2 * FreeRTOS Kernel V10.0.1
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3 * Copyright (C) 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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5 * Permission is hereby granted, free of charge, to any person obtaining a copy of
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6 * this software and associated documentation files (the "Software"), to deal in
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7 * the Software without restriction, including without limitation the rights to
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8 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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9 * the Software, and to permit persons to whom the Software is furnished to do so,
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10 * subject to the following conditions:
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12 * The above copyright notice and this permission notice shall be included in all
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13 * copies or substantial portions of the Software.
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15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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17 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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18 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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19 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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20 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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22 * http://www.FreeRTOS.org
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23 * http://aws.amazon.com/freertos
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25 * 1 tab == 4 spaces!
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35 /* Hardware registers. */
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40 /* Variables and functions. */
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41 .extern ulMaxAPIPriorityMask
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42 .extern _freertos_vector_table
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43 .extern pxCurrentTCB
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44 .extern vTaskSwitchContext
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45 .extern vApplicationIRQHandler
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46 .extern ulPortInterruptNesting
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47 .extern ulPortTaskHasFPUContext
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49 .global FreeRTOS_IRQ_Handler
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50 .global FreeRTOS_SWI_Handler
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51 .global vPortRestoreTaskContext
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56 .macro portSAVE_CONTEXT
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58 /* Save the LR and SPSR onto the system mode stack before switching to
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59 system mode to save the remaining system mode registers. */
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60 SRSDB sp!, #SYS_MODE
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64 /* Push the critical nesting count. */
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65 LDR R2, ulCriticalNestingConst
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69 /* Does the task have a floating point context that needs saving? If
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70 ulPortTaskHasFPUContext is 0 then no. */
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71 LDR R2, ulPortTaskHasFPUContextConst
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75 /* Save the floating point context, if any. */
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81 /* Save ulPortTaskHasFPUContext itself. */
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84 /* Save the stack pointer in the TCB. */
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85 LDR R0, pxCurrentTCBConst
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91 ; /**********************************************************************/
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93 .macro portRESTORE_CONTEXT
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95 /* Set the SP to point to the stack of the task being restored. */
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96 LDR R0, pxCurrentTCBConst
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100 /* Is there a floating point context to restore? If the restored
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101 ulPortTaskHasFPUContext is zero then no. */
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102 LDR R0, ulPortTaskHasFPUContextConst
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107 /* Restore the floating point context, if any. */
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113 /* Restore the critical section nesting depth. */
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114 LDR R0, ulCriticalNestingConst
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118 /* Ensure the priority mask is correct for the critical nesting depth. */
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119 LDR R2, ulICCPMRConst
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123 LDRNE R4, ulMaxAPIPriorityMaskConst
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127 /* Restore all system mode registers other than the SP (which is already
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131 /* Return to the task code, loading CPSR on the way. */
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139 /******************************************************************************
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140 * SVC handler is used to start the scheduler.
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141 *****************************************************************************/
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143 .type FreeRTOS_SWI_Handler, %function
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144 FreeRTOS_SWI_Handler:
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145 /* Save the context of the current task and select a new task to run. */
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147 LDR R0, vTaskSwitchContextConst
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149 portRESTORE_CONTEXT
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152 /******************************************************************************
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153 * vPortRestoreTaskContext is used to start the scheduler.
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154 *****************************************************************************/
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155 .type vPortRestoreTaskContext, %function
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156 vPortRestoreTaskContext:
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157 /* Switch to system mode. */
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159 portRESTORE_CONTEXT
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162 .type FreeRTOS_IRQ_Handler, %function
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163 FreeRTOS_IRQ_Handler:
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164 /* Return to the interrupted instruction. */
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167 /* Push the return address and SPSR. */
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172 /* Change to supervisor mode to allow reentry. */
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175 /* Push used registers. */
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178 /* Increment nesting count. r3 holds the address of ulPortInterruptNesting
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179 for future use. r1 holds the original ulPortInterruptNesting value for
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181 LDR r3, ulPortInterruptNestingConst
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186 /* Read value from the interrupt acknowledge register, which is stored in r0
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187 for future parameter and interrupt clearing use. */
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188 LDR r2, ulICCIARConst
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192 /* Ensure bit 2 of the stack pointer is clear. r2 holds the bit 2 value for
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193 future use. _RB_ Does this ever actually need to be done provided the start
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194 of the stack is 8-byte aligned? */
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199 /* Call the interrupt handler. r4 pushed to maintain alignment. */
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201 LDR r1, vApplicationIRQHandlerConst
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210 /* Write the value read from ICCIAR to ICCEOIR. */
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211 LDR r4, ulICCEOIRConst
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215 /* Restore the old nesting count. */
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218 /* A context switch is never performed if the nesting count is not 0. */
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220 BNE exit_without_switch
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222 /* Did the interrupt request a context switch? r1 holds the address of
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223 ulPortYieldRequired and r0 the value of ulPortYieldRequired for future
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225 LDR r1, =ulPortYieldRequired
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228 BNE switch_before_exit
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230 exit_without_switch:
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231 /* No context switch. Restore used registers, LR_irq and SPSR before
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240 switch_before_exit:
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241 /* A context swtich is to be performed. Clear the context switch pending
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246 /* Restore used registers, LR-irq and SPSR before saving the context
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247 to the task stack. */
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255 /* Call the function that selects the new task to execute.
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256 vTaskSwitchContext() if vTaskSwitchContext() uses LDRD or STRD
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257 instructions, or 8 byte aligned stack allocated data. LR does not need
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258 saving as a new LR will be loaded by portRESTORE_CONTEXT anyway. */
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259 LDR R0, vTaskSwitchContextConst
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262 /* Restore the context of, and branch to, the task selected to execute
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264 portRESTORE_CONTEXT
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267 /******************************************************************************
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268 * If the application provides an implementation of vApplicationIRQHandler(),
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269 * then it will get called directly without saving the FPU registers on
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270 * interrupt entry, and this weak implementation of
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271 * vApplicationIRQHandler() will not get called.
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273 * If the application provides its own implementation of
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274 * vApplicationFPUSafeIRQHandler() then this implementation of
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275 * vApplicationIRQHandler() will be called, save the FPU registers, and then
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276 * call vApplicationFPUSafeIRQHandler().
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278 * Therefore, if the application writer wants FPU registers to be saved on
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279 * interrupt entry their IRQ handler must be called
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280 * vApplicationFPUSafeIRQHandler(), and if the application writer does not want
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281 * FPU registers to be saved on interrupt entry their IRQ handler must be
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282 * called vApplicationIRQHandler().
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283 *****************************************************************************/
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286 .weak vApplicationIRQHandler
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287 .type vApplicationIRQHandler, %function
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288 vApplicationIRQHandler:
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295 LDR r1, vApplicationFPUSafeIRQHandlerConst
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306 ulICCIARConst: .word ulICCIAR
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307 ulICCEOIRConst: .word ulICCEOIR
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308 ulICCPMRConst: .word ulICCPMR
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309 pxCurrentTCBConst: .word pxCurrentTCB
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310 ulCriticalNestingConst: .word ulCriticalNesting
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311 ulPortTaskHasFPUContextConst: .word ulPortTaskHasFPUContext
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312 ulMaxAPIPriorityMaskConst: .word ulMaxAPIPriorityMask
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313 vTaskSwitchContextConst: .word vTaskSwitchContext
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314 vApplicationIRQHandlerConst: .word vApplicationIRQHandler
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315 ulPortInterruptNestingConst: .word ulPortInterruptNesting
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316 vApplicationFPUSafeIRQHandlerConst: .word vApplicationFPUSafeIRQHandler
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