1 /* Advance to next CU header. 2 Copyright (C) 2002, 2003, 2004 Red Hat, Inc. 3 Written by Ulrich Drepper <drepper (at) redhat.com>, 2002. 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 <libdwP.h> 20 21 22 int 23 dwarf_nextcu (dwarf, off, next_off, header_sizep, abbrev_offsetp, 24 address_sizep, offset_sizep) 25 Dwarf *dwarf; 26 Dwarf_Off off; 27 Dwarf_Off *next_off; 28 size_t *header_sizep; 29 Dwarf_Off *abbrev_offsetp; 30 uint8_t *address_sizep; 31 uint8_t *offset_sizep; 32 { 33 /* Maybe there has been an error before. */ 34 if (dwarf == NULL) 35 return -1; 36 37 /* If we reached the end before don't do anything. */ 38 if (off == (Dwarf_Off) -1l 39 /* Make sure there is enough space in the .debug_info section 40 for at least the initial word. We cannot test the rest since 41 we don't know yet whether this is a 64-bit object or not. */ 42 || unlikely (off + 4 >= dwarf->sectiondata[IDX_debug_info]->d_size)) 43 { 44 *next_off = (Dwarf_Off) -1l; 45 return 1; 46 } 47 48 /* This points into the .debug_info section to the beginning of the 49 CU entry. */ 50 char *bytes = (char *) dwarf->sectiondata[IDX_debug_info]->d_buf + off; 51 52 /* The format of the CU header is described in dwarf2p1 7.5.1: 53 54 1. A 4-byte or 12-byte unsigned integer representing the length 55 of the .debug_info contribution for that compilation unit, not 56 including the length field itself. In the 32-bit DWARF format, 57 this is a 4-byte unsigned integer (which must be less than 58 0xffffff00); in the 64-bit DWARF format, this consists of the 59 4-byte value 0xffffffff followed by an 8-byte unsigned integer 60 that gives the actual length (see Section 7.4). 61 62 2. A 2-byte unsigned integer representing the version of the 63 DWARF information for that compilation unit. For DWARF Version 64 2.1, the value in this field is 2. 65 66 3. A 4-byte or 8-byte unsigned offset into the .debug_abbrev 67 section. This offset associates the compilation unit with a 68 particular set of debugging information entry abbreviations. In 69 the 32-bit DWARF format, this is a 4-byte unsigned length; in 70 the 64-bit DWARF format, this is an 8-byte unsigned length (see 71 Section 7.4). 72 73 4. A 1-byte unsigned integer representing the size in bytes of 74 an address on the target architecture. If the system uses 75 segmented addressing, this value represents the size of the 76 offset portion of an address. */ 77 uint64_t length = read_4ubyte_unaligned_inc (dwarf, bytes); 78 size_t offset_size = 4; 79 if (length == 0xffffffffu) 80 offset_size = 8; 81 82 /* Now we know how large the header is. Note the trick in the 83 computation. If the offset_size is 4 the '- 4' term undoes the 84 '2 *'. If offset_size is 8 this term computes the size of the 85 escape value plus the 8 byte offset. */ 86 if (unlikely (off + 2 * offset_size - 4 + sizeof (uint16_t) 87 + offset_size + sizeof (uint8_t) 88 >= dwarf->sectiondata[IDX_debug_info]->d_size)) 89 { 90 *next_off = -1; 91 return 1; 92 } 93 94 if (length == 0xffffffffu) 95 /* This is a 64-bit DWARF format. */ 96 length = read_8ubyte_unaligned_inc (dwarf, bytes); 97 98 /* Read the version stamp. Always a 16-bit value. 99 XXX Do we need the value? */ 100 read_2ubyte_unaligned_inc (dwarf, bytes); 101 102 /* Get offset in .debug_abbrev. Note that the size of the entry 103 depends on whether this is a 32-bit or 64-bit DWARF definition. */ 104 uint64_t abbrev_offset; 105 if (offset_size == 4) 106 abbrev_offset = read_4ubyte_unaligned_inc (dwarf, bytes); 107 else 108 abbrev_offset = read_8ubyte_unaligned_inc (dwarf, bytes); 109 if (abbrev_offsetp != NULL) 110 *abbrev_offsetp = abbrev_offset; 111 112 /* The address size. Always an 8-bit value. */ 113 uint8_t address_size = *bytes++; 114 if (address_sizep != NULL) 115 *address_sizep = address_size; 116 117 /* Store the offset size. */ 118 if (offset_sizep != NULL) 119 *offset_sizep = offset_size; 120 121 /* Store the header length. */ 122 if (header_sizep != NULL) 123 *header_sizep = (bytes 124 - ((char *) dwarf->sectiondata[IDX_debug_info]->d_buf 125 + off)); 126 127 /* See above for an explanation of the trick in this formula. */ 128 *next_off = off + 2 * offset_size - 4 + length; 129 130 return 0; 131 } 132
