loader: support loading device tree on aarch64

Signed-off-by: Qiu Wenbo <qiuwenbo@phytium.com.cn>

Author: crab2313

src/loader/mod.rs

@@ -52,6 +52,8 @@ pub enum Error {
     CommandLineCopy,
     /// Command line overflowed guest memory.
     CommandLineOverflow,
+    /// Device tree bianry too big.
+    DtbTooBig,
     /// Invalid ELF magic number
     InvalidElfMagicNumber,
     /// Invalid program header size.
@@ -84,6 +86,8 @@ pub enum Error {
     ReadBzImageCompressedKernel,
     /// Unable to read Image header
     ReadImageHeader,
+    /// Unable to read DTB image
+    ReadDtbImage,
     /// Unable to seek to kernel start.
     SeekKernelStart,
     /// Unable to seek to ELF start.
@@ -100,6 +104,10 @@ pub enum Error {
     SeekImageEnd,
     /// Unable to seek to Image header.
     SeekImageHeader,
+    /// Unable to seek to DTB start.
+    SeekDtbStart,
+    /// Unable to seek to DTB end.
+    SeekDtbEnd,
 }
 
 /// A specialized `Result` type for the kernel loader.
@@ -113,6 +121,7 @@ impl error::Error for Error {
             }
             Error::CommandLineCopy => "Failed writing command line to guest memory",
             Error::CommandLineOverflow => "Command line overflowed guest memory",
+            Error::DtbTooBig => "Device tree image too big",
             Error::InvalidElfMagicNumber => "Invalid Elf magic number",
             Error::InvalidProgramHeaderSize => "Invalid program header size",
             Error::InvalidProgramHeaderOffset => "Invalid program header offset",
@@ -128,6 +137,7 @@ impl error::Error for Error {
             Error::ReadProgramHeader => "Unable to read program header",
             Error::ReadBzImageHeader => "Unable to read bzImage header",
             Error::ReadImageHeader => "Unable to read Image header",
+            Error::ReadDtbImage => "Unable to read DTB image",
             Error::ReadBzImageCompressedKernel => "Unable to read bzImage compressed kernel",
             Error::SeekKernelStart => "Unable to seek to kernel start",
             Error::SeekElfStart => "Unable to seek to elf start",
@@ -137,6 +147,8 @@ impl error::Error for Error {
             Error::SeekBzImageCompressedKernel => "Unable to seek bzImage compressed kernel",
             Error::SeekImageEnd => "Unable to seek Image end",
             Error::SeekImageHeader => "Unable to seek image header",
+            Error::SeekDtbStart => "Unable to seek DTB start",
+            Error::SeekDtbEnd => "Unable to seek DTB end",
         }
     }
 }
@@ -422,6 +434,34 @@ pub fn load_cmdline<M: GuestMemory>(
     Ok(())
 }
 
+/// Writes the device tree to the given memory slice.
+///
+/// # Arguments
+///
+/// * `guest_mem` - A u8 slice that will be partially overwritten by the device tree blob.
+/// * `guest_addr` - The address in `guest_mem` at which to load the device tree blob.
+/// * `dtb_image` - The device tree blob.
+#[cfg(target_arch = "aarch64")]
+pub fn load_dtb<F, M: GuestMemory>(
+        guest_mem: &M,
+        guest_addr: GuestAddress,
+        dtb_image: &mut F,
+    ) -> Result<()>
+    where F: Read + Seek
+{
+    let dtb_size = dtb_image
+            .seek(SeekFrom::End(0))
+            .map_err(|_| Error::SeekDtbEnd)? as usize;
+    if dtb_size > 0x200000 {
+        return Err(Error::DtbTooBig);
+    }
+    dtb_image.seek(SeekFrom::Start(0))
+                .map_err(|_| Error::SeekDtbStart)?;
+    guest_mem
+        .read_exact_from(guest_addr, dtb_image, dtb_size)
+            .map_err(|_| Error::ReadDtbImage)
+}
+
 #[cfg(feature = "image")]
 #[cfg(target_arch = "aarch64")]
 /// ARM64 Image (PE) format support