File: ptr_chck.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 (278 lines) | stat: -rw-r--r-- 9,590 bytes parent folder | download | duplicates (3)
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
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
/*
 * Copyright (c) 1991-1994 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_pmark.h"

/*
 * These are checking routines calls to which could be inserted by a
 * preprocessor to validate C pointer arithmetic.
 */

STATIC void GC_CALLBACK GC_default_same_obj_print_proc(void * p, void * q)
{
    ABORT_ARG2("GC_same_obj test failed",
               ": %p and %p are not in the same object", p, q);
}

void (GC_CALLBACK *GC_same_obj_print_proc) (void *, void *)
                = GC_default_same_obj_print_proc;

/* Check that p and q point to the same object.  Call           */
/* *GC_same_obj_print_proc if they don't.                       */
/* Returns the first argument.  (Return value may be hard       */
/* to use due to typing issues.  But if we had a suitable       */
/* preprocessor...)                                             */
/* Succeeds if neither p nor q points to the heap.              */
/* We assume this is performance critical.  (It shouldn't       */
/* be called by production code, but this can easily make       */
/* debugging intolerably slow.)                                 */
GC_API void * GC_CALL GC_same_obj(void *p, void *q)
{
    struct hblk *h;
    hdr *hhdr;
    ptr_t base, limit;
    word sz;

    if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
    hhdr = HDR((word)p);
    if (hhdr == 0) {
        if (divHBLKSZ((word)p) != divHBLKSZ((word)q)
            && HDR((word)q) != 0) {
            goto fail;
        }
        return(p);
    }
    /* If it's a pointer to the middle of a large object, move it       */
    /* to the beginning.                                                */
    if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
        h = HBLKPTR(p) - (word)hhdr;
        hhdr = HDR(h);
        while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
           h = FORWARDED_ADDR(h, hhdr);
           hhdr = HDR(h);
        }
        limit = (ptr_t)h + hhdr -> hb_sz;
        if ((word)p >= (word)limit || (word)q >= (word)limit
            || (word)q < (word)h) {
            goto fail;
        }
        return(p);
    }
    sz = hhdr -> hb_sz;
    if (sz > MAXOBJBYTES) {
      base = (ptr_t)HBLKPTR(p);
      limit = base + sz;
      if ((word)p >= (word)limit) {
        goto fail;
      }
    } else {
      size_t offset;
      size_t pdispl = HBLKDISPL(p);

      offset = pdispl % sz;
      if (HBLKPTR(p) != HBLKPTR(q)) goto fail;
                /* W/o this check, we might miss an error if    */
                /* q points to the first object on a page, and  */
                /* points just before the page.                 */
      base = (ptr_t)p - offset;
      limit = base + sz;
    }
    /* [base, limit) delimits the object containing p, if any.  */
    /* If p is not inside a valid object, then either q is      */
    /* also outside any valid object, or it is outside          */
    /* [base, limit).                                           */
    if ((word)q >= (word)limit || (word)q < (word)base) {
        goto fail;
    }
    return(p);
fail:
    (*GC_same_obj_print_proc)((ptr_t)p, (ptr_t)q);
    return(p);
}

STATIC void GC_CALLBACK GC_default_is_valid_displacement_print_proc (void *p)
{
    ABORT_ARG1("GC_is_valid_displacement test failed", ": %p not valid", p);
}

void (GC_CALLBACK *GC_is_valid_displacement_print_proc)(void *) =
        GC_default_is_valid_displacement_print_proc;

/* Check that if p is a pointer to a heap page, then it points to       */
/* a valid displacement within a heap object.                           */
/* Uninteresting with GC_all_interior_pointers.                         */
/* Always returns its argument.                                         */
/* Note that we don't lock, since nothing relevant about the header     */
/* should change while we have a valid object pointer to the block.     */
GC_API void * GC_CALL GC_is_valid_displacement(void *p)
{
    hdr *hhdr;
    word pdispl;
    word offset;
    struct hblk *h;
    word sz;

    if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
    hhdr = HDR((word)p);
    if (hhdr == 0) return(p);
    h = HBLKPTR(p);
    if (GC_all_interior_pointers) {
        while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
           h = FORWARDED_ADDR(h, hhdr);
           hhdr = HDR(h);
        }
    }
    if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
        goto fail;
    }
    sz = hhdr -> hb_sz;
    pdispl = HBLKDISPL(p);
    offset = pdispl % sz;
    if ((sz > MAXOBJBYTES && (word)p >= (word)h + sz)
        || !GC_valid_offsets[offset]
        || (word)p - offset + sz > (word)(h + 1)) {
        goto fail;
    }
    return(p);
fail:
    (*GC_is_valid_displacement_print_proc)((ptr_t)p);
    return(p);
}

STATIC void GC_CALLBACK GC_default_is_visible_print_proc(void * p)
{
    ABORT_ARG1("GC_is_visible test failed", ": %p not GC-visible", p);
}

void (GC_CALLBACK *GC_is_visible_print_proc)(void * p) =
                GC_default_is_visible_print_proc;

#ifndef THREADS
/* Could p be a stack address? */
   STATIC GC_bool GC_on_stack(ptr_t p)
   {
#    ifdef STACK_GROWS_DOWN
       if ((word)p >= (word)GC_approx_sp()
           && (word)p < (word)GC_stackbottom) {
         return(TRUE);
       }
#    else
       if ((word)p <= (word)GC_approx_sp()
           && (word)p > (word)GC_stackbottom) {
         return(TRUE);
       }
#    endif
     return(FALSE);
   }
#endif

/* Check that p is visible                                              */
/* to the collector as a possibly pointer containing location.          */
/* If it isn't, invoke *GC_is_visible_print_proc.                       */
/* Returns the argument in all cases.  May erroneously succeed          */
/* in hard cases.  (This is intended for debugging use with             */
/* untyped allocations.  The idea is that it should be possible, though */
/* slow, to add such a call to all indirect pointer stores.)            */
/* Currently useless for the multi-threaded worlds.                     */
GC_API void * GC_CALL GC_is_visible(void *p)
{
    hdr *hhdr;

    if ((word)p & (ALIGNMENT - 1)) goto fail;
    if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
#   ifdef THREADS
        hhdr = HDR((word)p);
        if (hhdr != 0 && GC_base(p) == 0) {
            goto fail;
        } else {
            /* May be inside thread stack.  We can't do much. */
            return(p);
        }
#   else
        /* Check stack first: */
          if (GC_on_stack(p)) return(p);
        hhdr = HDR((word)p);
        if (hhdr == 0) {
            if (GC_is_static_root(p)) return(p);
            /* Else do it again correctly:      */
#           if defined(DYNAMIC_LOADING) || defined(MSWIN32) \
                || defined(MSWINCE) || defined(CYGWIN32) || defined(PCR)
              GC_register_dynamic_libraries();
              if (GC_is_static_root(p))
                return(p);
#           endif
            goto fail;
        } else {
            /* p points to the heap. */
            word descr;
            ptr_t base = GC_base(p);    /* Should be manually inlined? */

            if (base == 0) goto fail;
            if (HBLKPTR(base) != HBLKPTR(p)) hhdr = HDR((word)p);
            descr = hhdr -> hb_descr;
    retry:
            switch(descr & GC_DS_TAGS) {
                case GC_DS_LENGTH:
                    if ((word)p - (word)base > descr) goto fail;
                    break;
                case GC_DS_BITMAP:
                    if ((word)p - (word)base >= WORDS_TO_BYTES(BITMAP_BITS)
                        || ((word)p & (sizeof(word) - 1))) goto fail;
                    if (!(((word)1 << (WORDSZ - ((ptr_t)p - (ptr_t)base) - 1))
                          & descr)) goto fail;
                    break;
                case GC_DS_PROC:
                    /* We could try to decipher this partially.         */
                    /* For now we just punt.                            */
                    break;
                case GC_DS_PER_OBJECT:
                    if ((signed_word)descr >= 0) {
                      descr = *(word *)((ptr_t)base + (descr & ~GC_DS_TAGS));
                    } else {
                      ptr_t type_descr = *(ptr_t *)base;
                      descr = *(word *)(type_descr
                                        - (descr - (word)(GC_DS_PER_OBJECT
                                           - GC_INDIR_PER_OBJ_BIAS)));
                    }
                    goto retry;
            }
            return(p);
        }
#   endif
fail:
    (*GC_is_visible_print_proc)((ptr_t)p);
    return(p);
}

GC_API void * GC_CALL GC_pre_incr (void **p, ptrdiff_t how_much)
{
    void * initial = *p;
    void * result = GC_same_obj((void *)((ptr_t)initial + how_much), initial);

    if (!GC_all_interior_pointers) {
        (void) GC_is_valid_displacement(result);
    }
    return (*p = result);
}

GC_API void * GC_CALL GC_post_incr (void **p, ptrdiff_t how_much)
{
    void * initial = *p;
    void * result = GC_same_obj((void *)((ptr_t)initial + how_much), initial);

    if (!GC_all_interior_pointers) {
        (void) GC_is_valid_displacement(result);
    }
    *p = result;
    return(initial);
}