1 /* Low-level DWARF 2 reading code 2 3 Copyright (C) 1994-2020 Free Software Foundation, Inc. 4 5 Adapted by Gary Funck (gary@intrepid.com), Intrepid Technology, 6 Inc. with support from Florida State University (under contract 7 with the Ada Joint Program Office), and Silicon Graphics, Inc. 8 Initial contribution by Brent Benson, Harris Computer Systems, Inc., 9 based on Fred Fish's (Cygnus Support) implementation of DWARF 1 10 support. 11 12 This file is part of GDB. 13 14 This program is free software; you can redistribute it and/or modify 15 it under the terms of the GNU General Public License as published by 16 the Free Software Foundation; either version 3 of the License, or 17 (at your option) any later version. 18 19 This program is distributed in the hope that it will be useful, 20 but WITHOUT ANY WARRANTY; without even the implied warranty of 21 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 22 GNU General Public License for more details. 23 24 You should have received a copy of the GNU General Public License 25 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 26 27 #ifndef GDB_DWARF2_LEB_H 28 #define GDB_DWARF2_LEB_H 29 30 /* Read dwarf information from a buffer. */ 31 32 static inline unsigned int 33 read_1_byte (bfd *abfd, const gdb_byte *buf) 34 { 35 return bfd_get_8 (abfd, buf); 36 } 37 38 static inline int 39 read_1_signed_byte (bfd *abfd, const gdb_byte *buf) 40 { 41 return bfd_get_signed_8 (abfd, buf); 42 } 43 44 static inline unsigned int 45 read_2_bytes (bfd *abfd, const gdb_byte *buf) 46 { 47 return bfd_get_16 (abfd, buf); 48 } 49 50 static inline int 51 read_2_signed_bytes (bfd *abfd, const gdb_byte *buf) 52 { 53 return bfd_get_signed_16 (abfd, buf); 54 } 55 56 /* Read the next three bytes (little-endian order) as an unsigned integer. */ 57 static inline unsigned int 58 read_3_bytes (bfd *abfd, const gdb_byte *buf) 59 { 60 unsigned int result = 0; 61 for (int i = 0; i < 3; ++i) 62 { 63 unsigned char byte = bfd_get_8 (abfd, buf); 64 buf++; 65 result |= ((unsigned int) byte << (i * 8)); 66 } 67 return result; 68 } 69 70 static inline unsigned int 71 read_4_bytes (bfd *abfd, const gdb_byte *buf) 72 { 73 return bfd_get_32 (abfd, buf); 74 } 75 76 static inline int 77 read_4_signed_bytes (bfd *abfd, const gdb_byte *buf) 78 { 79 return bfd_get_signed_32 (abfd, buf); 80 } 81 82 static inline ULONGEST 83 read_8_bytes (bfd *abfd, const gdb_byte *buf) 84 { 85 return bfd_get_64 (abfd, buf); 86 } 87 88 extern LONGEST read_signed_leb128 (bfd *, const gdb_byte *, unsigned int *); 89 90 extern ULONGEST read_unsigned_leb128 (bfd *, const gdb_byte *, unsigned int *); 91 92 /* Read the initial length from a section. The (draft) DWARF 3 93 specification allows the initial length to take up either 4 bytes 94 or 12 bytes. If the first 4 bytes are 0xffffffff, then the next 8 95 bytes describe the length and all offsets will be 8 bytes in length 96 instead of 4. 97 98 An older, non-standard 64-bit format is also handled by this 99 function. The older format in question stores the initial length 100 as an 8-byte quantity without an escape value. Lengths greater 101 than 2^32 aren't very common which means that the initial 4 bytes 102 is almost always zero. Since a length value of zero doesn't make 103 sense for the 32-bit format, this initial zero can be considered to 104 be an escape value which indicates the presence of the older 64-bit 105 format. As written, the code can't detect (old format) lengths 106 greater than 4GB. If it becomes necessary to handle lengths 107 somewhat larger than 4GB, we could allow other small values (such 108 as the non-sensical values of 1, 2, and 3) to also be used as 109 escape values indicating the presence of the old format. 110 111 The value returned via bytes_read should be used to increment the 112 relevant pointer after calling read_initial_length(). 113 114 [ Note: read_initial_length() and read_offset() are based on the 115 document entitled "DWARF Debugging Information Format", revision 116 3, draft 8, dated November 19, 2001. This document was obtained 117 from: 118 119 http://reality.sgiweb.org/davea/dwarf3-draft8-011125.pdf 120 121 This document is only a draft and is subject to change. (So beware.) 122 123 Details regarding the older, non-standard 64-bit format were 124 determined empirically by examining 64-bit ELF files produced by 125 the SGI toolchain on an IRIX 6.5 machine. 126 127 - Kevin, July 16, 2002 128 ] */ 129 extern LONGEST read_initial_length (bfd *abfd, const gdb_byte *buf, 130 unsigned int *bytes_read, 131 bool handle_nonstd = true); 132 133 /* Read an offset from the data stream. */ 134 extern LONGEST read_offset (bfd *abfd, const gdb_byte *buf, 135 unsigned int offset_size); 136 137 static inline const gdb_byte * 138 read_n_bytes (bfd *abfd, const gdb_byte *buf, unsigned int size) 139 { 140 /* If the size of a host char is 8 bits, we can return a pointer 141 to the buffer, otherwise we have to copy the data to a buffer 142 allocated on the temporary obstack. */ 143 gdb_assert (HOST_CHAR_BIT == 8); 144 return buf; 145 } 146 147 static inline const char * 148 read_direct_string (bfd *abfd, const gdb_byte *buf, 149 unsigned int *bytes_read_ptr) 150 { 151 /* If the size of a host char is 8 bits, we can return a pointer 152 to the string, otherwise we have to copy the string to a buffer 153 allocated on the temporary obstack. */ 154 gdb_assert (HOST_CHAR_BIT == 8); 155 if (*buf == '\0') 156 { 157 *bytes_read_ptr = 1; 158 return NULL; 159 } 160 *bytes_read_ptr = strlen ((const char *) buf) + 1; 161 return (const char *) buf; 162 } 163 164 #endif /* GDB_DWARF2_LEB_H */ 165