Replace obi-genfiles with Makefile-based code generation

.gitignore

@@ -86,6 +86,8 @@ internal/test/integration/components/pythonserver/pyvenv.cfg
 internal/test/integration/components/gosql/qosql
 *_bpfel.go
 *_bpfel.o
+*_bpfel.go.d
+*_bpfeb.go.d
 opentelemetry-ebpf-instrumentation.sln
 obi.sln
 internal/test/integration/components/javakafka/target/*

Makefile

@@ -45,7 +45,7 @@ CILIUM_EBPF_VER ?= v0.20.0
 CILIUM_EBPF_PKG := github.com/cilium/ebpf
 
 # regular expressions for excluded file patterns
-EXCLUDE_COVERAGE_FILES="(_bpfel.go)|(/opentelemetry-ebpf-instrumentation/internal/test/)|(/opentelemetry-ebpf-instrumentation/configs/)|(.pb.go)|(/pkg/export/otel/metric/)|(/cmd/obi-genfiles)"
+EXCLUDE_COVERAGE_FILES="(_bpfel.go)|(/opentelemetry-ebpf-instrumentation/internal/test/)|(/opentelemetry-ebpf-instrumentation/configs/)|(.pb.go)|(/pkg/export/otel/metric/)"
 
 .DEFAULT_GOAL := all
 
@@ -54,6 +54,12 @@ EXCLUDE_COVERAGE_FILES="(_bpfel.go)|(/opentelemetry-ebpf-instrumentation/interna
 # projects ca have different versions of the tools
 PROJECT_DIR := $(shell dirname $(abspath $(firstword $(MAKEFILE_LIST))))
 
+# BPF2GO_MAKEBASE tells bpf2go to generate Make-compatible dependency files (.d files)
+# relative to the project root. These .d files track dependencies between generated
+# Go code and source .c/.h files, enabling smart incremental builds.
+# See: https://pkg.go.dev/github.com/cilium/ebpf/cmd/bpf2go
+export BPF2GO_MAKEBASE := $(PROJECT_DIR)
+
 # Check that given variables are set and all have non-empty values,
 # die with an error otherwise.
 #
@@ -168,18 +174,87 @@ update-offsets: $(GO_OFFSETS_TRACKER)
 	@echo "### Updating pkg/internal/goexec/offsets.json"
 	$(GO_OFFSETS_TRACKER) -i configs/offsets/tracker_input.json pkg/internal/goexec/offsets.json
 
-.PHONY: generate
+### eBPF Code Generation ###########################################################
+#
+# This section handles generation of Go code from eBPF C sources using bpf2go.
+# The system supports smart incremental builds via Make's dependency tracking.
+#
+# Developer Guide:
+#
+#   make generate      - Smart incremental build (recommended for development)
+#                        Only regenerates files that are missing or out-of-date.
+#                        Takes ~0.05s when nothing needs rebuilding.
+#
+#   make generate/all  - Force regeneration of everything (use after git clean)
+#                        Always regenerates all eBPF code (~60s).
+#                        Use after: git clean -dxf, initial clone, or when in doubt.
+#
+#   make docker-generate - Generate in Docker container (for reproducible builds)
+#                          Mounts workspace and runs 'make generate' inside container.
+#                          Image: $(GEN_IMG)
+#
+# How it works:
+#   - bpf2go generates .d files (thanks to BPF2GO_MAKEBASE) that track dependencies
+#   - Make reads these .d files to know when source .c/.h files have changed
+#   - Only affected packages are rebuilt when sources change
+#   - Pattern rule runs go generate for each out-of-date file's directory
+#
+# Generated files (gitignored):
+#   - *_bpfel.go, *_bpfeb.go  - Go bindings for eBPF programs
+#   - *_bpfel.o, *_bpfeb.o    - Compiled eBPF bytecode
+#   - *_bpfel.go.d, *_bpfeb.go.d - Dependency files for Make
+#
+# NOTE on parallel builds:
+#   Using 'make -j' with the 'generate' target may result in a race condition.
+#   Each go generate invocation produces multiple files, and parallel execution
+#   can cause bpf2go to simultaneously be run on the same directory. This
+#   command should be idempotent, but it may cause redundant generation and
+#   potential conflicts.
+#
+################################################################################
+
+BPF_ROOT = pkg/
+
+# Find all generated Go and object files (used as Make targets)
+BPF_GEN_GO := $(shell find $(BPF_ROOT) -type f \( -name 'bpf_*_bpfe[lb].go' -o -name 'net_*_bpfe[lb].go' -o -name 'netsk_*_bpfe[lb].go' \))
+BPF_GEN_OBJ := $(BPF_GEN_GO:.go=.o)
+BPF_GEN_ALL := $(if $(BPF_GEN_GO),$(BPF_GEN_GO) $(BPF_GEN_OBJ))
+
+# Include dependency files generated by bpf2go for smart incremental builds.
+# These .d files contain Make rules like:
+#   pkg/internal/ebpf/logger/bpf_x86_bpfel.go: bpf/logger/logger.c bpf/bpfcore/vmlinux.h ...
+-include $(shell find $(BPF_ROOT) -type f -name '*_bpfe[lb].go.d' 2>/dev/null)
+
+.PHONY: generate generate/all
+# Smart incremental build - only regenerates what's needed
 generate: export BPF_CLANG := $(CLANG)
 generate: export BPF_CFLAGS := $(CFLAGS)
 generate: export BPF2GO := $(BPF2GO)
-generate: $(BPF2GO)
-	@echo "### Generating files..."
-	@OTEL_EBPF_GENFILES_RUN_LOCALLY=1 go generate cmd/obi-genfiles/obi_genfiles.go
-
+generate: $(BPF2GO) $(if $(BPF_GEN_ALL),$(BPF_GEN_ALL),generate/all)
+
+# Pattern rule: regenerate specific eBPF files when dependencies change
+$(BPF_GEN_ALL): $(BPF2GO)
+	@echo "Generating $(dir $@)..."
+	@go generate ./$(dir $@)
+
+# Force regeneration of all eBPF code (use after git clean or initial clone)
+generate/all: export BPF_CLANG := $(CLANG)
+generate/all: export BPF_CFLAGS := $(CFLAGS)
+generate/all: export BPF2GO := $(BPF2GO)
+generate/all: $(BPF2GO)
+	@echo "### Generating all eBPF files..."
+	@go generate ./...
+
+# Generate eBPF code in Docker container for reproducible builds
 .PHONY: docker-generate
 docker-generate:
-	@echo "### Generating files (docker)..."
-	@GOOS=$(shell go env GOHOSTOS) GOARCH=$(shell go env GOHOSTARCH) OTEL_EBPF_GENFILES_GEN_IMG=$(GEN_IMG) go generate cmd/obi-genfiles/obi_genfiles.go
+	@echo "### Generating files in Docker..."
+	@$(OCI_BIN) run --rm \
+		-u $(DOCKER_USER) \
+		-v "$(CURDIR):/src:z" \
+		-w /src \
+		$(GEN_IMG) \
+		make generate
 
 .PHONY: verify
 verify: prereqs lint test license-header-check