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vbpf / ebpf-verifier

eBPF verifier based on abstract interpretation
MIT License
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Add support for subprograms (call_local) #582

Closed dthaler closed 8 months ago

dthaler commented 9 months ago

https://www.ietf.org/archive/id/draft-ietf-bpf-isa-00.html#program-local-functions discusses program-local functions called via BPF_CALL with src = 0x1.

And there's been a discussion on the Linux kernel mailing list about the interaction between them and tail calls. In https://lore.kernel.org/bpf/1c0c1ede-8595-4420-9f70-004645895a71@huaweicloud.com/T/#mf88008daa42ba22f7d624718ccb2f3871163109a, Alexei writes:

I'm not sure it's such a code idea to support tailcalls from subprogs in risc-v. They're broken on x86-64 and so far several attempts to fix them were not successful. If we don't have a fix soon we will disable this feature completely in the verifier. In general tailcalling from subprogs is a niche use case. If there are users they should transition to tail call from main prog only.

dthaler commented 8 months ago

This seems to be a duplicate of issue #451