gdb/dwarf2/leb.h

   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 #endif /* GDB_DWARF2_LEB_H */