Replace obi-genfiles with Makefile-based code generation

[MrAlias]

The obi-genfiles command is superfluous, its complexity can be simplified into direct use of make based commands. Other OpenTelemetry projects like opentelemetry-go-instrumentation run generation entirely using make, providing a simpler and more maintainable approach. This PR aligns OBI with that established pattern.

Changes

Removed

• cmd/obi-genfiles/
• Complex environment variable configuration (OTEL_EBPF_GENFILES_*)
• Manual file walking and staleness detection logic

Added/Modified

• generate target: Smart incremental builds using Make's dependency system
• generate/all target: Force regeneration (for clean repos or CI)
• docker-generate target: Simplified Docker-based generation
• BPF2GO_MAKEBASE export: Enables bpf2go to generate Make-compatible dependency files (.d files)
• Updated .gitignore to exclude generated .d files
• generator.Dockerfile: Removed custom tool build stage, now just runs make generate

Benefits

1. Dramatically Faster Incremental Builds

• Before: Every make generate took ~60 seconds (always regenerated everything)
• After: make generate takes ~0.05 seconds when nothing changed (1200x faster)

$ time make generate
make: Nothing to be done for 'generate'.
make generate  0.02s user 0.02s system 100% cpu 0.047 total

2. Smart Dependency Tracking

The system now tracks source dependencies via .d files generated by bpf2go:

$ touch bpf/logger/logger.c && make generate
Generating pkg/internal/ebpf/logger/...  # Only rebuilds affected package

3. Parallel Execution Support

$ make -j4 generate  # 28.5s (287% CPU) vs 60s sequential (2x faster)

4. Simpler Architecture

• No custom tool to maintain, test, or document
• Uses standard Make patterns familiar to all developers

5. Single-Target Docker Generation

$ make docker-generate  # Just works, no environment variables needed

Validation

✅ Clean Repository (git clean -dxf scenario)

$ rm -rf pkg/internal/ebpf/logger/bpf_*
$ make generate/all
### Generating all eBPF files...
# Successfully regenerates everything

✅ Incremental Builds

$ make generate
make: Nothing to be done for 'generate'.

$ touch bpf/logger/logger.c
$ make generate
Generating pkg/internal/ebpf/logger/...  # Only rebuilds changed package

✅ Dependency Tracking

24 .d files generated locally, providing accurate source dependency information

✅ Backward Compatibility

• make docker-generate continues to work (mounts workspace, runs generation in container)
• All //go:generate directives unchanged
• Generated files identical to previous method
• CI/CD workflows can continue using same commands

Testing Performed

• Clean repository build (make generate/all)
• Incremental builds (make generate)
• Dependency tracking (source file changes detected)
• Parallel execution (make -j4 generate)
• Docker-based generation (make docker-generate)
• Performance validation (0.05s no-op vs 60s previously)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 43.40%. Comparing base (9772495) to head (9d9f309).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1290      +/-   ##
==========================================
- Coverage   43.41%   43.40%   -0.02%     
==========================================
  Files         304      304              
  Lines       32779    32779              
==========================================
- Hits        14232    14228       -4     
- Misses      17630    17632       +2     
- Partials      917      919       +2     

Flag	Coverage Δ
integration-test	21.07% <ø> (-0.04%)	⬇️
integration-test-arm	0.00% <ø> (ø)
integration-test-vm-x86_64-5.15.152	?
integration-test-vm-x86_64-6.10.6	?
k8s-integration-test	2.37% <ø> (ø)
oats-test	0.00% <ø> (ø)
unittests	44.28% <ø> (ø)

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[Copilot]

Pull request overview

This PR removes the custom obi-genfiles generator tool and shifts eBPF code generation to a Makefile-driven workflow (including Docker-based generation), aiming to simplify the architecture and improve incremental rebuild performance.

Changes:

• Removed cmd/obi-genfiles and its environment-variable-driven orchestration logic.
• Added Makefile targets for incremental generation (generate), forced regeneration (generate/all), and containerized generation (docker-generate) using bpf2go .d dependency files.
• Updated the generator container to run make generate and updated .gitignore to exclude generated .d files.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 6 comments.

File	Description
generator.Dockerfile	Simplifies the generator image to run make generate instead of building/running obi-genfiles.
cmd/obi-genfiles/obi_genfiles.go	Removes the bespoke generator implementation (file deleted).
Makefile	Introduces Make-based incremental dependency tracking for eBPF codegen and updates Docker generation target.
.gitignore	Ignores generated .d dependency files.

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[rafaelroquetto]

Niceeee! Thanks for doing this. obi-genfiles is a relic from that time in which we were experimenting with generating .o files directly into the OBI/Beyla package root (to avoid committing .o files to the repo) so it had to do some gymnastics to be able to write to Go modules and the likes. It no longer serves its purpose.

This is much better, cleaner and simpler (and faster!!)

[mariomac]

Looks good! Thanks for doing

[grcevski]

LGTM!

[grcevski]

The CI failures should get fixed once we merge the PR from @skl. I'm watching for it to finish CI and I'll merge.