1 /* 2 * FreeRTOS Kernel V11.1.0 3 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved. 4 * 5 * SPDX-License-Identifier: MIT 6 * 7 * Permission is hereby granted, free of charge, to any person obtaining a copy of 8 * this software and associated documentation files (the "Software"), to deal in 9 * the Software without restriction, including without limitation the rights to 10 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of 11 * the Software, and to permit persons to whom the Software is furnished to do so, 12 * subject to the following conditions: 13 * 14 * The above copyright notice and this permission notice shall be included in all 15 * copies or substantial portions of the Software. 16 * 17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS 19 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR 20 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER 21 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 22 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 23 * 24 * https://www.FreeRTOS.org 25 * https://github.com/FreeRTOS 26 * 27 */ 28 29 typedef void TCB_t; 30 extern volatile TCB_t * volatile pxCurrentTCB; 31 extern void vTaskSwitchContext( void ); 32 33 /* 34 * Saves the stack pointer for one task into its TCB, calls 35 * vTaskSwitchContext() to update the TCB being used, then restores the stack 36 * from the new TCB read to run the task. 37 */ 38 void portSWITCH_CONTEXT( void ); 39 40 /* 41 * Load the stack pointer from the TCB of the task which is going to be first 42 * to execute. Then force an IRET so the registers and IP are popped off the 43 * stack. 44 */ 45 void portFIRST_CONTEXT( void ); 46 47 /* There are slightly different versions depending on whether you are building 48 to include debugger information. If debugger information is used then there 49 are a couple of extra bytes left of the ISR stack (presumably for use by the 50 debugger). The true stack pointer is then stored in the bp register. We add 51 2 to the stack pointer to remove the extra bytes before we restore our context. */ 52 53 #ifdef DEBUG_BUILD 54 55 #pragma aux portSWITCH_CONTEXT = "mov ax, seg pxCurrentTCB" \ 56 "mov ds, ax" \ 57 "les bx, pxCurrentTCB" /* Save the stack pointer into the TCB. */ \ 58 "mov es:0x2[ bx ], ss" \ 59 "mov es:[ bx ], sp" \ 60 "call vTaskSwitchContext" /* Perform the switch. */ \ 61 "mov ax, seg pxCurrentTCB" /* Restore the stack pointer from the TCB. */ \ 62 "mov ds, ax" \ 63 "les bx, dword ptr pxCurrentTCB" \ 64 "mov ss, es:[ bx + 2 ]" \ 65 "mov sp, es:[ bx ]" \ 66 "mov bp, sp" /* Prepair the bp register for the restoration of the SP in the compiler generated portion of the ISR */ \ 67 "add bp, 0x0002" 68 69 70 71 #pragma aux portFIRST_CONTEXT = "mov ax, seg pxCurrentTCB" \ 72 "mov ds, ax" \ 73 "les bx, dword ptr pxCurrentTCB" \ 74 "mov ss, es:[ bx + 2 ]" \ 75 "mov sp, es:[ bx ]" \ 76 "add sp, 0x0002" /* Remove the extra bytes that exist in debug builds before restoring the context. */ \ 77 "pop ax" \ 78 "pop ax" \ 79 "pop es" \ 80 "pop ds" \ 81 "popa" \ 82 "iret" 83 #else 84 85 #pragma aux portSWITCH_CONTEXT = "mov ax, seg pxCurrentTCB" \ 86 "mov ds, ax" \ 87 "les bx, pxCurrentTCB" /* Save the stack pointer into the TCB. */ \ 88 "mov es:0x2[ bx ], ss" \ 89 "mov es:[ bx ], sp" \ 90 "call vTaskSwitchContext" /* Perform the switch. */ \ 91 "mov ax, seg pxCurrentTCB" /* Restore the stack pointer from the TCB. */ \ 92 "mov ds, ax" \ 93 "les bx, dword ptr pxCurrentTCB" \ 94 "mov ss, es:[ bx + 2 ]" \ 95 "mov sp, es:[ bx ]" 96 97 98 #pragma aux portFIRST_CONTEXT = "mov ax, seg pxCurrentTCB" \ 99 "mov ds, ax" \ 100 "les bx, dword ptr pxCurrentTCB" \ 101 "mov ss, es:[ bx + 2 ]" \ 102 "mov sp, es:[ bx ]" \ 103 "pop ax" \ 104 "pop ax" \ 105 "pop es" \ 106 "pop ds" \ 107 "popa" \ 108 "iret" 109 #endif 110
