279 lines
9.4 KiB
C
279 lines
9.4 KiB
C
/*
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* Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
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*
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* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
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* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
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*
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* Permission is hereby granted to use or copy this program
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* for any purpose, provided the above notices are retained on all copies.
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* Permission to modify the code and to distribute modified code is granted,
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* provided the above notices are retained, and a notice that the code was
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* modified is included with the above copyright notice.
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*/
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#include "private/gc_pmark.h"
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/*
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* These are checking routines calls to which could be inserted by a
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* preprocessor to validate C pointer arithmetic.
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*/
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STATIC void GC_CALLBACK GC_default_same_obj_print_proc(void * p, void * q)
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{
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ABORT_ARG2("GC_same_obj test failed",
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": %p and %p are not in the same object", p, q);
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}
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void (GC_CALLBACK *GC_same_obj_print_proc) (void *, void *)
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= GC_default_same_obj_print_proc;
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/* Check that p and q point to the same object. Call */
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/* *GC_same_obj_print_proc if they don't. */
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/* Returns the first argument. (Return value may be hard */
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/* to use due to typing issues. But if we had a suitable */
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/* preprocessor...) */
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/* Succeeds if neither p nor q points to the heap. */
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/* We assume this is performance critical. (It shouldn't */
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/* be called by production code, but this can easily make */
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/* debugging intolerably slow.) */
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GC_API void * GC_CALL GC_same_obj(void *p, void *q)
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{
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struct hblk *h;
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hdr *hhdr;
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ptr_t base, limit;
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word sz;
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if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
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hhdr = HDR((word)p);
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if (hhdr == 0) {
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if (divHBLKSZ((word)p) != divHBLKSZ((word)q)
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&& HDR((word)q) != 0) {
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goto fail;
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}
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return(p);
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}
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/* If it's a pointer to the middle of a large object, move it */
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/* to the beginning. */
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if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
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h = HBLKPTR(p) - (word)hhdr;
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hhdr = HDR(h);
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while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
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h = FORWARDED_ADDR(h, hhdr);
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hhdr = HDR(h);
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}
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limit = (ptr_t)h + hhdr -> hb_sz;
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if ((word)p >= (word)limit || (word)q >= (word)limit
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|| (word)q < (word)h) {
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goto fail;
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}
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return(p);
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}
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sz = hhdr -> hb_sz;
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if (sz > MAXOBJBYTES) {
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base = (ptr_t)HBLKPTR(p);
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limit = base + sz;
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if ((word)p >= (word)limit) {
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goto fail;
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}
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} else {
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size_t offset;
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size_t pdispl = HBLKDISPL(p);
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offset = pdispl % sz;
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if (HBLKPTR(p) != HBLKPTR(q)) goto fail;
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/* W/o this check, we might miss an error if */
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/* q points to the first object on a page, and */
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/* points just before the page. */
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base = (ptr_t)p - offset;
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limit = base + sz;
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}
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/* [base, limit) delimits the object containing p, if any. */
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/* If p is not inside a valid object, then either q is */
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/* also outside any valid object, or it is outside */
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/* [base, limit). */
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if ((word)q >= (word)limit || (word)q < (word)base) {
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goto fail;
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}
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return(p);
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fail:
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(*GC_same_obj_print_proc)((ptr_t)p, (ptr_t)q);
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return(p);
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}
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STATIC void GC_CALLBACK GC_default_is_valid_displacement_print_proc (void *p)
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{
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ABORT_ARG1("GC_is_valid_displacement test failed", ": %p not valid", p);
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}
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void (GC_CALLBACK *GC_is_valid_displacement_print_proc)(void *) =
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GC_default_is_valid_displacement_print_proc;
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/* Check that if p is a pointer to a heap page, then it points to */
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/* a valid displacement within a heap object. */
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/* Uninteresting with GC_all_interior_pointers. */
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/* Always returns its argument. */
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/* Note that we don't lock, since nothing relevant about the header */
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/* should change while we have a valid object pointer to the block. */
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GC_API void * GC_CALL GC_is_valid_displacement(void *p)
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{
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hdr *hhdr;
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word pdispl;
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word offset;
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struct hblk *h;
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word sz;
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if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
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hhdr = HDR((word)p);
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if (hhdr == 0) return(p);
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h = HBLKPTR(p);
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if (GC_all_interior_pointers) {
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while (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
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h = FORWARDED_ADDR(h, hhdr);
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hhdr = HDR(h);
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}
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}
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if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
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goto fail;
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}
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sz = hhdr -> hb_sz;
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pdispl = HBLKDISPL(p);
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offset = pdispl % sz;
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if ((sz > MAXOBJBYTES && (word)p >= (word)h + sz)
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|| !GC_valid_offsets[offset]
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|| (word)p - offset + sz > (word)(h + 1)) {
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goto fail;
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}
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return(p);
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fail:
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(*GC_is_valid_displacement_print_proc)((ptr_t)p);
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return(p);
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}
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STATIC void GC_CALLBACK GC_default_is_visible_print_proc(void * p)
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{
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ABORT_ARG1("GC_is_visible test failed", ": %p not GC-visible", p);
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}
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void (GC_CALLBACK *GC_is_visible_print_proc)(void * p) =
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GC_default_is_visible_print_proc;
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#ifndef THREADS
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/* Could p be a stack address? */
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STATIC GC_bool GC_on_stack(void *p)
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{
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# ifdef STACK_GROWS_DOWN
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if ((word)p >= (word)GC_approx_sp()
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&& (word)p < (word)GC_stackbottom) {
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return(TRUE);
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}
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# else
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if ((word)p <= (word)GC_approx_sp()
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&& (word)p > (word)GC_stackbottom) {
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return(TRUE);
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}
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# endif
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return(FALSE);
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}
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#endif
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/* Check that p is visible */
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/* to the collector as a possibly pointer containing location. */
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/* If it isn't, invoke *GC_is_visible_print_proc. */
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/* Returns the argument in all cases. May erroneously succeed */
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/* in hard cases. (This is intended for debugging use with */
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/* untyped allocations. The idea is that it should be possible, though */
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/* slow, to add such a call to all indirect pointer stores.) */
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/* Currently useless for the multi-threaded worlds. */
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GC_API void * GC_CALL GC_is_visible(void *p)
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{
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hdr *hhdr;
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if ((word)p & (ALIGNMENT - 1)) goto fail;
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if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
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# ifdef THREADS
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hhdr = HDR((word)p);
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if (hhdr != 0 && GC_base(p) == 0) {
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goto fail;
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} else {
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/* May be inside thread stack. We can't do much. */
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return(p);
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}
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# else
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/* Check stack first: */
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if (GC_on_stack(p)) return(p);
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hhdr = HDR((word)p);
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if (hhdr == 0) {
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if (GC_is_static_root(p)) return(p);
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/* Else do it again correctly: */
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# if defined(DYNAMIC_LOADING) || defined(MSWIN32) \
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|| defined(MSWINCE) || defined(CYGWIN32) || defined(PCR)
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GC_register_dynamic_libraries();
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if (GC_is_static_root(p))
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return(p);
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# endif
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goto fail;
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} else {
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/* p points to the heap. */
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word descr;
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ptr_t base = (ptr_t)GC_base(p); /* Should be manually inlined? */
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if (base == 0) goto fail;
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if (HBLKPTR(base) != HBLKPTR(p)) hhdr = HDR((word)p);
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descr = hhdr -> hb_descr;
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retry:
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switch(descr & GC_DS_TAGS) {
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case GC_DS_LENGTH:
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if ((word)p - (word)base > descr) goto fail;
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break;
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case GC_DS_BITMAP:
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if ((word)p - (word)base >= WORDS_TO_BYTES(BITMAP_BITS)
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|| ((word)p & (sizeof(word) - 1))) goto fail;
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if (!(((word)1 << (WORDSZ - ((ptr_t)p - (ptr_t)base) - 1))
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& descr)) goto fail;
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break;
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case GC_DS_PROC:
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/* We could try to decipher this partially. */
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/* For now we just punt. */
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break;
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case GC_DS_PER_OBJECT:
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if ((signed_word)descr >= 0) {
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descr = *(word *)((ptr_t)base + (descr & ~GC_DS_TAGS));
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} else {
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ptr_t type_descr = *(ptr_t *)base;
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descr = *(word *)(type_descr
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- (descr - (word)(GC_DS_PER_OBJECT
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- GC_INDIR_PER_OBJ_BIAS)));
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}
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goto retry;
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}
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return(p);
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}
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# endif
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fail:
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(*GC_is_visible_print_proc)((ptr_t)p);
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return(p);
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}
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GC_API void * GC_CALL GC_pre_incr (void **p, ptrdiff_t how_much)
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{
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void * initial = *p;
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void * result = GC_same_obj((void *)((ptr_t)initial + how_much), initial);
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if (!GC_all_interior_pointers) {
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(void) GC_is_valid_displacement(result);
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}
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return (*p = result);
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}
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GC_API void * GC_CALL GC_post_incr (void **p, ptrdiff_t how_much)
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{
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void * initial = *p;
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void * result = GC_same_obj((void *)((ptr_t)initial + how_much), initial);
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if (!GC_all_interior_pointers) {
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(void) GC_is_valid_displacement(result);
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}
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*p = result;
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return(initial);
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}
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