/*
 * FreeRTOS Kernel <DEVELOPMENT BRANCH>
 * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * 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
 *
 * 1 tab == 4 spaces!
 */

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. */

#ifdef DEBUG_BUILD

	#pragma aux portSWITCH_CONTEXT =	"mov	ax, seg pxCurrentTCB"														\
										"mov	ds, ax"																		\
										"les	bx, pxCurrentTCB"			/* Save the stack pointer into the TCB. */		\
										"mov	es:0x2[ bx ], ss"															\
										"mov	es:[ bx ], sp"																\
										"call	vTaskSwitchContext"			/* Perform the switch. */						\
										"mov	ax, seg pxCurrentTCB"		/* Restore the stack pointer from the TCB. */	\
										"mov	ds, ax"																		\
										"les	bx, dword ptr pxCurrentTCB"													\
										"mov	ss, es:[ bx + 2 ]"															\
										"mov	sp, es:[ bx ]"																\
										"mov	bp, sp"						/* Prepair the bp register for the restoration of the SP in the compiler generated portion of the ISR */	\
										"add	bp, 0x0002"

										

	#pragma aux portFIRST_CONTEXT =		"mov	ax, seg pxCurrentTCB"			\
										"mov	ds, ax"							\
										"les	bx, dword ptr pxCurrentTCB"		\
										"mov	ss, es:[ bx + 2 ]"				\
										"mov	sp, es:[ bx ]"					\
										"add	sp, 0x0002"						/* Remove the extra bytes that exist in debug builds before restoring the context. */ \
										"pop	ax"								\
										"pop	ax"								\
										"pop	es"								\
										"pop	ds"								\
										"popa"									\
										"iret"									
#else

	#pragma aux portSWITCH_CONTEXT =	"mov	ax, seg pxCurrentTCB"														\
										"mov	ds, ax"																		\
										"les	bx, pxCurrentTCB"			/* Save the stack pointer into the TCB. */		\
										"mov	es:0x2[ bx ], ss"															\
										"mov	es:[ bx ], sp"																\
										"call	vTaskSwitchContext"			/* Perform the switch. */						\
										"mov	ax, seg pxCurrentTCB"		/* Restore the stack pointer from the TCB. */	\
										"mov	ds, ax"																		\
										"les	bx, dword ptr pxCurrentTCB"													\
										"mov	ss, es:[ bx + 2 ]"															\
										"mov	sp, es:[ bx ]"
										

	#pragma aux portFIRST_CONTEXT =		"mov	ax, seg pxCurrentTCB"			\
										"mov	ds, ax"							\
										"les	bx, dword ptr pxCurrentTCB"		\
										"mov	ss, es:[ bx + 2 ]"				\
										"mov	sp, es:[ bx ]"					\
										"pop	ax"								\
										"pop	ax"								\
										"pop	es"								\
										"pop	ds"								\
										"popa"									\
										"iret"									
#endif