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196 lines
4.4 KiB
ArmAsm
196 lines
4.4 KiB
ArmAsm
/*
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* Linux Boot 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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* Based on code in hw/pc.c.
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*/
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#include "optionrom.h"
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#define BOOT_ROM_PRODUCT "Linux loader"
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BOOT_ROM_START
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run_linuxboot:
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cli
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cld
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jmp copy_kernel
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boot_kernel:
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read_fw FW_CFG_SETUP_ADDR
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mov %eax, %ebx
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shr $4, %ebx
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/* All segments contain real_addr */
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mov %bx, %ds
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mov %bx, %es
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mov %bx, %fs
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mov %bx, %gs
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mov %bx, %ss
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/* CX = CS we want to jump to */
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add $0x20, %bx
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mov %bx, %cx
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/* SP = cmdline_addr-real_addr-16 */
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read_fw FW_CFG_CMDLINE_ADDR
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mov %eax, %ebx
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read_fw FW_CFG_SETUP_ADDR
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sub %eax, %ebx
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sub $16, %ebx
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mov %ebx, %esp
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/* Build indirect lret descriptor */
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pushw %cx /* CS */
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xor %ax, %ax
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pushw %ax /* IP = 0 */
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/* Clear registers */
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xor %eax, %eax
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xor %ebx, %ebx
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xor %ecx, %ecx
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xor %edx, %edx
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xor %edi, %edi
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xor %ebp, %ebp
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/* Jump to Linux */
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lret
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copy_kernel:
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/* Read info block in low memory (0x10000 or 0x90000) */
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read_fw FW_CFG_SETUP_ADDR
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shr $4, %eax
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mov %eax, %es
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xor %edi, %edi
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read_fw_blob_addr32_edi(FW_CFG_SETUP)
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cmpw $0x203, %es:0x206 // if protocol >= 0x203
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jae 1f // have initrd_max
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movl $0x37ffffff, %es:0x22c // else assume 0x37ffffff
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1:
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/* Check if using kernel-specified initrd address */
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read_fw FW_CFG_INITRD_ADDR
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mov %eax, %edi // (load_kernel wants it in %edi)
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read_fw FW_CFG_INITRD_SIZE // find end of initrd
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add %edi, %eax
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xor %es:0x22c, %eax // if it matches es:0x22c
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and $-4096, %eax // (apart from padding for page)
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jz load_kernel // then initrd is not at top
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// of memory
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/* pc.c placed the initrd at end of memory. Compute a better
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* initrd address based on e801 data.
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*/
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mov $0xe801, %ax
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xor %cx, %cx
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xor %dx, %dx
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int $0x15
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/* Output could be in AX/BX or CX/DX */
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or %cx, %cx
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jnz 1f
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or %dx, %dx
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jnz 1f
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mov %ax, %cx
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mov %bx, %dx
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1:
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or %dx, %dx
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jnz 2f
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addw $1024, %cx /* add 1 MB */
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movzwl %cx, %edi
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shll $10, %edi /* convert to bytes */
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jmp 3f
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2:
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addw $16777216 >> 16, %dx /* add 16 MB */
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movzwl %dx, %edi
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shll $16, %edi /* convert to bytes */
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3:
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read_fw FW_CFG_INITRD_SIZE
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subl %eax, %edi
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andl $-4096, %edi /* EDI = start of initrd */
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movl %edi, %es:0x218 /* put it in the header */
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load_kernel:
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/* We need to load the kernel into memory we can't access in 16 bit
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mode, so let's get into 32 bit mode, write the kernel and jump
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back again. */
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/* Reserve space on the stack for our GDT descriptor. */
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mov %esp, %ebp
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sub $16, %esp
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/* Now create the GDT descriptor */
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movw $((3 * 8) - 1), -16(%bp)
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mov %cs, %eax
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movzwl %ax, %eax
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shl $4, %eax
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addl $gdt, %eax
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movl %eax, -14(%bp)
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/* And load the GDT */
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data32 lgdt -16(%bp)
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mov %ebp, %esp
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/* Get us to protected mode now */
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mov $1, %eax
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mov %eax, %cr0
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/* So we can set ES to a 32-bit segment */
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mov $0x10, %eax
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mov %eax, %es
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/* We're now running in 16-bit CS, but 32-bit ES! */
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/* Load kernel and initrd */
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read_fw_blob_addr32_edi(FW_CFG_INITRD)
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read_fw_blob_addr32(FW_CFG_KERNEL)
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read_fw_blob_addr32(FW_CFG_CMDLINE)
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/* And now jump into Linux! */
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mov $0, %eax
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mov %eax, %cr0
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/* ES = CS */
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mov %cs, %ax
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mov %ax, %es
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jmp boot_kernel
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/* Variables */
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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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BOOT_ROM_END
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