Enable generation of pointer variables by eBPF CodeGenInspector #3131
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Co-authored-by: Mateusz Kossakowski <[email protected]> Co-authored-by: Jan Palimąka <[email protected]>
mihaibudiu
approved these changes
Mar 15, 2022
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This PR enables emitting eBPF fields as pointer variables by eBPF
CodeGenInspector. So far,CodeGenInspectorassumes that eBPF fields (e.g.Headers) are on-stack variables. With this change, we can decide whether to access fields' member via.or->.A use case for this change is PSA implementation for eBPF backend. PSA-eBPF uses BPF array map to store the
Headersstructure, instead of an on-stack variable, to avoid BPF stack size limit, see the discussion here vmware-archive/p4c-xdp#43. Using BPF array map to store large piece of data (parsed headers) is a common approach used also by Cilium/Calico eBPF datapaths. We've observed almost no impact on performance when using BPF array map.Note that
ebpf_model.p4is not affected by this change, becauseuseAsPointerVariableis never called for any eBPF field generated for eBPF model.This PR is one from the series of PRs bringing the support for the PSA model to eBPF backend. The goal is to shrink the "main PR" with the full implementation of PSA for eBPF to facilitate review.
Co-authored-by: Mateusz Kossakowski [email protected]
Co-authored-by: Jan Palimąka [email protected]