+the old frame pointer with the return address and making EBP point two
+words later:
+
+On x86/x86-64 the stack now looks like this (stack grows downwards):
+
+@verbatim
+----------
+RETURN PC
+----------
+OLD FP
+---------- <- FP points here
+EMPTY SLOT
+----------
+FIRST ARG
+----------
+@end verbatim
+
+just as if the function had been CALLed and upon entry executed the
+standard prologue: PUSH EBP; MOV EBP, ESP. On other architectures the
+stack looks like this (stack grows upwards):
+
+@verbatim
+----------
+FIRST ARG
+----------
+EMPTY SLOT
+----------
+RETURN PC
+----------
+OLD FP
+---------- <- FP points here
+@end verbatim
+