When the linux kernel sets the NX bit vm86 segfaults when it tries to execute
code in memory that is not marked EXEC. Such code gets called whenever
we return from a VBIOS call to signal the calling program that the call
is actually finished and that we are not trapping for other reasons (like
IO accesses).
Use mprotect(2) to set these memory ranges PROT_EXEC.
a9e20306fb