On Thu, 28 Dec 2017 16:26:07 +0000
Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
> On 28 December 2017 at 16:19, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> > On Wed, 27 Dec 2017 08:50:33 +0000
> > Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
> >
> >> static inline jump_label_t jump_entry_code(const struct jump_entry *entry)
> >> {
> >> - return entry->code;
> >> + return (jump_label_t)&entry->code + entry->code;
> >
> > I'm paranoid about doing arithmetic on abstract types. What happens in
> > the future if jump_label_t becomes a pointer? You will get a different
> > result.
> >
>
> In general, I share your concern. In this case, however, jump_label_t
> is typedef'd three lines up and is never used anywhere else.
I would agree if this was in a .c file, but it's in a header file,
which causes me to be more paranoid.
>
> > Could we switch these calculations to something like:
> >
> > return (jump_label_t)((long)&entrty->code + entry->code);
> >
>
> jump_label_t is local to this .h file, so it can be defined as u32 or
> u64 depending on the word size. I don't mind adding the extra cast,
> but I am not sure if your paranoia is justified in this particular
> case. Perhaps we should just use 'unsigned long' throughout?
Actually, that may be better. Have the return value be jump_label_t,
but the cast be "unsigned long". That way it should always work.
static inline jump_label_t jump_entry_code(...)
{
return (unsigned long)&entry->code + entry->code;
}
-- Steve
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