On Thu, Feb 2, 2023 at 11:50 AM Daniel Borkmann [off-list ref] wrote:

On 2/2/23 9:36 AM, Xu Kuohai wrote:

quoted

On 2/2/2023 12:34 AM, Florent Revest wrote:

quoted

This series adds ftrace direct call support to arm64.
This makes BPF tracing programs (fentry/fexit/fmod_ret/lsm) work on arm64.

It is meant to apply on top of the arm64 tree which contains Mark Rutland's
series on CALL_OPS [1] under the for-next/ftrace tag.

quoted

The first three patches consolidate the two existing ftrace APIs for registering

direct calls. They are split to make the reviewers lives easier but if it'd be a
preferred style, I'd be happy to squash them in the next revision.
Currently, there is both a _ftrace_direct and _ftrace_direct_multi API. Apart
from samples and selftests, there are no users of the _ftrace_direct API left
in-tree so this deletes it and renames the _ftrace_direct_multi API to
_ftrace_direct for simplicity.

The main benefit of this refactoring is that, with the API that's left, an
ftrace_ops backing a direct call will only ever point to one direct call. We can
therefore store the direct called trampoline address in the ops (patch 4) and
look it up from the ftrace trampoline on arm64 (patch 7) in the case when the
destination would be out of reach of a BL instruction at the ftrace callsite.
(in this case, ftrace_caller acts as a lightweight intermediary trampoline)

This series has been tested on both arm64 and x86_64 with:
1- CONFIG_FTRACE_SELFTEST (cf: patch 6)
2- samples/ftrace/*.ko (cf: patch 8)
3- tools/testing/selftests/bpf/test_progs (both -t lsm and -t fentry_fexit)

Thanks a ton for working on this!

quoted

so it's time to update DENYLIST.aarch64 to unblock tests that failed due to lack of direct call.

That's a good point Xu, thanks! I'll update the deny list in my next revision.
It looks like this series fixes *a lot* of these tests, so that's exciting. :)

+1, with regards to logistics, if possible it might be nice to eventually gets
this into a feature branch on arm64 tree, then we could pull it too from there
for bpf-next and hash out the BPF CI bits for arm64 in the meantime.

I believe that Manu Bretelle already wired up the BPF CI for arm64, is
there more work required ?
Regarding the logistics, whatever works sgtm... :) I suppose it's up
to Catalin or Will.

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