Locking it down: marked mappings

• mark the mappings which kbind() is allowed to alter with a new mprotect() bit

  • mprotect(got_addr, got_len, PROT_READ | __PROT_KBIND)

  • kbind() verifies that that bit is set, else sigexit(SIGILL)

• mark the GOT and PLT as not permitting further mprotect() changes

  • mprotect(got_addr, got_len, PROT_READ | __PROT_KBIND | __PROT_LOCKPROT)

• kbind() can only change those pages; those pages can only be changed by kbind()