diff options
Diffstat (limited to 'pc-bios/optionrom')
| -rw-r--r-- | pc-bios/optionrom/Makefile | 2 | ||||
| -rw-r--r-- | pc-bios/optionrom/linuxboot.S | 140 |
2 files changed, 141 insertions, 1 deletions
diff --git a/pc-bios/optionrom/Makefile b/pc-bios/optionrom/Makefile index b01a54ec2d..54db882491 100644 --- a/pc-bios/optionrom/Makefile +++ b/pc-bios/optionrom/Makefile @@ -13,7 +13,7 @@ CFLAGS += -I$(SRC_PATH) CFLAGS += $(call cc-option, $(CFLAGS), -fno-stack-protector) QEMU_CFLAGS = $(CFLAGS) -build-all: multiboot.bin +build-all: multiboot.bin linuxboot.bin %.img: %.o $(call quiet-command,$(LD) -Ttext 0 -e _start -s -o $@ $<," Building $(TARGET_DIR)$@") diff --git a/pc-bios/optionrom/linuxboot.S b/pc-bios/optionrom/linuxboot.S new file mode 100644 index 0000000000..b3c90e33ce --- /dev/null +++ b/pc-bios/optionrom/linuxboot.S @@ -0,0 +1,140 @@ +/* + * Linux Boot Option ROM + * + * 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. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + * + * Copyright Novell Inc, 2009 + * Authors: Alexander Graf <agraf@suse.de> + * + * Based on code in hw/pc.c. + */ + +#include "optionrom.h" + +BOOT_ROM_START + +run_linuxboot: + + cli + cld + + jmp copy_kernel +boot_kernel: + + read_fw FW_CFG_SETUP_ADDR + + mov %eax, %ebx + shr $4, %ebx + + /* All segments contain real_addr */ + mov %bx, %ds + mov %bx, %es + mov %bx, %fs + mov %bx, %gs + mov %bx, %ss + + /* CX = CS we want to jump to */ + add $0x20, %bx + mov %bx, %cx + + /* SP = cmdline_addr-real_addr-16 */ + read_fw FW_CFG_CMDLINE_ADDR + mov %eax, %ebx + read_fw FW_CFG_SETUP_ADDR + sub %eax, %ebx + sub $16, %ebx + mov %ebx, %esp + + /* Build indirect lret descriptor */ + pushw %cx /* CS */ + xor %ax, %ax + pushw %ax /* IP = 0 */ + + /* Clear registers */ + xor %eax, %eax + xor %ebx, %ebx + xor %ecx, %ecx + xor %edx, %edx + xor %edi, %edi + xor %ebp, %ebp + + /* Jump to Linux */ + lret + + +copy_kernel: + + /* We need to load the kernel into memory we can't access in 16 bit + mode, so let's get into 32 bit mode, write the kernel and jump + back again. */ + + /* Set DS to SS+SP - 0x10, so we can write our GDT descriptor there */ + mov %ss, %eax + shl $4, %eax + add %esp, %eax + sub $0x10, %eax + shr $4, %eax + + /* Now create the GDT descriptor */ + mov %cs, %eax + shl $4, %eax + movw $((3 * 8) - 1), %bx + movw %bx, %gs:0 + movl $gdt, %ebx + add %eax, %ebx + movl %ebx, %gs:2 + + /* And load the GDT */ + data32 lgdt %gs:0 + + /* Get us to protected mode now */ + mov $1, %eax + mov %eax, %cr0 + + /* So we can set DS to a 32-bit segment */ + mov $0x10, %eax + mov %eax, %ds + + /* We're now running in 16-bit CS, but 32-bit DS! */ + + /* Load kernel and initrd */ + read_fw_blob(FW_CFG_KERNEL) + read_fw_blob(FW_CFG_INITRD) + read_fw_blob(FW_CFG_CMDLINE) + read_fw_blob(FW_CFG_SETUP) + + /* And now jump into Linux! */ + mov $0, %eax + mov %eax, %cr0 + + /* DS = CS */ + mov %cs, %ax + mov %ax, %ds + + jmp boot_kernel + +/* Variables */ + +.align 4, 0 +gdt: + /* 0x00 */ +.byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 + + /* 0x08: code segment (base=0, limit=0xfffff, type=32bit code exec/read, DPL=0, 4k) */ +.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9a, 0xcf, 0x00 + + /* 0x10: data segment (base=0, limit=0xfffff, type=32bit data read/write, DPL=0, 4k) */ +.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0xcf, 0x00 + +BOOT_ROM_END |