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1 /* Get abbreviation at given offset.
2    Copyright (C) 2003, 2004, 2005, 2006, 2014, 2017 Red Hat, Inc.
3    This file is part of elfutils.
4    Written by Ulrich Drepper <drepper@redhat.com>, 2003.
5 
6    This file is free software; you can redistribute it and/or modify
7    it under the terms of either
8 
9      * the GNU Lesser General Public License as published by the Free
10        Software Foundation; either version 3 of the License, or (at
11        your option) any later version
12 
13    or
14 
15      * the GNU General Public License as published by the Free
16        Software Foundation; either version 2 of the License, or (at
17        your option) any later version
18 
19    or both in parallel, as here.
20 
21    elfutils is distributed in the hope that it will be useful, but
22    WITHOUT ANY WARRANTY; without even the implied warranty of
23    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
24    General Public License for more details.
25 
26    You should have received copies of the GNU General Public License and
27    the GNU Lesser General Public License along with this program.  If
28    not, see <http://www.gnu.org/licenses/>.  */
29 
30 #ifdef HAVE_CONFIG_H
31 # include <config.h>
32 #endif
33 
34 #include <dwarf.h>
35 #include "libdwP.h"
36 
37 
38 Dwarf_Abbrev *
39 internal_function
__libdw_getabbrev(Dwarf * dbg,struct Dwarf_CU * cu,Dwarf_Off offset,size_t * lengthp,Dwarf_Abbrev * result)40 __libdw_getabbrev (Dwarf *dbg, struct Dwarf_CU *cu, Dwarf_Off offset,
41 		   size_t *lengthp, Dwarf_Abbrev *result)
42 {
43   /* Don't fail if there is not .debug_abbrev section.  */
44   if (dbg->sectiondata[IDX_debug_abbrev] == NULL)
45     return NULL;
46 
47   if (offset >= dbg->sectiondata[IDX_debug_abbrev]->d_size)
48     {
49       __libdw_seterrno (DWARF_E_INVALID_OFFSET);
50       return NULL;
51     }
52 
53   const unsigned char *abbrevp
54     = (unsigned char *) dbg->sectiondata[IDX_debug_abbrev]->d_buf + offset;
55 
56   if (*abbrevp == '\0')
57     /* We are past the last entry.  */
58     return DWARF_END_ABBREV;
59 
60   /* 7.5.3 Abbreviations Tables
61 
62      [...] Each declaration begins with an unsigned LEB128 number
63      representing the abbreviation code itself.  [...]  The
64      abbreviation code is followed by another unsigned LEB128
65      number that encodes the entry's tag.  [...]
66 
67      [...] Following the tag encoding is a 1-byte value that
68      determines whether a debugging information entry using this
69      abbreviation has child entries or not. [...]
70 
71      [...] Finally, the child encoding is followed by a series of
72      attribute specifications. Each attribute specification
73      consists of two parts. The first part is an unsigned LEB128
74      number representing the attribute's name. The second part is
75      an unsigned LEB128 number representing the attribute's form.  */
76   const unsigned char *end = (dbg->sectiondata[IDX_debug_abbrev]->d_buf
77 			      + dbg->sectiondata[IDX_debug_abbrev]->d_size);
78   const unsigned char *start_abbrevp = abbrevp;
79   unsigned int code;
80   get_uleb128 (code, abbrevp, end);
81 
82   /* Check whether this code is already in the hash table.  */
83   bool foundit = false;
84   Dwarf_Abbrev *abb = NULL;
85   if (cu == NULL
86       || (abb = Dwarf_Abbrev_Hash_find (&cu->abbrev_hash, code, NULL)) == NULL)
87     {
88       if (result == NULL)
89 	abb = libdw_typed_alloc (dbg, Dwarf_Abbrev);
90       else
91 	abb = result;
92     }
93   else
94     {
95       foundit = true;
96 
97       if (unlikely (abb->offset != offset))
98 	{
99 	  /* A duplicate abbrev code at a different offset,
100 	     that should never happen.  */
101 	invalid:
102 	  __libdw_seterrno (DWARF_E_INVALID_DWARF);
103 	  return NULL;
104 	}
105 
106       /* If the caller doesn't need the length we are done.  */
107       if (lengthp == NULL)
108 	goto out;
109     }
110 
111   /* If there is already a value in the hash table we are going to
112      overwrite its content.  This must not be a problem, since the
113      content better be the same.  */
114   abb->code = code;
115   if (abbrevp >= end)
116     goto invalid;
117   get_uleb128 (abb->tag, abbrevp, end);
118   if (abbrevp + 1 >= end)
119     goto invalid;
120   abb->has_children = *abbrevp++ == DW_CHILDREN_yes;
121   abb->attrp = (unsigned char *) abbrevp;
122   abb->offset = offset;
123 
124   /* Skip over all the attributes and check rest of the abbrev is valid.  */
125   unsigned int attrname;
126   unsigned int attrform;
127   do
128     {
129       if (abbrevp >= end)
130 	goto invalid;
131       get_uleb128 (attrname, abbrevp, end);
132       if (abbrevp >= end)
133 	goto invalid;
134       get_uleb128 (attrform, abbrevp, end);
135       if (attrform == DW_FORM_implicit_const)
136 	{
137 	  int64_t formval __attribute__((__unused__));
138 	  if (abbrevp >= end)
139 	    goto invalid;
140 	  get_sleb128 (formval, abbrevp, end);
141 	}
142     }
143   while (attrname != 0 || attrform != 0);
144 
145   /* Return the length to the caller if she asked for it.  */
146   if (lengthp != NULL)
147     *lengthp = abbrevp - start_abbrevp;
148 
149   /* Add the entry to the hash table.  */
150   if (cu != NULL && ! foundit)
151     (void) Dwarf_Abbrev_Hash_insert (&cu->abbrev_hash, abb->code, abb);
152 
153  out:
154   return abb;
155 }
156 
157 
158 Dwarf_Abbrev *
dwarf_getabbrev(Dwarf_Die * die,Dwarf_Off offset,size_t * lengthp)159 dwarf_getabbrev (Dwarf_Die *die, Dwarf_Off offset, size_t *lengthp)
160 {
161   if (die == NULL || die->cu == NULL)
162     return NULL;
163 
164   Dwarf_CU *cu = die->cu;
165   Dwarf *dbg = cu->dbg;
166   Dwarf_Off abbrev_offset = cu->orig_abbrev_offset;
167   Elf_Data *data = dbg->sectiondata[IDX_debug_abbrev];
168   if (data == NULL)
169     return NULL;
170 
171   if (offset >= data->d_size - abbrev_offset)
172     {
173       __libdw_seterrno (DWARF_E_INVALID_OFFSET);
174       return NULL;
175     }
176 
177   return __libdw_getabbrev (dbg, cu, abbrev_offset + offset, lengthp, NULL);
178 }
179