1 /*
2 * Copyright (c) 1991-1994 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 /*
15 * These are checking routines calls to which could be inserted by a
16 * preprocessor to validate C pointer arithmetic.
17 */
18
19 #include "private/gc_pmark.h"
20
21 #ifdef __STDC__
GC_default_same_obj_print_proc(GC_PTR p,GC_PTR q)22 void GC_default_same_obj_print_proc(GC_PTR p, GC_PTR q)
23 #else
24 void GC_default_same_obj_print_proc (p, q)
25 GC_PTR p, q;
26 #endif
27 {
28 GC_err_printf2("0x%lx and 0x%lx are not in the same object\n",
29 (unsigned long)p, (unsigned long)q);
30 ABORT("GC_same_obj test failed");
31 }
32
33 void (*GC_same_obj_print_proc) GC_PROTO((GC_PTR, GC_PTR))
34 = GC_default_same_obj_print_proc;
35
36 /* Check that p and q point to the same object. Call */
37 /* *GC_same_obj_print_proc if they don't. */
38 /* Returns the first argument. (Return value may be hard */
39 /* to use,due to typing issues. But if we had a suitable */
40 /* preprocessor ...) */
41 /* Succeeds if neither p nor q points to the heap. */
42 /* We assume this is performance critical. (It shouldn't */
43 /* be called by production code, but this can easily make */
44 /* debugging intolerably slow.) */
45 #ifdef __STDC__
GC_same_obj(register void * p,register void * q)46 GC_PTR GC_same_obj(register void *p, register void *q)
47 #else
48 GC_PTR GC_same_obj(p, q)
49 register char *p, *q;
50 #endif
51 {
52 register struct hblk *h;
53 register hdr *hhdr;
54 register ptr_t base, limit;
55 register word sz;
56
57 if (!GC_is_initialized) GC_init();
58 hhdr = HDR((word)p);
59 if (hhdr == 0) {
60 if (divHBLKSZ((word)p) != divHBLKSZ((word)q)
61 && HDR((word)q) != 0) {
62 goto fail;
63 }
64 return(p);
65 }
66 /* If it's a pointer to the middle of a large object, move it */
67 /* to the beginning. */
68 if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
69 h = HBLKPTR(p) - (word)hhdr;
70 hhdr = HDR(h);
71 while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
72 h = FORWARDED_ADDR(h, hhdr);
73 hhdr = HDR(h);
74 }
75 limit = (ptr_t)((word *)h + hhdr -> hb_sz);
76 if ((ptr_t)p >= limit || (ptr_t)q >= limit || (ptr_t)q < (ptr_t)h ) {
77 goto fail;
78 }
79 return(p);
80 }
81 sz = WORDS_TO_BYTES(hhdr -> hb_sz);
82 if (sz > MAXOBJBYTES) {
83 base = (ptr_t)HBLKPTR(p);
84 limit = base + sz;
85 if ((ptr_t)p >= limit) {
86 goto fail;
87 }
88 } else {
89 register int map_entry;
90 register int pdispl = HBLKDISPL(p);
91
92 map_entry = MAP_ENTRY((hhdr -> hb_map), pdispl);
93 if (map_entry > CPP_MAX_OFFSET) {
94 map_entry = BYTES_TO_WORDS(pdispl) % BYTES_TO_WORDS(sz);
95 if (HBLKPTR(p) != HBLKPTR(q)) goto fail;
96 /* W/o this check, we might miss an error if */
97 /* q points to the first object on a page, and */
98 /* points just before the page. */
99 }
100 base = (char *)((word)p & ~(WORDS_TO_BYTES(1) - 1));
101 base -= WORDS_TO_BYTES(map_entry);
102 limit = base + sz;
103 }
104 /* [base, limit) delimits the object containing p, if any. */
105 /* If p is not inside a valid object, then either q is */
106 /* also outside any valid object, or it is outside */
107 /* [base, limit). */
108 if ((ptr_t)q >= limit || (ptr_t)q < base) {
109 goto fail;
110 }
111 return(p);
112 fail:
113 (*GC_same_obj_print_proc)((ptr_t)p, (ptr_t)q);
114 return(p);
115 }
116
117 #ifdef __STDC__
GC_default_is_valid_displacement_print_proc(GC_PTR p)118 void GC_default_is_valid_displacement_print_proc (GC_PTR p)
119 #else
120 void GC_default_is_valid_displacement_print_proc (p)
121 GC_PTR p;
122 #endif
123 {
124 GC_err_printf1("0x%lx does not point to valid object displacement\n",
125 (unsigned long)p);
126 ABORT("GC_is_valid_displacement test failed");
127 }
128
129 void (*GC_is_valid_displacement_print_proc) GC_PROTO((GC_PTR)) =
130 GC_default_is_valid_displacement_print_proc;
131
132 /* Check that if p is a pointer to a heap page, then it points to */
133 /* a valid displacement within a heap object. */
134 /* Uninteresting with GC_all_interior_pointers. */
135 /* Always returns its argument. */
136 /* Note that we don't lock, since nothing relevant about the header */
137 /* should change while we have a valid object pointer to the block. */
138 #ifdef __STDC__
GC_is_valid_displacement(void * p)139 void * GC_is_valid_displacement(void *p)
140 #else
141 char *GC_is_valid_displacement(p)
142 char *p;
143 #endif
144 {
145 register hdr *hhdr;
146 register word pdispl;
147 register struct hblk *h;
148 register map_entry_type map_entry;
149 register word sz;
150
151 if (!GC_is_initialized) GC_init();
152 hhdr = HDR((word)p);
153 if (hhdr == 0) return(p);
154 h = HBLKPTR(p);
155 if (GC_all_interior_pointers) {
156 while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
157 h = FORWARDED_ADDR(h, hhdr);
158 hhdr = HDR(h);
159 }
160 }
161 if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
162 goto fail;
163 }
164 sz = WORDS_TO_BYTES(hhdr -> hb_sz);
165 pdispl = HBLKDISPL(p);
166 map_entry = MAP_ENTRY((hhdr -> hb_map), pdispl);
167 if (map_entry == OBJ_INVALID
168 || sz > MAXOBJBYTES && (ptr_t)p >= (ptr_t)h + sz) {
169 goto fail;
170 }
171 return(p);
172 fail:
173 (*GC_is_valid_displacement_print_proc)((ptr_t)p);
174 return(p);
175 }
176
177 #ifdef __STDC__
GC_default_is_visible_print_proc(GC_PTR p)178 void GC_default_is_visible_print_proc(GC_PTR p)
179 #else
180 void GC_default_is_visible_print_proc(p)
181 GC_PTR p;
182 #endif
183 {
184 GC_err_printf1("0x%lx is not a GC visible pointer location\n",
185 (unsigned long)p);
186 ABORT("GC_is_visible test failed");
187 }
188
189 void (*GC_is_visible_print_proc) GC_PROTO((GC_PTR p)) =
190 GC_default_is_visible_print_proc;
191
192 /* Could p be a stack address? */
GC_on_stack(p)193 GC_bool GC_on_stack(p)
194 ptr_t p;
195 {
196 # ifdef THREADS
197 return(TRUE);
198 # else
199 int dummy;
200 # ifdef STACK_GROWS_DOWN
201 if ((ptr_t)p >= (ptr_t)(&dummy) && (ptr_t)p < GC_stackbottom ) {
202 return(TRUE);
203 }
204 # else
205 if ((ptr_t)p <= (ptr_t)(&dummy) && (ptr_t)p > GC_stackbottom ) {
206 return(TRUE);
207 }
208 # endif
209 return(FALSE);
210 # endif
211 }
212
213 /* Check that p is visible */
214 /* to the collector as a possibly pointer containing location. */
215 /* If it isn't invoke *GC_is_visible_print_proc. */
216 /* Returns the argument in all cases. May erroneously succeed */
217 /* in hard cases. (This is intended for debugging use with */
218 /* untyped allocations. The idea is that it should be possible, though */
219 /* slow, to add such a call to all indirect pointer stores.) */
220 /* Currently useless for multithreaded worlds. */
221 #ifdef __STDC__
GC_is_visible(void * p)222 void * GC_is_visible(void *p)
223 #else
224 char *GC_is_visible(p)
225 char *p;
226 #endif
227 {
228 register hdr *hhdr;
229
230 if ((word)p & (ALIGNMENT - 1)) goto fail;
231 if (!GC_is_initialized) GC_init();
232 # ifdef THREADS
233 hhdr = HDR((word)p);
234 if (hhdr != 0 && GC_base(p) == 0) {
235 goto fail;
236 } else {
237 /* May be inside thread stack. We can't do much. */
238 return(p);
239 }
240 # else
241 /* Check stack first: */
242 if (GC_on_stack(p)) return(p);
243 hhdr = HDR((word)p);
244 if (hhdr == 0) {
245 GC_bool result;
246
247 if (GC_is_static_root(p)) return(p);
248 /* Else do it again correctly: */
249 # if (defined(DYNAMIC_LOADING) || defined(MSWIN32) || \
250 defined(MSWINCE) || defined(PCR)) \
251 && !defined(SRC_M3)
252 DISABLE_SIGNALS();
253 GC_register_dynamic_libraries();
254 result = GC_is_static_root(p);
255 ENABLE_SIGNALS();
256 if (result) return(p);
257 # endif
258 goto fail;
259 } else {
260 /* p points to the heap. */
261 word descr;
262 ptr_t base = GC_base(p); /* Should be manually inlined? */
263
264 if (base == 0) goto fail;
265 if (HBLKPTR(base) != HBLKPTR(p)) hhdr = HDR((word)p);
266 descr = hhdr -> hb_descr;
267 retry:
268 switch(descr & GC_DS_TAGS) {
269 case GC_DS_LENGTH:
270 if ((word)((ptr_t)p - (ptr_t)base) > (word)descr) goto fail;
271 break;
272 case GC_DS_BITMAP:
273 if ((ptr_t)p - (ptr_t)base
274 >= WORDS_TO_BYTES(BITMAP_BITS)
275 || ((word)p & (sizeof(word) - 1))) goto fail;
276 if (!((1 << (WORDSZ - ((ptr_t)p - (ptr_t)base) - 1))
277 & descr)) goto fail;
278 break;
279 case GC_DS_PROC:
280 /* We could try to decipher this partially. */
281 /* For now we just punt. */
282 break;
283 case GC_DS_PER_OBJECT:
284 if ((signed_word)descr >= 0) {
285 descr = *(word *)((ptr_t)base + (descr & ~GC_DS_TAGS));
286 } else {
287 ptr_t type_descr = *(ptr_t *)base;
288 descr = *(word *)(type_descr
289 - (descr - (GC_DS_PER_OBJECT
290 - GC_INDIR_PER_OBJ_BIAS)));
291 }
292 goto retry;
293 }
294 return(p);
295 }
296 # endif
297 fail:
298 (*GC_is_visible_print_proc)((ptr_t)p);
299 return(p);
300 }
301
302
GC_pre_incr(p,how_much)303 GC_PTR GC_pre_incr (p, how_much)
304 GC_PTR *p;
305 size_t how_much;
306 {
307 GC_PTR initial = *p;
308 GC_PTR result = GC_same_obj((GC_PTR)((word)initial + how_much), initial);
309
310 if (!GC_all_interior_pointers) {
311 (void) GC_is_valid_displacement(result);
312 }
313 return (*p = result);
314 }
315
GC_post_incr(p,how_much)316 GC_PTR GC_post_incr (p, how_much)
317 GC_PTR *p;
318 size_t how_much;
319 {
320 GC_PTR initial = *p;
321 GC_PTR result = GC_same_obj((GC_PTR)((word)initial + how_much), initial);
322
323 if (!GC_all_interior_pointers) {
324 (void) GC_is_valid_displacement(result);
325 }
326 *p = result;
327 return(initial);
328 }
329