arch: riscv: Introduce UEFI module

Provide Error definitions and load_uefi to be referenced while loading
firmware.

Signed-off-by: Ruoqing He <heruoqing@iscas.ac.cn>

arch/src/riscv64/mod.rs

@@ -7,6 +7,8 @@
 pub mod fdt;
 /// Layout for this riscv64 system.
 pub mod layout;
+/// Module for loading UEFI binary.
+pub mod uefi;
 
 use std::collections::HashMap;
 use std::fmt::Debug;

arch/src/riscv64/uefi.rs

@@ -0,0 +1,50 @@
+// Copyright 2020 Arm Limited (or its affiliates). All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+use std::io::{Read, Seek, SeekFrom};
+use std::os::fd::AsFd;
+use std::result;
+
+use thiserror::Error;
+use vm_memory::{GuestAddress, GuestMemory};
+
+/// Errors thrown while loading UEFI binary
+#[derive(Debug, Error)]
+pub enum Error {
+    /// Unable to seek to UEFI image start.
+    #[error("Unable to seek to UEFI image start")]
+    SeekUefiStart,
+    /// Unable to seek to UEFI image end.
+    #[error("Unable to seek to UEFI image end")]
+    SeekUefiEnd,
+    /// UEFI image too big.
+    #[error("UEFI image too big")]
+    UefiTooBig,
+    /// Unable to read UEFI image
+    #[error("Unable to read UEFI image")]
+    ReadUefiImage,
+}
+type Result<T> = result::Result<T, Error>;
+
+pub fn load_uefi<F, M: GuestMemory>(
+    guest_mem: &M,
+    guest_addr: GuestAddress,
+    uefi_image: &mut F,
+) -> Result<()>
+where
+    F: Read + Seek + AsFd,
+{
+    let uefi_size = uefi_image
+        .seek(SeekFrom::End(0))
+        .map_err(|_| Error::SeekUefiEnd)? as usize;
+
+    // edk2 image on virtual platform is smaller than 3M
+    if uefi_size > 0x300000 {
+        return Err(Error::UefiTooBig);
+    }
+    uefi_image.rewind().map_err(|_| Error::SeekUefiStart)?;
+    guest_mem
+        .read_exact_volatile_from(guest_addr, &mut uefi_image.as_fd(), uefi_size)
+        .map_err(|_| Error::ReadUefiImage)
+}