/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 1999,2000,2001,2002,2003,2005,2006,2007,2008,2009 Free Software Foundation, Inc.
*
* GRUB 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 3 of the License, or
* (at your option) any later version.
*
* GRUB 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 GRUB. If not, see .
*/
/*
* Note: These functions defined in this file may be called from C.
* Be careful of that you must not modify some registers. Quote
* from gcc-2.95.2/gcc/config/i386/i386.h:
1 for registers not available across function calls.
These must include the FIXED_REGISTERS and also any
registers that can be used without being saved.
The latter must include the registers where values are returned
and the register where structure-value addresses are passed.
Aside from that, you can include as many other registers as you like.
ax,dx,cx,bx,si,di,bp,sp,st,st1,st2,st3,st4,st5,st6,st7,arg
{ 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 }
*/
/*
* Note: GRUB is compiled with the options -mrtd and -mregparm=3.
* So the first three arguments are passed in %eax, %edx, and %ecx,
* respectively, and if a function has a fixed number of arguments
* and the number is greater than three, the function must return
* with "ret $N" where N is ((the number of arguments) - 3) * 4.
*/
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define ABS(x) ((x) - LOCAL (base) + GRUB_BOOT_MACHINE_KERNEL_ADDR + 0x200)
.file "startup.S"
.text
/* Tell GAS to generate 16-bit instructions so that this code works
in real mode. */
.code16
.globl start, _start
start:
_start:
LOCAL (base):
/*
* Guarantee that "main" is loaded at 0x0:0x8200.
*/
#ifdef __APPLE__
ljmp $0, $(ABS(LOCAL (codestart)) - 0x10000)
#else
ljmp $0, $ABS(LOCAL (codestart))
#endif
/*
* This is a special data area.
*/
. = _start + GRUB_KERNEL_I386_PC_TOTAL_MODULE_SIZE
VARIABLE(grub_total_module_size)
.long 0
. = _start + GRUB_KERNEL_I386_PC_COMPRESSED_SIZE
VARIABLE(grub_compressed_size)
.long 0
. = _start + GRUB_KERNEL_I386_PC_INSTALL_DOS_PART
VARIABLE(grub_install_dos_part)
.long 0xFFFFFFFF
. = _start + GRUB_KERNEL_I386_PC_INSTALL_BSD_PART
VARIABLE(grub_install_bsd_part)
.long 0xFFFFFFFF
. = _start + GRUB_KERNEL_I386_PC_REED_SOLOMON_REDUNDANCY
reed_solomon_redundancy:
.long 0
#ifdef APPLE_CC
bss_start:
.long 0
bss_end:
.long 0
#endif
/*
* This is the area for all of the special variables.
*/
VARIABLE(grub_boot_drive)
.byte 0
/* the real mode code continues... */
LOCAL (codestart):
cli /* we're not safe here! */
/* set up %ds, %ss, and %es */
xorw %ax, %ax
movw %ax, %ds
movw %ax, %ss
movw %ax, %es
/* set up the real mode/BIOS stack */
movl $GRUB_MEMORY_MACHINE_REAL_STACK, %ebp
movl %ebp, %esp
sti /* we're safe again */
/* save the boot drive */
ADDR32 movb %dl, EXT_C(grub_boot_drive)
/* reset disk system (%ah = 0) */
int $0x13
/* transition to protected mode */
DATA32 call real_to_prot
/* The ".code32" directive takes GAS out of 16-bit mode. */
.code32
incl %eax
call grub_gate_a20
movl EXT_C(grub_compressed_size), %edx
addl $(GRUB_KERNEL_MACHINE_RAW_SIZE - GRUB_KERNEL_I386_PC_NO_REED_SOLOMON_PART), %edx
movl reed_solomon_redundancy, %ecx
leal _start + GRUB_KERNEL_I386_PC_NO_REED_SOLOMON_PART, %eax
call EXT_C (grub_reed_solomon_recover)
jmp post_reed_solomon
#include
.text
. = _start + GRUB_KERNEL_I386_PC_NO_REED_SOLOMON_PART
/*
* Support for booting GRUB from a Multiboot boot loader (e.g. GRUB itself).
* This uses the a.out kludge to load raw binary to the area starting at 1MB,
* and relocates itself after loaded.
*/
.p2align 2 /* force 4-byte alignment */
multiboot_header:
/* magic */
.long 0x1BADB002
/* flags */
.long (1 << 16)
/* checksum */
.long -0x1BADB002 - (1 << 16)
/* header addr */
.long multiboot_header - _start + 0x100000 + 0x200
/* load addr */
.long 0x100000
/* load end addr */
.long 0
/* bss end addr */
.long 0
/* entry addr */
.long multiboot_entry - _start + 0x100000 + 0x200
multiboot_entry:
.code32
/* obtain the boot device */
movl 12(%ebx), %edx
movl $GRUB_MEMORY_MACHINE_PROT_STACK, %ebp
movl %ebp, %esp
/* relocate the code */
movl $(GRUB_KERNEL_MACHINE_RAW_SIZE + 0x200), %ecx
addl EXT_C(grub_compressed_size) - _start + 0x100000 + 0x200, %ecx
movl $0x100000, %esi
movl $GRUB_BOOT_MACHINE_KERNEL_ADDR, %edi
cld
rep
movsb
/* jump to the real address */
movl $multiboot_trampoline, %eax
jmp *%eax
multiboot_trampoline:
/* fill the boot information */
movl %edx, %eax
shrl $8, %eax
xorl %ebx, %ebx
cmpb $0xFF, %ah
je 1f
movb %ah, %bl
movl %ebx, EXT_C(grub_install_dos_part)
1:
cmpb $0xFF, %al
je 2f
movb %al, %bl
movl %ebx, EXT_C(grub_install_bsd_part)
2:
shrl $24, %edx
movb $0xFF, %dh
/* enter the usual booting */
call prot_to_real
jmp LOCAL (codestart)
post_reed_solomon:
#ifdef ENABLE_LZMA
movl $GRUB_MEMORY_MACHINE_DECOMPRESSION_ADDR, %edi
movl $(_start + GRUB_KERNEL_MACHINE_RAW_SIZE), %esi
pushl %edi
pushl %esi
movl $(BSS_START_SYMBOL - _start), %ecx
addl EXT_C(grub_total_module_size), %ecx
subl $GRUB_KERNEL_MACHINE_RAW_SIZE, %ecx
pushl %ecx
leal (%edi, %ecx), %ebx
call _LzmaDecodeA
/* _LzmaDecodeA clears DF, so no need to run cld */
popl %ecx
popl %edi
popl %esi
#endif
/* copy back the decompressed part (except the modules) */
subl EXT_C(grub_total_module_size), %ecx
rep
movsb
#if 0
/* copy modules before cleaning out the bss */
movl EXT_C(grub_total_module_size), %ecx
movl EXT_C(grub_kernel_image_size), %esi
addl %ecx, %esi
addl $_start, %esi
decl %esi
movl $END_SYMBOL, %edi
addl %ecx, %edi
decl %edi
std
rep
movsb
#endif
#ifdef APPLE_CC
/* clean out the bss */
bss_start_abs = ABS (bss_start)
bss_end_abs = ABS (bss_end)
movl bss_start_abs, %edi
/* compute the bss length */
movl bss_end_abs, %ecx
subl %edi, %ecx
#else
/* clean out the bss */
movl $BSS_START_SYMBOL, %edi
/* compute the bss length */
movl $END_SYMBOL, %ecx
subl %edi, %ecx
#endif
/* clean out */
xorl %eax, %eax
cld
rep
stosb
/*
* Call the start of main body of C code.
*/
call EXT_C(grub_main)
#include "../realmode.S"
/*
* grub_gate_a20(int on)
*
* Gate address-line 20 for high memory.
*
* This routine is probably overconservative in what it does, but so what?
*
* It also eats any keystrokes in the keyboard buffer. :-(
*/
grub_gate_a20:
movl %eax, %edx
gate_a20_test_current_state:
/* first of all, test if already in a good state */
call gate_a20_check_state
cmpb %al, %dl
jnz gate_a20_try_bios
ret
gate_a20_try_bios:
/* second, try a BIOS call */
pushl %ebp
call prot_to_real
.code16
movw $0x2400, %ax
testb %dl, %dl
jz 1f
incw %ax
1: int $0x15
DATA32 call real_to_prot
.code32
popl %ebp
call gate_a20_check_state
cmpb %al, %dl
jnz gate_a20_try_system_control_port_a
ret
gate_a20_try_system_control_port_a:
/*
* In macbook, the keyboard test would hang the machine, so we move
* this forward.
*/
/* fourth, try the system control port A */
inb $0x92
andb $(~0x03), %al
testb %dl, %dl
jz 6f
orb $0x02, %al
6: outb $0x92
/* When turning off Gate A20, do not check the state strictly,
because a failure is not fatal usually, and Gate A20 is always
on some modern machines. */
testb %dl, %dl
jz 7f
call gate_a20_check_state
cmpb %al, %dl
jnz gate_a20_try_keyboard_controller
7: ret
gate_a20_flush_keyboard_buffer:
inb $0x64
andb $0x02, %al
jnz gate_a20_flush_keyboard_buffer
2:
inb $0x64
andb $0x01, %al
jz 3f
inb $0x60
jmp 2b
3:
ret
gate_a20_try_keyboard_controller:
/* third, try the keyboard controller */
call gate_a20_flush_keyboard_buffer
movb $0xd1, %al
outb $0x64
4:
inb $0x64
andb $0x02, %al
jnz 4b
movb $0xdd, %al
testb %dl, %dl
jz 5f
orb $0x02, %al
5: outb $0x60
call gate_a20_flush_keyboard_buffer
/* output a dummy command (USB keyboard hack) */
movb $0xff, %al
outb $0x64
call gate_a20_flush_keyboard_buffer
call gate_a20_check_state
cmpb %al, %dl
/* everything failed, so restart from the beginning */
jnz gate_a20_try_bios
ret
gate_a20_check_state:
/* iterate the checking for a while */
movl $100, %ecx
1:
call 3f
cmpb %al, %dl
jz 2f
loop 1b
2:
ret
3:
pushl %ebx
pushl %ecx
xorl %eax, %eax
/* compare the byte at 0x8000 with that at 0x108000 */
movl $GRUB_BOOT_MACHINE_KERNEL_ADDR, %ebx
pushl %ebx
/* save the original byte in CL */
movb (%ebx), %cl
/* store the value at 0x108000 in AL */
addl $0x100000, %ebx
movb (%ebx), %al
/* try to set one less value at 0x8000 */
popl %ebx
movb %al, %ch
decb %ch
movb %ch, (%ebx)
/* serialize */
outb %al, $0x80
outb %al, $0x80
/* obtain the value at 0x108000 in CH */
pushl %ebx
addl $0x100000, %ebx
movb (%ebx), %ch
/* this result is 1 if A20 is on or 0 if it is off */
subb %ch, %al
xorb $1, %al
/* restore the original */
popl %ebx
movb %cl, (%ebx)
popl %ecx
popl %ebx
ret
#ifdef ENABLE_LZMA
#include "lzma_decode.S"
#endif
/*
* The code beyond this point is compressed. Assert that the uncompressed
* code fits GRUB_KERNEL_MACHINE_RAW_SIZE.
*/
. = _start + GRUB_KERNEL_MACHINE_RAW_SIZE
/*
* grub_exit()
*
* Exit the system.
*/
FUNCTION(grub_exit)
call prot_to_real
.code16
/* Tell the BIOS a boot failure. If this does not work, reboot. */
int $0x18
/* set 0x472 to 0x0000 for cold boot (0x1234 for warm boot) */
xorw %ax, %ax
movw $0x0472, %di
movw %ax, (%di)
ljmp $0xf000, $0xfff0
.code32
/*
* int grub_pxe_call (int func, void* data, grub_uint32_t pxe_rm_entry);
*/
FUNCTION(grub_pxe_call)
pushl %ebp
movl %esp, %ebp
pushl %esi
pushl %edi
pushl %ebx
movl %ecx, %ebx
movl %eax, %ecx
movl %edx, %eax
andl $0xF, %eax
shrl $4, %edx
shll $16, %edx
addl %eax, %edx
call prot_to_real
.code16
pushl %ebx
pushl %edx
pushw %cx
movw %sp, %bx
lcall *%ss:6(%bx)
cld
addw $10, %sp
movw %ax, %cx
DATA32 call real_to_prot
.code32
movzwl %cx, %eax
popl %ebx
popl %edi
popl %esi
popl %ebp
ret
#include "../int.S"