How are bpf_bpf{eb,el}.o files generated?

[hiqsociety]

for example xdp bpf_bpfeb.o <-- how is this file generated?

i would like to add libbpf_num_possible_cpus(), how do i do this?

int cpus = libbpf_num_possible_cpus();

[ti-mo]

The following go:generate statement invokes bpf2go when running go generate in the examples/xdp directory.

ebpf/examples/xdp/main.go

Line 24 in f17b01b

//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -cc $BPF_CLANG -cflags $BPF_CFLAGS bpf xdp.c -- -I../headers

This results in bpf_bpf*.(g)o files in the directory.

Regarding libbpf_num_possible_cpus(), please open another discussion with a bit more context about what you're trying to do.

[hiqsociety]

that's not true, if i remove the .o files found inside the directory, it fails to do. so it's not really running go generate to pre-generate the files

go build .

mv *.o /usr/local/src/
go build .
bpf_bpfel.go:119:12: pattern bpf_bpfel.o: no matching files found

[ti-mo]

it's (go build) not really running go generate to pre-generate the files

Exactly, did I say it would?

when running go generate in the examples/xdp directory

bpf2go invokes the compiler. This means bpf_bpfel.o is written when go generate is run.

[lmb]

Invoking go build doesn't invoke go generate, see https://go.dev/blog/generate.

[hiqsociety]

@lmb @ti-mo

i rephrase then...

1. how do i generate bpf_bpf{eb,el}.o files then?
2. how can i make xdp.c re-compile and show errors for compilation?

[lmb]

By invoking go generate in the correct folder as Timo and I have pointed out to you.