On Mon, Jul 13, 2020 at 04:32:39PM -0400, Steven Rostedt wrote:
> On Sat, 11 Jul 2020 12:49:30 +0200
> Peter Zijlstra <[email protected]> wrote:
> >
> > Something like so (on top of the next patch) ?
> >
> > I'm not convinced it actually helps much, but if it makes you feel
> > better :-)
>
> After you have bricked a bunch of people's NICs, you would be paranoid
> about this too!
>
> You work for Intel, next time you go to an office, see if you can find
> my picture on any dartboards in there ;-)
I'll tell em it was bad hardware for being able to get bricked like that
instead, how's that? ;-)
> > --- a/arch/x86/kernel/static_call.c
> > +++ b/arch/x86/kernel/static_call.c
> > @@ -56,15 +56,36 @@ static inline enum insn_type __sc_insn(b
> > return 2*tail + null;
> > }
> >
> > +static void __static_call_validate(void *insn, bool tail)
> > +{
> > + u8 opcode = *(u8 *)insn;
> > +
> > + if (tail) {
> > + if (opcode == JMP32_INSN_OPCODE ||
> > + opcode == RET_INSN_OPCODE)
> > + return;
> > + } else {
> > + if (opcode == CALL_INSN_OPCODE ||
> > + !memcmp(insn, ideal_nops[NOP_ATOMIC5], 5))
> > + return;
> > + }
> > +
> > + WARN_ONCE(1, "unexpected static_call insn opcode 0x%x at %pS\n",
> > opcode, insn);
> > +}
> > +
> > void arch_static_call_transform(void *site, void *tramp, void *func, bool
> > tail)
> > {
> > mutex_lock(&text_mutex);
> >
> > - if (tramp)
> > + if (tramp) {
> > + __static_call_validate(tramp, true);
> > __static_call_transform(tramp, __sc_insn(!func, true), func);
> > + }
> >
> > - if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site)
> > + if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site) {
> > + __static_call_validate(site, tail);
>
> I'd feel even more better if the validate failed, we just don't do the
> update.
It is either this or BUG()/panic(), you pick ;-)
