1 /* Advance to next CU header.
2    Copyright (C) 2002-2010 Red Hat, Inc.
3    This file is part of elfutils.
4    Written by Ulrich Drepper <drepper@redhat.com>, 2002.
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 <dwarf.h>
36 
37 
38 int
39 dwarf_next_unit (Dwarf *dwarf, Dwarf_Off off, Dwarf_Off *next_off,
40 		 size_t *header_sizep, Dwarf_Half *versionp,
41 		 Dwarf_Off *abbrev_offsetp, uint8_t *address_sizep,
42 		 uint8_t *offset_sizep, uint64_t *type_signaturep,
43 		 Dwarf_Off *type_offsetp)
44 {
45   const bool debug_types = type_signaturep != NULL;
46   const size_t sec_idx = debug_types ? IDX_debug_types : IDX_debug_info;
47 
48   /* Maybe there has been an error before.  */
49   if (dwarf == NULL)
50     return -1;
51 
52   /* If we reached the end before don't do anything.  */
53   if (off == (Dwarf_Off) -1l
54       || unlikely (dwarf->sectiondata[sec_idx] == NULL)
55       /* Make sure there is enough space in the .debug_info section
56 	 for at least the initial word.  We cannot test the rest since
57 	 we don't know yet whether this is a 64-bit object or not.  */
58       || unlikely (off + 4 >= dwarf->sectiondata[sec_idx]->d_size))
59     {
60       *next_off = (Dwarf_Off) -1l;
61       return 1;
62     }
63 
64   /* This points into the .debug_info section to the beginning of the
65      CU entry.  */
66   const unsigned char *data = dwarf->sectiondata[sec_idx]->d_buf;
67   const unsigned char *bytes = data + off;
68 
69   /* The format of the CU header is described in dwarf2p1 7.5.1:
70 
71      1.  A 4-byte or 12-byte unsigned integer representing the length
72 	 of the .debug_info contribution for that compilation unit, not
73 	 including the length field itself. In the 32-bit DWARF format,
74 	 this is a 4-byte unsigned integer (which must be less than
75 	 0xfffffff0); in the 64-bit DWARF format, this consists of the
76 	 4-byte value 0xffffffff followed by an 8-byte unsigned integer
77 	 that gives the actual length (see Section 7.2.2).
78 
79       2. A 2-byte unsigned integer representing the version of the
80 	 DWARF information for that compilation unit. For DWARF Version
81 	 2.1, the value in this field is 2.
82 
83       3. A 4-byte or 8-byte unsigned offset into the .debug_abbrev
84 	 section. This offset associates the compilation unit with a
85 	 particular set of debugging information entry abbreviations. In
86 	 the 32-bit DWARF format, this is a 4-byte unsigned length; in
87 	 the 64-bit DWARF format, this is an 8-byte unsigned length (see
88 	 Section 7.4).
89 
90       4. A 1-byte unsigned integer representing the size in bytes of
91 	 an address on the target architecture. If the system uses
92 	 segmented addressing, this value represents the size of the
93 	 offset portion of an address.  */
94   uint64_t length = read_4ubyte_unaligned_inc (dwarf, bytes);
95   size_t offset_size = 4;
96   /* Lengths of 0xfffffff0 - 0xffffffff are escape codes.  Oxffffffff is
97      used to indicate that 64-bit dwarf information is being used, the
98      other values are currently reserved.  */
99   if (length == DWARF3_LENGTH_64_BIT)
100     offset_size = 8;
101   else if (unlikely (length >= DWARF3_LENGTH_MIN_ESCAPE_CODE
102 		     && length <= DWARF3_LENGTH_MAX_ESCAPE_CODE))
103     {
104     invalid:
105       __libdw_seterrno (DWARF_E_INVALID_DWARF);
106       return -1;
107     }
108 
109   /* Now we know how large the header is.  */
110   if (unlikely (DIE_OFFSET_FROM_CU_OFFSET (off, offset_size, debug_types)
111 		>= dwarf->sectiondata[sec_idx]->d_size))
112     {
113       *next_off = -1;
114       return 1;
115     }
116 
117   if (length == DWARF3_LENGTH_64_BIT)
118     /* This is a 64-bit DWARF format.  */
119     length = read_8ubyte_unaligned_inc (dwarf, bytes);
120 
121   /* Read the version stamp.  Always a 16-bit value.  */
122   uint_fast16_t version = read_2ubyte_unaligned_inc (dwarf, bytes);
123 
124   /* Get offset in .debug_abbrev.  Note that the size of the entry
125      depends on whether this is a 32-bit or 64-bit DWARF definition.  */
126   uint64_t abbrev_offset;
127   if (__libdw_read_offset_inc (dwarf, sec_idx, &bytes, offset_size,
128 			       &abbrev_offset, IDX_debug_abbrev, 0))
129     return -1;
130 
131   /* The address size.  Always an 8-bit value.  */
132   uint8_t address_size = *bytes++;
133 
134   if (debug_types)
135     {
136       uint64_t type_sig8 = read_8ubyte_unaligned_inc (dwarf, bytes);
137 
138       Dwarf_Off type_offset;
139       if (__libdw_read_offset_inc (dwarf, sec_idx, &bytes, offset_size,
140 				   &type_offset, sec_idx, 0))
141 	return -1;
142 
143       /* Validate that the TYPE_OFFSET points past the header.  */
144       if (unlikely (type_offset < (size_t) (bytes - (data + off))))
145 	goto invalid;
146 
147       *type_signaturep = type_sig8;
148       if (type_offsetp != NULL)
149 	*type_offsetp = type_offset;
150     }
151 
152   /* Store the header length.  */
153   if (header_sizep != NULL)
154     *header_sizep = bytes - (data + off);
155 
156   if (versionp != NULL)
157     *versionp = version;
158 
159   if (abbrev_offsetp != NULL)
160     *abbrev_offsetp = abbrev_offset;
161 
162   if (address_sizep != NULL)
163     *address_sizep = address_size;
164 
165   /* Store the offset size.  */
166   if (offset_sizep != NULL)
167     *offset_sizep = offset_size;
168 
169   /* See definition of DIE_OFFSET_FROM_CU_OFFSET macro
170      for an explanation of the trick in this expression.  */
171   *next_off = off + 2 * offset_size - 4 + length;
172 
173   return 0;
174 }
175 INTDEF(dwarf_next_unit)
176 
177 int
178 dwarf_nextcu (Dwarf *dwarf, Dwarf_Off off, Dwarf_Off *next_off,
179 	      size_t *header_sizep, Dwarf_Off *abbrev_offsetp,
180 	      uint8_t *address_sizep, uint8_t *offset_sizep)
181 {
182   return INTUSE(dwarf_next_unit) (dwarf, off, next_off, header_sizep, NULL,
183 				  abbrev_offsetp, address_sizep, offset_sizep,
184 				  NULL, NULL);
185 }
186 INTDEF(dwarf_nextcu)
187