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mu/README.baremetal.md

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7403 - baremetal/ for apps without a kernel
2020-12-26 21:22:28 +00:00
Some apps written in SubX and Mu. Where the rest of this repo relies on a few
Linux syscalls, the apps in this subdirectory interface directly with hardware.
7419
2020-12-27 06:56:44 +00:00
We still need the top-level and apps to build them.
7404 - baremetal: first example program Design choice: all programs will use a graphics mode (1280x1024) with 256 colors. That should be fairly widely available. (It turns out text modes larger than 80x25 are not widely available even among modern emulators. Mu will need fonts sooner rather than later.) Mu will never try to be smart and do things like autodetect your hardware. We _will_ help you modify Mu for your hardware.
2020-12-26 22:21:04 +00:00
I'd like to eventually test these programs on real hardware, and to that end
they are extremely parsimonious in the hardware they assume:
7406
2020-12-26 23:34:10 +00:00
7410
2020-12-27 01:35:16 +00:00
0. Lots (more than 640KB/1MB[1]) of RAM
7424 - baremetal: downsize graphics resolution If it's large enough that I have doubts whether my top-of-the-line Mac is showing the bottom of the screen inside an emulator, it's too large. This way I also feel more confident that most modern hardware will support this graphics mode, and that these programs will work for others.
2020-12-27 16:33:22 +00:00
1. Pure-graphics video mode (1024x768 pixels) in 256-color mode. At 8x8
7423
2020-12-27 16:03:48 +00:00
pixels per grapheme, this will give us 160x128 graphemes. But it's still
an open question if it's reasonably widely supported by modern hardware.
If it isn't, I'll downsize.
7567 - baremetal: shift-key support
2021-01-28 03:34:50 +00:00
2. Keyboard. Just a partial US keyboard for now. Main qwerty zone only. No
number pad, no function keys, no ctrl/alt/meta/fn/super/capslck/numlck.
7404 - baremetal: first example program Design choice: all programs will use a graphics mode (1280x1024) with 256 colors. That should be fairly widely available. (It turns out text modes larger than 80x25 are not widely available even among modern emulators. Mu will need fonts sooner rather than later.) Mu will never try to be smart and do things like autodetect your hardware. We _will_ help you modify Mu for your hardware.
2020-12-26 22:21:04 +00:00
That's it:
* No wifi, no networking
* No multitouch, no touchscreen, no mouse
7423
2020-12-27 16:03:48 +00:00
* No graphics acceleration
7404 - baremetal: first example program Design choice: all programs will use a graphics mode (1280x1024) with 256 colors. That should be fairly widely available. (It turns out text modes larger than 80x25 are not widely available even among modern emulators. Mu will need fonts sooner rather than later.) Mu will never try to be smart and do things like autodetect your hardware. We _will_ help you modify Mu for your hardware.
2020-12-26 22:21:04 +00:00
* No virtual memory, no memory reclamation
7406
2020-12-26 23:34:10 +00:00
7407
2020-12-27 00:37:10 +00:00
Just your processor, gigabytes of RAM[1], a moderately-sized monitor and a
7423
2020-12-27 16:03:48 +00:00
keyboard. (The mouse should also be easy to provide.)
7404 - baremetal: first example program Design choice: all programs will use a graphics mode (1280x1024) with 256 colors. That should be fairly widely available. (It turns out text modes larger than 80x25 are not widely available even among modern emulators. Mu will need fonts sooner rather than later.) Mu will never try to be smart and do things like autodetect your hardware. We _will_ help you modify Mu for your hardware.
2020-12-26 22:21:04 +00:00
7423
2020-12-27 16:03:48 +00:00
We can't yet read from or write to disk, except for the initial load of the
program. Enabling access to lots of RAM gives up access to BIOS helpers for
the disk.
These programs don't convert to formats like ELF that can load on other
operating systems. There's also currently no code/data segment separation,
just labels and bytes. I promise not to write self-modifying code. Security
and sandboxing is still an open question.
7404 - baremetal: first example program Design choice: all programs will use a graphics mode (1280x1024) with 256 colors. That should be fairly widely available. (It turns out text modes larger than 80x25 are not widely available even among modern emulators. Mu will need fonts sooner rather than later.) Mu will never try to be smart and do things like autodetect your hardware. We _will_ help you modify Mu for your hardware.
2020-12-26 22:21:04 +00:00
7559 - reorganize sectors built in raw hex This was tedious for three reasons beyond the usual one of having to track and update offsets several time while I debug: - The Bochs troubles of the previous commit kept polluting my brain even though they were irrelevant. - I had to keep some changes locally to allow myself to use Bochs, which polluted my working directory. - I had to travel the long way to the realization that I'm not actually initializing the stack anywhere. BIOS was starting my stack off at 0x10000, which was promptly clobbered by my second read from disk. The good news: while I'm here I grow the interrupt descriptor table. So I don't have to go through this exercise when I get back to supporting the mouse.
2021-01-25 03:38:10 +00:00
Programs start executing at address 0x9400. See baremetal/boot.hex for
7519 - baremetal: run all tests on boot
2021-01-14 05:50:38 +00:00
details.
Mu programs always run all their automated tests first. `main` only runs if
there are no failing tests. See baremetal/mu-init.subx for details.
7404 - baremetal: first example program Design choice: all programs will use a graphics mode (1280x1024) with 256 colors. That should be fairly widely available. (It turns out text modes larger than 80x25 are not widely available even among modern emulators. Mu will need fonts sooner rather than later.) Mu will never try to be smart and do things like autodetect your hardware. We _will_ help you modify Mu for your hardware.
2020-12-26 22:21:04 +00:00
So far the programs have only been tested in Qemu and Bochs emulators.
7407
2020-12-27 00:37:10 +00:00
7408
2020-12-27 00:38:01 +00:00
[1] Though we might need to start thinking of [the PC memory map](https://wiki.osdev.org/Memory_Map_(x86))
7528 - heap allocator
2021-01-16 18:40:37 +00:00
as our programs grow past the first 32MB of memory. Mu doesn't yet make any
attempt to understand how much RAM the underlying computer has. Also, writing
to random locations can damage hardware or corrupt storage devices.