303 lines
7.8 KiB
Markdown
303 lines
7.8 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, mouse, 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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- PE import resolution and dynamic driver loading
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- Win32 personality (partial)
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- POSIX personality (partial)
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## how 2 build
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* open vs x64 build tools as admin
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* cd into this directory
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* `mkimage.bat`
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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) and FAT32.
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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 (because they're different)
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```
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"apps\shell.exe" -> current working directory
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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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The Win32 personality translates drive letters to drive numbers, the POSIX personality maps drives onto a tree.
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## screenshots
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<details><summary>Boot logs</summary>
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```
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BdsDxe: loading Boot0001 "UEFI QEMU HARDDISK QM00005 " from PciRoot(0x0)/Pci(0x4,0x0)/Sata(0x0,0xFFFF,0x0)
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BdsDxe: starting Boot0001 "UEFI QEMU HARDDISK QM00005 " from PciRoot(0x0)/Pci(0x4,0x0)/Sata(0x0,0xFFFF,0x0)
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1
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2
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3
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4
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Loading colonel.exe...
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Loading hal.dll...
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5
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6
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7
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8
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Found RSDP at: 0xF77E014
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9
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HAL: screen 1280x800
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HAL: FADT PM1a_CNT=0xb004 PM1b_CNT=0x0000 DSDT=0x0f77a000
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HAL: _S5_ SLP_TYP_A=0x00 SLP_TYP_B=0x00
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HAL: LAPIC=00000000fee00000 IOAPIC=00000000fec00000 HPET=00000000fed00000
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HAL: lapicPhys=0xFEE00000, lapicVirt=0xFFFF8800FEE00000, hpetPhys=0xFED00000
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HAL: Attempting to calibrate APIC timer via HPET...
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HAL: APIC timer: 62981 ticks/ms
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HAL: initialisation complete.
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KernelMain: Handing over to scheduler...
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SystemInitThread: Thread started. Igniting the system...
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InitializeDrivers: Initializing drivers...
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InitializeDrivers: Executing DriverEntry for ide.sys
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IDE: Init
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IDE: No drive on primary channel
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InitializeDrivers: Driver ide.sys failed to init!
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InitializeDrivers: Executing DriverEntry for ahci.sys
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AHCI: driver loading...
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AHCI: controller at PCI 00:04.0
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AHCI: PCI IRQ line = 11
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AHCI: ABAR phys=0x81060000 version=0x00010000
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AHCI: cap=0xc0141f05 ports=6 slots=32 64bit=1
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AHCI: port 0: link up, initializing...
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AHCI: port COMRESET done: sig=0x00000101 ssts=0x00000113
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AHCI: drive 0: 524288 sectors (256 MB)
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AHCI: drive 0 registered
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AHCI: port 1: no link (ssts=0x00000000)
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AHCI: port 2: no link (ssts=0x00000000)
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AHCI: port 3: no link (ssts=0x00000000)
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AHCI: port 4: no link (ssts=0x00000000)
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AHCI: port 5: no link (ssts=0x00000000)
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AHCI: ISR registered on IRQ 11; initialised 1 drive(s)
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InitializeDrivers: Executing DriverEntry for fat32.sys
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FAT32: Init
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FAT32: Init complete (status=0, clusters=128480).
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Found runtime driver: usb.sys
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Test runtime driver
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SystemInitThread: Loading system DLLs...
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Memory Status:
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-> Free (PMM): 151.71 MB
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-> Kernel Pool: 4.00 MB
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-> User Heap: 0.55 MB
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LaunchUserProcess: IoOpenFile: 0
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LaunchUserProcess: IoGetFileSize: 5120
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LaunchUserProcess: MmAllocateUserMemory: 0x8E020
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LaunchUserProcess: IoReadFile: 0
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LaunchUserProcess: IoCloseFile
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Created process (PID 2) with command line: init.exe
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LaunchUserProcess: PE Image mapped! Base 0x90020, Entry 0x91600
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LaunchUserProcess: Thread created and queued!
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[init] starting
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[init] waiting
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shell: ready
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> help
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Available commands:
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help - Show this list
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dir - List files
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cd <path> - Change directory
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type <file> - Display file contents
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del <file> - Delete a file
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write <file> <tx> - Create a file with text
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exit - Close the shell
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> dir
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System Volume Information
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drivers
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efi
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colonel.exe
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hal.dll
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syscall.dll
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win32.dll
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posix.dll
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init.exe
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shell_win32.exe
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shell_posix.exe
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shell_native.exe
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doom.exe
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video.exe
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boot.ini
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bink2w64.dll
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video.bk2
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doom1.wad
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> shell_win32.exe
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shell: ready
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shell_win32.exe
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> doom.exe
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doom: starting
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getenv: Unknown variable DOOMWADDIR
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DOOM Shareware Startup v1.10
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V_Init: allocate screens.
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M_LoadDefaults: Load system defaults.
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Z_Init: Init zone memory allocation daemon.
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W_Init: Init WADfiles.
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adding ./doom1.wad
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===========================================================================
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Shareware!
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===========================================================================
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M_Init: Init miscellaneous info.
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R_Init: Init DOOM refresh daemon - [.. ]
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InitTextures
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InitFlats........
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InitSprites
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InitColormaps
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R_InitData
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R_InitPointToAngle
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R_InitTables
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R_InitPlanes
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R_InitLightTables
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R_InitSkyMap
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R_InitTranslationsTables
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P_Init: Init Playloop state.
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I_Init: Setting up machine state.
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I_InitSound: I_InitSound: pre-cached all sound data
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I_InitSound: sound module ready
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D_CheckNetGame: Checking network game status.
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startskill 2 deathmatch: 0 startmap: 1 startepisode: 1
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player 1 of 1 (1 nodes)
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S_Init: Setting up sound.
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S_Init: default sfx volume 8
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HU_Init: Setting up heads up display.
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ST_Init: Init status bar.
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doom: entering game loop
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I_ShutdownSound: NOT finishing pending sounds
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> shell_posix.exe
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shell: ready
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> help
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Available commands:
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help - Show this list
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dir [path] - List directory contents
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cd <path> - Change directory
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type <file> - Display file contents
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del <file> - Delete a file
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write <file> <txt> - Create a file with text
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exit - Close the shell
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> dir
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System Volume Information
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drivers
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efi
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colonel.exe
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hal.dll
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syscall.dll
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win32.dll
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posix.dll
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init.exe
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shell_win32.exe
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shell_posix.exe
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shell_native.exe
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doom.exe
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video.exe
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boot.ini
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bink2w64.dll
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video.bk2
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doom1.wad
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.doo
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> video.exe
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video: starting
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video.exe
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video: video.bk2 loaded
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shell: goodbye
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> exit
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shell: goodbye
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> exit
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shell: goodbye
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> exit
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shell: goodbye
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[init] done
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ProcessWatcherThread: Process "init.exe" (PID 2) exited with code 0.
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ProcessWatcherThread: Shutting down.
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```
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</details>
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## faq
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Q: Why?
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A: Learning. Fun.
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Q: Does it run Doom?
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A: `doom.exe`
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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: It shouldn't.
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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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