Tinygo on Miek Gieben

eBPF from Go - IV - Code generation

Mon, 28 Oct 2024 15:47:08 +0200

Played more with TinyGo, but it always generates code for (minimal) reflection - i.e. the reflect package, because it requires that for its map implementation. I could skip or not generate that, but then that would mean using a map would be … weird? Anyhow it looked that even TinyGo does too much for eBPF. So plan D: generate eBPF code (and Go code) using Go. Cilium has done a lot of work in this regard.

eBPF from Go - III - Reducing the SSA

Mon, 30 Sep 2024 15:47:08 +0200

Again some progress. I’m mostly focussing on removing code from the SSA representation (-internal-dumpssa), so that I can work with a clean slate. As BPF is so limited almost none of the features from Go make sense, although in some far fetched future it would be super cool to have channels and goroutines to something in BPF - but not today. First need to get to “Hello World”.

I’m building this code:

eBPF from Go - II

Fri, 30 Aug 2024 15:47:08 +0200

Following up from the previous blog post… I’ve got a JSON file with the string ‘bpf’ in the correct place. Let’s see what tinygo thinks of that:

% ./build/tinygo build -o miekg/main.bpf -target bpf ./miekg/main.go
No available targets are compatible with triple "bpf-unknown-unknown"

clang indeed does not list bpf as a valid target, so this needs to be added.

The llvm build is configured from the main GNUMakefile, with -DLLVM_TARGETS_TO_BUILD.... Using grep and find I found the “llvm/test/CodeGen” directory, which, in addition to all listed targets also has a BPF directory. Let’s add BPF to that list and recompile.

eBPF from Go; First Steps

Thu, 29 Aug 2024 20:04:35 +0200

So I had this itch that I wanted to make a Go program compile to eBPF and be able to load that program in the Linux kernel by use of bpftool.

As I say in github.com/miekg/ebpf

eBPF in C? What am I, a farmer?

After much reading about eBPF and thinking about how that would work from Go, I figured that would involve writing a Go compiler.

So I could:

hack the official Go compiler and (try to) add a eBPF target (which would probably never be added as an official target because of all the constraints eBPF has).