How to mark syscall eBPF programs as sleepable

[christian-2]

I have placed an eBPF progam in an ELF section syscall, however when I try to load it into the kernel ebpf.NewCollection() raises an error: "Syscall programs can only be sleepable". From elfSectionDefs I would have estimated that syscall already implies _SEC_SLEEPABLE (hence sleepable). Apparently this is not the case. How am I supposed to mark my eBPF program as sleepable.

[florianl]

Hi!
It looks like the Kernel verifier returns this error. Did you set the BPF_F_SLEEPABLE flag in the ProgramSpec?

[christian-2]

@florianl Thanks for your quick reply. Yet, I could presumably set BPF_F_SLEEPABLE programmatically in Go before I load the eBPF program from an ELF file, but can this not be set in the eBPF program's source code as well? This would keep (almost) everything about that program in one place. My understanding so far is that a section name's suffix .s may serve this purpose, but this also did not work in my specific case so far.

[christian-2]

I think the puzzle is solved: the Go build pulls in github.com/cilium/ebpf v0.12.3, which apparently does not include a relevant bug fix.