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Diffstat (limited to 'src/boot.S')
| -rw-r--r-- | src/boot.S | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/src/boot.S b/src/boot.S new file mode 100644 index 0000000..0519b7e --- /dev/null +++ b/src/boot.S @@ -0,0 +1,100 @@ +/* + * <boot.S> + * + * First stage BIOS loader for Open Hack'Ware. + * + * Copyright (C) 2004-2005 Jocelyn Mayer (l_indien@magic.fr) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License V2 + * as published by the Free Software Foundation + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ +/* + * setup one RAM bank then + * relocate the one page BIOS second stage into RAM. + * + * We consider that we know nothing about the CPU state + * at the time we enter this code. + * + */ + +#define ASSEMBLY_CODE +#include "bios.h" + +.section .rom, "ax" +.align 2 +_boot_start: + /* Minimal setup */ + li r0, 0 ; + /* r11 is _boot_start address */ + mflr r11 ; + addi r11, r11, (_boot_start - _start - 4) ; + /* Disable MMU and interruptions */ + addi r12, r11, (_boot_no_mmu - _boot_start) ; + mtspr SRR0, r12 ; + mfmsr r12 ; + lis r13, 0x0004 ; + ori r13, r13, 0xEF71 ; + andc r15, r12, r13 ; + mtspr SRR1, r12 ; + rfi ; +_boot_no_mmu: + /* TODO: initialize physical RAM (we need at least one page) + * before doing anything else. + * This may be machine dependent code. + */ +_boot_copy: + /* Copy the second stage bootloader into RAM + * We may need a tiny driver if we need to boot from special device + * (ie disc-on-chip, ...) + */ + lis r12, (VECTORS_SIZE / 4)@h ; + ori r12, r12, (VECTORS_SIZE / 4)@l ; + mtctr r12 ; + clrrwi r12, r11, BIOS_IMAGE_BITS ; + addis r3, r12, VECTORS_SIZE@h ; + addi r3, r3, VECTORS_SIZE@l ; + subi r12, r12, 4 ; + lis r13, VECTORS_BASE@h ; + ori r13, r13, VECTORS_BASE@l ; + mtlr r13 ; + subi r13, r13, 4 ; +_boot_copy_loop: + lwzu r14, 4(r12) ; + stwu r14, 4(r13) ; + bdnz _boot_copy_loop ; + /* Synchronize the whole execution context */ + addi r12, r11, (_boot_sync - _boot_start) ; + mtspr SRR0, r12 ; + mfmsr r12 ; + mtspr SRR1, r12 ; + rfi ; +_boot_sync: + /* All done, jump into the loaded code */ + blrl ; + /* If we ever return, reboot */ + b _start ; + +.space BOOT_SIZE - 4 - (. - _boot_start), 0xFF +/* Reset entry point */ + . = 0x1FC +_start: + bl _boot_start ; |