minimal KVM abstraction + real mode guest example

1 files changed, 145 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..6793272
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,145 @@
+use std::convert::{AsMut, AsRef};
+use std::io;
+use std::ops;
+use std::os::unix::io::AsRawFd;
+
+pub mod kvm;
+pub mod kvm_sys;
+pub mod vcpu;
+pub mod vm;
+
+/// Strong type representing physical addresses.
+pub struct PhysAddr(pub u64);
+
+/// Helper to turn libc return values into an [io::Result](std::io::Result). Returns
+/// [`Error::last_os_error`](std::io::Error::last_os_error) if `ret < 0`.
+fn libcret(ret: libc::c_int) -> io::Result<libc::c_int> {
+    if ret < 0 {
+        Err(io::Error::last_os_error())
+    } else {
+        Ok(ret)
+    }
+}
+
+/// Wrapper of `libc::ioctl` for KVM ioctls with one argument and returning an
+/// [`io::Result`](std::io::Result).
+fn ioctl<F: AsRawFd>(fd: &F, cmd: u64, arg: u64) -> io::Result<libc::c_int> {
+    libcret(unsafe { libc::ioctl(fd.as_raw_fd(), cmd, arg) })
+}
+
+/// Wrapper to safely allocate memory for guest VMs.
+///
+/// The underlying memory is freed automatically once the `UserMem` instance is dropped.
+///
+/// Memory can be mapped into a guest VM with
+/// [`Vm::set_user_memory_region`](crate::vm::Vm::set_user_memory_region).
+pub struct UserMem {
+    ptr: *mut u8,
+    len: usize,
+}
+
+impl UserMem {
+    /// Allocate a zero-initialized memory region of `len` bytes.
+    pub fn new(len: usize) -> io::Result<UserMem> {
+        let ptr = unsafe {
+            libc::mmap(
+                std::ptr::null_mut(),
+                len,
+                libc::PROT_READ | libc::PROT_WRITE,
+                libc::MAP_PRIVATE | libc::MAP_ANONYMOUS,
+                -1,
+                0,
+            )
+        };
+
+        if ptr == libc::MAP_FAILED {
+            Err(io::Error::last_os_error())
+        } else {
+            Ok(UserMem {
+                ptr: ptr.cast(),
+                len,
+            })
+        }
+    }
+
+    /// Allocate a zero-initialized memory region of `len` bytes and initialize the first bytes
+    /// with `init_len`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `init_from` is larger than the memory size `len`.
+    pub fn with_init(len: usize, init_from: &[u8]) -> io::Result<UserMem> {
+        assert!(len >= init_from.len());
+
+        let mut m = UserMem::new(len)?;
+        m.as_mut()[..init_from.len()].copy_from_slice(init_from);
+        Ok(m)
+    }
+}
+
+impl ops::Drop for UserMem {
+    /// Free underlying memory.
+    fn drop(&mut self) {
+        unsafe { libc::munmap(self.ptr.cast(), self.len) };
+    }
+}
+
+impl AsRef<[u8]> for UserMem {
+    fn as_ref(&self) -> &[u8] {
+        unsafe { std::slice::from_raw_parts(self.ptr, self.len) }
+    }
+}
+
+impl AsMut<[u8]> for UserMem {
+    fn as_mut(&mut self) -> &mut [u8] {
+        unsafe { std::slice::from_raw_parts_mut(self.ptr, self.len) }
+    }
+}
+
+/// Internal wrapper to automatically `mmap` and `munmap` the the [`struct kvm_run`][kvm_run]
+/// for a given VPCU.
+///
+/// [kvm_run]: https://www.kernel.org/doc/html/latest/virt/kvm/api.html#the-kvm-run-structure
+struct KvmRun {
+    ptr: *mut kvm_sys::kvm_run,
+    len: usize,
+}
+
+impl KvmRun {
+    /// Mmap the `struct kvm_run` for a given `VCPU` referenced by the argument file descriptor
+    /// `vcpu`.
+    fn new<F: AsRawFd>(vcpu: &F, len: usize) -> io::Result<KvmRun> {
+        let ptr = unsafe {
+            libc::mmap(
+                std::ptr::null_mut(),
+                len,
+                libc::PROT_READ,
+                libc::MAP_SHARED,
+                vcpu.as_raw_fd(),
+                0,
+            )
+        };
+
+        if ptr == libc::MAP_FAILED {
+            Err(io::Error::last_os_error())
+        } else {
+            Ok(KvmRun {
+                ptr: ptr.cast(),
+                len,
+            })
+        }
+    }
+}
+
+impl ops::Drop for KvmRun {
+    /// Munmap the mmaped `struct kvm_run`.
+    fn drop(&mut self) {
+        unsafe { libc::munmap(self.ptr.cast(), self.len) };
+    }
+}
+
+impl AsRef<kvm_sys::kvm_run> for KvmRun {
+    fn as_ref(&self) -> &kvm_sys::kvm_run {
+        unsafe { &(*self.ptr) }
+    }
+}