| 1 | /*********************************************************************
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| 2 | * SEGGER Microcontroller GmbH *
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| 3 | * The Embedded Experts *
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| 4 | **********************************************************************
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| 5 | * *
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| 6 | * (c) 2014 - 2024 SEGGER Microcontroller GmbH *
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| 7 | * *
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| 8 | * www.segger.com Support: support@segger.com *
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| 9 | * *
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| 10 | **********************************************************************
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| 11 | * *
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| 12 | * All rights reserved. *
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| 13 | * *
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| 14 | * Redistribution and use in source and binary forms, with or *
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| 15 | * without modification, are permitted provided that the following *
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| 16 | * condition is met: *
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| 17 | * *
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| 18 | * - Redistributions of source code must retain the above copyright *
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| 19 | * notice, this condition and the following disclaimer. *
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| 20 | * *
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| 21 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND *
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| 22 | * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, *
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| 23 | * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF *
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| 24 | * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE *
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| 25 | * DISCLAIMED. IN NO EVENT SHALL SEGGER Microcontroller BE LIABLE FOR *
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| 26 | * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR *
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| 27 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT *
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| 28 | * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; *
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| 29 | * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF *
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| 30 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT *
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| 31 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE *
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| 32 | * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH *
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| 33 | * DAMAGE. *
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| 34 | * *
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| 35 | **********************************************************************
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| 36 |
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| 37 | -------------------------- END-OF-HEADER -----------------------------
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| 38 |
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| 39 | File : SEGGER_THUMB_Startup.s
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| 40 | Purpose : Generic runtime init startup code for ARM CPUs running
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| 41 | in THUMB mode.
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| 42 | Designed to work with the SEGGER linker to produce
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| 43 | smallest possible executables.
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| 44 |
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| 45 | This file does not normally require any customization.
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| 46 |
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| 47 | Additional information:
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| 48 | Preprocessor Definitions
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| 49 | FULL_LIBRARY
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| 50 | If defined then
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| 51 | - argc, argv are set up by calling SEGGER_SEMIHOST_GetArgs().
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| 52 | - the exit symbol is defined and executes on return from main.
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| 53 | - the exit symbol calls destructors, atexit functions and then
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| 54 | calls SEGGER_SEMIHOST_Exit().
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| 55 |
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| 56 | If not defined then
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| 57 | - argc and argv are not valid (main is assumed to not take parameters)
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| 58 | - the exit symbol is defined, executes on return from main and
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| 59 | halts in a loop.
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| 60 | */
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| 61 |
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| 62 | .syntax unified
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| 63 |
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| 64 | /*********************************************************************
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| 65 | *
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| 66 | * Defines, configurable
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| 67 | *
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| 68 | **********************************************************************
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| 69 | */
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| 70 |
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| 71 | #ifndef APP_ENTRY_POINT
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| 72 | #define APP_ENTRY_POINT main
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| 73 | #endif
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| 74 |
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| 75 | #ifndef ARGSSPACE
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| 76 | #define ARGSSPACE 128
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| 77 | #endif
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| 78 |
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| 79 | /*********************************************************************
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| 80 | *
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| 81 | * Macros
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| 82 | *
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| 83 | **********************************************************************
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| 84 | */
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| 85 | //
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| 86 | // Declare a label as function symbol (without switching sections)
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| 87 | //
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| 88 | .macro MARK_FUNC Name
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| 89 | .global \Name
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| 90 | .thumb_func
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| 91 | .code 16
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| 92 | \Name:
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| 93 | .endm
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| 94 | //
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| 95 | // Declare a regular function.
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| 96 | // Functions from the startup are placed in the init section.
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| 97 | //
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| 98 | .macro START_FUNC Name
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| 99 | .section .init.\Name, "ax"
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| 100 | .global \Name
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| 101 | .balign 2
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| 102 | .thumb_func
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| 103 | .code 16
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| 104 | \Name:
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| 105 | .endm
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| 106 |
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| 107 | //
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| 108 | // Declare a weak function
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| 109 | //
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| 110 | .macro WEAK_FUNC Name
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| 111 | .section .init.\Name, "ax", %progbits
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| 112 | .weak \Name
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| 113 | .balign 2
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| 114 | .thumb_func
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| 115 | .code 16
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| 116 | \Name:
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| 117 | .endm
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| 118 |
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| 119 | //
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| 120 | // Mark the end of a function and calculate its size
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| 121 | //
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| 122 | .macro END_FUNC name
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| 123 | .size \name,.-\name
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| 124 | .endm
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| 125 |
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| 126 | /*********************************************************************
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| 127 | *
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| 128 | * Externals
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| 129 | *
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| 130 | **********************************************************************
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| 131 | */
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| 132 | .extern APP_ENTRY_POINT // typically main
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| 133 |
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| 134 | /*********************************************************************
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| 135 | *
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| 136 | * Global functions
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| 137 | *
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| 138 | **********************************************************************
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| 139 | */
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| 140 | /*********************************************************************
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| 141 | *
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| 142 | * _start
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| 143 | *
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| 144 | * Function description
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| 145 | * Entry point for the startup code.
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| 146 | * Usually called by the reset handler.
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| 147 | * Performs all initialisation, based on the entries in the
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| 148 | * linker-generated init table, then calls main().
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| 149 | * It is device independent, so there should not be any need for an
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| 150 | * end-user to modify it.
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| 151 | *
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| 152 | * Additional information
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| 153 | * At this point, the stack pointer should already have been
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| 154 | * initialized
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| 155 | * - by hardware (such as on Cortex-M),
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| 156 | * - by the device-specific reset handler,
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| 157 | * - or by the debugger (such as for RAM Code).
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| 158 | */
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| 159 | #undef L
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| 160 | #define L(label) .L_start_##label
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| 161 |
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| 162 | START_FUNC _start
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| 163 | //
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| 164 | // Call linker init functions which in turn performs the following:
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| 165 | // * Perform segment init
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| 166 | // * Perform heap init (if used)
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| 167 | // * Call constructors of global Objects (if any exist)
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| 168 | //
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| 169 | ldr R4, =__SEGGER_init_table__ // Set table pointer to start of initialization table
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| 170 | L(RunInit):
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| 171 | ldr R0, [R4] // Get next initialization function from table
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| 172 | adds R4, R4, #4 // Increment table pointer to point to function arguments
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| 173 | blx R0 // Call initialization function
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| 174 | b L(RunInit)
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| 175 | //
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| 176 | MARK_FUNC __SEGGER_init_done
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| 177 | MARK_FUNC __startup_complete
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| 178 | //
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| 179 | // Time to call main(), the application entry point.
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| 180 | //
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| 181 | #ifndef FULL_LIBRARY
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| 182 | //
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| 183 | // In a real embedded application ("Free-standing environment"),
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| 184 | // main() does not get any arguments,
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| 185 | // which means it is not necessary to init R0 and R1.
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| 186 | //
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| 187 | bl APP_ENTRY_POINT // Call to application entry point (usually main())
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| 188 |
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| 189 | END_FUNC _start
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| 190 | //
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| 191 | // end of _start
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| 192 | // Fall-through to exit if main ever returns.
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| 193 | //
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| 194 | MARK_FUNC exit
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| 195 | //
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| 196 | // In a free-standing environment, if returned from application:
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| 197 | // Loop forever.
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| 198 | //
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| 199 | b .
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| 200 | .size exit,.-exit
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| 201 | #else
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| 202 | //
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| 203 | // In a hosted environment,
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| 204 | // we need to load R0 and R1 with argc and argv, in order to handle
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| 205 | // the command line arguments.
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| 206 | // This is required for some programs running under control of a
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| 207 | // debugger, such as automated tests.
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| 208 | //
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| 209 | movs R0, #ARGSSPACE
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| 210 | ldr R1, =__SEGGER_init_arg_data
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| 211 | bl SEGGER_SEMIHOST_GetArgs
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| 212 | ldr R1, =__SEGGER_init_arg_data
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| 213 | bl APP_ENTRY_POINT // Call to application entry point (usually main())
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| 214 | bl exit // Call exit function
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| 215 | b . // If we unexpectedly return from exit, hang.
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| 216 | END_FUNC _start
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| 217 | #endif
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| 218 | //
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| 219 | #ifdef FULL_LIBRARY
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| 220 | /*********************************************************************
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| 221 | *
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| 222 | * exit
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| 223 | *
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| 224 | * Function description
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| 225 | * Exit of the system.
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| 226 | * Called on return from application entry point or explicit call
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| 227 | * to exit.
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| 228 | *
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| 229 | * Additional information
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| 230 | * In a hosted environment exit gracefully, by
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| 231 | * saving the return value,
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| 232 | * calling destructurs of global objects,
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| 233 | * calling registered atexit functions,
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| 234 | * and notifying the host/debugger.
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| 235 | */
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| 236 | #undef L
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| 237 | #define L(label) .L_exit_##label
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| 238 |
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| 239 | WEAK_FUNC exit
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| 240 | mov R5, R0 // Save the exit parameter/return result
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| 241 | //
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| 242 | // Call destructors
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| 243 | //
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| 244 | ldr R0, =__dtors_start__ // Pointer to destructor list
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| 245 | ldr R1, =__dtors_end__
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| 246 | L(Loop):
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| 247 | cmp R0, R1
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| 248 | beq L(End) // Reached end of destructor list? => Done
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| 249 | ldr R2, [R0] // Load current destructor address into R2
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| 250 | adds R0, R0, #4 // Increment pointer
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| 251 | push {R0-R1} // Save R0 and R1
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| 252 | blx R2 // Call destructor
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| 253 | pop {R0-R1} // Restore R0 and R1
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| 254 | b L(Loop)
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| 255 | L(End):
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| 256 | //
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| 257 | // Call atexit functions
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| 258 | //
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| 259 | bl __SEGGER_RTL_execute_at_exit_fns
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| 260 | //
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| 261 | // Call debug_exit with return result/exit parameter
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| 262 | //
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| 263 | mov R0, R5
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| 264 | //
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| 265 | // Entry points for _exit and _Exit, which terminate immediately.
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| 266 | // Note: Destructors and registered atexit functions are not called. File descriptors are not closed.
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| 267 | //
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| 268 | MARK_FUNC _exit
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| 269 | MARK_FUNC _Exit
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| 270 | bl SEGGER_SEMIHOST_Exit
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| 271 | //
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| 272 | // If execution is not terminated, loop forever
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| 273 | //
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| 274 | L(ExitLoop):
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| 275 | b L(ExitLoop) // Loop forever.
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| 276 | END_FUNC exit
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| 277 | #endif
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| 278 |
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| 279 | #ifdef FULL_LIBRARY
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| 280 | .bss
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| 281 | .balign 4
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| 282 | __SEGGER_init_arg_data:
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| 283 | .space ARGSSPACE
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| 284 | .size __SEGGER_init_arg_data, .-__SEGGER_init_arg_data
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| 285 | .type __SEGGER_init_arg_data, %object
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| 286 | #endif
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| 287 |
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| 288 | /*************************** End of file ****************************/
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