arch/all-unix/exec/newstackswap.c

   1 /*
   2     Copyright © 1995-2011, 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/asmcall.h>
  10 #include <aros/debug.h>
  11 #include <exec/tasks.h>
  12 #include <proto/exec.h>
  13
  14 /*
  15  * The following includes need to go in this particular order!
  16  * We need to define _XOPEN_SOURCE (done in the first line of exec_platform.h)
  17  * for the proper context definition under Darwin before include any host headers,
  18  * otherwise ucontext_t will get only partial definition and getcontext() will clobber
  19  * your stack!
  20  */
  21 #include "exec_intern.h"
  22
  23 #include <signal.h>
  24 #include <string.h>
  25
  26 static void trampoline(IPTR (*func)(), IPTR *ret, IPTR *args)
  27 {
  28     /* this was called from NewStackSwap() which also called Disable */
  29     Enable();
  30
  31 #if DEBUG
  32     int i;
  33
  34     bug("[NewStackSwap] Stack swapping done\n");
  35     bug("[NewStackSwap] SP at 0x%p\n", AROS_GET_SP);
  36     bug("[NewStackSwap] Function address: 0x%p\n", func);
  37     for (i = 0; i < 8; i++)
  38         bug("[NewStackSwap] args[%u] = 0x%p\n", i, (void *)args[i]);
  39 #endif
  40
  41     *ret = func(args[0], args[1], args[2], args[3],
  42                 args[4], args[5], args[6], args[7]);
  43
  44     /* this was called from NewStackSwap() which will enable again */
  45     Disable();
  46 }
  47
  48 AROS_LH3(IPTR, NewStackSwap,
  49          AROS_LHA(struct StackSwapStruct *,  sss, A0),
  50          AROS_LHA(LONG_FUNC, entry, A1),
  51          AROS_LHA(struct StackSwapArgs *, args, A2),
  52          struct ExecBase *, SysBase, 134, Exec)
  53 {
  54     AROS_LIBFUNC_INIT
  55
  56     struct Task *me = FindTask(NULL);
  57     IPTR ret;
  58     volatile APTR splower, spupper;
  59     ucontext_t ucx, ucx_return;
  60
  61     D(bug("NewStackSwap(0x%p, 0x%p, 0x%p, 0x%p)\n", sss, entry, args, SysBase));
  62     DB2(bug("[NewStackSwap] Context size: %u\n", sizeof(ucontext_t)));
  63
  64     Disable();  /* To avoid random crashes during startup */
  65     PD(SysBase).SysIFace->getcontext(&ucx);
  66     AROS_HOST_BARRIER
  67     Enable();
  68
  69     D(bug("[NewStackSwap] getcontext() done, arguments: 0x%p, 0x%p, 0x%p, 0x%p\n", sss, entry, args, SysBase));
  70
  71     /* Prepare the alternate stack */
  72     ucx.uc_stack.ss_sp    = sss->stk_Lower;
  73     ucx.uc_stack.ss_size  = (size_t)sss->stk_Pointer - (size_t)sss->stk_Lower;
  74     ucx.uc_stack.ss_flags = SS_ONSTACK;
  75     ucx.uc_link           = &ucx_return;
  76
  77     if (me->tc_Flags & TF_STACKCHK)
  78         memset(ucx.uc_stack.ss_sp, 0xE1, ucx.uc_stack.ss_size);
  79
  80     D(bug("[NewStackSwap] Prepared stack: 0x%p - 0x%p (size %u bytes)\n", sss->stk_Lower, sss->stk_Pointer, ucx.uc_stack.ss_size));
  81
  82     PD(SysBase).SysIFace->makecontext(&ucx, (void *(*)()) trampoline, 3, entry, &ret, args->Args);
  83     AROS_HOST_BARRIER
  84
  85     DB2(bug("[NewStackSwap] Prepared context, doing stack swap\n"));
  86
  87     /* Remember original stack limits */
  88     splower = me->tc_SPLower;
  89     spupper = me->tc_SPUpper;
  90
  91     /* Disable(), otherwise stack check will fail */
  92     Disable();
  93
  94     /* Set new stack limits, swapcontext() will change the stack itself */
  95     me->tc_SPLower = sss->stk_Lower;
  96     me->tc_SPUpper = sss->stk_Upper;
  97
  98     /* We Enable() in trampoline */
  99     PD(SysBase).SysIFace->swapcontext(&ucx_return, &ucx);
 100     AROS_HOST_BARRIER
 101
 102     me->tc_SPLower = splower;
 103     me->tc_SPUpper = spupper;
 104     Enable();
 105
 106     return ret;
 107
 108     AROS_LIBFUNC_EXIT
 109 } /* NewStackSwap() */