headers/libs/libunwind/dwarf-eh.h

   1 /* libunwind - a platform-independent unwind library
   2    Copyright (c) 2003 Hewlett-Packard Development Company, L.P.
   3         Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
   4
   5 This file is part of libunwind.
   6
   7 Permission is hereby granted, free of charge, to any person obtaining
   8 a copy of this software and associated documentation files (the
   9 "Software"), to deal in the Software without restriction, including
  10 without limitation the rights to use, copy, modify, merge, publish,
  11 distribute, sublicense, and/or sell copies of the Software, and to
  12 permit persons to whom the Software is furnished to do so, subject to
  13 the following conditions:
  14
  15 The above copyright notice and this permission notice shall be
  16 included in all copies or substantial portions of the Software.
  17
  18 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  19 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  20 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  21 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  22 LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  23 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  24 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
  25
  26 #ifndef dwarf_eh_h
  27 #define dwarf_eh_h
  28
  29 #include "dwarf.h"
  30
  31 /* This header file defines the format of a DWARF exception-header
  32    section (.eh_frame_hdr, pointed to by program-header
  33    PT_GNU_EH_FRAME).  The exception-header is self-describing in the
  34    sense that the format of the addresses contained in it is expressed
  35    as a one-byte type-descriptor called a "pointer-encoding" (PE).
  36
  37    The exception header encodes the address of the .eh_frame section
  38    and optionally contains a binary search table for the
  39    Frame Descriptor Entries (FDEs) in the .eh_frame.  The contents of
  40    .eh_frame has the format described by the DWARF v3 standard
  41    (http://www.eagercon.com/dwarf/dwarf3std.htm), except that code
  42    addresses may be encoded in different ways.  Also, .eh_frame has
  43    augmentations that allow encoding a language-specific data-area
  44    (LSDA) pointer and a pointer to a personality-routine.
  45
  46    Details:
  47
  48     The Common Information Entry (CIE) associated with an FDE may
  49     contain an augmentation string.  Each character in this string has
  50     a specific meaning and either one or two associated operands.  The
  51     operands are stored in an augmentation body which appears right
  52     after the "return_address_register" member and before the
  53     "initial_instructions" member.  The operands appear in the order
  54     in which the characters appear in the string.  For example, if the
  55     augmentation string is "zL", the operand for 'z' would be first in
  56     the augmentation body and the operand for 'L' would be second.
  57     The following characters are supported for the CIE augmentation
  58     string:
  59
  60      'z': The operand for this character is a uleb128 value that gives the
  61           length of the CIE augmentation body, not counting the length
  62           of the uleb128 operand itself.  If present, this code must
  63           appear as the first character in the augmentation body.
  64
  65      'L': Indicates that the FDE's augmentation body contains an LSDA
  66           pointer.  The operand for this character is a single byte
  67           that specifies the pointer-encoding (PE) that is used for
  68           the LSDA pointer.
  69
  70      'R': Indicates that the code-pointers (FDE members
  71           "initial_location" and "address_range" and the operand for
  72           DW_CFA_set_loc) in the FDE have a non-default encoding.  The
  73           operand for this character is a single byte that specifies
  74           the pointer-encoding (PE) that is used for the
  75           code-pointers.  Note: the "address_range" member is always
  76           encoded as an absolute value.  Apart from that, the specified
  77           FDE pointer-encoding applies.
  78
  79      'P': Indicates the presence of a personality routine (handler).
  80           The first operand for this character specifies the
  81           pointer-encoding (PE) that is used for the second operand,
  82           which specifies the address of the personality routine.
  83
  84     If the augmentation string contains any other characters, the
  85     remainder of the augmentation string should be ignored.
  86     Furthermore, if the size of the augmentation body is unknown
  87     (i.e., 'z' is not the first character of the augmentation string),
  88     then the entire CIE as well all associated FDEs must be ignored.
  89
  90     A Frame Descriptor Entries (FDE) may contain an augmentation body
  91     which, if present, appears right after the "address_range" member
  92     and before the "instructions" member.  The contents of this body
  93     is implicitly defined by the augmentation string of the associated
  94     CIE.  The meaning of the characters in the CIE's augmentation
  95     string as far as FDEs are concerned is as follows:
  96
  97      'z': The first operand in the FDE's augmentation body specifies
  98           the total length of the augmentation body as a uleb128 (not
  99           counting the length of the uleb128 operand itself).
 100
 101      'L': The operand for this character is an LSDA pointer, encoded
 102           in the format specified by the corresponding operand in the
 103           CIE's augmentation body.
 104
 105 */
 106
 107 #define DW_EH_VERSION           1       /* The version we're implementing */
 108
 109 struct dwarf_eh_frame_hdr
 110   {
 111     unsigned char version;
 112     unsigned char eh_frame_ptr_enc;
 113     unsigned char fde_count_enc;
 114     unsigned char table_enc;
 115     /* The rest of the header is variable-length and consists of the
 116        following members:
 117
 118         encoded_t eh_frame_ptr;
 119         encoded_t fde_count;
 120         struct
 121           {
 122             encoded_t start_ip; // first address covered by this FDE
 123             encoded_t fde_addr; // address of the FDE
 124           }
 125         binary_search_table[fde_count];  */
 126   };
 127
 128 #endif /* dwarf_eh_h */