209 lines
4.3 KiB
ArmAsm
209 lines
4.3 KiB
ArmAsm
/*
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* Multiboot Option ROM
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*
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* Copyright Novell Inc, 2009
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* Authors: Alexander Graf <agraf@suse.de>
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*/
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#define NO_QEMU_PROTOS
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#include "../../hw/fw_cfg.h"
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#define BIOS_CFG_IOPORT_CFG 0x510
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#define BIOS_CFG_IOPORT_DATA 0x511
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#define MULTIBOOT_MAGIC 0x2badb002
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/* Read a variable from the fw_cfg device.
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Clobbers: %edx
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Out: %eax */
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.macro read_fw VAR
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mov $\VAR, %ax
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mov $BIOS_CFG_IOPORT_CFG, %dx
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outw %ax, (%dx)
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mov $BIOS_CFG_IOPORT_DATA, %dx
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inb (%dx), %al
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shl $8, %eax
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inb (%dx), %al
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shl $8, %eax
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inb (%dx), %al
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shl $8, %eax
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inb (%dx), %al
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bswap %eax
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.endm
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.code16
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.text
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.global _start
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_start:
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.short 0xaa55
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.byte 1 /* (_end - _start) / 512 */
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push %eax
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push %ds
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/* setup ds so we can access the IVT */
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xor %ax, %ax
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mov %ax, %ds
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/* save old int 19 */
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mov (0x19*4), %eax
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mov %eax, %cs:old_int19
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/* install our int 19 handler */
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movw $int19_handler, (0x19*4)
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mov %cs, (0x19*4+2)
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pop %ds
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pop %eax
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lret
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int19_handler:
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/* DS = CS */
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movw %cs, %ax
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movw %ax, %ds
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/* fall through */
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run_multiboot:
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cli
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cld
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mov %cs, %eax
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shl $0x4, %eax
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/* fix the gdt descriptor to be PC relative */
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mov (gdt_desc+2), %ebx
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add %eax, %ebx
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mov %ebx, (gdt_desc+2)
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/* fix the prot mode indirect jump to be PC relative */
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mov (prot_jump), %ebx
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add %eax, %ebx
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mov %ebx, (prot_jump)
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/* FS = bootinfo_struct */
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read_fw FW_CFG_INITRD_ADDR
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shr $4, %eax
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mov %ax, %fs
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/* ES = mmap_addr */
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read_fw FW_CFG_INITRD_SIZE
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shr $4, %eax
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mov %ax, %es
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/* Initialize multiboot mmap structs using int 0x15(e820) */
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xor %ebx, %ebx
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/* mmap start after first size */
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movl $4, %edi
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mmap_loop:
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/* entry size (mmap struct) & max buffer size (int15) */
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movl $20, %ecx
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/* store entry size */
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movl %ecx, %es:-4(%edi)
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/* e820 */
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movl $0x0000e820, %eax
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/* 'SMAP' magic */
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movl $0x534d4150, %edx
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int $0x15
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mmap_check_entry:
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/* last entry? then we're done */
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jb mmap_done
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and %bx, %bx
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jz mmap_done
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/* valid entry, so let's loop on */
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mmap_store_entry:
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/* %ax = entry_number * 24 */
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mov $24, %ax
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mul %bx
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mov %ax, %di
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movw %di, %fs:0x2c
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/* %di = 4 + (entry_number * 24) */
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add $4, %di
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jmp mmap_loop
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mmap_done:
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real_to_prot:
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/* Load the GDT before going into protected mode */
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lgdt:
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data32 lgdt %cs:gdt_desc
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/* get us to protected mode now */
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movl $1, %eax
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movl %eax, %cr0
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/* the LJMP sets CS for us and gets us to 32-bit */
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ljmp:
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data32 ljmp *%cs:prot_jump
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prot_mode:
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.code32
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/* initialize all other segments */
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movl $0x10, %eax
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movl %eax, %ss
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movl %eax, %ds
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movl %eax, %es
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movl %eax, %fs
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movl %eax, %gs
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/* Jump off to the kernel */
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read_fw FW_CFG_KERNEL_ADDR
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mov %eax, %ecx
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/* EBX contains a pointer to the bootinfo struct */
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read_fw FW_CFG_INITRD_ADDR
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movl %eax, %ebx
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/* EAX has to contain the magic */
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movl $MULTIBOOT_MAGIC, %eax
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ljmp2:
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jmp *%ecx
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/* Variables */
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.align 4, 0
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old_int19: .long 0
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prot_jump: .long prot_mode
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.short 8
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.align 4, 0
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gdt:
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/* 0x00 */
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.byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
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/* 0x08: code segment (base=0, limit=0xfffff, type=32bit code exec/read, DPL=0, 4k) */
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.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9a, 0xcf, 0x00
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/* 0x10: data segment (base=0, limit=0xfffff, type=32bit data read/write, DPL=0, 4k) */
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.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0xcf, 0x00
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/* 0x18: code segment (base=0, limit=0x0ffff, type=16bit code exec/read/conf, DPL=0, 1b) */
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.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9e, 0x00, 0x00
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/* 0x20: data segment (base=0, limit=0x0ffff, type=16bit data read/write, DPL=0, 1b) */
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.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0x00, 0x00
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gdt_desc:
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.short (5 * 8) - 1
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.long gdt
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.align 512, 0
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_end:
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