portable/BCC/16BitDOS/common/portasm.h

/*
 * FreeRTOS Kernel <DEVELOPMENT BRANCH>
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 */

#ifndef PORT_ASM_H
#define PORT_ASM_H

typedef void TCB_t;
extern volatile TCB_t * volatile pxCurrentTCB;
extern void vTaskSwitchContext( void );

/*
 * Saves the stack pointer for one task into its TCB, calls
 * vTaskSwitchContext() to update the TCB being used, then restores the stack
 * from the new TCB read to run the task.
 */
void portSWITCH_CONTEXT( void );

/*
 * Load the stack pointer from the TCB of the task which is going to be first
 * to execute.  Then force an IRET so the registers and IP are popped off the
 * stack.
 */
void portFIRST_CONTEXT( void );

/* There are slightly different versions depending on whether you are building
to include debugger information.  If debugger information is used then there
are a couple of extra bytes left of the ISR stack (presumably for use by the
debugger).  The true stack pointer is then stored in the bp register.  We add
2 to the stack pointer to remove the extra bytes before we restore our context. */

#define portSWITCH_CONTEXT()											\
							asm { mov	ax, seg pxCurrentTCB		}	\
							asm { mov	ds, ax						}	\
							asm { les	bx, pxCurrentTCB			}	/* Save the stack pointer into the TCB. */		\
							asm { mov	es:0x2[ bx ], ss			}	\
							asm { mov	es:[ bx ], sp				}	\
							asm { call  far ptr vTaskSwitchContext	}	/* Perform the switch. */						\
							asm { mov	ax, seg pxCurrentTCB		}	/* Restore the stack pointer from the TCB. */	\
							asm { mov	ds, ax						}	\
							asm { les	bx, dword ptr pxCurrentTCB	}	\
							asm { mov	ss, es:[ bx + 2 ]			}	\
							asm { mov	sp, es:[ bx ]				}

#define portFIRST_CONTEXT()												\
							__asm { mov	ax, seg pxCurrentTCB		}	\
							__asm { mov	ds, ax						}	\
							__asm { les	bx, dword ptr pxCurrentTCB	}	\
							__asm { mov	ss, es:[ bx + 2 ]			}	\
							__asm { mov	sp, es:[ bx ]				}	\
							__asm { pop	bp							}	\
							__asm { pop	di							}	\
							__asm { pop	si							}	\
							__asm { pop	ds							}	\
							__asm { pop	es							}	\
							__asm { pop	dx							}	\
							__asm { pop	cx							}	\
							__asm { pop	bx							}	\
							__asm { pop	ax							}	\
							__asm { iret							}


#endif