MIT XV6 - 1.1 Lab: Xv6 and Unix utilities - sleep

接上文 MIT XV6 - 1. 环境准备

实验正文

打开实验链接 Lab: Xv6 and Unix utilities ,可以看到他一共有6个小实验(头大，让我们争取日拱一卒吧...)：

Boot xv6 (easy)
sleep (easy)
pingpong (easy)
primes (moderate)/(hard)
find (moderate)
xargs (moderate)

Boot xv6

第一个直接跳过吧，其实上一篇文章已经做过了，就是

启动

bash 复制代码

make queue

输入ls

bash 复制代码

ls

然后就是两个额外的小技巧

xv6 has no ps command, but, if you type Ctrl-p, the kernel will print information about each process. If you try it now, you'll see two lines: one for init, and one for sh.
To quit qemu type: Ctrl-a x (press Ctrl and a at the same time, followed by x).

sleep

Implement a user-level sleep program for xv6, along the lines of the UNIX sleep command. Your sleep should pause for a user-specified number of ticks. A tick is a notion of time defined by the xv6 kernel, namely the time between two interrupts from the timer chip. Your solution should be in the file user/sleep.c.

实验要求第一条，上来就让你读教材。。我反正老老实实去读了。。虽然读完发现他让我读第一章，我读的是序章？？？我建议有兴趣你也跟着去读吧 xv6 book

Before you start coding, read Chapter 1 of the xv6 book.

然后就是其他要求或者说步骤吧

Put your code in user/sleep.c. Look at some of the other programs in user/ (e.g., user/echo.c, user/grep.c, and user/rm.c) to see how command-line arguments are passed to a program.
Add your sleep program to UPROGS in Makefile; once you've done that, make qemu will compile your program and you'll be able to run it from the xv6 shell.
If the user forgets to pass an argument, sleep should print an error message.
The command-line argument is passed as a string; you can convert it to an integer using atoi (see user/ulib.c).
Use the system call sleep.
See kernel/sysproc.c for the xv6 kernel code that implements the sleep system call (look for sys_sleep), user/user.h for the C definition of sleep callable from a user program, and user/usys.S for the assembler code that jumps from user code into the kernel for sleep.
sleep's main should call exit(0) when it is done.
Look at Kernighan and Ritchie's book The C programming language (second edition) (K&R) to learn about C.

我就不做翻译了直接上修改

新建 user/sleep.c

c 复制代码

#include "kernel/types.h"
#include "user/user.h" // for sleep and exit

int main(int argc, char *argv[])
{
    if (argc != 2)
    {
        fprintf(2, "Usage: sleep <seconds>\n");
        exit(1);
    }

    if (sleep(atoi(argv[1])) != 0)
    {
        fprintf(2, "sleep: failed to sleep\n");
        exit(1);
    }

    exit(0);
}

查看他的 user/user.h 可以看到预定义了一些系统调用方法和libc的函数，还是很熟悉的看起来，但是看到他的commit记录，让我有点郁闷

修改Makefile支持编译sleep.c

makefile 复制代码

UPROGS=\
	$U/_cat\
	$U/_echo\
	$U/_forktest\
	$U/_grep\
	$U/_init\
	$U/_kill\
	$U/_ln\
	$U/_ls\
	$U/_mkdir\
	$U/_rm\
	$U/_sh\
	$U/_stressfs\
	$U/_usertests\
	$U/_grind\
	$U/_wc\
	$U/_zombie\
	$U/_sleep\

重新编译～

bash 复制代码

make claen;make qemu

查看我们的sleep可执行文件

bash 复制代码

xv6 kernel is booting

hart 2 starting
hart 1 starting
init: starting sh
$ ls
.              1 1 1024
..             1 1 1024
README         2 2 2305
xargstest.sh   2 3 93
cat            2 4 33520
echo           2 5 32336
forktest       2 6 16136
grep           2 7 36960
init           2 8 32792
kill           2 9 32280
ln             2 10 32088
ls             2 11 35616
mkdir          2 12 32336
rm             2 13 32328
sh             2 14 55112
stressfs       2 15 33200
usertests      2 16 183160
grind          2 17 48544
wc             2 18 34424
zombie         2 19 31680
sleep          2 20 32160
console        3 21 0
$

果然有了，至于为什么编译后就自动挂载到了系统中，引用jyy一句话"计算机的世界里没有魔法，冤有头债有主"，后面的课程中一定可以发现他是如何实现的

运行 sleep 10

bash 复制代码

sleep 10

运行测试用例 ./grade-lab-util sleep

bash 复制代码

./grade-lab-util sleep
make: `kernel/kernel' is up to date.
== Test sleep, no arguments == sleep, no arguments: OK (0.6s) 
== Test sleep, returns == sleep, returns: OK (0.8s) 
== Test sleep, makes syscall == sleep, makes syscall: OK (0.9s)

虽然通过了他的测试用例，但不能称为一个好的应用，至少我在xv6系统控制台中随便输入点或者加点管道、重定向什么的，就gg了

代码已提交
xv6-learn