libctf/ctf-string.c

   1 /* CTF string table management.
   2    Copyright (C) 2019-2021 Free Software Foundation, Inc.
   3
   4    This file is part of libctf.
   5
   6    libctf is free software; you can redistribute it and/or modify it under
   7    the terms of the GNU General Public License as published by the Free
   8    Software Foundation; either version 3, or (at your option) any later
   9    version.
  10
  11    This program is distributed in the hope that it will be useful, but
  12    WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  14    See the GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; see the file COPYING.  If not see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <ctf-impl.h>
  21 #include <string.h>
  22
  23 /* Convert an encoded CTF string name into a pointer to a C string, using an
  24   explicit internal strtab rather than the fp-based one.  */
  25 const char *
  26 ctf_strraw_explicit (ctf_dict_t *fp, uint32_t name, ctf_strs_t *strtab)
  27 {
  28   ctf_strs_t *ctsp = &fp->ctf_str[CTF_NAME_STID (name)];
  29
  30   if ((CTF_NAME_STID (name) == CTF_STRTAB_0) && (strtab != NULL))
  31     ctsp = strtab;
  32
  33   /* If this name is in the external strtab, and there is a synthetic strtab,
  34      use it in preference.  */
  35
  36   if (CTF_NAME_STID (name) == CTF_STRTAB_1
  37       && fp->ctf_syn_ext_strtab != NULL)
  38     return ctf_dynhash_lookup (fp->ctf_syn_ext_strtab,
  39                                (void *) (uintptr_t) name);
  40
  41   /* If the name is in the internal strtab, and the offset is beyond the end of
  42      the ctsp->cts_len but below the ctf_str_prov_offset, this is a provisional
  43      string added by ctf_str_add*() but not yet built into a real strtab: get
  44      the value out of the ctf_prov_strtab.  */
  45
  46   if (CTF_NAME_STID (name) == CTF_STRTAB_0
  47       && name >= ctsp->cts_len && name < fp->ctf_str_prov_offset)
  48       return ctf_dynhash_lookup (fp->ctf_prov_strtab,
  49                                  (void *) (uintptr_t) name);
  50
  51   if (ctsp->cts_strs != NULL && CTF_NAME_OFFSET (name) < ctsp->cts_len)
  52     return (ctsp->cts_strs + CTF_NAME_OFFSET (name));
  53
  54   /* String table not loaded or corrupt offset.  */
  55   return NULL;
  56 }
  57
  58 /* Convert an encoded CTF string name into a pointer to a C string by looking
  59   up the appropriate string table buffer and then adding the offset.  */
  60 const char *
  61 ctf_strraw (ctf_dict_t *fp, uint32_t name)
  62 {
  63   return ctf_strraw_explicit (fp, name, NULL);
  64 }
  65
  66 /* Return a guaranteed-non-NULL pointer to the string with the given CTF
  67    name.  */
  68 const char *
  69 ctf_strptr (ctf_dict_t *fp, uint32_t name)
  70 {
  71   const char *s = ctf_strraw (fp, name);
  72   return (s != NULL ? s : "(?)");
  73 }
  74
  75 /* Remove all refs to a given atom.  */
  76 static void
  77 ctf_str_purge_atom_refs (ctf_str_atom_t *atom)
  78 {
  79   ctf_str_atom_ref_t *ref, *next;
  80
  81   for (ref = ctf_list_next (&atom->csa_refs); ref != NULL; ref = next)
  82     {
  83       next = ctf_list_next (ref);
  84       ctf_list_delete (&atom->csa_refs, ref);
  85       free (ref);
  86     }
  87 }
  88
  89 /* Free an atom (only called on ctf_close().)  */
  90 static void
  91 ctf_str_free_atom (void *a)
  92 {
  93   ctf_str_atom_t *atom = a;
  94
  95   ctf_str_purge_atom_refs (atom);
  96   free (atom);
  97 }
  98
  99 /* Create the atoms table.  There is always at least one atom in it, the null
 100    string.  */
 101 int
 102 ctf_str_create_atoms (ctf_dict_t *fp)
 103 {
 104   fp->ctf_str_atoms = ctf_dynhash_create (ctf_hash_string, ctf_hash_eq_string,
 105                                           free, ctf_str_free_atom);
 106   if (fp->ctf_str_atoms == NULL)
 107     return -ENOMEM;
 108
 109   if (!fp->ctf_prov_strtab)
 110     fp->ctf_prov_strtab = ctf_dynhash_create (ctf_hash_integer,
 111                                               ctf_hash_eq_integer,
 112                                               NULL, NULL);
 113   if (!fp->ctf_prov_strtab)
 114     goto oom_prov_strtab;
 115
 116   errno = 0;
 117   ctf_str_add (fp, "");
 118   if (errno == ENOMEM)
 119     goto oom_str_add;
 120
 121   return 0;
 122
 123  oom_str_add:
 124   ctf_dynhash_destroy (fp->ctf_prov_strtab);
 125   fp->ctf_prov_strtab = NULL;
 126  oom_prov_strtab:
 127   ctf_dynhash_destroy (fp->ctf_str_atoms);
 128   fp->ctf_str_atoms = NULL;
 129   return -ENOMEM;
 130 }
 131
 132 /* Destroy the atoms table.  */
 133 void
 134 ctf_str_free_atoms (ctf_dict_t *fp)
 135 {
 136   ctf_dynhash_destroy (fp->ctf_prov_strtab);
 137   ctf_dynhash_destroy (fp->ctf_str_atoms);
 138 }
 139
 140 /* Add a string to the atoms table, copying the passed-in string.  Return the
 141    atom added. Return NULL only when out of memory (and do not touch the
 142    passed-in string in that case).  Possibly augment the ref list with the
 143    passed-in ref.  Possibly add a provisional entry for this string to the
 144    provisional strtab.   */
 145 static ctf_str_atom_t *
 146 ctf_str_add_ref_internal (ctf_dict_t *fp, const char *str,
 147                           int add_ref, int make_provisional, uint32_t *ref)
 148 {
 149   char *newstr = NULL;
 150   ctf_str_atom_t *atom = NULL;
 151   ctf_str_atom_ref_t *aref = NULL;
 152
 153   atom = ctf_dynhash_lookup (fp->ctf_str_atoms, str);
 154
 155   if (add_ref)
 156     {
 157       if ((aref = malloc (sizeof (struct ctf_str_atom_ref))) == NULL)
 158         return NULL;
 159       aref->caf_ref = ref;
 160     }
 161
 162   if (atom)
 163     {
 164       if (add_ref)
 165         {
 166           ctf_list_append (&atom->csa_refs, aref);
 167           fp->ctf_str_num_refs++;
 168         }
 169       return atom;
 170     }
 171
 172   if ((atom = malloc (sizeof (struct ctf_str_atom))) == NULL)
 173     goto oom;
 174   memset (atom, 0, sizeof (struct ctf_str_atom));
 175
 176   if ((newstr = strdup (str)) == NULL)
 177     goto oom;
 178
 179   if (ctf_dynhash_insert (fp->ctf_str_atoms, newstr, atom) < 0)
 180     goto oom;
 181
 182   atom->csa_str = newstr;
 183   atom->csa_snapshot_id = fp->ctf_snapshots;
 184
 185   if (make_provisional)
 186     {
 187       atom->csa_offset = fp->ctf_str_prov_offset;
 188
 189       if (ctf_dynhash_insert (fp->ctf_prov_strtab, (void *) (uintptr_t)
 190                               atom->csa_offset, (void *) atom->csa_str) < 0)
 191         goto oom;
 192
 193       fp->ctf_str_prov_offset += strlen (atom->csa_str) + 1;
 194     }
 195
 196   if (add_ref)
 197     {
 198       ctf_list_append (&atom->csa_refs, aref);
 199       fp->ctf_str_num_refs++;
 200     }
 201   return atom;
 202
 203  oom:
 204   if (newstr)
 205     ctf_dynhash_remove (fp->ctf_str_atoms, newstr);
 206   free (atom);
 207   free (aref);
 208   free (newstr);
 209   return NULL;
 210 }
 211
 212 /* Add a string to the atoms table, without augmenting the ref list for this
 213    string: return a 'provisional offset' which can be used to return this string
 214    until ctf_str_write_strtab is called, or 0 on failure.  (Everywhere the
 215    provisional offset is assigned to should be added as a ref using
 216    ctf_str_add_ref() as well.) */
 217 uint32_t
 218 ctf_str_add (ctf_dict_t *fp, const char *str)
 219 {
 220   ctf_str_atom_t *atom;
 221   if (!str)
 222     return 0;
 223
 224   atom = ctf_str_add_ref_internal (fp, str, FALSE, TRUE, 0);
 225   if (!atom)
 226     return 0;
 227
 228   return atom->csa_offset;
 229 }
 230
 231 /* Like ctf_str_add(), but additionally augment the atom's refs list with the
 232    passed-in ref, whether or not the string is already present.  There is no
 233    attempt to deduplicate the refs list (but duplicates are harmless).  */
 234 uint32_t
 235 ctf_str_add_ref (ctf_dict_t *fp, const char *str, uint32_t *ref)
 236 {
 237   ctf_str_atom_t *atom;
 238   if (!str)
 239     return 0;
 240
 241   atom = ctf_str_add_ref_internal (fp, str, TRUE, TRUE, ref);
 242   if (!atom)
 243     return 0;
 244
 245   return atom->csa_offset;
 246 }
 247
 248 /* Add an external strtab reference at OFFSET.  Returns zero if the addition
 249    failed, nonzero otherwise.  */
 250 int
 251 ctf_str_add_external (ctf_dict_t *fp, const char *str, uint32_t offset)
 252 {
 253   ctf_str_atom_t *atom;
 254   if (!str)
 255     return 0;
 256
 257   atom = ctf_str_add_ref_internal (fp, str, FALSE, FALSE, 0);
 258   if (!atom)
 259     return 0;
 260
 261   atom->csa_external_offset = CTF_SET_STID (offset, CTF_STRTAB_1);
 262
 263   if (!fp->ctf_syn_ext_strtab)
 264     fp->ctf_syn_ext_strtab = ctf_dynhash_create (ctf_hash_integer,
 265                                                  ctf_hash_eq_integer,
 266                                                  NULL, NULL);
 267   if (!fp->ctf_syn_ext_strtab)
 268     {
 269       ctf_set_errno (fp, ENOMEM);
 270       return 0;
 271     }
 272
 273   if (ctf_dynhash_insert (fp->ctf_syn_ext_strtab,
 274                           (void *) (uintptr_t)
 275                           atom->csa_external_offset,
 276                           (void *) atom->csa_str) < 0)
 277     {
 278       /* No need to bother freeing the syn_ext_strtab: it will get freed at
 279          ctf_str_write_strtab time if unreferenced.  */
 280       ctf_set_errno (fp, ENOMEM);
 281       return 0;
 282     }
 283
 284   return 1;
 285 }
 286
 287 /* Remove a single ref.  */
 288 void
 289 ctf_str_remove_ref (ctf_dict_t *fp, const char *str, uint32_t *ref)
 290 {
 291   ctf_str_atom_ref_t *aref, *anext;
 292   ctf_str_atom_t *atom = NULL;
 293
 294   atom = ctf_dynhash_lookup (fp->ctf_str_atoms, str);
 295   if (!atom)
 296     return;
 297
 298   for (aref = ctf_list_next (&atom->csa_refs); aref != NULL; aref = anext)
 299     {
 300       anext = ctf_list_next (aref);
 301       if (aref->caf_ref == ref)
 302         {
 303           ctf_list_delete (&atom->csa_refs, aref);
 304           free (aref);
 305         }
 306     }
 307 }
 308
 309 /* A ctf_dynhash_iter_remove() callback that removes atoms later than a given
 310    snapshot ID.  External atoms are never removed, because they came from the
 311    linker string table and are still present even if you roll back type
 312    additions.  */
 313 static int
 314 ctf_str_rollback_atom (void *key _libctf_unused_, void *value, void *arg)
 315 {
 316   ctf_str_atom_t *atom = (ctf_str_atom_t *) value;
 317   ctf_snapshot_id_t *id = (ctf_snapshot_id_t *) arg;
 318
 319   return (atom->csa_snapshot_id > id->snapshot_id)
 320     && (atom->csa_external_offset == 0);
 321 }
 322
 323 /* Roll back, deleting all (internal) atoms created after a particular ID.  */
 324 void
 325 ctf_str_rollback (ctf_dict_t *fp, ctf_snapshot_id_t id)
 326 {
 327   ctf_dynhash_iter_remove (fp->ctf_str_atoms, ctf_str_rollback_atom, &id);
 328 }
 329
 330 /* An adaptor around ctf_purge_atom_refs.  */
 331 static void
 332 ctf_str_purge_one_atom_refs (void *key _libctf_unused_, void *value,
 333                              void *arg _libctf_unused_)
 334 {
 335   ctf_str_atom_t *atom = (ctf_str_atom_t *) value;
 336   ctf_str_purge_atom_refs (atom);
 337 }
 338
 339 /* Remove all the recorded refs from the atoms table.  */
 340 void
 341 ctf_str_purge_refs (ctf_dict_t *fp)
 342 {
 343   if (fp->ctf_str_num_refs > 0)
 344     ctf_dynhash_iter (fp->ctf_str_atoms, ctf_str_purge_one_atom_refs, NULL);
 345   fp->ctf_str_num_refs = 0;
 346 }
 347
 348 /* Update a list of refs to the specified value. */
 349 static void
 350 ctf_str_update_refs (ctf_str_atom_t *refs, uint32_t value)
 351 {
 352   ctf_str_atom_ref_t *ref;
 353
 354   for (ref = ctf_list_next (&refs->csa_refs); ref != NULL;
 355        ref = ctf_list_next (ref))
 356       *(ref->caf_ref) = value;
 357 }
 358
 359 /* State shared across the strtab write process.  */
 360 typedef struct ctf_strtab_write_state
 361 {
 362   /* Strtab we are writing, and the number of strings in it.  */
 363   ctf_strs_writable_t *strtab;
 364   size_t strtab_count;
 365
 366   /* Pointers to (existing) atoms in the atoms table, for qsorting.  */
 367   ctf_str_atom_t **sorttab;
 368
 369   /* Loop counter for sorttab population.  */
 370   size_t i;
 371
 372   /* The null-string atom (skipped during population).  */
 373   ctf_str_atom_t *nullstr;
 374 } ctf_strtab_write_state_t;
 375
 376 /* Count the number of entries in the strtab, and its length.  */
 377 static void
 378 ctf_str_count_strtab (void *key _libctf_unused_, void *value,
 379               void *arg)
 380 {
 381   ctf_str_atom_t *atom = (ctf_str_atom_t *) value;
 382   ctf_strtab_write_state_t *s = (ctf_strtab_write_state_t *) arg;
 383
 384   /* We only factor in the length of items that have no offset and have refs:
 385      other items are in the external strtab, or will simply not be written out
 386      at all.  They still contribute to the total count, though, because we still
 387      have to sort them.  We add in the null string's length explicitly, outside
 388      this function, since it is explicitly written out even if it has no refs at
 389      all.  */
 390
 391   if (s->nullstr == atom)
 392     {
 393       s->strtab_count++;
 394       return;
 395     }
 396
 397   if (!ctf_list_empty_p (&atom->csa_refs))
 398     {
 399       if (!atom->csa_external_offset)
 400         s->strtab->cts_len += strlen (atom->csa_str) + 1;
 401       s->strtab_count++;
 402     }
 403 }
 404
 405 /* Populate the sorttab with pointers to the strtab atoms.  */
 406 static void
 407 ctf_str_populate_sorttab (void *key _libctf_unused_, void *value,
 408                   void *arg)
 409 {
 410   ctf_str_atom_t *atom = (ctf_str_atom_t *) value;
 411   ctf_strtab_write_state_t *s = (ctf_strtab_write_state_t *) arg;
 412
 413   /* Skip the null string.  */
 414   if (s->nullstr == atom)
 415     return;
 416
 417   /* Skip atoms with no refs.  */
 418   if (!ctf_list_empty_p (&atom->csa_refs))
 419     s->sorttab[s->i++] = atom;
 420 }
 421
 422 /* Sort the strtab.  */
 423 static int
 424 ctf_str_sort_strtab (const void *a, const void *b)
 425 {
 426   ctf_str_atom_t **one = (ctf_str_atom_t **) a;
 427   ctf_str_atom_t **two = (ctf_str_atom_t **) b;
 428
 429   return (strcmp ((*one)->csa_str, (*two)->csa_str));
 430 }
 431
 432 /* Write out and return a strtab containing all strings with recorded refs,
 433    adjusting the refs to refer to the corresponding string.  The returned strtab
 434    may be NULL on error.  Also populate the synthetic strtab with mappings from
 435    external strtab offsets to names, so we can look them up with ctf_strptr().
 436    Only external strtab offsets with references are added.  */
 437 ctf_strs_writable_t
 438 ctf_str_write_strtab (ctf_dict_t *fp)
 439 {
 440   ctf_strs_writable_t strtab;
 441   ctf_str_atom_t *nullstr;
 442   uint32_t cur_stroff = 0;
 443   ctf_strtab_write_state_t s;
 444   ctf_str_atom_t **sorttab;
 445   size_t i;
 446   int any_external = 0;
 447
 448   memset (&strtab, 0, sizeof (struct ctf_strs_writable));
 449   memset (&s, 0, sizeof (struct ctf_strtab_write_state));
 450   s.strtab = &strtab;
 451
 452   nullstr = ctf_dynhash_lookup (fp->ctf_str_atoms, "");
 453   if (!nullstr)
 454     {
 455       ctf_err_warn (fp, 0, ECTF_INTERNAL, _("null string not found in strtab"));
 456       strtab.cts_strs = NULL;
 457       return strtab;
 458     }
 459
 460   s.nullstr = nullstr;
 461   ctf_dynhash_iter (fp->ctf_str_atoms, ctf_str_count_strtab, &s);
 462   strtab.cts_len++;                             /* For the null string.  */
 463
 464   ctf_dprintf ("%lu bytes of strings in strtab.\n",
 465                (unsigned long) strtab.cts_len);
 466
 467   /* Sort the strtab.  Force the null string to be first.  */
 468   sorttab = calloc (s.strtab_count, sizeof (ctf_str_atom_t *));
 469   if (!sorttab)
 470     goto oom;
 471
 472   sorttab[0] = nullstr;
 473   s.i = 1;
 474   s.sorttab = sorttab;
 475   ctf_dynhash_iter (fp->ctf_str_atoms, ctf_str_populate_sorttab, &s);
 476
 477   qsort (&sorttab[1], s.strtab_count - 1, sizeof (ctf_str_atom_t *),
 478          ctf_str_sort_strtab);
 479
 480   if ((strtab.cts_strs = malloc (strtab.cts_len)) == NULL)
 481     goto oom_sorttab;
 482
 483   /* Update all refs: also update the strtab appropriately.  */
 484   for (i = 0; i < s.strtab_count; i++)
 485     {
 486       if (sorttab[i]->csa_external_offset)
 487         {
 488           /* External strtab entry.  */
 489
 490           any_external = 1;
 491           ctf_str_update_refs (sorttab[i], sorttab[i]->csa_external_offset);
 492           sorttab[i]->csa_offset = sorttab[i]->csa_external_offset;
 493         }
 494       else
 495         {
 496           /* Internal strtab entry with refs: actually add to the string
 497              table.  */
 498
 499           ctf_str_update_refs (sorttab[i], cur_stroff);
 500           sorttab[i]->csa_offset = cur_stroff;
 501           strcpy (&strtab.cts_strs[cur_stroff], sorttab[i]->csa_str);
 502           cur_stroff += strlen (sorttab[i]->csa_str) + 1;
 503         }
 504     }
 505   free (sorttab);
 506
 507   if (!any_external)
 508     {
 509       ctf_dynhash_destroy (fp->ctf_syn_ext_strtab);
 510       fp->ctf_syn_ext_strtab = NULL;
 511     }
 512
 513   /* All the provisional strtab entries are now real strtab entries, and
 514      ctf_strptr() will find them there.  The provisional offset now starts right
 515      beyond the new end of the strtab.  */
 516
 517   ctf_dynhash_empty (fp->ctf_prov_strtab);
 518   fp->ctf_str_prov_offset = strtab.cts_len + 1;
 519   return strtab;
 520
 521  oom_sorttab:
 522   free (sorttab);
 523  oom:
 524   return strtab;
 525 }