xref: /third_party/elfutils/libdw/cie.c

/* CIE reading.
   Copyright (C) 2009-2010 Red Hat, Inc.
   This file is part of elfutils.

   This file is free software; you can redistribute it and/or modify
   it under the terms of either

     * the GNU Lesser General Public License as published by the Free
       Software Foundation; either version 3 of the License, or (at
       your option) any later version

   or

     * the GNU General Public License as published by the Free
       Software Foundation; either version 2 of the License, or (at
       your option) any later version

   or both in parallel, as here.

   elfutils 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.

   You should have received copies of the GNU General Public License and
   the GNU Lesser General Public License along with this program.  If
   not, see <http://www.gnu.org/licenses/>.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include "cfi.h"
#include "encoded-value.h"
#include <assert.h>
#include <search.h>
#include <stdlib.h>


static int
compare_cie (const void *a, const void *b)
{
  const struct dwarf_cie *cie1 = a;
  const struct dwarf_cie *cie2 = b;
  if (cie1->offset < cie2->offset)
    return -1;
  if (cie1->offset > cie2->offset)
    return 1;
  return 0;
}

/* There is no CIE at OFFSET in the tree.  Add it.  */
static struct dwarf_cie *
intern_new_cie (Dwarf_CFI *cache, Dwarf_Off offset, const Dwarf_CIE *info)
{
  struct dwarf_cie *cie = malloc (sizeof (struct dwarf_cie));
  if (cie == NULL)
    {
      __libdw_seterrno (DWARF_E_NOMEM);
      return NULL;
    }

  cie->offset = offset;
  cie->code_alignment_factor = info->code_alignment_factor;
  cie->data_alignment_factor = info->data_alignment_factor;
  cie->return_address_register = info->return_address_register;

  cie->fde_augmentation_data_size = 0;
  cie->sized_augmentation_data = false;
  cie->signal_frame = false;

  cie->fde_encoding = DW_EH_PE_absptr;
  cie->lsda_encoding = DW_EH_PE_omit;

  /* Grok the augmentation string and its data.  */
  const uint8_t *data = info->augmentation_data;
  for (const char *ap = info->augmentation; *ap != '\0'; ++ap)
    {
      uint8_t encoding;
      switch (*ap)
	{
	case 'z':
	  cie->sized_augmentation_data = true;
	  continue;

	case 'S':
	  cie->signal_frame = true;
	  continue;

	case 'L':		/* LSDA pointer encoding byte.  */
	  cie->lsda_encoding = *data++;
	  if (!cie->sized_augmentation_data)
	    cie->fde_augmentation_data_size
	      += encoded_value_size (&cache->data->d, cache->e_ident,
				     cie->lsda_encoding, NULL);
	  continue;

	case 'R':		/* FDE address encoding byte.  */
	  cie->fde_encoding = *data++;
	  continue;

	case 'P':		/* Skip personality routine.  */
	  encoding = *data++;
	  data += encoded_value_size (&cache->data->d, cache->e_ident,
				      encoding, data);
	  continue;

	default:
	  /* Unknown augmentation string.  If we have 'z' we can ignore it,
	     otherwise we must bail out.  */
	  if (cie->sized_augmentation_data)
	    continue;
	}
      /* We only get here when we need to bail out.  */
      break;
    }

  if ((cie->fde_encoding & 0x0f) == DW_EH_PE_absptr)
    {
      /* Canonicalize encoding to a specific size.  */
      assert (DW_EH_PE_absptr == 0);

      /* XXX should get from dwarf_next_cfi with v4 header.  */
      uint_fast8_t address_size
	= cache->e_ident[EI_CLASS] == ELFCLASS32 ? 4 : 8;
      switch (address_size)
	{
	case 8:
	  cie->fde_encoding |= DW_EH_PE_udata8;
	  break;
	case 4:
	  cie->fde_encoding |= DW_EH_PE_udata4;
	  break;
	default:
	  free (cie);
	  __libdw_seterrno (DWARF_E_INVALID_DWARF);
	  return NULL;
	}
    }

  /* Save the initial instructions to be played out into initial state.  */
  cie->initial_instructions = info->initial_instructions;
  cie->initial_instructions_end = info->initial_instructions_end;
  cie->initial_state = NULL;

  /* Add the new entry to the search tree.  */
  if (tsearch (cie, &cache->cie_tree, &compare_cie) == NULL)
    {
      free (cie);
      __libdw_seterrno (DWARF_E_NOMEM);
      return NULL;
    }

  return cie;
}

/* Look up a CIE_pointer for random access.  */
struct dwarf_cie *
internal_function
__libdw_find_cie (Dwarf_CFI *cache, Dwarf_Off offset)
{
  const struct dwarf_cie cie_key = { .offset = offset };
  struct dwarf_cie **found = tfind (&cie_key, &cache->cie_tree, &compare_cie);
  if (found != NULL)
    return *found;

  /* We have not read this CIE yet.  Go find it.  */
  Dwarf_Off next_offset = offset;
  Dwarf_CFI_Entry entry;
  int result = INTUSE(dwarf_next_cfi) (cache->e_ident,
				       &cache->data->d, CFI_IS_EH (cache),
				       offset, &next_offset, &entry);
  if (result != 0 || entry.cie.CIE_id != DW_CIE_ID_64)
    {
      __libdw_seterrno (DWARF_E_INVALID_DWARF);
      return NULL;
    }

  /* If this happened to be what we would have read next, notice it.  */
  if (cache->next_offset == offset)
    cache->next_offset = next_offset;

  return intern_new_cie (cache, offset, &entry.cie);
}

/* Enter a CIE encountered while reading through for FDEs.  */
void
internal_function
__libdw_intern_cie (Dwarf_CFI *cache, Dwarf_Off offset, const Dwarf_CIE *info)
{
  const struct dwarf_cie cie_key = { .offset = offset };
  struct dwarf_cie **found = tfind (&cie_key, &cache->cie_tree, &compare_cie);
  if (found == NULL)
    /* We have not read this CIE yet.  Enter it.  */
    (void) intern_new_cie (cache, offset, info);
}