arch/ppc-sam440/exec/stackswap.c

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: StackSwap() - Swap the stack of a task.
   6     Lang: english
   7 */
   8
   9 /*****************************************************************************
  10
  11     NAME */
  12 #include <exec/tasks.h>
  13 #include <proto/exec.h>
  14
  15         AROS_LH1(void, StackSwap,
  16
  17 /*  SYNOPSIS */
  18         AROS_LHA(struct StackSwapStruct *,  sss, A0),
  19
  20 /*  LOCATION */
  21         struct ExecBase *, SysBase, 122, Exec)
  22
  23 /*  FUNCTION
  24         Changes the stack used by a task. The StackSwapStruct will contain
  25         the value of the old stack such that the stack can be reset to the
  26         previous version by another call to StackSwap().
  27
  28         When the stack is swapped, the data on the stack(s) will not be
  29         altered, so the stack may not be set up for you. It is generally
  30         required that you replace your stack before exiting from the
  31         current stack frame (procedure, function call etc.).
  32
  33     INPUTS
  34         sss     -   A structure containing the values for the upper, lower
  35                     and current bounds of the stack you wish to use. The
  36                     values will be replaced by the current values and you
  37                     can restore the values later.
  38
  39     RESULT
  40         The program will be running on a new stack and sss will contain
  41         the old stack.
  42
  43         Calling StackSwap() twice consequtively will effectively do
  44         nothing.
  45
  46     NOTES
  47         Returning from the function that you call StackSwap() in can have
  48         unexpected results.
  49
  50     EXAMPLE
  51
  52     BUGS
  53
  54     SEE ALSO
  55         AddTask(), RemTask()
  56
  57     INTERNALS
  58         This function MUST be replaced in $(KERNEL) or $(ARCH).
  59
  60 ******************************************************************************/
  61 {
  62     AROS_LIBFUNC_INIT
  63     register IPTR real_sp asm("r1");
  64     IPTR *sp;
  65     IPTR *src;
  66     IPTR *dst;
  67     struct Task *thisTask = FindTask(NULL);
  68     APTR tmp;
  69
  70     dst = sss->stk_Pointer;
  71
  72     Disable();
  73
  74     /* Get the real stack pointer */
  75     asm volatile ("mr %0,%1":"=r"(sp):"r"(real_sp));
  76
  77     /* Go one stack frame upper - now src points to the stackframe of caller */
  78     src = (IPTR*)*sp;
  79
  80     /* Go one more stack frame up. Now you may copy from src to dst (src - sp) IPTR's */
  81     src = (IPTR*)*src;
  82
  83     /* Copy the two stack frames */
  84     while (src != sp)
  85     {
  86         *--dst = *--src;
  87     }
  88
  89     sss->stk_Pointer = dst;
  90
  91     tmp = thisTask->tc_SPLower;
  92     thisTask->tc_SPLower = sss->stk_Lower;
  93     sss->stk_Lower = tmp;
  94
  95     tmp = thisTask->tc_SPUpper;
  96     thisTask->tc_SPUpper = sss->stk_Upper;
  97     sss->stk_Upper = tmp;
  98
  99     tmp = thisTask->tc_SPReg;
 100     thisTask->tc_SPReg = sss->stk_Pointer;
 101     sss->stk_Pointer = tmp;
 102
 103     asm volatile("mr %0,%1"::"r"(real_sp),"r"(dst));
 104
 105     Enable();
 106
 107     AROS_LIBFUNC_EXIT
 108 } /* StackSwap() */