kernel/system/do_segctl.c

   1 /* The kernel call implemented in this file:
   2  *   m_type:    SYS_SEGCTL
   3  *
   4  * The parameters for this kernel call are:
   5  *    m4_l3:    SEG_PHYS        (physical base address)
   6  *    m4_l4:    SEG_SIZE        (size of segment)
   7  *    m4_l1:    SEG_SELECT      (return segment selector here)
   8  *    m4_l2:    SEG_OFFSET      (return offset within segment here)
   9  *    m4_l5:    SEG_INDEX       (return index into remote memory map here)
  10  */
  11 #include "../system.h"
  12
  13 #if USE_SEGCTL
  14
  15 /*===========================================================================*
  16  *                              do_segctl                                    *
  17  *===========================================================================*/
  18 PUBLIC int do_segctl(m_ptr)
  19 register message *m_ptr;        /* pointer to request message */
  20 {
  21 /* Return a segment selector and offset that can be used to reach a physical
  22  * address, for use by a driver doing memory I/O in the A0000 - DFFFF range.
  23  */
  24   u32_t selector;
  25   vir_bytes offset;
  26   int i, index;
  27   register struct proc *rp;
  28   phys_bytes phys = (phys_bytes) m_ptr->SEG_PHYS;
  29   vir_bytes size = (vir_bytes) m_ptr->SEG_SIZE;
  30   int result;
  31
  32   /* First check if there is a slot available for this segment. */
  33   rp = proc_addr(who_p);
  34   index = -1;
  35   for (i=0; i < NR_REMOTE_SEGS; i++) {
  36       if (! rp->p_priv->s_farmem[i].in_use) {
  37           index = i;
  38           rp->p_priv->s_farmem[i].in_use = TRUE;
  39           rp->p_priv->s_farmem[i].mem_phys = phys;
  40           rp->p_priv->s_farmem[i].mem_len = size;
  41           break;
  42       }
  43   }
  44   if (index < 0) return(ENOSPC);
  45
  46        offset = alloc_remote_segment(&selector, &rp->p_seg,
  47                 i, phys, size, USER_PRIVILEGE);
  48        result = OK;
  49
  50   /* Request successfully done. Now return the result. */
  51   m_ptr->SEG_INDEX = index | REMOTE_SEG;
  52   m_ptr->SEG_SELECT = selector;
  53   m_ptr->SEG_OFFSET = offset;
  54   return(result);
  55 }
  56
  57 #endif /* USE_SEGCTL */
  58