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* 7390 - null interrupt tablesKartik Agaram2020-12-231-11/+69
| | | | | Looks like the reset loops stop if we create null handlers for the first 10 indexes in the IDT.
* 7389 - snapshotKartik Agaram2020-12-231-6/+6
| | | | | | | | | | | | | Ok, we're back at the reset loop. Let's keep going; maybe having a decent keyboard handler will fix it. The bug I fixed here was caused by misunderstanding what m16&32 mean in the Intel manual. It's still a regular regmem operand that uses all of the ModR/M byte (which can be interpreted in 16-bit mode, adding to the complication). It's just constrained to not allow direct addressing (mod 00). I needed to better internalize the format of the instruction set references at the start of Volume 2, Chapter 3.
* 7388 - snapshot initializing interrupt tableKartik Agaram2020-12-231-24/+69
| | | | | | | | | | | | | | | | | | | | | | | | | I'm now back at the state of commit 7382 (including 7376). The existing print to screen surprisingly seems to work without reset-looping, but when I step through I notice that the lidt isn't doing what I expect. Desired: at address 0x7cce, the processor executes: 0f 01 1e 00 7f # lidt ds:*idt_descriptor Observed: at address 0x7cce, the processor executes: 0f 01 1e # lidt ds:*esi As a result the next instruction is: 00 7f fb So the `fb` isn't interpreted to enable interrupts. So the problem of commit 7376 is latent. Past this point the instruction stream is lined up again, and everything occurs as it should. Purely by chance. I fully expect all hell to break loose again, like it did in commit 7376, once I debug the lidt encoding. There's still something I don't understand about enabling interrupts. Perhaps I need to fill in more entries in the table.
* 7387Kartik Agaram2020-12-231-3/+4
| | | | | | Redo commit 7381. There was a bug. Current state: commit 7381 excluding 7376.
* 7386Kartik Agaram2020-12-231-2/+3
| | | | Commit 7380 excluding 7376.
* 7385Kartik Agaram2020-12-231-6/+6
| | | | Commit 7379 excluding 7376.
* 7384Kartik Agaram2020-12-231-4/+23
| | | | | Currently at commit 7378 (reset the A20 address line) except without 7376 (enabling interrupts).
* 7383Kartik Agaram2020-12-231-101/+36
| | | | | Currently at commit 7377 except without 7376 (enabling interrupts). Works as advertised.
* 7382 - snapshotKartik Agaram2020-12-231-21/+62
| | | | | Turns out I've been "testing" with a stale file since commit 7373. We need to go over everything since then.
* 7381Kartik Agaram2020-12-231-3/+3
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* 7380Kartik Agaram2020-12-231-2/+3
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* 7379Kartik Agaram2020-12-231-6/+6
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* 7378Kartik Agaram2020-12-231-4/+23
| | | | | | | | Turns out we only had access to 50% of RAM so far. Closing my nose and moving right along.. Though this _does_ give me practice interacting with ports. That'll be handy for the keyboard.
* 7377Kartik Agaram2020-12-231-5/+5
| | | | | | | Ooh, look at that, the device number comes conveniently initialized in the right register. No need to hardcode it. https://wiki.osdev.org/MBR_(x86)
* 7376Kartik Agaram2020-12-231-3/+7
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* 7375Kartik Agaram2020-12-231-9/+20
| | | | A little more robustness after reading https://stackoverflow.com/questions/43786251/int-13h-42h-doesnt-load-anything-in-bochs/43787939#43787939
* 7374Kartik Agaram2020-12-211-3/+16
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* 7373Kartik Agaram2020-12-211-1/+1
| | | | | apps/boot.hex doesn't need much by way of syntax highlighting. Have it work even for people who haven't installed subx.vim
* 7372 - successful read from disk using BIOSKartik Agaram2020-12-211-13/+48
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* 7371Kartik Agaram2020-12-211-1/+1
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* 7370Kartik Agaram2020-12-212-7/+8
| | | | Use a more realistically sized disk image. Now we can read the second sector.
* 7369 - read hard disk using BIOSKartik Agaram2020-12-202-8/+2
| | | | | | There were two problems: a) We have only 1 sector per track (spt=1), so 'second sector' is meaningless. b) Drives 0-127 are reserved for floppies.
* 7368 - ooh, int 13h works with a floppyKartik Agaram2020-12-201-0/+6
| | | | | Lots of great tips here: https://stackoverflow.com/questions/43786251/int-13h-42h-doesnt-load-anything-in-bochs/43787939#43787939
* 7367 - start of boot sector for Mu computerKartik Agaram2020-12-202-0/+191
| | | | | Not working yet. Reading sectors from disk returns an error (sets carry flag).
* 7366Kartik Agaram2020-12-201-22/+24
| | | | | | Move more padding around. Reading a sector from disk requires about 24 bytes of code.
* 7365Kartik Agaram2020-12-201-4/+4
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* 7364Kartik Agaram2020-12-201-11/+12
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* 7363Kartik Agaram2020-12-201-1/+1
| | | | | Kinda brutal way to lose the bochs warning. Should suffice for now. As we add more code we'll introduce more sectors.
* 7362Kartik Agaram2020-12-201-2/+2
| | | | | I hadn't noticed that bochs was getting into a reset loop after executing my code correctly. Fix that.
* 7361Kartik Agaram2020-12-201-2/+2
| | | | | Switch bochs from floppy to hard disk. Bochs throws a new warning, but otherwise 32bit.hex continues to work.
* 7360Kartik Agaram2020-12-201-13/+21
| | | | | Insert padding in a few places so we don't have to recalculate addresses quite so much.
* 7359 - boot into 32-bit modeKartik Agaram2020-12-201-6/+6
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* 7358Kartik Agaram2020-12-202-0/+208
| | | | | | | Snapshot: first draft of a boot image that switches to 32-bit mode as quickly as possible (~70 bytes) Doesn't work yet. Gets stuck in an infinite reset loop.
* 7357Kartik Agaram2020-12-191-74/+65
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* 7356Kartik Agaram2020-12-195-121/+115
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* 7355 - learning to boot into 32-bit modeKartik Agaram2020-12-1910-0/+351
| | | | | | These exercises are from the incomplete "Writing a simple operating system from scratch" by Nick Blundell. https://www.cs.bham.ac.uk/~exr/lectures/opsys/10_11/lectures/os-dev.pdf
* 7354 - tile: stop trying to center menuKartik Agaram2020-12-141-15/+7
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* 7353Kartik Agaram2020-12-141-1/+1
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* 7352Kartik Agaram2020-12-143-37/+15
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* 7351Kartik Agaram2020-12-141-1/+1
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* 7350 - mu.subx optimization: skip no-op copiesKartik Agaram2020-12-112-0/+141
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* 7349Kartik Agaram2020-12-111-12/+12
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* 7348 - mu.subx bug with string literalsKartik Agaram2020-12-112-0/+63
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* 7347 - tile: separate sandbox and function menusKartik Agaram2020-12-061-0/+38
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* 7346Kartik Agaram2020-12-061-2/+25
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* 7345Kartik Agaram2020-12-061-14/+14
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* 7344Kartik Agaram2020-12-061-3/+15
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* 7343Kartik Agaram2020-12-061-5/+4
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* 7342 - tile: hotkeys for ending function editKartik Agaram2020-12-061-0/+20
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* 7341 - tile: function editing doneKartik Agaram2020-12-062-22/+6
| | | | | A tiny modicum of reuse amidst all this copypasta: I'm able to reuse the same function that renders lines without stacks in the sandbox.
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