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/*
* linux/kernel/sys.c
*
* (C) 1991 Linus Torvalds
*/
#include <errno.h>
#include <linux/sched.h>
#include <linux/tty.h>
#include <linux/kernel.h>
#include <asm/segment.h>
#include <sys/times.h>
#include <sys/utsname.h>
//返回ENOSYS的函数，表明本系统版本还没有实现的函数
int sys_ftime()//返回时间日期
{
return -ENOSYS;
}
int sys_break()//
{
return -ENOSYS;
}
int sys_ptrace()//当前进程对子进程进行调试
{
return -ENOSYS;
}
int sys_stty()//修改并打引终端行设置
{
return -ENOSYS;
}
int sys_gtty()//取得终端行信息
{
return -ENOSYS;
}
int sys_rename()//修改文件名
{
return -ENOSYS;
}
int sys_prof()//程序执行时间区域。
{
return -ENOSYS;
}
int sys_setregid(int rgid, int egid)//设置当前任务的实际以及有效组ID
{
if (rgid>0) {
if ((current->gid == rgid) ||
suser())//是否为超级用户
current->gid = rgid;
else
return(-EPERM);
}
if (egid>0) {
if ((current->gid == egid) ||
(current->egid == egid) ||
(current->sgid == egid) ||
suser())//是否为超级用户
current->egid = egid;
else
return(-EPERM);
}
return 0;
}
int sys_setgid(int gid)//设置进程组号
{
return(sys_setregid(gid, gid));
}
int sys_acct()//打开关闭进程记帐功能
{
return -ENOSYS;
}
int sys_phys()//映射任意物理内存到进程的虚拟空间
{
return -ENOSYS;
}
int sys_lock()//
{
return -ENOSYS;
}
int sys_mpx()//
{
return -ENOSYS;
}
int sys_ulimit()//
{
return -ENOSYS;
}
int sys_time(long * tloc)//取当前时间，从1970年1月1日0点0分0秒开始
{
int i;
i = CURRENT_TIME;
if (tloc) {
verify_area(tloc,4);//验证内存容量
put_fs_long(i,(unsigned long *)tloc);//存入数据 段tloc中
}
return i;
}
/*
* Unprivileged users may change the real user id to the effective uid
* or vice versa.
*/
int sys_setreuid(int ruid, int euid)//设置进程的实际以及有效的用户ID
{
int old_ruid = current->uid;
if (ruid>0) {
if ((current->euid==ruid) ||
(old_ruid == ruid) ||
suser())//超级用户
current->uid = ruid;
else
return(-EPERM);
}
if (euid>0) {
if ((old_ruid == euid) ||
(current->euid == euid) ||
suser())//超级用户
current->euid = euid;
else {
current->uid = old_ruid;
return(-EPERM);
}
}
return 0;
}
int sys_setuid(int uid)//设置用户ID
{
return(sys_setreuid(uid, uid));
}
int sys_stime(long * tptr)//设置系统开机时间，参数tptr为从1970年1月1日0点0分0秒开始的时间值
{
if (!suser())
return -EPERM;
startup_time = get_fs_long((unsigned long *)tptr) - jiffies/HZ;//当前时间值减去系统运行的时间值，也就是系统开机的霎时间值，其中HZ=100,为系统运行频率
return 0;
}
int sys_times(struct tms * tbuf)//取得当前任务运行时间统计值
{
if (tbuf) {
verify_area(tbuf,sizeof *tbuf);
put_fs_long(current->utime,(unsigned long *)&tbuf->tms_utime);//用户运行时间
put_fs_long(current->stime,(unsigned long *)&tbuf->tms_stime);//内核运行时间
put_fs_long(current->cutime,(unsigned long *)&tbuf->tms_cutime);//子进程用户运行时间
put_fs_long(current->cstime,(unsigned long *)&tbuf->tms_cstime);//子进程内核运行时间
}
return jiffies;
}
int sys_brk(unsigned long end_data_seg)//修改数据段长度
{
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)//设置进程组ID
{
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)//返回当前进程 的进程组号
{
return current->pgrp;
}
int sys_setsid(void)//创建一个会 话
{
if (current->leader && !suser())
return -EPERM;
current->leader = 1;
current->session = current->pgrp = current->pid;//会话号==组号==进程号
current->tty = -1;
return current->pgrp;
}
int sys_uname(struct utsname * name)//取得系统相关信息
{
static struct utsname thisname = {
"linux .0","nodename","release ","version ","machine "
};
int i;
if (!name) return -ERROR;
verify_area(name,sizeof *name);//验证内存空间
for(i=0;i<sizeof *name;i++)
put_fs_byte(((char *) &thisname)[i],i+(char *) name);//将utsname 中的信息逐字节复制到用户缓冲区中
return 0;
}
int sys_umask(int mask)//设置当前进程文件属性屏蔽码
{
int old = current->umask;
current->umask = mask & 0777;
return (old);
}
int sys_newfuction(void)
{
}
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