libdw/cie.c

/* CIE reading.
   Copyright (C) 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
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   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
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#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);
}