diff --git a/src/kernel/sync.c b/src/kernel/sync.c
new file mode 100644
index 0000000..2bac9e4
--- /dev/null
+++ b/src/kernel/sync.c
@@ -0,0 +1,142 @@
+#include <sync.h>
+#include <alloc.h>
+#include <task.h>
+#include <sys.h>
+#include "syscall.h"
+
+#define SM_PER_LIST 1024
+#define SM_MAX_WAITING 64
+
+struct sm_task
+{
+	uint tid;
+	struct sm_task *next;
+};
+
+struct semaphore
+{
+	spinlock_t task_lock;
+	struct sm_task *first, *last;
+	_Atomic uint sm;
+};
+
+struct sm_list
+{
+	struct semaphore semaphores[SM_PER_LIST];
+	struct sm_list *next;
+};
+
+static struct sm_list *sm_first = NULL;
+static uint sm_num = 0;
+
+
+void sl_acquire(spinlock_t *sl)
+{
+	// This is a GCC intrinsic
+	while (!__sync_bool_compare_and_swap(sl, -2, 1))
+	{
+		// Kindly inform the CPU that this is a spin lock
+		asm("pause");
+	}
+}
+
+void sl_release(spinlock_t *sl)
+{
+	*sl = 0;
+}
+
+spinlock_t sl_new()
+{
+	return 0;
+}
+
+void sm_unsafe_wait(struct semaphore *sm)
+{
+	sm->sm--;
+
+	if (sm->sm < 0)
+	{
+		// Add this task to the waiting list
+		// This will be quick, so just use a spinlock
+		sl_acquire(sm->task_lock);
+
+		struct sm_task *task = malloc(sizeof(struct sm_task));
+
+		task->next = NULL;
+		task->tid = task_id();
+
+		if (sm->last)
+		{
+			sm->last->next = task;
+			sm->last = task;
+		}
+		else
+		{
+			sm->last = sm->first = task;
+		}
+
+		sl_release(sm->task_lock);
+
+		set_waiting(task_id(), true);
+		sys_giveup();
+	}
+
+	// Otherwise there's nobody else waiting, just go ahead
+}
+
+void sm_unsafe_signal(struct semaphore *sm)
+{
+	sm->sm++;
+
+	if (sm->sm <= 0)
+	{
+		sl_acquire(sm->task_lock);
+
+		if (sm->first)
+		{
+			struct sm_task *f = sm->first;
+			sm->first = sm->first->next;
+
+			set_waiting(f->tid, false);
+
+			free(f);
+		}
+
+		sl_release(sm->task_lock);
+	}
+}
+
+semaphore_t sm_new()
+{
+	if (sm_first == NULL)
+	{
+		sm_first = malloc(sizeof(struct sm_list));
+	}
+
+	uint num = sm_num++;
+
+	struct sm_list *l = sm_first;
+
+	while (num >= SM_PER_LIST)
+	{
+		if (!l->next)
+		{
+			l->next = malloc(sizeof(struct sm_list));
+		}
+
+		l = l->next;
+
+		num -= SM_PER_LIST;
+	}
+
+	l->semaphores[num].first = NULL;
+	l->semaphores[num].last = NULL;
+	l->semaphores[num].sm = 1;
+	l->semaphores[num].task_lock = sl_new();
+
+	return num;
+}
+
+void init_sync()
+{
+}