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
  22 /* Standard C includes.  */
  23 #include <stdlib.h>
  24
  25 /* Standard C++ includes.  */
  26 #include <string>
  27
  28 /* Local non-gdb includes.  */
  29 #include "build-id.h"
  30 #include "cli/cli-cmds.h"
  31 #include "command.h"
  32 #include "common/pathstuff.h"
  33 #include "common/scoped_mmap.h"
  34 #include "common/selftest.h"
  35 #include "dwarf-index-cache.h"
  36 #include "dwarf-index-write.h"
  37 #include "dwarf2read.h"
  38 #include "objfiles.h"
  39
  40 /* When set to 1, show debug messages about the index cache.  */
  41 static int debug_index_cache = 0;
  42
  43 /* The index cache directory, used for "set/show index-cache directory".  */
  44 static char *index_cache_directory = NULL;
  45
  46 /* See dwarf-index.cache.h.  */
  47 index_cache global_index_cache;
  48
  49 /* set/show index-cache commands.  */
  50 static cmd_list_element *set_index_cache_prefix_list;
  51 static cmd_list_element *show_index_cache_prefix_list;
  52
  53 /* Default destructor of index_cache_resource.  */
  54 index_cache_resource::~index_cache_resource () = default;
  55
  56 /* See dwarf-index-cache.h.  */
  57
  58 void
  59 index_cache::set_directory (std::string dir)
  60 {
  61   gdb_assert (!dir.empty ());
  62
  63   m_dir = std::move (dir);
  64
  65   if (debug_index_cache)
  66     printf_unfiltered ("index cache: 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   if (debug_index_cache)
  75     printf_unfiltered ("index cache: enabling (%s)\n", m_dir.c_str ());
  76
  77   m_enabled = true;
  78 }
  79
  80 /* See dwarf-index-cache.h.  */
  81
  82 void
  83 index_cache::disable ()
  84 {
  85   if (debug_index_cache)
  86     printf_unfiltered ("index cache: disabling\n");
  87
  88   m_enabled = false;
  89 }
  90
  91 /* See dwarf-index-cache.h.  */
  92
  93 void
  94 index_cache::store (struct dwarf2_per_objfile *dwarf2_per_objfile)
  95 {
  96   objfile *obj = dwarf2_per_objfile->objfile;
  97
  98   if (!enabled ())
  99     return;
 100
 101   const bfd_build_id *build_id = build_id_bfd_get (obj->obfd);
 102   if (build_id == nullptr)
 103     {
 104       if (debug_index_cache)
 105         printf_unfiltered ("index cache: objfile %s has no build id\n",
 106                            objfile_name (obj));
 107       return;
 108     }
 109
 110   if (m_dir.empty ())
 111     {
 112       warning (_("The index cache directory name is empty, skipping store."));
 113       return;
 114     }
 115
 116   std::string build_id_str = build_id_to_string (build_id);
 117
 118   TRY
 119     {
 120       /* Try to create the containing directory.  */
 121       if (!mkdir_recursive (m_dir.c_str ()))
 122         {
 123           warning (_("index cache: could not make cache directory: %s\n"),
 124                    safe_strerror (errno));
 125           return;
 126         }
 127
 128       if (debug_index_cache)
 129         printf_unfiltered ("index cache: writing index cache for objfile %s\n",
 130                          objfile_name (obj));
 131
 132       /* Write the index itself to the directory, using the build id as the
 133          filename.  */
 134       write_psymtabs_to_index (dwarf2_per_objfile, m_dir.c_str (),
 135                                build_id_str.c_str (), dw_index_kind::GDB_INDEX);
 136     }
 137   CATCH (except, RETURN_MASK_ERROR)
 138     {
 139       if (debug_index_cache)
 140         printf_unfiltered ("index cache: couldn't store index cache for objfile "
 141                          "%s: %s", objfile_name (obj), except.message);
 142     }
 143   END_CATCH
 144 }
 145
 146 #if HAVE_SYS_MMAN_H
 147
 148 /* Hold the resources for an mmapped index file.  */
 149
 150 struct index_cache_resource_mmap final : public index_cache_resource
 151 {
 152   /* Try to mmap FILENAME.  Throw an exception on failure, including if the
 153      file doesn't exist. */
 154   index_cache_resource_mmap (const char *filename)
 155     : mapping (mmap_file (filename))
 156   {}
 157
 158   scoped_mmap mapping;
 159 };
 160
 161 /* See dwarf-index-cache.h.  */
 162
 163 gdb::array_view<const gdb_byte>
 164 index_cache::lookup_gdb_index (const bfd_build_id *build_id,
 165                                std::unique_ptr<index_cache_resource> *resource)
 166 {
 167   if (!enabled ())
 168     return {};
 169
 170   if (m_dir.empty ())
 171     {
 172       warning (_("The index cache directory name is empty, skipping cache "
 173                  "lookup."));
 174       return {};
 175     }
 176
 177   /* Compute where we would expect a gdb index file for this build id to be.  */
 178   std::string filename = make_index_filename (build_id, INDEX4_SUFFIX);
 179
 180   TRY
 181     {
 182       if (debug_index_cache)
 183         printf_unfiltered ("index cache: trying to read %s\n",
 184                            filename.c_str ());
 185
 186       /* Try to map that file.  */
 187       index_cache_resource_mmap *mmap_resource
 188         = new index_cache_resource_mmap (filename.c_str ());
 189
 190       /* Yay, it worked!  Hand the resource to the caller.  */
 191       resource->reset (mmap_resource);
 192
 193       return gdb::array_view<const gdb_byte>
 194           ((const gdb_byte *) mmap_resource->mapping.get (),
 195            mmap_resource->mapping.size ());
 196     }
 197   CATCH (except, RETURN_MASK_ERROR)
 198     {
 199       if (debug_index_cache)
 200         printf_unfiltered ("index cache: couldn't read %s: %s\n",
 201                          filename.c_str (), except.message);
 202     }
 203   END_CATCH
 204
 205   return {};
 206 }
 207
 208 #else /* !HAVE_SYS_MMAN_H */
 209
 210 /* See dwarf-index-cache.h.  This is a no-op on unsupported systems.  */
 211
 212 gdb::array_view<const gdb_byte>
 213 index_cache::lookup_gdb_index (const bfd_build_id *build_id,
 214                                std::unique_ptr<index_cache_resource> *resource)
 215 {
 216   return {};
 217 }
 218
 219 #endif
 220
 221 /* See dwarf-index-cache.h.  */
 222
 223 std::string
 224 index_cache::make_index_filename (const bfd_build_id *build_id,
 225                                   const char *suffix) const
 226 {
 227   std::string build_id_str = build_id_to_string (build_id);
 228
 229   return m_dir + SLASH_STRING + build_id_str + suffix;
 230 }
 231
 232 /* "set index-cache" handler.  */
 233
 234 static void
 235 set_index_cache_command (const char *arg, int from_tty)
 236 {
 237   printf_unfiltered (_("\
 238 Missing arguments.  See \"help set index-cache\" for help.\n"));
 239 }
 240
 241 /* True when we are executing "show index-cache".  This is used to improve the
 242    printout a little bit.  */
 243 static bool in_show_index_cache_command = false;
 244
 245 /* "show index-cache" handler.  */
 246
 247 static void
 248 show_index_cache_command (const char *arg, int from_tty)
 249 {
 250   /* Note that we are executing "show index-cache".  */
 251   auto restore_flag = make_scoped_restore (&in_show_index_cache_command, true);
 252
 253   /* Call all "show index-cache" subcommands.  */
 254   cmd_show_list (show_index_cache_prefix_list, from_tty, "");
 255
 256   printf_unfiltered ("\n");
 257   printf_unfiltered
 258     (_("The index cache is currently %s.\n"),
 259      global_index_cache.enabled () ? _("enabled") : _("disabled"));
 260 }
 261
 262 /* "set index-cache on" handler.  */
 263
 264 static void
 265 set_index_cache_on_command (const char *arg, int from_tty)
 266 {
 267   global_index_cache.enable ();
 268 }
 269
 270 /* "set index-cache off" handler.  */
 271
 272 static void
 273 set_index_cache_off_command (const char *arg, int from_tty)
 274 {
 275   global_index_cache.disable ();
 276 }
 277
 278 /* "set index-cache directory" handler.  */
 279
 280 static void
 281 set_index_cache_directory_command (const char *arg, int from_tty,
 282                                    cmd_list_element *element)
 283 {
 284   /* Make sure the index cache directory is absolute and tilde-expanded.  */
 285   gdb::unique_xmalloc_ptr<char> abs (gdb_abspath (index_cache_directory));
 286   xfree (index_cache_directory);
 287   index_cache_directory = abs.release ();
 288   global_index_cache.set_directory (index_cache_directory);
 289 }
 290
 291 /* "show index-cache stats" handler.  */
 292
 293 static void
 294 show_index_cache_stats_command (const char *arg, int from_tty)
 295 {
 296   const char *indent = "";
 297
 298   /* If this command is invoked through "show index-cache", make the display a
 299      bit nicer.  */
 300   if (in_show_index_cache_command)
 301     {
 302       indent = "  ";
 303       printf_unfiltered ("\n");
 304     }
 305
 306   printf_unfiltered (_("%s  Cache hits (this session): %u\n"),
 307                      indent, global_index_cache.n_hits ());
 308   printf_unfiltered (_("%sCache misses (this session): %u\n"),
 309                      indent, global_index_cache.n_misses ());
 310 }
 311
 312 void
 313 _initialize_index_cache ()
 314 {
 315   /* Set the default index cache directory.  */
 316   std::string cache_dir = get_standard_cache_dir ();
 317   if (!cache_dir.empty ())
 318     {
 319       index_cache_directory = xstrdup (cache_dir.c_str ());
 320       global_index_cache.set_directory (std::move (cache_dir));
 321     }
 322   else
 323     warning (_("Couldn't determine a path for the index cache directory."));
 324
 325   /* set index-cache */
 326   add_prefix_cmd ("index-cache", class_files, set_index_cache_command,
 327                   _("Set index-cache options"), &set_index_cache_prefix_list,
 328                   "set index-cache ", false, &setlist);
 329
 330   /* show index-cache */
 331   add_prefix_cmd ("index-cache", class_files, show_index_cache_command,
 332                   _("Show index-cache options"), &show_index_cache_prefix_list,
 333                   "show index-cache ", false, &showlist);
 334
 335   /* set index-cache on */
 336   add_cmd ("on", class_files, set_index_cache_on_command,
 337            _("Enable the index cache."), &set_index_cache_prefix_list);
 338
 339   /* set index-cache off */
 340   add_cmd ("off", class_files, set_index_cache_off_command,
 341            _("Disable the index cache."), &set_index_cache_prefix_list);
 342
 343   /* set index-cache directory */
 344   add_setshow_filename_cmd ("directory", class_files, &index_cache_directory,
 345                             _("Set the directory of the index cache."),
 346                             _("Show the directory of the index cache."),
 347                             NULL,
 348                             set_index_cache_directory_command, NULL,
 349                             &set_index_cache_prefix_list,
 350                             &show_index_cache_prefix_list);
 351
 352   /* show index-cache stats */
 353   add_cmd ("stats", class_files, show_index_cache_stats_command,
 354            _("Show some stats about the index cache."),
 355            &show_index_cache_prefix_list);
 356
 357   /* set debug index-cache */
 358   add_setshow_boolean_cmd ("index-cache", class_maintenance,
 359                            &debug_index_cache,
 360                            _("Set display of index-cache debug messages."),
 361                            _("Show display of index-cache debug messages."),
 362                            _("\
 363 When non-zero, debugging output for the index cache is displayed."),
 364                             NULL, NULL,
 365                             &setdebuglist, &showdebuglist);
 366 }