File: checksums.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 (222 lines) | stat: -rw-r--r-- 6,809 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
/*
 * Copyright (c) 1992-1994 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"

#ifdef CHECKSUMS

/* This is debugging code intended to verify the results of dirty bit   */
/* computations. Works only in a single threaded environment.           */
/* We assume that stubborn objects are changed only when they are       */
/* enabled for writing.  (Certain kinds of writing are actually         */
/* safe under other conditions.)                                        */
#define NSUMS 10000

#define OFFSET 0x10000

typedef struct {
        GC_bool new_valid;
        word old_sum;
        word new_sum;
        struct hblk * block;    /* Block to which this refers + OFFSET  */
                                /* to hide it from collector.           */
} page_entry;

page_entry GC_sums[NSUMS];

STATIC word GC_faulted[NSUMS] = { 0 };
                /* Record of pages on which we saw a write fault.       */

STATIC size_t GC_n_faulted = 0;

#if defined(MPROTECT_VDB) && !defined(DARWIN)
  void GC_record_fault(struct hblk * h)
  {
    word page = (word)h & ~(GC_page_size - 1);

    GC_ASSERT(GC_page_size != 0);
    if (GC_n_faulted >= NSUMS) ABORT("write fault log overflowed");
    GC_faulted[GC_n_faulted++] = page;
  }
#endif

STATIC GC_bool GC_was_faulted(struct hblk *h)
{
    size_t i;
    word page = (word)h & ~(GC_page_size - 1);

    for (i = 0; i < GC_n_faulted; ++i) {
        if (GC_faulted[i] == page) return TRUE;
    }
    return FALSE;
}

STATIC word GC_checksum(struct hblk *h)
{
    word *p = (word *)h;
    word *lim = (word *)(h+1);
    word result = 0;

    while ((word)p < (word)lim) {
        result += *p++;
    }
    return(result | 0x80000000 /* doesn't look like pointer */);
}

#ifdef STUBBORN_ALLOC
  /* Check whether a stubborn object from the given block appears on    */
  /* the appropriate free list.                                         */
  STATIC GC_bool GC_on_free_list(struct hblk *h)
  {
    hdr * hhdr = HDR(h);
    size_t sz = BYTES_TO_WORDS(hhdr -> hb_sz);
    ptr_t p;

    if (sz > MAXOBJWORDS) return(FALSE);
    for (p = GC_sobjfreelist[sz]; p != 0; p = obj_link(p)) {
        if (HBLKPTR(p) == h) return(TRUE);
    }
    return(FALSE);
  }
#endif

int GC_n_dirty_errors = 0;
int GC_n_faulted_dirty_errors = 0;
int GC_n_changed_errors = 0;
unsigned long GC_n_clean = 0;
unsigned long GC_n_dirty = 0;

STATIC void GC_update_check_page(struct hblk *h, int index)
{
    page_entry *pe = GC_sums + index;
    hdr * hhdr = HDR(h);
    struct hblk *b;

    if (pe -> block != 0 && pe -> block != h + OFFSET) ABORT("goofed");
    pe -> old_sum = pe -> new_sum;
    pe -> new_sum = GC_checksum(h);
#   if !defined(MSWIN32) && !defined(MSWINCE)
        if (pe -> new_sum != 0x80000000 && !GC_page_was_ever_dirty(h)) {
            GC_err_printf("GC_page_was_ever_dirty(%p) is wrong\n", (void *)h);
        }
#   endif
    if (GC_page_was_dirty(h)) {
        GC_n_dirty++;
    } else {
        GC_n_clean++;
    }
    b = h;
    while (IS_FORWARDING_ADDR_OR_NIL(hhdr) && hhdr != 0) {
        b -= (word)hhdr;
        hhdr = HDR(b);
    }
    if (pe -> new_valid
        && hhdr != 0 && hhdr -> hb_descr != 0 /* may contain pointers */
        && pe -> old_sum != pe -> new_sum) {
        if (!GC_page_was_dirty(h) || !GC_page_was_ever_dirty(h)) {
            GC_bool was_faulted = GC_was_faulted(h);
            /* Set breakpoint here */GC_n_dirty_errors++;
            if (was_faulted) GC_n_faulted_dirty_errors++;
        }
#       ifdef STUBBORN_ALLOC
          if (!HBLK_IS_FREE(hhdr)
            && hhdr -> hb_obj_kind == STUBBORN
            && !GC_page_was_changed(h)
            && !GC_on_free_list(h)) {
            /* if GC_on_free_list(h) then reclaim may have touched it   */
            /* without any allocations taking place.                    */
            /* Set breakpoint here */GC_n_changed_errors++;
          }
#       endif
    }
    pe -> new_valid = TRUE;
    pe -> block = h + OFFSET;
}

word GC_bytes_in_used_blocks = 0;

STATIC void GC_add_block(struct hblk *h, word dummy GC_ATTR_UNUSED)
{
   hdr * hhdr = HDR(h);
   size_t bytes = hhdr -> hb_sz;

   bytes += HBLKSIZE-1;
   bytes &= ~(HBLKSIZE-1);
   GC_bytes_in_used_blocks += bytes;
}

STATIC void GC_check_blocks(void)
{
    word bytes_in_free_blocks = GC_large_free_bytes;

    GC_bytes_in_used_blocks = 0;
    GC_apply_to_all_blocks(GC_add_block, (word)0);
    GC_COND_LOG_PRINTF("GC_bytes_in_used_blocks = %lu,"
                       " bytes_in_free_blocks = %lu, heapsize = %lu\n",
                       (unsigned long)GC_bytes_in_used_blocks,
                       (unsigned long)bytes_in_free_blocks,
                       (unsigned long)GC_heapsize);
    if (GC_bytes_in_used_blocks + bytes_in_free_blocks != GC_heapsize) {
        GC_err_printf("LOST SOME BLOCKS!!\n");
    }
}

/* Should be called immediately after GC_read_dirty and GC_read_changed. */
void GC_check_dirty(void)
{
    int index;
    unsigned i;
    struct hblk *h;
    ptr_t start;

    GC_check_blocks();

    GC_n_dirty_errors = 0;
    GC_n_faulted_dirty_errors = 0;
    GC_n_changed_errors = 0;
    GC_n_clean = 0;
    GC_n_dirty = 0;

    index = 0;
    for (i = 0; i < GC_n_heap_sects; i++) {
        start = GC_heap_sects[i].hs_start;
        for (h = (struct hblk *)start;
             (word)h < (word)(start + GC_heap_sects[i].hs_bytes); h++) {
             GC_update_check_page(h, index);
             index++;
             if (index >= NSUMS) goto out;
        }
    }
out:
    GC_COND_LOG_PRINTF("Checked %lu clean and %lu dirty pages\n",
                       GC_n_clean, GC_n_dirty);
    if (GC_n_dirty_errors > 0) {
        GC_err_printf("Found %d dirty bit errors (%d were faulted)\n",
                      GC_n_dirty_errors, GC_n_faulted_dirty_errors);
    }
    if (GC_n_changed_errors > 0) {
        GC_err_printf("Found %d changed bit errors\n", GC_n_changed_errors);
        GC_err_printf(
                "These may be benign (provoked by nonpointer changes)\n");
#       ifdef THREADS
          GC_err_printf(
            "Also expect 1 per thread currently allocating a stubborn obj\n");
#       endif
    }
    for (i = 0; i < GC_n_faulted; ++i) {
        GC_faulted[i] = 0; /* Don't expose block pointers to GC */
    }
    GC_n_faulted = 0;
}

#endif /* CHECKSUMS */