diff --git a/apps/system/components/kata-os-common/Cargo.toml b/apps/system/components/kata-os-common/Cargo.toml
index 7911ea3..4dfee65 100644
--- a/apps/system/components/kata-os-common/Cargo.toml
+++ b/apps/system/components/kata-os-common/Cargo.toml
@@ -6,4 +6,5 @@ edition = "2018"
 [dependencies]
 capdl = { path = "src/capdl" }
 kata-os-model = { path = "src/kata-os-model" }
+kata-slot-allocator = { path = "src/kata-slot-allocator" }
 sel4-sys = { path = "src/sel4-sys" }
diff --git a/apps/system/components/kata-os-common/src/kata-slot-allocator/Cargo.toml b/apps/system/components/kata-os-common/src/kata-slot-allocator/Cargo.toml
new file mode 100644
index 0000000..df7bcd7
--- /dev/null
+++ b/apps/system/components/kata-os-common/src/kata-slot-allocator/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "kata-slot-allocator"
+version = "0.1.0"
+authors = ["Sam Leffler <sleffler@google.com>"]
+edition = "2018"
+
+[dependencies]
+# TODO(sleffler): v1.0 requires rust edition2021
+bitvec = { version = "0.22", default-features = false, features = ["alloc"] }
+spin = "0.9"
diff --git a/apps/system/components/kata-os-common/src/kata-slot-allocator/src/lib.rs b/apps/system/components/kata-os-common/src/kata-slot-allocator/src/lib.rs
new file mode 100644
index 0000000..68bdf21
--- /dev/null
+++ b/apps/system/components/kata-os-common/src/kata-slot-allocator/src/lib.rs
@@ -0,0 +1,423 @@
+//! An allocator for an array of integer-numbered objects. This is
+//! typically used to track capability slots in a CNode, though it
+//! can be used for other purposes.
+
+#![cfg_attr(not(test), no_std)]
+
+use bitvec::prelude::*;
+use core::ops::Range;
+use spin::Mutex;
+
+struct Slots {
+    bits: Option<BitBox<Lsb0, u8>>,
+    used: usize,
+    // TODO(sleffler): maybe track last alloc for O(1) sequential allocations
+}
+impl Slots {
+    fn new(size: usize) -> Self {
+        Slots {
+            bits: Some(bitvec![Lsb0, u8; 0; size].into_boxed_bitslice()),
+            used: 0,
+        }
+    }
+    const fn empty() -> Self {
+        Slots {
+            bits: None,
+            used: 0,
+        }
+    }
+    fn init(&mut self, size: usize) {
+        self.bits = Some(bitvec![Lsb0, u8; 0; size].into_boxed_bitslice());
+    }
+    fn used_slots(&self) -> usize { self.used }
+    fn free_slots(&self) -> usize {
+        let bits = self.bits.as_ref().unwrap();
+        bits.len() - self.used
+    }
+
+    fn not_any_in_range(&self, range: Range<usize>) -> bool {
+        let bslice = self.bits.as_ref().unwrap().as_bitslice();
+        // NB: check there is a valid slice
+        if range.start < bslice.len() && range.end <= bslice.len() {
+            bslice[range].not_any()
+        } else {
+            false
+        }
+    }
+    fn set_range(&mut self, range: Range<usize>, value: bool) {
+        let bits = self.bits.as_mut().unwrap();
+        let count = range.len();
+        let bslice = &mut bits.as_mut_bitslice()[range];
+        if value {
+            assert!(bslice.not_any());
+            bslice.set_all(true);
+            self.used = self.used + count;
+        } else {
+            assert!(bslice.all());
+            bslice.set_all(false);
+            self.used = self.used - count;
+        }
+    }
+    fn alloc_first_fit(&mut self, count: usize) -> Option<usize> {
+        if count == 0 { return None; }
+        if count > self.free_slots() { return None; }
+        if count == 1  {
+            let bits = self.bits.as_mut().unwrap();
+            let bit = bits.first_zero()?;
+            unsafe { bits.set_unchecked(bit, true) };
+            self.used = self.used + 1;
+            Some(bit)
+        } else {
+            let first_slot = self.bits.as_ref().unwrap().iter_zeros()
+                .find(|bit| self.not_any_in_range(bit + 1..bit + count))?;
+            self.set_range(first_slot..first_slot + count, true);
+            Some(first_slot)
+        }
+    }
+
+    fn free(&mut self, first_slot: usize, count: usize) {
+        assert!(count <= self.used);
+        self.set_range(first_slot..first_slot + count, false);
+    }
+}
+
+pub struct KataSlotAllocator {
+    slots: Mutex<Slots>,
+    base_slot: usize,
+}
+
+#[cfg(not(test))]
+pub static mut KATA_CSPACE_SLOTS: KataSlotAllocator = KataSlotAllocator::empty();
+
+impl KataSlotAllocator {
+    /// Initializes the Slot state
+    pub fn new(first_slot: usize, size: usize) -> Self {
+        KataSlotAllocator {
+            slots: Mutex::new(Slots::new(size)),
+            base_slot: first_slot,
+        }
+    }
+
+    /// Create a new UNINITIALIZED slot allocator. You must initialize this
+    /// using the init method before using the allocator.
+    pub const fn empty() -> Self {
+        KataSlotAllocator {
+            slots: Mutex::new(Slots::empty()),
+            base_slot: 0,
+        }
+    }
+
+    /// Initializes the Slot state
+    pub unsafe fn init(&mut self, first_slot: usize, size: usize) {
+        self.base_slot = first_slot;
+        (*self.slots.lock()).init(size);
+    }
+
+    /// Returns the base slot number.
+    pub fn base_slot(&self) -> usize { self.base_slot }
+
+    /// Returns the number of slots in use.
+    pub fn used_slots(&self) -> usize {
+        (*self.slots.lock()).used_slots()
+    }
+
+    /// Returns the number of slots available.
+    pub fn free_slots(&self) -> usize {
+        (*self.slots.lock()).free_slots()
+    }
+
+    pub fn alloc(&self, count: usize) -> Option<usize> {
+        (*self.slots.lock()).alloc_first_fit(count).map(|x| x + self.base_slot)
+    }
+
+    pub fn free(&self, first_slot: usize, count: usize) {
+        assert!(first_slot >= self.base_slot);
+        (*self.slots.lock()).free(first_slot - self.base_slot, count)
+    }
+}
+
+#[cfg(test)]
+mod slot_tests {
+    use super::*;
+
+    const NSLOTS: usize = 64;
+
+    #[test]
+    fn test_slots_new() {
+        let slots = Slots::new(NSLOTS);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+    }
+
+    #[test]
+    fn test_slots_init() {
+        static mut SLOTS: Slots = Slots::empty();
+        unsafe {
+            SLOTS.init(NSLOTS);
+            assert_eq!(SLOTS.used_slots(), 0);
+            assert_eq!(SLOTS.free_slots(), NSLOTS);
+        }
+    }
+
+    #[test]
+    fn test_slots_one() {
+        let mut slots = Slots::new(64);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+        let first = slots.alloc_first_fit(1).unwrap();
+        assert_eq!(slots.used_slots(), 1);
+        assert_eq!(slots.free_slots(), NSLOTS - 1);
+        slots.free(first, 1);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+    }
+
+    #[test]
+    fn test_slots_one_multi() {
+        let mut slots = Slots::new(64);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+        let first = slots.alloc_first_fit(1).unwrap();
+        let second = slots.alloc_first_fit(1).unwrap();
+        assert_eq!(slots.used_slots(), 2);
+        assert_eq!(slots.free_slots(), NSLOTS - 2);
+        slots.free(first, 1);
+        assert_eq!(slots.used_slots(), 1);
+        assert_eq!(slots.free_slots(), NSLOTS - 1);
+        slots.free(second, 1);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS );
+
+        let again = slots.alloc_first_fit(1).unwrap();
+        // first-fit so should get same thing
+        assert_eq!(first, again);
+    }
+
+    #[test]
+    fn test_slots_range() {
+        let mut slots = Slots::new(64);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+        let first = slots.alloc_first_fit(3).unwrap();
+        assert_eq!(slots.used_slots(), 3);
+        assert_eq!(slots.free_slots(), NSLOTS - 3);
+        slots.free(first, 3);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+
+        let again = slots.alloc_first_fit(3).unwrap();
+        assert_eq!(first, again);
+    }
+
+    #[test]
+    fn test_slots_range_multi() {
+        let mut slots = Slots::new(64);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+        let first = slots.alloc_first_fit(4).unwrap();
+        let second = slots.alloc_first_fit(4).unwrap();
+        assert_eq!(slots.used_slots(), 4 + 4);
+        assert_eq!(slots.free_slots(), NSLOTS - (4 + 4));
+        slots.free(first, 4);
+        assert_eq!(slots.used_slots(), 4);
+        assert_eq!(slots.free_slots(), NSLOTS - 4);
+        slots.free(second, 4);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+
+        let again = slots.alloc_first_fit(4).unwrap();
+        assert_eq!(first, again);
+    }
+
+    #[test]
+    fn test_slots_range_split_free() {
+        let mut slots = Slots::new(64);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+        let first = slots.alloc_first_fit(4).unwrap();
+        assert_eq!(slots.used_slots(), 4);
+        assert_eq!(slots.free_slots(), NSLOTS - 4);
+        slots.free(first, 2);
+        assert_eq!(slots.used_slots(), 2);
+        assert_eq!(slots.free_slots(), NSLOTS - 2);
+        slots.free(first + 2, 2);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+    }
+
+    #[test]
+    fn test_slots_range_split_free_multi() {
+        let mut slots = Slots::new(64);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+
+        // Request 4 slots
+        let first = slots.alloc_first_fit(4).unwrap();
+        assert_eq!(slots.used_slots(), 4);
+        assert_eq!(slots.free_slots(), NSLOTS - 4);
+        // Free the first 2 slots to create a hole
+        slots.free(first, 2);
+        assert_eq!(slots.used_slots(), 2);
+        assert_eq!(slots.free_slots(), NSLOTS - 2);
+
+        // Requet another 4 slots
+        let second = slots.alloc_first_fit(4).unwrap();
+        // The hole is 2-large so our request should go after
+        assert_eq!(first + 4, second);
+        slots.free(first + 2, 2);
+        assert_eq!(slots.used_slots(), 4);
+        assert_eq!(slots.free_slots(), NSLOTS - 4);
+    }
+
+    #[test]
+    fn test_slots_empty() {
+        let mut slots = Slots::new(0);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), 0);
+        assert!(slots.alloc_first_fit(1).is_none());
+        assert!(slots.alloc_first_fit(8).is_none());
+
+    }
+
+    #[test]
+    fn test_slots_too_small() {
+        let mut slots = Slots::new(NSLOTS);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+        assert!(slots.alloc_first_fit(NSLOTS + 1).is_none());
+    }
+
+    #[test]
+    fn test_slots_oospace() {
+        let mut slots = Slots::new(4);
+        // Allocate 3 of 4 slots
+        let first = slots.alloc_first_fit(3).unwrap();
+        assert_eq!(slots.free_slots(), 1);
+        // Request 2 slots, not enough space
+        assert!(slots.alloc_first_fit(2).is_none());
+
+        // Free up [0,1] so free is [0, 1, 3]
+        slots.free(first, 2);
+        // Request 3 which does not fit.
+        assert!(slots.alloc_first_fit(3).is_none());
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_slots_free_single_invalid() {
+        let mut slots = Slots::new(NSLOTS);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+        // Free an already free slot
+        slots.free(0, 1);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_slots_free_hole_invalid() {
+        let mut slots = Slots::new(NSLOTS);
+        assert_eq!(slots.used_slots(), 0);
+        assert_eq!(slots.free_slots(), NSLOTS);
+        // Allocate the first 4 slots
+        let first = slots.alloc_first_fit(4).unwrap();
+        // Free slot 2, should work.
+        slots.free(first + 2, 1);
+        // Try to free a range that includes a previously free'd slot
+        slots.free(first, 4);
+    }
+}
+
+#[cfg(test)]
+mod kata_slot_tests {
+    use super::*;
+
+    // NB: all these tests will run concurrently to exercise locking
+
+    const SLOT_RANGE: Range<usize> = Range { start: 10, end: 10 + 64 };
+    static mut SLOTS: KataSlotAllocator = KataSlotAllocator::empty();
+    fn setup() {
+        use std::sync::Once;
+        static INIT: Once = Once::new();
+        INIT.call_once(|| { unsafe { SLOTS.init(SLOT_RANGE.start, SLOT_RANGE.len()) }; })
+    }
+
+    #[test]
+    fn test_slots_one() {
+        setup();
+        unsafe {
+            let first = SLOTS.alloc(1).unwrap();
+            assert!(SLOT_RANGE.contains(&first));
+            SLOTS.free(first, 1);
+        }
+    }
+
+    #[test]
+    fn test_slots_one_multi() {
+        setup();
+        unsafe {
+            let first = SLOTS.alloc(1).unwrap();
+            assert!(SLOT_RANGE.contains(&first));
+            let second = SLOTS.alloc(1).unwrap();
+            assert!(SLOT_RANGE.contains(&second));
+            SLOTS.free(first, 1);
+            SLOTS.free(second, 1);
+        }
+    }
+
+    #[test]
+    fn test_slots_range() {
+        setup();
+        unsafe {
+            let first = SLOTS.alloc(3).unwrap();
+            assert!(SLOT_RANGE.contains(&first));
+            assert!(SLOT_RANGE.contains(&(first + 1)));
+            assert!(SLOT_RANGE.contains(&(first + 2)));
+            SLOTS.free(first, 3);
+        }
+    }
+
+    #[test]
+    fn test_slots_range_multi() {
+        setup();
+        unsafe {
+            let first = SLOTS.alloc(4).unwrap();
+            let second = SLOTS.alloc(4).unwrap();
+            SLOTS.free(first, 4);
+            SLOTS.free(second, 4);
+        }
+    }
+
+    #[test]
+    fn test_slots_range_split_free() {
+        setup();
+        unsafe {
+            let first = SLOTS.alloc(4).unwrap();
+            SLOTS.free(first, 2);
+            SLOTS.free(first + 2, 2);
+        }
+    }
+
+    #[test]
+    fn test_slots_range_split_free_multi() {
+        setup();
+        unsafe {
+            // Request 4 slots
+            let first = SLOTS.alloc(4).unwrap();
+            // Free the first 2 slots to create a hole
+            SLOTS.free(first, 2);
+
+            // Requet another 4 slots
+            let _second = SLOTS.alloc(4).unwrap();
+            // The hole is 2-large so our request should go after
+            SLOTS.free(first + 2, 2);
+        }
+    }
+
+    #[test]
+    fn test_slots_oospace() {
+        setup();
+        unsafe {
+            assert!(SLOTS.alloc(SLOT_RANGE.len() + 1).is_none());
+        }
+    }
+}
diff --git a/apps/system/components/kata-os-common/src/lib.rs b/apps/system/components/kata-os-common/src/lib.rs
index 9eb3126..cb6ccd0 100644
--- a/apps/system/components/kata-os-common/src/lib.rs
+++ b/apps/system/components/kata-os-common/src/lib.rs
@@ -2,4 +2,5 @@
 
 pub extern crate capdl;
 pub extern crate kata_os_model;
+pub extern crate kata_slot_allocator;
 pub extern crate sel4_sys;