**1.在include/unistd.h中添加系统调用号** ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554347358592.png-wm) **2.在kernel/system_call.s中修改系统调用总数** ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554347528925.png-wm) **3.在include/linux/sys.h中添加内核函数的声明，填表sys_call_table** ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554347942334.png-wm) ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554347953521.png-wm) **4.在kernel中新建who.c,实现内核函数** ``` #include #include #include #include #include #include #include struct str{ char stri[24]; int length; }myname; int sys_iam(const char* name){ int len = 0; while(get_fs_byte(name + len) != '\0'){ len++; } if(len > 23){ //printk("iam is returning ..."); //printk("now in iam, errno = %d ...\n", errno); return -EINVAL;//注意 } int i = 0; for(; i < len; i++){ myname.stri[i] = get_fs_byte(name + i); } myname.stri[len] = '\0'; myname.length = len; return myname.length; } **注意，如果用getfsbyte直接写=name[i]，会造成segment fault** int sys_whoami(char *name, unsigned int size){ if(size < myname.length){ //printk("whoami is returning ..."); //printk("now in whoami, errno = %d ...\n", errno); return -EINVAL;// } int i = 0; for(; i < myname.length; i++){ put_fs_byte(myname.stri[i], name + i); } put_fs_byte('\0', name + i); return myname.length; } ``` **5.修改who.c同目录下的makefile如实验文档， make all** **6.编写测试程序** ######1）挂载hdc，在hdc/usr/root目录下编辑测试程序iam.c和whoami.c ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554348734411.png-wm) ######2）testlab2.sh中，测试程序需要的格式如图 ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554350404069.png-wm) ######可以发现要求执行iam的同时输入 ``` //iam.c #define __LIBRARY__//注意library前后是两个下划线。。 #include #include "unistd.h" _syscall1(int, iam, const char*, name);//这里的类型是指针。。。 int main(int argc, char* argv[]){ iam(argv[1]); return 0; } ``` ``` //whoami.c #include #include _syscall2(int, whoami, char*, name, unsigned int, size); int main(){ char name[100]; whoami(name, 23); printf("%s", name); return 0; } ``` **7.修改挂载hdc内的unistd** ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554349325101.png-wm) ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554349370744.png-wm) ######系统启动之前一定先卸载hdc，系统启动时不能挂在磁盘，否则会造成系统损坏！！！ ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554349467982.png-wm) **8.编译并测试编写的程序** ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554349589939.png-wm) **9.运行脚本程序** ######1)关闭bochs（之前记得sync）->挂在hdc_->把/home/teacher/下的两个test文件复制到hdc/usr/root下->卸载hdc->启动bochs->增加执行权限->运行脚本程序 ######2)测试结果：![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554350034641.png-wm) **10.运行测试程序** ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554364192297.png-wm) **注意：在unistd中可以看到，API会把内核函数的返回值的相反数赋给errno，再返回-1** ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554364690342.png-wm) **所以sys_iam和sys_whoami不符合条件只需要返回-EINVAL，API会返回-1。如果在内核函数中写errno = EINVAL， return -1，API会置errno = 1，如图** ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/962312/1554364637044.png-wm) **11.实验报告** ######1)unistd.h中最多到syscall3，即只能展开三个参数，扩大限制需要编写syscall4， 5.。。 ######2）添加系统调用foo步骤：同上

“操作系统原理与实践”实验报告