On Thu, Aug 21, 2025, 2:13 AM Peter Zijlstra <pet...@infradead.org> wrote:
> On Thu, Aug 21, 2025 at 01:16:56AM -0700, Andrew Pinski wrote:
>
> > > +/* Compute KCFI type ID for a function declaration or function type
> > > (internal) */
> > > +static uint32_t
> > > +compute_kcfi_type_id (tree fntype_or_fndecl)
> > > +{
> > > + if (!fntype_or_fndecl)
> > > + return 0;
> > > +
> > > + const char *canonical_name = mangle_function_type
> (fntype_or_fndecl);
> > > + uint32_t base_type_id = kcfi_hash_string (canonical_name);
> > >
> >
> > Now I am curious why this needs to be a mangled function name? Since the
> > function in C the symbol is just its name.
> > Is there documentation that says the hash needs to be based on all of the
> > function arguments types?
>
> The whole point of kCFI is to limit the targets of indirect calls to
> functions of the same signature. The actual function name is immaterial.
>
So then just hash the function argument types. It only needs to be
consistent for the objects that are compiled together right?
Using mangle to do the hashing seems wasteful. Was it done this way because
that was the easiest way it was done in clang?
And nobody thought this seems wasteful?
Thanks,
Andrew
>
