I just checked: SBCL on Linux/amd64 puts compiled functions in a r+w+x page. You could write Lisp that writes Lisp that writes self-modifying machine code, and

I just checked: SBCL on Linux/amd64 puts compiled functions in a r+w+x page. You could write Lisp that writes Lisp that writes self-modifying machine code, and it would (I think) run by default. (compiled-function-p #'f) ; T (disassemble 'f) ; disassembly for F ; Size: 58 bytes. Origin: #x5350CD14 ; F ; 14: 498B4510 MOV RAX, [R13+16] ; thread.binding-stack-pointer ; 18: 488945F8 MOV [RBP-8], RAX ; 1C: 4883EC10 SUB RSP, 16 ; [...] $ pmap $PID --range 5350CD14 442331: /usr/bin/sbcl 0000000053498000 122272K rwx-- [ anon ] total 122272K