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25
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1 #include "kernel.h"
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2
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3 // global variables:
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4 uint64_t next_pid = 1;
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5 task_t* ready_queue = 0; // Head of the queue of tasks.
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6 task_t* current_task = 0; // Pointer to the currently running task.
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7
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8 void initialize_tasking()
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9 {
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10 next_pid = 1;
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11 }
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12
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13 /*
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14 Create a new task with some loaded program.
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15 */
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16 void new_task()
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17 {
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18 task_t* newtask = (task_t*)kmalloc(sizeof(task_t));
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19 newtask->pid = next_pid++;
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20 newtask->rip = 0;
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21 newtask->next = 0;
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22
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23 // Append the new task to the ready queue:
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24 task_t* task = ready_queue;
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25 while (task->next != 0)
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26 {
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27 task = task->next;
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28 }
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29 task->next = newtask;
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30 }
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31
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32 /* Fork function duplicates the process */
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33 void task_fork()
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34 {
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35 asm volatile("cli"); // Disable interrupts
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36 task_t *parent_task = current_task;
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37
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38 // Create new task:
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39 task_t *new_task = (task_t*)kmalloc(sizeof(task_t));
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40 new_task->pid = next_pid++;
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41 new_task->rsp = 0;
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42 new_task->rbp = 0;
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43 new_task->rip = 0;
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44 new_task->next = 0;
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45
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46 // Append to the queue:
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47 task_t* tmp_task = ready_queue;
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48 while (tmp_task->next != 0)
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49 {
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50 tmp_task = tmp_task->next;
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51 }
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52 tmp_task->next = new_task;
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53
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54 uint64_t rip = read_rip();
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55
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56 if (current_task == parent_task)
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57 {
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58 uint64_t rbp, rsp;
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59 asm volatile("mov %%rsp, %0" : "=r"(rsp));
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60 asm volatile("mov %%rbp, %0" : "=r"(rbp));
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61 new_task->rip = rip;
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62
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63 asm volatile("sti");
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64 }
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65 }
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66
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67 /*
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68 Scheduler function that switches tasks for multi tasking.
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69 */
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70 void task_scheduler()
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71 {
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72 if (current_task == 0)
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73 {
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74 return;
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75 }
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76
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77 uint64_t rbp, rsp, rip;
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78
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79 rip = 0;
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80 rsp = 0;
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81 rbp = 0;
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82
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83 current_task->rip = rip; // TODO
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84 current_task->rsp = rsp;
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85 current_task->rbp = rbp;
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86
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87 // Select next task:
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88 current_task = current_task->next;
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89 if (current_task == 0)
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90 {
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91 current_task = ready_queue;
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92 }
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93
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94 // Set the rbp, rsp and rip registers:
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95 rsp = current_task->rsp;
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96 rbp = current_task->rbp;
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97 }
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98
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