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 #include "libunwind_i.h" 31 32 /* This header file defines the format of a DWARF exception-header 33 section (.eh_frame_hdr, pointed to by program-header 34 PT_GNU_EH_FRAME). The exception-header is self-describing in the 35 sense that the format of the addresses contained in it is expressed 36 as a one-byte type-descriptor called a "pointer-encoding" (PE). 37 38 The exception header encodes the address of the .eh_frame section 39 and optionally contains a binary search table for the 40 Frame Descriptor Entries (FDEs) in the .eh_frame. The contents of 41 .eh_frame has the format described by the DWARF v3 standard 42 (http://www.eagercon.com/dwarf/dwarf3std.htm), except that code 43 addresses may be encoded in different ways. Also, .eh_frame has 44 augmentations that allow encoding a language-specific data-area 45 (LSDA) pointer and a pointer to a personality-routine. 46 47 Details: 48 49 The Common Information Entry (CIE) associated with an FDE may 50 contain an augmentation string. Each character in this string has 51 a specific meaning and either one or two associated operands. The 52 operands are stored in an augmentation body which appears right 53 after the "return_address_register" member and before the 54 "initial_instructions" member. The operands appear in the order 55 in which the characters appear in the string. For example, if the 56 augmentation string is "zL", the operand for 'z' would be first in 57 the augmentation body and the operand for 'L' would be second. 58 The following characters are supported for the CIE augmentation 59 string: 60 61 'z': The operand for this character is a uleb128 value that gives the 62 length of the CIE augmentation body, not counting the length 63 of the uleb128 operand itself. If present, this code must 64 appear as the first character in the augmentation body. 65 66 'L': Indicates that the FDE's augmentation body contains an LSDA 67 pointer. The operand for this character is a single byte 68 that specifies the pointer-encoding (PE) that is used for 69 the LSDA pointer. 70 71 'R': Indicates that the code-pointers (FDE members 72 "initial_location" and "address_range" and the operand for 73 DW_CFA_set_loc) in the FDE have a non-default encoding. The 74 operand for this character is a single byte that specifies 75 the pointer-encoding (PE) that is used for the 76 code-pointers. Note: the "address_range" member is always 77 encoded as an absolute value. Apart from that, the specified 78 FDE pointer-encoding applies. 79 80 'P': Indicates the presence of a personality routine (handler). 81 The first operand for this character specifies the 82 pointer-encoding (PE) that is used for the second operand, 83 which specifies the address of the personality routine. 84 85 If the augmentation string contains any other characters, the 86 remainder of the augmentation string should be ignored. 87 Furthermore, if the size of the augmentation body is unknown 88 (i.e., 'z' is not the first character of the augmentation string), 89 then the entire CIE as well all associated FDEs must be ignored. 90 91 A Frame Descriptor Entries (FDE) may contain an augmentation body 92 which, if present, appears right after the "address_range" member 93 and before the "instructions" member. The contents of this body 94 is implicitly defined by the augmentation string of the associated 95 CIE. The meaning of the characters in the CIE's augmentation 96 string as far as FDEs are concerned is as follows: 97 98 'z': The first operand in the FDE's augmentation body specifies 99 the total length of the augmentation body as a uleb128 (not 100 counting the length of the uleb128 operand itself). 101 102 'L': The operand for this character is an LSDA pointer, encoded 103 in the format specified by the corresponding operand in the 104 CIE's augmentation body. 105 106 */ 107 108 #define DW_EH_VERSION 1 /* The version we're implementing */ 109 110 struct __attribute__((packed)) dwarf_eh_frame_hdr 111 { 112 unsigned char version; 113 unsigned char eh_frame_ptr_enc; 114 unsigned char fde_count_enc; 115 unsigned char table_enc; 116 Elf_W (Addr) eh_frame; 117 /* The rest of the header is variable-length and consists of the 118 following members: 119 120 encoded_t fde_count; 121 struct 122 { 123 encoded_t start_ip; // first address covered by this FDE 124 encoded_t fde_addr; // address of the FDE 125 } 126 binary_search_table[fde_count]; */ 127 }; 128 129 #endif /* dwarf_eh_h */ 130