[ac7d5ef0] | 1 | /* _load_segments |
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| 2 | * |
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| 3 | * This file assists the board independent startup code by |
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| 4 | * loading the proper segment register values. The values |
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| 5 | * loaded are board dependent. |
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| 6 | * |
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| 7 | * NOTE: No stack has been established when this routine |
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| 8 | * is invoked. It returns by jumping back to bspentry. |
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| 9 | * |
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| 10 | * COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994. |
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| 11 | * On-Line Applications Research Corporation (OAR). |
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| 12 | * All rights assigned to U.S. Government, 1994. |
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| 13 | * |
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| 14 | * This material may be reproduced by or for the U.S. Government pursuant |
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| 15 | * to the copyright license under the clause at DFARS 252.227-7013. This |
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| 16 | * notice must appear in all copies of this file and its derivatives. |
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| 17 | * |
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| 18 | * $Id$ |
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| 19 | */ |
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| 20 | |
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| 21 | #include "asm.h" |
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| 22 | |
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| 23 | BEGIN_CODE |
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| 24 | |
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| 25 | /* |
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| 26 | * FORCEBUG loads us into a virtual address space which |
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| 27 | * really starts at PHYSICAL_ADDRESS_BASE. |
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| 28 | */ |
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| 29 | |
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| 30 | .set PHYSICAL_ADDRESS_BASE, 0x00002000 |
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| 31 | |
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| 32 | /* |
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| 33 | * At reset time, FORCEBUG normally has the segment selectors preloaded. |
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| 34 | * If a human resets the instruction pointer, this will not have occurred. |
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| 35 | * However, no guarantee can be made of the other registers if cs:ip was |
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| 36 | * modified to restart the program. Because of this, the BSP reloads all |
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| 37 | * segment registers (except cs) with the values they have following |
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| 38 | * a reset. |
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| 39 | */ |
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| 40 | |
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| 41 | |
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| 42 | .set RESET_SS, 0x40 # initial value of stack segment register |
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| 43 | .set RESET_DS, 0x40 # initial value of data segment register |
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| 44 | .set RESET_ES, 0x40 # initial value of extra segment register |
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| 45 | .set RESET_FS, 0x40 # initial value of "f" segment register |
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| 46 | .set RESET_GS, 0x30 # initial value of "g" segment register |
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| 47 | |
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| 48 | |
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| 49 | #define LOAD_SEGMENTS(_value,_segment) \ |
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| 50 | movw $ ## _value, ax ; \ |
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[767a6c6] | 51 | movw ax, _segment |
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[ac7d5ef0] | 52 | |
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| 53 | EXTERN (establish_stack) |
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| 54 | |
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| 55 | PUBLIC (_load_segments) |
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| 56 | SYM (_load_segments): |
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| 57 | LOAD_SEGMENTS( RESET_SS, ss ) |
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| 58 | LOAD_SEGMENTS( RESET_DS, ds ) |
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| 59 | LOAD_SEGMENTS( RESET_ES, es ) |
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| 60 | LOAD_SEGMENTS( RESET_FS, fs ) |
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| 61 | LOAD_SEGMENTS( RESET_GS, gs ) |
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| 62 | |
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| 63 | jmp SYM (_establish_stack) # return to the bsp entry code |
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| 64 | |
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| 65 | PUBLIC (_return_to_monitor) |
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| 66 | SYM (_return_to_monitor): |
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| 67 | |
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| 68 | call SYM (Clock_exit) |
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| 69 | movb $0,al |
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| 70 | int $0x20 # restart FORCEbug |
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| 71 | jmp SYM (start) # FORCEbug does not reset PC |
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| 72 | |
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| 73 | END_CODE |
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| 74 | |
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| 75 | BEGIN_DATA |
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| 76 | |
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| 77 | PUBLIC (_Do_Load_IDT) |
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| 78 | SYM (_Do_Load_IDT): |
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| 79 | .byte 1 |
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| 80 | |
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| 81 | PUBLIC (_Do_Load_GDT) |
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| 82 | SYM (_Do_Load_GDT): |
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| 83 | .byte 0 |
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| 84 | |
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| 85 | END_DATA |
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| 86 | END |
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