> [ as John tries to find a gun...  8-]
> 
> Basically, the first four cases are explicitly covered by the
> interface described by sigreturn(), and also work the same
> way on N other architectures.  They *must* return the proper
> error codes, and *not* do anything else.
> 
> The final case, that of the bogus LDTs, is the only one that
> *can* be handled differently.  Since a bogus LDT either means
> a serious problem, or an (obvious) attempt to breach security,
> the process trying it should be signalled, if possible.
> 
> comments follow the chunks that they comment on.  The above bit
> is what i've been trying to say, but i think i've made a little
> mess of it.

Sigh... Now I get it...
> 
> > --- 511,566 ----
> >         fp = (struct sigframe *)
> >              ((caddr_t)scp - offsetof(struct sigframe, sf_sc));
> >   
> > !       if (useracc((caddr_t)fp, sizeof(*fp), 0) == 0) {
> > !               trapsignal(p, SIGBUS, T_STKFLT);
> >                 return(EINVAL);
> > +       }
> 
> can't access something on the stack.  man page says "return EFAULT."
> (i.e. don't signal)
Ok on this one - nuke the trapsignal.

> 
> > !       if (useracc((caddr_t)scp, sizeof(*scp), 0) == 0) {
> > !               trapsignal(p, SIGBUS, T_STKFLT);
> >                 return(EINVAL);
> > +       }
> 
> can't access something on the stack.  man page says "return EFAULT."
> (i.e. don't signal)
Ditto.

> 
> >         /* make sure they aren't trying to do anything funny */
> > !       if ((scp->sc_ps & PSL_MBZ) != 0 || (scp->sc_ps & PSL_MBO) != PSL_MBO) {
> > !               trapsignal(p, SIGBUS, T_PROTFLT);
> >                 return(EINVAL);
> > +       }
> 
> The process status longword is invalid.  man page says "return EINVAL."
> (i.e. don't signal)
Ditto, ditto.

> 
> >         /* compare IOPL; we can't insist that it's always 3 or the X server
> >            will fail */
> > !       if ((tf->tf_eflags & PSL_IOPL) < (scp->sc_efl & PSL_IOPL)) {
> > !               trapsignal(p, SIGBUS, T_PROTFLT);
> >                 return(EINVAL);
> > +       }
> 
> The process status longword is would raise the process's privilege.
> man page says "return EINVAL." (i.e. don't signal)
Ok, but this is a 386 specific thing.

> 
> >         p->p_sigacts->ps_onstack = scp->sc_onstack & 01;
> >         p->p_sigmask = scp->sc_mask &~
> >             (sigmask(SIGKILL)|sigmask(SIGCONT)|sigmask(SIGSTOP));
> > + 
> > +       /*
> > +        * Sanity check the user's selectors and error if they
> > +        * are suspect.
> > +        */
> > + #define max_ldt_sel(pcb) \
> > +       ((((pcb)->pcb_ldt)? \
> > +           (gdt_segs[GUSERLDT_SEL].ssd_limit + 1) : \
> > +               sizeof(ldt))/sizeof(union descriptor))
> > + 
> > + #define valid_sel(sel) \
> > +       (((sel) == 0) || \
> > +         (ISPL((sel)) == SEL_UPL && ISLDT((sel))) || \
> > +         (ISLDT((sel)) && IDXSEL((sel)) < max_ldt_sel((struct pcb *)(p->p_addr))))
> > + 
> > +       if (scp->sc_cs&0xffff != _ucodesel || scp->sc_ss&0xffff != _udatasel ||
> > +           scp->sc_ds&0xffff != _udatasel || scp->sc_es&0xffff != _udatasel) {
> > +               if (!valid_sel(scp->sc_cs) || !valid_sel(scp->sc_ss) ||
> > +                   !valid_sel(scp->sc_ds) || !valid_sel(scp->sc_es)) {
> > +                   trapsignal(p, SIGBUS, T_PROTFLT);
> > +                   return(EINVAL);
> > +               }
> > +       }
> > + #undef valid_sel
> 
> Man page doesn't cover this case.
> 
> They're trying to do something "strange and evil" to the CPU.
> Strange and evil processes must be stopped!  But, if they're stopped,
> they can be restarted.  So... HIT IT WITH A BUS!  8-)

So this is right now case is right now ?

Amazing - looks like my first implementation before I decided to
"clean it up" and post it...

> 
> 
> 
> chris

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 John Brezak                    UUCP:     uunet!apollo.hp!brezak
 Hewlett Packard/Apollo         Internet: brezak@ch.hp.com
 300 Apollo Drive               Phone:    (508) 436-4915
 Chelmsford, Massachusetts      Fax:      (508) 436-5103


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