Makefile: support cross compiling

Dockerfile

@@ -2,11 +2,18 @@ FROM debian:testing
 
 WORKDIR /agent
 
-ARG arch=amd64
-
-RUN apt-get update -y && apt-get dist-upgrade -y && apt-get install -y \
+# cross_debian_arch: amd64 or arm64
+# cross_pkg_arch: x86-64 or aarch64
+RUN cross_debian_arch=$(uname -m | sed 's/x86_64/arm64/' | sed 's/aarch64/amd64/'); \
+    cross_pkg_arch=$(uname -m | sed 's/x86_64/aarch64/' | sed 's/aarch64/x86-64/'); \
+    dpkg --add-architecture "${cross_debian_arch}" && \
+    apt-get update -y && \
+    apt-get dist-upgrade -y && \
+    apt-get install -y \
     curl wget cmake dwz lsb-release software-properties-common gnupg git clang-16 llvm \
-    golang unzip jq && apt-get clean autoclean && apt-get autoremove --yes
+    golang unzip jq libc6:${cross_debian_arch} gcc-${cross_pkg_arch}-linux-gnu && \
+    apt-get clean autoclean && \
+    apt-get autoremove --yes
 
 RUN wget -qO- https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(go env GOPATH)/bin v1.56.2
 

Makefile

@@ -3,6 +3,34 @@
 
 SHELL := /usr/bin/env bash
 
+# Detect native architecture and translate to GOARCH.
+NATIVE_ARCH := $(shell uname -m)
+ifeq ($(NATIVE_ARCH),x86_64)
+NATIVE_ARCH := amd64
+else ifneq (,$(filter $(NATIVE_ARCH),aarch64 arm64))
+NATIVE_ARCH := arm64
+else
+$(error Unsupported architecture: $(NATIVE_ARCH))
+endif
+
+# Valid values are: amd64, arm64.
+TARGET_ARCH ?= $(NATIVE_ARCH)
+
+ifeq ($(NATIVE_ARCH),$(TARGET_ARCH))
+ARCH_PREFIX :=
+else ifeq ($(TARGET_ARCH),arm64)
+ARCH_PREFIX := aarch64-linux-gnu-
+else ifeq ($(TARGET_ARCH),amd64)
+ARCH_PREFIX := x86_64-linux-gnu-
+else
+$(error Unsupported architecture: $(TARGET_ARCH))
+endif
+
+export CGO_ENABLED = 1
+export GOARCH = $(TARGET_ARCH)
+export CC = $(ARCH_PREFIX)gcc
+export OBJCOPY = $(ARCH_PREFIX)objcopy
+
 BRANCH = $(shell git rev-parse --abbrev-ref HEAD | tr -d '-' | tr '[:upper:]' '[:lower:]')
 COMMIT_SHORT_SHA = $(shell git rev-parse --short=8 HEAD)
 
@@ -62,23 +90,13 @@ integration-test-binaries: generate ebpf
 			./$(test_name)) || exit ; \
 	)
 
-# Detect native architecture.
-UNAME_NATIVE_ARCH:=$(shell uname -m)
-
-ifeq ($(UNAME_NATIVE_ARCH),x86_64)
-NATIVE_ARCH:=amd64
-else ifneq (,$(filter $(UNAME_NATIVE_ARCH),aarch64 arm64))
-NATIVE_ARCH:=arm64
-else
-$(error Unsupported architecture: $(UNAME_NATIVE_ARCH))
-endif
-
 docker-image:
-	docker build -t profiling-agent --build-arg arch=$(NATIVE_ARCH) -f Dockerfile .
+	docker build -t profiling-agent -f Dockerfile .
 
 agent:
 	docker run -v "$$PWD":/agent -it --rm --user $(shell id -u):$(shell id -g) profiling-agent \
-		make VERSION=$(VERSION) REVISION=$(REVISION) BUILD_TIMESTAMP=$(BUILD_TIMESTAMP)
+		make TARGET_ARCH=$(TARGET_ARCH) VERSION=$(VERSION) REVISION=$(REVISION) \
+		BUILD_TIMESTAMP=$(BUILD_TIMESTAMP)
 
 legal:
 	@go install go.elastic.co/go-licence-detector@latest

libpf/pfelf/testdata/Makefile

@@ -1,5 +1,8 @@
 .PHONY: all
 
+CC ?= cc
+OBJCOPY ?= objcopy
+
 BINARIES=fixed-address \
 	go-binary \
 	kernel-image \
@@ -15,18 +18,18 @@ clean:
 	rm -f $(BINARIES)
 
 with-debug-syms: test.c
-	gcc $< -g -o $@
+	$(CC) $< -g -o $@
 
 without-debug-syms: test.c
-	gcc $< -s -o $@
+	$(CC) $< -s -o $@
 
 separate-debug-file: with-debug-syms
-	objcopy --only-keep-debug $< $@
+	$(OBJCOPY) --only-keep-debug $< $@
 
 fixed-address: fixed-address.c fixed-address.ld
 	# The following command will likely print a warning (about a missing -T option), which should be ignored.
 	# Removing the warning would require passing a fully-fledged linker script to bypass gcc's default.
-	gcc $^ -o $@
+	$(CC) $^ -o $@
 
 # Write an ELF notes file with a build ID
 the_notorious_build_id:
@@ -36,12 +39,12 @@ the_notorious_build_id:
 	bash -c "echo -en 'somedata\x04\x00\x00\x00\x14\x00\x00\x00\x03\x00\x00\x00GNU\x00_notorious_build_id_\x00somedata' > $@"
 
 kernel-image: test.c
-	gcc $< -s -o $@ -DLINUX_VERSION="\"Linux version 1.2.3\\n\""
+	$(CC) $< -s -o $@ -DLINUX_VERSION="\"Linux version 1.2.3\\n\""
 
 ubuntu-kernel-image: test.c
-	gcc $< -s -o $@ -DLINUX_VERSION="\"Linux version 1.2.3 (Ubuntu 4.5.6)\\n\""
+	$(CC) $< -s -o $@ -DLINUX_VERSION="\"Linux version 1.2.3 (Ubuntu 4.5.6)\\n\""
 
 # A fake go binary (with a .gopclntab section)
 go-binary: without-debug-syms
-	objcopy --add-section .gopclntab=/dev/null $< $@
+	$(OBJCOPY) --add-section .gopclntab=/dev/null $< $@
 

reporter/testdata/Makefile

@@ -1,7 +1,7 @@
 .PHONY: all
 
-CC=gcc
-CFLAGS=-Wl,--build-id
+CC ?= cc
+CFLAGS = -Wl,--build-id
 
 all: test
 

support/ebpf/Makefile

@@ -1,28 +1,24 @@
 SHELL ?= bash
-
-CLANG ?= clang-16
-LINK ?= llvm-link-16
+BPF_CLANG ?= clang-16
+BPF_LINK ?= llvm-link-16
 LLC ?= llc-16
 
 DEBUG_FLAGS = -DOPTI_DEBUG -g
 
-# Detect native architecture.
-NATIVE_ARCH:=$(shell uname -m)
-
+# Detect native architecture and translate to GOARCH.
+NATIVE_ARCH := $(shell uname -m)
 ifeq ($(NATIVE_ARCH),x86_64)
-NATIVE_ARCH:=x86
-else ifeq ($(NATIVE_ARCH),aarch64)
-NATIVE_ARCH:=arm64
+NATIVE_ARCH := amd64
+else ifneq (,$(filter $(NATIVE_ARCH),aarch64 arm64))
+NATIVE_ARCH := arm64
 else
 $(error Unsupported architecture: $(NATIVE_ARCH))
 endif
 
-# This can be passed-in, valid values are: x86, arm64.
-target_arch ?= $(NATIVE_ARCH)
+# Valid values are: amd64, arm64.
+TARGET_ARCH ?= $(NATIVE_ARCH)
 
-# Set default values.
-TARGET_ARCH = $(target_arch)
-TRACER_NAME = tracer.ebpf.$(TARGET_ARCH)
+TRACER_NAME ?= tracer.ebpf.$(TARGET_ARCH)
 
 ifeq ($(TARGET_ARCH),arm64)
 TARGET_FLAGS = -target aarch64-linux-gnu
@@ -53,28 +49,28 @@ all: $(TRACER_NAME)
 debug: TARGET_FLAGS+=$(DEBUG_FLAGS)
 debug: all
 
-x86:
-	$(MAKE) target_arch=x86 all
+amd64:
+	$(MAKE) TARGET_ARCH=amd64 all
 
 arm64:
-	$(MAKE) target_arch=arm64 all
+	$(MAKE) TARGET_ARCH=arm64 all
 
-debug-x86:
-	$(MAKE) target_arch=x86 debug
+debug-amd64:
+	$(MAKE) TARGET_ARCH=amd64 debug
 
 debug-arm64:
-	$(MAKE) target_arch=arm64 debug
+	$(MAKE) TARGET_ARCH=arm64 debug
 
 errors.h: ../../tools/errors-codegen/errors.json
 	go run ../../tools/errors-codegen/main.go bpf $@
 
 %.ebpf.c: errors.h ;
 
 %.ebpf.$(TARGET_ARCH).o: %.ebpf.c
-	$(CLANG) $(FLAGS) -o $@
+	$(BPF_CLANG) $(FLAGS) -o $@
 
 $(TRACER_NAME): $(OBJS)
-	$(LINK) $^ -o - | $(LLC) -march=bpf -mcpu=v2 -filetype=obj -o $@
+	$(BPF_LINK) $^ -o - | $(LLC) -march=bpf -mcpu=v2 -filetype=obj -o $@
 	@./print_instruction_count.sh $@
 
 baseline: $(TRACER_NAME)

tools/fake-apm-agent/Makefile

@@ -1,5 +1,7 @@
 .PHONY: clean all
 
+CC ?= cc
+
 ARCH=$(shell uname -m)
 LIB_NAME=elastic-jvmti-linux-$(ARCH).so
 
@@ -12,10 +14,10 @@ endif
 all: fake-apm-agent $(LIB_NAME)
 
 $(LIB_NAME): fake-apm-agent-lib.c
-	cc $< -g -shared -fPIC -mtls-dialect=$(TLS_DIALECT) -ftls-model=global-dynamic -o $@
+	$(CC) $< -g -shared -fPIC -mtls-dialect=$(TLS_DIALECT) -ftls-model=global-dynamic -o $@
 
 fake-apm-agent: fake-apm-agent.c
-	cc $< -g -DLIB_NAME='"$(LIB_NAME)"' -o $@
+	$(CC) $< -g -DLIB_NAME='"$(LIB_NAME)"' -o $@
 
 clean:
 	rm elastic-jvmti-linux-$(ARCH).so