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1 /****************************************************************************
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2 * *
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3 * GNAT COMPILER COMPONENTS *
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4 * *
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5 * S I G T R A M P *
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6 * *
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7 * Asm Implementation File *
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8 * *
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131
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9 * Copyright (C) 2015-2018, Free Software Foundation, Inc. *
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111
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10 * *
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11 * GNAT is free software; you can redistribute it and/or modify it under *
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12 * terms of the GNU General Public License as published by the Free Soft- *
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13 * ware Foundation; either version 3, or (at your option) any later ver- *
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14 * sion. GNAT is distributed in the hope that it will be useful, but WITH- *
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15 * OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY *
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16 * or FITNESS FOR A PARTICULAR PURPOSE. *
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17 * *
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18 * As a special exception under Section 7 of GPL version 3, you are granted *
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19 * additional permissions described in the GCC Runtime Library Exception, *
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20 * version 3.1, as published by the Free Software Foundation. *
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21 * *
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22 * In particular, you can freely distribute your programs built with the *
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23 * GNAT Pro compiler, including any required library run-time units, using *
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24 * any licensing terms of your choosing. See the AdaCore Software License *
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25 * for full details. *
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26 * *
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27 * GNAT was originally developed by the GNAT team at New York University. *
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28 * Extensive contributions were provided by Ada Core Technologies Inc. *
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29 * *
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30 ****************************************************************************/
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31
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32 /******************************************************
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33 * ARM-Android version of the __gnat_sigtramp service *
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34 ******************************************************/
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35
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36 #include <sys/ucontext.h>
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37
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38 #include "sigtramp.h"
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39 /* See sigtramp.h for a general explanation of functionality. */
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40
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41 /* ----------------------
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42 -- General comments --
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43 ----------------------
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44
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45 Stubs are generated from toplevel asms,
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46 The general idea is to establish CFA as the sigcontext
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47 and state where to find the registers as offsets from there.
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48
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49 We support stubs for VxWorks and Android, providing unwind info for
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50 common registers. We might need variants with support for floating
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51 point or altivec registers as well at some point.
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52
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53 For Android it would be simpler to write this in Asm since there's only
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54 one variant, but to keep it looking like the VxWorks stubs,
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55 C is the choice for our toplevel interface.
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56
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57 Note that the registers we "restore" here are those to which we have
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58 direct access through the system sigcontext structure, which includes
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59 only a partial set of the non-volatiles ABI-wise. */
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60
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61 /* -----------------------------------------
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62 -- Protypes for our internal asm stubs --
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63 -----------------------------------------
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64
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65 The registers are expected to be at SIGCONTEXT + 12 (reference the
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66 sicontext structure in asm/sigcontext.h which describes the first
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67 3 * 4byte fields.) Even though our symbols will remain local, the
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68 prototype claims "extern" and not "static" to prevent compiler complaints
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69 about a symbol used but never defined. */
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70
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71 /* sigtramp stub providing unwind info for common registers. */
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72
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73 extern void __gnat_sigtramp_common
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74 (int signo, void *siginfo, void *sigcontext,
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75 __sigtramphandler_t * handler);
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76
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77 void __gnat_sigtramp (int signo, void *si, void *sc,
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78 __sigtramphandler_t * handler)
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79 __attribute__((optimize(2)));
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80
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81 void __gnat_sigtramp (int signo, void *si, void *ucontext,
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82 __sigtramphandler_t * handler)
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83 {
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84 struct sigcontext *mcontext = &((ucontext_t *) ucontext)->uc_mcontext;
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85
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86 __gnat_sigtramp_common (signo, si, mcontext, handler);
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87 }
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88
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89 /* asm string construction helpers. */
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90
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91 #define STR(TEXT) #TEXT
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92 /* stringify expanded TEXT, surrounding it with double quotes. */
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93
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94 #define S(E) STR(E)
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95 /* stringify E, which will resolve as text but may contain macros
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96 still to be expanded. */
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97
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98 /* asm (TEXT) outputs <tab>TEXT. These facilitate the output of
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99 multiline contents: */
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100 #define TAB(S) "\t" S
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101 #define CR(S) S "\n"
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102
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103 #undef TCR
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104 #define TCR(S) TAB(CR(S))
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105
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106 /* Trampoline body block
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107 --------------------- */
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108
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109 #define SIGTRAMP_BODY \
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110 CR("") \
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111 TCR("# Allocate frame and also save r2 which is the argument register") \
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112 TCR("# containing the sigcontext, so that we can restore it during") \
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113 TCR("# unwinding and thereby load the rest of the desired context.") \
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114 TCR("stmfd sp!, {r2, r3, lr}") \
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115 TCR("# The unwinder undo's these operations in reverse order so starting") \
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116 TCR("# from bottom, restore r2 from the current vsp location, move r2 into") \
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117 TCR("# the vsp, add 12 bytes to get the start of the register save area") \
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118 TCR("# then restore the 15 general purpose registers of the frame which") \
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119 TCR("# raised the signal.") \
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120 TCR(".save {r0-r15}") \
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121 TCR(".pad #12") \
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122 TCR(".movsp r2") \
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123 TCR(".save {r2}") \
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124 TCR("# Call the real handler. The signo, siginfo and sigcontext") \
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125 TCR("# arguments are the same as those we received in r0, r1 and r2.") \
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126 TCR("blx r3") \
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127 TCR("# Restore our callee-saved items, release our frame and return") \
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128 TCR("# (should never get here!).") \
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129 TCR("ldmfd sp, {r2, r3, pc}")
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130
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131 /* Symbol definition block
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132 ----------------------- */
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133
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134 #define SIGTRAMP_START(SYM) \
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135 CR("# " S(SYM) " unwind trampoline") \
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136 TCR(".type " S(SYM) ", %function") \
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137 CR("") \
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138 CR(S(SYM) ":") \
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139 TCR(".fnstart")
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140
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141 /* Symbol termination block
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142 ------------------------ */
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143
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144 #define SIGTRAMP_END(SYM) \
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145 CR(".fnend") \
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146 TCR(".size " S(SYM) ", .-" S(SYM))
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147
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148 /*----------------------------
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149 -- And now, the real code --
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150 ---------------------------- */
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151
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152 /* Text section start. The compiler isn't aware of that switch. */
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153
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154 asm (".text\n"
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155 TCR(".align 2"));
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156
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157 /* sigtramp stub for common registers. */
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158
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159 #define TRAMP_COMMON __gnat_sigtramp_common
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160
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161 asm (SIGTRAMP_START(TRAMP_COMMON));
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162 asm (SIGTRAMP_BODY);
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163 asm (SIGTRAMP_END(TRAMP_COMMON));
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