279 lines
4.8 KiB
ArmAsm
279 lines
4.8 KiB
ArmAsm
; Copyright 2021-2024 Sebastian Lederer. See the file LICENSE.md for details
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.ORG 4096
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CORELOADER:
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; initialize program stack and
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; return stack pointers
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LOADCP 24060
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STOREREG FP
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LOADCP 24064
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STOREREG RP
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LOADCP SYSBOOTTICKS
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LOADCP GETTICKS
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CALL
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STOREI
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DROP
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LOADCP INITSDCARD
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CALL
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;LOADCP FIND_SYSPART ; no need to call, it never
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;CALL ; returns, so just fall through
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.EQU PART_START 0
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.EQU EXTENT_SIZE 4
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.EQU DIR_SIZE 8
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.EQU SLOT_NO 12
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.EQU SIZE_BYTES 16
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.EQU PRG_START_BLK 20
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.EQU FIND_FS 24
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.EQU PARTENTRY_SIZE 64
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.EQU DIRENTRY_SIZE 64
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FIND_SYSPART:
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FPADJ -FIND_FS
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; load block 0
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LOADC 0
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LOADCP CARDREADBLK
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CALL
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DUP ; non-zero return code means error
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CBRANCH.Z FIND_1
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LOADCP PRINTHEXW
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CALL
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LOADCP NEWLINE
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CALL
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LOADC 0
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JUMP
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FIND_1:
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DROP ; remove return code
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;LOADC 512
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;LOADCP CARD_BUF
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;LOADCP HEXDUMP
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;CALL
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; address of the first partition entry
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LOADCP CARD_BUF
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FIND_L:
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DUP ; dup addr for comparison
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LOADCP SYSPART_NAME
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LOADC SYSNAME_WORDS
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LOADCP _CMPWORDS
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CALL
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CBRANCH.NZ FIND_FOUND
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; go to next entry
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LOADC PARTENTRY_SIZE
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ADD
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; check if address is still
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; within the data block
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DUP
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LOADCP CARD_BUF,512
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CMP LT
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CBRANCH FIND_L
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; remove address
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DROP
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; not found, complain and
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; go back to ROM monitor
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LOADCP SYSPART_ERR
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LOADCP PRINTLINE
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CALL
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LOADC 0
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JUMP
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FIND_FOUND:
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; address of the part entry is on stack
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; check if partition is enabled
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DUP ; duplicate address
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LOADC 40 ; add PartFlags field offset
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ADD
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LOADI
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LOADC 1
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AND ; check bit 0 (PartEnabled)
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CBRANCH.Z FIND_L ; if not set, continue loop
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; address of part entry is still on stack
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DUP
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LOADC 44 ; add startBlock field offset
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ADD
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LOADI ; get start block number
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STORE PART_START
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; address of part entry is still on stack
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DUP
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LOADC 52 ; move to extentSize field
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ADD
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LOADI ; get value
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STORE EXTENT_SIZE
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; address of part entry is still on stack
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LOADC 56 ; move to dirSize field
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ADD
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LOADI ; get value
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STORE DIR_SIZE
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LOADC 0
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STORE SLOT_NO ; start with dirslot 0
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LOAD PART_START ; start with first block of the partition
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FIND_FILE:
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DUP ; duplicate block number
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LOADCP CARDREADBLK ; read that block
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CALL
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DROP ; ignore error
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; scan directory entries for shell file name
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LOADCP CARD_BUF
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FIND_FILE_L:
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DUP
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LOADCP SHELL_NAME
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LOADC SHELLNAME_WORDS
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LOADCP _CMPWORDS ; compare names
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CALL
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CBRANCH.NZ FIND_F_FOUND ; exit loop if names match
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; check if current dirslot no
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; is below maximum number of slots
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LOAD SLOT_NO
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LOAD DIR_SIZE
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CMP GE
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CBRANCH FIND_F_NOTFOUND ; max slots reached, exit
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; add 1 to SLOT_NO
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LOAD SLOT_NO
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INC 1
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STORE SLOT_NO
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; address is still on stack
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LOADC DIRENTRY_SIZE
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ADD ; go to next dir entry
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; check if address is still
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; below end of data block
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DUP
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LOADCP CARD_BUF,512
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CMP LT
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CBRANCH FIND_FILE_L ; if it is below, loop
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DROP ; remove dir entry addr
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; block no is still on stack
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INC 1
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BRANCH FIND_FILE ; read next block
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FIND_F_NOTFOUND:
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LOADCP SHELL_ERR
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LOADCP PRINTLINE
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CALL
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; remove entry addr and block number
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DROP
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DROP
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LOADC 0
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JUMP
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FIND_F_FOUND:
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; found the file name, now check if it has the right flags
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; address of dir entry is still on stack
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DUP
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LOADC 40 ; add flags field offset
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ADD
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LOADI ; load flags
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LOADC 16 ; test for SlotFirst flag
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AND
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CBRANCH.Z FIND_FILE_L ; if not set, continue loop
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;LOADCP FOUND_MSG
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;LOADCP PRINTLINE
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;CALL
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; we got the right file, now calculate start block
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; and get file size from dir entry
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; address of dir entry is still on stack
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; phys start block = part start + slot_no * (extent_size/512)
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LOAD EXTENT_SIZE
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LOADC 9
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LOADCP _SHRM
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CALL
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LOAD SLOT_NO
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LOADCP _MUL
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CALL
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LOAD PART_START
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ADD
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;DUP
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;LOADCP PRINTHEXW
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;CALL
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;LOADC ' '
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;LOADCP CONOUT
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;CALL
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STORE PRG_START_BLK
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; address of dir entry is still on stack
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LOADC 44
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ADD ; add sizeBytes field offset
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LOADI ; get size in bytes
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;DUP
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;LOADCP PRINTHEXW
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;CALL
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;LOADCP NEWLINE
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;CALL
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STORE SIZE_BYTES
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; remove block number
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DROP
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; set argument count to 0
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; in case this gets called
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; by a terminating program
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LOADCP PARGCOUNT
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LOADC 0
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STOREI
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DROP
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LOADC 0 ; device id is always 0
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LOAD PRG_START_BLK
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LOAD SIZE_BYTES
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; release our stack frame
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FPADJ FIND_FS
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; load program
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LOADCP CORELOAD
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CALL
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LOADC 0
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JUMP
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.CPOOL
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.EQU SYSNAME_WORDS 4
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SYSPART_NAME:
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.WORD 6, 32
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.BYTE "SYSTEM"
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SYSPART_ERR:
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.BYTE "No ""SYSTEM"" partition.",13,10,10,0
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.EQU SHELLNAME_WORDS 5
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SHELL_NAME:
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.WORD 10,32
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.BYTE "shell.prog"
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SHELL_ERR:
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.BYTE "No shell on ""SYSTEM"" partition.",13,10,10,0
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FOUND_MSG:
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.BYTE " shell.prog ",0
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%include corelib.s
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