Anachronaut
cd5f548736
Three blocks move and nothing else changes. Branches take 0x60, subroutines take 0x70, and the ALU moves up into the 0x10 block the two of them used to share. Order within each block is preserved exactly - this relocates them, it does not rethink them. WHAT IT BUYS IS AN EMPTY 0x00 TO 0x0F. Program Memory that was never written, or a load that stopped part way and left zeroes in its tail, used to read as a long run of ADDs: the machine carried on through them, arrived somewhere unpredictable, and whatever broke there was a long way from the byte that caused it. Now it faults where it is met: Fault: 0x00 at Program Address 0x0004 is not an instruction. That is the address of the byte after the last real instruction, which is the difference between a diagnosis and a search. Reserving the whole nibble rather than just 0x00 means a run into blank memory faults wherever it starts rather than only when it lands on the right byte. runOffTest records it, and the block is left empty for whatever turns out to want it. The other half is room: branches and subroutines had filled 0x10 to 0x1F between them, so a service return that keeps Q and DP3 had nowhere to sit next to its family. It has 0x76 waiting now. Five places wrote an opcode down that the scripted remap did not reach, and four of them were found by tests rather than by looking: - secondPass.c lists which opcodes take an address, and firstPass.c knows SWI by number. Missing those made XOR read as a branch. - Asm.asm knows SWI by number too, being the other assembler. Missing it made the native and host assemblers disagree byte for byte, which is exactly the check that exists to catch a thing known in two places. - loaderTest.asm carries a hand written payload, and its RETI was 0x19. To the assembler those are numbers and to the program they are data, so nothing but running it could notice. It says so in a comment now. - The Assembler Manual prints the bytes hello.asm assembles to, and two of them were branches. The monitor's recorded disassembly moved by exactly the bytes it should: 18 became 72 wherever SWI appears, with SETD and INIB untouched and every disassembled line still reading the same.
43 lines
1.6 KiB
Plaintext
43 lines
1.6 KiB
Plaintext
CosmOS
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> x examine, d disassemble, a assemble, s set, b bank, g go, exit leaves
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* b <program|data|number>
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* there is no such bank
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* loaded, starting at 4000
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* bank 00
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* 4000 47 00 20 00 SETD.0 2000
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4004 72 10 SWI 10
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4006 47 00 20 44 SETD.0 2044
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400A 72 10 SWI 10
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400C 47 00 20 7A SETD.0 207A
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4010 27 1F INIB 1F
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4012 72 11 SWI 11
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4014 47 00 20 5D SETD.0 205D
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* 4000 47 00 20 00 72 10 47 00 20 44 72 10 47 00 20 7A G. .r.G. Dr.G. z
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4010 27 1F 72 11 47 00 20 5D 72 10 47 00 20 7A 72 10 '.r.G. ]r.G. zr.
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4020 47 00 20 65 72 10 72 12 00 00 00 00 00 00 00 00 G. er.r.........
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4030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
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* bank 01
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* 2000 61 20 70 72 6F 67 72 61 6D 2C 20 6C 6F 61 64 65 a program, loade
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2010 64 20 6F 66 66 20 61 20 64 69 73 6B 2C 20 72 75 d off a disk, ru
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2020 6E 6E 69 6E 67 20 6F 6E 20 74 68 65 20 73 79 73 nning on the sys
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2030 74 65 6D 20 74 68 61 74 20 6C 6F 61 64 65 64 20 tem that loaded
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* bank 02
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* 0000 01 FF 00 00 00 00 00 00 01 FF 00 00 00 00 00 00 ................
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0010 03 FF 08 00 00 00 00 00 01 20 01 00 00 00 00 00 ......... ......
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0020 00 FF 00 00 00 00 00 00 00 FF 00 00 00 00 00 00 ................
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0030 00 FF 00 00 00 00 00 00 00 FF 00 00 00 00 00 00 ................
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* that bank will not be written
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* bank 00
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* * 8000 26 48 INIA 48
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8002 D1 00 OUTA 00
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8004 26 0A INIA 0A
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8006 D1 00 OUTA 00
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8008 18 SHR
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8009 12 AND
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800A 00 ?
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800B 00 ?
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* Fault: 0x00 at Program Address 0x800A is not an instruction.
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H
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Execution halted.
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[exit 1]
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