Fix gpt-auto-generator on usr-only root in presence of sysexts (#43591)

This adds a fallback to `blockdev_get_root`, to handle the case where `/usr` is a sysext overlay. Additinal changes are: - move `extension_overlay_block` to `extension-util.h`, and make it generic to work in both confext and sysext cases (though only sysext is actually used currently) - add a usr-only integration test to exercise the failure Closes #43565.
2026-09-14 09:51:37 +02:00
parent 1f66b52452 e8807add48
commit 15e79c52b7
5 changed files with 161 additions and 44 deletions
@@ -0,0 +1,93 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+set -eux
+set -o pipefail
+
+GENERATOR_BIN="/usr/lib/systemd/system-generators/systemd-gpt-auto-generator"
+WORK_DIR="$(mktemp --directory /var/tmp/test-gpt-auto-generator.XXXXXX)"
+DEFINITIONS="$WORK_DIR/definitions"
+IMAGE="$WORK_DIR/image.raw"
+OUTPUT="$WORK_DIR/output"
+ROOT="$WORK_DIR/root"
+LOOP=""
+
+at_exit() {
+    set +e
+
+    if [[ -n "$LOOP" ]]; then
+        losetup --detach "$LOOP"
+    fi
+
+    rm -rf "$WORK_DIR"
+}
+
+trap at_exit EXIT
+
+test -x "$GENERATOR_BIN"
+mkdir -p "$DEFINITIONS" "$OUTPUT"/{normal,early,late} "$ROOT"
+
+cat >"$DEFINITIONS/10-usr.conf" <<EOF
+[Partition]
+Type=usr
+SizeMinBytes=10M
+SizeMaxBytes=10M
+EOF
+
+cat >"$DEFINITIONS/20-home.conf" <<EOF
+[Partition]
+Type=home
+SizeMinBytes=10M
+SizeMaxBytes=10M
+EOF
+
+systemd-repart \
+    --definitions="$DEFINITIONS" \
+    --empty=create \
+    --size=32M \
+    --dry-run=no \
+    --offline=yes \
+    "$IMAGE"
+
+LOOP="$(losetup --show --find --partscan "$IMAGE")"
+udevadm wait --timeout=60 --settle --initialized=no "$LOOP"p1 "$LOOP"p2
+
+# Recreate a root=tmpfs system whose /usr/ is backed by a GPT partition and overlaid by systemd-sysext.
+# Run the generator as PID 1 because generators deliberately do nothing in containers.
+unshare --mount --pid --fork --mount-proc \
+    bash -euxo pipefail -s -- "$ROOT" "$OUTPUT" "$WORK_DIR" "$LOOP" "$GENERATOR_BIN" <<'EOF'
+mount --make-rprivate /
+
+mount --types tmpfs tmpfs "$1"
+mkdir -p "$1"/{dev,proc,run/generator-output,sys,usr}
+mount --bind /dev "$1/dev"
+mount --bind /proc "$1/proc"
+mount --bind /sys "$1/sys"
+mount --bind "$2" "$1/run/generator-output"
+
+mkdir -p "$3/usr-upper" "$3/usr-work"
+mount --types overlay overlay \
+    --options lowerdir=/usr,upperdir="$3/usr-upper",workdir="$3/usr-work" \
+    "$1/usr"
+
+for directory in bin lib lib64 sbin; do
+    if [[ -e "/$directory" ]]; then
+        mkdir -p "$1/$directory"
+        mount --bind "/$directory" "$1/$directory"
+    fi
+done
+
+mkdir -p "$1/usr/.systemd-sysext"
+cat "/sys/class/block/${4##*/}p1/dev" >"$1/usr/.systemd-sysext/backing"
+
+export container=
+export SYSTEMD_IN_INITRD=0
+export SYSTEMD_PROC_CMDLINE="root=tmpfs systemd.gpt_auto=yes"
+exec chroot "$1" "$5" \
+    /run/generator-output/normal \
+    /run/generator-output/early \
+    /run/generator-output/late
+EOF
+
+test -f "$OUTPUT/late/home.mount"
+WHAT="$(sed -n 's/^What=//p' "$OUTPUT/late/home.mount")"
+test "$(readlink --canonicalize "$WHAT")" = "$(readlink --canonicalize "${LOOP}p2")"