x01.os.21: print "Loading..."

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先把目标设低点，开机进入后，在屏幕上打印“Loading..."即可。由于要在 bochs 中运行，首先就是安装 bochs。Oldlinux 中有相关资源，可自行下载。winxp 和 linux 的配置脚本如下：

# for windows bochs config

megs : 32

romimage: file=$BXSHARE/BIOS-bochs-latest
vgaromimage: file=$BXSHARE/VGABIOS-lgpl-latest

floppya: 1_44="a.img", status=inserted
floppyb: 1_44="b.img", status=inserted
ata0-master: type=disk, path="c.img", cylinders=365, heads=16, spt=63

boot: a

mouse: enabled=0

# for linux bochs config

display_library : sdl
megs : 32

romimage : file=/usr/share/bochs/BIOS-bochs-latest
vgaromimage : file=/usr/share/vgabios/vgabios.bin

floppya: 1_44="a.img", status=inserted
floppyb: 1_44="b.img", status=inserted
ata0-master: type=disk, path="c.img", cylinders=365, heads=16, spt=63

boot : a

mouse : enabled=0
keyboard_mapping : enabled=1, map=/usr/share/bochs/keymaps/sdl-pc-us.map 

当然，这只是作为参考。如是 winxp，建议直接在 bochs-sls1.0 中编译，用 dd 写入 /dev/fd1, 即 b.img；如是 ubuntu，我使用 eclipse，贪图智能提示而已，本质并无区别。github 中的代码为 Ubuntu 系统。由于要求简单，代码自然也简单，分别为 makefile, boot/bootsect.s, tools/build.c 如下：

# makefile

AS86 = as86 -0 -a 
LD86 = ld86 -0

AS = as 
LD = ld 
LDFLAGS = -s -x -M
CC = gcc
CFLAGS = -Wall -O -fstrength-reduce -fomit-frame-pointer -nostdinc -Iinclude
CPP = gcc -E -nostdinc -Iinclude

ROOT_DEV = /dev/hd1

.c.s:
    $(CC) $(CFLAGS) -S -o $*.s $<
.s.o:
    $(AS) -c -o $*.o $<
.c.o:
    $(CC) $(CFLAGS) -c -o $*.o $<
    
Image: boot/bootsect tools/build
    tools/build boot/bootsect > Image
    sync
    
boot/bootsect: boot/bootsect.s 
    $(AS86) -o boot/bootsect.o boot/bootsect.s 
    $(LD86) -o boot/bootsect boot/bootsect.o
    
tools/build: tools/build.c
    gcc -o tools/build tools/build.c

! boot/bootsect.s

.text

entry start
start:
    mov ax, #0x07c0
    mov ds, ax
    mov es, ax 
    mov ss, ax 
    mov sp, #0xff00
    
    mov cx, #18
    mov bx, #0x000c
    mov bp, #msg
    mov ax, #0x1301
    int 0x10 
    
die:
    jmp die 
    
msg:
    .byte 13,10,13,10
    .ascii "Loading..."
    .byte 13,10,13,10
    
    .org 510
    .word 0xaa55
    

/*
 * tools/build.c 
 */
 
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <linux/fs.h>
#include <unistd.h>
#include <fcntl.h>

#define MINIX_HEADER        32
#define GCC_HEADER            1024
#define SYS_SIZE            0x2000
#define DEFAULT_MAJOR_ROOT    3 
#define DEFAULT_MINOR_ROOT    1 
#define SETUP_SECTS            4

void die(char* str)
{
    fprintf(stderr, "%s\n", str);
    exit(1);
}

int main(int argc, char** argv)
{
    int i, id, c;
    char buf[1024];
    char major_root, minor_root;
    
    if (argc == 5) {
    } else {
        major_root = DEFAULT_MAJOR_ROOT;
        minor_root = DEFAULT_MINOR_ROOT;
    }
    fprintf(stderr, "Root device is (%d, %d)\n", major_root, minor_root);
    for (i = 0; i < sizeof buf; i++)
        buf[i] = 0;
        
    if ((id = open(argv[1], O_RDONLY, 0)) < 0)
        die("Unable open bootsect");
    if (read(id, buf, MINIX_HEADER) != MINIX_HEADER)
        die("Unable read Minix header");
    i = read(id, buf, sizeof buf);
    fprintf(stderr, "bootsect is %d bytes.\n", i);
    buf[508] = (char)major_root;
    buf[509] = (char)minor_root;
    if ((*(unsigned short*)(buf + 510)) != 0xaa55)
        die("boot hasn't '0xaa55' flag.");
    i = write(1, buf, 512);
    if (i != 512)
        die("write call failed.");
    close(id);
    
    return 0;
}

源代码：https://github.com/chinax01/Lab

在 ubuntu 中进入目录后运行如下命令即可：

make

make editcopy

bochs