annotate doc/manual/callconvs/callconv_ppc64.tex @ 345:c607d67cd6b8 r1.1-RC2

- doc: added syscall info to appendix, fixed broken literature link - cleanup, added missing forward declarations, ...
author Tassilo Philipp
date Tue, 07 Jan 2020 21:52:57 +0100
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1 %//////////////////////////////////////////////////////////////////////////////
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2 %
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3 % Copyright (c) 2007-2019 Daniel Adler <dadler@uni-goettingen.de>,
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4 % Tassilo Philipp <tphilipp@potion-studios.com>
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5 %
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6 % Permission to use, copy, modify, and distribute this software for any
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7 % purpose with or without fee is hereby granted, provided that the above
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8 % copyright notice and this permission notice appear in all copies.
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9 %
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10 % THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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11 % WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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12 % MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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13 % ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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14 % WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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15 % ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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16 % OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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17 %
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18 %//////////////////////////////////////////////////////////////////////////////
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19
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20 % ==================================================
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21 % PowerPC 64
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22 % ==================================================
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23 \subsection{PowerPC (64bit) Calling Conventions}
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24
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25 \paragraph{Overview}
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27 \begin{itemize}
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28 \item Word size is 32 bits for historical reasons
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29 \item Big endian (MSB) and litte endian (LSB) operating modes.
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30 \item Apple Mac OS X/Darwin PPC is specified in "Mac OS X ABI Function Call Guide"\cite{ppcMacOSX}. It uses Big Endian (MSB).
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31 \item Linux PPC 64-bit ABI is specified in "64-bit PowerPC ELF Application Binary Interface Supplement"\cite{ppcelf64abi} which is based on "System V ABI".
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32 \end{itemize}
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33
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34 \paragraph{\product{dyncall} support}
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35
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36 \product{Dyncall} and \product{dyncallback} are supported for PowerPC (64bit)
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37 Big Endian and Little Endian ELF ABIs on System V systems. Mac OS X is not
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38 supported.\\
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39 \product{Dyncall} can also be used to issue syscalls by using the syscall
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40 number as target parameter and selecting the correct mode.
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43 \subsubsection{PPC64 ELF ABI}
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44
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45 \paragraph{Registers and register usage}
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46
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47 \begin{table}[h]
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48 \begin{tabular*}{0.95\textwidth}{3 B}
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49 Name & Brief description\\
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50 \hline
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51 {\bf gpr0} & scratch\\
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52 {\bf gpr1} & stack pointer\\
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53 {\bf gpr2} & TOC base ptr (offset table and data for position independent code), scratch\\
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54 {\bf gpr3} & return value, parameter 0 for integer or pointer, scratch\\
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55 {\bf gpr4-gpr10} & parameter 1-7 for integer or pointer parameters, scratch\\
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57 {\bf gpr11} & env pointer if needed, scratch\\
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58 {\bf gpr12} & used for exception handling and glink code, scratch\\
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59 {\bf gpr13} & used for system thread ID, preserve\\
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60 {\bf gpr14-31} & preserve\\
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61 {\bf fpr0} & scratch\\
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62 {\bf fpr1-fpr4} & floating point return value, floating point parameter 0-3 (always double precision)\\
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63 {\bf fpr5-fpr13} & floating point parameters 4-12 (always double precision)\\
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64 {\bf fpr14-fpr31} & preserve\\
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65 {\bf v0-v1} & scratch\\
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66 {\bf v2-v13} & vector parameters\\
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67 {\bf v14-v19} & scratch\\
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68 {\bf v20-v31} & preserve\\
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69 {\bf lr} & link-register, scratch\\
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70 {\bf ctr} & count-register, scratch\\
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71 {\bf xer} & fixed point exception register, scratch\\
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72 {\bf fpscr} & floating point status and control register, scratch\\
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73 {\bf cr0-cr7} & conditional register fields, each 4-bit wide (cr0-cr1 and cr5-cr7 are scratch)\\
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74 \end{tabular*}
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75 \caption{Register usage on PowerPC 64-Bit ELF ABI}
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76 \end{table}
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78 \paragraph{Parameter passing}
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79
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80 \begin{itemize}
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81 \item stack grows down
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82 \item stack parameter order: right-to-left
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83 \item caller cleans up the stack
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84 \item stack is always 16 byte aligned
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85 \item the stack pointer must be atomically updated (to avoid any timing window in which an interrupt can occur with a partially updated stack), usually with the stdu (store doubleword with update) instruction
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86 \item the first 8 integer parameters are passed in registers gpr3-gpr10
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87 \item the first 13 floating point parameters are passed in registers fpr1-fpr13
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88 \item preserved registers are saved using a defined order (from high to low addresses):
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89 fpr* (64bit aligned),
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90 gpr*,
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91 VRSAVE save word (32 bits),
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92 padding for alignment (4 or 12 bytes),
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93 v* (128bit aligned)
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94 \item if a floating point parameter is passed via a register, a gpr registers is skipped for subsequent integer parameters
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95 \item the caller pushes subsequent parameters onto the stack
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96 \item single precision floating point values use the second word in a doubleword
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97 \item a quad precision floating point argument is passed as two consecutive double precision ones
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98 \item integer types \textless\ 64 bit are sign or zero extended and use a doubleword
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99 \item ellipsis calls take floating point values in int and float registers (single precision floats are promoted to double precision as
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100 required by ellipsis calls)
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101 \item space for all potential gpr* register passed arguments is reserved in the stack parameter area (in order to spill the parameters if
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102 needed - e.g. varargs), meaning a minimum of 64 bytes to hold gpr3-gpr10
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103 \item all nonvector parameters are aligned on 8-byte boundaries
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104 \item vector parameters are aligned on 16-byte boundaries
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105 \item integer parameters \textless\ 64 bit are right-justified (meaning occupy higher-address bytes) in their 8-byte slot on the stack, requiring extra-care for big-endian targets
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106 \end{itemize}
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107
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108
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109 \paragraph{Return values}
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110
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111 \begin{itemize}
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112 \item return values of integer \textless=\ 32bit or pointer type use gpr3 and are zero or sign extended depending on their type
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113 \item 64 bit integers use gpr3
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114 \item floating point values are returned via fpr1
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115 \item character arrays \textless=\ 8 bytes use gpr3, and are right justified
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116 \item for all structs/unions (regardless of size) or character arrays \textgreater\ 8 bytes, a secret first parameter with an address to a caller allocated space is passed as first argument to the function (meaning in gpr3), which is written to by the callee
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117 \end{itemize}
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120 \paragraph{Stack layout}
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121
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122 Stack frame is always 16-byte aligned.
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123 % verified/amended: TP nov 2019 (see also doc/disas_examples/ppc64.elfabi.disas)
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124 Stack directly after function prolog:\\
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126 \begin{figure}[h]
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127 \begin{tabular}{5|3|1 1}
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128 & \vdots & & \\
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129 \hhline{~=~~}
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130 register save area & \hspace{4cm} & & \mrrbrace{14}{caller's frame} \\
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131 \hhline{~-~~}
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132 local data & & & \\
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133 \hhline{~-~~}
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134 \mrlbrace{6}{parameter area} & last arg & \mrrbrace{3}{stack parameters} & \\
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135 & \ldots & & \\
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136 & arg 8 & & \\
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137 & gpr10 & \mrrbrace{3}{spill area (as needed)} & \\
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138 & \ldots & & \\
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139 & gpr3 & & \\
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140 \hhline{~-~~}
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141 \mrlbrace{6}{linkage area} & TOC ptr reg & & \\
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142 & reserved & & \\
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143 & reserved & & \\
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144 & return address (callee saved) & & \\
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145 & condition reg (callee saved) & & \\
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146 & parent stack frame pointer & & \\
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147 \hhline{~=~~}
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148 register save area & & & \mrrbrace{4}{current frame} \\
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149 \hhline{~-~~}
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150 local data & & & \\
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151 \hhline{~-~~}
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152 parameter area & & & \\
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153 \hhline{~-~~}
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154 linkage area & \vdots & & \\
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155 \end{tabular}
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156 \caption{Stack layout on ppc64 ELF ABI}
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157 \end{figure}
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158
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159
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160 \newpage
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161
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162 \subsubsection{System V syscalls}
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163
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164 \paragraph{Parameter passing}
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165
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166 \begin{itemize}
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167 \item syscall is issued via the {\em sc} instruction
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168 \item kernel destroys registers r13
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169 \item syscall number is set in r0
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170 \item params are passed in registers r3 through r10
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171 \item no stack in use, meaning syscalls are in theory limited to eight arguments
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172 \item register r3 holds the return value, overflow flag in conditional register cr0 signals errors in syscall
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173 \end{itemize}
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174