arch/arm-all/exec/newstackswap.c

   1 /*
   2     Copyright © 1995-2014, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: NewStackSwap() - Call a function with swapped stack, ARM version
   6     Lang: english
   7 */
   8
   9 #include <aros/debug.h>
  10 #include <exec/tasks.h>
  11 #include <proto/exec.h>
  12
  13 #define _PUSH(sp, val) *--sp = (IPTR)val
  14
  15 AROS_LH3(IPTR, NewStackSwap,
  16         AROS_LHA(struct StackSwapStruct *,  sss, A0),
  17         AROS_LHA(LONG_FUNC, entry, A1),
  18         AROS_LHA(struct StackSwapArgs *, args, A2),
  19         struct ExecBase *, SysBase, 134, Exec)
  20 {
  21     AROS_LIBFUNC_INIT
  22
  23     volatile struct Task *t = FindTask(NULL);
  24     volatile IPTR *sp = sss->stk_Pointer;
  25     volatile APTR spreg = t->tc_SPReg;
  26     volatile APTR splower = t->tc_SPLower;
  27     volatile APTR spupper = t->tc_SPUpper;
  28     IPTR ret;
  29
  30     if (args != NULL)
  31     {
  32         /* Only last four arguments are put to stack in ARM */
  33         _PUSH(sp, args->Args[7]);
  34         _PUSH(sp, args->Args[6]);
  35         _PUSH(sp, args->Args[5]);
  36         _PUSH(sp, args->Args[4]);
  37     }
  38     else
  39     {
  40         /* Dummy args to be put in registers below */
  41         args = splower;
  42     }
  43
  44     if (t->tc_Flags & TF_STACKCHK)
  45     {
  46         UBYTE* startfill = sss->stk_Lower;
  47
  48         while (startfill < (UBYTE *)sp)
  49             *startfill++ = 0xE1;
  50     }
  51
  52     /*
  53      * We need to Disable() before changing limits and SP, otherwise
  54      * stack check will fail if we get interrupted in the middle of this
  55      */
  56     D(bug("[NewStackSwap] SP 0x%p, entry point 0x%p\n", sp, entry));
  57     Disable();
  58
  59     /* Change limits. The rest is done in asm below */
  60     t->tc_SPReg = (APTR)sp;
  61     t->tc_SPLower = sss->stk_Lower;
  62     t->tc_SPUpper = sss->stk_Upper;
  63
  64     asm volatile
  65     (
  66     /* Save original SP by adding one more stack frame */
  67     "   push    {fp}\n"
  68     "   add     fp, sp, #4\n"
  69     /* Actually change the stack */
  70     "   mov     sp, %2\n"
  71
  72     /* Enable(). It preserves all registers by convention. */
  73     "   mov     r0, %4\n"
  74     "   ldr     r12, [r0, #-84]\n"
  75     "   blx     r12\n"
  76
  77     /* Call our function with its arguments */
  78     "   ldr     r0, [%3, #0]\n"
  79     "   ldr     r1, [%3, #4]\n"
  80     "   ldr     r2, [%3, #8]\n"
  81     "   ldr     r3, [%3, #12]\n"
  82     "   blx     %1\n"
  83
  84     /* Disable(). r0 is first argument, so save it. */
  85     "   push    {r0}\n"
  86     "   ldr     r0, _sysbase\n"
  87     "   ldr     r0, [r0]\n"
  88     "   ldr     r12, [r0, #-80]\n"
  89     "   blx     r12\n"
  90     "   pop     {%0}\n"
  91
  92     /* Restore original SP. Function's return value is in %0 now. */
  93     "   sub     sp, fp, #4\n"
  94     "   pop     {fp}\n"
  95     : "=r"(ret)
  96     : "r"(entry), "r"(sp), "r"(args), "r"(SysBase)
  97     : "r0", "r1", "r2", "r3", "r12", "lr", "cc");
  98
  99     /* Change limits back and return */
 100     t->tc_SPReg = spreg;
 101     t->tc_SPLower = splower;
 102     t->tc_SPUpper = spupper;
 103     Enable();
 104
 105     D(bug("[NewStackSwap] Returning 0x%p\n", ret));
 106     return ret;
 107
 108     AROS_LIBFUNC_EXIT
 109 } /* NewStackSwap() */
 110
 111 /* Reference to a global SysBase */
 112 asm ("_sysbase: .word SysBase");