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1 /* Copyright (C) 2001, 2002, 2003, 2004, 2005, 2009 Free Software Foundation, Inc.
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2 Contributed by Jakub Jelinek <jakub@redhat.com>.
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3
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4 This file is part of GCC.
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5
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6 GCC is free software; you can redistribute it and/or modify
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7 it under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 3, or (at your option)
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9 any later version.
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10
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11 GCC is distributed in the hope that it will be useful,
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 GNU General Public License for more details.
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15
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16 Under Section 7 of GPL version 3, you are granted additional
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17 permissions described in the GCC Runtime Library Exception, version
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18 3.1, as published by the Free Software Foundation.
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19
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20 You should have received a copy of the GNU General Public License and
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21 a copy of the GCC Runtime Library Exception along with this program;
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22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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23 <http://www.gnu.org/licenses/>. */
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24
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25 /* Locate the FDE entry for a given address, using PT_GNU_EH_FRAME ELF
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26 segment and dl_iterate_phdr to avoid register/deregister calls at
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27 DSO load/unload. */
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28
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29 #ifndef _GNU_SOURCE
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30 #define _GNU_SOURCE 1
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31 #endif
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32
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33 #include "tconfig.h"
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34 #include "tsystem.h"
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35 #ifndef inhibit_libc
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36 #include <link.h>
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37 #endif
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38 #include "coretypes.h"
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39 #include "tm.h"
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40 #include "dwarf2.h"
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41 #include "unwind.h"
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42 #define NO_BASE_OF_ENCODED_VALUE
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43 #include "unwind-pe.h"
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44 #include "unwind-dw2-fde.h"
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45 #include "unwind-compat.h"
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46 #include "gthr.h"
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47
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48 #if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \
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49 && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ > 2) \
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50 || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 2 && defined(DT_CONFIG)))
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51
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52 #ifndef __RELOC_POINTER
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53 # define __RELOC_POINTER(ptr, base) ((ptr) + (base))
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54 #endif
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55
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56 static const fde * _Unwind_Find_registered_FDE (void *pc, struct dwarf_eh_bases *bases);
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57
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58 #define _Unwind_Find_FDE _Unwind_Find_registered_FDE
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59 #include "unwind-dw2-fde.c"
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60 #undef _Unwind_Find_FDE
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61
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62 #ifndef PT_GNU_EH_FRAME
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63 #define PT_GNU_EH_FRAME (PT_LOOS + 0x474e550)
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64 #endif
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65
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66 struct unw_eh_callback_data
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67 {
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68 _Unwind_Ptr pc;
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69 void *tbase;
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70 void *dbase;
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71 void *func;
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72 const fde *ret;
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73 int check_cache;
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74 };
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75
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76 struct unw_eh_frame_hdr
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77 {
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78 unsigned char version;
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79 unsigned char eh_frame_ptr_enc;
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80 unsigned char fde_count_enc;
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81 unsigned char table_enc;
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82 };
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83
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84 #define FRAME_HDR_CACHE_SIZE 8
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85
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86 static struct frame_hdr_cache_element
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87 {
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88 _Unwind_Ptr pc_low;
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89 _Unwind_Ptr pc_high;
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90 _Unwind_Ptr load_base;
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91 const ElfW(Phdr) *p_eh_frame_hdr;
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92 const ElfW(Phdr) *p_dynamic;
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93 struct frame_hdr_cache_element *link;
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94 } frame_hdr_cache[FRAME_HDR_CACHE_SIZE];
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95
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96 static struct frame_hdr_cache_element *frame_hdr_cache_head;
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97
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98 /* Like base_of_encoded_value, but take the base from a struct
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99 unw_eh_callback_data instead of an _Unwind_Context. */
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100
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101 static _Unwind_Ptr
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102 base_from_cb_data (unsigned char encoding, struct unw_eh_callback_data *data)
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103 {
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104 if (encoding == DW_EH_PE_omit)
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105 return 0;
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106
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107 switch (encoding & 0x70)
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108 {
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109 case DW_EH_PE_absptr:
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110 case DW_EH_PE_pcrel:
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111 case DW_EH_PE_aligned:
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112 return 0;
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113
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114 case DW_EH_PE_textrel:
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115 return (_Unwind_Ptr) data->tbase;
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116 case DW_EH_PE_datarel:
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117 return (_Unwind_Ptr) data->dbase;
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118 default:
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119 gcc_unreachable ();
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120 }
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121 }
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122
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123 static int
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124 _Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr)
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125 {
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126 struct unw_eh_callback_data *data = (struct unw_eh_callback_data *) ptr;
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127 const ElfW(Phdr) *phdr, *p_eh_frame_hdr, *p_dynamic;
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128 long n, match;
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129 #ifdef __FRV_FDPIC__
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130 struct elf32_fdpic_loadaddr load_base;
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131 #else
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132 _Unwind_Ptr load_base;
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133 #endif
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134 const unsigned char *p;
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135 const struct unw_eh_frame_hdr *hdr;
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136 _Unwind_Ptr eh_frame;
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137 struct object ob;
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138
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139 struct ext_dl_phdr_info
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140 {
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141 ElfW(Addr) dlpi_addr;
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142 const char *dlpi_name;
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143 const ElfW(Phdr) *dlpi_phdr;
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144 ElfW(Half) dlpi_phnum;
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145 unsigned long long int dlpi_adds;
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146 unsigned long long int dlpi_subs;
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147 };
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148
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149 match = 0;
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150 phdr = info->dlpi_phdr;
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151 load_base = info->dlpi_addr;
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152 p_eh_frame_hdr = NULL;
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153 p_dynamic = NULL;
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154
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155 struct frame_hdr_cache_element *prev_cache_entry = NULL,
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156 *last_cache_entry = NULL;
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157
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158 if (data->check_cache && size >= sizeof (struct ext_dl_phdr_info))
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159 {
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160 static unsigned long long adds = -1ULL, subs;
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161 struct ext_dl_phdr_info *einfo = (struct ext_dl_phdr_info *) info;
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162
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163 /* We use a least recently used cache replacement policy. Also,
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164 the most recently used cache entries are placed at the head
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165 of the search chain. */
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166
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167 if (einfo->dlpi_adds == adds && einfo->dlpi_subs == subs)
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168 {
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169 /* Find data->pc in shared library cache.
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170 Set load_base, p_eh_frame_hdr and p_dynamic
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171 plus match from the cache and goto
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172 "Read .eh_frame_hdr header." below. */
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173
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174 struct frame_hdr_cache_element *cache_entry;
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175
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176 for (cache_entry = frame_hdr_cache_head;
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177 cache_entry;
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178 cache_entry = cache_entry->link)
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179 {
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180 if (data->pc >= cache_entry->pc_low
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181 && data->pc < cache_entry->pc_high)
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182 {
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183 load_base = cache_entry->load_base;
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184 p_eh_frame_hdr = cache_entry->p_eh_frame_hdr;
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185 p_dynamic = cache_entry->p_dynamic;
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186
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187 /* And move the entry we're using to the head. */
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188 if (cache_entry != frame_hdr_cache_head)
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189 {
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190 prev_cache_entry->link = cache_entry->link;
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191 cache_entry->link = frame_hdr_cache_head;
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192 frame_hdr_cache_head = cache_entry;
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193 }
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194 goto found;
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195 }
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196
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197 last_cache_entry = cache_entry;
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198 /* Exit early if we found an unused entry. */
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199 if ((cache_entry->pc_low | cache_entry->pc_high) == 0)
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200 break;
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201 if (cache_entry->link != NULL)
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202 prev_cache_entry = cache_entry;
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203 }
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204 }
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205 else
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206 {
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207 adds = einfo->dlpi_adds;
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208 subs = einfo->dlpi_subs;
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209 /* Initialize the cache. Create a chain of cache entries,
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210 with the final one terminated by a NULL link. */
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211 int i;
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212 for (i = 0; i < FRAME_HDR_CACHE_SIZE; i++)
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213 {
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214 frame_hdr_cache[i].pc_low = 0;
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215 frame_hdr_cache[i].pc_high = 0;
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216 frame_hdr_cache[i].link = &frame_hdr_cache[i+1];
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217 }
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218 frame_hdr_cache[i-1].link = NULL;
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219 frame_hdr_cache_head = &frame_hdr_cache[0];
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220 data->check_cache = 0;
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221 }
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222 }
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223
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224 /* Make sure struct dl_phdr_info is at least as big as we need. */
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225 if (size < offsetof (struct dl_phdr_info, dlpi_phnum)
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226 + sizeof (info->dlpi_phnum))
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227 return -1;
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228
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229 _Unwind_Ptr pc_low = 0, pc_high = 0;
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230
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231 /* See if PC falls into one of the loaded segments. Find the eh_frame
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232 segment at the same time. */
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233 for (n = info->dlpi_phnum; --n >= 0; phdr++)
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234 {
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235 if (phdr->p_type == PT_LOAD)
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236 {
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237 _Unwind_Ptr vaddr = (_Unwind_Ptr)
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238 __RELOC_POINTER (phdr->p_vaddr, load_base);
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239 if (data->pc >= vaddr && data->pc < vaddr + phdr->p_memsz)
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240 {
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241 match = 1;
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242 pc_low = vaddr;
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243 pc_high = vaddr + phdr->p_memsz;
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244 }
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245 }
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246 else if (phdr->p_type == PT_GNU_EH_FRAME)
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247 p_eh_frame_hdr = phdr;
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248 else if (phdr->p_type == PT_DYNAMIC)
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249 p_dynamic = phdr;
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250 }
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251
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252 if (!match)
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253 return 0;
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254
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255 if (size >= sizeof (struct ext_dl_phdr_info))
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256 {
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257 /* Move the cache entry we're about to overwrite to the head of
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258 the list. If either last_cache_entry or prev_cache_entry are
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259 NULL, that cache entry is already at the head. */
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260 if (last_cache_entry != NULL && prev_cache_entry != NULL)
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261 {
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262 prev_cache_entry->link = last_cache_entry->link;
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263 last_cache_entry->link = frame_hdr_cache_head;
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264 frame_hdr_cache_head = last_cache_entry;
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265 }
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266
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267 frame_hdr_cache_head->load_base = load_base;
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268 frame_hdr_cache_head->p_eh_frame_hdr = p_eh_frame_hdr;
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269 frame_hdr_cache_head->p_dynamic = p_dynamic;
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270 frame_hdr_cache_head->pc_low = pc_low;
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271 frame_hdr_cache_head->pc_high = pc_high;
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272 }
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273
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274 found:
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275
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276 if (!p_eh_frame_hdr)
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277 return 0;
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278
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279 /* Read .eh_frame_hdr header. */
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280 hdr = (const struct unw_eh_frame_hdr *)
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281 __RELOC_POINTER (p_eh_frame_hdr->p_vaddr, load_base);
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282 if (hdr->version != 1)
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283 return 1;
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284
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285 #ifdef CRT_GET_RFIB_DATA
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286 # ifdef __i386__
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287 data->dbase = NULL;
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288 if (p_dynamic)
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289 {
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290 /* For dynamically linked executables and shared libraries,
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291 DT_PLTGOT is the gp value for that object. */
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292 ElfW(Dyn) *dyn = (ElfW(Dyn) *)
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293 __RELOC_POINTER (p_dynamic->p_vaddr, load_base);
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294 for (; dyn->d_tag != DT_NULL ; dyn++)
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295 if (dyn->d_tag == DT_PLTGOT)
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296 {
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297 /* On IA-32, _DYNAMIC is writable and GLIBC has relocated it. */
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298 data->dbase = (void *) dyn->d_un.d_ptr;
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299 break;
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300 }
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301 }
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302 # elif defined __FRV_FDPIC__ && defined __linux__
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303 data->dbase = load_base.got_value;
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304 # else
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305 # error What is DW_EH_PE_datarel base on this platform?
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306 # endif
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307 #endif
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308
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309 p = read_encoded_value_with_base (hdr->eh_frame_ptr_enc,
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310 base_from_cb_data (hdr->eh_frame_ptr_enc,
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311 data),
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312 (const unsigned char *) (hdr + 1),
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313 &eh_frame);
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314
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315 /* We require here specific table encoding to speed things up.
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316 Also, DW_EH_PE_datarel here means using PT_GNU_EH_FRAME start
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317 as base, not the processor specific DW_EH_PE_datarel. */
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318 if (hdr->fde_count_enc != DW_EH_PE_omit
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319 && hdr->table_enc == (DW_EH_PE_datarel | DW_EH_PE_sdata4))
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320 {
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321 _Unwind_Ptr fde_count;
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322
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323 p = read_encoded_value_with_base (hdr->fde_count_enc,
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324 base_from_cb_data (hdr->fde_count_enc,
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325 data),
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326 p, &fde_count);
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327 /* Shouldn't happen. */
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328 if (fde_count == 0)
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329 return 1;
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330 if ((((_Unwind_Ptr) p) & 3) == 0)
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331 {
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332 struct fde_table {
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333 signed initial_loc __attribute__ ((mode (SI)));
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334 signed fde __attribute__ ((mode (SI)));
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335 };
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336 const struct fde_table *table = (const struct fde_table *) p;
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337 size_t lo, hi, mid;
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338 _Unwind_Ptr data_base = (_Unwind_Ptr) hdr;
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339 fde *f;
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340 unsigned int f_enc, f_enc_size;
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341 _Unwind_Ptr range;
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342
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343 mid = fde_count - 1;
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344 if (data->pc < table[0].initial_loc + data_base)
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345 return 1;
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346 else if (data->pc < table[mid].initial_loc + data_base)
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347 {
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348 lo = 0;
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349 hi = mid;
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350
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351 while (lo < hi)
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352 {
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353 mid = (lo + hi) / 2;
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354 if (data->pc < table[mid].initial_loc + data_base)
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355 hi = mid;
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356 else if (data->pc >= table[mid + 1].initial_loc + data_base)
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357 lo = mid + 1;
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358 else
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359 break;
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360 }
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361
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362 gcc_assert (lo < hi);
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363 }
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364
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365 f = (fde *) (table[mid].fde + data_base);
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366 f_enc = get_fde_encoding (f);
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367 f_enc_size = size_of_encoded_value (f_enc);
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368 read_encoded_value_with_base (f_enc & 0x0f, 0,
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369 &f->pc_begin[f_enc_size], &range);
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370 if (data->pc < table[mid].initial_loc + data_base + range)
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371 data->ret = f;
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372 data->func = (void *) (table[mid].initial_loc + data_base);
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373 return 1;
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374 }
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375 }
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376
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377 /* We have no sorted search table, so need to go the slow way.
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378 As soon as GLIBC will provide API so to notify that a library has been
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379 removed, we could cache this (and thus use search_object). */
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380 ob.pc_begin = NULL;
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381 ob.tbase = data->tbase;
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382 ob.dbase = data->dbase;
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383 ob.u.single = (fde *) eh_frame;
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384 ob.s.i = 0;
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385 ob.s.b.mixed_encoding = 1; /* Need to assume worst case. */
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386 data->ret = linear_search_fdes (&ob, (fde *) eh_frame, (void *) data->pc);
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387 if (data->ret != NULL)
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388 {
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389 _Unwind_Ptr func;
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390 unsigned int encoding = get_fde_encoding (data->ret);
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391
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392 read_encoded_value_with_base (encoding,
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393 base_from_cb_data (encoding, data),
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394 data->ret->pc_begin, &func);
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395 data->func = (void *) func;
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396 }
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397 return 1;
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398 }
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399
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400 const fde *
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401 _Unwind_Find_FDE (void *pc, struct dwarf_eh_bases *bases)
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402 {
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403 struct unw_eh_callback_data data;
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404 const fde *ret;
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405
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406 ret = _Unwind_Find_registered_FDE (pc, bases);
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407 if (ret != NULL)
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408 return ret;
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409
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410 data.pc = (_Unwind_Ptr) pc;
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411 data.tbase = NULL;
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412 data.dbase = NULL;
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413 data.func = NULL;
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414 data.ret = NULL;
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415 data.check_cache = 1;
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416
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417 if (dl_iterate_phdr (_Unwind_IteratePhdrCallback, &data) < 0)
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418 return NULL;
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419
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420 if (data.ret)
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421 {
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422 bases->tbase = data.tbase;
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423 bases->dbase = data.dbase;
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424 bases->func = data.func;
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425 }
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426 return data.ret;
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427 }
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428
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429 #else
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430 /* Prevent multiple include of header files. */
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431 #define _Unwind_Find_FDE _Unwind_Find_FDE
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432 #include "unwind-dw2-fde.c"
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433 #endif
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434
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435 #if defined (USE_GAS_SYMVER) && defined (SHARED) && defined (USE_LIBUNWIND_EXCEPTIONS)
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436 alias (_Unwind_Find_FDE);
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437 #endif
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