crates: Add discoverable partition module and parttype APIs

This fleshes out what we had with a more rigorous
binding to the spec.

As part of this though, the ESP constant we had here was uppercase,
but the spec version uses lowercase. Add APIs to find a partition
by type, comparing case insensitively.

Assisted-by: Claude Code
Signed-off-by: Colin Walters <[email protected]>

Author: cgwalters

Cargo.lock

@@ -36,6 +36,7 @@ anyhow = "1.0.82"
 camino = "1.1.6"
 canon-json = "0.2.1"
 cap-std-ext = "4.0.3"
+cfg-if = "1.0"
 chrono = { version = "0.4.38", default-features = false }
 clap = "4.5.4"
 clap_mangen = { version = "0.2.20" }

Cargo.toml

@@ -161,13 +161,29 @@ impl PartitionTable {
             .ok_or_else(|| anyhow::anyhow!("Missing partition for index {partno}"))?;
         Ok(r)
     }
+
+    /// Find the partition with the given type UUID (case-insensitive).
+    ///
+    /// Partition type UUIDs are compared case-insensitively per the GPT specification,
+    /// as different tools may report them in different cases.
+    pub fn find_partition_of_type(&self, uuid: &str) -> Option<&Partition> {
+        self.partitions.iter().find(|p| p.parttype_matches(uuid))
+    }
 }
 
 impl Partition {
     #[allow(dead_code)]
     pub fn path(&self) -> &Utf8Path {
         self.node.as_str().into()
     }
+
+    /// Check if this partition's type matches the given UUID (case-insensitive).
+    ///
+    /// Partition type UUIDs are compared case-insensitively per the GPT specification,
+    /// as different tools may report them in different cases.
+    pub fn parttype_matches(&self, uuid: &str) -> bool {
+        self.parttype.eq_ignore_ascii_case(uuid)
+    }
 }
 
 #[context("Listing partitions of {dev}")]
@@ -505,4 +521,85 @@ mod test {
         );
         Ok(())
     }
+
+    #[test]
+    fn test_parttype_matches() {
+        let partition = Partition {
+            node: "/dev/loop0p1".to_string(),
+            start: 2048,
+            size: 8192,
+            parttype: "c12a7328-f81f-11d2-ba4b-00a0c93ec93b".to_string(), // lowercase ESP UUID
+            uuid: Some("58A4C5F0-BD12-424C-B563-195AC65A25DD".to_string()),
+            name: Some("EFI System".to_string()),
+        };
+
+        // Test exact match (lowercase)
+        assert!(partition.parttype_matches("c12a7328-f81f-11d2-ba4b-00a0c93ec93b"));
+
+        // Test case-insensitive match (uppercase)
+        assert!(partition.parttype_matches("C12A7328-F81F-11D2-BA4B-00A0C93EC93B"));
+
+        // Test case-insensitive match (mixed case)
+        assert!(partition.parttype_matches("C12a7328-F81f-11d2-Ba4b-00a0C93ec93b"));
+
+        // Test non-match
+        assert!(!partition.parttype_matches("0FC63DAF-8483-4772-8E79-3D69D8477DE4"));
+    }
+
+    #[test]
+    fn test_find_partition_of_type() -> Result<()> {
+        let fixture = indoc::indoc! { r#"
+        {
+            "partitiontable": {
+               "label": "gpt",
+               "id": "A67AA901-2C72-4818-B098-7F1CAC127279",
+               "device": "/dev/loop0",
+               "unit": "sectors",
+               "firstlba": 34,
+               "lastlba": 20971486,
+               "sectorsize": 512,
+               "partitions": [
+                  {
+                     "node": "/dev/loop0p1",
+                     "start": 2048,
+                     "size": 8192,
+                     "type": "C12A7328-F81F-11D2-BA4B-00A0C93EC93B",
+                     "uuid": "58A4C5F0-BD12-424C-B563-195AC65A25DD",
+                     "name": "EFI System"
+                  },{
+                     "node": "/dev/loop0p2",
+                     "start": 10240,
+                     "size": 20961247,
+                     "type": "0FC63DAF-8483-4772-8E79-3D69D8477DE4",
+                     "uuid": "F51ABB0D-DA16-4A21-83CB-37F4C805AAA0",
+                     "name": "root"
+                  }
+               ]
+            }
+         }
+        "# };
+        let table: SfDiskOutput = serde_json::from_str(fixture).unwrap();
+
+        // Find ESP partition using lowercase UUID (should match uppercase in fixture)
+        let esp = table
+            .partitiontable
+            .find_partition_of_type("c12a7328-f81f-11d2-ba4b-00a0c93ec93b");
+        assert!(esp.is_some());
+        assert_eq!(esp.unwrap().node, "/dev/loop0p1");
+
+        // Find root partition using uppercase UUID (should match case-insensitively)
+        let root = table
+            .partitiontable
+            .find_partition_of_type("0fc63daf-8483-4772-8e79-3d69d8477de4");
+        assert!(root.is_some());
+        assert_eq!(root.unwrap().node, "/dev/loop0p2");
+
+        // Try to find non-existent partition type
+        let nonexistent = table
+            .partitiontable
+            .find_partition_of_type("00000000-0000-0000-0000-000000000000");
+        assert!(nonexistent.is_none());
+
+        Ok(())
+    }
 }

crates/blockdev/src/blockdev.rs

@@ -30,6 +30,7 @@ anyhow = { workspace = true }
 camino = { workspace = true, features = ["serde1"] }
 canon-json = { workspace = true }
 cap-std-ext = { workspace = true, features = ["fs_utf8"] }
+cfg-if = { workspace = true }
 chrono = { workspace = true, features = ["serde"] }
 clap = { workspace = true, features = ["derive","cargo"] }
 clap_mangen = { workspace = true, optional = true }

crates/lib/Cargo.toml

@@ -44,7 +44,8 @@ use crate::{
         BOOT_LOADER_ENTRIES, COMPOSEFS_CMDLINE, ORIGIN_KEY_BOOT, ORIGIN_KEY_BOOT_DIGEST,
         STAGED_BOOT_LOADER_ENTRIES, STATE_DIR_ABS, USER_CFG, USER_CFG_STAGED,
     },
-    install::{dps_uuid::DPS_UUID, RW_KARG},
+    discoverable_partition_specification::this_arch_root,
+    install::RW_KARG,
     spec::{Bootloader, Host},
 };
 
@@ -400,7 +401,7 @@ pub(crate) fn setup_composefs_bls_boot(
                 Utf8PathBuf::from("/sysroot"),
                 get_esp_partition(&sysroot_parent)?.0,
                 [
-                    format!("root=UUID={DPS_UUID}"),
+                    format!("root=UUID={}", this_arch_root()),
                     RW_KARG.to_string(),
                     format!("{COMPOSEFS_CMDLINE}={id_hex}"),
                 ]

crates/lib/src/bootc_composefs/boot.rs

@@ -10,23 +10,19 @@ use bootc_mount as mount;
 
 #[cfg(any(feature = "composefs-backend", feature = "install-to-disk"))]
 use crate::bootc_composefs::boot::mount_esp;
-use crate::utils;
+use crate::{discoverable_partition_specification, utils};
 
 /// The name of the mountpoint for efi (as a subdirectory of /boot, or at the toplevel)
 pub(crate) const EFI_DIR: &str = "efi";
 /// The EFI system partition GUID
-#[allow(dead_code)]
-pub(crate) const ESP_GUID: &str = "C12A7328-F81F-11D2-BA4B-00A0C93EC93B";
 /// Path to the bootupd update payload
 #[allow(dead_code)]
 const BOOTUPD_UPDATES: &str = "usr/lib/bootupd/updates";
 
 #[allow(dead_code)]
 pub(crate) fn esp_in(device: &PartitionTable) -> Result<&Partition> {
     device
-        .partitions
-        .iter()
-        .find(|p| p.parttype.as_str() == ESP_GUID)
+        .find_partition_of_type(discoverable_partition_specification::ESP)
         .ok_or(anyhow::anyhow!("ESP not found in partition table"))
 }
 
@@ -84,9 +80,7 @@ pub(crate) fn install_systemd_boot(
     _deployment_path: Option<&str>,
 ) -> Result<()> {
     let esp_part = device
-        .partitions
-        .iter()
-        .find(|p| p.parttype.as_str() == ESP_GUID)
+        .find_partition_of_type(discoverable_partition_specification::ESP)
         .ok_or_else(|| anyhow::anyhow!("ESP partition not found"))?;
 
     let esp_mount = mount_esp(&esp_part.node).context("Mounting ESP")?;