arch: load initramfs and populate zero page

* load the initramfs File into the guest memory, aligned to page size
* finally setup the initramfs address and its size into the boot params
  (in configure_64bit_boot)

Signed-off-by: Damjan Georgievski <gdamjan@gmail.com>

arch/src/lib.rs

@@ -41,6 +41,8 @@ pub enum Error {
     StartInfoPastRamEnd,
     /// Error writing hvm_start_info to guest memory.
     StartInfoSetup,
+    /// Failed to compute initramfs address.
+    InitramfsAddress,
 }
 pub type Result<T> = result::Result<T, Error>;
 
@@ -76,8 +78,8 @@ pub mod x86_64;
 
 #[cfg(target_arch = "x86_64")]
 pub use x86_64::{
-    arch_memory_regions, configure_system, layout, layout::CMDLINE_MAX_SIZE, layout::CMDLINE_START,
-    BootProtocol, EntryPoint,
+    arch_memory_regions, configure_system, initramfs_load_addr, layout, layout::CMDLINE_MAX_SIZE,
+    layout::CMDLINE_START, BootProtocol, EntryPoint,
 };
 
 /// Safe wrapper for `sysconf(_SC_PAGESIZE)`.
@@ -86,3 +88,11 @@ fn pagesize() -> usize {
     // Trivially safe
     unsafe { libc::sysconf(libc::_SC_PAGESIZE) as usize }
 }
+
+/// Type for passing information about the initramfs in the guest memory.
+pub struct InitramfsConfig {
+    /// Load address of initramfs in guest memory
+    pub address: vm_memory::GuestAddress,
+    /// Size of initramfs in guest memory
+    pub size: usize,
+}

arch/src/x86_64/mod.rs

@@ -13,12 +13,14 @@ pub mod layout;
 mod mptable;
 pub mod regs;
 
+use crate::InitramfsConfig;
 use crate::RegionType;
 use linux_loader::loader::bootparam::{boot_params, setup_header};
 use linux_loader::loader::start_info::{hvm_memmap_table_entry, hvm_start_info};
 use std::mem;
 use vm_memory::{
-    Address, ByteValued, Bytes, GuestAddress, GuestMemory, GuestMemoryMmap, GuestUsize,
+    Address, ByteValued, Bytes, GuestAddress, GuestMemory, GuestMemoryMmap, GuestMemoryRegion,
+    GuestUsize,
 };
 
 #[derive(Debug, Copy, Clone)]
@@ -151,6 +153,7 @@ pub fn configure_system(
     guest_mem: &GuestMemoryMmap,
     cmdline_addr: GuestAddress,
     cmdline_size: usize,
+    initramfs: &Option<InitramfsConfig>,
     num_cpus: u8,
     setup_hdr: Option<setup_header>,
     rsdp_addr: Option<GuestAddress>,
@@ -164,7 +167,14 @@ pub fn configure_system(
             configure_pvh(guest_mem, cmdline_addr, rsdp_addr)?;
         }
         BootProtocol::LinuxBoot => {
-            configure_64bit_boot(guest_mem, cmdline_addr, cmdline_size, setup_hdr, rsdp_addr)?;
+            configure_64bit_boot(
+                guest_mem,
+                cmdline_addr,
+                cmdline_size,
+                initramfs,
+                setup_hdr,
+                rsdp_addr,
+            )?;
         }
     }
 
@@ -293,6 +303,7 @@ fn configure_64bit_boot(
     guest_mem: &GuestMemoryMmap,
     cmdline_addr: GuestAddress,
     cmdline_size: usize,
+    initramfs: &Option<InitramfsConfig>,
     setup_hdr: Option<setup_header>,
     rsdp_addr: Option<GuestAddress>,
 ) -> super::Result<()> {
@@ -319,6 +330,11 @@ fn configure_64bit_boot(
     params.0.hdr.cmd_line_ptr = cmdline_addr.raw_value() as u32;
     params.0.hdr.cmdline_size = cmdline_size as u32;
 
+    if let Some(initramfs_config) = initramfs {
+        params.0.hdr.ramdisk_image = initramfs_config.address.raw_value() as u32;
+        params.0.hdr.ramdisk_size = initramfs_config.size as u32;
+    }
+
     add_e820_entry(&mut params.0, 0, layout::EBDA_START.raw_value(), E820_RAM)?;
 
     let mem_end = guest_mem.last_addr();
@@ -388,6 +404,25 @@ fn add_e820_entry(
     Ok(())
 }
 
+/// Returns the memory address where the initramfs could be loaded.
+pub fn initramfs_load_addr(
+    guest_mem: &GuestMemoryMmap,
+    initramfs_size: usize,
+) -> super::Result<u64> {
+    let first_region = guest_mem
+        .find_region(GuestAddress::new(0))
+        .ok_or(super::Error::InitramfsAddress)?;
+    // It's safe to cast to usize because the size of a region can't be greater than usize.
+    let lowmem_size = first_region.len() as usize;
+
+    if lowmem_size < initramfs_size {
+        return Err(super::Error::InitramfsAddress);
+    }
+
+    let aligned_addr: u64 = ((lowmem_size - initramfs_size) & !(crate::pagesize() - 1)) as u64;
+    Ok(aligned_addr)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -417,6 +452,7 @@ mod tests {
             &gm,
             GuestAddress(0),
             0,
+            &None,
             1,
             None,
             None,
@@ -437,6 +473,7 @@ mod tests {
             &gm,
             GuestAddress(0),
             0,
+            &None,
             no_vcpus,
             None,
             None,
@@ -448,6 +485,7 @@ mod tests {
             &gm,
             GuestAddress(0),
             0,
+            &None,
             no_vcpus,
             None,
             None,
@@ -468,6 +506,7 @@ mod tests {
             &gm,
             GuestAddress(0),
             0,
+            &None,
             no_vcpus,
             None,
             None,
@@ -479,6 +518,7 @@ mod tests {
             &gm,
             GuestAddress(0),
             0,
+            &None,
             no_vcpus,
             None,
             None,
@@ -499,6 +539,7 @@ mod tests {
             &gm,
             GuestAddress(0),
             0,
+            &None,
             no_vcpus,
             None,
             None,
@@ -510,6 +551,7 @@ mod tests {
             &gm,
             GuestAddress(0),
             0,
+            &None,
             no_vcpus,
             None,
             None,

vmm/src/vm.rs

@@ -38,9 +38,10 @@ use kvm_ioctls::*;
 use linux_loader::cmdline::Cmdline;
 use linux_loader::loader::KernelLoader;
 use signal_hook::{iterator::Signals, SIGINT, SIGTERM, SIGWINCH};
+use std::convert::TryInto;
 use std::ffi::CString;
 use std::fs::File;
-use std::io;
+use std::io::{self, Seek, SeekFrom};
 use std::ops::Deref;
 use std::path::PathBuf;
 use std::sync::{Arc, Mutex, RwLock};
@@ -78,9 +79,15 @@ pub enum Error {
     /// Cannot open the kernel image
     KernelFile(io::Error),
 
+    /// Cannot open the initramfs image
+    InitramfsFile(io::Error),
+
     /// Cannot load the kernel in memory
     KernelLoad(linux_loader::loader::Error),
 
+    /// Cannot load the initramfs in memory
+    InitramfsLoad,
+
     /// Cannot load the command line in memory
     LoadCmdLine(linux_loader::loader::Error),
 
@@ -219,6 +226,7 @@ impl VmState {
 
 pub struct Vm {
     kernel: File,
+    initramfs: Option<File>,
     threads: Vec<thread::JoinHandle<()>>,
     device_manager: Arc<Mutex<DeviceManager>>,
     config: Arc<Mutex<VmConfig>>,
@@ -254,6 +262,11 @@ impl Vm {
         let kernel = File::open(&config.lock().unwrap().kernel.as_ref().unwrap().path)
             .map_err(Error::KernelFile)?;
 
+        let initramfs = match &config.lock().unwrap().initramfs {
+            Some(initramfs) => Some(File::open(&initramfs.path).map_err(Error::InitramfsFile)?),
+            None => None,
+        };
+
         let fd: VmFd;
         loop {
             match kvm.create_vm() {
@@ -377,6 +390,7 @@ impl Vm {
 
         Ok(Vm {
             kernel,
+            initramfs,
             device_manager,
             config,
             on_tty,
@@ -388,6 +402,28 @@ impl Vm {
         })
     }
 
+    fn load_initramfs(&mut self, guest_mem: &GuestMemoryMmap) -> Result<arch::InitramfsConfig> {
+        let mut initramfs = self.initramfs.as_ref().unwrap();
+        let size: usize = initramfs
+            .seek(SeekFrom::End(0))
+            .map_err(|_| Error::InitramfsLoad)?
+            .try_into()
+            .unwrap();
+        initramfs
+            .seek(SeekFrom::Start(0))
+            .map_err(|_| Error::InitramfsLoad)?;
+
+        let address =
+            arch::initramfs_load_addr(guest_mem, size).map_err(|_| Error::InitramfsLoad)?;
+        let address = GuestAddress(address);
+
+        guest_mem
+            .read_from(address, &mut initramfs, size)
+            .map_err(|_| Error::InitramfsLoad)?;
+
+        Ok(arch::InitramfsConfig { address, size })
+    }
+
     fn load_kernel(&mut self) -> Result<EntryPoint> {
         let mut cmdline = Cmdline::new(arch::CMDLINE_MAX_SIZE);
         cmdline
@@ -425,6 +461,12 @@ impl Vm {
             &cmdline_cstring,
         )
         .map_err(Error::LoadCmdLine)?;
+
+        let initramfs_config = match self.initramfs {
+            Some(_) => Some(self.load_initramfs(mem.deref())?),
+            None => None,
+        };
+
         let boot_vcpus = self.cpu_manager.lock().unwrap().boot_vcpus();
         let _max_vcpus = self.cpu_manager.lock().unwrap().max_vcpus();
 
@@ -447,6 +489,7 @@ impl Vm {
                     &mem,
                     arch::layout::CMDLINE_START,
                     cmdline_cstring.to_bytes().len() + 1,
+                    &initramfs_config,
                     boot_vcpus,
                     Some(hdr),
                     rsdp_addr,
@@ -481,6 +524,7 @@ impl Vm {
                     &mem,
                     arch::layout::CMDLINE_START,
                     cmdline_cstring.to_bytes().len() + 1,
+                    &initramfs_config,
                     boot_vcpus,
                     None,
                     rsdp_addr,