48 lines
1.8 KiB
Markdown
48 lines
1.8 KiB
Markdown
# 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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## Bootsector layout
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(all addresses are offsets from 0x7C00)
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| start | end | use |
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|--------|--------|-------------------|
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| 0x0000 | ? | Bootloader code |
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| ? | 0x0193 | _padding_ |
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| 0x0194 | 0x01bd | SFS header |
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| 0x01be | ? | _padding_ |
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| ? | 0x01fd | data |
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| 0x01fe | 0x01ff | 0x55AA boot magic |
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## Hard Drive layout
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| start | end | use |
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|--------|--------|--------------------------------------------|
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| 0x0000 | 0x01ff | Bootloader code (including SFS superblock) |
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| 0x0200 | 0x81ff | SFS reserved area (kernel ELF file) |
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| 0x8200 | 0x???? | SFS data area |
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| 0x???? | 0x???? | SFS free area |
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| 0x???? | end | SFS index area |
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## Known issues
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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 machine_ approach currently.
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### Kernel is not a file
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I reserve 32KiB of SFS reserved area for the ELF file of the kernel. This is currently for "historic reasons" (a.k.a. I'm too lazy to load the filesystem in the bootloader). The kernel then handles the filesystem.
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