The two flags are distinct and it is impossible to correctly handle clone(2)
without the assistance of fork1().
I've added a fork_req flag, FR2_SHARE_PATHS, which indicates that p_pd
should be treated the opposite way p_fd is (based on RFFDG flag). This is a
little ugly, but the benefit is that existing RFFDG API is preserved.
Holding FR2_SHARE_PATHS disabled, RFFDG indicates both p_fd and p_pd are
copied, while !RFFDG indicates both should be cloned.
In Chrome, clone(2) is used with CLONE_FS, without CLONE_FILES, and expects
independent fd tables.
The previous conflation of CLONE_FS and CLONE_FILES was introduced in