[PATCH v3] initramfs-framework: support LABEL with root-only udev trigger

[Wenwen Fu <wenwfu@qti.qualcomm.com>]

Filesystem labels are not available in kernel uevents. Add
util-linux-findfs to initramfs-module-udev and use findfs to resolve
root=LABEL= to a device. Read the kernel-provided PARTUUID from sysfs
and trigger only that partition, falling back to a full trigger if the
label cannot be resolved safely. Keeping findfs out of the BusyBox
defconfig avoids increasing BusyBox for unrelated users.

Exclude the util-linux dependency from signature propagation because
this allarch recipe only invokes findfs at runtime.

Tested with bitbake -p, the core-image-minimal-initramfs dependency
graph, and the sstatetests.SStateHashSameSigs2.test_sstate_allarch_samesigs
selftest.

AI-Generated: OpenAI Codex
Signed-off-by: Wenwen Fu <wenwfu@qti.qualcomm.com>
---
Changes in v3:
- Exclude the util-linux dependency from initramfs-framework signatures
  to preserve allarch sstate reuse across machines.
- Validate the fix with the allarch sstate signature selftest.

Changes in v2:
- Keep findfs out of the default BusyBox configuration.
- Add util-linux-findfs as an initramfs-module-udev runtime dependency.
---

 meta/conf/layer.conf                                 |  1 +
 .../initrdscripts/initramfs-framework/udev           | 12 ++++++++++++
 .../initrdscripts/initramfs-framework_1.0.bb         |  2 +-
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/meta/conf/layer.conf b/meta/conf/layer.conf
index b91ce3e437..1ad34b430d 100644
--- a/meta/conf/layer.conf
+++ b/meta/conf/layer.conf
@@ -61,6 +61,7 @@ SIGGEN_EXCLUDE_SAFE_RECIPE_DEPS += " \
   initramfs-framework->${VIRTUAL-RUNTIME_base-utils} \
   initramfs-framework->eudev \
   initramfs-framework->systemd \
+  initramfs-framework->util-linux \
   initramfs-module-install-efi->dosfstools \
   initramfs-module-install-efi->e2fsprogs \
   initramfs-module-install-efi->parted \
diff --git a/meta/recipes-core/initrdscripts/initramfs-framework/udev b/meta/recipes-core/initrdscripts/initramfs-framework/udev
index 8f67e78a7c..85c5ba1178 100644
--- a/meta/recipes-core/initrdscripts/initramfs-framework/udev
+++ b/meta/recipes-core/initrdscripts/initramfs-framework/udev
@@ -43,6 +43,18 @@ udev_trigger_root_device() {
 		PARTUUID=?*)
 			root_match="PARTUUID=${bootparam_root#PARTUUID=}"
 			;;
+		LABEL=?*)
+			# The kernel does not export the filesystem LABEL in the
+			# uevent, so resolve it to a device node with findfs and
+			# match on that device's kernel-provided PARTUUID.
+			root_label="${bootparam_root#LABEL=}"
+			root_dev=$(findfs "LABEL=$root_label" 2>/dev/null) || return 1
+			[ -n "$root_dev" ] || return 1
+			root_partuuid=$(sed -n 's/^PARTUUID=//p' \
+				"/sys/class/block/${root_dev#/dev/}/uevent" 2>/dev/null)
+			[ -n "$root_partuuid" ] || return 1
+			root_match="PARTUUID=$root_partuuid"
+			;;
 		*)
 			return 1
 			;;
diff --git a/meta/recipes-core/initrdscripts/initramfs-framework_1.0.bb b/meta/recipes-core/initrdscripts/initramfs-framework_1.0.bb
index 2ec03bc34c..936cd0c995 100644
--- a/meta/recipes-core/initrdscripts/initramfs-framework_1.0.bb
+++ b/meta/recipes-core/initrdscripts/initramfs-framework_1.0.bb
@@ -88,7 +88,7 @@ RDEPENDS:initramfs-module-mdev = "${PN}-base busybox-mdev"
 FILES:initramfs-module-mdev = "/init.d/01-mdev"
 
 SUMMARY:initramfs-module-udev = "initramfs support for udev"
-RDEPENDS:initramfs-module-udev = "${PN}-base udev"
+RDEPENDS:initramfs-module-udev = "${PN}-base udev util-linux-findfs"
 FILES:initramfs-module-udev = "/init.d/01-udev"
 
 SUMMARY:initramfs-module-e2fs = "initramfs support for ext4/ext3/ext2 filesystems"
-- 
2.43.0