Linux0.01 源代码及注释
Bootsect.s ..........................................................................................................................................4
Head.s..............................................................................................................................................12
Setup.s.............................................................................................................................................21
Bitmap.c..........................................................................................................................................29
Block_dev.c.....................................................................................................................................34
Buffer.c............................................................................................................................................37
Char_dev.c ......................................................................................................................................51
Exec.c..............................................................................................................................................54
Fcntl.c..............................................................................................................................................68
File_dev.c........................................................................................................................................70
File_table.c......................................................................................................................................74
Inode.c.............................................................................................................................................74
Ioctl.c ..............................................................................................................................................86
Namei.c ...........................................................................................................................................88
Open.c ...........................................................................................................................................117
Pipe.c.............................................................................................................................................125
Read_write.c .................................................................................................................................129
Stat.c..............................................................................................................................................133
Super.c...........................................................................................................................................135
Truncate.c......................................................................................................................................146
Include...........................................................................................................................................148
Asm...............................................................................................................................................148
io.h ................................................................................................................................................148
Memory.h......................................................................................................................................149
Segment.h......................................................................................................................................150
System.h........................................................................................................................................153
Fs.h................................................................................................................................................155
Hdreg.h..........................................................................................................................................161
Head.h ...........................................................................................................................................163
Kernel.h.........................................................................................................................................164
Mm.h.............................................................................................................................................165
Sched.h..........................................................................................................................................165
Sys.h..............................................................................................................................................174
Tty.h ..............................................................................................................................................176
Config.h ........................................................................................................................................178
Stat.h .............................................................................................................................................180
Times.h..........................................................................................................................................182
Types.h..........................................................................................................................................183
Utsname.h .....................................................................................................................................184
Wait.h............................................................................................................................................184
Out.h..............................................................................................................................................185
Const.h ..........................................................................................................................................192
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Stype.h ..........................................................................................................................................193
Errno.h ..........................................................................................................................................194
Fcntl.h ...........................................................................................................................................196
Singnal.h .......................................................................................................................................198
Stdarg.h .........................................................................................................................................200
Stddef.h .........................................................................................................................................201
String.h..........................................................................................................................................202
Termios.h ......................................................................................................................................213
Time.h ...........................................................................................................................................221
Unistd.h.........................................................................................................................................222
Utime.h..........................................................................................................................................229
Main.c ...........................................................................................................................................229
Blk.h..............................................................................................................................................237
Floppy.c.........................................................................................................................................241
Hd.c...............................................................................................................................................258
Ll_rw_blk.c...................................................................................................................................269
Ramdisk.c......................................................................................................................................275
Makefile ........................................................................................................................................280
Console.c.......................................................................................................................................282
Keyboard.s ....................................................................................................................................306
Rs_io.s...........................................................................................................................................322
Serial.c ..........................................................................................................................................338
Tty_io.c .........................................................................................................................................340
Tty_ioctl.c .....................................................................................................................................354
Makefile ........................................................................................................................................361
Math_emulate.c.............................................................................................................................364
Makefile ........................................................................................................................................366
Asm.s ............................................................................................................................................368
Exit.c.............................................................................................................................................373
Fork.c ............................................................................................................................................379
Mktime.c .......................................................................................................................................384
Panic.c...........................................................................................................................................385
Printk.c..........................................................................................................................................386
Sched.c..........................................................................................................................................388
Signal.c..........................................................................................................................................402
Sys.c..............................................................................................................................................406
System_call.s ................................................................................................................................414
Vsprintf.c ......................................................................................................................................423
_exit.c............................................................................................................................................431
Close.c...........................................................................................................................................432
Ctype.c ..........................................................................................................................................432
Dup.c.............................................................................................................................................433
Execve.c........................................................................................................................................434
Malloc.c ........................................................................................................................................435
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Open.c ...........................................................................................................................................444
String.c..........................................................................................................................................445
Setsid.c..........................................................................................................................................445
Wait.c ............................................................................................................................................446
Write.c...........................................................................................................................................446
Makefile ........................................................................................................................................447
Memory.c ......................................................................................................................................450
page.s ............................................................................................................................................466
Makefile ........................................................................................................................................467
Build.c...........................................................................................................................................469
Makefile(总)...............................................................................................................................475
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Bootsect.s
!
! SYS_SIZE is the number of clicks (16 bytes) to be loaded.
! 0x3000 is 0x30000 bytes = 196kB, more than enough for current
! versions of linux ! SYS_SIZE 是要加载的节数(16 字节为 1 节)。0x3000 共为
1 2 3 4 5 6
0x7c00
0x0000
0x90000
0x10000
0xA0000
system 模块
代码执行位置线路
0x90200
! 0x30000 字节=192 kB(上面 Linus 估算错了),对于当前的版本空间已足够了。
!
SYSSIZE = 0x3000 ! 指编译连接后 system 模块的大小。参见列表 1.2 中第 92 的说明。
! 这里给出了一个最大默认值。
!
! bootsect.s (C) 1991 Linus Torvalds
!
! bootsect.s is loaded at 0x7c00 by the bios-startup routines, and moves
! iself out of the way to address 0x90000, and jumps there.
!
! It then loads 'setup' directly after itself (0x90200), and the system
! at 0x10000, using BIOS interrupts.
!
! NOTE! currently system is at most 8*65536 bytes long. This should be no
! problem, even in the future. I want to keep it simple. This 512 kB
! kernel size should be enough, especially as this doesn't contain the
! buffer cache as in minix
!
! The loader has been made as simple as possible, and continuos
! read errors will result in a unbreakable loop. Reboot by hand. It
! loads pretty fast by getting whole sectors at a time whenever possible.
!
! 以下是前面这些文字的翻译:
! bootsect.s (C) 1991 Linus Torvalds 版权所有
!
! bootsect.s 被 bios-启动子程序加载至 0x7c00 (31k)处,并将自己
! 移到了地址 0x90000 (576k)处,并跳转至那里。
!
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! 它然后使用 BIOS 中断将'setup'直接加载到自己的后面(0x90200)(576.5k),
! 并将 system 加载到地址 0x10000 处。
!
! 注意! 目前的内核系统最大长度限制为(8*65536)(512k)字节,即使是在
! 将来这也应该没有问题的。我想让它保持简单明了。这样 512k 的最大内核长度应该
! 足够了,尤其是这里没有象 minix 中一样包含缓冲区高速缓冲。
!
! 加载程序已经做的够简单了,所以持续的读出错将导致死循环。只能手工重启。
! 只要可能,通过一次取取所有的扇区,加载过程可以做的很快的。
.globl begtext, begdata, begbss, endtext, enddata, endbss ! 定义了 6 个全局标识符;
.text ! 文本段;
begtext:
.data ! 数据段;
begdata:
.bss ! 堆栈段;
begbss:
.text ! 文本段;
SETUPLEN = 4 ! nr of setup-sectors
! setup 程序的扇区数(setup-sectors)值;
BOOTSEG = 0x07c0 ! original address of boot-sector
! bootsect 的原始地址(是段地址,以下同);
INITSEG = 0x9000 ! we move boot here - out of the way
! 将 bootsect 移到这里 -- 避开;
SETUPSEG = 0x9020 ! setup starts here
! setup 程序从这里开始;
SYSSEG = 0x1000 ! system loaded at 0x10000 (65536).
! system 模块加载到 0x10000(64 kB)处;
ENDSEG = SYSSEG + SYSSIZE ! where to stop loading
! 停止加载的段地址;
! ROOT_DEV: 0x000 - same type of floppy as boot.
! 根文件系统设备使用与引导时同样的软驱设备;
! 0x301 - first partition on first drive etc
! 根文件系统设备在第一个硬盘的第一个分区上,等等;
ROOT_DEV = 0x306 ! 指定根文件系统设备是第 2 个硬盘的第 1 个分区。这是 Linux 老式
的硬盘命名
! 方式,具体值的含义如下:
! 设备号=主设备号*256 + 次设备号(也即 dev_no = (major<<8) + minor )
! (主设备号:1-内存,2-磁盘,3-硬盘,4-ttyx,5-tty,6-并行口,7-非命名管道)
! 0x300 - /dev/hd0 - 代表整个第 1 个硬盘;
! 0x301 - /dev/hd1 - 第 1 个盘的第 1 个分区;
! …
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! 0x304 - /dev/hd4 - 第 1 个盘的第 4 个分区;
! 0x305 - /dev/hd5 - 代表整个第 2 个硬盘盘;
! 0x306 - /dev/hd6 - 第 2 个盘的第 1 个分区;
! …
! 0x309 - /dev/hd9 - 第 2 个盘的第 4 个分区;
! 从 linux 内核 0.95 版后已经使用与现在相同的命名方法了。
entry start ! 告知连接程序,程序从 start 标号开始执行。
start: ! 47--56 行作用是将自身(bootsect)从目前段位置 0x07c0(31k)
! 移动到 0x9000(576k)处,共 256 字(512 字节),然后跳转到
! 移动后代码的 go 标号处,也即本程序的下一语句处。
mov ax,#BOOTSEG ! 将 ds 段寄存器置为 0x7C0;
mov ds,ax
mov ax,#INITSEG ! 将 es 段寄存器置为 0x9000;
mov es,ax
mov cx,#256 ! 移动计数值=256 字;
sub si,si ! 源地址 ds:si = 0x07C0:0x0000
sub di,di ! 目的地址 es:di = 0x9000:0x0000
rep ! 重复执行,直到 cx = 0
movw ! 移动 1 个字;
jmpi go,INITSEG ! 间接跳转。这里 INITSEG 指出跳转到的段地址。
go: mov ax,cs ! 将 ds、es 和 ss 都置成移动后代码所在的段处(0x9000)。
mov ds,ax !由于程序中有堆栈操作(push,pop,call),因此必须设置堆栈。
mov es,ax
! put stack at 0x9ff00. ! 将堆栈指针 sp 指向 0x9ff00(即 0x9000:0xff00)处
mov ss,ax
mov sp,#0xFF00 ! arbitrary value >>512
! 由于代码段移动过了,所以要重新设置堆栈段的位置。
! sp 只要指向远大于 512 偏移(即地址 0x90200)处
! 都可以。因为从 0x90200 地址开始处还要放置 setup 程序,
! 而此时 setup 程序大约为 4 个扇区,因此 sp 要指向大
! 于(0x200 + 0x200 * 4 + 堆栈大小)处。
! load the setup-sectors directly after the bootblock.
! Note that 'es' is already set up.
! 在 bootsect 程序块后紧根着加载 setup 模块的代码数据。
! 注意 es 已经设置好了。(在移动代码时 es 已经指向目的段地址处 0x9000)。
load_setup:
! 68--77 行的用途是利用 BIOS 中断 INT 0x13 将 setup 模块从磁盘第 2 个扇区
! 开始读到 0x90200 开始处,共读 4 个扇区。如果读出错,则复位驱动器,并
! 重试,没有退路。INT 0x13 的使用方法如下:
! 读扇区:
! ah = 0x02 - 读磁盘扇区到内存;al = 需要读出的扇区数量;
6
! ch = 磁道(柱面)号的低 8 位; cl = 开始扇区(0-5 位),磁道号高 2 位(6-7);
! dh = 磁头号; dl = 驱动器号(如果是硬盘则要置位 7);
! es:bx ??指向数据缓冲区; 如果出错则 CF 标志置位。
mov dx,#0x0000 ! drive 0, head 0
mov cx,#0x0002 ! sector 2, track 0
mov bx,#0x0200 ! address = 512, in INITSEG
mov ax,#0x0200+SETUPLEN ! service 2, nr of sectors
int 0x13 ! read it
jnc ok_load_setup ! ok - continue
mov dx,#0x0000
mov ax,#0x0000 ! reset the diskette
int 0x13
j load_setup
ok_load_setup:
! Get disk drive parameters, specifically nr of sectors/track
! 取磁盘驱动器的参数,特别是每道的扇区数量。
! 取磁盘驱动器参数 INT 0x13 调用格式和返回信息如下:
! ah = 0x08 dl = 驱动器号(如果是硬盘则要置位 7 为 1)。
! 返回信息:
! 如果出错则 CF 置位,并且 ah = 状态码。
! ah = 0, al = 0, bl = 驱动器类型(AT/PS2)
! ch = 最大磁道号的低 8 位,cl = 每磁道最大扇区数(位 0-5),最大磁道号高 2 位(位 6-7)
! dh = 最大磁头数, dl = 驱动器数量,
! es:di -?? 软驱磁盘参数表。
mov dl,#0x00
mov ax,#0x0800 ! AH=8 is get drive parameters
int 0x13
mov ch,#0x00
seg cs ! 表示下一条语句的操作数在 cs 段寄存器所指的段中。
mov sectors,cx ! 保存每磁道扇区数。
mov ax,#INITSEG
mov es,ax ! 因为上面取磁盘参数中断改掉了 es 的值,这里重新改回。
! Print some inane message ! 在显示一些信息('Loading system ...'回车换行,共 24 个字符)。
mov ah,#0x03 ! read cursor pos
xor bh,bh ! 读光标位置。
int 0x10
mov cx,#24 ! 共 24 个字符。
mov bx,#0x0007 ! page 0, attribute 7 (normal)
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mov bp,#msg1 ! 指向要显示的字符串。
mov ax,#0x1301 ! write string, move cursor
int 0x10 ! 写字符串并移动光标。
! ok, we've written the message, now
! we want to load the system (at 0x10000) ! 现在开始将 system 模块加载到 0x10000(64k)处。
mov ax,#SYSSEG
mov es,ax ! segment of 0x010000 ! es = 存放 system 的段地址。
call read_it ! 读磁盘上 system 模块,es 为输入参数。
call kill_motor ! 关闭驱动器马达,这样就可以知道驱动器的状态了。
! After that we check which root-device to use. If the device is
! defined (!= 0), nothing is done and the given device is used.
! Otherwise, either /dev/PS0 (2,28) or /dev/at0 (2,8), depending
! on the number of sectors that the BIOS reports currently.
! 此后,我们检查要使用哪个根文件系统设备(简称根设备)。如果已经指定了设备(!=0)
! 就直接使用给定的设备。否则就需要根据 BIOS 报告的每磁道扇区数来
! 确定到底使用/dev/PS0 (2,28) 还是 /dev/at0 (2,8)。
! 上面一行中两个设备文件的含义:
! 在 Linux 中软驱的主设备号是 2(参见第 43 行的注释),次设备号 = type*4 + nr,其中
! nr 为 0-3 分别对应软驱 A、B、C 或 D;type 是软驱的类型(2??1.2M 或 7??1.44M 等)。
! 因为 7*4 + 0 = 28,所以 /dev/PS0 (2,28)指的是 1.44M A 驱动器,其设备号是 0x021c
! 同理 /dev/at0 (2,8)指的是 1.2M A 驱动器,其设备号是 0x0208。
seg cs
mov ax,root_dev ! 将根设备号
cmp ax,#0
jne root_defined
seg cs
mov bx,sectors ! 取上面第 88 行保存的每磁道扇区数。如果 sectors=15
! 则说明是 1.2Mb 的驱动器;如果 sectors=18,则说明是
! 1.44Mb 软驱。因为是可引导的驱动器,所以肯定是 A 驱。
mov ax,#0x0208 ! /dev/ps0 - 1.2Mb
cmp bx,#15 ! 判断每磁道扇区数是否=15
je root_defined ! 如果等于,则 ax 中就是引导驱动器的设备号。
mov ax,#0x021c ! /dev/PS0 - 1.44Mb
cmp bx,#18
je root_defined
undef_root: ! 如果都不一样,则死循环(死机)。
jmp undef_root
root_defined:
seg cs
mov root_dev,ax ! 将检查过的设备号保存起来。
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