[TUHS] Query on PDP-11 assembly

Brantley Coile brantley at coraid.com
Wed Apr 30 23:55:13 AEST 2008

In your example, -(sp) = r5; r5 = pc; pc = guestf.
Guestf will have to bump r5 as in consumes the parameters.
Rts r5 means pc = r5; r5 = (sp)+.

Hope this helps.

Warren Toomey wrote:
> All, I'm trying to write a PDP-11 disassembler for a.out files. I'm having
> trouble dealing with jsrs. Take, for example, the code here:
> http://minnie.tuhs.org/UnixTree/1972_stuff/s1/frag19.html
> I can happily deal with the   jsr pc,do   type of jsr, but the ones
> involving r5 have me stumped, e.g.:
> 	jsr	r5,questf; < nonexistent\n\0>; .even
> It appears that data is being inserted into the executable directly
> after the jsr instruction. How does the rts which returns from the jsr
> know how much data to skip, and what is the involvement of r5 here?
> Thanks,
> 	Warren
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