Line data Source code
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 : #include "private/gc_pmark.h"
15 :
16 : /*
17 : * These are checking routines calls to which could be inserted by a
18 : * preprocessor to validate C pointer arithmetic.
19 : */
20 :
21 0 : STATIC void GC_CALLBACK GC_default_same_obj_print_proc(void * p, void * q)
22 : {
23 0 : GC_err_printf("%p and %p are not in the same object\n", p, q);
24 0 : ABORT("GC_same_obj test failed");
25 0 : }
26 :
27 : void (GC_CALLBACK *GC_same_obj_print_proc) (void *, void *)
28 : = GC_default_same_obj_print_proc;
29 :
30 : /* Check that p and q point to the same object. Call */
31 : /* *GC_same_obj_print_proc if they don't. */
32 : /* Returns the first argument. (Return value may be hard */
33 : /* to use,due to typing issues. But if we had a suitable */
34 : /* preprocessor ...) */
35 : /* Succeeds if neither p nor q points to the heap. */
36 : /* We assume this is performance critical. (It shouldn't */
37 : /* be called by production code, but this can easily make */
38 : /* debugging intolerably slow.) */
39 0 : GC_API void * GC_CALL GC_same_obj(void *p, void *q)
40 : {
41 : struct hblk *h;
42 : hdr *hhdr;
43 : ptr_t base, limit;
44 : word sz;
45 :
46 0 : if (!GC_is_initialized) GC_init();
47 0 : hhdr = HDR((word)p);
48 0 : if (hhdr == 0) {
49 0 : if (divHBLKSZ((word)p) != divHBLKSZ((word)q)
50 0 : && HDR((word)q) != 0) {
51 0 : goto fail;
52 : }
53 0 : return(p);
54 : }
55 : /* If it's a pointer to the middle of a large object, move it */
56 : /* to the beginning. */
57 0 : if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
58 0 : h = HBLKPTR(p) - (word)hhdr;
59 0 : hhdr = HDR(h);
60 0 : while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
61 0 : h = FORWARDED_ADDR(h, hhdr);
62 0 : hhdr = HDR(h);
63 : }
64 0 : limit = (ptr_t)h + hhdr -> hb_sz;
65 0 : if ((ptr_t)p >= limit || (ptr_t)q >= limit || (ptr_t)q < (ptr_t)h ) {
66 : goto fail;
67 : }
68 0 : return(p);
69 : }
70 0 : sz = hhdr -> hb_sz;
71 0 : if (sz > MAXOBJBYTES) {
72 0 : base = (ptr_t)HBLKPTR(p);
73 0 : limit = base + sz;
74 0 : if ((ptr_t)p >= limit) {
75 0 : goto fail;
76 : }
77 : } else {
78 : size_t offset;
79 0 : size_t pdispl = HBLKDISPL(p);
80 :
81 0 : offset = pdispl % sz;
82 0 : if (HBLKPTR(p) != HBLKPTR(q)) goto fail;
83 : /* W/o this check, we might miss an error if */
84 : /* q points to the first object on a page, and */
85 : /* points just before the page. */
86 0 : base = (ptr_t)p - offset;
87 0 : limit = base + sz;
88 : }
89 : /* [base, limit) delimits the object containing p, if any. */
90 : /* If p is not inside a valid object, then either q is */
91 : /* also outside any valid object, or it is outside */
92 : /* [base, limit). */
93 0 : if ((ptr_t)q >= limit || (ptr_t)q < base) {
94 : goto fail;
95 : }
96 0 : return(p);
97 : fail:
98 0 : (*GC_same_obj_print_proc)((ptr_t)p, (ptr_t)q);
99 0 : return(p);
100 : }
101 :
102 0 : STATIC void GC_CALLBACK GC_default_is_valid_displacement_print_proc (void *p)
103 : {
104 0 : GC_err_printf("%p does not point to valid object displacement\n", p);
105 0 : ABORT("GC_is_valid_displacement test failed");
106 0 : }
107 :
108 : void (GC_CALLBACK *GC_is_valid_displacement_print_proc)(void *) =
109 : GC_default_is_valid_displacement_print_proc;
110 :
111 : /* Check that if p is a pointer to a heap page, then it points to */
112 : /* a valid displacement within a heap object. */
113 : /* Uninteresting with GC_all_interior_pointers. */
114 : /* Always returns its argument. */
115 : /* Note that we don't lock, since nothing relevant about the header */
116 : /* should change while we have a valid object pointer to the block. */
117 0 : GC_API void * GC_CALL GC_is_valid_displacement(void *p)
118 : {
119 : hdr *hhdr;
120 : word pdispl;
121 : word offset;
122 : struct hblk *h;
123 : word sz;
124 :
125 0 : if (!GC_is_initialized) GC_init();
126 0 : hhdr = HDR((word)p);
127 0 : if (hhdr == 0) return(p);
128 0 : h = HBLKPTR(p);
129 0 : if (GC_all_interior_pointers) {
130 0 : while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
131 0 : h = FORWARDED_ADDR(h, hhdr);
132 0 : hhdr = HDR(h);
133 : }
134 : }
135 0 : if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
136 0 : goto fail;
137 : }
138 0 : sz = hhdr -> hb_sz;
139 0 : pdispl = HBLKDISPL(p);
140 0 : offset = pdispl % sz;
141 0 : if ((sz > MAXOBJBYTES && (ptr_t)p >= (ptr_t)h + sz)
142 0 : || !GC_valid_offsets[offset]
143 0 : || (ptr_t)p - offset + sz > (ptr_t)(h + 1)) {
144 : goto fail;
145 : }
146 0 : return(p);
147 : fail:
148 0 : (*GC_is_valid_displacement_print_proc)((ptr_t)p);
149 0 : return(p);
150 : }
151 :
152 0 : STATIC void GC_CALLBACK GC_default_is_visible_print_proc(void * p)
153 : {
154 0 : GC_err_printf("%p is not a GC visible pointer location\n", p);
155 0 : ABORT("GC_is_visible test failed");
156 0 : }
157 :
158 : void (GC_CALLBACK *GC_is_visible_print_proc)(void * p) =
159 : GC_default_is_visible_print_proc;
160 :
161 : #ifndef THREADS
162 : /* Could p be a stack address? */
163 : STATIC GC_bool GC_on_stack(ptr_t p)
164 : {
165 : # ifdef STACK_GROWS_DOWN
166 : if ((ptr_t)p >= GC_approx_sp() && (ptr_t)p < GC_stackbottom) {
167 : return(TRUE);
168 : }
169 : # else
170 : if ((ptr_t)p <= GC_approx_sp() && (ptr_t)p > GC_stackbottom) {
171 : return(TRUE);
172 : }
173 : # endif
174 : return(FALSE);
175 : }
176 : #endif
177 :
178 : /* Check that p is visible */
179 : /* to the collector as a possibly pointer containing location. */
180 : /* If it isn't invoke *GC_is_visible_print_proc. */
181 : /* Returns the argument in all cases. May erroneously succeed */
182 : /* in hard cases. (This is intended for debugging use with */
183 : /* untyped allocations. The idea is that it should be possible, though */
184 : /* slow, to add such a call to all indirect pointer stores.) */
185 : /* Currently useless for multithreaded worlds. */
186 0 : GC_API void * GC_CALL GC_is_visible(void *p)
187 : {
188 : hdr *hhdr;
189 :
190 0 : if ((word)p & (ALIGNMENT - 1)) goto fail;
191 0 : if (!GC_is_initialized) GC_init();
192 : # ifdef THREADS
193 0 : hhdr = HDR((word)p);
194 0 : if (hhdr != 0 && GC_base(p) == 0) {
195 : goto fail;
196 : } else {
197 : /* May be inside thread stack. We can't do much. */
198 0 : return(p);
199 : }
200 : # else
201 : /* Check stack first: */
202 : if (GC_on_stack(p)) return(p);
203 : hhdr = HDR((word)p);
204 : if (hhdr == 0) {
205 : if (GC_is_static_root(p)) return(p);
206 : /* Else do it again correctly: */
207 : # if defined(DYNAMIC_LOADING) || defined(MSWIN32) \
208 : || defined(MSWINCE) || defined(CYGWIN32) || defined(PCR)
209 : GC_register_dynamic_libraries();
210 : if (GC_is_static_root(p))
211 : return(p);
212 : # endif
213 : goto fail;
214 : } else {
215 : /* p points to the heap. */
216 : word descr;
217 : ptr_t base = GC_base(p); /* Should be manually inlined? */
218 :
219 : if (base == 0) goto fail;
220 : if (HBLKPTR(base) != HBLKPTR(p)) hhdr = HDR((word)p);
221 : descr = hhdr -> hb_descr;
222 : retry:
223 : switch(descr & GC_DS_TAGS) {
224 : case GC_DS_LENGTH:
225 : if ((word)((ptr_t)p - (ptr_t)base) > (word)descr) goto fail;
226 : break;
227 : case GC_DS_BITMAP:
228 : if ((word)((ptr_t)p - (ptr_t)base)
229 : >= WORDS_TO_BYTES(BITMAP_BITS)
230 : || ((word)p & (sizeof(word) - 1))) goto fail;
231 : if (!(((word)1 << (WORDSZ - ((ptr_t)p - (ptr_t)base) - 1))
232 : & descr)) goto fail;
233 : break;
234 : case GC_DS_PROC:
235 : /* We could try to decipher this partially. */
236 : /* For now we just punt. */
237 : break;
238 : case GC_DS_PER_OBJECT:
239 : if ((signed_word)descr >= 0) {
240 : descr = *(word *)((ptr_t)base + (descr & ~GC_DS_TAGS));
241 : } else {
242 : ptr_t type_descr = *(ptr_t *)base;
243 : descr = *(word *)(type_descr
244 : - (descr - (word)(GC_DS_PER_OBJECT
245 : - GC_INDIR_PER_OBJ_BIAS)));
246 : }
247 : goto retry;
248 : }
249 : return(p);
250 : }
251 : # endif
252 : fail:
253 0 : (*GC_is_visible_print_proc)((ptr_t)p);
254 0 : return(p);
255 : }
256 :
257 0 : GC_API void * GC_CALL GC_pre_incr (void **p, ptrdiff_t how_much)
258 : {
259 0 : void * initial = *p;
260 0 : void * result = GC_same_obj((void *)((ptr_t)initial + how_much), initial);
261 :
262 0 : if (!GC_all_interior_pointers) {
263 0 : (void) GC_is_valid_displacement(result);
264 : }
265 0 : return (*p = result);
266 : }
267 :
268 0 : GC_API void * GC_CALL GC_post_incr (void **p, ptrdiff_t how_much)
269 : {
270 0 : void * initial = *p;
271 0 : void * result = GC_same_obj((void *)((ptr_t)initial + how_much), initial);
272 :
273 0 : if (!GC_all_interior_pointers) {
274 0 : (void) GC_is_valid_displacement(result);
275 : }
276 0 : *p = result;
277 0 : return(initial);
278 : }
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