/*
 * FreeRTOS Kernel V10.3.1
 * 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.
 *
 * http://www.FreeRTOS.org
 * http://aws.amazon.com/freertos
 *
 */

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 /* 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 ]"


    #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 /* ifdef DEBUG_BUILD */