Notices by Drew DeVault (drewdevault@fosstodon.org), page 5

Getting lwext4 to actually write changes to the disk is turning out to be a bit involved

Day 12 of making a Unix clone

New syscalls: getdents, fexecve

Fleshed out the filesystem implementation via os:: in the Bunnix port of the Hare stdlib

Some more inode refactoring done

(f)execve(2) now populates auxilary vector of new process

Next: stat/fstat/fstatat, respect/enforce open flags and file modes (e.g. O_WRONLY on a file with -w should not work, implement O_DIRECTORY, etc)

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

Call it 32 lines, that assert belongs somewhere else

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

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

Character special device files baby!

Answer: turns out it was a bug in the AHCI driver. Took me ages to figure that out.

Spent most of the day failing to get O_CREAT to work on ext4, further investigation tomorrow

many process, much wait

waitpid

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.

Also implemented an inode cache and reference counting for inodes 😃

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

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.

Today's mood

I need to implement an idle task so that the kernel doesn't crash when all processes are blocked, but I don't want to touch the scheduler again

Day 19 -- going to Utrecht tonight so there's not going to be much

* dash incorporated into source tree to provide /bin/sh
* New syscalls: setcreds (provides setuid et al), setgroups, mount
* libc expanded with support for passwd, groups, shadow, etc, login(1) stuff
* Bunnix executes /etc/rc on boot as a shell script

I have realized that dash depends on signals to work properly, however, so I will probably have to either get that working or switch to rc.

✓ idle

Hopefully I don't have to touch the scheduler again until SMP

Next up... block special devices. I really need to do signal but blockdevs will let me procrastinate on that

Could do sleep(2) as well

Today:

/dev/cons
/dev/kbd