RE: UserGenException argument passing (PR 43431)

["Paul Koning" <Paul_Koning%Dell.com@localhost>]

> > could someone please explain how UserGenException
> (arch/mips/mips/mipsX_subr.S)
> > is supposed to pass the last argument (the trap frame pointer) to
> trap()?
> 
>    I don't think it does, or ever did.  The trap frame pointer points
> to
> the trap frame for kernel exceptions, and should only be used for
them.
> User exceptions save the registers in the PCB, and reference them from
> there.

That inconsistency is certainly there as far back as 1.6.2.  So what's
going on is that the "frame" argument in trap() is valid for kernel
traps and garbage for user traps.  Given that trap() doesn't reference
the "frame" argument for user traps, this piece of sloppy coding doesn't
actually cause trouble.

        paul