libdwfl/segment.c

/* Manage address space lookup table for libdwfl.
   Copyright (C) 2008, 2009, 2010 Red Hat, Inc.
   This file is part of Red Hat elfutils.

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   it under the terms of the GNU General Public License as published by the
   Free Software Foundation; version 2 of the License.

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   General Public License for more details.

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   this file solely under the GPL without exception.

   Red Hat elfutils is an included package of the Open Invention Network.
   An included package of the Open Invention Network is a package for which
   Open Invention Network licensees cross-license their patents.  No patent
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#include "libdwflP.h"

static GElf_Addr
segment_start (Dwfl *dwfl, GElf_Addr start)
{
  if (dwfl->segment_align > 1)
    start &= -dwfl->segment_align;
  return start;
}

static GElf_Addr
segment_end (Dwfl *dwfl, GElf_Addr end)
{
  if (dwfl->segment_align > 1)
    end = (end + dwfl->segment_align - 1) & -dwfl->segment_align;
  return end;
}

static bool
insert (Dwfl *dwfl, size_t i, GElf_Addr start, GElf_Addr end, int segndx)
{
  bool need_start = (i == 0 || dwfl->lookup_addr[i - 1] != start);
  bool need_end = (i >= dwfl->lookup_elts || dwfl->lookup_addr[i + 1] != end);
  size_t need = need_start + need_end;
  if (need == 0)
    return false;

  if (dwfl->lookup_alloc - dwfl->lookup_elts < need)
    {
      size_t n = dwfl->lookup_alloc == 0 ? 16 : dwfl->lookup_alloc * 2;
      GElf_Addr *naddr = realloc (dwfl->lookup_addr, sizeof naddr[0] * n);
      if (unlikely (naddr == NULL))
	return true;
      int *nsegndx = realloc (dwfl->lookup_segndx, sizeof nsegndx[0] * n);
      if (unlikely (nsegndx == NULL))
	{
	  if (naddr != dwfl->lookup_addr)
	    free (naddr);
	  return true;
	}
      dwfl->lookup_alloc = n;
      dwfl->lookup_addr = naddr;
      dwfl->lookup_segndx = nsegndx;

      if (dwfl->lookup_module != NULL)
	{
	  /* Make sure this array is big enough too.  */
	  Dwfl_Module **old = dwfl->lookup_module;
	  dwfl->lookup_module = realloc (dwfl->lookup_module,
					 sizeof dwfl->lookup_module[0] * n);
	  if (unlikely (dwfl->lookup_module == NULL))
	    {
	      free (old);
	      return true;
	    }
	}
    }

  if (unlikely (i < dwfl->lookup_elts))
    {
      const size_t move = dwfl->lookup_elts - i;
      memmove (&dwfl->lookup_addr[i + need], &dwfl->lookup_addr[i],
	       move * sizeof dwfl->lookup_addr[0]);
      memmove (&dwfl->lookup_segndx[i + need], &dwfl->lookup_segndx[i],
	       move * sizeof dwfl->lookup_segndx[0]);
      if (dwfl->lookup_module != NULL)
	memmove (&dwfl->lookup_module[i + need], &dwfl->lookup_module[i],
		 move * sizeof dwfl->lookup_module[0]);
    }

  if (need_start)
    {
      dwfl->lookup_addr[i] = start;
      dwfl->lookup_segndx[i] = segndx;
      ++i;
    }
  else
    dwfl->lookup_segndx[i - 1] = segndx;

  if (need_end)
    {
      dwfl->lookup_addr[i] = end;
      dwfl->lookup_segndx[i] = -1;
    }

  dwfl->lookup_elts += need;

  return false;
}

static int
lookup (Dwfl *dwfl, GElf_Addr address, int hint)
{
  if (hint >= 0
      && address >= dwfl->lookup_addr[hint]
      && ((size_t) hint + 1 == dwfl->lookup_elts
	  || address < dwfl->lookup_addr[hint + 1]))
    return hint;

  /* Do binary search on the array indexed by module load address.  */
  size_t l = 0, u = dwfl->lookup_elts;
  while (l < u)
    {
      size_t idx = (l + u) / 2;
      if (address < dwfl->lookup_addr[idx])
	u = idx;
      else
	{
	  l = idx + 1;
	  if (l == dwfl->lookup_elts || address < dwfl->lookup_addr[l])
	    return idx;
	}
    }

  return -1;
}

static bool
reify_segments (Dwfl *dwfl)
{
  int hint = -1;
  int highest = -1;
  bool fixup = false;
  for (Dwfl_Module *mod = dwfl->modulelist; mod != NULL; mod = mod->next)
    if (! mod->gc)
      {
	const GElf_Addr start = segment_start (dwfl, mod->low_addr);
	const GElf_Addr end = segment_end (dwfl, mod->high_addr);
	bool resized = false;

	int idx = lookup (dwfl, start, hint);
	if (unlikely (idx < 0))
	  {
	    /* Module starts below any segment.  Insert a low one.  */
	    if (unlikely (insert (dwfl, 0, start, end, -1)))
	      return true;
	    idx = 0;
	    resized = true;
	  }
	else if (dwfl->lookup_addr[idx] > start)
	  {
	    /* The module starts in the middle of this segment.  Split it.  */
	    if (unlikely (insert (dwfl, idx + 1, start, end,
				  dwfl->lookup_segndx[idx])))
	      return true;
	    ++idx;
	    resized = true;
	  }
	else if (dwfl->lookup_addr[idx] < start)
	  {
	    /* The module starts past the end of this segment.
	       Add a new one.  */
	    if (unlikely (insert (dwfl, idx + 1, start, end, -1)))
	      return true;
	    ++idx;
	    resized = true;
	  }

	if ((size_t) idx + 1 < dwfl->lookup_elts
	    && end < dwfl->lookup_addr[idx + 1])
	  {
	    /* The module ends in the middle of this segment.  Split it.  */
	    if (unlikely (insert (dwfl, idx + 1,
				  end, dwfl->lookup_addr[idx + 1], -1)))
	      return true;
	    resized = true;
	  }

	if (dwfl->lookup_module == NULL)
	  {
	    dwfl->lookup_module = calloc (dwfl->lookup_alloc,
					  sizeof dwfl->lookup_module[0]);
	    if (unlikely (dwfl->lookup_module == NULL))
	      return true;
	  }

	/* Cache a backpointer in the module.  */
	mod->segment = idx;

	/* Put MOD in the table for each segment that's inside it.  */
	do
	  dwfl->lookup_module[idx++] = mod;
	while ((size_t) idx < dwfl->lookup_elts
	       && dwfl->lookup_addr[idx] < end);
	assert (dwfl->lookup_module[mod->segment] == mod);

	if (resized && idx - 1 >= highest)
	  /* Expanding the lookup tables invalidated backpointers
	     we've already stored.  Reset those ones.  */
	  fixup = true;

	highest = idx - 1;
	hint = (size_t) idx < dwfl->lookup_elts ? idx : -1;
      }

  if (fixup)
    /* Reset backpointer indices invalidated by table insertions.  */
    for (size_t idx = 0; idx < dwfl->lookup_elts; ++idx)
      if (dwfl->lookup_module[idx] != NULL)
	dwfl->lookup_module[idx]->segment = idx;

  return false;
}

int
dwfl_addrsegment (Dwfl *dwfl, Dwarf_Addr address, Dwfl_Module **mod)
{
  if (unlikely (dwfl == NULL))
    return -1;

  if (unlikely (dwfl->lookup_module == NULL)
      && mod != NULL
      && unlikely (reify_segments (dwfl)))
    {
      __libdwfl_seterrno (DWFL_E_NOMEM);
      return -1;
    }

  int idx = lookup (dwfl, address, -1);
  if (likely (mod != NULL))
    {
      if (unlikely (idx < 0) || unlikely (dwfl->lookup_module == NULL))
	*mod = NULL;
      else
	{
	  *mod = dwfl->lookup_module[idx];

	  /* If this segment does not have a module, but the address is
	     the upper boundary of the previous segment's module, use that.  */
	  if (*mod == NULL && idx > 0 && dwfl->lookup_addr[idx] == address)
	    {
	      *mod = dwfl->lookup_module[idx - 1];
	      if (*mod != NULL && (*mod)->high_addr != address)
		*mod = NULL;
	    }
	}
    }

  if (likely (idx >= 0))
    /* Translate internal segment table index to user segment index.  */
    idx = dwfl->lookup_segndx[idx];

  return idx;
}
INTDEF (dwfl_addrsegment)

int
dwfl_report_segment (Dwfl *dwfl, int ndx, const GElf_Phdr *phdr, GElf_Addr bias,
		     const void *ident)
{
  if (dwfl == NULL)
    return -1;

  if (ndx < 0)
    ndx = dwfl->lookup_tail_ndx;

  if (phdr->p_align > 1 && (dwfl->segment_align <= 1 ||
			    phdr->p_align < dwfl->segment_align))
    dwfl->segment_align = phdr->p_align;

  if (unlikely (dwfl->lookup_module != NULL))
    {
      free (dwfl->lookup_module);
      dwfl->lookup_module = NULL;
    }

  GElf_Addr start = segment_start (dwfl, bias + phdr->p_vaddr);
  GElf_Addr end = segment_end (dwfl, bias + phdr->p_vaddr + phdr->p_memsz);

  /* Coalesce into the last one if contiguous and matching.  */
  if (ndx != dwfl->lookup_tail_ndx
      || ident == NULL
      || ident != dwfl->lookup_tail_ident
      || start != dwfl->lookup_tail_vaddr
      || phdr->p_offset != dwfl->lookup_tail_offset)
    {
      /* Normally just appending keeps us sorted.  */

      size_t i = dwfl->lookup_elts;
      while (i > 0 && unlikely (start < dwfl->lookup_addr[i - 1]))
	--i;

      if (unlikely (insert (dwfl, i, start, end, ndx)))
	{
	  __libdwfl_seterrno (DWFL_E_NOMEM);
	  return -1;
	}
    }

  dwfl->lookup_tail_ident = ident;
  dwfl->lookup_tail_vaddr = end;
  dwfl->lookup_tail_offset = end - bias - phdr->p_vaddr + phdr->p_offset;
  dwfl->lookup_tail_ndx = ndx + 1;

  return ndx;
}
INTDEF (dwfl_report_segment)