efi: Implement writing to block device

Using the SectorWrite trait added to the block device implement writing
to the block device. This is useful for bootloaders that need to write
to the block device in order to be able support fallback booting.

In particular this enables the firmware to be used with Ubuntu 19.10
("eoan".)

Signed-off-by: Rob Bradford <[email protected]>

src/efi/block.rs

@@ -145,18 +145,43 @@ pub extern "win64" fn read_blocks(
 
 #[cfg(not(test))]
 pub extern "win64" fn write_blocks(
-    _: *mut BlockIoProtocol,
+    proto: *mut BlockIoProtocol,
     _: u32,
-    _: u64,
-    _: usize,
-    _: *mut c_void,
+    start: u64,
+    size: usize,
+    buffer: *mut c_void,
 ) -> Status {
-    Status::UNSUPPORTED
+    let wrapper = container_of!(proto, BlockWrapper, proto);
+    let wrapper = unsafe { &*wrapper };
+
+    let blocks = (size / 512) as usize;
+    let mut region = crate::mem::MemoryRegion::new(buffer as u64, size as u64);
+
+    for i in 0..blocks {
+        use crate::block::SectorWrite;
+        let data = region.as_mut_slice(i as u64 * 512, 512);
+        let block = unsafe { &*wrapper.block };
+        match block.write(wrapper.start_lba + start + i as u64, data) {
+            Ok(()) => continue,
+            Err(_) => {
+                return Status::DEVICE_ERROR;
+            }
+        };
+    }
+
+    Status::SUCCESS
 }
 
 #[cfg(not(test))]
-pub extern "win64" fn flush_blocks(_: *mut BlockIoProtocol) -> Status {
-    Status::UNSUPPORTED
+pub extern "win64" fn flush_blocks(proto: *mut BlockIoProtocol) -> Status {
+    let wrapper = container_of!(proto, BlockWrapper, proto);
+    let wrapper = unsafe { &*wrapper };
+    use crate::block::SectorWrite;
+    let block = unsafe { &*wrapper.block };
+    match block.flush() {
+        Ok(()) => Status::SUCCESS,
+        Err(_) => Status::DEVICE_ERROR,
+    }
 }
 
 #[cfg(not(test))]