| 1 | /* |
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| 2 | * crt0_redboot.S -- Minimal startup file for MN10300 targets running Redboot. |
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| 3 | * |
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| 4 | * Copyright (c) 2001 Red Hat, Inc. |
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| 5 | * Derived from crt0_cygmon.S - Copyright (c) 1995, 1996, 1997, 2000 Red Hat, Inc. |
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| 6 | * |
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| 7 | * The authors hereby grant permission to use, copy, modify, distribute, |
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| 8 | * and license this software and its documentation for any purpose, provided |
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| 9 | * that existing copyright notices are retained in all copies and that this |
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| 10 | * notice is included verbatim in any distributions. No written agreement, |
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| 11 | * license, or royalty fee is required for any of the authorized uses. |
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| 12 | * Modifications to this software may be copyrighted by their authors |
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| 13 | * and need not follow the licensing terms described here, provided that |
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| 14 | * the new terms are clearly indicated on the first page of each file where |
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| 15 | * they apply. |
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| 16 | */ |
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| 17 | |
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| 18 | /* |
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| 19 | * This file contains the minimal startup code necessary. |
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| 20 | * This will not do any hardware initialization. It is assumed that we are talking to Redboot |
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| 21 | * and therefore the hardware will be initialized properly. |
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| 22 | */ |
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| 23 | |
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| 24 | /* |
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| 25 | * Set up some room for a stack. We just grab a chunk of memory. |
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| 26 | */ |
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| 27 | #define STACK_SIZE 0x4000 |
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| 28 | #define GLOBAL_SIZE 0x2000 |
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| 29 | |
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| 30 | #define STARTUP_STACK_SIZE 0x0100 |
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| 31 | |
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| 32 | .comm __memsize, 12 |
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| 33 | .comm __lstack, STARTUP_STACK_SIZE |
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| 34 | .comm __stackbase,4 |
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| 35 | |
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| 36 | .section .text |
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| 37 | .global _start |
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| 38 | _start: |
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| 39 | /* |
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| 40 | * Setup a small stack so we can run some C code, |
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| 41 | * and get the usable memory size. |
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| 42 | */ |
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| 43 | mov __lstack,a0 |
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| 44 | add STARTUP_STACK_SIZE-4,a0 |
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| 45 | mov a0,sp |
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| 46 | |
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| 47 | /* |
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| 48 | * zero out the bss section. |
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| 49 | */ |
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| 50 | .global __memsize |
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| 51 | .global _get_mem_info |
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| 52 | zerobss: |
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| 53 | mov __bss_start, a0 # These variables are defined in the linker script |
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| 54 | mov _end, a1 |
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| 55 | |
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| 56 | cmp a0, a1 # If no bss, then do nothing |
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| 57 | beq 7f |
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| 58 | |
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| 59 | clr d0 |
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| 60 | 3: |
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| 61 | movbu d0,(a0) # Clear a byte and bump pointer |
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| 62 | inc a0 |
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| 63 | cmp a0, a1 |
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| 64 | bne 3b |
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| 65 | |
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| 66 | 7: |
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| 67 | /* |
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| 68 | * Setup the stack pointer -- |
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| 69 | * get_mem_info returns the top of memory, so just use that In |
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| 70 | * addition, we must subtract 24 bytes for the 3 8 byte |
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| 71 | * arguments to main, in case main wants to write them back to |
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| 72 | * the stack. The caller is supposed to allocate stack space |
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| 73 | * for parameters in registers in the old MIPS ABIs. We must |
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| 74 | * do this even though we aren't passing arguments, because |
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| 75 | * main might be declared to have them. |
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| 76 | * Some ports need a larger alignment for the stack, so we |
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| 77 | * subtract 32, which satisifes the stack for the arguments and |
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| 78 | * keeps the stack pointer better aligned. |
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| 79 | */ |
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| 80 | mov __memsize, d0 |
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| 81 | call _get_mem_info,[],0 |
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| 82 | |
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| 83 | sub 32, a0 |
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| 84 | mov a0, sp |
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| 85 | |
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| 86 | mov __stackbase, a1 |
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| 87 | mov a0, (a1) # keep this for future ref |
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| 88 | |
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| 89 | call ___main,[],0 # Call __main to run ctors/dtors |
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| 90 | clr d0 |
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| 91 | clr d1 |
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| 92 | mov d0, (4,sp) |
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| 93 | or 0x0800,psw # Enable interrupts |
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| 94 | call _main,[],0 # Call main program |
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| 95 | call _exit,[],0 |
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| 96 | |
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| 97 | /* EOF crt0_redboot.S */ |
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