boehm-gc/mark_rts.c

   1 /*
   2  * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
   3  * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
   4  *
   5  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   6  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   7  *
   8  * Permission is hereby granted to use or copy this program
   9  * for any purpose,  provided the above notices are retained on all copies.
  10  * Permission to modify the code and to distribute modified code is granted,
  11  * provided the above notices are retained, and a notice that the code was
  12  * modified is included with the above copyright notice.
  13  */
  14 /* Boehm, October 9, 1995 1:06 pm PDT */
  15 # include <stdio.h>
  16 # include "gc_priv.h"
  17
  18 /* MAX_ROOT_SETS is the maximum number of ranges that can be    */
  19 /* registered as static roots.                                  */
  20 # ifdef LARGE_CONFIG
  21 #   define MAX_ROOT_SETS 4096
  22 # else
  23 #   ifdef PCR
  24 #     define MAX_ROOT_SETS 1024
  25 #   else
  26 #     ifdef MSWIN32
  27 #       define MAX_ROOT_SETS 512
  28             /* Under NT, we add only written pages, which can result    */
  29             /* in many small root sets.                                 */
  30 #     else
  31 #       define MAX_ROOT_SETS 64
  32 #     endif
  33 #   endif
  34 # endif
  35
  36 # define MAX_EXCLUSIONS (MAX_ROOT_SETS/4)
  37 /* Maximum number of segments that can be excluded from root sets.      */
  38
  39 /* Data structure for list of root sets.                                */
  40 /* We keep a hash table, so that we can filter out duplicate additions. */
  41 /* Under Win32, we need to do a better job of filtering overlaps, so    */
  42 /* we resort to sequential search, and pay the price.                   */
  43 struct roots {
  44         ptr_t r_start;
  45         ptr_t r_end;
  46 #       ifndef MSWIN32
  47           struct roots * r_next;
  48 #       endif
  49         GC_bool r_tmp;
  50                 /* Delete before registering new dynamic libraries */
  51 };
  52
  53 static struct roots static_roots[MAX_ROOT_SETS];
  54
  55 static int n_root_sets = 0;
  56
  57         /* static_roots[0..n_root_sets) contains the valid root sets. */
  58
  59 # if !defined(NO_DEBUGGING)
  60 /* For debugging:       */
  61 void GC_print_static_roots()
  62 {
  63     register int i;
  64     size_t total = 0;
  65
  66     for (i = 0; i < n_root_sets; i++) {
  67         GC_printf2("From 0x%lx to 0x%lx ",
  68                    (unsigned long) static_roots[i].r_start,
  69                    (unsigned long) static_roots[i].r_end);
  70         if (static_roots[i].r_tmp) {
  71             GC_printf0(" (temporary)\n");
  72         } else {
  73             GC_printf0("\n");
  74         }
  75         total += static_roots[i].r_end - static_roots[i].r_start;
  76     }
  77     GC_printf1("Total size: %ld\n", (unsigned long) total);
  78     if (GC_root_size != total) {
  79         GC_printf1("GC_root_size incorrect: %ld!!\n",
  80                    (unsigned long) GC_root_size);
  81     }
  82 }
  83 # endif /* NO_DEBUGGING */
  84
  85 /* Primarily for debugging support:     */
  86 /* Is the address p in one of the registered static                     */
  87 /* root sections?                                                       */
  88 GC_bool GC_is_static_root(p)
  89 ptr_t p;
  90 {
  91     static int last_root_set = 0;
  92     register int i;
  93
  94
  95     if (p >= static_roots[last_root_set].r_start
  96         && p < static_roots[last_root_set].r_end) return(TRUE);
  97     for (i = 0; i < n_root_sets; i++) {
  98         if (p >= static_roots[i].r_start
  99             && p < static_roots[i].r_end) {
 100             last_root_set = i;
 101             return(TRUE);
 102         }
 103     }
 104     return(FALSE);
 105 }
 106
 107 #ifndef MSWIN32
 108 #   define LOG_RT_SIZE 6
 109 #   define RT_SIZE (1 << LOG_RT_SIZE)  /* Power of 2, may be != MAX_ROOT_SETS */
 110
 111     static struct roots * root_index[RT_SIZE];
 112         /* Hash table header.  Used only to check whether a range is    */
 113         /* already present.                                             */
 114
 115 static int rt_hash(addr)
 116 char * addr;
 117 {
 118     word result = (word) addr;
 119 #   if CPP_WORDSZ > 8*LOG_RT_SIZE
 120         result ^= result >> 8*LOG_RT_SIZE;
 121 #   endif
 122 #   if CPP_WORDSZ > 4*LOG_RT_SIZE
 123         result ^= result >> 4*LOG_RT_SIZE;
 124 #   endif
 125     result ^= result >> 2*LOG_RT_SIZE;
 126     result ^= result >> LOG_RT_SIZE;
 127     result &= (RT_SIZE-1);
 128     return(result);
 129 }
 130
 131 /* Is a range starting at b already in the table? If so return a        */
 132 /* pointer to it, else NIL.                                             */
 133 struct roots * GC_roots_present(b)
 134 char *b;
 135 {
 136     register int h = rt_hash(b);
 137     register struct roots *p = root_index[h];
 138
 139     while (p != 0) {
 140         if (p -> r_start == (ptr_t)b) return(p);
 141         p = p -> r_next;
 142     }
 143     return(FALSE);
 144 }
 145
 146 /* Add the given root structure to the index. */
 147 static void add_roots_to_index(p)
 148 struct roots *p;
 149 {
 150     register int h = rt_hash(p -> r_start);
 151
 152     p -> r_next = root_index[h];
 153     root_index[h] = p;
 154 }
 155
 156 # else /* MSWIN32 */
 157
 158 #   define add_roots_to_index(p)
 159
 160 # endif
 161
 162
 163
 164
 165 word GC_root_size = 0;
 166
 167 void GC_add_roots(b, e)
 168 char * b; char * e;
 169 {
 170     DCL_LOCK_STATE;
 171
 172     DISABLE_SIGNALS();
 173     LOCK();
 174     GC_add_roots_inner(b, e, FALSE);
 175     UNLOCK();
 176     ENABLE_SIGNALS();
 177 }
 178
 179
 180 /* Add [b,e) to the root set.  Adding the same interval a second time   */
 181 /* is a moderately fast noop, and hence benign.  We do not handle       */
 182 /* different but overlapping intervals efficiently.  (We do handle      */
 183 /* them correctly.)                                                     */
 184 /* Tmp specifies that the interval may be deleted before                */
 185 /* reregistering dynamic libraries.                                     */
 186 void GC_add_roots_inner(b, e, tmp)
 187 char * b; char * e;
 188 GC_bool tmp;
 189 {
 190     struct roots * old;
 191
 192 #   ifdef MSWIN32
 193       /* Spend the time to ensure that there are no overlapping */
 194       /* or adjacent intervals.                                 */
 195       /* This could be done faster with e.g. a                  */
 196       /* balanced tree.  But the execution time here is         */
 197       /* virtually guaranteed to be dominated by the time it    */
 198       /* takes to scan the roots.                               */
 199       {
 200         register int i;
 201
 202         for (i = 0; i < n_root_sets; i++) {
 203             old = static_roots + i;
 204             if ((ptr_t)b <= old -> r_end && (ptr_t)e >= old -> r_start) {
 205                 if ((ptr_t)b < old -> r_start) {
 206                     old -> r_start = (ptr_t)b;
 207                     GC_root_size += (old -> r_start - (ptr_t)b);
 208                 }
 209                 if ((ptr_t)e > old -> r_end) {
 210                     old -> r_end = (ptr_t)e;
 211                     GC_root_size += ((ptr_t)e - old -> r_end);
 212                 }
 213                 old -> r_tmp &= tmp;
 214                 break;
 215             }
 216         }
 217         if (i < n_root_sets) {
 218           /* merge other overlapping intervals */
 219             struct roots *other;
 220
 221             for (i++; i < n_root_sets; i++) {
 222               other = static_roots + i;
 223               b = (char *)(other -> r_start);
 224               e = (char *)(other -> r_end);
 225               if ((ptr_t)b <= old -> r_end && (ptr_t)e >= old -> r_start) {
 226                 if ((ptr_t)b < old -> r_start) {
 227                     old -> r_start = (ptr_t)b;
 228                     GC_root_size += (old -> r_start - (ptr_t)b);
 229                 }
 230                 if ((ptr_t)e > old -> r_end) {
 231                     old -> r_end = (ptr_t)e;
 232                     GC_root_size += ((ptr_t)e - old -> r_end);
 233                 }
 234                 old -> r_tmp &= other -> r_tmp;
 235                 /* Delete this entry. */
 236                   GC_root_size -= (other -> r_end - other -> r_start);
 237                   other -> r_start = static_roots[n_root_sets-1].r_start;
 238                   other -> r_end = static_roots[n_root_sets-1].r_end;
 239                                   n_root_sets--;
 240               }
 241             }
 242           return;
 243         }
 244       }
 245 #   else
 246       old = GC_roots_present(b);
 247       if (old != 0) {
 248         if ((ptr_t)e <= old -> r_end) /* already there */ return;
 249         /* else extend */
 250         GC_root_size += (ptr_t)e - old -> r_end;
 251         old -> r_end = (ptr_t)e;
 252         return;
 253       }
 254 #   endif
 255     if (n_root_sets == MAX_ROOT_SETS) {
 256         ABORT("Too many root sets\n");
 257     }
 258     static_roots[n_root_sets].r_start = (ptr_t)b;
 259     static_roots[n_root_sets].r_end = (ptr_t)e;
 260     static_roots[n_root_sets].r_tmp = tmp;
 261 #   ifndef MSWIN32
 262       static_roots[n_root_sets].r_next = 0;
 263 #   endif
 264     add_roots_to_index(static_roots + n_root_sets);
 265     GC_root_size += (ptr_t)e - (ptr_t)b;
 266     n_root_sets++;
 267 }
 268
 269 void GC_clear_roots GC_PROTO((void))
 270 {
 271     DCL_LOCK_STATE;
 272
 273     DISABLE_SIGNALS();
 274     LOCK();
 275     n_root_sets = 0;
 276     GC_root_size = 0;
 277 #   ifndef MSWIN32
 278     {
 279         register int i;
 280
 281         for (i = 0; i < RT_SIZE; i++) root_index[i] = 0;
 282     }
 283 #   endif
 284     UNLOCK();
 285     ENABLE_SIGNALS();
 286 }
 287
 288 /* Internal use only; lock held.        */
 289 void GC_remove_tmp_roots()
 290 {
 291     register int i;
 292
 293     for (i = 0; i < n_root_sets; ) {
 294         if (static_roots[i].r_tmp) {
 295             GC_root_size -= (static_roots[i].r_end - static_roots[i].r_start);
 296             static_roots[i].r_start = static_roots[n_root_sets-1].r_start;
 297             static_roots[i].r_end = static_roots[n_root_sets-1].r_end;
 298             static_roots[i].r_tmp = static_roots[n_root_sets-1].r_tmp;
 299             n_root_sets--;
 300         } else {
 301             i++;
 302         }
 303     }
 304 #   ifndef MSWIN32
 305     {
 306         register int i;
 307
 308         for (i = 0; i < RT_SIZE; i++) root_index[i] = 0;
 309         for (i = 0; i < n_root_sets; i++) add_roots_to_index(static_roots + i);
 310     }
 311 #   endif
 312
 313 }
 314
 315 ptr_t GC_approx_sp()
 316 {
 317     word dummy;
 318
 319     return((ptr_t)(&dummy));
 320 }
 321
 322 /*
 323  * Data structure for excluded static roots.
 324  */
 325 struct exclusion {
 326     ptr_t e_start;
 327     ptr_t e_end;
 328 };
 329
 330 struct exclusion excl_table[MAX_EXCLUSIONS];
 331                                         /* Array of exclusions, ascending */
 332                                         /* address order.                 */
 333 size_t excl_table_entries = 0;          /* Number of entries in use.      */
 334
 335 /* Return the first exclusion range that includes an address >= start_addr */
 336 /* Assumes the exclusion table contains at least one entry (namely the     */
 337 /* GC data structures).                                                    */
 338 struct exclusion * GC_next_exclusion(start_addr)
 339 ptr_t start_addr;
 340 {
 341     size_t low = 0;
 342     size_t high = excl_table_entries - 1;
 343     size_t mid;
 344
 345     while (high > low) {
 346         mid = (low + high) >> 1;
 347         /* low <= mid < high    */
 348         if ((word) excl_table[mid].e_end <= (word) start_addr) {
 349             low = mid + 1;
 350         } else {
 351             high = mid;
 352         }
 353     }
 354     if ((word) excl_table[low].e_end <= (word) start_addr) return 0;
 355     return excl_table + low;
 356 }
 357
 358 void GC_exclude_static_roots(start, finish)
 359 GC_PTR start;
 360 GC_PTR finish;
 361 {
 362     struct exclusion * next;
 363     size_t next_index, i;
 364
 365     if (0 == excl_table_entries) {
 366         next = 0;
 367     } else {
 368         next = GC_next_exclusion(start);
 369     }
 370     if (0 != next) {
 371       if ((word)(next -> e_start) < (word) finish) {
 372         /* incomplete error check. */
 373         ABORT("exclusion ranges overlap");
 374       }
 375       if ((word)(next -> e_start) == (word) finish) {
 376         /* extend old range backwards   */
 377           next -> e_start = (ptr_t)start;
 378           return;
 379       }
 380       next_index = next - excl_table;
 381       for (i = excl_table_entries; i > next_index; --i) {
 382         excl_table[i] = excl_table[i-1];
 383       }
 384     } else {
 385       next_index = excl_table_entries;
 386     }
 387     if (excl_table_entries == MAX_EXCLUSIONS) ABORT("Too many exclusions");
 388     excl_table[next_index].e_start = (ptr_t)start;
 389     excl_table[next_index].e_end = (ptr_t)finish;
 390     ++excl_table_entries;
 391 }
 392
 393 /* Invoke push_conditional on ranges that are not excluded. */
 394 void GC_push_conditional_with_exclusions(bottom, top, all)
 395 ptr_t bottom;
 396 ptr_t top;
 397 int all;
 398 {
 399     struct exclusion * next;
 400     ptr_t excl_start;
 401
 402     while (bottom < top) {
 403         next = GC_next_exclusion(bottom);
 404         if (0 == next || (excl_start = next -> e_start) >= top) {
 405             GC_push_conditional(bottom, top, all);
 406             return;
 407         }
 408         if (excl_start > bottom) GC_push_conditional(bottom, excl_start, all);
 409         bottom = next -> e_end;
 410     }
 411 }
 412
 413 /*
 414  * Call the mark routines (GC_tl_push for a single pointer, GC_push_conditional
 415  * on groups of pointers) on every top level accessible pointer.
 416  * If all is FALSE, arrange to push only possibly altered values.
 417  */
 418
 419 void GC_push_roots(all)
 420 GC_bool all;
 421 {
 422     register int i;
 423
 424     /*
 425      * push registers - i.e., call GC_push_one(r) for each
 426      * register contents r.
 427      */
 428         GC_push_regs(); /* usually defined in machine_dep.c */
 429
 430     /*
 431      * Next push static data.  This must happen early on, since it's
 432      * not robust against mark stack overflow.
 433      */
 434      /* Reregister dynamic libraries, in case one got added.    */
 435 #      if (defined(DYNAMIC_LOADING) || defined(MSWIN32) || defined(PCR)) \
 436            && !defined(SRC_M3)
 437          GC_remove_tmp_roots();
 438          GC_register_dynamic_libraries();
 439 #      endif
 440      /* Mark everything in static data areas                             */
 441        for (i = 0; i < n_root_sets; i++) {
 442          GC_push_conditional_with_exclusions(
 443                              static_roots[i].r_start,
 444                              static_roots[i].r_end, all);
 445        }
 446
 447     /*
 448      * Now traverse stacks.
 449      */
 450 #   ifndef THREADS
 451         /* Mark everything on the stack.           */
 452 #         ifdef STACK_GROWS_DOWN
 453             GC_push_all_stack( GC_approx_sp(), GC_stackbottom );
 454 #         else
 455             GC_push_all_stack( GC_stackbottom, GC_approx_sp() );
 456 #         endif
 457 #   endif
 458     if (GC_push_other_roots != 0) (*GC_push_other_roots)();
 459         /* In the threads case, this also pushes thread stacks. */
 460 }
 461