drewdevault

drewdevault, 16 days ago

Did nanosleep(2)

drewdevault, 16 days ago

To implement nanosleep I just improved the wait queues a bit until nanosleep could be done in 33 lines of code

drewdevault, 16 days ago

Will probably have to change a bit once I implement signals and have to deal with EINTR

drewdevault, 16 days ago

Call it 32 lines, that assert belongs somewhere else

drewdevault, 16 days ago

Block device files are now mounted, not that you can open them

drewdevault, 16 days ago

Right, now you can open them

drewdevault, 16 days ago

I think that's everything for day 13:

• O_CREAT support for openat
• Character and block devices, incl /dev/null, zero, full, and block devices and partitions
• Populate /dev with devices on boot
• Add idle task to scheduler
• New syscall: nanosleep

Next, in no particular order:

• Flesh out files a bit more (e.g. enforce O_RDONLY)
• Flesh out filesystem syscalls (mkdir, fstatat, etc)
• Signals & waitpid
• pipe(2), dup(2)
• Start writing a libc
• Port a shell

drewdevault, 16 days ago

Once I get all of those done, it's time to write a blog post about it and resume other projects!

drewdevault, 16 days ago

@lanodan I could port rc (and I might) but I'd like to do an ash derivative

drewdevault, 16 days ago

@JayT quite so

drewdevault, 16 days ago

@okflo oh god now I have to port doom to it

drewdevault, 16 days ago

Ended up with some extra free time tonight and did a couple more syscalls: unlinkat, mkdirat

Remaining filesystem-related syscalls are the stat family of calls, rmdirat (or AT_REMOVEDIR I guess), chmod/chown/chgrp, readlinkat, linkat, symlinkat, and utimensat.

drewdevault, 16 days ago

@jbowen https://git.sr.ht/~sircmpwn/bunnix

drewdevault, 16 days ago

Implemented a bunch of openat flags this morning: RDONLY/WRONLY/RDWR is now enforced, and O_DIRECTORY, O_APPEND, O_TRUNC, and O_EXCL are now supported

I chose to diverge from POSIX on O_DIRECTORY because I think it's kind of lame, but I could change my mind if this comes back to bite me when I start porting real-world software

drewdevault, 16 days ago

Also implemented an inode cache and reference counting for inodes 😃

drewdevault, 16 days ago

The cache currently serves just to make sure that there is a 1:1 correspondence between inode numbers and inode data structures (so that if several files hold a reference to the same inode they all remain in sync), it does not persist inodes after all references are released... yet. A broader cache system that keeps cached data in unused RAM is planned for the future.

drewdevault, 15 days ago

Signals 🤮

drewdevault, 15 days ago

waitpid

drewdevault, 15 days ago

@f4grx they're a better design, using O_DIRECTORY etc, imho. Particularly when it comes to implementing mountpoints. Simplifies things if you don't start from the assumption that you're always walking from the root

drewdevault, 15 days ago

many process, much wait

drewdevault, 15 days ago

@mxk what is sync_fd()? Do you mean fsync?

drewdevault, 15 days ago

@mxk I haven't implemented fsync and presently all writes are committed to disk before write(2) et al returns to userspace, so I'm not sure. I might know more when I get to that.

drewdevault, 15 days ago

@mxk @bugaevc I made it so that you can only open directories with O_DIRECTORY and they can only be O_RDONLY

drewdevault, 15 days ago

@bugaevc @mxk I guess that makes sense. We'll see what people are doing in the wild when I start porting software and it trips over this

drewdevault, 15 days ago

Okay, about done for today. Summary of day 14 writing a Unix clone:

New syscalls: exit, waitpid

Improvements to openat: enforces read/write mode, supports O_DIRECTORY, O_APPEND, O_TRUNC, O_EXCL, and O_CLOEXEC

Added an inode cache

Optimized the MMU code for fork and process clean-up (still no CoW, though)

And laid some groundwork for signals, which I have been dreading from the start.

https://git.sr.ht/~sircmpwn/bunnix