startup.s

最新的grub2源代码

/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 1999,2000,2001,2002,2003,2005 Free Software Foundation, Inc.
 *
 *  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, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */


/*
 * 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 if greater than three, the function must return
 *       with "ret $N" where N is ((the number of arguments) - 3) * 4.
 */

#include <config.h>
#include <grub/symbol.h>
#include <grub/boot.h>
#include <grub/machine/boot.h>
#include <grub/machine/memory.h>
#include <grub/machine/console.h>
#include <grub/machine/linux.h>
#include <grub/machine/kernel.h>
#include <grub/machine/multiboot.h>
		
#define ABS(x)	((x) - EXT_C(start) + 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:
	/*
	 *  Guarantee that "main" is loaded at 0x0:0x8200.
	 */
	ljmp $0, $ABS(codestart)

	/*
	 *  Compatibility version number
	 *
	 *  These MUST be at byte offset 6 and 7 of the executable
	 *  DO NOT MOVE !!!
	 */
	. = EXT_C(start) + 0x6
	.byte	GRUB_BOOT_VERSION_MAJOR, GRUB_BOOT_VERSION_MINOR

	/*
	 *  This is a special data area 8 bytes from the beginning.
	 */

	. = EXT_C(start) + 0x8

VARIABLE(grub_total_module_size)
	.long	0
VARIABLE(grub_kernel_image_size)
	.long	0
VARIABLE(grub_compressed_size)
	.long	0
VARIABLE(grub_install_dos_part)
	.long	0xFFFFFFFF
VARIABLE(grub_install_bsd_part)
	.long	0xFFFFFFFF
VARIABLE(grub_prefix)
	.string "/boot/grub"

	/*
	 *  Leave some breathing room for the prefix.
	 */

	. = EXT_C(start) + 0x50

/*
 * 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.
 */
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

	/* 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
	/* enter the usual booting */
	call	prot_to_real
	.code16
	
/* the real mode code continues... */
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 boot drive reference */
	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	EXT_C(grub_gate_a20)
	
	/* decompress the compressed part and put the result at 1MB */
	movl	$0x100000, %esi
	movl	$(START_SYMBOL + GRUB_KERNEL_MACHINE_RAW_SIZE), %edi

	pushl	%esi
	pushl	EXT_C(grub_compressed_size)
	pushl	%edi
	call	lzo1x_decompress
	addl	$12, %esp

	/* copy back the decompressed part */
	movl	%eax, %ecx
	cld
	rep
	movsb

	/* 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_SYMBOL, %esi
	decl	%esi
	movl	$END_SYMBOL, %edi
	addl	%ecx, %edi
	decl	%edi
	std
	rep
	movsb
	
	/* clean out the bss */
	movl	$BSS_START_SYMBOL, %edi

	/* compute the bss length */
	movl	$END_SYMBOL, %ecx
	subl	%edi, %ecx
			
	/* clean out */
	xorl	%eax, %eax
	cld
	rep
	stosb
	
	/*
	 *  Call the start of main body of C code.
	 */
	call EXT_C(grub_main)


/*
 *  This is the area for all of the special variables.
 */

	.p2align	2	/* force 4-byte alignment */

protstack:
	.long	GRUB_MEMORY_MACHINE_PROT_STACK

VARIABLE(grub_boot_drive)
	.long	0

VARIABLE(grub_start_addr)
	.long	START_SYMBOL

VARIABLE(grub_end_addr)
	.long	END_SYMBOL
	
VARIABLE(grub_apm_bios_info)
	.word	0	/* version */
	.word	0	/* cseg */
	.long	0	/* offset */
	.word	0	/* cseg_16 */
	.word	0	/* dseg_16 */
	.word	0	/* cseg_len */
	.word	0	/* cseg_16_len */
	.word	0	/* dseg_16_len */
	
/*
 * This is the Global Descriptor Table
 *
 *  An entry, a "Segment Descriptor", looks like this:
 *
 * 31          24         19   16                 7           0
 * ------------------------------------------------------------
 * |             | |B| |A|       | |   |1|0|E|W|A|            |
 * | BASE 31..24 |G|/|L|V| LIMIT |P|DPL|  TYPE   | BASE 23:16 |  4
 * |             | |D| |L| 19..16| |   |1|1|C|R|A|            |
 * ------------------------------------------------------------
 * |                             |                            |
 * |        BASE 15..0           |       LIMIT 15..0          |  0
 * |                             |                            |
 * ------------------------------------------------------------
 *
 *  Note the ordering of the data items is reversed from the above
 *  description.
 */

	.p2align	2	/* force 4-byte alignment */
gdt:
	.word	0, 0
	.byte	0, 0, 0, 0

	/* -- code segment --
	 * base = 0x00000000, limit = 0xFFFFF (4 KiB Granularity), present
	 * type = 32bit code execute/read, DPL = 0
	 */
	.word	0xFFFF, 0
	.byte	0, 0x9A, 0xCF, 0

	/* -- data segment --
	 * base = 0x00000000, limit 0xFFFFF (4 KiB Granularity), present
	 * type = 32 bit data read/write, DPL = 0 
	 */
	.word	0xFFFF, 0
	.byte	0, 0x92, 0xCF, 0

	/* -- 16 bit real mode CS --
	 * base = 0x00000000, limit 0x0FFFF (1 B Granularity), present
	 * type = 16 bit code execute/read only/conforming, DPL = 0
	 */
	.word	0xFFFF, 0
	.byte	0, 0x9E, 0, 0

	/* -- 16 bit real mode DS --
	 * base = 0x00000000, limit 0x0FFFF (1 B Granularity), present
	 * type = 16 bit data read/write, DPL = 0
	 */
	.word	0xFFFF, 0
	.byte	0, 0x92, 0, 0


/* this is the GDT descriptor */
gdtdesc:
	.word	0x27			/* limit */
	.long	gdt			/* addr */

	
/*
 *  These next two routines, "real_to_prot" and "prot_to_real" are structured
 *  in a very specific way.  Be very careful when changing them.
 *
 *  NOTE:  Use of either one messes up %eax and %ebp.
 */

real_to_prot:
	.code16
	cli

	/* load the GDT register */
	DATA32	ADDR32	lgdt	gdtdesc

	/* turn on protected mode */
	movl	%cr0, %eax
	orl	$GRUB_MEMORY_MACHINE_CR0_PE_ON, %eax
	movl	%eax, %cr0

	/* jump to relocation, flush prefetch queue, and reload %cs */
	DATA32	ljmp	$GRUB_MEMORY_MACHINE_PROT_MODE_CSEG, $protcseg

	.code32
protcseg:
	/* reload other segment registers */
	movw	$GRUB_MEMORY_MACHINE_PROT_MODE_DSEG, %ax
	movw	%ax, %ds
	movw	%ax, %es
	movw	%ax, %fs
	movw	%ax, %gs
	movw	%ax, %ss

	/* put the return address in a known safe location */
	movl	(%esp), %eax
	movl	%eax, GRUB_MEMORY_MACHINE_REAL_STACK

	/* get protected mode stack */
	movl	protstack, %eax
	movl	%eax, %esp
	movl	%eax, %ebp

	/* get return address onto the right stack */
	movl	GRUB_MEMORY_MACHINE_REAL_STACK, %eax
	movl	%eax, (%esp)

	/* zero %eax */
	xorl	%eax, %eax

	/* return on the old (or initialized) stack! */
	ret


prot_to_real:
	/* just in case, set GDT */
	lgdt	gdtdesc

	/* save the protected mode stack */
	movl	%esp, %eax
	movl	%eax, protstack

	/* get the return address */
	movl	(%esp), %eax
	movl	%eax, GRUB_MEMORY_MACHINE_REAL_STACK

	/* set up new stack */
	movl	$GRUB_MEMORY_MACHINE_REAL_STACK, %eax
	movl	%eax, %esp
	movl	%eax, %ebp

	/* set up segment limits */
	movw	$GRUB_MEMORY_MACHINE_PSEUDO_REAL_DSEG, %ax
	movw	%ax, %ds
	movw	%ax, %es
	movw	%ax, %fs
	movw	%ax, %gs
	movw	%ax, %ss

	/* this might be an extra step */
	/* jump to a 16 bit segment */
	ljmp	$GRUB_MEMORY_MACHINE_PSEUDO_REAL_CSEG, $tmpcseg

tmpcseg:
	.code16

	/* clear the PE bit of CR0 */
	movl	%cr0, %eax
	andl 	$(~GRUB_MEMORY_MACHINE_CR0_PE_ON), %eax
	movl	%eax, %cr0

	/* flush prefetch queue, reload %cs */
	DATA32	ljmp	$0, $realcseg

realcseg:
	/* we are in real mode now
	 * set up the real mode segment registers : DS, SS, ES
	 */
	/* zero %eax */
	xorl	%eax, %eax

	movw	%ax, %ds
	movw	%ax, %es
	movw	%ax, %fs
	movw	%ax, %gs
	movw	%ax, %ss

	/* restore interrupts */
	sti

	/* return on new stack! */
	DATA32	ret

	.code32


/*
 * 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.  :-(
 */

FUNCTION(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_keyboard_controller
	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
	jnz	gate_a20_try_system_control_port_a
	ret

gate_a20_try_system_control_port_a:
	/* 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
	/* everything failed, so restart from the beginning */
	jnz	gate_a20_try_bios
7:	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

#include "lzo1x.S"


/*
 *  This call is special...  it never returns...  in fact it should simply
 *  hang at this point!
 */

FUNCTION(grub_stop)
	call	prot_to_real

	/*
	 * This next part is sort of evil.  It takes advantage of the
	 * byte ordering on the x86 to work in either 16-bit or 32-bit
	 * mode, so think about it before changing it.
	 */

FUNCTION(grub_hard_stop)
	hlt
	jmp EXT_C(grub_hard_stop)


/*
 * grub_stop_floppy()
 *
 * Stop the floppy drive from spinning, so that other software is
 * jumped to with a known state.
 */
FUNCTION(grub_stop_floppy)
	movw	$0x3F2, %dx
	xorb	%al, %al
	outb	%al, %dx
	ret

/*
 * grub_reboot()
 *
 * Reboot the system. At the moment, rely on BIOS.
 */
FUNCTION(grub_reboot)
	call	prot_to_real
	.code16
	/* cold boot */
	movw	$0x0472, %di
	movw	%ax, (%di)
	ljmp	$0xFFFF, $0x0000
	.code32
	
/*
 * grub_halt(int no_apm)
 *
 * Halt the system, using APM if possible. If NO_APM is true, don't use
 * APM even if it is available.
 */
FUNCTION(grub_halt)
	/* see if zero */
	testl	%eax, %eax
	jnz	EXT_C(grub_stop)

	call	prot_to_real
	.code16
	
	/* detect APM */
	movw	$0x5300, %ax
	xorw	%bx, %bx
	int	$0x15
	jc	EXT_C(grub_hard_stop)
	/* don't check %bx for buggy BIOSes... */

	/* disconnect APM first */
	movw	$0x5304, %ax
	xorw	%bx, %bx
	int	$0x15

	/* connect APM */
	movw	$0x5301, %ax
	xorw	%bx, %bx
	int	$0x15
	jc	EXT_C(grub_hard_stop)

	/* set APM protocol level - 1.1 or bust. (this covers APM 1.2 also) */
	movw	$0x530E, %ax
	xorw	%bx, %bx
	movw	$0x0101, %cx
	int	$0x15
	jc	EXT_C(grub_hard_stop)
	
	/* set the power state to off */
	movw	$0x5307, %ax
	movw	$1, %bx
	movw	$3, %cx
	int	$0x15

	/* shouldn't reach here */
	jmp	EXT_C(grub_hard_stop)
	.code32
	
	
/*
 *  void grub_chainloader_real_boot (int drive, void *part_addr)
 *
 *  This starts another boot loader.
 */

FUNCTION(grub_chainloader_real_boot)
	pushl	%edx
	pushl	%eax

	call	EXT_C(grub_dl_unload_all)

	/* set up to pass boot drive */
	popl	%edx

	/* ESI must point to a partition table entry */
	popl	%esi

	/* Turn off Gate A20 */
	xorl	%eax, %eax
	call	EXT_C(grub_gate_a20)
	
	call	prot_to_real
	.code16
	ljmp	$0, $GRUB_MEMORY_MACHINE_BOOT_LOADER_ADDR
	.code32


/*
 * void grub_linux_boot_zimage (void)
 */
VARIABLE(grub_linux_prot_size)
	.long	0