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
14 #include "private/gc_priv.h"
15
16 #ifdef CHECKSUMS
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 STATIC word GC_faulted[NSUMS] = { 0 };
38 /* Record of pages on which we saw a write fault. */
39
40 STATIC size_t GC_n_faulted = 0;
41
GC_record_fault(struct hblk * h)42 void GC_record_fault(struct hblk * h)
43 {
44 word page = (word)h;
45
46 page += GC_page_size - 1;
47 page &= ~(GC_page_size - 1);
48 if (GC_n_faulted >= NSUMS) ABORT("write fault log overflowed");
49 GC_faulted[GC_n_faulted++] = page;
50 }
51
GC_was_faulted(struct hblk * h)52 STATIC GC_bool GC_was_faulted(struct hblk *h)
53 {
54 size_t i;
55 word page = (word)h;
56
57 page += GC_page_size - 1;
58 page &= ~(GC_page_size - 1);
59 for (i = 0; i < GC_n_faulted; ++i) {
60 if (GC_faulted[i] == page) return TRUE;
61 }
62 return FALSE;
63 }
64
GC_checksum(struct hblk * h)65 STATIC word GC_checksum(struct hblk *h)
66 {
67 word *p = (word *)h;
68 word *lim = (word *)(h+1);
69 word result = 0;
70
71 while (p < lim) {
72 result += *p++;
73 }
74 return(result | 0x80000000 /* doesn't look like pointer */);
75 }
76
77 #ifdef STUBBORN_ALLOC
78 /* Check whether a stubborn object from the given block appears on */
79 /* the appropriate free list. */
GC_on_free_list(struct hblk * h)80 STATIC GC_bool GC_on_free_list(struct hblk *h)
81 {
82 hdr * hhdr = HDR(h);
83 size_t sz = BYTES_TO_WORDS(hhdr -> hb_sz);
84 ptr_t p;
85
86 if (sz > MAXOBJWORDS) return(FALSE);
87 for (p = GC_sobjfreelist[sz]; p != 0; p = obj_link(p)) {
88 if (HBLKPTR(p) == h) return(TRUE);
89 }
90 return(FALSE);
91 }
92 #endif
93
94 int GC_n_dirty_errors = 0;
95 int GC_n_faulted_dirty_errors = 0;
96 int GC_n_changed_errors = 0;
97 int GC_n_clean = 0;
98 int GC_n_dirty = 0;
99
100 GC_INNER GC_bool GC_page_was_ever_dirty(struct hblk * h);
101
GC_update_check_page(struct hblk * h,int index)102 STATIC void GC_update_check_page(struct hblk *h, int index)
103 {
104 page_entry *pe = GC_sums + index;
105 hdr * hhdr = HDR(h);
106 struct hblk *b;
107
108 if (pe -> block != 0 && pe -> block != h + OFFSET) ABORT("goofed");
109 pe -> old_sum = pe -> new_sum;
110 pe -> new_sum = GC_checksum(h);
111 # if !defined(MSWIN32) && !defined(MSWINCE)
112 if (pe -> new_sum != 0x80000000 && !GC_page_was_ever_dirty(h)) {
113 GC_err_printf("GC_page_was_ever_dirty(%p) is wrong\n", h);
114 }
115 # endif
116 if (GC_page_was_dirty(h)) {
117 GC_n_dirty++;
118 } else {
119 GC_n_clean++;
120 }
121 b = h;
122 while (IS_FORWARDING_ADDR_OR_NIL(hhdr) && hhdr != 0) {
123 b -= (word)hhdr;
124 hhdr = HDR(b);
125 }
126 if (pe -> new_valid
127 && hhdr != 0 && hhdr -> hb_descr != 0 /* may contain pointers */
128 && pe -> old_sum != pe -> new_sum) {
129 if (!GC_page_was_dirty(h) || !GC_page_was_ever_dirty(h)) {
130 GC_bool was_faulted = GC_was_faulted(h);
131 /* Set breakpoint here */GC_n_dirty_errors++;
132 if (was_faulted) GC_n_faulted_dirty_errors++;
133 }
134 # ifdef STUBBORN_ALLOC
135 if (!HBLK_IS_FREE(hhdr)
136 && hhdr -> hb_obj_kind == STUBBORN
137 && !GC_page_was_changed(h)
138 && !GC_on_free_list(h)) {
139 /* if GC_on_free_list(h) then reclaim may have touched it */
140 /* without any allocations taking place. */
141 /* Set breakpoint here */GC_n_changed_errors++;
142 }
143 # endif
144 }
145 pe -> new_valid = TRUE;
146 pe -> block = h + OFFSET;
147 }
148
149 word GC_bytes_in_used_blocks = 0;
150
151 /*ARGSUSED*/
GC_add_block(struct hblk * h,word dummy)152 STATIC void GC_add_block(struct hblk *h, word dummy)
153 {
154 hdr * hhdr = HDR(h);
155 size_t bytes = hhdr -> hb_sz;
156
157 bytes += HBLKSIZE-1;
158 bytes &= ~(HBLKSIZE-1);
159 GC_bytes_in_used_blocks += bytes;
160 }
161
GC_check_blocks(void)162 STATIC void GC_check_blocks(void)
163 {
164 word bytes_in_free_blocks = GC_large_free_bytes;
165
166 GC_bytes_in_used_blocks = 0;
167 GC_apply_to_all_blocks(GC_add_block, (word)0);
168 if (GC_print_stats)
169 GC_log_printf("GC_bytes_in_used_blocks = %lu,"
170 " bytes_in_free_blocks = %lu, heapsize = %lu\n",
171 (unsigned long)GC_bytes_in_used_blocks,
172 (unsigned long)bytes_in_free_blocks,
173 (unsigned long)GC_heapsize);
174 if (GC_bytes_in_used_blocks + bytes_in_free_blocks != GC_heapsize) {
175 GC_err_printf("LOST SOME BLOCKS!!\n");
176 }
177 }
178
179 /* Should be called immediately after GC_read_dirty and GC_read_changed. */
GC_check_dirty(void)180 void GC_check_dirty(void)
181 {
182 int index;
183 unsigned i;
184 struct hblk *h;
185 ptr_t start;
186
187 GC_check_blocks();
188
189 GC_n_dirty_errors = 0;
190 GC_n_faulted_dirty_errors = 0;
191 GC_n_changed_errors = 0;
192 GC_n_clean = 0;
193 GC_n_dirty = 0;
194
195 index = 0;
196 for (i = 0; i < GC_n_heap_sects; i++) {
197 start = GC_heap_sects[i].hs_start;
198 for (h = (struct hblk *)start;
199 h < (struct hblk *)(start + GC_heap_sects[i].hs_bytes);
200 h++) {
201 GC_update_check_page(h, index);
202 index++;
203 if (index >= NSUMS) goto out;
204 }
205 }
206 out:
207 if (GC_print_stats)
208 GC_log_printf("Checked %lu clean and %lu dirty pages\n",
209 (unsigned long)GC_n_clean, (unsigned long)GC_n_dirty);
210 if (GC_n_dirty_errors > 0) {
211 GC_err_printf("Found %d dirty bit errors (%d were faulted)\n",
212 GC_n_dirty_errors, GC_n_faulted_dirty_errors);
213 }
214 if (GC_n_changed_errors > 0) {
215 GC_err_printf("Found %lu changed bit errors\n",
216 (unsigned long)GC_n_changed_errors);
217 GC_err_printf(
218 "These may be benign (provoked by nonpointer changes)\n");
219 # ifdef THREADS
220 GC_err_printf(
221 "Also expect 1 per thread currently allocating a stubborn obj\n");
222 # endif
223 }
224 for (i = 0; i < GC_n_faulted; ++i) {
225 GC_faulted[i] = 0; /* Don't expose block pointers to GC */
226 }
227 GC_n_faulted = 0;
228 }
229
230 #endif /* CHECKSUMS */
231