Generating multiple types with bpf2go

[tamilmani1989]

Hi,

I have multiple types in ebpf code and I couldn't use bpf2go to generate code for multiple types. If i use one type as specified in example, its working and if i define second type, go generate failing with second type not found,. is there any way to do it?

working:
//go:generate bpf2go -cc clang-13 -cflags "-g -O2 -Wall -target bpf -D__TARGET_ARCH_x86 -Wall" -type v4event bpf ./cprog.c --
../headers

Not Working:
//go:generate bpf2go -cc clang-13 -cflags "-g -O2 -Wall -target bpf -D__TARGET_ARCH_x86 -Wall" -type v4event -type verdict bpf ./cprog.c -- ../headers

bpf_bpfel.go: type name verdict: not found

[lmb]

Hi, can you provide the C source in question?

[tamilmani1989]

@lmb i figured it out. i didn't define the verdict event. i was missing this:

const struct verdict *unusedverdict __attribute__((unused));

[ti-mo]

Yep, you need to make sure to declare a dummy instance of the type and declare it unused so it doesn't get optimized away.

For posterity, you can enumerate all types present in an ELF's BTF blob using bpftool:

~ ebpf master ✓ bpftool btf dump file testdata/loader-clang-14-el.elf
...
[61] CONST '(anon)' type_id=62
[62] VOLATILE '(anon)' type_id=7
[63] VAR 'key3' type_id=61, linkage=global

This is what bpf2go will look at to generate corresponding Go types.

[tamilmani1989]

@lmb not related to this question. Currently im compiling bpf2go code and using bpf2go cmd directly with go:generate. I couldn't compile with go:generate go run github.com/cilium/ebpf/cmd/bpf2go. it s failing with flag provided but not defined: -type. when would be next release to support -type field?

[tamilmani1989]

@lmb @ti-mo any update on above query?

[ti-mo]

This is more of a Go question, but go run github.com/cilium/ebpf/cmd/bpf2go@master is possible if you need it temporarily. We'll target a release early May.