[MULTITASKING] Context switching and scheduler

kernel/include/list.h

@@ -0,0 +1,69 @@
+#pragma once
+
+#define LIST(type, name) \
+  struct { \
+    type *prev; \
+    type *next; \
+  } name;
+
+#define LIST_HEAD_INIT(name) \
+  name.prev = name.next = 0;
+
+#define LIST_INIT(self, list) \
+    self->list.prev = self->list.next = 0;
+
+#define LIST_APPEND(head, self, list) \
+  do { \
+    self->list.prev = head.prev; \
+    self->list.next = 0; \
+    if(self->list.prev) { \
+      self->list.prev->list.next = self; \
+    } \
+    head.prev = self; \
+    if(!head.next){head.next = head.prev;} \
+  } while(0);
+
+#define LIST_REMOVE(head, self, list) \
+  do { \
+    if(head.next == self) { \
+      head.next = self->list.next; \
+    } \
+    if(head.prev == self) { \
+      head.prev = self->list.prev; \
+    } \
+    if(self->list.next) { \
+      self->list.next->list.prev = self->list.prev; \
+    } \
+    if(self->list.prev) { \
+      self->list.prev->list.next = self->list.next; \
+    } \
+    self->list.prev = self->list.next = 0; \
+  } while(0);
+
+#define LIST_EMPTY(head) ((head.next) == 0)
+#define LIST_FIRST(head) (head.next)
+
+#define LIST_FOREACH(head, type, name, list) \
+  for(type *name = head.next; name; name = name->list.next)
+
+#define LIST_INSERT_BEFORE(head, self, list, after) \
+  do { \
+    self->list.next = after; \
+    self->list.next = after->list.prev; \
+    after->list.prev = self; \
+    if(self->list.prev) \
+      self->list.prev->list.next = self; \
+    if(head.next == after) \
+      head.next = self; \
+  } while(0);
+
+#define LIST_INSERT_AFTER(head, self, list, before) \
+  do { \
+    self->list.prev = before; \
+    self->list.next = before->list.next; \
+    before->list.next = self; \
+    if(self->list.next) \
+      self->list.next->list.prev = self; \
+    if(head->prev == before) \
+      head.prev = self; \
+  } while(0);

kernel/include/scheduler.h

@@ -0,0 +1,6 @@
+#pragma once
+#include <thread.h>
+
+void schedule();
+void scheduler_insert(thread_t *th);
+void scheduler_init();

kernel/include/thread.h

@@ -0,0 +1,43 @@
+#pragma once
+#include <stdint.h>
+#include <list.h>
+
+#define THREAD_STACK_SIZE 0x1000-sizeof(thread_t)
+
+typedef struct thread_st
+{
+  uint64_t stack_pointer; // Top of the kernel stack for thread
+  uint64_t tid;
+  uint64_t state;
+  LIST(struct thread_st, ready_queue);
+} thread_t;
+
+#define THREAD_STATE_WAITING  0x1
+#define THREAD_STATE_READY    0x2
+#define THREAD_STATE_RUNNING  0x3
+#define THREAD_STATE_FINISHED 0x4
+
+typedef struct thread_stack_st
+{
+  uint8_t stack[THREAD_STACK_SIZE-8*8];
+  // Stack layout of a new thread
+  uint64_t RBP;
+  uint64_t RBX;
+  uint64_t R12;
+  uint64_t R13;
+  uint64_t R14;
+  uint64_t R15;
+  uint64_t zero_frame;
+  uint64_t function_address;
+  thread_t tcb;
+} thread_stack_t;
+
+thread_t *current_thread;
+#define get_current_thread() (current_thread)
+#define set_current_thread(new) (current_thread = (new))
+
+thread_t *new_thread(void (*func)(void));
+void switch_thread(thread_t *old, thread_t *new);
+void free_thread(thread_t *th);
+
+void swtch(uint64_t *old, uint64_t *new);