| 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 */ |