dbg_mlc.c

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/* 
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991-1995 by Xerox Corporation.  All rights reserved.
 * Copyright (c) 1997 by Silicon Graphics.  All rights reserved.
 * Copyright (c) 1999-2004 Hewlett-Packard Development Company, L.P.
 * Copyright (C) 2007 Free Software Foundation, Inc
 *
 * 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 <errno.h>
#include <string.h>
#include "private/dbg_mlc.h"

void GC_default_print_heap_obj_proc();
GC_API void GC_register_finalizer_no_order
    	(void * obj, GC_finalization_proc fn, void * cd,
	 GC_finalization_proc *ofn, void * *ocd);


#ifndef SHORT_DBG_HDRS
/* Check whether object with base pointer p has debugging info	*/ 
/* p is assumed to point to a legitimate object in our part	*/
/* of the heap.							*/
/* This excludes the check as to whether the back pointer is 	*/
/* odd, which is added by the GC_HAS_DEBUG_INFO macro.		*/
/* Note that if DBG_HDRS_ALL is set, uncollectable objects	*/
/* on free lists may not have debug information set.  Thus it's	*/
/* not always safe to return TRUE, even if the client does	*/
/* its part.							*/
GC_bool GC_has_other_debug_info(ptr_t p)
{
    register oh * ohdr = (oh *)p;
    register ptr_t body = (ptr_t)(ohdr + 1);
    register word sz = GC_size((ptr_t) ohdr);
    
    if (HBLKPTR((ptr_t)ohdr) != HBLKPTR((ptr_t)body)
        || sz < DEBUG_BYTES + EXTRA_BYTES) {
        return(FALSE);
    }
    if (ohdr -> oh_sz == sz) {
    	/* Object may have had debug info, but has been deallocated	*/
    	return(FALSE);
    }
    if (ohdr -> oh_sf == (START_FLAG ^ (word)body)) return(TRUE);
    if (((word *)ohdr)[BYTES_TO_WORDS(sz)-1] == (END_FLAG ^ (word)body)) {
        return(TRUE);
    }
    return(FALSE);
}
#endif

#ifdef KEEP_BACK_PTRS

# include <stdlib.h>

# if defined(LINUX) || defined(SOLARIS) \
     || defined(HPUX) || defined(IRIX5) || defined(OSF1)
#   define RANDOM() random()
# else
#   define RANDOM() (long)rand()
# endif

  /* Store back pointer to source in dest, if that appears to be possible. */
  /* This is not completely safe, since we may mistakenly conclude that	   */
  /* dest has a debugging wrapper.  But the error probability is very	   */
  /* small, and this shouldn't be used in production code.		   */
  /* We assume that dest is the real base pointer.  Source will usually    */
  /* be a pointer to the interior of an object.				   */
  void GC_store_back_pointer(ptr_t source, ptr_t dest)
  {
    if (GC_HAS_DEBUG_INFO(dest)) {
      ((oh *)dest) -> oh_back_ptr = HIDE_BACK_PTR(source);
    }
  }

  void GC_marked_for_finalization(ptr_t dest) {
    GC_store_back_pointer(MARKED_FOR_FINALIZATION, dest);
  }

  /* Store information about the object referencing dest in *base_p	*/
  /* and *offset_p.							*/
  /*   source is root ==> *base_p = address, *offset_p = 0		*/
  /*   source is heap object ==> *base_p != 0, *offset_p = offset 	*/
  /*   Returns 1 on success, 0 if source couldn't be determined.	*/
  /* Dest can be any address within a heap object.			*/
  GC_ref_kind GC_get_back_ptr_info(void *dest, void **base_p, size_t *offset_p)
  {
    oh * hdr = (oh *)GC_base(dest);
    ptr_t bp;
    ptr_t bp_base;
    if (!GC_HAS_DEBUG_INFO((ptr_t) hdr)) return GC_NO_SPACE;
    bp = REVEAL_POINTER(hdr -> oh_back_ptr);
    if (MARKED_FOR_FINALIZATION == bp) return GC_FINALIZER_REFD;
    if (MARKED_FROM_REGISTER == bp) return GC_REFD_FROM_REG;
    if (NOT_MARKED == bp) return GC_UNREFERENCED;
#   if ALIGNMENT == 1
      /* Heuristically try to fix off by 1 errors we introduced by 	*/
      /* insisting on even addresses.					*/
      {
	ptr_t alternate_ptr = bp + 1;
	ptr_t target = *(ptr_t *)bp;
	ptr_t alternate_target = *(ptr_t *)alternate_ptr;

	if (alternate_target >= GC_least_plausible_heap_addr
	    && alternate_target <= GC_greatest_plausible_heap_addr
	    && (target < GC_least_plausible_heap_addr
		|| target > GC_greatest_plausible_heap_addr)) {
	    bp = alternate_ptr;
	}
      }
#   endif
    bp_base = GC_base(bp);
    if (0 == bp_base) {
      *base_p = bp;
      *offset_p = 0;
      return GC_REFD_FROM_ROOT;
    } else {
      if (GC_HAS_DEBUG_INFO(bp_base)) bp_base += sizeof(oh);
      *base_p = bp_base;
      *offset_p = bp - bp_base;
      return GC_REFD_FROM_HEAP;
    }
  }

  /* Generate a random heap address.		*/
  /* The resulting address is in the heap, but	*/
  /* not necessarily inside a valid object.	*/
  void *GC_generate_random_heap_address(void)
  {
    int i;
    long heap_offset = RANDOM();
    if (GC_heapsize > RAND_MAX) {
	heap_offset *= RAND_MAX;
	heap_offset += RANDOM();
    }
    heap_offset %= GC_heapsize;
    	/* This doesn't yield a uniform distribution, especially if	*/
        /* e.g. RAND_MAX = 1.5* GC_heapsize.  But for typical cases,	*/
        /* it's not too bad.						*/
    for (i = 0; i < GC_n_heap_sects; ++ i) {
	size_t size = GC_heap_sects[i].hs_bytes;
	if (heap_offset < size) {
	    return GC_heap_sects[i].hs_start + heap_offset;
	} else {
	    heap_offset -= size;
	}
    }
    ABORT("GC_generate_random_heap_address: size inconsistency");
    /*NOTREACHED*/
    return 0;
  }

  /* Generate a random address inside a valid marked heap object. */
  void *GC_generate_random_valid_address(void)
  {
    ptr_t result;
    ptr_t base;
    for (;;) {
	result = GC_generate_random_heap_address();
  	base = GC_base(result);
	if (0 == base) continue;
	if (!GC_is_marked(base)) continue;
	return result;
    }
  }

  /* Print back trace for p */
  void GC_print_backtrace(void *p)
  {
    void *current = p;
    int i;
    GC_ref_kind source;
    size_t offset;
    void *base;

    GC_print_heap_obj(GC_base(current));
    GC_err_printf("\n");
    for (i = 0; ; ++i) {
      source = GC_get_back_ptr_info(current, &base, &offset);
      if (GC_UNREFERENCED == source) {
	GC_err_printf("Reference could not be found\n");
  	goto out;
      }
      if (GC_NO_SPACE == source) {
	GC_err_printf("No debug info in object: Can't find reference\n");
	goto out;
      }
      GC_err_printf("Reachable via %d levels of pointers from ",
		 (unsigned long)i);
      switch(source) {
	case GC_REFD_FROM_ROOT:
	  GC_err_printf("root at %p\n\n", base);
	  goto out;
	case GC_REFD_FROM_REG:
	  GC_err_printf("root in register\n\n");
	  goto out;
	case GC_FINALIZER_REFD:
	  GC_err_printf("list of finalizable objects\n\n");
	  goto out;
	case GC_REFD_FROM_HEAP:
	  GC_err_printf("offset %ld in object:\n", (unsigned long)offset);
	  /* Take GC_base(base) to get real base, i.e. header. */
	  GC_print_heap_obj(GC_base(base));
	  GC_err_printf("\n");
	  break;
      }
      current = base;
    }
    out:;
  }

  /* Force a garbage collection and generate a backtrace from a	*/
  /* random heap address.					*/
  void GC_generate_random_backtrace_no_gc(void)
  {
    void * current;
    current = GC_generate_random_valid_address();
    GC_printf("\n****Chose address %p in object\n", current);
    GC_print_backtrace(current);
  }
    
  void GC_generate_random_backtrace(void)
  {
    GC_gcollect();
    GC_generate_random_backtrace_no_gc();
  }
    
#endif /* KEEP_BACK_PTRS */

# define CROSSES_HBLK(p, sz) \
	(((word)(p + sizeof(oh) + sz - 1) ^ (word)p) >= HBLKSIZE)
/* Store debugging info into p.  Return displaced pointer. */
/* Assumes we don't hold allocation lock.		   */
ptr_t GC_store_debug_info(ptr_t p, word sz, const char *string, word integer)
{
    register word * result = (word *)((oh *)p + 1);
    DCL_LOCK_STATE;
    
    /* There is some argument that we should dissble signals here.	*/
    /* But that's expensive.  And this way things should only appear	*/
    /* inconsistent while we're in the handler.				*/
    LOCK();
    GC_ASSERT(GC_size(p) >= sizeof(oh) + sz);
    GC_ASSERT(!(SMALL_OBJ(sz) && CROSSES_HBLK(p, sz)));
#   ifdef KEEP_BACK_PTRS
      ((oh *)p) -> oh_back_ptr = HIDE_BACK_PTR(NOT_MARKED);
#   endif
#   ifdef MAKE_BACK_GRAPH
      ((oh *)p) -> oh_bg_ptr = HIDE_BACK_PTR((ptr_t)0);
#   endif
    ((oh *)p) -> oh_string = string;
    ((oh *)p) -> oh_int = integer;
#   ifndef SHORT_DBG_HDRS
      ((oh *)p) -> oh_sz = sz;
      ((oh *)p) -> oh_sf = START_FLAG ^ (word)result;
      ((word *)p)[BYTES_TO_WORDS(GC_size(p))-1] =
         result[SIMPLE_ROUNDED_UP_WORDS(sz)] = END_FLAG ^ (word)result;
#   endif
    UNLOCK();
    return((ptr_t)result);
}

#ifdef DBG_HDRS_ALL
/* Store debugging info into p.  Return displaced pointer.	   */
/* This version assumes we do hold the allocation lock.		   */
ptr_t GC_store_debug_info_inner(ptr_t p, word sz, char *string, word integer)
{
    register word * result = (word *)((oh *)p + 1);
    
    /* There is some argument that we should disable signals here.	*/
    /* But that's expensive.  And this way things should only appear	*/
    /* inconsistent while we're in the handler.				*/
    GC_ASSERT(GC_size(p) >= sizeof(oh) + sz);
    GC_ASSERT(!(SMALL_OBJ(sz) && CROSSES_HBLK(p, sz)));
#   ifdef KEEP_BACK_PTRS
      ((oh *)p) -> oh_back_ptr = HIDE_BACK_PTR(NOT_MARKED);
#   endif
#   ifdef MAKE_BACK_GRAPH
      ((oh *)p) -> oh_bg_ptr = HIDE_BACK_PTR((ptr_t)0);
#   endif
    ((oh *)p) -> oh_string = string;
    ((oh *)p) -> oh_int = integer;
#   ifndef SHORT_DBG_HDRS
      ((oh *)p) -> oh_sz = sz;
      ((oh *)p) -> oh_sf = START_FLAG ^ (word)result;
      ((word *)p)[BYTES_TO_WORDS(GC_size(p))-1] =
         result[SIMPLE_ROUNDED_UP_WORDS(sz)] = END_FLAG ^ (word)result;
#   endif
    return((ptr_t)result);
}
#endif

#ifndef SHORT_DBG_HDRS
/* Check the object with debugging info at ohdr		*/
/* return NIL if it's OK.  Else return clobbered	*/
/* address.						*/
ptr_t GC_check_annotated_obj(oh *ohdr)
{
    register ptr_t body = (ptr_t)(ohdr + 1);
    register word gc_sz = GC_size((ptr_t)ohdr);
    if (ohdr -> oh_sz + DEBUG_BYTES > gc_sz) {
        return((ptr_t)(&(ohdr -> oh_sz)));
    }
    if (ohdr -> oh_sf != (START_FLAG ^ (word)body)) {
        return((ptr_t)(&(ohdr -> oh_sf)));
    }
    if (((word *)ohdr)[BYTES_TO_WORDS(gc_sz)-1] != (END_FLAG ^ (word)body)) {
        return((ptr_t)((word *)ohdr + BYTES_TO_WORDS(gc_sz)-1));
    }
    if (((word *)body)[SIMPLE_ROUNDED_UP_WORDS(ohdr -> oh_sz)]
        != (END_FLAG ^ (word)body)) {
        return((ptr_t)((word *)body + SIMPLE_ROUNDED_UP_WORDS(ohdr -> oh_sz)));
    }
    return(0);
}
#endif /* !SHORT_DBG_HDRS */

static GC_describe_type_fn GC_describe_type_fns[MAXOBJKINDS] = {0};

void GC_register_describe_type_fn(int kind, GC_describe_type_fn fn)
{
  GC_describe_type_fns[kind] = fn;
}

/* Print a type description for the object whose client-visible address	*/
/* is p.								*/
void GC_print_type(ptr_t p)
{
    hdr * hhdr = GC_find_header(p);
    char buffer[GC_TYPE_DESCR_LEN + 1];
    int kind = hhdr -> hb_obj_kind;

    if (0 != GC_describe_type_fns[kind] && GC_is_marked(GC_base(p))) {
	/* This should preclude free list objects except with	*/
	/* thread-local allocation.				*/
	buffer[GC_TYPE_DESCR_LEN] = 0;
	(GC_describe_type_fns[kind])(p, buffer);
	GC_ASSERT(buffer[GC_TYPE_DESCR_LEN] == 0);
	GC_err_puts(buffer);
    } else {
	switch(kind) {
	  case PTRFREE:
	    GC_err_puts("PTRFREE");
	    break;