W ^ X


Shorthand for: PROT_WRITE xor PROT_EXEC

Goal: In regular process, ensure no page is mapped both PROT_EXEC
and PROT_WRITE simultaneously

Handle GOT/PLT
exec on some... not on others..
ld.so must know about modifying those (and signal blocking)

kernel must map ld.so more carefully

Making this change took a lot of time

Not violating POSIX