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 #ifndef PORT_ASM_H 30 #define PORT_ASM_H 31 32 typedef void TCB_t; 33 extern volatile TCB_t * volatile pxCurrentTCB; 34 extern void vTaskSwitchContext( void ); 35 36 /* 37 * Saves the stack pointer for one task into its TCB, calls 38 * vTaskSwitchContext() to update the TCB being used, then restores the stack 39 * from the new TCB read to run the task. 40 */ 41 void portSWITCH_CONTEXT( void ); 42 43 /* 44 * Load the stack pointer from the TCB of the task which is going to be first 45 * to execute. Then force an IRET so the registers and IP are popped off the 46 * stack. 47 */ 48 void portFIRST_CONTEXT( void ); 49 50 /* There are slightly different versions depending on whether you are building 51 to include debugger information. If debugger information is used then there 52 are a couple of extra bytes left of the ISR stack (presumably for use by the 53 debugger). The true stack pointer is then stored in the bp register. We add 54 2 to the stack pointer to remove the extra bytes before we restore our context. */ 55 56 #define portSWITCH_CONTEXT() \ 57 asm { mov ax, seg pxCurrentTCB } \ 58 asm { mov ds, ax } \ 59 asm { les bx, pxCurrentTCB } /* Save the stack pointer into the TCB. */ \ 60 asm { mov es:0x2[ bx ], ss } \ 61 asm { mov es:[ bx ], sp } \ 62 asm { call far ptr vTaskSwitchContext } /* Perform the switch. */ \ 63 asm { mov ax, seg pxCurrentTCB } /* Restore the stack pointer from the TCB. */ \ 64 asm { mov ds, ax } \ 65 asm { les bx, dword ptr pxCurrentTCB } \ 66 asm { mov ss, es:[ bx + 2 ] } \ 67 asm { mov sp, es:[ bx ] } 68 69 #define portFIRST_CONTEXT() \ 70 __asm { mov ax, seg pxCurrentTCB } \ 71 __asm { mov ds, ax } \ 72 __asm { les bx, dword ptr pxCurrentTCB } \ 73 __asm { mov ss, es:[ bx + 2 ] } \ 74 __asm { mov sp, es:[ bx ] } \ 75 __asm { pop bp } \ 76 __asm { pop di } \ 77 __asm { pop si } \ 78 __asm { pop ds } \ 79 __asm { pop es } \ 80 __asm { pop dx } \ 81 __asm { pop cx } \ 82 __asm { pop bx } \ 83 __asm { pop ax } \ 84 __asm { iret } 85 86 87 #endif 88
