From a61201b8047ebe278cfb281723a4bf6c82556472 Mon Sep 17 00:00:00 2001
From: Christian Cunningham <cc@localhost>
Date: Thu, 6 Jan 2022 15:51:48 -0800
Subject: Scheduling

---
 include/sys/core.h     |  10 ----
 include/sys/schedule.h | 142 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 142 insertions(+), 10 deletions(-)
 create mode 100644 include/sys/schedule.h

(limited to 'include/sys')

diff --git a/include/sys/core.h b/include/sys/core.h
index 2d611b3..361ffb1 100644
--- a/include/sys/core.h
+++ b/include/sys/core.h
@@ -21,16 +21,6 @@ static inline void delay(unsigned long cycles)
 			: "=r"(cycles): [cycles]"0"(cycles) : "cc");
 }
 
-static inline void preserveregs(void)
-{
-	asm volatile("push {r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11}");
-}
-
-static inline void restoreregs(void)
-{
-	asm volatile("pop {r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11}");
-}
-
 static inline void* getsp(void)
 {
 	void* out;
diff --git a/include/sys/schedule.h b/include/sys/schedule.h
new file mode 100644
index 0000000..cced851
--- /dev/null
+++ b/include/sys/schedule.h
@@ -0,0 +1,142 @@
+#ifndef SYS_SCHEDULE_H
+#define SYS_SCHEDULE_H
+#include <cpu.h>
+#include <lib/mem.h>
+#include <lib/ll.h>
+#include <sys/core.h>
+
+enum ThreadStatus {
+	THREAD_READY,
+	THREAD_WAITING,
+	THREAD_WAITING_FOR_MUTEX,
+	THREAD_STACK_ERROR,
+	THREAD_RUNNING,
+	THREAD_FINISHED,
+};
+
+struct ThreadData {
+	unsigned short status;
+	void* mutex_waiting;
+	unsigned long pid;
+	unsigned char priority;
+};
+
+struct Thread {
+	struct ThreadData data;
+	void (*thread)(void);
+	void* stack;
+	void* stack_base;
+};
+
+#define MAX_THREADS 0x100
+#define STACK_SIZE 0x1000
+#define PRIORITIES 6
+struct Scheduler {
+	struct LL tlist[PRIORITIES];
+	struct LL* rthread_ll;
+};
+
+#ifndef SYS_SCHEDULE_C
+#define SYS_SCHEDULE_C
+extern struct Scheduler scheduler;
+#endif
+
+void init_scheduler(void);
+void add_thread(void (*thread_fxn)(void), unsigned char priority);
+void schedule(void);
+void remove_running_thread(void);
+
+static inline void preserveregs(struct Thread* thread)
+{
+	// Preserve current stack pointer
+	void* sp = getsp();
+	// Get current mode
+	unsigned long mode = getmode();
+	// Set supervisor mode - "User mode"
+	setsvc();
+	void* ssp = getsp();
+	// Move stack to reserved register area
+	setsp(thread->stack_base - 0x1000 + 16*4);
+	// Push registers to the stack
+	asm volatile ("push {r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, lr}");
+	// Restore stack to previous
+	setsp(ssp);
+	// Restore mode
+	setmode(mode);
+	// Restore current stack pointer
+	setsp(sp);
+}
+
+static inline void preservestack(struct Thread* thread)
+{
+	// Get current mode
+	unsigned long mode = getmode();
+	// Set supervisor mode - "User mode"
+	setsvc();
+	// Store the stack pointer
+	void* ssp = getsp();
+	thread->stack = ssp;
+	// Restore mode
+	setmode(mode);
+}
+
+static inline void restoreregs(struct Thread* thread)
+{
+	// Preserve current stack pointer
+	void* sp = getsp();
+	// Get current mode
+	unsigned long mode = getmode();
+	// Set supervisor mode - "User mode"
+	setsvc();
+	void* ssp = getsp();
+	// Move stack to reserved register area
+	setsp(thread->stack_base - 0x1000 + 16*4 - 14*4);
+	// Restore registers on the stack
+	asm volatile ("pop {r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, lr}");
+	// Restore stack to previous
+	setsp(ssp);
+	// Restore mode
+	setmode(mode);
+	// Restore current stack pointer
+	setsp(sp);
+}
+
+static inline void restorestack(struct Thread* thread)
+{
+	// Get current mode
+	unsigned long mode = getmode();
+	// Set supervisor mode - "User mode"
+	setsvc();
+	// Set stack pointer to thread's stack pointer
+	asm volatile("mov sp, %0" :: "r"(thread->stack));
+	// Restore mode
+	setmode(mode);
+}
+
+static inline void preservesysstack(unsigned long* sp)
+{
+	if (*sp == 0) {
+		unsigned long mode = getmode();
+		setsvc();
+		*sp = (unsigned long)getsp();
+		setmode(mode);
+	}
+}
+
+static inline void restoresysstack(unsigned long* sp)
+{
+	if (*sp) {
+		unsigned long mode = getmode();
+		setsvc();
+		setsp((void*)*sp);
+		setmode(mode);
+		*sp = 0;
+	}
+}
+
+static inline void preservepc(struct Thread* t)
+{
+	asm volatile ("mov %0, lr" : "=r"(t->thread));
+}
+
+#endif
-- 
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