Re: [PATCH RFC v3 24/36] kmsan: disable instrumentation of certain functions

[Alexander Potapenko <glider@google.com>]

> The comment style around __no_sanitize_memory looks very different for
> different call sites, perhaps it makes sense to unify it somehow.

Done in v4.

> > +/*
> > + * Dark magic happening here, let's not instrument this function.
> > + * Also avoid copying any metadata by using raw __memmove().
> > + */
> > +__no_sanitize_memory
> >  struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s)
> >  {
> >         /*
> > @@ -648,10 +656,10 @@ struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s)
> >                 (struct bad_iret_stack *)this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;
> >
> >         /* Copy the IRET target to the new stack. */
> > -       memmove(&new_stack->regs.ip, (void *)s->regs.sp, 5*8);
> > +       __memmove(&new_stack->regs.ip, (void *)s->regs.sp, 5*8);
> >
> >         /* Copy the remainder of the stack from the current stack. */
> > -       memmove(new_stack, s, offsetof(struct bad_iret_stack, regs.ip));
> > +       __memmove(new_stack, s, offsetof(struct bad_iret_stack, regs.ip));
>
> Looks like this change should go into a separate patch.

I disagree. Both the __no_sanitize_memory annotation and __memmove()
calls serve the same purpose: avoid calling KMSAN code from
fixup_bad_iret().
I don't think it makes sense to separate them.


> > +       kmsan_unpoison_shadow(args, sizeof(*args));
> > +       regs = args->regs;
> > +       if (regs)
> > +               kmsan_unpoison_shadow(regs, sizeof(*regs));
>
> This one as well.

Done in v4.