kernel/sched.c

   1 /*
   2  *  ZeX/OS
   3  *  Copyright (C) 2007  Tomas 'ZeXx86' Jedrzejek (zexx86@gmail.com)
   4  *
   5  *  This program is free software: you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation, either version 3 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19
  20 #include <system.h>
  21 #include <x86.h>
  22 #include <string.h>
  23 #include <setjmp.h>
  24
  25 /* jmp_buf (E)IP and (E)SP register names for various environments:
  26                         Tinylib         TurboC  DJGPP   Linux (glibc5) */
  27 #define JMPBUF_IP       eip     /*      j_ip    __eip   __pc    */
  28 #define JMPBUF_SP       esp     /*      j_sp    __esp   __sp    */
  29 #define JMPBUF_FLAGS    eflags  /*      j_flag  __eflags ?      */
  30
  31 task_t task_list;
  32 task_t *_curr_task;
  33 unsigned task_id = NULL;
  34
  35 #define WAIT    0xFFFFFL
  36
  37 static void wait (void)
  38 {
  39         unsigned long wait;
  40
  41         for(wait = WAIT; wait != 0; wait--)
  42                 /* nothing */;
  43 }
  44
  45 int cstrcmp (char *one, char *two)
  46 {
  47         int i;
  48
  49         for(i = 0; (unsigned) i < strlen (one); i ++)
  50         {
  51                 if (one[i] != two[i])
  52                         return -1;
  53         }
  54
  55         if ((two[i] == ' ' || two[i] == '\0') || two[i] == '\n')
  56                 return 0;
  57
  58         return -2;
  59 }
  60
  61
  62 int gets (void)
  63 {
  64         if (key != 0)
  65         {
  66
  67                 int i = 0;
  68                 settextcolor (2,0);
  69
  70                 char c[1];
  71                 c[0] = key;
  72                 tty_write (currtty, c, 1);
  73
  74                 if (key == '\n') // we press enter
  75                 {
  76                         currtty->shell[currtty->shell_len] = '\0';
  77                         currtty->shell_len = 0;
  78                         i = 1;
  79                 }
  80                 else
  81                 {
  82                         /* if you has wroted some text, and backspace is pressed, lets move cursor back */
  83                         if (key == '\b' && currtty->shell_len > 0)
  84                         {
  85                                 currtty->shell_len --;                  // first we have to descrease text length
  86                                 currtty->shell[currtty->shell_len] = '\0';              // we can put \0 character under cursor
  87                                 //putch (' ');
  88                         }
  89                         else /* you type normal text */
  90                         {
  91                                 currtty->shell[currtty->shell_len] = key;
  92                                 currtty->shell_len ++;
  93                         }
  94                 }
  95
  96                 key = 0;
  97                 settextcolor (15, 0);
  98
  99                 return i;
 100         }
 101
 102         return 0;
 103 }
 104
 105 /*****************************************************************************
 106 *****************************************************************************/
 107
 108 void fdd_task (void)
 109 {
 110         while(1)
 111         {
 112                 schedule();
 113                 //puts ("thread1\n");
 114                 wait();
 115         }
 116 }
 117
 118 unsigned task_shell ()
 119 {
 120         int i;
 121
 122         while(1)
 123         {
 124                 schedule ();
 125                 //puts ("thread0\n");
 126                 /*i = gets ();
 127
 128                 if (i == 1) {
 129                         if (curruser)
 130                                 console (i);
 131                         else
 132                                 getlogin (i);
 133                 }*/
 134
 135                 wait ();
 136         }
 137 }
 138
 139 /**     SCHEDULE
 140  *      Function, which handle each task.
 141  *      It jump from task to another task in moment, when schedule () is called.
 142  */
 143
 144 int ticks = 0;
 145 void schedule (void)
 146 {
 147
 148         /* handle console on kernel level */
 149         int i = gets ();
 150
 151         if (i == 1) {
 152                 if (currtty->user)
 153                         console (i);
 154                 else
 155                         getlogin (i);
 156         }
 157
 158         /* handle all other tasks */
 159         ticks ++;               /* increase ticks count */
 160         if (ticks > 100)        /* tasks has priority 0-100% */
 161                 ticks = 0;      /* null ticks counter, we start again */
 162
 163
 164         if (_curr_task->priority)       /* is it on kernel level ? No ? Let's continue */
 165                 if ((100 - _curr_task->priority) < ticks)
 166                         return;
 167
 168         if(setjmp (_curr_task->state))  /* set current task */
 169                 return;
 170
 171         while (1) {
 172                 _curr_task = _curr_task->next;  /* continue on next task */
 173
 174                 if (_curr_task == &task_list)   /* task is out of task_list structure */
 175                         _curr_task = task_list.next;    /* current task is first task in task_list structure */
 176
 177                 if (_curr_task->status == TS_RUNNABLE) {        /* Is current task running ? */
 178                         timer_wait (1);                         /* prevent before kernel freeze or stack fault */
 179                         longjmp (_curr_task->state, 1);         /* long jump to task function */
 180                         return;
 181                 }
 182         }
 183
 184 }
 185 /*****************************************************************************
 186 *****************************************************************************/
 187
 188 unsigned task_create (char *name, unsigned entry, unsigned priority)
 189 {
 190         task_id ++;     // increase new task
 191
 192         if (priority > 100)     /* priority 100 is max */
 193                 priority = 100;
 194
 195         task_t *task;
 196
 197         /* alloc and init context */
 198         task = (task_t *) kmalloc (sizeof (task_t));
 199
 200         if (entry == NULL) {
 201                 /* mark task #0 (idle task) runnable */
 202                 task->status = TS_RUNNABLE;
 203
 204                 task->priority = priority;
 205                 // add name of task
 206                 strcpy (task->name, name);
 207
 208                 /* add into list */
 209                 task->next = &task_list;
 210                 task->prev = task_list.prev;
 211                 task->prev->next = task;
 212                 task->next->prev = task;
 213
 214                 /* set _curr_task so schedule() will save state of task #0 */
 215                 _curr_task = task;
 216                 return 1;
 217         }
 218
 219         (void) setjmp (task->state);
 220         // ...especially the stack pointer
 221         unsigned adr = (unsigned) (task->stacks + USER_STACK_SIZE);
 222         task->state[0].JMPBUF_SP = adr;
 223         // ...and program counter
 224         task->state[0].JMPBUF_IP = entry;
 225         // set EFLAGS value to enable interrupts
 226         task->state[0].JMPBUF_FLAGS = 0x200;
 227         // mark it runnable
 228         task->status = TS_RUNNABLE;
 229         // task priority - how offten will be active
 230         task->priority = priority;
 231         // add name of task
 232         strcpy (task->name, name);
 233
 234         /* add into list */
 235         task->next = &task_list;
 236         task->prev = task_list.prev;
 237         task->prev->next = task;
 238         task->next->prev = task;
 239
 240         kprintf ("task -> %s (%d)\n", name, task_id);
 241
 242         return 1;
 243 }
 244
 245 unsigned int init_tasks (void)
 246 {
 247         task_list.next = &task_list;
 248         task_list.prev = &task_list;
 249
 250         if (!task_create ("kernel", NULL, 0))
 251                 return 0;
 252
 253         /*if (!task_create ("shell", (unsigned) task_shell, 50))
 254                 return 0;
 255
 256         if (!task_create ("fdd", (unsigned) fdd_task, 25))
 257                 return 0;*/
 258
 259         return 1;
 260 }