Interesting discussion on ETXTBSY

What if we arranged for ETXTBSY to be emitted by default for files which have pages mapped executable in some process's address space? (The flag would obviously be flipped by the first mmap(MAP_EXEC) of that file, and flipped off by munmap). This is, obviously, a change in semantics, but surely not even jitters rely on writing to executable file-backed pages (differing cache coherency semantics make this operation intrinsically nonportable in any case).

This prevents the "easy DoS" of open-with-a-flag-to-deny-overwriting -- the only DoS vector now available is the one we already have, "execute something and nobody else can overwrite it while you're executing from it", which seems entirely, y'know, desirable.