2005-07-17 Yoshinori Okuji <okuji@enbug.org>
* conf/i386-pc.rmk (pxeboot_img_LDFLAGS): The text address should be 0x7C00 instead of 0x8000. * boot/i386/pc/pxeboot.S: Rewritten. * kern/i386/pc/startup.S (gate_a20_try_bios): No need to specify EXT_C. (gate_a20_check_state): Read a byte from 0x108000. Invert the result.
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5 changed files with 44 additions and 35 deletions
12
ChangeLog
12
ChangeLog
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@ -1,3 +1,15 @@
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2005-07-17 Yoshinori Okuji <okuji@enbug.org>
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* conf/i386-pc.rmk (pxeboot_img_LDFLAGS): The text address should
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be 0x7C00 instead of 0x8000.
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* boot/i386/pc/pxeboot.S: Rewritten.
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* kern/i386/pc/startup.S (gate_a20_try_bios): No need to specify
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EXT_C.
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(gate_a20_check_state): Read a byte from 0x108000. Invert the
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result.
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2005-07-16 Yoshinori K. Okuji <okuji@enbug.org>
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* kern/i386/pc/startup.S (grub_gate_a20): Rewritten for
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@ -1,7 +1,6 @@
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/* -*-Asm-*- */
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/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 1999,2000,2001,2002,2004 Free Software Foundation, Inc.
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* Copyright (C) 2000,2005 Free Software Foundation, Inc.
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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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@ -18,26 +17,20 @@
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <grub/boot.h>
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#include <grub/machine/boot.h>
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/*
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* defines for the code go here
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*/
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.file "pxeboot.S"
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.text
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/* Tell GAS to generate 16-bit instructions so that this code works
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in real mode. */
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/* Start with the prehistoric environment... */
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.code16
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/* Let's go */
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.globl _start; _start:
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/*
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* _start is loaded at 0x7c00 and is jumped to with CS:IP 0:0x7c00
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*/
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/* Jump to the real world */
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ljmp $0, $0x8200
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. = 0x8000 - 0x7C00 -1
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/* This region is a junk. Do you say that this is wasteful?
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But I like that the memory layout of the body is consistent
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among different kernels rather than scamping just for 1.5KB. */
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. = _start + 0x8200 - 0x7C00 - 0x200 - 1
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.byte 0
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@ -48,7 +48,7 @@ pxeboot_img-boot_i386_pc_pxeboot.d: boot/i386/pc/pxeboot.S
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-include pxeboot_img-boot_i386_pc_pxeboot.d
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pxeboot_img_ASFLAGS = $(COMMON_ASFLAGS)
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pxeboot_img_LDFLAGS = -nostdlib -Wl,-N,-Ttext,8000
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pxeboot_img_LDFLAGS = -nostdlib -Wl,-N,-Ttext,7C00
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# For diskboot.img.
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diskboot_img_SOURCES = boot/i386/pc/diskboot.S
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@ -14,7 +14,7 @@ boot_img_LDFLAGS = -nostdlib -Wl,-N,-Ttext,7C00
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# For pxeboot.img
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pxeboot_img_SOURCES = boot/i386/pc/pxeboot.S
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pxeboot_img_ASFLAGS = $(COMMON_ASFLAGS)
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pxeboot_img_LDFLAGS = -nostdlib -Wl,-N,-Ttext,8000
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pxeboot_img_LDFLAGS = -nostdlib -Wl,-N,-Ttext,7C00
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# For diskboot.img.
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diskboot_img_SOURCES = boot/i386/pc/diskboot.S
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@ -396,7 +396,7 @@ gate_a20_test_current_state:
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gate_a20_try_bios:
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/* second, try a BIOS call */
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pushl %ebp
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call EXT_C(prot_to_real)
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call prot_to_real
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.code16
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movw $0x2400, %ax
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@ -405,7 +405,7 @@ gate_a20_try_bios:
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incw %ax
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1: int $0x15
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DATA32 call EXT_C(real_to_prot)
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DATA32 call real_to_prot
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.code32
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popl %ebp
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@ -484,27 +484,31 @@ gate_a20_check_state:
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pushl %ebx
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pushl %ecx
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xorl %eax, %eax
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/* compare the byte at 0x2000 with that at 0x102000 */
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/* compare the byte at 0x8000 with that at 0x108000 */
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movl $GRUB_BOOT_MACHINE_KERNEL_ADDR, %ebx
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pushl %ebx
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/* save the original byte in CL */
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movb (%ebx), %cl
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/* store the value at 0x102000 in AL */
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/* store the value at 0x108000 in AL */
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addl $0x100000, %ebx
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movb (%ebx), %al
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/* try to set one less value at 0x2000 */
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/* try to set one less value at 0x8000 */
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popl %ebx
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movb %al, %ch
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decb %ch
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movb %ch, (%ebx)
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/* serialize */
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outb $0x80
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outb $0x80
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/* store the value at 0x2000 in CH */
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outb %al, $0x80
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outb %al, $0x80
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/* obtain the value at 0x108000 in CH */
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pushl %ebx
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addl $0x100000, %ebx
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movb (%ebx), %ch
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/* this result is 1 if A20 is on or 0 if it is off */
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subb %ch, %al
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xorb $1, %al
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/* restore the original */
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popl %ebx
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movb %cl, (%ebx)
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popl %ecx
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popl %ebx
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