efi: Consistently support filenames up to 256 characters

Previously the path in the FileDevicePathProtocol was limited to 128
ascii characters.

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>

src/efi/file.rs

@@ -16,7 +16,7 @@ use crate::block::SectorBuf;
 #[repr(C)]
 pub struct FileDevicePathProtocol {
     pub device_path: DevicePathProtocol,
-    pub filename: [u16; 64],
+    pub filename: [u16; 128],
 }
 
 pub extern "efiapi" fn filesystem_open_volume(

src/efi/mod.rs

@@ -1067,17 +1067,17 @@ fn file_device_path(path: &str) -> *mut r_efi::protocols::device_path::Protocol
             device_path: DevicePathProtocol {
                 r#type: r_efi::protocols::device_path::TYPE_MEDIA,
                 sub_type: 4, // Media Path type file
-                length: [132, 0],
+                length: [(260u16 & 0xff) as u8, (260u16 >> 8) as u8],
             },
-            filename: [0; 64],
+            filename: [0; 128],
         },
         file::FileDevicePathProtocol {
             device_path: DevicePathProtocol {
                 r#type: r_efi::protocols::device_path::TYPE_END,
                 sub_type: 0xff, // End of full path
                 length: [4, 0],
             },
-            filename: [0; 64],
+            filename: [0; 128],
         },
     ];