libdwfl/cu.c

/* Keeping track of DWARF compilation units in libdwfl.
   Copyright (C) 2005 Red Hat, Inc.

   This program is Open Source software; you can redistribute it and/or
   modify it under the terms of the Open Software License version 1.0 as
   published by the Open Source Initiative.

   You should have received a copy of the Open Software License along
   with this program; if not, you may obtain a copy of the Open Software
   License version 1.0 from http://www.opensource.org/licenses/osl.php or
   by writing the Open Source Initiative c/o Lawrence Rosen, Esq.,
   3001 King Ranch Road, Ukiah, CA 95482.   */

#include "libdwflP.h"
#include "../libdw/libdwP.h"
#include "../libdw/memory-access.h"
#include <search.h>


static inline Dwarf_Arange *
dwar (Dwfl_Module *mod, unsigned int idx)
{
  return &mod->dw->aranges->info[mod->aranges[idx].arange];
}


static Dwfl_Error
addrarange (Dwfl_Module *mod, Dwarf_Addr addr, struct dwfl_arange **arange)
{
  if (mod->aranges == NULL)
    {
      Dwarf_Aranges *dwaranges;
      if (dwarf_getaranges (mod->dw, &dwaranges, NULL) != 0)
	return DWFL_E_LIBDW;

      struct dwfl_arange *aranges = malloc (dwaranges->naranges
					    * sizeof *aranges);
      if (unlikely (aranges == NULL))
	return DWFL_E_NOMEM;

      /* libdw has sorted its list by address, which is how we want it.
	 But the sorted list is full of not-quite-contiguous runs pointing
	 to the same CU.  We don't care about the little gaps inside the
	 module, we'll consider them part of the surrounding CU anyway.
	 Collect our own array with just one record for each run of ranges
	 pointing to one CU.  */

      size_t naranges = 0;
      Dwarf_Off lastcu = 0;
      for (size_t i = 0; i < dwaranges->naranges; ++i)
	if (i == 0 || dwaranges->info[i].offset != lastcu)
	  {
	    aranges[naranges].arange = i;
	    aranges[naranges].cu = NULL;
	    ++naranges;
	    lastcu = dwaranges->info[i].offset;
	  }

      /* Store the final array, which is probably much smaller than before.  */
      mod->naranges = naranges;
      mod->aranges = (realloc (aranges, naranges * sizeof aranges[0])
		      ?: aranges);
      mod->lazycu += naranges;
    }

  /* The address must be inside the module to begin with.  */
  addr -= mod->debug.bias;

  /* The ranges are sorted by address, so we can use binary search.  */
  size_t l = 0, u = mod->naranges;
  while (l < u)
    {
      size_t idx = (l + u) / 2;
      Dwarf_Addr start = dwar (mod, idx)->addr;
      if (addr < start)
	{
	  u = idx;
	  continue;
	}
      else if (addr > start)
	{
	  if (idx + 1 < mod->naranges)
	    {
	      if (addr >= dwar (mod, idx + 1)->addr)
		{
		  l = idx + 1;
		  continue;
		}
	    }
	  else
	    {
	      /* It might be in the last range.  */
	      const Dwarf_Arange *last
		= &mod->dw->aranges->info[mod->dw->aranges->naranges - 1];
	      if (addr > last->addr + last->length)
		break;
	    }
	}

      *arange = &mod->aranges[idx];
      return DWFL_E_NOERROR;
    }

  return DWFL_E_ADDR_OUTOFRANGE;
}


static void
nofree (void *arg)
{
  struct dwfl_cu *cu = arg;
  if (cu == (void *) -1l)
    return;

  assert (cu->mod->lazycu == 0);
}

/* One reason fewer to keep the lazy lookup table for CUs.  */
static inline void
less_lazy (Dwfl_Module *mod)
{
  if (--mod->lazycu > 0)
    return;

  /* We know about all the CUs now, we don't need this table.  */
  tdestroy (mod->lazy_cu_root, nofree);
  mod->lazy_cu_root = NULL;
}

static inline Dwarf_Off
cudie_offset (const struct dwfl_cu *cu)
{
  return cu->die.cu->start + 3 * cu->die.cu->offset_size - 4 + 3;
}

static int
compare_cukey (const void *a, const void *b)
{
  return cudie_offset (a) - cudie_offset (b);
}

/* Intern the CU if necessary.  */
static Dwfl_Error
intern_cu (Dwfl_Module *mod, Dwarf_Off cuoff, struct dwfl_cu **result)
{
  struct Dwarf_CU dwkey;
  struct dwfl_cu key;
  key.die.cu = &dwkey;
  dwkey.offset_size = 0;
  dwkey.start = cuoff - (3 * 0 - 4 + 3);
  struct dwfl_cu **found = tsearch (&key, &mod->lazy_cu_root, &compare_cukey);
  if (unlikely (found == NULL))
    return DWFL_E_NOMEM;

  if (*found == &key || *found == NULL)
    {
      if (unlikely (cuoff + 4 >= mod->dw->sectiondata[IDX_debug_info]->d_size))
	{
	  /* This is the EOF marker.  Now we have interned all the CUs.
	     One increment in MOD->lazycu counts not having hit EOF yet.  */
	  *found = (void *) -1l;
	  less_lazy (mod);
	}
      else
	{
	  /* This is a new entry, meaning we haven't looked at this CU.  */

	  *found = NULL;

	  struct dwfl_cu *cu = malloc (sizeof *cu);
	  if (unlikely (cu == NULL))
	    return DWFL_E_NOMEM;

	  cu->mod = mod;
	  cu->next = NULL;
	  cu->lines = NULL;

	  /* XXX use non-searching lookup */
	  Dwarf_Die *die = dwarf_offdie (mod->dw, cuoff, &cu->die);
	  if (die == NULL)
	    return DWFL_E_LIBDW;
	  assert (die == &cu->die);

	  struct dwfl_cu **newvec = realloc (mod->cu, ((mod->ncu + 1)
						       * sizeof (mod->cu[0])));
	  if (newvec == NULL)
	    {
	      free (cu);
	      return DWFL_E_NOMEM;
	    }
	  mod->cu = newvec;

	  mod->cu[mod->ncu++] = cu;
	  if (cu->die.cu->start == 0)
	    mod->first_cu = cu;

	  *found = cu;
	}
    }

  *result = *found;
  return DWFL_E_NOERROR;
}


/* Traverse all the CUs in the module.  */

Dwfl_Error
internal_function_def
__libdwfl_nextcu (Dwfl_Module *mod, struct dwfl_cu *lastcu,
		  struct dwfl_cu **cu)
{
  Dwarf_Off cuoff;
  struct dwfl_cu **nextp;

  if (lastcu == NULL)
    {
      /* Start the traversal.  */
      cuoff = 0;
      nextp = &mod->first_cu;
    }
  else
    {
      /* Continue following LASTCU.  */
      cuoff = lastcu->die.cu->end;
      nextp = &lastcu->next;
    }

  if (*nextp == NULL)
    {
      size_t cuhdrsz;
      Dwarf_Off nextoff;
      if (dwarf_nextcu (mod->dw, cuoff, &nextoff, &cuhdrsz,
			NULL, NULL, NULL) != 0)
	return DWFL_E_LIBDW;

      Dwfl_Error result = intern_cu (mod, cuoff + cuhdrsz, nextp);
      if (result != DWFL_E_NOERROR)
	return result;

      if ((*nextp)->next == NULL && nextoff == (Dwarf_Off) -1l)
	(*nextp)->next = (void *) -1l;
    }

  *cu = *nextp == (void *) -1l ? NULL : *nextp;
  return DWFL_E_NOERROR;
}


/* Intern the CU arange points to, if necessary.  */

static Dwfl_Error
arangecu (Dwfl_Module *mod, struct dwfl_arange *arange, struct dwfl_cu **cu)
{
  if (arange->cu == NULL)
    {
      const Dwarf_Arange *dwarange = &mod->dw->aranges->info[arange->arange];
      Dwfl_Error result = intern_cu (mod, dwarange->offset, &arange->cu);
      if (result != DWFL_E_NOERROR)
	return result;
      assert (arange->cu != NULL && arange->cu != (void *) -1l);
      less_lazy (mod);		/* Each arange with null ->cu counts once.  */
    }

  *cu = arange->cu;
  return DWFL_E_NOERROR;
}

Dwfl_Error
internal_function_def
__libdwfl_addrcu (Dwfl_Module *mod, Dwarf_Addr addr, struct dwfl_cu **cu)
{
  struct dwfl_arange *arange;
  return addrarange (mod, addr, &arange) ?: arangecu (mod, arange, cu);
}