readme enhancement
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@@ -1,8 +1,8 @@
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# NT-Lite -- an x86-64 kernel
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## The Monster From ~~Redmond~~ Cracow
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“Not only is UNIX dead, it’s starting to smell really bad.” - Rob Pike
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Boots. Runs processes. Loads drivers. Plays video. Runs Doom. Has opinions.
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“UNIX has three operations: read, write, and lie through ioctl.”
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## what is it?
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@@ -55,28 +55,8 @@ Single address space for the whole system. No separate kernel/user page tables.
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Kernel lives in the higher half. User processes only see what they are explicitly given. Kernel pages are supervisor-only so user-mode code cannot touch them. User pages are isolated from each other through the allocator and process creation path, not by hardware address-space separation. One rogue pointer can't crash the kernel but it might corrupt other processes. But what are the chances?
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Is this how a serious modern OS should isolate processes? No.
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Is it very convenient while building? Absolutely.
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### boot chain
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Bootloader loads config, pulls in the core images, sets up the higher-half mapping, then jumps to `KernelMain`.
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From there:
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```text
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HAL init
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interrupts
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paging
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scheduler
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boot drivers
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filesystems
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runtime drivers
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self-tests
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init.exe
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shell
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```
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### execution model
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NT-Lite has a Windows-flavored execution model, but a simplified one.
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@@ -104,8 +84,6 @@ The important bit:
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interrupt -> DPC -> IoCompleteRequest -> APC -> alertable wait/user callback
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```
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That is a real path, not a TODO scribbled in the margin.
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### I/O and filesystems
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Everything goes through the VFS. Disk access, filesystem parsing, path resolution, and process personalities are separate layers instead of one giant bowl of sadness.
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@@ -144,7 +122,7 @@ Currently shipping:
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```text
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AHCI interrupt-driven SATA
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IDE PIO/DMA
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FAT32 filesystem driver with VFAT long filename support
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FAT32 filesystem driver with VFAT and all
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```
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### processes, threads, and syscalls
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@@ -191,8 +169,6 @@ if (s == SYS_STATUS_PENDING)
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If the request completes by user APC, the alertable wait returns `SYS_STATUS_USER_APC`, the callback runs in user mode, and the original execution continues afterward.
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That sentence used to be science fiction. Now it is boring. Excellent.
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## paths
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```text
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@@ -204,9 +180,8 @@ That sentence used to be science fiction. Now it is boring. Excellent.
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"/1/apps/video.exe" -> volume 1
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```
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Volumes `0`-`7` are available. A volume only works if a filesystem is registered on it. The Win32 personality translates drive letters to volume numbers, while the POSIX personality maps volumes onto a tree.
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`0:/` is a mounted namespace, not a Windows path. It merely enjoys cosplay.
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Volumes `0`-`7` are available. A volume only works if a filesystem is registered on it (duh).
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The Win32 personality translates drive letters to volume numbers, while the POSIX personality maps volumes onto a tree.
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## how to build
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@@ -247,20 +222,14 @@ apps/
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video.exe
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```
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## known truths
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- FAT32 works well enough to save `.doomrc` properly.
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- Doom runs.
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- Video playback works.
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- Async file I/O exists.
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- Process isolation is not strong.
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- This is not production software.
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- This is absolutely the wrong way to spend a weekend.
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## screenshots
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## TODO
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todo
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## faq
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Q: Why?
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@@ -269,29 +238,29 @@ A: Learning. Fun. Spite.
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Q: Does it run Doom?
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A: `doom.exe`
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Q: Does Doom save its config correctly?
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A: Yes. `.doomrc`, not cursed `.DOO` nonsense. VFAT forever!
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Q: Can you read and write files?
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A: As far as I'm aware.
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Q: Does it have async I/O?
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A: Yes. Events, IOSBs, user APC callbacks, cancellation. Very suspiciously serious.
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A: You didn't read the features list?
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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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A: Depends how you frame it. Some apps will run, most will not.
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Q: Are processes isolated?
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A: No. But IPC is free.
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Q: How often does it crash?
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A: Less often than before, which is how civilizations begin.
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A: Less often than before.
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Q: Can it recover from a crash?
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A: Usually. Unless the kernel shat itself.
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A: Yes. Unless the kernel faulted.
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Q: Is this finished?
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A: No. And it never will be.
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Q: Will it corrupt my data?
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A: It should not.
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A: It shouldn't.
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Q: Why is the path syntax so weird?
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A: It makes sense to me.
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@@ -300,7 +269,7 @@ Q: Why are the logs so verbose?
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A: How else do I debug it?
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Q: What should I read first?
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A: This document. Then the scheduler. Then whatever hurt you last.
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A: This document.
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Q: Can I use this in production?
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A: Don't.
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