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/**************************************************************************
* arch/z80/src/z8/z8_saveusercontext.S
* Save the state of the current user thread
*
* Copyright (C) 2008 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS or IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER or CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, or CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS or SERVICES; LOSS
* OF USE, DATA, or PROFITS; or BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, or TORT (INCLUDING NEGLIGENCE or OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
**************************************************************************/
/**************************************************************************
* Included Files
**************************************************************************/
#include <nuttx/config.h>
#include <arch/irq.h>
#include <ez8.inc>
/**************************************************************************
* Definitions
**************************************************************************/
xdef _z8_saveusercontext
/**************************************************************************
* Code
**************************************************************************/
segment CODE
/****************************************************************************
* Name: _z8_saveusercontext
*
* Description:
* Save the current state of the user thread. Since this function is
* called from user code, it is only necessary to save the parts of the
* context that must be preserved between function calls. This includes
*
* - Frame pointer (r14, r15)
* - Register pointer (RP)
* - Interrupt state (flags)
* - Stack pointer (sph, spl)
* - Return address
*
* Parameters:
* On entry, the following stack organization is assumed:
*
* Pointer to the context save structure
* TOS -> Return address (2)
*
* Assumptions:
* Large model, dynamic frames
*
**************************************************************************/
_z8_saveusercontext:
/* Get the rr6 = the current value of the stack pointer */
ldx r6, sph /* rr6 = stack pointer */
ldx r7, spl
/* Get rr2 = the pointer to the context save structure */
ldx r2, 2(rr6) /* rr2 = pointer to context structure */
ldx r3, 3(rr6)
/* Get the value currently in the interrupt control register.
* Bit 7 (IRQE) determines whether or not interrupts are
* currently enabled (0:disabled, 1:enabled)
*/
ldx r4, IRQCTL /* r4 = IRQCTL value */
/* Disable all interrupts so that there can be no concurrent
* modification of the TCB state save area.
*/
di
/* Fetch and save the return address from the stack */
ldx r0, @rr6 /* rr0 = return address */
ldx r1, 1(rr6)
ldx XCPT_PCH_OFFS(rr2), r0
ldx XCPT_PCL_OFFS(rr2), r1
/* Fetch and save the register pointer */
ldx r0, rp /* r0 = register pointer */
ldx XCPT_RP_OFFS(rr2), r0
/* Calculate the value of the stack pointer on return
* from this function
*/
ld r1, #3 /* rr0 = 3 */
clr r0
add r1, r7 /* rr0 = SP + 3 */
adc r0, r6
ldx XCPT_SPH_OFFS(rr2), r0
ldx XCPT_SPL_OFFS(rr2), r1
/* Save the IRQCTL register value */
clr r0
ldx XCPT_UNUSED_OFFS(rr2), r0
ldx XCPT_IRQCTL_OFFS(rr2), r4
/* Save the frame pointer (rr14) in the context structure */
ldx XCPT_R14_OFFS(rr2), r14
ldx XCPT_R15_OFFS(rr2), r15
/* Set the return value of 1 in the context structure. When the
* state is restored (via z8_restorecontext() or an interrupt
* return), the return value of 1 distinguishes the no-context-
* switch case.
*/
/* clr r0 */
ld r1, #1
ldx XCPT_R0_OFFS(rr2), r0
ldx XCPT_R1_OFFS(rr2), r1
/* Setup to return zero for the no-context-switch case */
/* clr r0 */
clr r1
/* Now decide if we need to re-enable interrupts or not */
tm r4, #%80
jr z, _z8_noenable
ei
_z8_noenable:
ret
end
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