Subversion Repositories Kolibri OS

/* Subroutines needed for unwinding stack frames for exception handling.  */

/* Copyright (C) 1997-2015 Free Software Foundation, Inc.

   Contributed by Jason Merrill .

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under

the terms of the GNU General Public License as published by the Free

Software Foundation; either version 3, or (at your option) any later

version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY

WARRANTY; without even the implied warranty of MERCHANTABILITY or

FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

for more details.

Under Section 7 of GPL version 3, you are granted additional

permissions described in the GCC Runtime Library Exception, version

3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and

a copy of the GCC Runtime Library Exception along with this program;

see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

.  */

#ifndef _Unwind_Find_FDE

#include "tconfig.h"

#include "tsystem.h"

#include "coretypes.h"

#include "tm.h"

#include "libgcc_tm.h"

#include "dwarf2.h"

#include "unwind.h"

#define NO_BASE_OF_ENCODED_VALUE

#include "unwind-pe.h"

#include "unwind-dw2-fde.h"

#include "gthr.h"

#endif

/* The unseen_objects list contains objects that have been registered

   but not yet categorized in any way.  The seen_objects list has had

   its pc_begin and count fields initialized at minimum, and is sorted

   by decreasing value of pc_begin.  */

static struct object *unseen_objects;

static struct object *seen_objects;

#ifdef __GTHREAD_MUTEX_INIT

static __gthread_mutex_t object_mutex = __GTHREAD_MUTEX_INIT;

#define init_object_mutex_once()

#else

#ifdef __GTHREAD_MUTEX_INIT_FUNCTION

static __gthread_mutex_t object_mutex;

static void

init_object_mutex (void)

{

  __GTHREAD_MUTEX_INIT_FUNCTION (&object_mutex);

}

static void

init_object_mutex_once (void)

{

  static __gthread_once_t once = __GTHREAD_ONCE_INIT;

  __gthread_once (&once, init_object_mutex);

}

#else

/* ???  Several targets include this file with stubbing parts of gthr.h

   and expect no locking to be done.  */

#define init_object_mutex_once()

static __gthread_mutex_t object_mutex;

#endif

#endif

/* Called from crtbegin.o to register the unwind info for an object.  */

void

__register_frame_info_bases (const void *begin, struct object *ob,

			     void *tbase, void *dbase)

{

  /* If .eh_frame is empty, don't register at all.  */

  if ((const uword *) begin == 0 || *(const uword *) begin == 0)

    return;

  ob->pc_begin = (void *)-1;

  ob->tbase = tbase;

  ob->dbase = dbase;

  ob->u.single = begin;

  ob->s.i = 0;

  ob->s.b.encoding = DW_EH_PE_omit;

#ifdef DWARF2_OBJECT_END_PTR_EXTENSION

  ob->fde_end = NULL;

#endif

  init_object_mutex_once ();

  __gthread_mutex_lock (&object_mutex);

  ob->next = unseen_objects;

  unseen_objects = ob;

  __gthread_mutex_unlock (&object_mutex);

}

void

__register_frame_info (const void *begin, struct object *ob)

{

  __register_frame_info_bases (begin, ob, 0, 0);

}

void

__register_frame (void *begin)

{

  struct object *ob;

  /* If .eh_frame is empty, don't register at all.  */

  if (*(uword *) begin == 0)

    return;

  ob = malloc (sizeof (struct object));

  __register_frame_info (begin, ob);

}

/* Similar, but BEGIN is actually a pointer to a table of unwind entries

   for different translation units.  Called from the file generated by

   collect2.  */

void

__register_frame_info_table_bases (void *begin, struct object *ob,

				   void *tbase, void *dbase)

{

  ob->pc_begin = (void *)-1;

  ob->tbase = tbase;

  ob->dbase = dbase;

  ob->u.array = begin;

  ob->s.i = 0;

  ob->s.b.from_array = 1;

  ob->s.b.encoding = DW_EH_PE_omit;

  init_object_mutex_once ();

  __gthread_mutex_lock (&object_mutex);

  ob->next = unseen_objects;

  unseen_objects = ob;

  __gthread_mutex_unlock (&object_mutex);

}

void

__register_frame_info_table (void *begin, struct object *ob)

{

  __register_frame_info_table_bases (begin, ob, 0, 0);

}

void

__register_frame_table (void *begin)

{

  struct object *ob = malloc (sizeof (struct object));

  __register_frame_info_table (begin, ob);

}

/* Called from crtbegin.o to deregister the unwind info for an object.  */

/* ??? Glibc has for a while now exported __register_frame_info and

   __deregister_frame_info.  If we call __register_frame_info_bases

   from crtbegin (wherein it is declared weak), and this object does

   not get pulled from libgcc.a for other reasons, then the

   invocation of __deregister_frame_info will be resolved from glibc.

   Since the registration did not happen there, we'll die.

   Therefore, declare a new deregistration entry point that does the

   exact same thing, but will resolve to the same library as

   implements __register_frame_info_bases.  */

void *

__deregister_frame_info_bases (const void *begin)

{

  struct object **p;

  struct object *ob = 0;

  /* If .eh_frame is empty, we haven't registered.  */

  if ((const uword *) begin == 0 || *(const uword *) begin == 0)

    return ob;

  init_object_mutex_once ();

  __gthread_mutex_lock (&object_mutex);

  for (p = &unseen_objects; *p ; p = &(*p)->next)

    if ((*p)->u.single == begin)

      {

	ob = *p;

	*p = ob->next;

	goto out;

      }

  for (p = &seen_objects; *p ; p = &(*p)->next)

    if ((*p)->s.b.sorted)

      {

	if ((*p)->u.sort->orig_data == begin)

	  {

	    ob = *p;

	    *p = ob->next;

	    free (ob->u.sort);

	    goto out;

	  }

      }

    else

      {

	if ((*p)->u.single == begin)

	  {

	    ob = *p;

	    *p = ob->next;

	    goto out;

	  }

      }

 out:

  __gthread_mutex_unlock (&object_mutex);

  gcc_assert (ob);

  return (void *) ob;

}

void *

__deregister_frame_info (const void *begin)

{

  return __deregister_frame_info_bases (begin);

}

void

__deregister_frame (void *begin)

{

  /* If .eh_frame is empty, we haven't registered.  */

  if (*(uword *) begin != 0)

    free (__deregister_frame_info (begin));

}

/* Like base_of_encoded_value, but take the base from a struct object

   instead of an _Unwind_Context.  */

static _Unwind_Ptr

base_from_object (unsigned char encoding, struct object *ob)

{

  if (encoding == DW_EH_PE_omit)

    return 0;

  switch (encoding & 0x70)

    {

    case DW_EH_PE_absptr:

    case DW_EH_PE_pcrel:

    case DW_EH_PE_aligned:

      return 0;

    case DW_EH_PE_textrel:

      return (_Unwind_Ptr) ob->tbase;

    case DW_EH_PE_datarel:

      return (_Unwind_Ptr) ob->dbase;

    default:

      gcc_unreachable ();

    }

}

/* Return the FDE pointer encoding from the CIE.  */

/* ??? This is a subset of extract_cie_info from unwind-dw2.c.  */

static int

get_cie_encoding (const struct dwarf_cie *cie)

{

  const unsigned char *aug, *p;

  _Unwind_Ptr dummy;

  _uleb128_t utmp;

  _sleb128_t stmp;

  aug = cie->augmentation;

  p = aug + strlen ((const char *)aug) + 1; /* Skip the augmentation string.  */

  if (__builtin_expect (cie->version >= 4, 0))

    {

      if (p[0] != sizeof (void *) || p[1] != 0)

	return DW_EH_PE_omit;		/* We are not prepared to handle unexpected

					   address sizes or segment selectors.  */

      p += 2;				/* Skip address size and segment size.  */

    }

  if (aug[0] != 'z')

    return DW_EH_PE_absptr;

  p = read_uleb128 (p, &utmp);		/* Skip code alignment.  */

  p = read_sleb128 (p, &stmp);		/* Skip data alignment.  */

  if (cie->version == 1)		/* Skip return address column.  */

    p++;

  else

    p = read_uleb128 (p, &utmp);

  aug++;				/* Skip 'z' */

  p = read_uleb128 (p, &utmp);		/* Skip augmentation length.  */

  while (1)

    {

      /* This is what we're looking for.  */

      if (*aug == 'R')

	return *p;

      /* Personality encoding and pointer.  */

      else if (*aug == 'P')

	{

	  /* ??? Avoid dereferencing indirect pointers, since we're

	     faking the base address.  Gotta keep DW_EH_PE_aligned

	     intact, however.  */

	  p = read_encoded_value_with_base (*p & 0x7F, 0, p + 1, &dummy);

	}

      /* LSDA encoding.  */

      else if (*aug == 'L')

	p++;

      /* Otherwise end of string, or unknown augmentation.  */

      else

	return DW_EH_PE_absptr;

      aug++;

    }

}

static inline int

get_fde_encoding (const struct dwarf_fde *f)

{

  return get_cie_encoding (get_cie (f));

}

/* Sorting an array of FDEs by address.

   (Ideally we would have the linker sort the FDEs so we don't have to do

   it at run time. But the linkers are not yet prepared for this.)  */

/* Comparison routines.  Three variants of increasing complexity.  */

static int

fde_unencoded_compare (struct object *ob __attribute__((unused)),

		       const fde *x, const fde *y)

{

  _Unwind_Ptr x_ptr, y_ptr;

  memcpy (&x_ptr, x->pc_begin, sizeof (_Unwind_Ptr));

  memcpy (&y_ptr, y->pc_begin, sizeof (_Unwind_Ptr));

  if (x_ptr > y_ptr)

    return 1;

  if (x_ptr < y_ptr)

    return -1;

  return 0;

}

static int

fde_single_encoding_compare (struct object *ob, const fde *x, const fde *y)

{

  _Unwind_Ptr base, x_ptr, y_ptr;

  base = base_from_object (ob->s.b.encoding, ob);

  read_encoded_value_with_base (ob->s.b.encoding, base, x->pc_begin, &x_ptr);

  read_encoded_value_with_base (ob->s.b.encoding, base, y->pc_begin, &y_ptr);

  if (x_ptr > y_ptr)

    return 1;

  if (x_ptr < y_ptr)

    return -1;

  return 0;

}

static int

fde_mixed_encoding_compare (struct object *ob, const fde *x, const fde *y)

{

  int x_encoding, y_encoding;

  _Unwind_Ptr x_ptr, y_ptr;

  x_encoding = get_fde_encoding (x);

  read_encoded_value_with_base (x_encoding, base_from_object (x_encoding, ob),

				x->pc_begin, &x_ptr);

  y_encoding = get_fde_encoding (y);

  read_encoded_value_with_base (y_encoding, base_from_object (y_encoding, ob),

				y->pc_begin, &y_ptr);

  if (x_ptr > y_ptr)

    return 1;

  if (x_ptr < y_ptr)

    return -1;

  return 0;

}

typedef int (*fde_compare_t) (struct object *, const fde *, const fde *);

/* This is a special mix of insertion sort and heap sort, optimized for

   the data sets that actually occur. They look like

   101 102 103 127 128 105 108 110 190 111 115 119 125 160 126 129 130.

   I.e. a linearly increasing sequence (coming from functions in the text

   section), with additionally a few unordered elements (coming from functions

   in gnu_linkonce sections) whose values are higher than the values in the

   surrounding linear sequence (but not necessarily higher than the values

   at the end of the linear sequence!).

   The worst-case total run time is O(N) + O(n log (n)), where N is the

   total number of FDEs and n is the number of erratic ones.  */

struct fde_accumulator

{

  struct fde_vector *linear;

  struct fde_vector *erratic;

};

static inline int

start_fde_sort (struct fde_accumulator *accu, size_t count)

{

  size_t size;

  if (! count)

    return 0;

  size = sizeof (struct fde_vector) + sizeof (const fde *) * count;

  if ((accu->linear = malloc (size)))

    {

      accu->linear->count = 0;

      if ((accu->erratic = malloc (size)))

	accu->erratic->count = 0;

      return 1;

    }

  else

    return 0;

}

static inline void

fde_insert (struct fde_accumulator *accu, const fde *this_fde)

{

  if (accu->linear)

    accu->linear->array[accu->linear->count++] = this_fde;

}

/* Split LINEAR into a linear sequence with low values and an erratic

   sequence with high values, put the linear one (of longest possible

   length) into LINEAR and the erratic one into ERRATIC. This is O(N).

   Because the longest linear sequence we are trying to locate within the

   incoming LINEAR array can be interspersed with (high valued) erratic

   entries.  We construct a chain indicating the sequenced entries.

   To avoid having to allocate this chain, we overlay it onto the space of

   the ERRATIC array during construction.  A final pass iterates over the

   chain to determine what should be placed in the ERRATIC array, and

   what is the linear sequence.  This overlay is safe from aliasing.  */

static inline void

fde_split (struct object *ob, fde_compare_t fde_compare,

	   struct fde_vector *linear, struct fde_vector *erratic)

{

  static const fde *marker;

  size_t count = linear->count;

  const fde *const *chain_end = ▮

  size_t i, j, k;

  /* This should optimize out, but it is wise to make sure this assumption

     is correct. Should these have different sizes, we cannot cast between

     them and the overlaying onto ERRATIC will not work.  */

  gcc_assert (sizeof (const fde *) == sizeof (const fde **));

  for (i = 0; i < count; i++)

    {

      const fde *const *probe;

      for (probe = chain_end;

	   probe != &marker && fde_compare (ob, linear->array[i], *probe) < 0;

	   probe = chain_end)

	{

	  chain_end = (const fde *const*) erratic->array[probe - linear->array];

	  erratic->array[probe - linear->array] = NULL;

	}

      erratic->array[i] = (const fde *) chain_end;

      chain_end = &linear->array[i];

    }

  /* Each entry in LINEAR which is part of the linear sequence we have

     discovered will correspond to a non-NULL entry in the chain we built in

     the ERRATIC array.  */

  for (i = j = k = 0; i < count; i++)

    if (erratic->array[i])

      linear->array[j++] = linear->array[i];

    else

      erratic->array[k++] = linear->array[i];

  linear->count = j;

  erratic->count = k;

}

#define SWAP(x,y) do { const fde * tmp = x; x = y; y = tmp; } while (0)

/* Convert a semi-heap to a heap.  A semi-heap is a heap except possibly

   for the first (root) node; push it down to its rightful place.  */

static void

frame_downheap (struct object *ob, fde_compare_t fde_compare, const fde **a,

		int lo, int hi)

{

  int i, j;

  for (i = lo, j = 2*i+1;

       j < hi;

       j = 2*i+1)

    {

      if (j+1 < hi && fde_compare (ob, a[j], a[j+1]) < 0)

	++j;

      if (fde_compare (ob, a[i], a[j]) < 0)

	{

	  SWAP (a[i], a[j]);

	  i = j;

	}

      else

	break;

    }

}

/* This is O(n log(n)).  BSD/OS defines heapsort in stdlib.h, so we must

   use a name that does not conflict.  */

static void

frame_heapsort (struct object *ob, fde_compare_t fde_compare,

		struct fde_vector *erratic)

{

  /* For a description of this algorithm, see:

     Samuel P. Harbison, Guy L. Steele Jr.: C, a reference manual, 2nd ed.,

     p. 60-61.  */

  const fde ** a = erratic->array;

  /* A portion of the array is called a "heap" if for all i>=0:

     If i and 2i+1 are valid indices, then a[i] >= a[2i+1].

     If i and 2i+2 are valid indices, then a[i] >= a[2i+2].  */

  size_t n = erratic->count;

  int m;

  /* Expand our heap incrementally from the end of the array, heapifying

     each resulting semi-heap as we go.  After each step, a[m] is the top

     of a heap.  */

  for (m = n/2-1; m >= 0; --m)

    frame_downheap (ob, fde_compare, a, m, n);

  /* Shrink our heap incrementally from the end of the array, first

     swapping out the largest element a[0] and then re-heapifying the

     resulting semi-heap.  After each step, a[0..m) is a heap.  */

  for (m = n-1; m >= 1; --m)

    {

      SWAP (a[0], a[m]);

      frame_downheap (ob, fde_compare, a, 0, m);

    }

#undef SWAP

}

/* Merge V1 and V2, both sorted, and put the result into V1.  */

static inline void

fde_merge (struct object *ob, fde_compare_t fde_compare,

	   struct fde_vector *v1, struct fde_vector *v2)

{

  size_t i1, i2;

  const fde * fde2;

  i2 = v2->count;

  if (i2 > 0)

    {

      i1 = v1->count;

      do

	{

	  i2--;

	  fde2 = v2->array[i2];

	  while (i1 > 0 && fde_compare (ob, v1->array[i1-1], fde2) > 0)

	    {

	      v1->array[i1+i2] = v1->array[i1-1];

	      i1--;

	    }

	  v1->array[i1+i2] = fde2;

	}

      while (i2 > 0);

      v1->count += v2->count;

    }

}

static inline void

end_fde_sort (struct object *ob, struct fde_accumulator *accu, size_t count)

{

  fde_compare_t fde_compare;

  gcc_assert (!accu->linear || accu->linear->count == count);

  if (ob->s.b.mixed_encoding)

    fde_compare = fde_mixed_encoding_compare;

  else if (ob->s.b.encoding == DW_EH_PE_absptr)

    fde_compare = fde_unencoded_compare;

  else

    fde_compare = fde_single_encoding_compare;

  if (accu->erratic)

    {

      fde_split (ob, fde_compare, accu->linear, accu->erratic);

      gcc_assert (accu->linear->count + accu->erratic->count == count);

      frame_heapsort (ob, fde_compare, accu->erratic);

      fde_merge (ob, fde_compare, accu->linear, accu->erratic);

      free (accu->erratic);

    }

  else

    {

      /* We've not managed to malloc an erratic array,

	 so heap sort in the linear one.  */

      frame_heapsort (ob, fde_compare, accu->linear);

    }

}

/* Update encoding, mixed_encoding, and pc_begin for OB for the

   fde array beginning at THIS_FDE.  Return the number of fdes

   encountered along the way.  */

static size_t

classify_object_over_fdes (struct object *ob, const fde *this_fde)

{

  const struct dwarf_cie *last_cie = 0;

  size_t count = 0;

  int encoding = DW_EH_PE_absptr;

  _Unwind_Ptr base = 0;

  for (; ! last_fde (ob, this_fde); this_fde = next_fde (this_fde))

    {

      const struct dwarf_cie *this_cie;

      _Unwind_Ptr mask, pc_begin;

      /* Skip CIEs.  */

      if (this_fde->CIE_delta == 0)

	continue;

      /* Determine the encoding for this FDE.  Note mixed encoded

	 objects for later.  */

      this_cie = get_cie (this_fde);

      if (this_cie != last_cie)

	{

	  last_cie = this_cie;

	  encoding = get_cie_encoding (this_cie);

	  if (encoding == DW_EH_PE_omit)

	    return -1;

	  base = base_from_object (encoding, ob);

	  if (ob->s.b.encoding == DW_EH_PE_omit)

	    ob->s.b.encoding = encoding;

	  else if (ob->s.b.encoding != encoding)

	    ob->s.b.mixed_encoding = 1;

	}

      read_encoded_value_with_base (encoding, base, this_fde->pc_begin,

				    &pc_begin);

      /* Take care to ignore link-once functions that were removed.

	 In these cases, the function address will be NULL, but if

	 the encoding is smaller than a pointer a true NULL may not

	 be representable.  Assume 0 in the representable bits is NULL.  */

      mask = size_of_encoded_value (encoding);

      if (mask < sizeof (void *))

	mask = (((_Unwind_Ptr) 1) << (mask << 3)) - 1;

      else

	mask = -1;

      if ((pc_begin & mask) == 0)

	continue;

      count += 1;

      if ((void *) pc_begin < ob->pc_begin)

	ob->pc_begin = (void *) pc_begin;

    }

  return count;

}

static void

add_fdes (struct object *ob, struct fde_accumulator *accu, const fde *this_fde)

{

  const struct dwarf_cie *last_cie = 0;

  int encoding = ob->s.b.encoding;

  _Unwind_Ptr base = base_from_object (ob->s.b.encoding, ob);

  for (; ! last_fde (ob, this_fde); this_fde = next_fde (this_fde))

    {

      const struct dwarf_cie *this_cie;

      /* Skip CIEs.  */

      if (this_fde->CIE_delta == 0)

	continue;

      if (ob->s.b.mixed_encoding)

	{

	  /* Determine the encoding for this FDE.  Note mixed encoded

	     objects for later.  */

	  this_cie = get_cie (this_fde);

	  if (this_cie != last_cie)

	    {

	      last_cie = this_cie;

	      encoding = get_cie_encoding (this_cie);

	      base = base_from_object (encoding, ob);

	    }

	}

      if (encoding == DW_EH_PE_absptr)

	{

	  _Unwind_Ptr ptr;

	  memcpy (&ptr, this_fde->pc_begin, sizeof (_Unwind_Ptr));

	  if (ptr == 0)

	    continue;

	}

      else

	{

	  _Unwind_Ptr pc_begin, mask;

	  read_encoded_value_with_base (encoding, base, this_fde->pc_begin,

					&pc_begin);

	  /* Take care to ignore link-once functions that were removed.

	     In these cases, the function address will be NULL, but if

	     the encoding is smaller than a pointer a true NULL may not

	     be representable.  Assume 0 in the representable bits is NULL.  */

	  mask = size_of_encoded_value (encoding);

	  if (mask < sizeof (void *))

	    mask = (((_Unwind_Ptr) 1) << (mask << 3)) - 1;

	  else

	    mask = -1;

	  if ((pc_begin & mask) == 0)

	    continue;

	}

      fde_insert (accu, this_fde);

    }

}

/* Set up a sorted array of pointers to FDEs for a loaded object.  We

   count up the entries before allocating the array because it's likely to

   be faster.  We can be called multiple times, should we have failed to

   allocate a sorted fde array on a previous occasion.  */

static inline void

init_object (struct object* ob)

{

  struct fde_accumulator accu;

  size_t count;

  count = ob->s.b.count;

  if (count == 0)

    {

      if (ob->s.b.from_array)

	{

	  fde **p = ob->u.array;

	  for (count = 0; *p; ++p)

	    {

	      size_t cur_count = classify_object_over_fdes (ob, *p);

	      if (cur_count == (size_t) -1)

		goto unhandled_fdes;

	      count += cur_count;

	    }

	}

      else

	{

	  count = classify_object_over_fdes (ob, ob->u.single);

	  if (count == (size_t) -1)

	    {

	      static const fde terminator;

	    unhandled_fdes:

	      ob->s.i = 0;

	      ob->s.b.encoding = DW_EH_PE_omit;

	      ob->u.single = &terminator;

	      return;

	    }

	}

      /* The count field we have in the main struct object is somewhat

	 limited, but should suffice for virtually all cases.  If the

	 counted value doesn't fit, re-write a zero.  The worst that

	 happens is that we re-count next time -- admittedly non-trivial

	 in that this implies some 2M fdes, but at least we function.  */

      ob->s.b.count = count;

      if (ob->s.b.count != count)

	ob->s.b.count = 0;

    }

  if (!start_fde_sort (&accu, count))

    return;

  if (ob->s.b.from_array)

    {

      fde **p;

      for (p = ob->u.array; *p; ++p)

	add_fdes (ob, &accu, *p);

    }

  else

    add_fdes (ob, &accu, ob->u.single);

  end_fde_sort (ob, &accu, count);

  /* Save the original fde pointer, since this is the key by which the

     DSO will deregister the object.  */

  accu.linear->orig_data = ob->u.single;

  ob->u.sort = accu.linear;

  ob->s.b.sorted = 1;

}

/* A linear search through a set of FDEs for the given PC.  This is

   used when there was insufficient memory to allocate and sort an

   array.  */

static const fde *

linear_search_fdes (struct object *ob, const fde *this_fde, void *pc)

{

  const struct dwarf_cie *last_cie = 0;

  int encoding = ob->s.b.encoding;

  _Unwind_Ptr base = base_from_object (ob->s.b.encoding, ob);

  for (; ! last_fde (ob, this_fde); this_fde = next_fde (this_fde))

    {

      const struct dwarf_cie *this_cie;

      _Unwind_Ptr pc_begin, pc_range;

      /* Skip CIEs.  */

      if (this_fde->CIE_delta == 0)

	continue;

      if (ob->s.b.mixed_encoding)

	{

	  /* Determine the encoding for this FDE.  Note mixed encoded

	     objects for later.  */

	  this_cie = get_cie (this_fde);

	  if (this_cie != last_cie)

	    {

	      last_cie = this_cie;

	      encoding = get_cie_encoding (this_cie);

	      base = base_from_object (encoding, ob);

	    }

	}

      if (encoding == DW_EH_PE_absptr)

	{

	  const _Unwind_Ptr *pc_array = (const _Unwind_Ptr *) this_fde->pc_begin;

	  pc_begin = pc_array[0];

	  pc_range = pc_array[1];

	  if (pc_begin == 0)

	    continue;

	}

      else

	{

	  _Unwind_Ptr mask;

	  const unsigned char *p;

	  p = read_encoded_value_with_base (encoding, base,

					    this_fde->pc_begin, &pc_begin);

	  read_encoded_value_with_base (encoding & 0x0F, 0, p, &pc_range);

	  /* Take care to ignore link-once functions that were removed.

	     In these cases, the function address will be NULL, but if

	     the encoding is smaller than a pointer a true NULL may not

	     be representable.  Assume 0 in the representable bits is NULL.  */

	  mask = size_of_encoded_value (encoding);

	  if (mask < sizeof (void *))

	    mask = (((_Unwind_Ptr) 1) << (mask << 3)) - 1;

	  else

	    mask = -1;

	  if ((pc_begin & mask) == 0)

	    continue;

	}

      if ((_Unwind_Ptr) pc - pc_begin < pc_range)

	return this_fde;

    }

  return NULL;

}

/* Binary search for an FDE containing the given PC.  Here are three

   implementations of increasing complexity.  */

static inline const fde *

binary_search_unencoded_fdes (struct object *ob, void *pc)

{

  struct fde_vector *vec = ob->u.sort;

  size_t lo, hi;

  for (lo = 0, hi = vec->count; lo < hi; )

    {

      size_t i = (lo + hi) / 2;

      const fde *const f = vec->array[i];

      void *pc_begin;

      uaddr pc_range;

      memcpy (&pc_begin, (const void * const *) f->pc_begin, sizeof (void *));

      memcpy (&pc_range, (const uaddr *) f->pc_begin + 1, sizeof (uaddr));

      if (pc < pc_begin)

	hi = i;

      else if (pc >= pc_begin + pc_range)

	lo = i + 1;

      else

	return f;

    }

  return NULL;

}

static inline const fde *

binary_search_single_encoding_fdes (struct object *ob, void *pc)

{

  struct fde_vector *vec = ob->u.sort;

  int encoding = ob->s.b.encoding;

  _Unwind_Ptr base = base_from_object (encoding, ob);

  size_t lo, hi;

  for (lo = 0, hi = vec->count; lo < hi; )

    {

      size_t i = (lo + hi) / 2;

      const fde *f = vec->array[i];

      _Unwind_Ptr pc_begin, pc_range;

      const unsigned char *p;

      p = read_encoded_value_with_base (encoding, base, f->pc_begin,

					&pc_begin);

      read_encoded_value_with_base (encoding & 0x0F, 0, p, &pc_range);

      if ((_Unwind_Ptr) pc < pc_begin)

	hi = i;

      else if ((_Unwind_Ptr) pc >= pc_begin + pc_range)

	lo = i + 1;

      else

	return f;

    }

  return NULL;

}

static inline const fde *

binary_search_mixed_encoding_fdes (struct object *ob, void *pc)

{

  struct fde_vector *vec = ob->u.sort;

  size_t lo, hi;

  for (lo = 0, hi = vec->count; lo < hi; )

    {

      size_t i = (lo + hi) / 2;

      const fde *f = vec->array[i];

      _Unwind_Ptr pc_begin, pc_range;

      const unsigned char *p;

      int encoding;

      encoding = get_fde_encoding (f);

      p = read_encoded_value_with_base (encoding,

					base_from_object (encoding, ob),

					f->pc_begin, &pc_begin);

      read_encoded_value_with_base (encoding & 0x0F, 0, p, &pc_range);

      if ((_Unwind_Ptr) pc < pc_begin)

	hi = i;

      else if ((_Unwind_Ptr) pc >= pc_begin + pc_range)

	lo = i + 1;

      else

	return f;

    }

  return NULL;

}

static const fde *

search_object (struct object* ob, void *pc)

{

  /* If the data hasn't been sorted, try to do this now.  We may have

     more memory available than last time we tried.  */

  if (! ob->s.b.sorted)

    {

      init_object (ob);

      /* Despite the above comment, the normal reason to get here is

	 that we've not processed this object before.  A quick range

	 check is in order.  */

      if (pc < ob->pc_begin)

	return NULL;

    }

  if (ob->s.b.sorted)

    {

      if (ob->s.b.mixed_encoding)

	return binary_search_mixed_encoding_fdes (ob, pc);

      else if (ob->s.b.encoding == DW_EH_PE_absptr)

	return binary_search_unencoded_fdes (ob, pc);

      else

	return binary_search_single_encoding_fdes (ob, pc);

    }

  else

    {

      /* Long slow laborious linear search, cos we've no memory.  */

      if (ob->s.b.from_array)

	{

	  fde **p;

	  for (p = ob->u.array; *p ; p++)

	    {

	      const fde *f = linear_search_fdes (ob, *p, pc);

	      if (f)

		return f;

	    }

	  return NULL;

	}

      else

	return linear_search_fdes (ob, ob->u.single, pc);

    }

}

const fde *

_Unwind_Find_FDE (void *pc, struct dwarf_eh_bases *bases)

{

  struct object *ob;

  const fde *f = NULL;

  init_object_mutex_once ();

  __gthread_mutex_lock (&object_mutex);

  /* Linear search through the classified objects, to find the one

     containing the pc.  Note that pc_begin is sorted descending, and

     we expect objects to be non-overlapping.  */

  for (ob = seen_objects; ob; ob = ob->next)

    if (pc >= ob->pc_begin)

      {

	f = search_object (ob, pc);

	if (f)

	  goto fini;

	break;

      }

  /* Classify and search the objects we've not yet processed.  */

  while ((ob = unseen_objects))

    {

      struct object **p;

      unseen_objects = ob->next;

      f = search_object (ob, pc);

      /* Insert the object into the classified list.  */

      for (p = &seen_objects; *p ; p = &(*p)->next)

	if ((*p)->pc_begin < ob->pc_begin)

	  break;

      ob->next = *p;

      *p = ob;

      if (f)

	goto fini;

    }

 fini:

  __gthread_mutex_unlock (&object_mutex);

  if (f)

    {

      int encoding;

      _Unwind_Ptr func;

      bases->tbase = ob->tbase;

      bases->dbase = ob->dbase;

      encoding = ob->s.b.encoding;

      if (ob->s.b.mixed_encoding)

	encoding = get_fde_encoding (f);

      read_encoded_value_with_base (encoding, base_from_object (encoding, ob),

				    f->pc_begin, &func);

      bases->func = (void *) func;

    }

  return f;

}