chore(code): split much of the efi support code to crates/eficore

crates/eficore/src/partition.rs

@@ -0,0 +1,55 @@
+use anyhow::{Context, Result};
+use uefi::Guid;
+use uefi::proto::device_path::DevicePath;
+use uefi::proto::media::partition::PartitionInfo;
+use uefi_raw::Status;
+
+/// Represents the type of partition GUID that can be retrieved.
+#[derive(PartialEq, Eq)]
+pub enum PartitionGuidForm {
+    /// The partition GUID is the unique partition GUID.
+    Partition,
+    /// The partition GUID is the partition type GUID.
+    PartitionType,
+}
+
+/// Retrieve the partition / partition type GUID of the device root `path`.
+/// This only works on GPT partitions. If the root is not a GPT partition, None is returned.
+/// If the GUID is all zeros, this will return None.
+pub fn partition_guid(path: &DevicePath, form: PartitionGuidForm) -> Result<Option<Guid>> {
+    // Clone the path so we can pass it to the UEFI stack.
+    let path = path.to_boxed();
+    let result = uefi::boot::locate_device_path::<PartitionInfo>(&mut &*path);
+    let handle = match result {
+        Ok(handle) => Ok(Some(handle)),
+        Err(error) => {
+            // If the error is NOT_FOUND or UNSUPPORTED, we can return None.
+            // These are non-fatal errors.
+            if error.status() == Status::NOT_FOUND || error.status() == Status::UNSUPPORTED {
+                Ok(None)
+            } else {
+                Err(error)
+            }
+        }
+    }
+    .context("unable to locate device path")?;
+
+    // If we have the handle, we can try to open the partition info protocol.
+    if let Some(handle) = handle {
+        // Open the partition info protocol.
+        let partition_info = uefi::boot::open_protocol_exclusive::<PartitionInfo>(handle)
+            .context("unable to open partition info protocol")?;
+        // Find the unique partition GUID.
+        // If this is not a GPT partition, this will produce None.
+        Ok(partition_info
+            .gpt_partition_entry()
+            .map(|entry| match form {
+                // Match the form of the partition GUID.
+                PartitionGuidForm::Partition => entry.unique_partition_guid,
+                PartitionGuidForm::PartitionType => entry.partition_type_guid.0,
+            })
+            .filter(|guid| !guid.is_zero()))
+    } else {
+        Ok(None)
+    }
+}