Very simple threading and context switching.

src/kernel/proc/thread.c

@@ -0,0 +1,46 @@
+#include <thread.h>
+
+struct thread *threads[8];
+int current_tid = -1;
+int tid = 0;
+
+struct thread dummy;
+
+struct thread *new_thread(void (*function)())
+{
+  struct thread *th = threads[tid] = P2V(pmm_alloc());
+
+  th->tcb.tid = tid++;
+  th->RBP = (uint64_t)&th->RBP2;
+  th->ret = (uint64_t)function;
+  th->tcb.stack_ptr = (uint64_t)&th->RBP;
+
+  return th;
+}
+
+void switch_thread(struct thread *old, struct thread *new)
+{
+  swtch(&old->tcb.stack_ptr, &new->tcb.stack_ptr);
+}
+
+void yield()
+{
+  struct thread *old, *new;
+  if(current_tid == -1)
+    old = &dummy;
+  else
+    old = threads[current_tid];
+
+  current_tid++;
+  if(current_tid == tid)
+    current_tid = 0;
+
+  new = threads[current_tid];
+
+  switch_thread(old, new);
+}
+
+int get_tid()
+{
+  return CURRENT_THREAD()->tcb.tid;
+}