Re: [PATCH bpf-next 2/2] selftests/bpf: add inline assembly helpers to access array elements

[Barret Rhoden]

On 1/3/24 16:21, Andrii Nakryiko wrote:
> On Wed, Jan 3, 2024 at 12:06 PM Barret Rhoden<brho@xxxxxxxxxx>  wrote:
> > On 1/3/24 14:51, Andrii Nakryiko wrote:
> > > I'm curious how bpf_cmp_likely/bpf_cmp_unlikely (just applied to
> > > bpf-next) compares to this?
> > these work great!
> >
> > e.g.
> >
> >           if (bpf_cmp_likely(idx, <, NR_MAP_ELEMS))
> >                   map_elems[idx] = i;
> >
> > works fine.  since that's essentially the code that bpf_array_elem() was
> > trying to replace, i'd rather just use the new bpf_cmp helpers than have
> > the special array_elem helpers.
> ok, cool, thanks for checking! The less special macros, the better.

sorry - turns out it only worked in testing.  in my actual program, i 
still run into issues.  the comparison is done, which is what bpf_cmp 
enforces.  but the compiler is discarding the comparison.  i have more 
info in the other thread, but figured i'd mention it here too.  =(