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 (at) 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
