Re: [PATCH bpf-next v2 0/4] bpf: make trusted args nullable

[Eduard Zingerman <eddyz87@gmail.com>]

On Fri, 2024-05-10 at 05:28 -0700, Vadim Fedorenko wrote:
> Current verifier checks for the arg to be nullable after checking for
> certain pointer types. It prevents programs to pass NULL to kfunc args
> even if they are marked as nullable. This patchset adjusts verifier and
> changes bpf crypto kfuncs to allow null for IV parameter which is
> optional for some ciphers. Benchmark shows ~4% improvements when there
> is no need to initialise 0-sized dynptr.
> 
> v2:
> - adjust kdoc accordingly
> 

Hi Vadim, sorry for late response.

I think that this patch-set looks good,
but I'd like to ask you to add a dedicated test to the following file:
tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c.
(crypto tests are for crypto and might be modified in the future
 w/o consideration of verifier pathways they currently test).

Also nullable dynptr sounds kind-of funny.
As far as I understand, performance gains are due to omission of extra
function call. Did you consider inlining for bpf_dynptr_from_mem()?
Same way it is done for bpf_kptr_xchg() in verifier.c:do_misc_fixups().

Thanks,
Eduard