rom/exec/traphandler.c

   1 /*
   2     Copyright © 1995-2012, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Default trap handler
   6     Lang: english
   7 */
   8
   9 #include <exec/alerts.h>
  10 #include <exec/interrupts.h>
  11 #include <exec/tasks.h>
  12 #include <proto/exec.h>
  13
  14 #include "etask.h"
  15 #include "exec_intern.h"
  16 #include "exec_util.h"
  17
  18 /* User-mode code where the task jumps to.
  19  * NOTE: This is only called on ETasks!
  20  */
  21 static void Exec_CrashHandler(void)
  22 {
  23     struct Task *task = FindTask(NULL);
  24     struct IntETask *iet = GetIntETask(task);
  25
  26     /* Makes Alert() attempting to bring up Intuition requester */
  27     iet->iet_AlertFlags &= ~AF_Alert;
  28
  29     Alert(iet->iet_AlertCode);
  30 }
  31
  32 /* In original AmigaOS the trap handler is entered in supervisor mode with the
  33  * following on the supervisor stack:
  34  *  0(sp).l = trap#
  35  *  4(sp) Processor dependent exception frame
  36  * In our current implementation we use two pointers on stack. The idea is taken
  37  * from AmigaOS v4.
  38  *
  39  * For m68k, we need a thunk, since we will call this routine via
  40  * the AOS 1.x-3.x method described above.
  41  *
  42  * See arch/m68k-all/kernel/m68k_exception.c for implementation details.
  43  */
  44 #ifdef __mc68000
  45 asm (
  46         "       .text\n"
  47         "       .balign 2\n"
  48         "       .global Exec_TrapHandler\n"
  49         "Exec_TrapHandler:\n"
  50         "       movem.l %d0-%d7/%a0-%a6,%sp@-\n"   /* Save regs */
  51         "       move.l  %sp@(15*4),%d0\n"          /* Get trap code */
  52         "       move.l  %usp,%a0\n"          /* Get USP */
  53         "       move.l  %a0,%sp@(15*4)\n"    /* Fix up A7 to be USP */
  54         "       move.l  %sp,%sp@-\n"    /* Push on pointer to exception ctx */
  55         "       move.l  %d0,%sp@-\n"    /* Push on trap number */
  56         "       jsr Exec__TrapHandler\n" /* Call C routine */
  57         "       addq.l  #8,%sp\n"       /* Pop off C routine args */
  58         "       movem.l %sp@+,%d0-%d7/%a0-%a5\n"  /* Restore registers */
  59         "       move.l  %sp@(4), %a6\n"
  60         "       move.l  %a6,%usp\n"     /* Restore USP */
  61         "       move.l  %sp@+,%a6\n"    /* Restore A6 */
  62         "       addq.l  #4,%sp\n"       /* Skip past A7 */
  63         "       rte\n"                  /* Return from trap */
  64         );
  65 void Exec__TrapHandler(ULONG trapNum, struct ExceptionContext *ctx)
  66 #else
  67 void Exec_TrapHandler(ULONG trapNum, struct ExceptionContext *ctx)
  68 #endif
  69 {
  70     struct Task *task = SysBase->ThisTask;
  71
  72     /* Our situation is deadend */
  73     trapNum |= AT_DeadEnd;
  74
  75     /*
  76      * We must have a valid ETask in order to be able
  77      * to display a requester in user mode.
  78      */
  79     if (task && (task->tc_Flags & TF_ETASK) && (task->tc_State != TS_REMOVED))
  80     {
  81         /* Get internal task structure */
  82         struct IntETask *iet = GetIntETask(task);
  83
  84         if (iet->iet_AlertFlags & AF_Alert)
  85         {
  86             /*
  87              * Protection against double-crash. If the task is already in alert state,  we have
  88              * a second crash during processing the first one. Then we just pick up initial alert code
  89              * and call Alert() with it in supervisor mode.
  90              */
  91             trapNum = iet->iet_AlertCode;
  92         }
  93         else
  94         {
  95             /*
  96              * Otherwise we can try to send the crash to user level.
  97              *
  98              * First mark crash condition, and also specify alert code for user-level handler.
  99              * If we double-crash while jumping to user mode, we will know this (ETF_Alert will
 100              * already be set)
 101              */
 102             iet->iet_AlertType     = AT_CPU;
 103             iet->iet_AlertFlags    = AF_Alert|AF_Location;
 104             iet->iet_AlertCode     = trapNum;
 105             iet->iet_AlertLocation = (APTR)ctx->PC;    /* Location is our PC, where we crashed */
 106             iet->iet_AlertStack    = (APTR)ctx->FP;    /* Remember also stack frame for backtrace */
 107
 108             /*
 109              * This is a CPU alert. We've got a full CPU context, so we remember it
 110              * in our ETask structure for displaying to the user later.
 111              * Note that we store only GPR part of the context. We don't copy
 112              * attached FPU data (if any). This can be considered TODO.
 113              */
 114             CopyMem(ctx, &iet->iet_AlertData, sizeof(struct ExceptionContext));
 115
 116             /*
 117              * Make the task to jump to crash handler. We don't care about return address etc because
 118              * the alert is deadend anyway.
 119              */
 120             ctx->PC = (IPTR)Exec_CrashHandler;
 121             /* Let the task go */
 122             return;
 123         }
 124     }
 125
 126     Exec_ExtAlert(trapNum, (APTR)ctx->PC, (APTR)ctx->FP, AT_CPU, ctx, SysBase);
 127 } /* TrapHandler */