diff options
Diffstat (limited to 'pc-bios/optionrom/multiboot.S')
| -rw-r--r-- | pc-bios/optionrom/multiboot.S | 232 |
1 files changed, 232 insertions, 0 deletions
diff --git a/pc-bios/optionrom/multiboot.S b/pc-bios/optionrom/multiboot.S new file mode 100644 index 000000000..181a4b03a --- /dev/null +++ b/pc-bios/optionrom/multiboot.S @@ -0,0 +1,232 @@ +/* + * Multiboot 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> + */ + +#include "optionrom.h" + +#define BOOT_ROM_PRODUCT "multiboot loader" + +#define MULTIBOOT_MAGIC 0x2badb002 + +#define GS_PROT_JUMP 0 +#define GS_GDT_DESC 6 + + +BOOT_ROM_START + +run_multiboot: + + cli + cld + + mov %cs, %eax + shl $0x4, %eax + + /* set up a long jump descriptor that is PC relative */ + + /* move stack memory to %gs */ + mov %ss, %ecx + shl $0x4, %ecx + mov %esp, %ebx + add %ebx, %ecx + sub $0x20, %ecx + sub $0x30, %esp + shr $0x4, %ecx + mov %cx, %gs + + /* now push the indirect jump descriptor there */ + mov (prot_jump), %ebx + add %eax, %ebx + movl %ebx, %gs:GS_PROT_JUMP + mov $8, %bx + movw %bx, %gs:GS_PROT_JUMP + 4 + + /* fix the gdt descriptor to be PC relative */ + movw (gdt_desc), %bx + movw %bx, %gs:GS_GDT_DESC + movl (gdt_desc+2), %ebx + add %eax, %ebx + movl %ebx, %gs:GS_GDT_DESC + 2 + + xor %eax, %eax + mov %eax, %es + + /* Read the bootinfo struct into RAM */ + read_fw_blob_dma(FW_CFG_INITRD) + + /* FS = bootinfo_struct */ + read_fw FW_CFG_INITRD_ADDR + shr $4, %eax + mov %ax, %fs + + /* Account for the EBDA in the multiboot structure's e801 + * map. + */ + int $0x12 + cwtl + movl %eax, %fs:4 + + /* ES = mmap_addr */ + mov %fs:48, %eax + shr $4, %eax + mov %ax, %es + + /* Initialize multiboot mmap structs using int 0x15(e820) */ + xor %ebx, %ebx + /* Start storing mmap data at %es:0 */ + xor %edi, %edi + +mmap_loop: + /* The multiboot entry size has offset -4, so leave some space */ + add $4, %di + /* entry size (mmap struct) & max buffer size (int15) */ + movl $20, %ecx + /* e820 */ + movl $0x0000e820, %eax + /* 'SMAP' magic */ + movl $0x534d4150, %edx + int $0x15 + +mmap_check_entry: + /* Error or last entry already done? */ + jb mmap_done + +mmap_store_entry: + /* store entry size */ + /* old as(1) doesn't like this insn so emit the bytes instead: + movl %ecx, %es:-4(%edi) + */ + .dc.b 0x26,0x67,0x66,0x89,0x4f,0xfc + + /* %edi += entry_size, store as mbs_mmap_length */ + add %ecx, %edi + movw %di, %fs:0x2c + + /* Continuation value 0 means last entry */ + test %ebx, %ebx + jnz mmap_loop + +mmap_done: + /* Calculate upper_mem field: The amount of memory between 1 MB and + the first upper memory hole. Get it from the mmap. */ + xor %di, %di + mov $0x100000, %edx +upper_mem_entry: + cmp %fs:0x2c, %di + je upper_mem_done + add $4, %di + + /* Skip if type != 1 */ + cmpl $1, %es:16(%di) + jne upper_mem_next + + /* Skip if > 4 GB */ + movl %es:4(%di), %eax + test %eax, %eax + jnz upper_mem_next + + /* Check for contiguous extension (base <= %edx < base + length) */ + movl %es:(%di), %eax + cmp %eax, %edx + jb upper_mem_next + addl %es:8(%di), %eax + cmp %eax, %edx + jae upper_mem_next + + /* If so, update %edx, and restart the search (mmap isn't ordered) */ + mov %eax, %edx + xor %di, %di + jmp upper_mem_entry + +upper_mem_next: + addl %es:-4(%di), %edi + jmp upper_mem_entry + +upper_mem_done: + sub $0x100000, %edx + shr $10, %edx + mov %edx, %fs:0x8 + +real_to_prot: + /* Load the GDT before going into protected mode */ +lgdt: + data32 lgdt %gs:GS_GDT_DESC + + /* get us to protected mode now */ + movl $1, %eax + movl %eax, %cr0 + + /* the LJMP sets CS for us and gets us to 32-bit */ +ljmp: + data32 ljmp *%gs:GS_PROT_JUMP + +prot_mode: +.code32 + + /* initialize all other segments */ + movl $0x10, %eax + movl %eax, %ss + movl %eax, %ds + movl %eax, %es + movl %eax, %fs + movl %eax, %gs + + /* Read the kernel and modules into RAM */ + read_fw_blob_dma(FW_CFG_KERNEL) + + /* Jump off to the kernel */ + read_fw FW_CFG_KERNEL_ENTRY + mov %eax, %ecx + + /* EBX contains a pointer to the bootinfo struct */ + read_fw FW_CFG_INITRD_ADDR + movl %eax, %ebx + + /* EAX has to contain the magic */ + movl $MULTIBOOT_MAGIC, %eax +ljmp2: + jmp *%ecx + +/* Variables */ +.align 4, 0 +prot_jump: .long prot_mode + .short 8 + +.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 + + /* 0x18: code segment (base=0, limit=0x0ffff, type=16bit code exec/read/conf, DPL=0, 1b) */ +.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9e, 0x00, 0x00 + + /* 0x20: data segment (base=0, limit=0x0ffff, type=16bit data read/write, DPL=0, 1b) */ +.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0x00, 0x00 + +gdt_desc: +.short (5 * 8) - 1 +.long gdt + +BOOT_ROM_END |