AnachronautandClaude Opus 5
000a6d39cb
Dispatching through a vector with nothing in it was the one fault this machine could not hand over, because the thing that would hand it over is the thing that has just found nothing to hand it to. It stopped the machine and no program could do anything about it - so calling a service the system does not implement was fatal, and that is an ordinary mistake to make. Two new fault vectors: 5 when a software vector was empty, 6 when a device interrupted and its hardware entry was. Separate, because they are separate mistakes with separate fixes - one is a program calling something that is not there, the other a program that asked to be interrupted and forgot the handler. WHICH ENTRY WAS EMPTY ARRIVES IN Q, and it is the only thing on this machine a handler is given in a register. Not a fault cause register by another route: the vector still says what happened and Q says which of the 256 entries it happened about, which is a parameter and not a cause. It costs no new state at all, because the frame already saved the Q the interrupted program had and RETI puts it back. The escalation happens once. If vector 5 or 6 is itself empty the machine stops the way it always did, having genuinely run out of places to go. swiFaultTest is what guards that, and it was written long before any of this: it installs nothing, so it must still get the old halt. Breaking the escalation fails the two new tests and not that one; making the escalation unbounded fails that one and not the two new ones. Each break fails exactly the half it belongs to. noDeviceTest is fed no input on purpose. The console raises its line once when input ENDS as well as when a byte arrives - which exists so a program driven by interrupts is told when nothing more is coming - so with no input at all, that end is what turns up. Groundwork for CosmOS's fault screen, which wanted to catch these two and could not. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
52 lines
1.4 KiB
NASM
52 lines
1.4 KiB
NASM
; A device raising its line with nothing installed to answer it, CAUGHT.
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;
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; The other half of the fault that could not be handed over. A program that asks a device to
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; interrupt it and then forgets the handler used to stop the machine dead; now it goes to a
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; vector of its own with the port in Q, so the program can say which device it was that
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; nobody was listening to.
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;
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; NOTHING IS TYPED AT THIS. The console raises its line once at the end of input as well as
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; for an arriving byte - which is exactly so that a program driven by interrupts is told when
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; nothing more is coming - and the test is run with no input at all, so that end is what
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; arrives.
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;
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; Correct output is:
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; nobody listening on port 00
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; and a clean halt.
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#Include console.asm
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#Program
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start:
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INIA 0x02 ; Interrupt when the console has something to say.
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OUTA 0x02
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SIF
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spin:
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; Never touches the console. Whatever happens below is something that interrupted this.
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BRI spin
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; Q holds the port whose entry was empty. The console is port zero.
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nobody:
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SETD.0 NobodyText
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CALL printString
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MVQA
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CALL printByteHex
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CALL newLine
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; The console back to how it was found, so nothing else is asked for, and stop. There is
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; nothing to resume to: the loop above only exists to be interrupted.
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RSTA
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OUTA 0x02
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HALT
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#Data
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NobodyText:
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"nobody listening on port "
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#Vectors
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Boot start
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NoDevice nobody
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