patina: Add EFI_RAM_DISK_PROTOCOL bindings

Adds sdk/patina/src/uefi_protocol/ram_disk.rs implementing the FFI
binding for EFI_RAM_DISK_PROTOCOL per UEFI 2.10 section 13.16. Exposes
the Protocol struct, RegisterFn / UnregisterFn type aliases, and the
four well-known RamDiskType GUIDs (virtual disk, virtual CD, persistent
variants).

Used by the SRE flow to install the recovery WIM as a virtual block
device after reading it out of the NVMe boot partition into RAM.

Adds two unit tests covering the protocol GUID against the UEFI-spec
value and the distinctness of the four RamDiskType GUIDs.

Closes #65.

Author: kat-perez

sdk/patina/src/uefi_protocol.rs

@@ -9,6 +9,7 @@
 
 pub mod decompress;
 pub mod performance_measurement;
+pub mod ram_disk;
 pub mod status_code;
 
 use crate::BinaryGuid;

sdk/patina/src/uefi_protocol/ram_disk.rs

@@ -0,0 +1,99 @@
+//! UEFI RAM Disk Protocol bindings (UEFI 2.10 §13.16).
+//!
+//! Used to install a contiguous range of system memory as a virtual block device the system
+//! firmware can boot from. The SRE flow uses this to boot the recovery WIM after reading it
+//! out of the NVMe boot partition into RAM.
+//!
+//! ## License
+//!
+//! Copyright (c) Microsoft Corporation.
+//!
+//! SPDX-License-Identifier: Apache-2.0
+//!
+use r_efi::efi;
+
+use crate::uefi_protocol::ProtocolInterface;
+
+/// Well-known `RamDiskType` GUID for a generic virtual disk.
+pub const RAM_DISK_VIRTUAL_DISK_GUID: efi::Guid =
+    efi::Guid::from_fields(0x77ab535a, 0x45fc, 0x624b, 0x55, 0x60, &[0xf7, 0xb2, 0x81, 0xd1, 0xf9, 0x6e]);
+
+/// Well-known `RamDiskType` GUID for a virtual CD (ISO9660) image.
+pub const RAM_DISK_VIRTUAL_CD_GUID: efi::Guid =
+    efi::Guid::from_fields(0x3d5abd30, 0x4175, 0x87ce, 0x6d, 0x64, &[0xd2, 0xad, 0xe5, 0x23, 0xc4, 0xbb]);
+
+/// Well-known `RamDiskType` GUID for a persistent virtual disk.
+pub const RAM_DISK_PERSISTENT_VIRTUAL_DISK_GUID: efi::Guid =
+    efi::Guid::from_fields(0x5cea02c9, 0x4d07, 0x69d3, 0x26, 0x9f, &[0x44, 0x96, 0xfb, 0xe0, 0x96, 0xf9]);
+
+/// Well-known `RamDiskType` GUID for a persistent virtual CD.
+pub const RAM_DISK_PERSISTENT_VIRTUAL_CD_GUID: efi::Guid =
+    efi::Guid::from_fields(0x08018188, 0x42cd, 0xbb48, 0x10, 0x0f, &[0x53, 0x87, 0xd5, 0x3d, 0xed, 0x3d]);
+
+/// FFI type for `EFI_RAM_DISK_REGISTER_RAMDISK`.
+///
+/// Installs a `[ram_disk_base, ram_disk_base + ram_disk_size)` memory range as a RAM disk of
+/// type `ram_disk_type`. When `parent_device_path` is null, the protocol creates a virtual
+/// device-path root; otherwise the new RAM disk is appended under the supplied path. On
+/// success the resulting device path is written to `*device_path` (caller-owned, do not free
+/// before calling `Unregister`).
+pub type RegisterFn = extern "efiapi" fn(
+    ram_disk_base: u64,
+    ram_disk_size: u64,
+    ram_disk_type: *mut efi::Guid,
+    parent_device_path: *mut efi::protocols::device_path::Protocol,
+    device_path: *mut *mut efi::protocols::device_path::Protocol,
+) -> efi::Status;
+
+/// FFI type for `EFI_RAM_DISK_UNREGISTER_RAMDISK`.
+///
+/// Removes a previously-installed RAM disk identified by the device path returned from
+/// `Register`. The backing memory is **not** freed by this call — the caller owns its
+/// lifetime.
+pub type UnregisterFn = extern "efiapi" fn(device_path: *mut efi::protocols::device_path::Protocol) -> efi::Status;
+
+/// FFI binding for `EFI_RAM_DISK_PROTOCOL` per UEFI 2.10 §13.16.
+#[repr(C)]
+pub struct Protocol {
+    pub register: RegisterFn,
+    pub unregister: UnregisterFn,
+}
+
+// SAFETY: Layout matches the UEFI 2.10 §13.16 protocol struct (two efiapi function pointers).
+// PROTOCOL_GUID matches the UEFI-spec value (AB38A0DF-6873-44A9-87E6-D4EB56148449).
+unsafe impl ProtocolInterface for Protocol {
+    const PROTOCOL_GUID: crate::BinaryGuid = crate::BinaryGuid::from_string("AB38A0DF-6873-44A9-87E6-D4EB56148449");
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::uefi_protocol::ProtocolInterface;
+
+    #[test]
+    fn protocol_guid_matches_uefi_spec() {
+        // EFI_RAM_DISK_PROTOCOL_GUID per UEFI 2.10 §13.16.
+        let expected =
+            efi::Guid::from_fields(0xab38a0df, 0x6873, 0x44a9, 0x87, 0xe6, &[0xd4, 0xeb, 0x56, 0x14, 0x84, 0x49]);
+        assert_eq!(
+            *Protocol::PROTOCOL_GUID.0.as_bytes(),
+            *expected.as_bytes(),
+            "RAM Disk protocol GUID must match UEFI 2.10 §13.16"
+        );
+    }
+
+    #[test]
+    fn ram_disk_type_guids_are_distinct() {
+        let virtual_disk = *RAM_DISK_VIRTUAL_DISK_GUID.as_bytes();
+        let virtual_cd = *RAM_DISK_VIRTUAL_CD_GUID.as_bytes();
+        let persistent = *RAM_DISK_PERSISTENT_VIRTUAL_DISK_GUID.as_bytes();
+        let persistent_cd = *RAM_DISK_PERSISTENT_VIRTUAL_CD_GUID.as_bytes();
+
+        assert_ne!(virtual_disk, virtual_cd);
+        assert_ne!(virtual_disk, persistent);
+        assert_ne!(virtual_disk, persistent_cd);
+        assert_ne!(virtual_cd, persistent);
+        assert_ne!(virtual_cd, persistent_cd);
+        assert_ne!(persistent, persistent_cd);
+    }
+}