30 lines
1.2 KiB
Markdown
30 lines
1.2 KiB
Markdown
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# RoBootloader
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## Low Memory
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| start | end | use |
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|---------|---------|---------------------------|
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| 0x00000 | 0x004ff | BIOS stuff, don't touch |
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| 0x00500 | 0x06bff | _free space_ |
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| 0x06c00 | 0x07bff | **Bootloader stack** |
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| 0x07c00 | 0x07dff | Bootloader |
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| 0x07e00 | 0x07fff | _free space_ |
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| 0x08000 | 0x0ffff | **ELF file** (64 sectors) |
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| 0x10000 | 0x7ffff | **kernel space** |
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| 0x80000 | 0x9ffff | EDBA, partially usable |
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| 0xa0000 | 0xfffff | unusable |
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## Drive layout
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The first 512 bytes are the bootloader, right after that the 32-bit kernel ELF-file, this kernel can be 32KiB big. In the future, this "kernel" can be replaced by a second stage of the bootloader.
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## Known issues
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### USB Boot
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It doesn't boot the kernel from USB, as BIOS does not recognize USB as valid hard drive for int 13, only hard drives and floppies. Thus it loads sectors 2-65 from the hard drive. If this is written on a hard drive, it could work if DRIVE_ID is set correctly.
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### Stack setup
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As I don't quite get how segments work in real mode, there are most likely errors in the way I set up my stack. I'm going on a _it works on my qemu_ approach currently.
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