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mark_rts.c

/* 
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * 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 <stdio.h>
# include "private/gc_priv.h"

/* Data structure for list of root sets.                    */
/* We keep a hash table, so that we can filter out duplicate additions. */
/* Under Win32, we need to do a better job of filtering overlaps, so    */
/* we resort to sequential search, and pay the price.             */
/* This is really declared in gc_priv.h:
struct roots {
      ptr_t r_start;
      ptr_t r_end;
 #    if !defined(MSWIN32) && !defined(MSWINCE)
        struct roots * r_next;
 #    endif
      GC_bool r_tmp;
            -- Delete before registering new dynamic libraries
};

struct roots GC_static_roots[MAX_ROOT_SETS];
*/

int GC_no_dls = 0;      /* Register dynamic library data segments.      */

static int n_root_sets = 0;

      /* GC_static_roots[0..n_root_sets) contains the valid root sets. */

# if !defined(NO_DEBUGGING)
/* For debugging: */
void GC_print_static_roots()
{
    register int i;
    size_t total = 0;
    
    for (i = 0; i < n_root_sets; i++) {
        GC_printf2("From 0x%lx to 0x%lx ",
               (unsigned long) GC_static_roots[i].r_start,
               (unsigned long) GC_static_roots[i].r_end);
        if (GC_static_roots[i].r_tmp) {
            GC_printf0(" (temporary)\n");
        } else {
            GC_printf0("\n");
        }
        total += GC_static_roots[i].r_end - GC_static_roots[i].r_start;
    }
    GC_printf1("Total size: %ld\n", (unsigned long) total);
    if (GC_root_size != total) {
      GC_printf1("GC_root_size incorrect: %ld!!\n",
               (unsigned long) GC_root_size);
    }
}
# endif /* NO_DEBUGGING */

/* Primarily for debugging support: */
/* Is the address p in one of the registered static               */
/* root sections?                                     */
GC_bool GC_is_static_root(p)
ptr_t p;
{
    static int last_root_set = MAX_ROOT_SETS;
    register int i;
    
    
    if (last_root_set < n_root_sets
      && p >= GC_static_roots[last_root_set].r_start
        && p < GC_static_roots[last_root_set].r_end) return(TRUE);
    for (i = 0; i < n_root_sets; i++) {
      if (p >= GC_static_roots[i].r_start
            && p < GC_static_roots[i].r_end) {
            last_root_set = i;
            return(TRUE);
        }
    }
    return(FALSE);
}

#if !defined(MSWIN32) && !defined(MSWINCE)
/* 
#   define LOG_RT_SIZE 6
#   define RT_SIZE (1 << LOG_RT_SIZE)  -- Power of 2, may be != MAX_ROOT_SETS

    struct roots * GC_root_index[RT_SIZE];
      -- Hash table header.  Used only to check whether a range is
      -- already present.
      -- really defined in gc_priv.h
*/

static int rt_hash(addr)
char * addr;
{
    word result = (word) addr;
#   if CPP_WORDSZ > 8*LOG_RT_SIZE
      result ^= result >> 8*LOG_RT_SIZE;
#   endif
#   if CPP_WORDSZ > 4*LOG_RT_SIZE
      result ^= result >> 4*LOG_RT_SIZE;
#   endif
    result ^= result >> 2*LOG_RT_SIZE;
    result ^= result >> LOG_RT_SIZE;
    result &= (RT_SIZE-1);
    return(result);
}

/* Is a range starting at b already in the table? If so return a  */
/* pointer to it, else NIL.                                 */
struct roots * GC_roots_present(b)
char *b;
{
    register int h = rt_hash(b);
    register struct roots *p = GC_root_index[h];
    
    while (p != 0) {
        if (p -> r_start == (ptr_t)b) return(p);
        p = p -> r_next;
    }
    return(FALSE);
}

/* Add the given root structure to the index. */
static void add_roots_to_index(p)
struct roots *p;
{
    register int h = rt_hash(p -> r_start);
    
    p -> r_next = GC_root_index[h];
    GC_root_index[h] = p;
}

# else /* MSWIN32 || MSWINCE */

#   define add_roots_to_index(p)

# endif




word GC_root_size = 0;

void GC_add_roots(b, e)
char * b; char * e;
{
    DCL_LOCK_STATE;
    
    DISABLE_SIGNALS();
    LOCK();
    GC_add_roots_inner(b, e, FALSE);
    UNLOCK();
    ENABLE_SIGNALS();
}


/* Add [b,e) to the root set.  Adding the same interval a second time   */
/* is a moderately fast noop, and hence benign.  We do not handle */
/* different but overlapping intervals efficiently.  (We do handle      */
/* them correctly.)                                         */
/* Tmp specifies that the interval may be deleted before          */
/* reregistering dynamic libraries.                         */ 
void GC_add_roots_inner(b, e, tmp)
char * b; char * e;
GC_bool tmp;
{
    struct roots * old;
    
#   if defined(MSWIN32) || defined(MSWINCE)
      /* Spend the time to ensure that there are no overlapping   */
      /* or adjacent intervals.                             */
      /* This could be done faster with e.g. a              */
      /* balanced tree.  But the execution time here is           */
      /* virtually guaranteed to be dominated by the time it      */
      /* takes to scan the roots.                     */
      {
        register int i;
        
        for (i = 0; i < n_root_sets; i++) {
            old = GC_static_roots + i;
            if ((ptr_t)b <= old -> r_end && (ptr_t)e >= old -> r_start) {
                if ((ptr_t)b < old -> r_start) {
                    old -> r_start = (ptr_t)b;
                    GC_root_size += (old -> r_start - (ptr_t)b);
                }
                if ((ptr_t)e > old -> r_end) {
                    old -> r_end = (ptr_t)e;
                    GC_root_size += ((ptr_t)e - old -> r_end);
                }
                old -> r_tmp &= tmp;
                break;
            }
        }
        if (i < n_root_sets) {
          /* merge other overlapping intervals */
            struct roots *other;
            
            for (i++; i < n_root_sets; i++) {
              other = GC_static_roots + i;
              b = (char *)(other -> r_start);
              e = (char *)(other -> r_end);
              if ((ptr_t)b <= old -> r_end && (ptr_t)e >= old -> r_start) {
                if ((ptr_t)b < old -> r_start) {
                    old -> r_start = (ptr_t)b;
                    GC_root_size += (old -> r_start - (ptr_t)b);
                }
                if ((ptr_t)e > old -> r_end) {
                    old -> r_end = (ptr_t)e;
                    GC_root_size += ((ptr_t)e - old -> r_end);
                }
                old -> r_tmp &= other -> r_tmp;
                /* Delete this entry. */
                  GC_root_size -= (other -> r_end - other -> r_start);
                  other -> r_start = GC_static_roots[n_root_sets-1].r_start;
                  other -> r_end = GC_static_roots[n_root_sets-1].r_end;
                                  n_root_sets--;
              }
            }
          return;
        }
      }
#   else
      old = GC_roots_present(b);
      if (old != 0) {
        if ((ptr_t)e <= old -> r_end) /* already there */ return;
        /* else extend */
        GC_root_size += (ptr_t)e - old -> r_end;
        old -> r_end = (ptr_t)e;
        return;
      }
#   endif
    if (n_root_sets == MAX_ROOT_SETS) {
        ABORT("Too many root sets\n");
    }
    GC_static_roots[n_root_sets].r_start = (ptr_t)b;
    GC_static_roots[n_root_sets].r_end = (ptr_t)e;
    GC_static_roots[n_root_sets].r_tmp = tmp;
#   if !defined(MSWIN32) && !defined(MSWINCE)
      GC_static_roots[n_root_sets].r_next = 0;
#   endif
    add_roots_to_index(GC_static_roots + n_root_sets);
    GC_root_size += (ptr_t)e - (ptr_t)b;
    n_root_sets++;
}

static GC_bool roots_were_cleared = FALSE;

void GC_clear_roots GC_PROTO((void))
{
    DCL_LOCK_STATE;
    
    DISABLE_SIGNALS();
    LOCK();
    roots_were_cleared = TRUE;
    n_root_sets = 0;
    GC_root_size = 0;
#   if !defined(MSWIN32) && !defined(MSWINCE)
    {
      register int i;
      
      for (i = 0; i < RT_SIZE; i++) GC_root_index[i] = 0;
    }
#   endif
    UNLOCK();
    ENABLE_SIGNALS();
}

/* Internal use only; lock held.    */
static void GC_remove_root_at_pos(i) 
int i;
{
    GC_root_size -= (GC_static_roots[i].r_end - GC_static_roots[i].r_start);
    GC_static_roots[i].r_start = GC_static_roots[n_root_sets-1].r_start;
    GC_static_roots[i].r_end = GC_static_roots[n_root_sets-1].r_end;
    GC_static_roots[i].r_tmp = GC_static_roots[n_root_sets-1].r_tmp;
    n_root_sets--;
}

#if !defined(MSWIN32) && !defined(MSWINCE)
static void GC_rebuild_root_index()
{
    register int i;
      
    for (i = 0; i < RT_SIZE; i++) GC_root_index[i] = 0;
    for (i = 0; i < n_root_sets; i++)
      add_roots_to_index(GC_static_roots + i);
}
#endif

/* Internal use only; lock held.    */
void GC_remove_tmp_roots()
{
    register int i;
    
    for (i = 0; i < n_root_sets; ) {
      if (GC_static_roots[i].r_tmp) {
            GC_remove_root_at_pos(i);
      } else {
          i++;
    }
    }
    #if !defined(MSWIN32) && !defined(MSWINCE)
    GC_rebuild_root_index();
    #endif
}

#if !defined(MSWIN32) && !defined(MSWINCE)
void GC_remove_roots(b, e)
char * b; char * e;
{
    DCL_LOCK_STATE;
    
    DISABLE_SIGNALS();
    LOCK();
    GC_remove_roots_inner(b, e);
    UNLOCK();
    ENABLE_SIGNALS();
}

/* Should only be called when the lock is held */
void GC_remove_roots_inner(b,e)
char * b; char * e;
{
    int i;
    for (i = 0; i < n_root_sets; ) {
      if (GC_static_roots[i].r_start >= (ptr_t)b && GC_static_roots[i].r_end <= (ptr_t)e) {
            GC_remove_root_at_pos(i);
      } else {
          i++;
      }
    }
    GC_rebuild_root_index();
}
#endif /* !defined(MSWIN32) && !defined(MSWINCE) */

#if defined(MSWIN32) || defined(_WIN32_WCE_EMULATION)
/* Workaround for the OS mapping and unmapping behind our back:         */
/* Is the address p in one of the temporary static root sections? */
GC_bool GC_is_tmp_root(p)
ptr_t p;
{
    static int last_root_set = MAX_ROOT_SETS;
    register int i;
    
    if (last_root_set < n_root_sets
      && p >= GC_static_roots[last_root_set].r_start
        && p < GC_static_roots[last_root_set].r_end)
      return GC_static_roots[last_root_set].r_tmp;
    for (i = 0; i < n_root_sets; i++) {
      if (p >= GC_static_roots[i].r_start
            && p < GC_static_roots[i].r_end) {
            last_root_set = i;
            return GC_static_roots[i].r_tmp;
        }
    }
    return(FALSE);
}
#endif /* MSWIN32 || _WIN32_WCE_EMULATION */

ptr_t GC_approx_sp()
{
    VOLATILE word dummy;

    dummy = 42;   /* Force stack to grow if necessary.      Otherwise the     */
            /* later accesses might cause the kernel to think we're     */
            /* doing something wrong.                       */
#   ifdef _MSC_VER
#     pragma warning(disable:4172)
#   endif
    return((ptr_t)(&dummy));
#   ifdef _MSC_VER
#     pragma warning(default:4172)
#   endif
}

/*
 * Data structure for excluded static roots.
 * Real declaration is in gc_priv.h.

struct exclusion {
    ptr_t e_start;
    ptr_t e_end;
};

struct exclusion GC_excl_table[MAX_EXCLUSIONS];
                              -- Array of exclusions, ascending
                              -- address order.
*/

size_t GC_excl_table_entries = 0;   /* Number of entries in use.    */

/* Return the first exclusion range that includes an address >= start_addr */
/* Assumes the exclusion table contains at least one entry (namely the     */
/* GC data structures).                                        */
struct exclusion * GC_next_exclusion(start_addr)
ptr_t start_addr;
{
    size_t low = 0;
    size_t high = GC_excl_table_entries - 1;
    size_t mid;

    while (high > low) {
      mid = (low + high) >> 1;
      /* low <= mid < high    */
      if ((word) GC_excl_table[mid].e_end <= (word) start_addr) {
          low = mid + 1;
      } else {
          high = mid;
      }
    }
    if ((word) GC_excl_table[low].e_end <= (word) start_addr) return 0;
    return GC_excl_table + low;
}

void GC_exclude_static_roots(start, finish)
GC_PTR start;
GC_PTR finish;
{
    struct exclusion * next;
    size_t next_index, i;

    if (0 == GC_excl_table_entries) {
      next = 0;
    } else {
      next = GC_next_exclusion(start);
    }
    if (0 != next) {
      if ((word)(next -> e_start) < (word) finish) {
      /* incomplete error check. */
      ABORT("exclusion ranges overlap");
      }  
      if ((word)(next -> e_start) == (word) finish) {
        /* extend old range backwards     */
          next -> e_start = (ptr_t)start;
        return;
      }
      next_index = next - GC_excl_table;
      for (i = GC_excl_table_entries; i > next_index; --i) {
      GC_excl_table[i] = GC_excl_table[i-1];
      }
    } else {
      next_index = GC_excl_table_entries;
    }
    if (GC_excl_table_entries == MAX_EXCLUSIONS) ABORT("Too many exclusions");
    GC_excl_table[next_index].e_start = (ptr_t)start;
    GC_excl_table[next_index].e_end = (ptr_t)finish;
    ++GC_excl_table_entries;
}

/* Invoke push_conditional on ranges that are not excluded. */
void GC_push_conditional_with_exclusions(bottom, top, all)
ptr_t bottom;
ptr_t top;
int all;
{
    struct exclusion * next;
    ptr_t excl_start;

    while (bottom < top) {
        next = GC_next_exclusion(bottom);
      if (0 == next || (excl_start = next -> e_start) >= top) {
          GC_push_conditional(bottom, top, all);
          return;
      }
      if (excl_start > bottom) GC_push_conditional(bottom, excl_start, all);
      bottom = next -> e_end;
    }
}

/*
 * In the absence of threads, push the stack contents.
 * In the presence of threads, push enough of the current stack
 * to ensure that callee-save registers saved in collector frames have been
 * seen.
 */
void GC_push_current_stack(cold_gc_frame)
ptr_t cold_gc_frame;
{
#   if defined(THREADS)
      if (0 == cold_gc_frame) return;
#       ifdef STACK_GROWS_DOWN
        GC_push_all_eager(GC_approx_sp(), cold_gc_frame);
        /* For IA64, the register stack backing store is handled  */
        /* in the thread-specific code.                     */
#       else
        GC_push_all_eager( cold_gc_frame, GC_approx_sp() );
#       endif
#   else
#     ifdef STACK_GROWS_DOWN
          GC_push_all_stack_partially_eager( GC_approx_sp(), GC_stackbottom,
                                     cold_gc_frame );
#         ifdef IA64
            /* We also need to push the register stack backing store. */
            /* This should really be done in the same way as the  */
            /* regular stack.  For now we fudge it a bit.         */
            /* Note that the backing store grows up, so we can't use    */
            /* GC_push_all_stack_partially_eager.                 */
            {
            extern word GC_save_regs_ret_val;
                  /* Previously set to backing store pointer.     */
            ptr_t bsp = (ptr_t) GC_save_regs_ret_val;
              ptr_t cold_gc_bs_pointer;
            if (GC_all_interior_pointers) {
                cold_gc_bs_pointer = bsp - 2048;
              if (cold_gc_bs_pointer < BACKING_STORE_BASE) {
                cold_gc_bs_pointer = BACKING_STORE_BASE;
              } else {
                GC_push_all_stack(BACKING_STORE_BASE, cold_gc_bs_pointer);
              }
            } else {
              cold_gc_bs_pointer = BACKING_STORE_BASE;
            }
            GC_push_all_eager(cold_gc_bs_pointer, bsp);
            /* All values should be sufficiently aligned that we  */
            /* dont have to worry about the boundary.       */
            }
#         endif
#       else
          GC_push_all_stack_partially_eager( GC_stackbottom, GC_approx_sp(),
                                     cold_gc_frame );
#       endif
#   endif /* !THREADS */
}

/*
 * Push GC internal roots.  Only called if there is some reason to believe
 * these would not otherwise get registered.
 */
void GC_push_gc_structures GC_PROTO((void))
{
    GC_push_finalizer_structures();
    GC_push_stubborn_structures();
#   if defined(THREADS)
      GC_push_thread_structures();
#   endif
}

#ifdef THREAD_LOCAL_ALLOC
  void GC_mark_thread_local_free_lists();
#endif

void GC_cond_register_dynamic_libraries()
{
# if (defined(DYNAMIC_LOADING) || defined(MSWIN32) || defined(MSWINCE) \
     || defined(PCR)) && !defined(SRC_M3)
    GC_remove_tmp_roots();
    if (!GC_no_dls) GC_register_dynamic_libraries();
# else
    GC_no_dls = TRUE;
# endif
}

/*
 * Call the mark routines (GC_tl_push for a single pointer, GC_push_conditional
 * on groups of pointers) on every top level accessible pointer.
 * If all is FALSE, arrange to push only possibly altered values.
 * Cold_gc_frame is an address inside a GC frame that
 * remains valid until all marking is complete.
 * A zero value indicates that it's OK to miss some
 * register values.
 */
void GC_push_roots(all, cold_gc_frame)
GC_bool all;
ptr_t cold_gc_frame;
{
    int i;
    int kind;

    /*
     * Next push static data.  This must happen early on, since it's
     * not robust against mark stack overflow.
     */
     /* Reregister dynamic libraries, in case one got added.            */
     /* There is some argument for doing this as late as possible,      */
     /* especially on win32, where it can change asynchronously.  */
     /* In those cases, we do it here.  But on other platforms, it's    */
     /* not safe with the world stopped, so we do it earlier.           */
#      if !defined(REGISTER_LIBRARIES_EARLY)
         GC_cond_register_dynamic_libraries();
#      endif

     /* Mark everything in static data areas                             */
       for (i = 0; i < n_root_sets; i++) {
         GC_push_conditional_with_exclusions(
                       GC_static_roots[i].r_start,
                       GC_static_roots[i].r_end, all);
       }

     /* Mark all free list header blocks, if those were allocated from  */
     /* the garbage collected heap.  This makes sure they don't   */
     /* disappear if we are not marking from static data.  It also      */
     /* saves us the trouble of scanning them, and possibly that of     */
     /* marking the freelists.                                    */
       for (kind = 0; kind < GC_n_kinds; kind++) {
       GC_PTR base = GC_base(GC_obj_kinds[kind].ok_freelist);
       if (0 != base) {
         GC_set_mark_bit(base);
       }
       }
       
     /* Mark from GC internal roots if those might otherwise have */
     /* been excluded.                                      */
       if (GC_no_dls || roots_were_cleared) {
         GC_push_gc_structures();
       }

     /* Mark thread local free lists, even if their mark    */
     /* descriptor excludes the link field.                 */
     /* If the world is not stopped, this is unsafe.  It is */
     /* also unnecessary, since we will do this again with the    */
     /* world stopped.                                */
#      ifdef THREAD_LOCAL_ALLOC
         if (GC_world_stopped) GC_mark_thread_local_free_lists();
#      endif

    /*
     * Now traverse stacks, and mark from register contents.
     * These must be done last, since they can legitimately overflow
     * the mark stack.
     */
#   ifdef USE_GENERIC_PUSH_REGS
      GC_generic_push_regs(cold_gc_frame);
      /* Also pushes stack, so that we catch callee-save registers      */
      /* saved inside the GC_push_regs frame.                     */
#   else
       /*
        * push registers - i.e., call GC_push_one(r) for each
        * register contents r.
        */
        GC_push_regs(); /* usually defined in machine_dep.c */
      GC_push_current_stack(cold_gc_frame);
      /* In the threads case, this only pushes collector frames.      */
      /* In the case of linux threads on IA64, the hot section of */
      /* the main stack is marked here, but the register stack    */
      /* backing store is handled in the threads-specific code.   */
#   endif
    if (GC_push_other_roots != 0) (*GC_push_other_roots)();
      /* In the threads case, this also pushes thread stacks.     */
        /* Note that without interior pointer recognition lots    */
      /* of stuff may have been pushed already, and this    */
      /* should be careful about mark stack overflows.      */
}


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