The previous pipe2 implementation used redox_rt::sys::open() which goes
through the FILETABLE's insert_upper mechanism. This can collide with
the untracked namespace fd (ns_fd) stored in DYNAMIC_PROC_INFO, causing
the kernel to overwrite the namespace fd entry with a pipe scheme root
entry. Subsequent open() calls then resolve to the wrong scheme, and
kdup fails with EBADF because it receives a write-end (odd) ID instead
of a read-end (even) ID.
Fix: bypass the open() function entirely and use raw syscall::openat +
syscall::dup, then register both fds with register_external_fd so the
FILETABLE tracks them correctly.
Red Bear OS
eac112e919