ptr_chck.c

/*
 * 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);
}

GC_same_obj_print_proc_t GC_same_obj_print_proc
    = GC_default_same_obj_print_proc;

GC_API void *GC_CALL
GC_same_obj(void *p, void *q)
{
  hdr *hhdr;
  ptr_t base, limit;
  size_t sz;

  if (!EXPECT(GC_is_initialized, TRUE))
    GC_init();
  hhdr = HDR(p);
  if (NULL == hhdr) {
    if (divHBLKSZ(ADDR(p)) != divHBLKSZ(ADDR(q)) && HDR(q) != NULL) {
      GC_same_obj_print_proc((ptr_t)p, (ptr_t)q);
    }
    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)) {
    struct hblk *h = GC_find_starting_hblk(HBLKPTR(p), &hhdr);

    limit = (ptr_t)h + hhdr->hb_sz;
    if (ADDR_GE((ptr_t)p, limit) || ADDR_GE((ptr_t)q, limit)
        || ADDR_LT((ptr_t)q, (ptr_t)h)) {
      GC_same_obj_print_proc((ptr_t)p, (ptr_t)q);
    }
    return p;
  }
  sz = hhdr->hb_sz;
  if (sz > MAXOBJBYTES) {
    base = (ptr_t)HBLKPTR(p);
    limit = base + sz;
    if (ADDR_GE((ptr_t)p, limit)) {
      GC_same_obj_print_proc((ptr_t)p, (ptr_t)q);
      return p;
    }
  } else {
    size_t offset;

    if (HBLKPTR(p) != HBLKPTR(q)) {
      /* Without this check, we might miss an error if q points to    */
      /* the first object on a page, and points just before the page. */
      GC_same_obj_print_proc((ptr_t)p, (ptr_t)q);
      return p;
    }
    offset = HBLKDISPL(p) % sz;
    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 (!ADDR_INSIDE((ptr_t)q, base, limit)) {
    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);
}

GC_valid_ptr_print_proc_t GC_is_valid_displacement_print_proc
    = GC_default_is_valid_displacement_print_proc;

GC_API void *GC_CALL
GC_is_valid_displacement(void *p)
{
  hdr *hhdr;
  size_t offset;
  struct hblk *h;
  size_t sz;

  if (!EXPECT(GC_is_initialized, TRUE))
    GC_init();
  if (NULL == p)
    return NULL;
  hhdr = HDR(p);
  if (NULL == hhdr)
    return p;
  h = HBLKPTR(p);
  if (GC_all_interior_pointers) {
    h = GC_find_starting_hblk(h, &hhdr);
  } else if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
    GC_is_valid_displacement_print_proc((ptr_t)p);
    return p;
  }
  sz = hhdr->hb_sz;
  offset = HBLKDISPL(p) % sz;
  if ((sz > MAXOBJBYTES && ADDR_GE((ptr_t)p, (ptr_t)h + sz))
      || !GC_valid_offsets[offset]
      || (ADDR_LT((ptr_t)(h + 1), (ptr_t)p + sz - offset)
          && !IS_FORWARDING_ADDR_OR_NIL(HDR(h + 1)))) {
    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);
}

GC_valid_ptr_print_proc_t GC_is_visible_print_proc
    = GC_default_is_visible_print_proc;

#ifndef THREADS
/* Could p be a stack address?        */
STATIC GC_bool
GC_on_stack(ptr_t p)
{
  return HOTTER_THAN(p, GC_stackbottom) && !HOTTER_THAN(p, GC_approx_sp());
}
#endif /* !THREADS */

GC_API void *GC_CALL
GC_is_visible(void *p)
{
  const hdr *hhdr;

  if ((ADDR(p) & (ALIGNMENT - 1)) != 0)
    goto fail;
  if (!EXPECT(GC_is_initialized, TRUE))
    GC_init();
#ifdef THREADS
  hhdr = HDR(p);
  if (hhdr != NULL && NULL == GC_base(p)) {
    goto fail;
  } else {
    /* May be inside thread stack.  We can't do much. */
    return p;
  }
#else
  /* Check stack first: */
  if (GC_on_stack((ptr_t)p))
    return p;

  hhdr = HDR(p);
  if (NULL == hhdr) {
    if (GC_is_static_root((ptr_t)p))
      return p;
      /* Else do it again correctly:      */
#  if defined(ANY_MSWIN) || defined(DYNAMIC_LOADING)
    if (!GC_no_dls) {
      GC_register_dynamic_libraries();
      if (GC_is_static_root((ptr_t)p))
        return p;
    }
#  endif
    goto fail;
  } else {
    /* p points to the heap. */
    word descr;
    /* TODO: should GC_base be manually inlined? */
    ptr_t base = (ptr_t)GC_base(p);

    if (NULL == base)
      goto fail;
    if (HBLKPTR(base) != HBLKPTR(p))
      hhdr = HDR(base);
    descr = hhdr->hb_descr;
  retry:
    switch (descr & GC_DS_TAGS) {
    case GC_DS_LENGTH:
      if ((word)((ptr_t)p - base) >= descr)
        goto fail;
      break;
    case GC_DS_BITMAP:
      if ((ptr_t)p - base >= (ptrdiff_t)PTRS_TO_BYTES(BITMAP_BITS)
          || (ADDR(p) & (sizeof(ptr_t) - 1)) != 0)
        goto fail;
      if (!(((word)1 << (CPP_WORDSZ - 1 - (word)((ptr_t)p - base))) & 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 (!(descr & SIGNB)) {
        descr = *(word *)((ptr_t)base + (descr & ~(word)GC_DS_TAGS));
      } else {
        ptr_t type_descr = *(ptr_t *)base;

        if (EXPECT(NULL == type_descr, FALSE)) {
          /* See the comment in GC_mark_from.     */
          goto fail;
        }
        descr = *(word *)(type_descr
                          - ((GC_signed_word)descr
                             + (GC_INDIR_PER_OBJ_BIAS - GC_DS_PER_OBJECT)));
      }
      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((ptr_t)initial + how_much, initial);

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

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

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

GC_API void GC_CALL
GC_set_same_obj_print_proc(GC_same_obj_print_proc_t fn)
{
  GC_ASSERT(NONNULL_ARG_NOT_NULL(fn));
  GC_same_obj_print_proc = fn;
}

GC_API GC_same_obj_print_proc_t GC_CALL
GC_get_same_obj_print_proc(void)
{
  return GC_same_obj_print_proc;
}

GC_API void GC_CALL
GC_set_is_valid_displacement_print_proc(GC_valid_ptr_print_proc_t fn)
{
  GC_ASSERT(NONNULL_ARG_NOT_NULL(fn));
  GC_is_valid_displacement_print_proc = fn;
}

GC_API GC_valid_ptr_print_proc_t GC_CALL
GC_get_is_valid_displacement_print_proc(void)
{
  return GC_is_valid_displacement_print_proc;
}

GC_API void GC_CALL
GC_set_is_visible_print_proc(GC_valid_ptr_print_proc_t fn)
{
  GC_ASSERT(NONNULL_ARG_NOT_NULL(fn));
  GC_is_visible_print_proc = fn;
}

GC_API GC_valid_ptr_print_proc_t GC_CALL
GC_get_is_visible_print_proc(void)
{
  return GC_is_visible_print_proc;
}