gdb/dwarf-index-cache.c

   1 /* Caching of GDB/DWARF index files.
   2
   3    Copyright (C) 1994-2019 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 "common/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 (const gdb_exception_error &except)
 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.what ());
 137     }
 138 }
 139
 140 #if HAVE_SYS_MMAN_H
 141
 142 /* Hold the resources for an mmapped index file.  */
 143
 144 struct index_cache_resource_mmap final : public index_cache_resource
 145 {
 146   /* Try to mmap FILENAME.  Throw an exception on failure, including if the
 147      file doesn't exist. */
 148   index_cache_resource_mmap (const char *filename)
 149     : mapping (mmap_file (filename))
 150   {}
 151
 152   scoped_mmap mapping;
 153 };
 154
 155 /* See dwarf-index-cache.h.  */
 156
 157 gdb::array_view<const gdb_byte>
 158 index_cache::lookup_gdb_index (const bfd_build_id *build_id,
 159                                std::unique_ptr<index_cache_resource> *resource)
 160 {
 161   if (!enabled ())
 162     return {};
 163
 164   if (m_dir.empty ())
 165     {
 166       warning (_("The index cache directory name is empty, skipping cache "
 167                  "lookup."));
 168       return {};
 169     }
 170
 171   /* Compute where we would expect a gdb index file for this build id to be.  */
 172   std::string filename = make_index_filename (build_id, INDEX4_SUFFIX);
 173
 174   try
 175     {
 176       if (debug_index_cache)
 177         printf_unfiltered ("index cache: trying to read %s\n",
 178                            filename.c_str ());
 179
 180       /* Try to map that file.  */
 181       index_cache_resource_mmap *mmap_resource
 182         = new index_cache_resource_mmap (filename.c_str ());
 183
 184       /* Yay, it worked!  Hand the resource to the caller.  */
 185       resource->reset (mmap_resource);
 186
 187       return gdb::array_view<const gdb_byte>
 188           ((const gdb_byte *) mmap_resource->mapping.get (),
 189            mmap_resource->mapping.size ());
 190     }
 191   catch (const gdb_exception_error &except)
 192     {
 193       if (debug_index_cache)
 194         printf_unfiltered ("index cache: couldn't read %s: %s\n",
 195                            filename.c_str (), except.what ());
 196     }
 197
 198   return {};
 199 }
 200
 201 #else /* !HAVE_SYS_MMAN_H */
 202
 203 /* See dwarf-index-cache.h.  This is a no-op on unsupported systems.  */
 204
 205 gdb::array_view<const gdb_byte>
 206 index_cache::lookup_gdb_index (const bfd_build_id *build_id,
 207                                std::unique_ptr<index_cache_resource> *resource)
 208 {
 209   return {};
 210 }
 211
 212 #endif
 213
 214 /* See dwarf-index-cache.h.  */
 215
 216 std::string
 217 index_cache::make_index_filename (const bfd_build_id *build_id,
 218                                   const char *suffix) const
 219 {
 220   std::string build_id_str = build_id_to_string (build_id);
 221
 222   return m_dir + SLASH_STRING + build_id_str + suffix;
 223 }
 224
 225 /* "set index-cache" handler.  */
 226
 227 static void
 228 set_index_cache_command (const char *arg, int from_tty)
 229 {
 230   printf_unfiltered (_("\
 231 Missing arguments.  See \"help set index-cache\" for help.\n"));
 232 }
 233
 234 /* True when we are executing "show index-cache".  This is used to improve the
 235    printout a little bit.  */
 236 static bool in_show_index_cache_command = false;
 237
 238 /* "show index-cache" handler.  */
 239
 240 static void
 241 show_index_cache_command (const char *arg, int from_tty)
 242 {
 243   /* Note that we are executing "show index-cache".  */
 244   auto restore_flag = make_scoped_restore (&in_show_index_cache_command, true);
 245
 246   /* Call all "show index-cache" subcommands.  */
 247   cmd_show_list (show_index_cache_prefix_list, from_tty, "");
 248
 249   printf_unfiltered ("\n");
 250   printf_unfiltered
 251     (_("The index cache is currently %s.\n"),
 252      global_index_cache.enabled () ? _("enabled") : _("disabled"));
 253 }
 254
 255 /* "set index-cache on" handler.  */
 256
 257 static void
 258 set_index_cache_on_command (const char *arg, int from_tty)
 259 {
 260   global_index_cache.enable ();
 261 }
 262
 263 /* "set index-cache off" handler.  */
 264
 265 static void
 266 set_index_cache_off_command (const char *arg, int from_tty)
 267 {
 268   global_index_cache.disable ();
 269 }
 270
 271 /* "set index-cache directory" handler.  */
 272
 273 static void
 274 set_index_cache_directory_command (const char *arg, int from_tty,
 275                                    cmd_list_element *element)
 276 {
 277   /* Make sure the index cache directory is absolute and tilde-expanded.  */
 278   gdb::unique_xmalloc_ptr<char> abs (gdb_abspath (index_cache_directory));
 279   xfree (index_cache_directory);
 280   index_cache_directory = abs.release ();
 281   global_index_cache.set_directory (index_cache_directory);
 282 }
 283
 284 /* "show index-cache stats" handler.  */
 285
 286 static void
 287 show_index_cache_stats_command (const char *arg, int from_tty)
 288 {
 289   const char *indent = "";
 290
 291   /* If this command is invoked through "show index-cache", make the display a
 292      bit nicer.  */
 293   if (in_show_index_cache_command)
 294     {
 295       indent = "  ";
 296       printf_unfiltered ("\n");
 297     }
 298
 299   printf_unfiltered (_("%s  Cache hits (this session): %u\n"),
 300                      indent, global_index_cache.n_hits ());
 301   printf_unfiltered (_("%sCache misses (this session): %u\n"),
 302                      indent, global_index_cache.n_misses ());
 303 }
 304
 305 void
 306 _initialize_index_cache ()
 307 {
 308   /* Set the default index cache directory.  */
 309   std::string cache_dir = get_standard_cache_dir ();
 310   if (!cache_dir.empty ())
 311     {
 312       index_cache_directory = xstrdup (cache_dir.c_str ());
 313       global_index_cache.set_directory (std::move (cache_dir));
 314     }
 315   else
 316     warning (_("Couldn't determine a path for the index cache directory."));
 317
 318   /* set index-cache */
 319   add_prefix_cmd ("index-cache", class_files, set_index_cache_command,
 320                   _("Set index-cache options"), &set_index_cache_prefix_list,
 321                   "set index-cache ", false, &setlist);
 322
 323   /* show index-cache */
 324   add_prefix_cmd ("index-cache", class_files, show_index_cache_command,
 325                   _("Show index-cache options"), &show_index_cache_prefix_list,
 326                   "show index-cache ", false, &showlist);
 327
 328   /* set index-cache on */
 329   add_cmd ("on", class_files, set_index_cache_on_command,
 330            _("Enable the index cache."), &set_index_cache_prefix_list);
 331
 332   /* set index-cache off */
 333   add_cmd ("off", class_files, set_index_cache_off_command,
 334            _("Disable the index cache."), &set_index_cache_prefix_list);
 335
 336   /* set index-cache directory */
 337   add_setshow_filename_cmd ("directory", class_files, &index_cache_directory,
 338                             _("Set the directory of the index cache."),
 339                             _("Show the directory of the index cache."),
 340                             NULL,
 341                             set_index_cache_directory_command, NULL,
 342                             &set_index_cache_prefix_list,
 343                             &show_index_cache_prefix_list);
 344
 345   /* show index-cache stats */
 346   add_cmd ("stats", class_files, show_index_cache_stats_command,
 347            _("Show some stats about the index cache."),
 348            &show_index_cache_prefix_list);
 349
 350   /* set debug index-cache */
 351   add_setshow_boolean_cmd ("index-cache", class_maintenance,
 352                            &debug_index_cache,
 353                            _("Set display of index-cache debug messages."),
 354                            _("Show display of index-cache debug messages."),
 355                            _("\
 356 When non-zero, debugging output for the index cache is displayed."),
 357                             NULL, NULL,
 358                             &setdebuglist, &showdebuglist);
 359 }