kern/amd64: proc: Add initial context switch logic

This commit introduces new functions that will be useful for
having multiple processes run on the system.

- Add md_proc_yield()
- Add md_proc_kick()
- Add md_sched_switch()

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 22 insertions, 0 deletions

diff --git a/src/sys/include/os/sched.h b/src/sys/include/os/sched.h
index b393395..1850366 100644
--- a/src/sys/include/os/sched.h
+++ b/src/sys/include/os/sched.h
@@ -35,6 +35,7 @@
 #include <sys/proc.h>
 #include <os/spinlock.h>
 
+#define SCHED_QUANTUM 10000
 #define SCHED_NQUEUES 4
 
 /*
@@ -50,6 +51,13 @@ struct sched_queue {
 };
 
 /*
+ * Context switch to another process
+ *
+ * @tf: Current CPU context frame
+ */
+void md_sched_switch(struct trapframe *tf);
+
+/*
  * Enqueue a new process to a queue
  *
  * @q: Queue to target
diff --git a/src/sys/include/sys/proc.h b/src/sys/include/sys/proc.h
index d09e459..59d47ec 100644
--- a/src/sys/include/sys/proc.h
+++ b/src/sys/include/sys/proc.h
@@ -31,6 +31,7 @@
 #define _SYS_PROC_H_
 
 #include <sys/types.h>
+#include <sys/cdefs.h>
 #include <sys/queue.h>
 #include <machine/pcb.h>    /* standard */
 
@@ -87,4 +88,17 @@ int md_proc_init(struct proc *procp, int flags);
  */
 int md_set_ip(struct proc *procp, uintptr_t ip);
 
+/*
+ * Put the current process into a halt loop
+ * until the next one runs.
+ */
+__dead void md_proc_yield(void);
+
+/*
+ * Kick a process into a user context
+ *
+ * @procp: Process pointer
+ */
+__dead void md_proc_kick(struct proc *procp);
+
 #endif  /* !_SYS_PROC_H_ */