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jeremybenn |
/*
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* crt0_redboot.S -- Minimal startup file for MN10300 targets running Redboot.
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*
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* Copyright (c) 2001 Red Hat, Inc.
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* Derived from crt0_cygmon.S - Copyright (c) 1995, 1996, 1997, 2000 Red Hat, Inc.
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*
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* The authors hereby grant permission to use, copy, modify, distribute,
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* and license this software and its documentation for any purpose, provided
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* that existing copyright notices are retained in all copies and that this
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* notice is included verbatim in any distributions. No written agreement,
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* license, or royalty fee is required for any of the authorized uses.
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* Modifications to this software may be copyrighted by their authors
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* and need not follow the licensing terms described here, provided that
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* the new terms are clearly indicated on the first page of each file where
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* they apply.
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*/
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/*
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* This file contains the minimal startup code necessary.
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* This will not do any hardware initialization. It is assumed that we are talking to Redboot
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* and therefore the hardware will be initialized properly.
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*/
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/*
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* Set up some room for a stack. We just grab a chunk of memory.
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*/
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#define STACK_SIZE 0x4000
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#define GLOBAL_SIZE 0x2000
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#define STARTUP_STACK_SIZE 0x0100
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.comm __memsize, 12
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.comm __lstack, STARTUP_STACK_SIZE
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.comm __stackbase,4
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.section .text
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.global _start
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_start:
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/*
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* Setup a small stack so we can run some C code,
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* and get the usable memory size.
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*/
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mov __lstack,a0
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add STARTUP_STACK_SIZE-4,a0
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mov a0,sp
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/*
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* zero out the bss section.
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*/
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.global __memsize
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.global _get_mem_info
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zerobss:
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mov __bss_start, a0 # These variables are defined in the linker script
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mov _end, a1
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cmp a0, a1 # If no bss, then do nothing
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beq 7f
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clr d0
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3:
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movbu d0,(a0) # Clear a byte and bump pointer
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inc a0
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cmp a0, a1
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bne 3b
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7:
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/*
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* Setup the stack pointer --
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* get_mem_info returns the top of memory, so just use that In
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* addition, we must subtract 24 bytes for the 3 8 byte
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* arguments to main, in case main wants to write them back to
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* the stack. The caller is supposed to allocate stack space
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* for parameters in registers in the old MIPS ABIs. We must
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* do this even though we aren't passing arguments, because
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* main might be declared to have them.
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* Some ports need a larger alignment for the stack, so we
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* subtract 32, which satisifes the stack for the arguments and
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* keeps the stack pointer better aligned.
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*/
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mov __memsize, d0
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call _get_mem_info,[],0
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sub 32, a0
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mov a0, sp
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mov __stackbase, a1
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mov a0, (a1) # keep this for future ref
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call ___main,[],0 # Call __main to run ctors/dtors
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clr d0
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clr d1
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mov d0, (4,sp)
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or 0x0800,psw # Enable interrupts
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call _main,[],0 # Call main program
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call _exit,[],0
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/* EOF crt0_redboot.S */
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