[ebpf] Add `ebpf.Modifier` for removing helper calls

[p-lambert]

What does this PR do?

Add ebpf.Modifer for removing certain helper calls from eBPF bytecode.

Motivation

Allow eBPF developers to write code referencing multiple eBPF helpers that get "conditionally selected" during runtime. For example, with this change someone might write code such as the following:

if (ring_buffers_supported) {
    bpf_ringbuf_output(...);
} else {
    bpf_perf_event_output(...);
}

And then use this ebpf.Modifer to strip out the call to bpf_ringbuf_output in case the target kernel doesn't support it:

if (ring_buffers_supported) {
    // NO-OP
} else {
    bpf_perf_event_output(...);
}

Additional Notes

Please try to favor the use of either CO-RE or runtime compilation to conditionally select eBPF helpers. This should be regarded as a last resort when the aforementioned options don't apply (prebuilt artifacts, for example).

Possible Drawbacks / Trade-offs

Describe how to test/QA your changes

[p-lambert]

/merge

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[pr-commenter[bot]]

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Regression Detector Results

Run ID: 671a84ad-96f3-4466-9b2f-14f821c47936 Baseline: dd88f33e6653d5934786a3f00041d5f9f51a7f60 Comparison: 8ef8bea4d1b3f4627bc6a0d2e2468bda1a50f311 Total CPUs: 7

Performance changes are noted in the perf column of each table:

• ✅ = significantly better comparison variant performance
• ❌ = significantly worse comparison variant performance
• ➖ = no significant change in performance

Experiments with missing or malformed data

• basic_py_check

Usually, this warning means that there is no usable optimization goal data for that experiment, which could be a result of misconfiguration.

No significant changes in experiment optimization goals

Confidence level: 90.00% Effect size tolerance: |Δ mean %| ≥ 5.00%

There were no significant changes in experiment optimization goals at this confidence level and effect size tolerance.

Experiments ignored for regressions

Regressions in experiments with settings containing erratic: true are ignored.

perf	experiment	goal	Δ mean %	Δ mean % CI
➖	file_to_blackhole	% cpu utilization	-1.42	[-7.96, +5.12]

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	+2.93	[+1.52, +4.34]
➖	process_agent_real_time_mode	memory utilization	+0.49	[+0.45, +0.52]
➖	process_agent_standard_check_with_stats	memory utilization	+0.20	[+0.16, +0.23]
➖	trace_agent_json	ingress throughput	+0.02	[-0.02, +0.06]
➖	trace_agent_msgpack	ingress throughput	+0.00	[-0.00, +0.00]
➖	uds_dogstatsd_to_api	ingress throughput	+0.00	[-0.00, +0.00]
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.00	[-0.00, +0.00]
➖	process_agent_standard_check	memory utilization	-0.36	[-0.40, -0.31]
➖	idle	memory utilization	-0.47	[-0.50, -0.43]
➖	file_tree	memory utilization	-0.47	[-0.55, -0.38]
➖	tcp_syslog_to_blackhole	ingress throughput	-0.83	[-0.92, -0.75]
➖	otel_to_otel_logs	ingress throughput	-1.14	[-1.75, -0.52]
➖	file_to_blackhole	% cpu utilization	-1.42	[-7.96, +5.12]

Explanation

A regression test is an A/B test of target performance in a repeatable rig, where "performance" is measured as "comparison variant minus baseline variant" for an optimization goal (e.g., ingress throughput). Due to intrinsic variability in measuring that goal, we can only estimate its mean value for each experiment; we report uncertainty in that value as a 90.00% confidence interval denoted "Δ mean % CI".

For each experiment, we decide whether a change in performance is a "regression" -- a change worth investigating further -- if all of the following criteria are true:

1. Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.

2. Its 90.00% confidence interval "Δ mean % CI" does not contain zero, indicating that if our statistical model is accurate, there is at least a 90.00% chance there is a difference in performance between baseline and comparison variants.

3. Its configuration does not mark it "erratic".

[dd-devflow[bot]]

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[p-lambert]

/merge

[dd-devflow[bot]]

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Use /merge -c to cancel this operation!

[dd-devflow[bot]]

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