gcc/unwind-dw2-fde.c

   1 /* Subroutines needed for unwinding stack frames for exception handling.  */
   2 /* Copyright (C) 1997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
   3    Contributed by Jason Merrill <jason@cygnus.com>.
   4
   5 This file is part of GNU CC.
   6
   7 GNU CC 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 2, or (at your option)
  10 any later version.
  11
  12 In addition to the permissions in the GNU General Public License, the
  13 Free Software Foundation gives you unlimited permission to link the
  14 compiled version of this file into combinations with other programs,
  15 and to distribute those combinations without any restriction coming
  16 from the use of this file.  (The General Public License restrictions
  17 do apply in other respects; for example, they cover modification of
  18 the file, and distribution when not linked into a combine
  19 executable.)
  20
  21 GNU CC is distributed in the hope that it will be useful,
  22 but WITHOUT ANY WARRANTY; without even the implied warranty of
  23 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  24 GNU General Public License for more details.
  25
  26 You should have received a copy of the GNU General Public License
  27 along with GNU CC; see the file COPYING.  If not, write to
  28 the Free Software Foundation, 59 Temple Place - Suite 330,
  29 Boston, MA 02111-1307, USA.  */
  30
  31 #include "tconfig.h"
  32 #include "tsystem.h"
  33 #include "dwarf2.h"
  34 #include "unwind.h"
  35 #include "unwind-pe.h"
  36 #include "unwind-dw2-fde.h"
  37 #include "gthr.h"
  38
  39 /* The unseen_objects list contains objects that have been registered
  40    but not yet categorized in any way.  The seen_objects list has had
  41    it's pc_begin and count fields initialized at minimum, and is sorted
  42    by decreasing value of pc_begin.  */
  43 static struct object *unseen_objects;
  44 static struct object *seen_objects;
  45
  46 #ifdef __GTHREAD_MUTEX_INIT
  47 static __gthread_mutex_t object_mutex = __GTHREAD_MUTEX_INIT;
  48 #else
  49 static __gthread_mutex_t object_mutex;
  50 #endif
  51
  52 #ifdef __GTHREAD_MUTEX_INIT_FUNCTION
  53 static void
  54 init_object_mutex (void)
  55 {
  56   __GTHREAD_MUTEX_INIT_FUNCTION (&object_mutex);
  57 }
  58
  59 static void
  60 init_object_mutex_once (void)
  61 {
  62   static __gthread_once_t once = __GTHREAD_ONCE_INIT;
  63   __gthread_once (&once, init_object_mutex);
  64 }
  65 #else
  66 #define init_object_mutex_once()
  67 #endif
  68
  69 /* Called from crtbegin.o to register the unwind info for an object.  */
  70
  71 void
  72 __register_frame_info_bases (void *begin, struct object *ob,
  73                              void *tbase, void *dbase)
  74 {
  75   ob->pc_begin = (void *)-1;
  76   ob->tbase = tbase;
  77   ob->dbase = dbase;
  78   ob->u.single = begin;
  79   ob->s.i = 0;
  80   ob->s.b.encoding = DW_EH_PE_omit;
  81
  82   init_object_mutex_once ();
  83   __gthread_mutex_lock (&object_mutex);
  84
  85   ob->next = unseen_objects;
  86   unseen_objects = ob;
  87
  88   __gthread_mutex_unlock (&object_mutex);
  89 }
  90
  91 void
  92 __register_frame_info (void *begin, struct object *ob)
  93 {
  94   __register_frame_info_bases (begin, ob, 0, 0);
  95 }
  96
  97 void
  98 __register_frame (void *begin)
  99 {
 100   struct object *ob = (struct object *) malloc (sizeof (struct object));
 101   __register_frame_info (begin, ob);
 102 }
 103
 104 /* Similar, but BEGIN is actually a pointer to a table of unwind entries
 105    for different translation units.  Called from the file generated by
 106    collect2.  */
 107
 108 void
 109 __register_frame_info_table_bases (void *begin, struct object *ob,
 110                                    void *tbase, void *dbase)
 111 {
 112   ob->pc_begin = (void *)-1;
 113   ob->tbase = tbase;
 114   ob->dbase = dbase;
 115   ob->u.array = begin;
 116   ob->s.i = 0;
 117   ob->s.b.from_array = 1;
 118   ob->s.b.encoding = DW_EH_PE_omit;
 119
 120   init_object_mutex_once ();
 121   __gthread_mutex_lock (&object_mutex);
 122
 123   ob->next = unseen_objects;
 124   unseen_objects = ob;
 125
 126   __gthread_mutex_unlock (&object_mutex);
 127 }
 128
 129 void
 130 __register_frame_info_table (void *begin, struct object *ob)
 131 {
 132   __register_frame_info_table_bases (begin, ob, 0, 0);
 133 }
 134
 135 void
 136 __register_frame_table (void *begin)
 137 {
 138   struct object *ob = (struct object *) malloc (sizeof (struct object));
 139   __register_frame_info_table (begin, ob);
 140 }
 141
 142 /* Called from crtbegin.o to deregister the unwind info for an object.  */
 143 /* ??? Glibc has for a while now exported __register_frame_info and
 144    __deregister_frame_info.  If we call __register_frame_info_bases
 145    from crtbegin (wherein it is declared weak), and this object does
 146    not get pulled from libgcc.a for other reasons, then the
 147    invocation of __deregister_frame_info will be resolved from glibc.
 148    Since the registration did not happen there, we'll abort.
 149
 150    Therefore, declare a new deregistration entry point that does the
 151    exact same thing, but will resolve to the same library as
 152    implements __register_frame_info_bases.  */
 153
 154 void *
 155 __deregister_frame_info_bases (void *begin)
 156 {
 157   struct object **p;
 158   struct object *ob = 0;
 159
 160   init_object_mutex_once ();
 161   __gthread_mutex_lock (&object_mutex);
 162
 163   for (p = &unseen_objects; *p ; p = &(*p)->next)
 164     if ((*p)->u.single == begin)
 165       {
 166         ob = *p;
 167         *p = ob->next;
 168         goto out;
 169       }
 170
 171   for (p = &seen_objects; *p ; p = &(*p)->next)
 172     if ((*p)->s.b.sorted)
 173       {
 174         if ((*p)->u.sort->orig_data == begin)
 175           {
 176             ob = *p;
 177             *p = ob->next;
 178             free (ob->u.sort);
 179             goto out;
 180           }
 181       }
 182     else
 183       {
 184         if ((*p)->u.single == begin)
 185           {
 186             ob = *p;
 187             *p = ob->next;
 188             goto out;
 189           }
 190       }
 191
 192   __gthread_mutex_unlock (&object_mutex);
 193   abort ();
 194
 195  out:
 196   __gthread_mutex_unlock (&object_mutex);
 197   return (void *) ob;
 198 }
 199
 200 void *
 201 __deregister_frame_info (void *begin)
 202 {
 203   return __deregister_frame_info_bases (begin);
 204 }
 205
 206 void
 207 __deregister_frame (void *begin)
 208 {
 209   free (__deregister_frame_info (begin));
 210 }
 211
 212 \f
 213 /* Like base_of_encoded_value, but take the base from a struct object
 214    instead of an _Unwind_Context.  */
 215
 216 static _Unwind_Ptr
 217 base_from_object (unsigned char encoding, struct object *ob)
 218 {
 219   if (encoding == DW_EH_PE_omit)
 220     return 0;
 221
 222   switch (encoding & 0x70)
 223     {
 224     case DW_EH_PE_absptr:
 225     case DW_EH_PE_pcrel:
 226     case DW_EH_PE_aligned:
 227       return 0;
 228
 229     case DW_EH_PE_textrel:
 230       return (_Unwind_Ptr) ob->tbase;
 231     case DW_EH_PE_datarel:
 232       return (_Unwind_Ptr) ob->dbase;
 233     }
 234   abort ();
 235 }
 236
 237 /* Return the FDE pointer encoding from the CIE.  */
 238 /* ??? This is a subset of extract_cie_info from unwind-dw2.c.  */
 239
 240 static int
 241 get_cie_encoding (struct dwarf_cie *cie)
 242 {
 243   const unsigned char *aug, *p;
 244   _Unwind_Ptr dummy;
 245
 246   aug = cie->augmentation;
 247   if (aug[0] != 'z')
 248     return DW_EH_PE_absptr;
 249
 250   p = aug + strlen (aug) + 1;           /* Skip the augmentation string.  */
 251   p = read_uleb128 (p, &dummy);         /* Skip code alignment.  */
 252   p = read_sleb128 (p, &dummy);         /* Skip data alignment.  */
 253   p++;                                  /* Skip return address column.  */
 254
 255   aug++;                                /* Skip 'z' */
 256   p = read_uleb128 (p, &dummy);         /* Skip augmentation length.  */
 257   while (1)
 258     {
 259       /* This is what we're looking for.  */
 260       if (*aug == 'R')
 261         return *p;
 262       /* Personality encoding and pointer.  */
 263       else if (*aug == 'P')
 264         {
 265           /* ??? Avoid dereferencing indirect pointers, since we're
 266              faking the base address.  Gotta keep DW_EH_PE_aligned
 267              intact, however.  */
 268           p = read_encoded_value_with_base (*p & 0x7F, 0, p + 1, &dummy);
 269         }
 270       /* LSDA encoding.  */
 271       else if (*aug == 'L')
 272         p++;
 273       /* Otherwise end of string, or unknown augmentation.  */
 274       else
 275         return DW_EH_PE_absptr;
 276       aug++;
 277     }
 278 }
 279
 280 static inline int
 281 get_fde_encoding (struct dwarf_fde *f)
 282 {
 283   return get_cie_encoding (get_cie (f));
 284 }
 285
 286 \f
 287 /* Sorting an array of FDEs by address.
 288    (Ideally we would have the linker sort the FDEs so we don't have to do
 289    it at run time. But the linkers are not yet prepared for this.)  */
 290
 291 /* Comparison routines.  Three variants of increasing complexity.  */
 292
 293 static saddr
 294 fde_unencoded_compare (struct object *ob __attribute__((unused)),
 295                        fde *x, fde *y)
 296 {
 297   return *(saddr *)x->pc_begin - *(saddr *)y->pc_begin;
 298 }
 299
 300 static saddr
 301 fde_single_encoding_compare (struct object *ob, fde *x, fde *y)
 302 {
 303   _Unwind_Ptr base, x_ptr, y_ptr;
 304
 305   base = base_from_object (ob->s.b.encoding, ob);
 306   read_encoded_value_with_base (ob->s.b.encoding, base, x->pc_begin, &x_ptr);
 307   read_encoded_value_with_base (ob->s.b.encoding, base, y->pc_begin, &y_ptr);
 308
 309   return x_ptr - y_ptr;
 310 }
 311
 312 static saddr
 313 fde_mixed_encoding_compare (struct object *ob, fde *x, fde *y)
 314 {
 315   int x_encoding, y_encoding;
 316   _Unwind_Ptr x_ptr, y_ptr;
 317
 318   x_encoding = get_fde_encoding (x);
 319   read_encoded_value_with_base (x_encoding, base_from_object (x_encoding, ob),
 320                                 x->pc_begin, &x_ptr);
 321
 322   y_encoding = get_fde_encoding (y);
 323   read_encoded_value_with_base (y_encoding, base_from_object (y_encoding, ob),
 324                                 y->pc_begin, &y_ptr);
 325
 326   return x_ptr - y_ptr;
 327 }
 328
 329 typedef saddr (*fde_compare_t) (struct object *, fde *, fde *);
 330
 331
 332 /* This is a special mix of insertion sort and heap sort, optimized for
 333    the data sets that actually occur. They look like
 334    101 102 103 127 128 105 108 110 190 111 115 119 125 160 126 129 130.
 335    I.e. a linearly increasing sequence (coming from functions in the text
 336    section), with additionally a few unordered elements (coming from functions
 337    in gnu_linkonce sections) whose values are higher than the values in the
 338    surrounding linear sequence (but not necessarily higher than the values
 339    at the end of the linear sequence!).
 340    The worst-case total run time is O(N) + O(n log (n)), where N is the
 341    total number of FDEs and n is the number of erratic ones.  */
 342
 343 struct fde_accumulator
 344 {
 345   struct fde_vector *linear;
 346   struct fde_vector *erratic;
 347 };
 348
 349 static inline int
 350 start_fde_sort (struct fde_accumulator *accu, size_t count)
 351 {
 352   size_t size;
 353   if (! count)
 354     return 0;
 355
 356   size = sizeof (struct fde_vector) + sizeof (fde *) * count;
 357   if ((accu->linear = (struct fde_vector *) malloc (size)))
 358     {
 359       accu->linear->count = 0;
 360       if ((accu->erratic = (struct fde_vector *) malloc (size)))
 361         accu->erratic->count = 0;
 362       return 1;
 363     }
 364   else
 365     return 0;
 366 }
 367
 368 static inline void
 369 fde_insert (struct fde_accumulator *accu, fde *this_fde)
 370 {
 371   if (accu->linear)
 372     accu->linear->array[accu->linear->count++] = this_fde;
 373 }
 374
 375 /* Split LINEAR into a linear sequence with low values and an erratic
 376    sequence with high values, put the linear one (of longest possible
 377    length) into LINEAR and the erratic one into ERRATIC. This is O(N).
 378
 379    Because the longest linear sequence we are trying to locate within the
 380    incoming LINEAR array can be interspersed with (high valued) erratic
 381    entries.  We construct a chain indicating the sequenced entries.
 382    To avoid having to allocate this chain, we overlay it onto the space of
 383    the ERRATIC array during construction.  A final pass iterates over the
 384    chain to determine what should be placed in the ERRATIC array, and
 385    what is the linear sequence.  This overlay is safe from aliasing.  */
 386
 387 static inline void
 388 fde_split (struct object *ob, fde_compare_t fde_compare,
 389            struct fde_vector *linear, struct fde_vector *erratic)
 390 {
 391   static fde *marker;
 392   size_t count = linear->count;
 393   fde **chain_end = &marker;
 394   size_t i, j, k;
 395
 396   /* This should optimize out, but it is wise to make sure this assumption
 397      is correct. Should these have different sizes, we cannot cast between
 398      them and the overlaying onto ERRATIC will not work.  */
 399   if (sizeof (fde *) != sizeof (fde **))
 400     abort ();
 401
 402   for (i = 0; i < count; i++)
 403     {
 404       fde **probe;
 405
 406       for (probe = chain_end;
 407            probe != &marker && fde_compare (ob, linear->array[i], *probe) < 0;
 408            probe = chain_end)
 409         {
 410           chain_end = (fde **)erratic->array[probe - linear->array];
 411           erratic->array[probe - linear->array] = NULL;
 412         }
 413       erratic->array[i] = (fde *)chain_end;
 414       chain_end = &linear->array[i];
 415     }
 416
 417   /* Each entry in LINEAR which is part of the linear sequence we have
 418      discovered will correspond to a non-NULL entry in the chain we built in
 419      the ERRATIC array.  */
 420   for (i = j = k = 0; i < count; i++)
 421     if (erratic->array[i])
 422       linear->array[j++] = linear->array[i];
 423     else
 424       erratic->array[k++] = linear->array[i];
 425   linear->count = j;
 426   erratic->count = k;
 427 }
 428
 429 /* This is O(n log(n)).  BSD/OS defines heapsort in stdlib.h, so we must
 430    use a name that does not conflict.  */
 431
 432 static void
 433 frame_heapsort (struct object *ob, fde_compare_t fde_compare,
 434                 struct fde_vector *erratic)
 435 {
 436   /* For a description of this algorithm, see:
 437      Samuel P. Harbison, Guy L. Steele Jr.: C, a reference manual, 2nd ed.,
 438      p. 60-61. */
 439   fde ** a = erratic->array;
 440   /* A portion of the array is called a "heap" if for all i>=0:
 441      If i and 2i+1 are valid indices, then a[i] >= a[2i+1].
 442      If i and 2i+2 are valid indices, then a[i] >= a[2i+2]. */
 443 #define SWAP(x,y) do { fde * tmp = x; x = y; y = tmp; } while (0)
 444   size_t n = erratic->count;
 445   size_t m = n;
 446   size_t i;
 447
 448   while (m > 0)
 449     {
 450       /* Invariant: a[m..n-1] is a heap. */
 451       m--;
 452       for (i = m; 2*i+1 < n; )
 453         {
 454           if (2*i+2 < n
 455               && fde_compare (ob, a[2*i+2], a[2*i+1]) > 0
 456               && fde_compare (ob, a[2*i+2], a[i]) > 0)
 457             {
 458               SWAP (a[i], a[2*i+2]);
 459               i = 2*i+2;
 460             }
 461           else if (fde_compare (ob, a[2*i+1], a[i]) > 0)
 462             {
 463               SWAP (a[i], a[2*i+1]);
 464               i = 2*i+1;
 465             }
 466           else
 467             break;
 468         }
 469     }
 470   while (n > 1)
 471     {
 472       /* Invariant: a[0..n-1] is a heap. */
 473       n--;
 474       SWAP (a[0], a[n]);
 475       for (i = 0; 2*i+1 < n; )
 476         {
 477           if (2*i+2 < n
 478               && fde_compare (ob, a[2*i+2], a[2*i+1]) > 0
 479               && fde_compare (ob, a[2*i+2], a[i]) > 0)
 480             {
 481               SWAP (a[i], a[2*i+2]);
 482               i = 2*i+2;
 483             }
 484           else if (fde_compare (ob, a[2*i+1], a[i]) > 0)
 485             {
 486               SWAP (a[i], a[2*i+1]);
 487               i = 2*i+1;
 488             }
 489           else
 490             break;
 491         }
 492     }
 493 #undef SWAP
 494 }
 495
 496 /* Merge V1 and V2, both sorted, and put the result into V1. */
 497 static inline void
 498 fde_merge (struct object *ob, fde_compare_t fde_compare,
 499            struct fde_vector *v1, struct fde_vector *v2)
 500 {
 501   size_t i1, i2;
 502   fde * fde2;
 503
 504   i2 = v2->count;
 505   if (i2 > 0)
 506     {
 507       i1 = v1->count;
 508       do {
 509         i2--;
 510         fde2 = v2->array[i2];
 511         while (i1 > 0 && fde_compare (ob, v1->array[i1-1], fde2) > 0)
 512           {
 513             v1->array[i1+i2] = v1->array[i1-1];
 514             i1--;
 515           }
 516         v1->array[i1+i2] = fde2;
 517       } while (i2 > 0);
 518       v1->count += v2->count;
 519     }
 520 }
 521
 522 static inline void
 523 end_fde_sort (struct object *ob, struct fde_accumulator *accu, size_t count)
 524 {
 525   fde_compare_t fde_compare;
 526
 527   if (accu->linear && accu->linear->count != count)
 528     abort ();
 529
 530   if (ob->s.b.mixed_encoding)
 531     fde_compare = fde_mixed_encoding_compare;
 532   else if (ob->s.b.encoding == DW_EH_PE_absptr)
 533     fde_compare = fde_unencoded_compare;
 534   else
 535     fde_compare = fde_single_encoding_compare;
 536
 537   if (accu->erratic)
 538     {
 539       fde_split (ob, fde_compare, accu->linear, accu->erratic);
 540       if (accu->linear->count + accu->erratic->count != count)
 541         abort ();
 542       frame_heapsort (ob, fde_compare, accu->erratic);
 543       fde_merge (ob, fde_compare, accu->linear, accu->erratic);
 544       free (accu->erratic);
 545     }
 546   else
 547     {
 548       /* We've not managed to malloc an erratic array,
 549          so heap sort in the linear one.  */
 550       frame_heapsort (ob, fde_compare, accu->linear);
 551     }
 552 }
 553
 554 \f
 555 /* Update encoding, mixed_encoding, and pc_begin for OB for the
 556    fde array beginning at THIS_FDE.  Return the number of fdes
 557    encountered along the way.  */
 558
 559 static size_t
 560 classify_object_over_fdes (struct object *ob, fde *this_fde)
 561 {
 562   struct dwarf_cie *last_cie = 0;
 563   size_t count = 0;
 564   int encoding = DW_EH_PE_absptr;
 565   _Unwind_Ptr base = 0;
 566
 567   for (; this_fde->length != 0; this_fde = next_fde (this_fde))
 568     {
 569       struct dwarf_cie *this_cie;
 570       _Unwind_Ptr mask, pc_begin;
 571
 572       /* Skip CIEs.  */
 573       if (this_fde->CIE_delta == 0)
 574         continue;
 575
 576       /* Determine the encoding for this FDE.  Note mixed encoded
 577          objects for later.  */
 578       this_cie = get_cie (this_fde);
 579       if (this_cie != last_cie)
 580         {
 581           last_cie = this_cie;
 582           encoding = get_cie_encoding (this_cie);
 583           base = base_from_object (encoding, ob);
 584           if (ob->s.b.encoding == DW_EH_PE_omit)
 585             ob->s.b.encoding = encoding;
 586           else if (ob->s.b.encoding != encoding)
 587             ob->s.b.mixed_encoding = 1;
 588         }
 589
 590       read_encoded_value_with_base (encoding, base, this_fde->pc_begin,
 591                                     &pc_begin);
 592
 593       /* Take care to ignore link-once functions that were removed.
 594          In these cases, the function address will be NULL, but if
 595          the encoding is smaller than a pointer a true NULL may not
 596          be representable.  Assume 0 in the representable bits is NULL.  */
 597       mask = size_of_encoded_value (encoding);
 598       if (mask < sizeof (void *))
 599         mask = (1L << (mask << 3)) - 1;
 600       else
 601         mask = -1;
 602
 603       if ((pc_begin & mask) == 0)
 604         continue;
 605
 606       count += 1;
 607       if ((void *)pc_begin < ob->pc_begin)
 608         ob->pc_begin = (void *)pc_begin;
 609     }
 610
 611   return count;
 612 }
 613
 614 static void
 615 add_fdes (struct object *ob, struct fde_accumulator *accu, fde *this_fde)
 616 {
 617   struct dwarf_cie *last_cie = 0;
 618   int encoding = ob->s.b.encoding;
 619   _Unwind_Ptr base = base_from_object (ob->s.b.encoding, ob);
 620
 621   for (; this_fde->length != 0; this_fde = next_fde (this_fde))
 622     {
 623       struct dwarf_cie *this_cie;
 624
 625       /* Skip CIEs.  */
 626       if (this_fde->CIE_delta == 0)
 627         continue;
 628
 629       if (ob->s.b.mixed_encoding)
 630         {
 631           /* Determine the encoding for this FDE.  Note mixed encoded
 632              objects for later.  */
 633           this_cie = get_cie (this_fde);
 634           if (this_cie != last_cie)
 635             {
 636               last_cie = this_cie;
 637               encoding = get_cie_encoding (this_cie);
 638               base = base_from_object (encoding, ob);
 639             }
 640         }
 641
 642       if (encoding == DW_EH_PE_absptr)
 643         {
 644           if (*(_Unwind_Ptr *)this_fde->pc_begin == 0)
 645             continue;
 646         }
 647       else
 648         {
 649           _Unwind_Ptr pc_begin, mask;
 650
 651           read_encoded_value_with_base (encoding, base, this_fde->pc_begin,
 652                                         &pc_begin);
 653
 654           /* Take care to ignore link-once functions that were removed.
 655              In these cases, the function address will be NULL, but if
 656              the encoding is smaller than a pointer a true NULL may not
 657              be representable.  Assume 0 in the representable bits is NULL.  */
 658           mask = size_of_encoded_value (encoding);
 659           if (mask < sizeof (void *))
 660             mask = (1L << (mask << 3)) - 1;
 661           else
 662             mask = -1;
 663
 664           if ((pc_begin & mask) == 0)
 665             continue;
 666         }
 667
 668       fde_insert (accu, this_fde);
 669     }
 670 }
 671
 672 /* Set up a sorted array of pointers to FDEs for a loaded object.  We
 673    count up the entries before allocating the array because it's likely to
 674    be faster.  We can be called multiple times, should we have failed to
 675    allocate a sorted fde array on a previous occasion.  */
 676
 677 static inline void
 678 init_object (struct object* ob)
 679 {
 680   struct fde_accumulator accu;
 681   size_t count;
 682
 683   count = ob->s.b.count;
 684   if (count == 0)
 685     {
 686       if (ob->s.b.from_array)
 687         {
 688           fde **p = ob->u.array;
 689           for (count = 0; *p; ++p)
 690             count += classify_object_over_fdes (ob, *p);
 691         }
 692       else
 693         count = classify_object_over_fdes (ob, ob->u.single);
 694
 695       /* The count field we have in the main struct object is somewhat
 696          limited, but should suffice for virtually all cases.  If the
 697          counted value doesn't fit, re-write a zero.  The worst that
 698          happens is that we re-count next time -- admittedly non-trivial
 699          in that this implies some 2M fdes, but at least we function.  */
 700       ob->s.b.count = count;
 701       if (ob->s.b.count != count)
 702         ob->s.b.count = 0;
 703     }
 704
 705   if (!start_fde_sort (&accu, count))
 706     return;
 707
 708   if (ob->s.b.from_array)
 709     {
 710       fde **p;
 711       for (p = ob->u.array; *p; ++p)
 712         add_fdes (ob, &accu, *p);
 713     }
 714   else
 715     add_fdes (ob, &accu, ob->u.single);
 716
 717   end_fde_sort (ob, &accu, count);
 718
 719   /* Save the original fde pointer, since this is the key by which the
 720      DSO will deregister the object.  */
 721   accu.linear->orig_data = ob->u.single;
 722   ob->u.sort = accu.linear;
 723
 724   ob->s.b.sorted = 1;
 725 }
 726
 727 /* A linear search through a set of FDEs for the given PC.  This is
 728    used when there was insufficient memory to allocate and sort an
 729    array.  */
 730
 731 static fde *
 732 linear_search_fdes (struct object *ob, fde *this_fde, void *pc)
 733 {
 734   struct dwarf_cie *last_cie = 0;
 735   int encoding = ob->s.b.encoding;
 736   _Unwind_Ptr base = base_from_object (ob->s.b.encoding, ob);
 737
 738   for (; this_fde->length != 0; this_fde = next_fde (this_fde))
 739     {
 740       struct dwarf_cie *this_cie;
 741       _Unwind_Ptr pc_begin, pc_range;
 742
 743       /* Skip CIEs.  */
 744       if (this_fde->CIE_delta == 0)
 745         continue;
 746
 747       if (ob->s.b.mixed_encoding)
 748         {
 749           /* Determine the encoding for this FDE.  Note mixed encoded
 750              objects for later.  */
 751           this_cie = get_cie (this_fde);
 752           if (this_cie != last_cie)
 753             {
 754               last_cie = this_cie;
 755               encoding = get_cie_encoding (this_cie);
 756               base = base_from_object (encoding, ob);
 757             }
 758         }
 759
 760       if (encoding == DW_EH_PE_absptr)
 761         {
 762           pc_begin = ((_Unwind_Ptr *)this_fde->pc_begin)[0];
 763           pc_range = ((_Unwind_Ptr *)this_fde->pc_begin)[1];
 764           if (pc_begin == 0)
 765             continue;
 766         }
 767       else
 768         {
 769           _Unwind_Ptr mask;
 770           const char *p;
 771
 772           p = read_encoded_value_with_base (encoding, base,
 773                                             this_fde->pc_begin, &pc_begin);
 774           read_encoded_value_with_base (encoding & 0x0F, 0, p, &pc_range);
 775
 776           /* Take care to ignore link-once functions that were removed.
 777              In these cases, the function address will be NULL, but if
 778              the encoding is smaller than a pointer a true NULL may not
 779              be representable.  Assume 0 in the representable bits is NULL.  */
 780           mask = size_of_encoded_value (encoding);
 781           if (mask < sizeof (void *))
 782             mask = (1L << (mask << 3)) - 1;
 783           else
 784             mask = -1;
 785
 786           if ((pc_begin & mask) == 0)
 787             continue;
 788         }
 789
 790       if ((_Unwind_Ptr)pc - pc_begin < pc_range)
 791         return this_fde;
 792     }
 793
 794   return NULL;
 795 }
 796
 797 /* Binary search for an FDE containing the given PC.  Here are three
 798    implementations of increasing complexity.  */
 799
 800 static inline fde *
 801 binary_search_unencoded_fdes (struct object *ob, void *pc)
 802 {
 803   struct fde_vector *vec = ob->u.sort;
 804   size_t lo, hi;
 805
 806   for (lo = 0, hi = vec->count; lo < hi; )
 807     {
 808       size_t i = (lo + hi) / 2;
 809       fde *f = vec->array[i];
 810       void *pc_begin;
 811       uaddr pc_range;
 812
 813       pc_begin = ((void **)f->pc_begin)[0];
 814       pc_range = ((uaddr *)f->pc_begin)[1];
 815
 816       if (pc < pc_begin)
 817         hi = i;
 818       else if (pc >= pc_begin + pc_range)
 819         lo = i + 1;
 820       else
 821         return f;
 822     }
 823
 824   return NULL;
 825 }
 826
 827 static inline fde *
 828 binary_search_single_encoding_fdes (struct object *ob, void *pc)
 829 {
 830   struct fde_vector *vec = ob->u.sort;
 831   int encoding = ob->s.b.encoding;
 832   _Unwind_Ptr base = base_from_object (encoding, ob);
 833   size_t lo, hi;
 834
 835   for (lo = 0, hi = vec->count; lo < hi; )
 836     {
 837       size_t i = (lo + hi) / 2;
 838       fde *f = vec->array[i];
 839       _Unwind_Ptr pc_begin, pc_range;
 840       const char *p;
 841
 842       p = read_encoded_value_with_base (encoding, base, f->pc_begin,
 843                                         &pc_begin);
 844       read_encoded_value_with_base (encoding & 0x0F, 0, p, &pc_range);
 845
 846       if ((_Unwind_Ptr)pc < pc_begin)
 847         hi = i;
 848       else if ((_Unwind_Ptr)pc >= pc_begin + pc_range)
 849         lo = i + 1;
 850       else
 851         return f;
 852     }
 853
 854   return NULL;
 855 }
 856
 857 static inline fde *
 858 binary_search_mixed_encoding_fdes (struct object *ob, void *pc)
 859 {
 860   struct fde_vector *vec = ob->u.sort;
 861   size_t lo, hi;
 862
 863   for (lo = 0, hi = vec->count; lo < hi; )
 864     {
 865       size_t i = (lo + hi) / 2;
 866       fde *f = vec->array[i];
 867       _Unwind_Ptr pc_begin, pc_range;
 868       const char *p;
 869       int encoding;
 870
 871       encoding = get_fde_encoding (f);
 872       p = read_encoded_value_with_base (encoding,
 873                                         base_from_object (encoding, ob),
 874                                         f->pc_begin, &pc_begin);
 875       read_encoded_value_with_base (encoding & 0x0F, 0, p, &pc_range);
 876
 877       if ((_Unwind_Ptr)pc < pc_begin)
 878         hi = i;
 879       else if ((_Unwind_Ptr)pc >= pc_begin + pc_range)
 880         lo = i + 1;
 881       else
 882         return f;
 883     }
 884
 885   return NULL;
 886 }
 887
 888 static fde *
 889 search_object (struct object* ob, void *pc)
 890 {
 891   /* If the data hasn't been sorted, try to do this now.  We may have
 892      more memory available than last time we tried.  */
 893   if (! ob->s.b.sorted)
 894     {
 895       init_object (ob);
 896
 897       /* Despite the above comment, the normal reason to get here is
 898          that we've not processed this object before.  A quick range
 899          check is in order.  */
 900       if (pc < ob->pc_begin)
 901         return NULL;
 902     }
 903
 904   if (ob->s.b.sorted)
 905     {
 906       if (ob->s.b.mixed_encoding)
 907         return binary_search_mixed_encoding_fdes (ob, pc);
 908       else if (ob->s.b.encoding == DW_EH_PE_absptr)
 909         return binary_search_unencoded_fdes (ob, pc);
 910       else
 911         return binary_search_single_encoding_fdes (ob, pc);
 912     }
 913   else
 914     {
 915       /* Long slow labourious linear search, cos we've no memory.  */
 916       if (ob->s.b.from_array)
 917         {
 918           fde **p;
 919           for (p = ob->u.array; *p ; p++)
 920             {
 921               fde *f = linear_search_fdes (ob, *p, pc);
 922               if (f)
 923                 return f;
 924             }
 925           return NULL;
 926         }
 927       else
 928         return linear_search_fdes (ob, ob->u.single, pc);
 929     }
 930 }
 931
 932 fde *
 933 _Unwind_Find_FDE (void *pc, struct dwarf_eh_bases *bases)
 934 {
 935   struct object *ob;
 936   fde *f = NULL;
 937
 938   init_object_mutex_once ();
 939   __gthread_mutex_lock (&object_mutex);
 940
 941   /* Linear search through the classified objects, to find the one
 942      containing the pc.  Note that pc_begin is sorted decending, and
 943      we expect objects to be non-overlapping.  */
 944   for (ob = seen_objects; ob; ob = ob->next)
 945     if (pc >= ob->pc_begin)
 946       {
 947         f = search_object (ob, pc);
 948         if (f)
 949           goto fini;
 950         break;
 951       }
 952
 953   /* Classify and search the objects we've not yet processed.  */
 954   while ((ob = unseen_objects))
 955     {
 956       struct object **p;
 957
 958       unseen_objects = ob->next;
 959       f = search_object (ob, pc);
 960
 961       /* Insert the object into the classified list.  */
 962       for (p = &seen_objects; *p ; p = &(*p)->next)
 963         if ((*p)->pc_begin < ob->pc_begin)
 964           break;
 965       ob->next = *p;
 966       *p = ob;
 967
 968       if (f)
 969         goto fini;
 970     }
 971
 972  fini:
 973   __gthread_mutex_unlock (&object_mutex);
 974
 975   if (f)
 976     {
 977       int encoding;
 978
 979       bases->tbase = ob->tbase;
 980       bases->dbase = ob->dbase;
 981
 982       encoding = ob->s.b.encoding;
 983       if (ob->s.b.mixed_encoding)
 984         encoding = get_fde_encoding (f);
 985       read_encoded_value_with_base (encoding, base_from_object (encoding, ob),
 986                                     f->pc_begin, (_Unwind_Ptr *)&bases->func);
 987     }
 988
 989   return f;
 990 }