From b8e1d11bed65942a60abdd4f5fd8168a93cc4416 Mon Sep 17 00:00:00 2001
From: Alex Zenla <alex@edera.dev>
Date: Wed, 1 Oct 2025 21:51:58 -0700
Subject: [PATCH] introduce image data copy polyfill to allow builds on systems
 without image mounts

---
 hack/build.sh                       | 46 +++++++++++++++++++++--------
 hack/clean.sh                       | 12 ++++++--
 hack/utils/Dockerfile.copy          |  1 -
 hack/utils/Dockerfile.copy-direct   |  1 +
 hack/utils/Dockerfile.copy-polyfill |  4 +++
 5 files changed, 48 insertions(+), 16 deletions(-)
 delete mode 100644 hack/utils/Dockerfile.copy
 create mode 100644 hack/utils/Dockerfile.copy-direct
 create mode 100644 hack/utils/Dockerfile.copy-polyfill

diff --git a/hack/build.sh b/hack/build.sh
index 9b2652b..7004e45 100755
--- a/hack/build.sh
+++ b/hack/build.sh
@@ -25,9 +25,37 @@ fi
 mkdir -p "${FINAL_DIR}"
 
 if [ "${SKIP_KERNEL_BUILD}" != "1" ] || [ "${SKIP_VM_BUILD}" != "1" ] || [ "${SKIP_SPROUT_BUILD}" != "1" ]; then
-	docker build -t "${DOCKER_PREFIX}/sprout-utils-copy:${DOCKER_TAG}" -f hack/utils/Dockerfile.copy hack
+	docker build -t "${DOCKER_PREFIX}/sprout-utils-copy-direct:${DOCKER_TAG}" -f hack/utils/Dockerfile.copy-direct hack
 fi
 
+copy_from_image_direct() {
+	IMAGE="${1}"
+	SOURCE="${2}"
+	TARGET="${3}"
+
+	docker run --rm -i \
+		--mount="type=image,source=${IMAGE},target=/image" \
+		"${DOCKER_PREFIX}/sprout-utils-copy-direct:${DOCKER_TAG}" cat "/image/${SOURCE}" >"${TARGET}" 2>/dev/null
+}
+
+copy_from_image_polyfill() {
+	IMAGE="${1}"
+	SOURCE="${2}"
+	TARGET="${3}"
+
+	docker build -t "${IMAGE}-copy-polyfill:${DOCKER_TAG}" --build-arg "TARGET_IMAGE=${IMAGE}:${DOCKER_TAG}" \
+		-f hack/utils/Dockerfile.copy-polyfill hack
+	# note: the -w '//' is a workaround for Git Bash where / is magically rewritten.
+	docker run --rm -i -w '//' "${IMAGE}-copy-polyfill:${DOCKER_TAG}" cat "image/${SOURCE}" >"${TARGET}"
+}
+
+copy_from_image() {
+	if ! copy_from_image_direct "${@}" 2>/dev/null; then
+		echo "[warn] image mounts not supported, falling back to polyfill"
+		copy_from_image_polyfill "${@}"
+	fi
+}
+
 if [ "${SKIP_KERNEL_BUILD}" != "1" ]; then
 	echo "[kernel build] ${TARGET_ARCH} ${RUST_PROFILE}"
 	docker build --platform="${DOCKER_TARGET}" -t "${DOCKER_PREFIX}/sprout-kernel-${TARGET_ARCH}:${DOCKER_TAG}" -f kernel/Dockerfile kernel
@@ -37,26 +65,20 @@ if [ "${SKIP_KERNEL_BUILD}" != "1" ]; then
 		build kernel
 	fi
 
-	docker run --rm -i \
-		--mount="type=image,source=${DOCKER_PREFIX}/sprout-kernel-${TARGET_ARCH}:${DOCKER_TAG},target=/image" \
-		"${DOCKER_PREFIX}/sprout-utils-copy:${DOCKER_TAG}" cat /image/kernel.efi >"${FINAL_DIR}/kernel.efi"
+	copy_from_image "${DOCKER_PREFIX}/sprout-kernel-${TARGET_ARCH}" "kernel.efi" "${FINAL_DIR}/kernel.efi"
 	cp hack/configs/kernel.sprout.toml "${FINAL_DIR}/sprout.toml"
 fi
 
 if [ "${SKIP_VM_BUILD}" != "1" ]; then
 	echo "[vm build] ${TARGET_ARCH} ${RUST_PROFILE}"
 	docker build --platform="${DOCKER_TARGET}" -t "${DOCKER_PREFIX}/sprout-ovmf-${TARGET_ARCH}:${DOCKER_TAG}" -f vm/Dockerfile.ovmf "${FINAL_DIR}"
-	docker run --rm -i \
-		--mount="type=image,source=${DOCKER_PREFIX}/sprout-ovmf-${TARGET_ARCH}:${DOCKER_TAG},target=/image" \
-		"${DOCKER_PREFIX}/sprout-utils-copy:${DOCKER_TAG}" cat /image/ovmf.fd >"${FINAL_DIR}/ovmf.fd"
+	copy_from_image "${DOCKER_PREFIX}/sprout-ovmf-${TARGET_ARCH}" "ovmf.fd" "${FINAL_DIR}/ovmf.fd"
 fi
 
 if [ "${SKIP_SPROUT_BUILD}" != "1" ]; then
 	echo "[sprout build] ${TARGET_ARCH} ${RUST_PROFILE}"
 	docker build --platform="${DOCKER_TARGET}" -t "${DOCKER_PREFIX}/sprout-${TARGET_ARCH}:${DOCKER_TAG}" --build-arg="RUST_TARGET_SUBDIR=${RUST_TARGET_SUBDIR}" -f Dockerfile .
-	docker run --rm -i \
-		--mount="type=image,source=${DOCKER_PREFIX}/sprout-${TARGET_ARCH}:${DOCKER_TAG},target=/image" \
-		"${DOCKER_PREFIX}/sprout-utils-copy:${DOCKER_TAG}" cat /image/sprout.efi >"${FINAL_DIR}/sprout.efi"
+	copy_from_image "${DOCKER_PREFIX}/sprout-${TARGET_ARCH}" "sprout.efi" "${FINAL_DIR}/sprout.efi"
 	mkdir -p "${FINAL_DIR}/efi/EFI/BOOT"
 	cp "${FINAL_DIR}/sprout.efi" "${FINAL_DIR}/efi/EFI/BOOT/${EFI_NAME}.EFI"
 	if [ -f "${FINAL_DIR}/kernel.efi" ]; then
@@ -68,7 +90,5 @@ fi
 if [ "${SKIP_BOOT_BUILD}" != "1" ]; then
 	echo "[boot build] ${TARGET_ARCH} ${RUST_PROFILE}"
 	docker build --platform="${DOCKER_TARGET}" -t "${DOCKER_PREFIX}/sprout-boot-${TARGET_ARCH}:${DOCKER_TAG}" --build-arg "EFI_NAME=${EFI_NAME}" -f boot/Dockerfile "${FINAL_DIR}"
-	docker run --rm -i \
-		--mount="type=image,source=${DOCKER_PREFIX}/sprout-boot-${TARGET_ARCH}:${DOCKER_TAG},target=/image" \
-		"${DOCKER_PREFIX}/sprout-utils-copy:${DOCKER_TAG}" cat /image/sprout.img >"${FINAL_DIR}/sprout.img"
+	copy_from_image "${DOCKER_PREFIX}/sprout-boot-${TARGET_ARCH}" "sprout.img" "${FINAL_DIR}/sprout.img"
 fi
diff --git a/hack/clean.sh b/hack/clean.sh
index ae9a858..44d2f78 100755
--- a/hack/clean.sh
+++ b/hack/clean.sh
@@ -13,8 +13,16 @@ delete_image() {
 cargo clean || true
 
 if command -v docker >/dev/null 2>&1; then
-	delete_image sprout-utils-copy || true
-	delete_image sprout-ovmf || true
 	delete_image sprout-x86_64 || true
 	delete_image sprout-aarch64 || true
+	delete_image sprout-utils-copy-direct || true
+	delete_image sprout-utils-copy-polyfill || true
+	delete_image sprout-ovmf-x86_64 || true
+	delete_image sprout-ovmf-aarch64 || true
+	delete_image sprout-kernel-x86_64 || true
+	delete_image sprout-kernel-aarch64 || true
+	delete_image sprout-kernel-build-x86_64 || true
+	delete_image sprout-kernel-build-aarch64 || true
+	delete_image sprout-boot-x86_64 || true
+	delete_image sprout-boot-aarch64 || true
 fi
diff --git a/hack/utils/Dockerfile.copy b/hack/utils/Dockerfile.copy
deleted file mode 100644
index 6b2bdbe..0000000
--- a/hack/utils/Dockerfile.copy
+++ /dev/null
@@ -1 +0,0 @@
-FROM --platform=$BUILDPLATFORM debian:trixie@sha256:fd8f5a1df07b5195613e4b9a0b6a947d3772a151b81975db27d47f093f60c6e6
diff --git a/hack/utils/Dockerfile.copy-direct b/hack/utils/Dockerfile.copy-direct
new file mode 100644
index 0000000..545d8a9
--- /dev/null
+++ b/hack/utils/Dockerfile.copy-direct
@@ -0,0 +1 @@
+FROM --platform=$BUILDPLATFORM debian:trixie@sha256:b7e663fabda920f28abf26e7fbfe0867145645fdf3e47a42323147242151e066
diff --git a/hack/utils/Dockerfile.copy-polyfill b/hack/utils/Dockerfile.copy-polyfill
new file mode 100644
index 0000000..5061850
--- /dev/null
+++ b/hack/utils/Dockerfile.copy-polyfill
@@ -0,0 +1,4 @@
+ARG TARGET_IMAGE=scratch
+FROM ${TARGET_IMAGE} AS image
+FROM --platform=$BUILDPLATFORM debian:trixie@sha256:b7e663fabda920f28abf26e7fbfe0867145645fdf3e47a42323147242151e066 AS final
+COPY --from=image / /image