116 lines
2.8 KiB
Markdown
116 lines
2.8 KiB
Markdown
# NT-Lite -- an x86-64 kernel
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Boots. Runs processes. Mimics Windows to some extent.
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## what is it?
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A 64-bit operating system kernel written from scratch.
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UEFI bootloader, physical and virtual memory managers, preemptive scheduler, HAL, VFS, PE loader, partial Win32 layer.
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It boots into a shell.
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~20k lines of C and assembly.
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## features
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- UEFI bootloader
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- physical memory manager
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- virtual memory manager with kernel pool
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- HAL (screen, keyboard, timer, disk, PCI, APIC)
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- preemptive scheduler with priority levels
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- processes and threads
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- VFS with IRPs
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- drive-letter paths (`0:\apps\shell.exe`)
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- INI-based boot and driver configuration
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- partial Win32 layer (kernel32 and user32, capable of running simple windows apps)
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- PE import resolution and dynamic driver loading
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## how 2 build
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* open env variables
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* set `NTLITE_DRIVE` as your thumbdrive (ex. `G:`)
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* set `NTLITE_NTPATH` as your thumbdrive (ex. `\\.\PhysicalDrive7`)
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* open vs x64 build tools
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* cd into this directory
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* `build.bat`
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* `run.bat`(ide)/`rund.bat`(ide, debug)/`runa.bat`(ahci)/`runad.bat`(ahci, debug)
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* enjoy
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## how it looks when built
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I have some strong opinions on OS design.
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```
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efi/boot/
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bootx64.efi
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boot.ini
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hal.dll
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colonel.exe
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drivers/
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drivers.ini
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ide.sys
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ahci.sys
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fat32.sys
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syscall.dll
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win32.dll
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posix.dll
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shell.exe
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video.exe
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```
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## driver model
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drivers are PE32+ `.sys` files with an entry point preferably named DriverEntry accepting a constant pointer to HAL_API.
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drivers to be loaded have their path stored in `drivers.ini`, split into essential for boot (loaded by bootloader) and not required for boot (loaded by kernel).
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a disk driver fills in a `DISK_DRIVER` vtable and calls `IoRegisterDisk(index, &driver)`.
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a filesystem driver fills in an `IO_FILESYSTEM` vtable and calls `IoRegisterFilesystem(index, &fs, &vol)`.
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currently shipping: AHCI (interrupts), IDE (PIO/DMA), FAT32 (read-only).
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## how it boots
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1. UEFI loads `boot.ini`, reads `drivers.ini`
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2. bootloader maps kernel, HAL, and boot drivers into the upper half
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3. direct physical window at `0xFFFF880000000000`
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4. jumps to `KernelMain`
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5. PMM, VMM, GDT, IDT, HAL, IRQs, scheduler
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6. loads runtime drivers from disk
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7. launches `shell.exe`
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## paths
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```
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"apps\shell.exe" -> drive 0
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"0:\apps\shell.exe" -> drive 0
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"2:\data\config.ini" -> drive 2
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```
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drives 0–7. a drive only works if a filesystem registered on it.
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## screenshots
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## faq
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Q: Why?
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A: Why not?
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Q: Does it run Doom?
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A: Not yet.
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Q: Is the Win32 layer real?
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A: Real enough to load binaries that expect it. Not real enough to run Notepad.
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Q: Is the scheduler preemptive?
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A: As much as it will ever be.
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Q: Will it corrupt my data?
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A: How would it? It's read-only.
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Q: Is this finished?
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A: Not in the slightest.
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Q: Can I use this in production?
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A: Don't.
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