rm -r fails to remove directories

[SomeDevHere]

Expected Result Directory is deleted

Actual Result Directory is kept and rm fails with Is a directory

Steps To Reproduce

1. Create an empty directory mkdir tmp
2. Delete the directory rm -r tmp

Xtrace Log xtrace.log

Additional Information This error seems to happen because Darling is ignoring the flag AT_REMOVEDIR_DATALESS when passed to unlinkat.

System Information

Software	Version
Linux Kernel	6.3.6-arch1-1
Darling	894d62c91d78d56e05708f40f2d7e490fce5f046

[wjc404]

I got the same issue when using darling(built from master branch yesterday) on WSL2(ubuntu-22.04):

[bugaevc]

atflags_bsd_to_linux needs to handle AT_REMOVEDIR_DATALESS

[bugaevc]

On top of that it should reject unknown flags with EINVAL, which is what rm expects to see if the kernel doesn't support AT_REMOVEDIR_DATALESS

[bugaevc]

XNU has these AT flags:

• AT_EACCESS -- Linux has that too, we could just convert it, or ignore it, depending on what we want to do about UID/setuid
• AT_SYMLINK_NOFOLLOW, AT_SYMLINK_FOLLOW, AT_REMOVEDIR -- these we handle already
• AT_REMOVEDIR_DATALESS, which is what this bug is about -- same as AT_REMOVEDIR, but don't materialize the dir first if it's dataless. Dataless files are apparently some sort of placeholders for real files that can be "materialized" into full files with help from filecoordinationd -- and by default, dataless files are automatically and transparently materialized, unless you explicitly ask not to, and AT_REMOVEDIR_DATALESS is one way of doing that. Since we don't and are not going to have anything like dataless files in Darling, it's safe to treat AT_REMOVEDIR_DATALESS just like AT_REMOVEDIR
• AT_REALDEV -- seems to impact what st_dev gets returned for fstatat, not sure how exactly; we could just ignore it since we virtualize VFS/mounts/devices anyway
• AT_FDONLY is Linux's AT_EMPTY_PATH

Anything else -> EINVAL

[niansa]

Maybe it should be checked how Darwin handles fat32 volumes which don't support dataless files either Just to make sure Darling does the same on volumes that don's support it (say, root volume).

[mrhhug]

Can confirm the fix at : https://github.com/darlinghq/darling-xnu/pull/2 remediates the rm -rf directory issue on my current kernel : 6.4.3-arch1-2