Re: [PATCH v9 1/7] typeinfo: Introduce KCFI typeinfo mangling API

[Kees Cook <kees@kernel.org>]

On Fri, Dec 12, 2025 at 03:07:51PM -0800, Andrew Pinski wrote:
> On Tue, Dec 9, 2025 at 6:27 PM Kees Cook <kees@kernel.org> wrote:
> [...]
> > +uint32_t
> > +typeinfo_get_hash (tree type)
> > +{
> > +  gcc_assert (type != NULL_TREE);
> > +  uint32_t hash_state = 2166136261U; /* FNV-1a 32-bit offset basis.  */
> > +
> > +  mangle_type (type, nullptr, &hash_state);
> > +  return hash_state;
> > +}
> 
> It might make sense to do a few self_test here instead of (in addition
> to) having a testcase.
> This way the testing is done earlier.

I tried to do this back in v2 and could not make it work. See [1] for
more details on what I found, but basically I don't have access to the
parser itself in the selftests, so I couldn't build end-to-end testing
of arbitrary C (testing node types isn't really a sufficient test in my
view). I could to basic type tests, but it would be redundant to what
I ended up with in dg, and I didn't want to split up the testing.

If I'm missing some other way to do this, I'd be happy to give it a shot!

-Kees

[1] https://lore.kernel.org/linux-hardening/20250905002418.464643-1-kees@kernel.org/

-- 
Kees Cook