dwarf_getabbrev.c revision a5a89687681ca81e82681b56612495c0d087829e 
1/* Get abbreviation at given offset.
2   Copyright (C) 2003, 2004, 2005 Red Hat, Inc.
3   Written by Ulrich Drepper <drepper@redhat.com>, 2003.
4
5   This program is Open Source software; you can redistribute it and/or
6   modify it under the terms of the Open Software License version 1.0 as
7   published by the Open Source Initiative.
8
9   You should have received a copy of the Open Software License along
10   with this program; if not, you may obtain a copy of the Open Software
11   License version 1.0 from http://www.opensource.org/licenses/osl.php or
12   by writing the Open Source Initiative c/o Lawrence Rosen, Esq.,
13   3001 King Ranch Road, Ukiah, CA 95482.   */
14
15#ifdef HAVE_CONFIG_H
16# include <config.h>
17#endif
18
19#include <assert.h>
20#include <dwarf.h>
21#include "libdwP.h"
22
23
24Dwarf_Abbrev *
25internal_function_def
26__libdw_getabbrev (dbg, cu, offset, lengthp, result)
27     Dwarf *dbg;
28     struct Dwarf_CU *cu;
29     Dwarf_Off offset;
30     size_t *lengthp;
31     Dwarf_Abbrev *result;
32{
33  /* Don't fail if there is not .debug_abbrev section.  */
34  if (dbg->sectiondata[IDX_debug_abbrev] == NULL)
35    return NULL;
36
37  if (offset >= dbg->sectiondata[IDX_debug_abbrev]->d_size)
38    {
39      __libdw_seterrno (DWARF_E_INVALID_OFFSET);
40      return NULL;
41    }
42
43  const unsigned char *abbrevp
44    = (unsigned char *) dbg->sectiondata[IDX_debug_abbrev]->d_buf + offset;
45
46  if (*abbrevp == '\0')
47    /* We are past the last entry.  */
48    return DWARF_END_ABBREV;
49
50  /* 7.5.3 Abbreviations Tables
51
52     [...] Each declaration begins with an unsigned LEB128 number
53     representing the abbreviation code itself.  [...]  The
54     abbreviation code is followed by another unsigned LEB128
55     number that encodes the entry's tag.  [...]
56
57     [...] Following the tag encoding is a 1-byte value that
58     determines whether a debugging information entry using this
59     abbreviation has child entries or not. [...]
60
61     [...] Finally, the child encoding is followed by a series of
62     attribute specifications. Each attribute specification
63     consists of two parts. The first part is an unsigned LEB128
64     number representing the attribute's name. The second part is
65     an unsigned LEB128 number representing the attribute's form.  */
66  const unsigned char *start_abbrevp = abbrevp;
67  unsigned int code;
68  get_uleb128 (code, abbrevp);
69
70  /* Check whether this code is already in the hash table.  */
71  bool foundit = false;
72  Dwarf_Abbrev *abb = NULL;
73  if (cu == NULL
74      || (abb = Dwarf_Abbrev_Hash_find (&cu->abbrev_hash, code, NULL)) == NULL)
75    {
76      if (result == NULL)
77	abb = libdw_typed_alloc (dbg, Dwarf_Abbrev);
78      else
79	abb = result;
80    }
81  else
82    {
83      foundit = true;
84
85      assert (abb->offset == offset);
86
87      /* If the caller doesn't need the length we are done.  */
88      if (lengthp == NULL)
89	goto out;
90    }
91
92  /* If there is already a value in the hash table we are going to
93     overwrite its content.  This must not be a problem, since the
94     content better be the same.  */
95  abb->code = code;
96  get_uleb128 (abb->tag, abbrevp);
97  abb->has_children = *abbrevp++ == DW_CHILDREN_yes;
98  abb->attrp = (unsigned char *) abbrevp;
99  abb->offset = offset;
100
101  /* Skip over all the attributes and count them while doing so.  */
102  abb->attrcnt = 0;
103  unsigned int attrname;
104  unsigned int attrform;
105  do
106    {
107      get_uleb128 (attrname, abbrevp);
108      get_uleb128 (attrform, abbrevp);
109    }
110  while (attrname != 0 && attrform != 0 && ++abb->attrcnt);
111
112  /* Return the length to the caller if she asked for it.  */
113  if (lengthp != NULL)
114    *lengthp = abbrevp - start_abbrevp;
115
116  /* Add the entry to the hash table.  */
117  if (cu != NULL && ! foundit)
118    (void) Dwarf_Abbrev_Hash_insert (&cu->abbrev_hash, abb->code, abb);
119
120 out:
121  return abb;
122}
123
124
125Dwarf_Abbrev *
126dwarf_getabbrev (die, offset, lengthp)
127     Dwarf_Die *die;
128     Dwarf_Off offset;
129     size_t *lengthp;
130{
131  return __libdw_getabbrev (die->cu->dbg, die->cu,
132			    die->cu->orig_abbrev_offset + offset, lengthp,
133			    NULL);
134}
135