd_show_list (show_index_cache_prefix_list, from_tty, "");
 250
 251   printf_unfiltered ("\n");
 252   printf_unfiltered
 253     (_("The index cache is currently %s.\n"),
 254      global_index_cache.enabled () ? _("enabled") : _("disabled"));
 255 }
 256
 257 /* "set index-cache on" handler.  */
 258
 259 static void
 260 set_index_cache_on_command (const char *arg, int from_tty)
 261 {
 262   global_index_cache.enable ();
 263 }
 264
 265 /* "set index-cache off" handler.  */
 266
 267 static void
 268 set_index_cache_off_command (const char *arg, int from_tty)
 269 {
 270   global_index_cache.disable ();
 271 }
 272
 273 /* "set index-cache directory" handler.  */
 274
 275 static void
 276 set_index_cache_directory_command (const char *arg, int from_tty,
 277                                    cmd_list_element *element)
 278 {
 279   /* Make sure the index cache directory is absolute and tilde-expanded.  */
 280   gdb::unique_xmalloc_ptr<char> abs (gdb_abspath (index_cache_directory));
 281   xfree (index_cache_directory);
 282   index_cache_directory = abs.release ();
 283   global_index_cache.set_directory (index_cache_directory);
 284 }
 285
 286 /* "show index-cache stats" handler.  */
 287
 288 static void
 289 show_index_cache_stats_command (const char *arg, int from_tty)
 290 {
 291   const char *indent = "";
 292
 293   /* If this command is invoked through "show index-cache", make the display a
 294      bit nicer.  */
 295   if (in_show_index_cache_command)
 296     {
 297       indent = "  ";
 298       printf_unfiltered ("\n");
 299     }
 300
 301   printf_unfiltered (_("%s  Cache hits (this session): %u\n"),
 302                      indent, global_index_cache.n_hits ());
 303   printf_unfiltered (_("%sCache misses (this session): %u\n"),
 304                      indent, global_index_cache.n_misses ());
 305 }
 306
 307 void
 308 _initialize_index_cache ()
 309 {
 310   /* Set the default index cache directory.  */
 311   std::string cache_dir = get_standard_cache_dir ();
 312   if (!cache_dir.empty ())
 313     {
 314       index_cache_directory = xstrdup (cache_dir.c_str ());
 315       global_index_cache.set_directory (std::move (cache_dir));
 316     }
 317   else
 318     warning (_("Couldn't determine a path for the index cache directory."));
 319
 320   /* set index-cache */
 321   add_prefix_cmd ("index-cache", class_files, set_index_cache_command,
 322                   _("Set index-cache options"), &set_index_cache_prefix_list,
 323                   "set index-cache ", false, &setlist);
 324
 325   /* show index-cache */
 326   add_prefix_cmd ("index-cache", class_files, show_index_cache_command,
 327                   _("Show index-cache options"), &show_index_cache_prefix_list,
 328                   "show index-cache ", false, &showlist);
 329
 330   /* set index-cache on */
 331   add_cmd ("on", class_files, set_index_cache_on_command,
 332            _("Enable the index cache."), &set_index_cache_prefix_list);
 333
 334   /* set index-cache off */
 335   add_cmd ("off", class_files, set_index_cache_off_command,
 336            _("Disable the index cache."), &set_index_cache_prefix_list);
 337
 338   /* set index-cache directory */
 339   add_setshow_filename_cmd ("directory", class_files, &index_cache_directory,
 340                             _("Set the directory of the index cache."),
 341                             _("Show the directory of the index cache."),
 342                             NULL,
 343                             set_index_cache_directory_command, NULL,
 344                             &set_index_cache_prefix_list,
 345                             &show_index_cache_prefix_list);
 346
 347   /* show index-cache stats */
 348   add_cmd ("stats", class_files, show_index_cache_stats_command,
 349            _("Show some stats about the index cache."),
 350            &show_index_cache_prefix_list);
 351
 352   /* set debug index-cache */
 353   add_setshow_boolean_cmd ("index-cache", class_maintenance,
 354                            &debug_index_cache,
 355                            _("Set display of index-cache debug messages."),
 356                            _("Show display of index-cache debug messages."),
 357                            _("\
 358 When non-zero, debugging output for the index cache is displayed."),
 359                             NULL, NULL,
 360                             &setdebuglist, &showdebuglist);
 361 }