replace struct_util with ByteValued from vm-memory

Fixes #20
Closes rust-vmm/vmm-sys-util#77

Signed-off-by: Alexandra Iordache <aghecen@amazon.com>

Author: Alexandra Iordache

src/loader/mod.rs

@@ -27,7 +27,9 @@ use std::io::{Read, Seek};
 #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 use std::mem;
 
-use vm_memory::{Address, Bytes, GuestAddress, GuestMemory, GuestUsize};
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+use vm_memory::VolatileMemory;
+use vm_memory::{Address, ByteValued, Bytes, GuestAddress, GuestMemory, GuestUsize};
 
 #[allow(dead_code)]
 #[allow(non_camel_case_types)]
@@ -42,9 +44,6 @@ pub mod bootparam;
 #[allow(non_upper_case_globals)]
 #[cfg_attr(feature = "cargo-clippy", allow(clippy::all))]
 mod elf;
-#[cfg(any(feature = "elf", feature = "bzimage"))]
-#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
-mod struct_util;
 
 #[derive(Debug, PartialEq)]
 /// Kernel loader errors.
@@ -171,6 +170,15 @@ pub trait KernelLoader {
 /// Raw ELF (a.k.a. vmlinux) kernel image support.
 pub struct Elf;
 
+#[cfg(feature = "elf")]
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+unsafe impl ByteValued for elf::Elf64_Ehdr {}
+#[cfg(feature = "elf")]
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+unsafe impl ByteValued for elf::Elf64_Phdr {}
+
+unsafe impl ByteValued for bootparam::setup_header {}
+
 #[cfg(feature = "elf")]
 #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 impl KernelLoader for Elf {
@@ -196,14 +204,17 @@ impl KernelLoader for Elf {
     where
         F: Read + Seek,
     {
-        let mut ehdr: elf::Elf64_Ehdr = Default::default();
         kernel_image
             .seek(SeekFrom::Start(0))
             .map_err(|_| Error::SeekElfStart)?;
-        unsafe {
-            // read_struct is safe when reading a POD struct.  It can be used and dropped without issue.
-            struct_util::read_struct(kernel_image, &mut ehdr).map_err(|_| Error::ReadElfHeader)?;
-        }
+
+        // TODO: use `Bytes` trait methods when rust-vmm/vm-memory#83 is merged.
+        let ehdr_bytes = &mut [0u8; mem::size_of::<elf::Elf64_Ehdr>()][..];
+        ehdr_bytes
+            .as_volatile_slice()
+            .read_from(0, kernel_image, ehdr_bytes.len())
+            .map_err(|_| Error::ReadElfHeader)?;
+        let ehdr = elf::Elf64_Ehdr::from_mut_slice(ehdr_bytes).ok_or(Error::ReadElfHeader)?;
 
         // Sanity checks
         if ehdr.e_ident[elf::EI_MAG0 as usize] != elf::ELFMAG0 as u8
@@ -238,14 +249,24 @@ impl KernelLoader for Elf {
         kernel_image
             .seek(SeekFrom::Start(ehdr.e_phoff))
             .map_err(|_| Error::SeekProgramHeader)?;
-        let phdrs: Vec<elf::Elf64_Phdr> = unsafe {
-            // Reading the structs is safe for a slice of POD structs.
-            struct_util::read_struct_slice(kernel_image, ehdr.e_phnum as usize)
-                .map_err(|_| Error::ReadProgramHeader)?
-        };
+
+        // TODO: use `Bytes` trait methods when rust-vmm/vm-memory#83 is merged.
+        let phdr_sz = mem::size_of::<elf::Elf64_Phdr>();
+        let phdrs_bytes = &mut vec![0u8; ehdr.e_phnum as usize * phdr_sz][..];
+        phdrs_bytes
+            .as_volatile_slice()
+            .read_from(0, kernel_image, phdrs_bytes.len())
+            .map_err(|_| Error::ReadProgramHeader)?;
+        let mut phdrs: Vec<&elf::Elf64_Phdr> = vec![];
+        for i in 0usize..ehdr.e_phnum as usize {
+            phdrs.push(
+                elf::Elf64_Phdr::from_slice(&phdrs_bytes[i * phdr_sz..(i + 1) * phdr_sz])
+                    .ok_or(Error::ReadElfHeader)?,
+            );
+        }
 
         // Read in each section pointed to by the program headers.
-        for phdr in &phdrs {
+        for phdr in phdrs {
             if phdr.p_type != elf::PT_LOAD || phdr.p_filesz == 0 {
                 continue;
             }
@@ -314,15 +335,18 @@ impl KernelLoader for BzImage {
         let mut kernel_size = kernel_image
             .seek(SeekFrom::End(0))
             .map_err(|_| Error::SeekBzImageEnd)? as usize;
-        let mut boot_header: bootparam::setup_header = Default::default();
         kernel_image
             .seek(SeekFrom::Start(0x1F1))
             .map_err(|_| Error::SeekBzImageHeader)?;
-        unsafe {
-            // read_struct is safe when reading a POD struct.  It can be used and dropped without issue.
-            struct_util::read_struct(kernel_image, &mut boot_header)
-                .map_err(|_| Error::ReadBzImageHeader)?;
-        }
+
+        // TODO: use `Bytes` trait methods when rust-vmm/vm-memory#83 is merged.
+        let boothdr_bytes = &mut [0u8; mem::size_of::<bootparam::setup_header>()][..];
+        boothdr_bytes
+            .as_volatile_slice()
+            .read_from(0, kernel_image, boothdr_bytes.len())
+            .map_err(|_| Error::ReadBzImageHeader)?;
+        let boot_header = bootparam::setup_header::from_mut_slice(boothdr_bytes)
+            .ok_or(Error::ReadBzImageHeader)?;
 
         // if the HdrS magic number is not found at offset 0x202, the boot protocol version is "old",
         // the image type is assumed as zImage, not bzImage.
@@ -358,7 +382,7 @@ impl KernelLoader for BzImage {
         boot_header.code32_start = mem_offset.raw_value() as u32;
 
         let mut loader_result: KernelLoaderResult = Default::default();
-        loader_result.setup_header = Some(boot_header);
+        loader_result.setup_header = Some(*boot_header);
         loader_result.kernel_load = mem_offset;
 
         //seek the compressed vmlinux.bin and read to memory