1 /* Return child of current DIE.
2 Copyright (C) 2003-2011, 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 "libdwP.h"
35 #include <string.h>
36
37 /* Some arbitrary value not conflicting with any existing code. */
38 #define INVALID 0xffffe444
39
40
41 unsigned char *
42 internal_function
__libdw_find_attr(Dwarf_Die * die,unsigned int search_name,unsigned int * codep,unsigned int * formp)43 __libdw_find_attr (Dwarf_Die *die, unsigned int search_name,
44 unsigned int *codep, unsigned int *formp)
45 {
46 const unsigned char *readp = NULL;
47
48 /* Find the abbreviation entry. */
49 Dwarf_Abbrev *abbrevp = __libdw_dieabbrev (die, &readp);
50 if (unlikely (abbrevp == DWARF_END_ABBREV))
51 {
52 __libdw_seterrno (DWARF_E_INVALID_DWARF);
53 return NULL;
54 }
55
56 /* Search the name attribute. Attribute has been checked when
57 Dwarf_Abbrev was created, we can read unchecked. */
58 const unsigned char *attrp = abbrevp->attrp;
59 while (1)
60 {
61 /* Get attribute name and form. */
62 unsigned int attr_name;
63 get_uleb128_unchecked (attr_name, attrp);
64
65 unsigned int attr_form;
66 get_uleb128_unchecked (attr_form, attrp);
67
68 /* We can stop if we found the attribute with value zero. */
69 if (attr_name == 0 && attr_form == 0)
70 break;
71
72 /* Is this the name attribute? */
73 if (attr_name == search_name && search_name != INVALID)
74 {
75 if (codep != NULL)
76 *codep = attr_name;
77 if (formp != NULL)
78 *formp = attr_form;
79
80 /* Normally the attribute data comes from the DIE/info,
81 except for implicit_form, where it comes from the abbrev. */
82 if (attr_form == DW_FORM_implicit_const)
83 return (unsigned char *) attrp;
84 else
85 return (unsigned char *) readp;
86 }
87
88 /* Skip over the rest of this attribute (if there is any). */
89 if (attr_form != 0)
90 {
91 size_t len = __libdw_form_val_len (die->cu, attr_form, readp);
92 if (unlikely (len == (size_t) -1l))
93 {
94 readp = NULL;
95 break;
96 }
97
98 // __libdw_form_val_len will have done a bounds check.
99 readp += len;
100
101 // If the value is in the abbrev data, skip it.
102 if (attr_form == DW_FORM_implicit_const)
103 {
104 int64_t attr_value __attribute__((__unused__));
105 get_sleb128_unchecked (attr_value, attrp);
106 }
107 }
108 }
109
110 // XXX Do we need other values?
111 if (codep != NULL)
112 *codep = INVALID;
113 if (formp != NULL)
114 *formp = INVALID;
115
116 return (unsigned char *) readp;
117 }
118
119
120 int
dwarf_child(Dwarf_Die * die,Dwarf_Die * result)121 dwarf_child (Dwarf_Die *die, Dwarf_Die *result)
122 {
123 /* Ignore previous errors. */
124 if (die == NULL)
125 return -1;
126
127 /* Find the abbreviation entry. */
128 Dwarf_Abbrev *abbrevp = __libdw_dieabbrev (die, NULL);
129 if (unlikely (abbrevp == DWARF_END_ABBREV))
130 {
131 __libdw_seterrno (DWARF_E_INVALID_DWARF);
132 return -1;
133 }
134
135 /* If there are no children, do not search. */
136 if (! abbrevp->has_children)
137 return 1;
138
139 /* Skip past the last attribute. */
140 void *addr = __libdw_find_attr (die, INVALID, NULL, NULL);
141
142 if (addr == NULL)
143 return -1;
144
145 /* RESULT can be the same as DIE. So preserve what we need. */
146 struct Dwarf_CU *cu = die->cu;
147
148 /* It's kosher (just suboptimal) to have a null entry first thing (7.5.3).
149 So if this starts with ULEB128 of 0 (even with silly encoding of 0),
150 it is a kosher null entry and we do not really have any children. */
151 const unsigned char *code = addr;
152 const unsigned char *endp = cu->endp;
153 while (1)
154 {
155 if (unlikely (code >= endp)) /* Truncated section. */
156 return 1;
157 if (unlikely (*code == 0x80))
158 ++code;
159 else
160 break;
161 }
162 if (unlikely (*code == '\0'))
163 return 1;
164
165 /* Clear the entire DIE structure. This signals we have not yet
166 determined any of the information. */
167 memset (result, '\0', sizeof (Dwarf_Die));
168
169 /* We have the address. */
170 result->addr = addr;
171
172 /* Same CU as the parent. */
173 result->cu = cu;
174
175 return 0;
176 }
177 INTDEF(dwarf_child)
178