block_util, vmm: Add fixed VHD asynchronous implementation

This commit adds the asynchronous support for fixed VHD disk files.

It introduces FixedVhd as a new ImageType, moving the image type
detection to the block_util crate (instead of qcow crate).

It creates a new vhd module in the block_util crate in order to handle
VHD footer, following the VHD specification.

It creates a new fixed_vhd_async module in the block_util crate to
implement the asynchronous version of fixed VHD disk file. It relies on
io_uring.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

block_util/src/vhd.rs

@@ -0,0 +1,120 @@
+// Copyright © 2021 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+
+use std::convert::TryInto;
+use std::fs::File;
+use std::io::{Read, Seek, SeekFrom};
+
+#[derive(Clone, Copy)]
+pub struct VhdFooter {
+    cookie: u64,
+    features: u32,
+    file_format_version: u32,
+    data_offset: u64,
+    time_stamp: u32,
+    creator_application: u32,
+    creator_version: u32,
+    creator_host_os: u32,
+    original_size: u64,
+    current_size: u64,
+    disk_geometry: u32,
+    disk_type: u32,
+    checksum: u32,
+    unique_id: u128,
+    saved_state: u8,
+}
+
+impl VhdFooter {
+    pub fn new(file: &mut File) -> std::io::Result<VhdFooter> {
+        // We must create a buffer aligned on 512 bytes with a size being a
+        // multiple of 512 bytes as the file might be opened with O_DIRECT flag.
+        #[repr(align(512))]
+        struct Sector {
+            data: [u8; 512],
+        }
+        let mut s = Sector { data: [0; 512] };
+
+        // Place the cursor 512 bytes before the end of the file, as this is
+        // where the footer starts.
+        file.seek(SeekFrom::End(-512))?;
+
+        // Fill in the VhdFooter structure
+        file.read_exact(&mut s.data)?;
+
+        Ok(VhdFooter {
+            cookie: u64::from_be_bytes(s.data[0..8].try_into().unwrap()),
+            features: u32::from_be_bytes(s.data[8..12].try_into().unwrap()),
+            file_format_version: u32::from_be_bytes(s.data[12..16].try_into().unwrap()),
+            data_offset: u64::from_be_bytes(s.data[16..24].try_into().unwrap()),
+            time_stamp: u32::from_be_bytes(s.data[24..28].try_into().unwrap()),
+            creator_application: u32::from_be_bytes(s.data[28..32].try_into().unwrap()),
+            creator_version: u32::from_be_bytes(s.data[32..36].try_into().unwrap()),
+            creator_host_os: u32::from_be_bytes(s.data[36..40].try_into().unwrap()),
+            original_size: u64::from_be_bytes(s.data[40..48].try_into().unwrap()),
+            current_size: u64::from_be_bytes(s.data[48..56].try_into().unwrap()),
+            disk_geometry: u32::from_be_bytes(s.data[56..60].try_into().unwrap()),
+            disk_type: u32::from_be_bytes(s.data[60..64].try_into().unwrap()),
+            checksum: u32::from_be_bytes(s.data[64..68].try_into().unwrap()),
+            unique_id: u128::from_be_bytes(s.data[68..84].try_into().unwrap()),
+            saved_state: u8::from_be_bytes(s.data[84..85].try_into().unwrap()),
+        })
+    }
+
+    pub fn cookie(&self) -> u64 {
+        self.cookie
+    }
+    pub fn features(&self) -> u32 {
+        self.features
+    }
+    pub fn file_format_version(&self) -> u32 {
+        self.file_format_version
+    }
+    pub fn data_offset(&self) -> u64 {
+        self.data_offset
+    }
+    pub fn time_stamp(&self) -> u32 {
+        self.time_stamp
+    }
+    pub fn creator_application(&self) -> u32 {
+        self.creator_application
+    }
+    pub fn creator_version(&self) -> u32 {
+        self.creator_version
+    }
+    pub fn creator_host_os(&self) -> u32 {
+        self.creator_host_os
+    }
+    pub fn original_size(&self) -> u64 {
+        self.original_size
+    }
+    pub fn current_size(&self) -> u64 {
+        self.current_size
+    }
+    pub fn disk_geometry(&self) -> u32 {
+        self.disk_geometry
+    }
+    pub fn disk_type(&self) -> u32 {
+        self.disk_type
+    }
+    pub fn checksum(&self) -> u32 {
+        self.checksum
+    }
+    pub fn unique_id(&self) -> u128 {
+        self.unique_id
+    }
+    pub fn saved_state(&self) -> u8 {
+        self.saved_state
+    }
+}
+
+/// Determine image type through file parsing.
+pub fn is_fixed_vhd(f: &mut File) -> std::io::Result<bool> {
+    let footer = VhdFooter::new(f)?;
+
+    // "conectix" => 0x636f6e6563746978
+    Ok(footer.cookie() == 0x636f6e6563746978
+        && footer.file_format_version() == 0x0001_0000
+        && footer.data_offset() == 0xffff_ffff_ffff_ffff
+        && footer.disk_type() == 0x2)
+}