81 lines
2.3 KiB
ArmAsm
81 lines
2.3 KiB
ArmAsm
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/* Copyright (c) 1997 Paul Mackerras <paulus@cs.anu.edu.au>
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* Initial Power Macintosh COFF version.
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* Copyright (c) 1999 Grant Erickson <grant@lcse.umn.edu>
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* Modifications for IBM PowerPC 400-class processor evaluation
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* boards.
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*
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* Module name: crt0.S
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*
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* Description:
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* Boot loader execution entry point. Clears out .bss section as per
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* ANSI C requirements. Invalidates and flushes the caches over the
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* range covered by the boot loader's .text section. Sets up a stack
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* below the .text section entry point.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <asm/ppc_asm.h>
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.text
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.globl _start
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_start:
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#ifdef XCOFF
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.long __start,0,0
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.globl __start
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__start:
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#endif
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## Flush and invalidate the caches for the range in memory covering
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## the .text section of the boot loader
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lis r9,_start@h # r9 = &_start
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lis r8,_etext@ha #
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addi r8,r8,_etext@l # r8 = &_etext
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3: dcbf r0,r9 # Flush the data cache
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icbi r0,r9 # Invalidate the instruction cache
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addi r9,r9,0x10 # Increment by one cache line
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cmplw cr0,r9,r8 # Are we at the end yet?
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blt 3b # No, keep flushing and invalidating
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sync # sync ; isync after flushing the icache
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isync
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## Clear out the BSS as per ANSI C requirements
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lis r7,_end@ha
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addi r7,r7,_end@l # r7 = &_end
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lis r8,__bss_start@ha #
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addi r8,r8,__bss_start@l # r8 = &_bss_start
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## Determine how large an area, in number of words, to clear
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subf r7,r8,r7 # r7 = &_end - &_bss_start + 1
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addi r7,r7,3 # r7 += 3
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srwi. r7,r7,2 # r7 = size in words.
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beq 2f # If the size is zero, do not bother
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addi r8,r8,-4 # r8 -= 4
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mtctr r7 # SPRN_CTR = number of words to clear
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li r0,0 # r0 = 0
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1: stwu r0,4(r8) # Clear out a word
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bdnz 1b # If we are not done yet, keep clearing
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2:
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#ifdef CONFIG_40x
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## Set up the stack
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lis r9,_start@h # r9 = &_start (text section entry)
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ori r9,r9,_start@l
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subi r1,r9,64 # Start the stack 64 bytes below _start
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clrrwi r1,r1,4 # Make sure it is aligned on 16 bytes.
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li r0,0
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stwu r0,-16(r1)
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mtlr r9
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#endif
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b start # All done, start the real work.
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