On 5/11/21 4:24 PM, Andrii Nakryiko wrote:

On Fri, May 7, 2021 at 8:49 PM Alexei Starovoitov
[off-list ref] wrote:

quoted

From: Alexei Starovoitov <ast@kernel.org>

Rely on fd_array kernel feature only to generate loader program,
since it's mandatory for it.
Avoid using fd_array by default to preserve test coverage
for old style map_fd patching.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---

As mentioned in the previous patch, this is almost a complete undo of
one of the earlier patches, but it also leaves FEAT_FD_IDX and
probe_kern_fd_idx() around. Can you please try to combine them?

I cannot combine 9 and this 15, because then 14 will be broken.
I'd have to combine all 3, but then the fd_idx won't get its own
test coverage.
With patches 1 through 9 I've tested the whole test_progs
and that gives the confidence that kernel and libbpf side
are doing it correctly.
Then with the rest of patches and without 15 I test everything again.
Such testing approach covers lskel and fd_idx together.
I think this patch 15 is rather unnecessary. It's here only because
you didn't like patch 9.
I think patch 9 is a good default for libbpf to take.
Eventually llvm can emit .o with fd_idx style.
The libbpf would just call probe_kern_fd_idx() and won't need
to massage the .text after llvm if kernel supports it.
It would need to sanitize back to BPF_PSEUDO_MAP_FD only on older kernels.
That's the reason I'm not deleting probe_kern_fd_idx() in this patch,
because I think it will be used fairly soon.
But I can delete it too if you insist.
But combining 9,14,15 into one I'd like to avoid.
I think there is a value to have this in git to easily go back later
to test everything in fd_idx mode by reverting this patch 15.