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sys修改1.c

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+/*
+ *  linux/kernel/sys.c
+ *
+ *  (C) 1991  Linus Torvalds
+ */
+
+#include <errno.h>
+
+#include <linux/sched.h>	//调度程序头文件。定义了任务结构task_struct,任务0的数据,
+							//还有一些有关描述符参数设置和获取的嵌入式汇编函数宏语言
+#include <linux/tty.h>
+#include <linux/kernel.h>	//内核头文件
+#include <asm/segment.h>
+#include <sys/times.h>
+#include <sys/utsname.h>	//系统名称结构头文件
+
+int sys_ftime()
+{
+	return -ENOSYS;
+}
+
+int sys_break()
+{
+	return -ENOSYS;
+}
+
+int sys_ptrace()
+{
+	return -ENOSYS;
+}
+
+int sys_stty()
+{
+	return -ENOSYS;
+}
+
+int sys_gtty()
+{
+	return -ENOSYS;
+}
+
+int sys_rename()
+{
+	return -ENOSYS;
+}
+
+int sys_prof()
+{
+	return -ENOSYS;
+}
+
+int sys_setregid(int rgid, int egid)
+{
+	if (rgid>0) {
+		if ((current->gid == rgid) || 
+		    suser())
+			current->gid = rgid;
+		else
+			return(-EPERM);
+	}
+	if (egid>0) {
+		if ((current->gid == egid) ||
+		    (current->egid == egid) ||
+		    suser()) {
+			current->egid = egid;
+			current->sgid = egid;
+		} else
+			return(-EPERM);
+	}
+	return 0;
+}
+//设置进程组号
+int sys_setgid(int gid)
+{
+/*	return(sys_setregid(gid, gid)); */
+	if (suser())
+		current->gid = current->egid = current->sgid = gid;
+	else if ((gid == current->gid) || (gid == current->sgid))
+		current->egid = gid;
+	else
+		return -EPERM;
+	return 0;
+}
+
+int sys_acct()
+{
+	return -ENOSYS;
+}
+
+int sys_phys()
+{
+	return -ENOSYS;
+}
+
+int sys_lock()
+{
+	return -ENOSYS;
+}
+
+int sys_mpx()
+{
+	return -ENOSYS;
+}
+
+int sys_ulimit()
+{
+	return -ENOSYS;
+}
+//返回从1970年1月1号 开始记时的时间值(s)
+int sys_time(long * tloc)
+{
+	int i;
+
+	i = CURRENT_TIME;
+	if (tloc) {
+		verify_area(tloc,4);
+		put_fs_long(i,(unsigned long *)tloc);	//把时间值存储到用户空间
+		//段寄存器fs被默认地指向用户数据空间，因此此函数可利用fs段寄存器来访问用户空间中的值
+	}
+	return i;
+}
+
+/*
+ * Unprivileged users may change the real user id to the effective uid
+ * or vice versa.
+ */
+int sys_setreuid(int ruid, int euid)
+{
+	int old_ruid = current->uid;
+	
+	if (ruid>0) {
+		if ((current->euid==ruid) ||
+                    (old_ruid == ruid) ||
+		    suser())
+			current->uid = ruid;
+		else
+			return(-EPERM);
+	}
+	if (euid>0) {
+		if ((old_ruid == euid) ||
+                    (current->euid == euid) ||
+		    suser()) {
+			current->euid = euid;
+			current->suid = euid;
+		} else {
+			current->uid = old_ruid;
+			return(-EPERM);
+		}
+	}
+	return 0;
+}
+
+int sys_setuid(int uid)
+{
+/*	return(sys_setreuid(uid, uid)); */
+	if (suser())
+		current->uid = current->euid = current->suid = uid;
+	else if ((uid == current->uid) || (uid == current->suid))
+		current->euid = uid;
+	else
+		return -EPERM;
+	return(0);
+}
+
+int sys_stime(long * tptr)
+{
+	if (!suser())
+		return -EPERM;
+	startup_time = get_fs_long((unsigned long *)tptr) - jiffies/HZ;
+	return 0;
+}
+//获取当前任务运行时间统计值
+int sys_times(struct tms * tbuf)
+{
+	if (tbuf) {
+		verify_area(tbuf,sizeof *tbuf);
+		put_fs_long(current->utime,(unsigned long *)&tbuf->tms_utime);
+		put_fs_long(current->stime,(unsigned long *)&tbuf->tms_stime);
+		put_fs_long(current->cutime,(unsigned long *)&tbuf->tms_cutime);
+		put_fs_long(current->cstime,(unsigned long *)&tbuf->tms_cstime);
+	}
+	return jiffies;
+}
+//设置程序在内存中的末端位置
+int sys_brk(unsigned long end_data_seg)
+{
+	//如果参数值大于代码结尾，并且小于（堆栈-16kb），则设置新数据段结尾值
+	if (end_data_seg >= current->end_code &&
+	    end_data_seg < current->start_stack - 16384)
+		current->brk = end_data_seg;
+	return current->brk;
+}
+
+/*
+ * This needs some heave checking ...
+ * I just haven't get the stomach for it. I also don't fully
+ * understand sessions/pgrp etc. Let somebody who does explain it.
+ */
+int sys_setpgid(int pid, int pgid)
+{
+	int i;
+
+	if (!pid)
+		pid = current->pid;
+	if (!pgid)
+		pgid = current->pid;
+	for (i=0 ; i<NR_TASKS ; i++)
+		if (task[i] && task[i]->pid==pid) {
+			if (task[i]->leader)
+				return -EPERM;
+			if (task[i]->session != current->session)
+				return -EPERM;
+			task[i]->pgrp = pgid;
+			return 0;
+		}
+	return -ESRCH;
+}
+
+int sys_getpgrp(void)
+{
+	return current->pgrp;
+}
+
+int sys_setsid(void)
+{
+	if (current->leader && !suser())
+		return -EPERM;
+	current->leader = 1;
+	current->session = current->pgrp = current->pid;
+	current->tty = -1;
+	return current->pgrp;
+}
+
+int sys_getgroups()
+{
+	return -ENOSYS;
+}
+
+int sys_setgroups()
+{
+	return -ENOSYS;
+}
+
+int sys_uname(struct utsname * name)
+{
+	static struct utsname thisname = {
+		"linux .0","nodename","release ","version ","machine "
+	};
+	int i;
+
+	if (!name) return -ERROR;
+	verify_area(name,sizeof *name);
+	for(i=0;i<sizeof *name;i++)
+		put_fs_byte(((char *) &thisname)[i],i+(char *) name);
+	return 0;
+}
+
+int sys_sethostname()
+{
+	return -ENOSYS;
+}
+
+int sys_getrlimit()
+{
+	return -ENOSYS;
+}
+
+int sys_setrlimit()
+{
+	return -ENOSYS;
+}
+
+int sys_getrusage()
+{
+	return -ENOSYS;
+}
+
+int sys_gettimeofday()
+{
+	return -ENOSYS;
+}
+
+int sys_settimeofday()
+{
+	return -ENOSYS;
+}
+
+
+int sys_umask(int mask)
+{
+	int old = current->umask;
+
+	current->umask = mask & 0777;
+	return (old);
+}
+
+int sys_pipe2(void){
+	return 0;
+}
+
+int sys_sleep(unsigned int seconds){
+	sys_signal(SIGALRM,SIG_IGN);
+	sys_alarm(seconds);
+	sys_pause();
+	return 0;
+}
+
+int sys_execve2(){
+	return 0;
+}
+//获取目录的目录项
+int sys_getdents(int fd,struct linux_dirent *dirp,unsigned int count){
+	return 0;
+}
+
+int sys_getcwd(char* buf,size_t size){
+    //char cwd[BUF_MAX];
+    if(buf == NULL){
+        buf = get_free_page();
+    }
+    else buf = malloc(size);
+	if(!buf)return -1;
+    unsigned current_depth = 0;
+    struct m_inode* current_ino;
+    struct m_inode* parent_ino;
+    for(;;){
+        current_ino = namei(".");
+        parent_ino = namei("..");
+        if(current_ino == parent_ino)
+            break;
+        sys_chdir("..");
+        //read_inode(current_ino);		这是个静态函数
+        //buf[current_depth++] = read_inode(current_ino);//根据节点号，在当前目录查找文件read_inode
+		current_depth++;
+    }
+    int i = current_depth-1;
+    for(i;i >= 0;i--){
+        printk("/%s",buf[i]);
+    }
+    printk("%s\n",current_depth==0?"/":"");
+    //复制过来
+    return 0;
+}