🚀 go-pugleaf

rkl@cbnewsh.att.com (kevin.laux) writes:

>	RETF is used when interrupt handlers want to return one of the Flags
>bits.  The INT instruction pushes the Flags onto the current stack, then CS,
>then IP.  When the interrupt handler uses the flags bits to return success,
>failure or whatever, it cannot use an IRET as this will end up popping the
>old flags off the stack destroying the bits that were purposely set up.
>The RETF 0002h instruction will pop CS:IP off the stack and then will discard
>two bytes.

I think you are wrong.  (Purely conjecture, since I haven't debugged the
code, of course).  I think routines that return information in the
flags (such as, e.g., almost all of the INT 21 routines) do it by
manipulating the word on the stack itself (at, I believe, [SP+4]), so
that the final IRET returns a diferent flags value than the one
originally pushed by the INT instruction.