fix make update-kernel-deps

Switching to OCI images to distribute kernels broke the update-kernel-deps
target. Move it to a script and fix it to work with OCI images.

Signed-off-by: Lorenz Bauer <lmb@isovalent.com>

Makefile

@@ -103,14 +103,6 @@ testdata/loader-%-eb.elf: testdata/loader.c
 	$(STRIP) -g $@
 
 .PHONY: update-kernel-deps
-update-kernel-deps: KERNEL_VERSION?=6.6
+update-kernel-deps: export KERNEL_VERSION?=6.6
 update-kernel-deps:
-	$(eval TMP := $(shell mktemp -d))
-	curl -fL https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/plain/tools/lib/bpf/libbpf.c?h=v$(KERNEL_VERSION) -o "$(TMP)/libbpf.c"
-	"$(CURDIR)/internal/cmd/gensections.awk" "$(TMP)/libbpf.c" | gofmt > "$(CURDIR)/elf_sections.go"
-	curl -fL "$(CI_KERNEL_URL)/linux-$(KERNEL_VERSION)-amd64.tgz" -o "$(TMP)/linux.tgz"
-	tar xvf "$(TMP)/linux.tgz" -C "$(TMP)" --strip-components=2 ./boot/vmlinuz ./lib/modules
-	/lib/modules/$(shell uname -r)/build/scripts/extract-vmlinux "$(TMP)/vmlinuz" > "$(TMP)/vmlinux"
-	$(OBJCOPY) --dump-section .BTF=/dev/stdout "$(TMP)/vmlinux" /dev/null | gzip > "btf/testdata/vmlinux.btf.gz"
-	find "$(TMP)/modules" -type f -name bpf_testmod.ko -exec $(OBJCOPY) --dump-section .BTF="btf/testdata/btf_testmod.btf" {} /dev/null \;
-	$(RM) -r "$(TMP)"
+	./testdata/sh/update-kernel-deps.sh

run-tests.sh

@@ -14,6 +14,8 @@ set -euo pipefail
 script="$(realpath "$0")"
 readonly script
 
+source "$(dirname "$script")/testdata/sh/lib.sh"
+
 quote_env() {
   for var in "$@"; do
     if [ -v "$var" ]; then
@@ -120,26 +122,6 @@ fi
 input="$(mktemp -d)"
 readonly input
 
-readonly docker="${CONTAINER_ENGINE:-docker}"
-
-extract_oci_image() {
-  local image_name=$1
-  local target_directory=$2
-
-  echo -n "Fetching $image_name... "
-
-  # We abuse the --output flag of docker buildx to obtain a copy of the image.
-  # This is simpler than creating a temporary container and using docker cp.
-  # It also automatically fetches the image for us if necessary.
-  if ! echo "FROM $image_name" | "$docker" buildx build --quiet --pull --output="$target_directory" - &> /dev/null; then
-    echo "failed"
-    return 1
-  fi
-
-  echo "ok"
-  return 0
-}
-
 if [[ -f "${1}" ]]; then
   # First argument is a local file.
   readonly kernel="${1}"

testdata/sh/lib.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+
+set -euo pipefail
+
+readonly docker="${CONTAINER_ENGINE:-docker}"
+
+extract_oci_image() {
+	local image_name=$1
+	local target_directory=$2
+
+	echo -n "Fetching $image_name... "
+
+	# We abuse the --output flag of docker buildx to obtain a copy of the image.
+	# This is simpler than creating a temporary container and using docker cp.
+	# It also automatically fetches the image for us if necessary.
+	if ! echo "FROM $image_name" | "$docker" buildx build --quiet --pull --output="$target_directory" - &> /dev/null; then
+		echo "failed"
+		return 1
+	fi
+
+	echo "ok"
+	return 0
+}

testdata/sh/update-kernel-deps.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+
+set -euo pipefail
+
+source "$(dirname "$(realpath "$0")")/lib.sh"
+
+# Create a temporary directory
+TMP=$(mktemp -d)
+
+cleanup() {
+	rm -r "$TMP"
+}
+
+trap cleanup EXIT
+
+# Download and process libbpf.c
+curl -fL "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/plain/tools/lib/bpf/libbpf.c?h=v$KERNEL_VERSION" -o "$TMP/libbpf.c"
+"./internal/cmd/gensections.awk" "$TMP/libbpf.c" | gofmt > "./elf_sections.go"
+
+# Download the specified version of the Linux kernel
+extract_oci_image "ghcr.io/cilium/ci-kernels:$KERNEL_VERSION" "$TMP"
+
+# Extract vmlinux
+"/lib/modules/$(uname -r)/build/scripts/extract-vmlinux" "$TMP/boot/vmlinuz" > "$TMP/vmlinux"
+
+# Extract BTF
+objcopy --dump-section .BTF=/dev/stdout "$TMP/vmlinux" /dev/null | gzip > "btf/testdata/vmlinux.btf.gz"
+find "$TMP/lib/modules" -type f -name bpf_testmod.ko -exec objcopy --dump-section .BTF="btf/testdata/btf_testmod.btf" {} /dev/null \;