129 lines
3.6 KiB
NASM
129 lines
3.6 KiB
NASM
;*************************************************************************
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; arch/z80/src/z180/z180_saveusercontext.asm
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;
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; Licensed to the Apache Software Foundation (ASF) under one or more
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; contributor license agreements. See the NOTICE file distributed with
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; this work for additional information regarding copyright ownership. The
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; ASF licenses this file to you under the Apache License, Version 2.0 (the
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; "License"); you may not use this file except in compliance with the
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; License. You may obtain a copy of the License at
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;
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; http://www.apache.org/licenses/LICENSE-2.0
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;
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; Unless required by applicable law or agreed to in writing, software
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; distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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; WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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; License for the specific language governing permissions and limitations
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; under the License.
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;
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;*************************************************************************
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;*************************************************************************
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; Constants
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;*************************************************************************
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; Register save area layout
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.globl XCPT_I ; Offset 0: Saved I w/interrupt state in parity
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.globl XCPT_BC ; Offset 1: Saved BC register
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.globl XCPT_DE ; Offset 2: Saved DE register
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.globl XCPT_IX ; Offset 3: Saved IX register
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.globl XCPT_IY ; Offset 4: Saved IY register
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.globl XCPT_SP ; Offset 5: Offset to SP at time of interrupt
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.globl XCPT_HL ; Offset 6: Saved HL register
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.globl XCPT_AF ; Offset 7: Saved AF register
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.globl XCPT_PC ; Offset 8: Offset to PC at time of interrupt
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; Stack frame
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FRAME_IY == 0 ; Location of IY on the stack
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FRAME_IX == 2 ; Location of IX on the stack
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FRAME_RET == 4 ; Location of return address on the stack
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FRAME_REGS == 6 ; Location of reg save area on stack
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SP_OFFSET == 6
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;*************************************************************************
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; Name: up_saveusercontext
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;*************************************************************************
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.area _CODE
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_up_saveusercontext:
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; Set up a stack frame
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push ix ; Save IX and IY
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push iy
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ld ix, #0
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add ix, sp ; IX = stack frame
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; Fetch the address of the save area
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ld e, FRAME_REGS(ix) ; HL = save area address
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ld d, FRAME_REGS+1(ix) ;
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ld iy, #0
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add iy, de ; IY = save area address
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; Then save the registers
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; Save the current interrupt state at offset 0
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ld a, i ; Get interrupt state
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push af
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pop hl
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ld XCPT_I(iy), l ; Offset 0: I w/interrupt state in parity
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ld XCPT_I+1(iy), h
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; Save BC at offset 1
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ld XCPT_BC(iy), c ; Offset 1: BC
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ld XCPT_BC+1(iy), b
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; DE is not preserved (offset 2)
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; Save IX at offset 3
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ld l, FRAME_IX(ix) ; HL = Saved value of IX
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ld h, FRAME_IX+1(ix) ;
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ld XCPT_IX(iy), l ; Offset 3: IX
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ld XCPT_IX+1(iy), h ;
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; Save IY at offset 4
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ld l, FRAME_IY(ix) ; HL = Saved value of IY
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ld h, FRAME_IY+1(ix) ;
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ld XCPT_IY(iy), l ; Offset 4: IY
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ld XCPT_IY+1(iy), h
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; Save that stack pointer as it would be upon return in offset 5
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ld hl, #SP_OFFSET ; Value of stack pointer on return
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add hl, sp
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ld XCPT_SP(iy), l ; Offset 5 SP
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ld XCPT_SP+1(iy), h
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; HL is saved as the value 1 at offset 6
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xor a ; A = 0
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ld XCPT_HL+1(iy), a ; Offset 2: HL on return (=1)
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inc a ; A = 1
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ld XCPT_HL(iy), a ;
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; AF is not preserved (offset 7)
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; Save the return address in offset 8
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ld l, FRAME_RET(ix) ; HL = Saved return address
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ld h, FRAME_RET+1(ix) ;
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ld XCPT_PC(iy), l ; Offset 8: PC
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ld XCPT_PC+1(iy), h
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; Return the value 0
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xor a ; HL = return value of zero
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ld l, a
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ld h, a
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pop iy
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pop ix
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ret
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