99 lines
3.3 KiB
ArmAsm
99 lines
3.3 KiB
ArmAsm
/* SPDX-License-Identifier: BSD-3-Clause */
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/* See the end of this file for copyright, licensing, and warranty information. */
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.syntax unified
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.thumb
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.text
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.extern sched_process_switch
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.thumb_func
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.global irq_pend_sv
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.type irq_pend_sv, %function
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/* void irq_pend_sv(void); */
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irq_pend_sv:
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/*
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* There seems to be a limitation in Thumb which prohibits popping to
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* any register > r7. Hence, we need to split the PUSHes and POPs into
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* multiple operations and MOV register values around.
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*/
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/*
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* Some registers have already been saved by hardware at this point,
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* we only need to take care of r4-r11 and lr (the latter of which is
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* required because lr is overwritten when entering the irq).
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* The stuff we push onto the stack manually looks about like this:
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*
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* >>> stack grow direction >>>
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* r7 r6 r5 r4 lr r11 r10 r9 r8
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*/
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push {r4-r7} /* r4-r7 */
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mov r3, r8
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mov r4, r9
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mov r5, r10
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mov r6, r11
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mov r7, lr
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push {r3-r7} /* r8-r11, lr */
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/*
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* Now that our stack is completely saved, we can proceed to call the
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* Kernel's scheduler. This updates `_current_process` to the process
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* we want to execute next.
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*/
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/* TODO: Implement banked stack pointer */
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mov r0, sp
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bl sched_process_switch /* sp = sched_process_switch(sp); */
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mov sp, r0
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/*
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* The new stack pointer contains the state of the new process, so we
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* load it into our registers using the same procedure as above,
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* just in reverse order.
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*/
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pop {r3-r7} /* r8-r11, lr */
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mov lr, r7
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mov r11, r6
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mov r10, r5
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mov r9, r4
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mov r8, r3
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pop {r4-r7} /* r4-r7 */
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/*
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* ... and now get the fuck outta here, hoping I never need to touch
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* this again, even though deep inside I know I will return here at some
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* point because something broke (or I feel the need to micro-optimize).
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*/
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bx lr
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.size irq_pend_sv, .-irq_pend_sv
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/*
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* Copyright (c) 2020 Felix Kopp <sandtler@sandtler.club>
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*
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* Redistribution and use in source and binary forms, with or without modification, are permitted
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* provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this list of
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* conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright notice, this list of
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* conditions and the following disclaimer in the documentation and/or other materials
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* provided with the distribution.
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* 3. Neither the name of the copyright holder nor the names of its contributors may be
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* used to endorse or promote products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
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* WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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