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