1 | /* bspclean.c |
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2 | * |
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3 | * These routines return control to 167Bug after a normal exit from the |
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4 | * application. |
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5 | * |
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6 | * COPYRIGHT (c) 1989-1999. |
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7 | * On-Line Applications Research Corporation (OAR). |
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8 | * |
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9 | * The license and distribution terms for this file may be |
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10 | * found in the file LICENSE in this distribution or at |
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11 | * http://www.OARcorp.com/rtems/license.html. |
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12 | * |
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13 | * Modifications of respective RTEMS files: |
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14 | * Copyright (c) 1998, National Research Council of Canada |
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15 | * |
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16 | * $Id$ |
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17 | */ |
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18 | |
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19 | #include <rtems.h> |
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20 | #include <bsp.h> |
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21 | #include <page_table.h> |
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22 | |
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23 | /* |
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24 | * bsp_return_to_monitor_trap |
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25 | * |
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26 | * Switch the VBR back to ROM and make a .RETURN syscall to return control to |
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27 | * 167 Bug. If 167Bug ever returns, restart the application. |
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28 | * |
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29 | * Input parameters: NONE |
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30 | * |
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31 | * Output parameters: NONE |
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32 | * |
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33 | * Return values: NONE |
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34 | */ |
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35 | static void bsp_return_to_monitor_trap( void ) |
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36 | { |
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37 | extern void start( void ); |
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38 | |
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39 | register volatile void *start_addr; |
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40 | |
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41 | page_table_teardown(); |
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42 | |
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43 | lcsr->intr_ena = 0; /* disable interrupts */ |
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44 | m68k_set_vbr(0xFFE00000); /* restore 167Bug vectors */ |
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45 | asm volatile( "trap #15 /* trap to 167Bug */ |
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46 | .short 0x63" ); /* return to 167Bug (.RETURN) */ |
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47 | |
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48 | /* restart program */ |
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49 | start_addr = start; |
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50 | asm volatile( "jmp %0@" : "=a" (start_addr) : "0" (start_addr) ); |
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51 | } |
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52 | |
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53 | /* |
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54 | * bsp_cleanup |
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55 | * |
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56 | * This code was copied from other MC680x0 MVME BSPs. |
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57 | * Our guess is that someone was concerned about the CPU no longer being in |
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58 | * supervisor mode when they got here. This function forces the CPU back to |
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59 | * supervisor mode so the VBR may be changed. It places the address of the |
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60 | * function that makes a 167Bug .RETURN syscall in the trap 13 entry in the |
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61 | * exception vector, and then issues a trap 13 call. It is also possible that |
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62 | * the code was copied from some other OS that does run tasks in user mode. |
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63 | * In any case, it appears to be a bit of paranoia, and could lead to |
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64 | * problems if 167Bug is invoked before we get to switch the VBR back to |
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65 | * 167Bug because trap 13 is documented as being reserved for the internal |
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66 | * use of the debugger. |
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67 | * |
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68 | * Prototyped in rtems/c/src/lib/libbsp/m68k/mvme167/include/bsp.h |
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69 | * |
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70 | * Input parameters: NONE |
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71 | * |
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72 | * Output parameters: NONE |
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73 | * |
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74 | * Return values: DOES NOT RETURN |
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75 | */ |
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76 | void bsp_cleanup( void ) |
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77 | { |
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78 | M68Kvec[ 45 ] = bsp_return_to_monitor_trap; |
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79 | asm volatile( "trap #13" ); |
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80 | } |
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