From 00660fb9143daf7fa04647bccd6047b9bf0f5e48 Mon Sep 17 00:00:00 2001
From: Christian Cunningham <cc@localhost>
Date: Fri, 21 Jan 2022 11:37:49 -0700
Subject: Scheduler Rewrite Start

---
 src/sys/schedule.S | 155 +++++++----------------------------------------------
 1 file changed, 19 insertions(+), 136 deletions(-)

(limited to 'src/sys/schedule.S')

diff --git a/src/sys/schedule.S b/src/sys/schedule.S
index a46654c..298646a 100644
--- a/src/sys/schedule.S
+++ b/src/sys/schedule.S
@@ -1,143 +1,26 @@
 .section ".text"
 .globl schedule
-// TODO: Implement Scheduler for IRQ
 
-
-// Save Context
-// reg = struct cpu_context*
-.macro save_context reg
-	str r4,  [\reg, #0x00]
-	str r5,  [\reg, #0x04]
-	str r6,  [\reg, #0x08]
-	str r7,  [\reg, #0x0c]
-	str r8,  [\reg, #0x10]
-	str r9,  [\reg, #0x14]
-	str r10, [\reg, #0x18]
-	str r11, [\reg, #0x1c]
-	str r12, [\reg, #0x20]
-	str lr,  [\reg, #0x24]
+// Implicit: SVC Mode
+.macro preserve_ctx
+	cps #0x1f // Sys mode
+	push {r0-r12, lr} // Restore usr regs
+	cps #0x10 // Svc mode
+	ldr r3, =scheduler // struct Scheduler
+	ldr r3, [r3, #4] // struct Thread* rthread
+	str lr, [r3, #0] // svc_lr -> void* pc
 .endm
-// Restore Context
-// reg = struct cpu_context*
-.macro restore_context reg
-	ldr r4, [\reg, #0x00]
-	ldr r5, [\reg, #0x04]
-	ldr r6, [\reg, #0x08]
-	ldr r7, [\reg, #0x0c]
-	ldr r8, [\reg, #0x10]
-	ldr r9, [\reg, #0x14]
-	ldr r10, [\reg, #0x18]
-	ldr r11, [\reg, #0x1c]
-	ldr r12, [\reg, #0x20]
-	ldr lr , [\reg, #0x24]
+
+.macro restore_ctx
+	ldr r3, =scheduler // struct Scheduler
+	ldr r3, [r3, #4] // struct Thread* rthread
+	ldr lr, [r3, #0] // void* pc -> lr_svc
+	cps #0x1f // Sys mode
+	pop {r0-r12,lr} // Restore usr regs
+	cps #0x10 // Svc mode
 .endm
 
-// Implemented the scheduler in Assembly since the C defined was messing around with the program stacks
-//  This way, I can be confident that the stacks will be unchanged
 schedule:
-	ldr r3, =scheduler
-	// Preserve context
-	ldr r0, [r3, #4]
-	// r0 = struct cpu_context*
-	save_context r0
-	// Get the next available thread
-	push {r1-r3, lr}
-	bl get_next_thread
-	pop {r1-r3, lr}
-	ldr r1,  [r3, #0] 
-	// r3 = struct Scheduler*
-	// r0 = struct LL* next_thread_ll
-	// r1 = struct LL* current_thread_ll
-	// Check if there is a valid currently running thread
-	cmp r1, #0
-	beq schedule.current_thread_nexists
-schedule.current_thread_exists:
-	cmp r0, r1
-	beq schedule.run_current
-	cmp r0, #0
-	moveq r0, r1 // Make the current running thread the next running thread if no next running thread
-	// Next is not the same as the current
-	// Preserve stack of current
-	ldr r2,  [r1, #0x8] // struct Thread* current
-	ldrh r1, [r2, #0x0e]
-	cmp r1, #2 // THREAD_WAITING
-	beq schedule.temp_status
-	cmp r1, #1 // THREAD_RUNNING
-	bne schedule.dont_modify_status
-schedule.temp_status:
-	mov r1, #0 // THREAD_READY
-	strh r1, [r2, #0x0e]
-schedule.dont_modify_status:
-	str sp,  [r2, #0x4] // void* stack // Preserve stack
-	// Preserve program counter of current
-	str lr,  [r2, #0x0] // void* thread // Preserve pc
-	ldr r2,  [r0, #0x8] // struct Thread* next
-	// Set new stack pointer
-	ldr sp,  [r2, #0x4]
-	// Set the thread as running
-	mov r1, #1 // THREAD_RUNNING
-	strh r1,  [r2, #0x0e] // unsigned short status
-	add r2,  r2, #0x18
-	// Set new running thread
-	str r0,  [r3, #0x0] // struct LL* next_thread_ll // Set new running thread
-	// Set new context
-	str r2,  [r3, #0x4] // struct cpu_context* ctx // Set new context
-	b schedule.run_current
-schedule.current_thread_nexists:
-	// r0 = struct LL* next_thread_ll
-	// r1 = 0 = struct LL* current_thread_ll
-	cmp r0, #0
-	beq schedule.no_next_thread
-	ldr r1, [r0, #0x8]
-	// r1 =  struct Thread* next_thread
-	// Store system stack pointer
-	ldr r2, =svcsp
-	push {r1}
-	ldr r1, [r2]
-	cmp r1, #0
-	pop {r1}
-	bne schedule.dont_overwrite_sys_stack
-	// Store if zero system stack
-	str sp, [r2]
-schedule.dont_overwrite_sys_stack:
-	// Move stack to next thread's stack pointer
-	ldr sp, [r1, #0x4] // void* stack
-	// Store the running thread ll entry
-	str r0, [r3, #0x0] // struct LL* rthread_ll
-	ldr r2, [r0, #0x8] // struct Thread* thread
-	mov r0, #1 // THREAD_RUNNING
-	strh r0, [r2, #0x0e]
-	// Set context
-	add r1, r1, #0x18 // struct cpu_context*
-	str r1, [r3, #0x4] // store to scheduler.ctx
-schedule.run_current:
-	// Restore context
-	ldr r2,  [r3, #0x4] // struct cpu_context* ctx // Set new context
-	restore_context r2
-	// Run
-	ldr r1, [r3, #0]
-	// r1 = struct LL* rthread_ll
-	ldr r1, [r1, #0x8]
-	// r1 = struct Thread* rthread
-	ldr r0, [r1, #0x0]
-	// r0 = void* thread
-	bx r0
-schedule.no_next_thread:
-	// r0 = 0 = struct LL* next_thread_ll
-	// r1 = 0 = struct LL* current_thread_ll
-	// No thread to run
-	// Restore sys context
-	ldr r0, =svccpu
-	str r0, [r3, #0x4] // Store context
-	ldr r0, =svcsp
-	ldr r1, [r0]
-	cmp r1, #0
-	beq schedule.exit
-	mov sp, r1 // Restore stack pointer
-	mov r1, #0
-	str r1, [r0] // Clear stack pointer
-schedule.exit:
-	// Restore register context
-	ldr r2,  [r3, #0x4] // struct cpu_context* ctx // Set new context
-	restore_context r2
-	bx lr
+	//preserve_ctx
+	//restore_ctx
+	//bx lr
-- 
cgit v1.2.1