libgc/checksums.c

   1 /*
   2  * Copyright (c) 1992-1994 by Xerox Corporation.  All rights reserved.
   3  *
   4  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   5  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   6  *
   7  * Permission is hereby granted to use or copy this program
   8  * for any purpose,  provided the above notices are retained on all copies.
   9  * Permission to modify the code and to distribute modified code is granted,
  10  * provided the above notices are retained, and a notice that the code was
  11  * modified is included with the above copyright notice.
  12  */
  13 /* Boehm, March 29, 1995 12:51 pm PST */
  14 # ifdef CHECKSUMS
  15
  16 # include "private/gc_priv.h"
  17
  18 /* This is debugging code intended to verify the results of dirty bit   */
  19 /* computations. Works only in a single threaded environment.           */
  20 /* We assume that stubborn objects are changed only when they are       */
  21 /* enabled for writing.  (Certain kinds of writing are actually         */
  22 /* safe under other conditions.)                                        */
  23 # define NSUMS 10000
  24
  25 # define OFFSET 0x10000
  26
  27 typedef struct {
  28         GC_bool new_valid;
  29         word old_sum;
  30         word new_sum;
  31         struct hblk * block;    /* Block to which this refers + OFFSET  */
  32                                 /* to hide it from collector.           */
  33 } page_entry;
  34
  35 page_entry GC_sums [NSUMS];
  36
  37 word GC_checksum(h)
  38 struct hblk *h;
  39 {
  40     register word *p = (word *)h;
  41     register word *lim = (word *)(h+1);
  42     register word result = 0;
  43
  44     while (p < lim) {
  45         result += *p++;
  46     }
  47     return(result | 0x80000000 /* doesn't look like pointer */);
  48 }
  49
  50 # ifdef STUBBORN_ALLOC
  51 /* Check whether a stubborn object from the given block appears on      */
  52 /* the appropriate free list.                                           */
  53 GC_bool GC_on_free_list(h)
  54 struct hblk *h;
  55 {
  56     register hdr * hhdr = HDR(h);
  57     register int sz = hhdr -> hb_sz;
  58     ptr_t p;
  59
  60     if (sz > MAXOBJSZ) return(FALSE);
  61     for (p = GC_sobjfreelist[sz]; p != 0; p = obj_link(p)) {
  62         if (HBLKPTR(p) == h) return(TRUE);
  63     }
  64     return(FALSE);
  65 }
  66 # endif
  67
  68 int GC_n_dirty_errors;
  69 int GC_n_changed_errors;
  70 int GC_n_clean;
  71 int GC_n_dirty;
  72
  73 void GC_update_check_page(h, index)
  74 struct hblk *h;
  75 int index;
  76 {
  77     page_entry *pe = GC_sums + index;
  78     register hdr * hhdr = HDR(h);
  79     struct hblk *b;
  80
  81     if (pe -> block != 0 && pe -> block != h + OFFSET) ABORT("goofed");
  82     pe -> old_sum = pe -> new_sum;
  83     pe -> new_sum = GC_checksum(h);
  84 #   if !defined(MSWIN32) && !defined(MSWINCE)
  85         if (pe -> new_sum != 0x80000000 && !GC_page_was_ever_dirty(h)) {
  86             GC_printf1("GC_page_was_ever_dirty(0x%lx) is wrong\n",
  87                        (unsigned long)h);
  88         }
  89 #   endif
  90     if (GC_page_was_dirty(h)) {
  91         GC_n_dirty++;
  92     } else {
  93         GC_n_clean++;
  94     }
  95     b = h;
  96     while (IS_FORWARDING_ADDR_OR_NIL(hhdr) && hhdr != 0) {
  97         b -= (word)hhdr;
  98         hhdr = HDR(b);
  99     }
 100     if (pe -> new_valid
 101         && hhdr != 0 && hhdr -> hb_descr != 0 /* may contain pointers */
 102         && pe -> old_sum != pe -> new_sum) {
 103         if (!GC_page_was_dirty(h) || !GC_page_was_ever_dirty(h)) {
 104             /* Set breakpoint here */GC_n_dirty_errors++;
 105         }
 106 #       ifdef STUBBORN_ALLOC
 107           if ( hhdr -> hb_map != GC_invalid_map
 108             && hhdr -> hb_obj_kind == STUBBORN
 109             && !GC_page_was_changed(h)
 110             && !GC_on_free_list(h)) {
 111             /* if GC_on_free_list(h) then reclaim may have touched it   */
 112             /* without any allocations taking place.                    */
 113             /* Set breakpoint here */GC_n_changed_errors++;
 114           }
 115 #       endif
 116     }
 117     pe -> new_valid = TRUE;
 118     pe -> block = h + OFFSET;
 119 }
 120
 121 word GC_bytes_in_used_blocks;
 122
 123 void GC_add_block(h, dummy)
 124 struct hblk *h;
 125 word dummy;
 126 {
 127    register hdr * hhdr = HDR(h);
 128    register bytes = WORDS_TO_BYTES(hhdr -> hb_sz);
 129
 130    bytes += HBLKSIZE-1;
 131    bytes &= ~(HBLKSIZE-1);
 132    GC_bytes_in_used_blocks += bytes;
 133 }
 134
 135 void GC_check_blocks()
 136 {
 137     word bytes_in_free_blocks = GC_large_free_bytes;
 138
 139     GC_bytes_in_used_blocks = 0;
 140     GC_apply_to_all_blocks(GC_add_block, (word)0);
 141     GC_printf2("GC_bytes_in_used_blocks = %ld, bytes_in_free_blocks = %ld ",
 142                 GC_bytes_in_used_blocks, bytes_in_free_blocks);
 143     GC_printf1("GC_heapsize = %ld\n", GC_heapsize);
 144     if (GC_bytes_in_used_blocks + bytes_in_free_blocks != GC_heapsize) {
 145         GC_printf0("LOST SOME BLOCKS!!\n");
 146     }
 147 }
 148
 149 /* Should be called immediately after GC_read_dirty and GC_read_changed. */
 150 void GC_check_dirty()
 151 {
 152     register int index;
 153     register unsigned i;
 154     register struct hblk *h;
 155     register ptr_t start;
 156
 157     GC_check_blocks();
 158
 159     GC_n_dirty_errors = 0;
 160     GC_n_changed_errors = 0;
 161     GC_n_clean = 0;
 162     GC_n_dirty = 0;
 163
 164     index = 0;
 165     for (i = 0; i < GC_n_heap_sects; i++) {
 166         start = GC_heap_sects[i].hs_start;
 167         for (h = (struct hblk *)start;
 168              h < (struct hblk *)(start + GC_heap_sects[i].hs_bytes);
 169              h++) {
 170              GC_update_check_page(h, index);
 171              index++;
 172              if (index >= NSUMS) goto out;
 173         }
 174     }
 175 out:
 176     GC_printf2("Checked %lu clean and %lu dirty pages\n",
 177               (unsigned long) GC_n_clean, (unsigned long) GC_n_dirty);
 178     if (GC_n_dirty_errors > 0) {
 179         GC_printf1("Found %lu dirty bit errors\n",
 180                    (unsigned long)GC_n_dirty_errors);
 181     }
 182     if (GC_n_changed_errors > 0) {
 183         GC_printf1("Found %lu changed bit errors\n",
 184                    (unsigned long)GC_n_changed_errors);
 185         GC_printf0("These may be benign (provoked by nonpointer changes)\n");
 186 #       ifdef THREADS
 187             GC_printf0(
 188             "Also expect 1 per thread currently allocating a stubborn obj.\n");
 189 #       endif
 190     }
 191 }
 192
 193 # else
 194
 195 extern int GC_quiet;
 196         /* ANSI C doesn't allow translation units to be empty.  */
 197         /* So we guarantee this one is nonempty.                */
 198
 199 # endif /* CHECKSUMS */