arch/i386-all/exec/newstackswap.c

   1 /*
   2     Copyright © 1995-2012, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: NewStackSwap() - Call a function with swapped stack.
   6     Lang: english
   7 */
   8
   9 #include <aros/config.h>
  10 #include <aros/debug.h>
  11 #include <exec/tasks.h>
  12 #include <proto/exec.h>
  13
  14 #define _PUSH(sp, val) *--sp = (IPTR)val
  15
  16 AROS_LH3(IPTR, NewStackSwap,
  17         AROS_LHA(struct StackSwapStruct *,  sss, A0),
  18         AROS_LHA(LONG_FUNC, entry, A1),
  19         AROS_LHA(struct StackSwapArgs *, args, A2),
  20         struct ExecBase *, SysBase, 134, Exec)
  21 {
  22     AROS_LIBFUNC_INIT
  23
  24     volatile struct Task *t = FindTask(NULL);
  25     volatile IPTR *sp = sss->stk_Pointer;
  26     volatile APTR splower = t->tc_SPLower;
  27     volatile APTR spupper = t->tc_SPUpper;
  28     IPTR ret;
  29     BYTE i;
  30
  31     /* Put arguments on stack in appropriate order */
  32     for (i = 7; i >= 0; i--)
  33     {
  34         D(bug("[NewStackSwap] Argument %d value 0x%08lX\n", i, args->Args[i]));
  35         _PUSH(sp, args->Args[i]);
  36     }
  37
  38     if (t->tc_Flags & TF_STACKCHK)
  39     {
  40         volatile UBYTE* startfill = sss->stk_Lower;
  41
  42         while (startfill < (UBYTE *)sp)
  43             *startfill++ = 0xE1;
  44     }
  45
  46     /*
  47      * We need to Disable() before changing limits and SP, otherwise
  48      * stack check will fail if we get interrupted in the middle of this
  49      */
  50     D(bug("[NewStackSwap] SP 0x%p, entry point 0x%p\n", sp, entry));
  51     Disable();
  52
  53     /* Change limits. The rest is done in asm below */
  54     t->tc_SPLower = sss->stk_Lower;
  55     t->tc_SPUpper = sss->stk_Upper;
  56
  57     asm volatile
  58     (
  59     /* Save original ESP by setting up a new stack frame */
  60     "   push    %%ebp\n"
  61     "   movl    %%esp, %%ebp\n"
  62     /* Actually change the stack */
  63     "   movl    %2, %%esp\n\t"
  64
  65     /* Enable(). Pass SysBase in %eax, We don't need %eax afterwards */
  66     "   call    *-84(%0)\n"
  67
  68     /* Call our function */
  69     "   call    *%1\n"
  70
  71     /*
  72      * Disable().
  73      * Remember %eax (e.g. %0) and put local SysBase of this function in it.
  74      * %3 was clobbered by the called function.
  75      */
  76     "   push    %0\n"
  77     "   movl    SysBase, %0\n"
  78     "   call    *-80(%0)\n"
  79     "   pop     %0\n"
  80
  81     /* Restore original ESP. Function's return value is in EAX. */
  82     "   movl    %%ebp, %%esp\n"
  83     "   pop     %%ebp\n"
  84     : "=a"(ret)
  85     : "r"(entry), "r"(sp), "a"(SysBase)
  86     : "ecx", "edx", "cc");
  87
  88     /* Change limits back and return */
  89     t->tc_SPLower = splower;
  90     t->tc_SPUpper = spupper;
  91     Enable();
  92
  93     D(bug("[NewStackSwap] Returning 0x%08lX\n", ret));
  94     return ret;
  95
  96     AROS_LIBFUNC_EXIT
  97 } /* NewStackSwap() */