Support multiple languages / platforms about libbpf-bootstrap HOT 9 CLOSED

I have some small questions.

1. Do we need a symbolic link in src/bpf to vmlinux.h ?
2. How does rust example link against libbpf ?

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I like it overall, but I'd leave libbpf submodule at the top level still. It is not used from Rust, but I feel like it's a good idea to keep it at top level, because some other language might come up that will build libbpf from sources (e.g., Go + Cgo). In in general, it's libbpf-bootstrap, so libbpf should be more apparent ;)

As for Makefile in each example subdir. It's trivial to have a simlar makefile that will delegate to upper level Makefile for build and clean up, so yeah, cd examples/c/bootstrap && make should just work, IMO.

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@chenhengqi

Do we need a symbolic link in src/bpf to vmlinux.h ?

Yeah, we could. Or we could just have src/bpf/xdp.bpf.c do #include "../../../vmlinux/vmlinux.h".

How does rust example link against libbpf ?

libbpf-rs depends on libbpf-sys. libbpf-sys vendors (submodule) a specific libbpf version and builds/links to it at compile time: https://github.com/alexforster/libbpf-sys/blob/3c1c21e45c7ea74f6d0fe18ab99624d9ee14fc96/build.rs#L13-L23

from libbpf-bootstrap.

I like it overall, but I'd leave libbpf submodule at the top level still. It is not used from Rust, but I feel like it's a good idea to keep it at top level, because some other language might come up that will build libbpf from sources (e.g., Go + Cgo). In in general, it's libbpf-bootstrap, so libbpf should be more apparent ;)

Sure, sounds good.

As for Makefile in each example subdir. It's trivial to have a simlar makefile that will delegate to upper level Makefile for build and clean up, so yeah, cd examples/c/bootstrap && make should just work, IMO.

Ok, I'll look into that

I'll update the issue summary

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The kprobe program depends on vmlinux.h. If I want to compile the android bpf program, do I need to generate the vmlinux.h file corresponding to the android system? How should I organize them?

└── vmlinux
    ├── vmlinux_508.h
    └── vmlinux.h -> vmlinux_508.h

Or this?

- vmlinux
  - linux/vmlinux.h
  - android/vmlinux.h

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Maybe:

└── vmlinux
    ├── Makefile
    ├── xmake.lua
    ├── vmlinux_508.h
    └── vmlinux.h -> vmlinux_508.h

and then depending on if you use make or xmake vmlinux_508.h and vmlinux.h is overwritten. And if you retarget xmake to android, vmlinux* gets overwritten

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No overwriting, please. See iovisor/bcc#3265 for how we dealt with it in libbpf-tools. Do you think that's feasible here as well?

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So only one vmlinux.h can support linux and android at same time? It seems great!

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Yes, it's just a source of type definitions, nothing more. And you don't even need vmlinux.h, you can define all the types on your own and mark them with __attribute__((preserve_access_index)) to make them CO-RE-compatible.

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