From d1b5720abd83dbb1f0e771400db0078036cabd01 Mon Sep 17 00:00:00 2001
From: Drew Galbraith <dgalbraith33@gmail.com>
Date: Sat, 25 Jan 2025 23:17:45 -0800
Subject: [PATCH] Add a Mutex implementation.

---
 rust/lib/mammoth/src/sync.rs    | 53 +++++++++++++++++++++++++++++++++
 rust/lib/mammoth/src/syscall.rs | 30 +++++++++++++++++++
 2 files changed, 83 insertions(+)

diff --git a/rust/lib/mammoth/src/sync.rs b/rust/lib/mammoth/src/sync.rs
index 8d80f17..0ee5fea 100644
--- a/rust/lib/mammoth/src/sync.rs
+++ b/rust/lib/mammoth/src/sync.rs
@@ -1,3 +1,7 @@
+use core::cell::UnsafeCell;
+use core::ops::Deref;
+use core::ops::DerefMut;
+
 use crate::{cap::Capability, syscall, zion::ZError};
 
 pub struct Semaphore {
@@ -17,3 +21,52 @@ impl Semaphore {
         syscall::semaphone_signal(&self.cap)
     }
 }
+
+pub struct Mutex<T> {
+    cap: Capability,
+    data: UnsafeCell<T>,
+}
+
+unsafe impl<T> Sync for Mutex<T> where T: Send {}
+
+pub struct MutexGuard<'a, T> {
+    mutex: &'a Mutex<T>,
+}
+
+unsafe impl<T> Send for MutexGuard<'_, T> where T: Send {}
+unsafe impl<T> Sync for MutexGuard<'_, T> where T: Sync {}
+
+impl<T> Deref for MutexGuard<'_, T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        unsafe { &*self.mutex.data.get() }
+    }
+}
+
+impl<T> DerefMut for MutexGuard<'_, T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        unsafe { &mut *self.mutex.data.get() }
+    }
+}
+
+impl<T> Mutex<T> {
+    pub fn new(data: T) -> Mutex<T> {
+        Mutex {
+            cap: syscall::mutex_create().unwrap(),
+            data: UnsafeCell::new(data),
+        }
+    }
+
+    pub fn lock(&self) -> MutexGuard<T> {
+        syscall::mutex_lock(&self.cap).unwrap();
+
+        MutexGuard { mutex: self }
+    }
+}
+
+impl<T> Drop for MutexGuard<'_, T> {
+    fn drop(&mut self) {
+        syscall::mutex_release(&self.mutex.cap).unwrap();
+    }
+}
diff --git a/rust/lib/mammoth/src/syscall.rs b/rust/lib/mammoth/src/syscall.rs
index 565a2c1..31acd94 100644
--- a/rust/lib/mammoth/src/syscall.rs
+++ b/rust/lib/mammoth/src/syscall.rs
@@ -412,6 +412,36 @@ pub fn reply_port_recv(
     Ok((num_bytes, num_caps))
 }
 
+pub fn mutex_create() -> Result<Capability, ZError> {
+    let mut mutex_cap: z_cap_t = 0;
+    syscall(
+        zion::kZionMutexCreate,
+        &zion::ZMutexCreateReq {
+            mutex_cap: &mut mutex_cap,
+        },
+    )?;
+
+    Ok(Capability::take(mutex_cap))
+}
+
+pub fn mutex_lock(mutex_cap: &Capability) -> Result<(), ZError> {
+    syscall(
+        zion::kZionMutexLock,
+        &zion::ZMutexLockReq {
+            mutex_cap: mutex_cap.raw(),
+        },
+    )
+}
+
+pub fn mutex_release(mutex_cap: &Capability) -> Result<(), ZError> {
+    syscall(
+        zion::kZionMutexRelease,
+        &zion::ZMutexReleaseReq {
+            mutex_cap: mutex_cap.raw(),
+        },
+    )
+}
+
 pub fn semaphore_create() -> Result<Capability, ZError> {
     let mut sem_cap: z_cap_t = 0;
     syscall(