File: blacklst.c

package info (click to toggle)
libgc 1:7.6.4-0.4
  • links: PTS
  • area: main
  • in suites: bullseye, buster, sid
  • size: 4,956 kB
  • sloc: ansic: 35,613; sh: 4,193; cpp: 1,247; makefile: 163; asm: 99
file content (290 lines) | stat: -rw-r--r-- 10,379 bytes parent folder | download | duplicates (2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
/*
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to use or copy this program
 * for any purpose,  provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is granted,
 * provided the above notices are retained, and a notice that the code was
 * modified is included with the above copyright notice.
 */

#include "private/gc_priv.h"

/*
 * We maintain several hash tables of hblks that have had false hits.
 * Each contains one bit per hash bucket;  If any page in the bucket
 * has had a false hit, we assume that all of them have.
 * See the definition of page_hash_table in gc_private.h.
 * False hits from the stack(s) are much more dangerous than false hits
 * from elsewhere, since the former can pin a large object that spans the
 * block, even though it does not start on the dangerous block.
 */

/*
 * Externally callable routines are:

 * GC_add_to_black_list_normal
 * GC_add_to_black_list_stack
 * GC_promote_black_lists
 * GC_is_black_listed
 *
 * All require that the allocator lock is held.
 */

/* Pointers to individual tables.  We replace one table by another by   */
/* switching these pointers.                                            */
STATIC word * GC_old_normal_bl = NULL;
                /* Nonstack false references seen at last full          */
                /* collection.                                          */
STATIC word * GC_incomplete_normal_bl = NULL;
                /* Nonstack false references seen since last            */
                /* full collection.                                     */
STATIC word * GC_old_stack_bl = NULL;
STATIC word * GC_incomplete_stack_bl = NULL;

STATIC word GC_total_stack_black_listed = 0;
                        /* Number of bytes on stack blacklist.  */

GC_INNER word GC_black_list_spacing = MINHINCR * HBLKSIZE;
                        /* Initial rough guess. */

STATIC void GC_clear_bl(word *);

GC_INNER void GC_default_print_heap_obj_proc(ptr_t p)
{
    ptr_t base = GC_base(p);
    int kind = HDR(base)->hb_obj_kind;

    GC_err_printf("object at %p of appr. %lu bytes (%s)\n",
                  (void *)base, (unsigned long)GC_size(base),
                  kind == PTRFREE ? "atomic" :
                    IS_UNCOLLECTABLE(kind) ? "uncollectable" : "composite");
}

GC_INNER void (*GC_print_heap_obj)(ptr_t p) = GC_default_print_heap_obj_proc;

#ifdef PRINT_BLACK_LIST
  STATIC void GC_print_blacklisted_ptr(word p, ptr_t source,
                                       const char *kind_str)
  {
    ptr_t base = GC_base(source);

    if (0 == base) {
        GC_err_printf("Black listing (%s) %p referenced from %p in %s\n",
                      kind_str, (void *)p, (void *)source,
                      NULL != source ? "root set" : "register");
    } else {
        /* FIXME: We can't call the debug version of GC_print_heap_obj  */
        /* (with PRINT_CALL_CHAIN) here because the lock is held and    */
        /* the world is stopped.                                        */
        GC_err_printf("Black listing (%s) %p referenced from %p in"
                      " object at %p of appr. %lu bytes\n",
                      kind_str, (void *)p, (void *)source,
                      (void *)base, (unsigned long)GC_size(base));
    }
  }
#endif /* PRINT_BLACK_LIST */

GC_INNER void GC_bl_init_no_interiors(void)
{
  if (GC_incomplete_normal_bl == 0) {
    GC_old_normal_bl = (word *)GC_scratch_alloc(sizeof(page_hash_table));
    GC_incomplete_normal_bl = (word *)GC_scratch_alloc(
                                                  sizeof(page_hash_table));
    if (GC_old_normal_bl == 0 || GC_incomplete_normal_bl == 0) {
      GC_err_printf("Insufficient memory for black list\n");
      EXIT();
    }
    GC_clear_bl(GC_old_normal_bl);
    GC_clear_bl(GC_incomplete_normal_bl);
  }
}

GC_INNER void GC_bl_init(void)
{
    if (!GC_all_interior_pointers) {
      GC_bl_init_no_interiors();
    }
    GC_ASSERT(NULL == GC_old_stack_bl && NULL == GC_incomplete_stack_bl);
    GC_old_stack_bl = (word *)GC_scratch_alloc(sizeof(page_hash_table));
    GC_incomplete_stack_bl = (word *)GC_scratch_alloc(sizeof(page_hash_table));
    if (GC_old_stack_bl == 0 || GC_incomplete_stack_bl == 0) {
        GC_err_printf("Insufficient memory for black list\n");
        EXIT();
    }
    GC_clear_bl(GC_old_stack_bl);
    GC_clear_bl(GC_incomplete_stack_bl);
}

STATIC void GC_clear_bl(word *doomed)
{
    BZERO(doomed, sizeof(page_hash_table));
}

STATIC void GC_copy_bl(word *old, word *new)
{
    BCOPY(old, new, sizeof(page_hash_table));
}

static word total_stack_black_listed(void);

/* Signal the completion of a collection.  Turn the incomplete black    */
/* lists into new black lists, etc.                                     */
GC_INNER void GC_promote_black_lists(void)
{
    word * very_old_normal_bl = GC_old_normal_bl;
    word * very_old_stack_bl = GC_old_stack_bl;

    GC_old_normal_bl = GC_incomplete_normal_bl;
    GC_old_stack_bl = GC_incomplete_stack_bl;
    if (!GC_all_interior_pointers) {
      GC_clear_bl(very_old_normal_bl);
    }
    GC_clear_bl(very_old_stack_bl);
    GC_incomplete_normal_bl = very_old_normal_bl;
    GC_incomplete_stack_bl = very_old_stack_bl;
    GC_total_stack_black_listed = total_stack_black_listed();
    GC_VERBOSE_LOG_PRINTF(
                "%lu bytes in heap blacklisted for interior pointers\n",
                (unsigned long)GC_total_stack_black_listed);
    if (GC_total_stack_black_listed != 0) {
        GC_black_list_spacing =
                HBLKSIZE*(GC_heapsize/GC_total_stack_black_listed);
    }
    if (GC_black_list_spacing < 3 * HBLKSIZE) {
        GC_black_list_spacing = 3 * HBLKSIZE;
    }
    if (GC_black_list_spacing > MAXHINCR * HBLKSIZE) {
        GC_black_list_spacing = MAXHINCR * HBLKSIZE;
        /* Makes it easier to allocate really huge blocks, which otherwise */
        /* may have problems with nonuniform blacklist distributions.      */
        /* This way we should always succeed immediately after growing the */
        /* heap.                                                           */
    }
}

GC_INNER void GC_unpromote_black_lists(void)
{
    if (!GC_all_interior_pointers) {
      GC_copy_bl(GC_old_normal_bl, GC_incomplete_normal_bl);
    }
    GC_copy_bl(GC_old_stack_bl, GC_incomplete_stack_bl);
}

/* P is not a valid pointer reference, but it falls inside      */
/* the plausible heap bounds.                                   */
/* Add it to the normal incomplete black list if appropriate.   */
#ifdef PRINT_BLACK_LIST
  GC_INNER void GC_add_to_black_list_normal(word p, ptr_t source)
#else
  GC_INNER void GC_add_to_black_list_normal(word p)
#endif
{
  if (GC_modws_valid_offsets[p & (sizeof(word)-1)]) {
    word index = PHT_HASH((word)p);

    if (HDR(p) == 0 || get_pht_entry_from_index(GC_old_normal_bl, index)) {
#     ifdef PRINT_BLACK_LIST
        if (!get_pht_entry_from_index(GC_incomplete_normal_bl, index)) {
          GC_print_blacklisted_ptr(p, source, "normal");
        }
#     endif
      set_pht_entry_from_index(GC_incomplete_normal_bl, index);
    } /* else this is probably just an interior pointer to an allocated */
      /* object, and isn't worth black listing.                         */
  }
}

/* And the same for false pointers from the stack. */
#ifdef PRINT_BLACK_LIST
  GC_INNER void GC_add_to_black_list_stack(word p, ptr_t source)
#else
  GC_INNER void GC_add_to_black_list_stack(word p)
#endif
{
  word index = PHT_HASH((word)p);

  if (HDR(p) == 0 || get_pht_entry_from_index(GC_old_stack_bl, index)) {
#   ifdef PRINT_BLACK_LIST
      if (!get_pht_entry_from_index(GC_incomplete_stack_bl, index)) {
        GC_print_blacklisted_ptr(p, source, "stack");
      }
#   endif
    set_pht_entry_from_index(GC_incomplete_stack_bl, index);
  }
}

/*
 * Is the block starting at h of size len bytes black listed?   If so,
 * return the address of the next plausible r such that (r, len) might not
 * be black listed.  (R may not actually be in the heap.  We guarantee only
 * that every smaller value of r after h is also black listed.)
 * If (h,len) is not black listed, return 0.
 * Knows about the structure of the black list hash tables.
 */
struct hblk * GC_is_black_listed(struct hblk *h, word len)
{
    word index = PHT_HASH((word)h);
    word i;
    word nblocks;

    if (!GC_all_interior_pointers
        && (get_pht_entry_from_index(GC_old_normal_bl, index)
            || get_pht_entry_from_index(GC_incomplete_normal_bl, index))) {
      return (h+1);
    }

    nblocks = divHBLKSZ(len);
    for (i = 0;;) {
        if (GC_old_stack_bl[divWORDSZ(index)] == 0
            && GC_incomplete_stack_bl[divWORDSZ(index)] == 0) {
            /* An easy case */
          i += WORDSZ - modWORDSZ(index);
        } else {
          if (get_pht_entry_from_index(GC_old_stack_bl, index)
              || get_pht_entry_from_index(GC_incomplete_stack_bl, index)) {
            return(h+i+1);
          }
          i++;
        }
        if (i >= nblocks) break;
        index = PHT_HASH((word)(h+i));
    }
    return(0);
}

/* Return the number of blacklisted blocks in a given range.    */
/* Used only for statistical purposes.                          */
/* Looks only at the GC_incomplete_stack_bl.                    */
STATIC word GC_number_stack_black_listed(struct hblk *start,
                                         struct hblk *endp1)
{
    register struct hblk * h;
    word result = 0;

    for (h = start; (word)h < (word)endp1; h++) {
        word index = PHT_HASH((word)h);

        if (get_pht_entry_from_index(GC_old_stack_bl, index)) result++;
    }
    return(result);
}

/* Return the total number of (stack) black-listed bytes. */
static word total_stack_black_listed(void)
{
    register unsigned i;
    word total = 0;

    for (i = 0; i < GC_n_heap_sects; i++) {
        struct hblk * start = (struct hblk *) GC_heap_sects[i].hs_start;
        struct hblk * endp1 = start + divHBLKSZ(GC_heap_sects[i].hs_bytes);

        total += GC_number_stack_black_listed(start, endp1);
    }
    return(total * HBLKSIZE);
}