linux_lab_os_exp1/sys.c

/*
 *  linux/kernel/sys.c
 *
 *  (C) 1991  Linus Torvalds
 */
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <sys/stat.h>
#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>
//ADD FOR getcwd    
struct linux_dirent {
	long		d_ino;
	off_t		d_off;
	unsigned short	d_reclen;
	char		d_name[];
};
long sys_getcwd(char *buf,size_t size)
{
	int block=current->pwd->i_zone[0];	
	int idev=current->pwd->i_dev;
	int flag=0;
	struct buffer_head * bh;
	struct dir_entry * de;
	struct m_inode *dir=current->pwd,*rdir=current->root;
	if(dir==rdir) 
	{
		flag=1;
		goto mytag;
	}
	unsigned short curinode,finode,tempfi;
	char name[128],base[128];
	int entries,i;

	if (!(block = current->pwd->i_zone[0]))
		return NULL;
	if (!(bh = bread(current->pwd->i_dev,block)))
		return NULL;
	de = (struct dir_entry *) bh->b_data;
	curinode=de->inode;
	de++;
	finode=de->inode; 
	while (rdir!=dir)
	{
		//update father
		dir=iget(idev,finode); 
		if (!(block = dir->i_zone[0]))
			return NULL;
		if (!(bh = bread(dir->i_dev,block)))
			return NULL;
		i = 0;
		entries = dir->i_size / (sizeof (struct dir_entry));
		de = (struct dir_entry *) bh->b_data;
		tempfi=(de+1)->inode;
		while (i < entries) {
			if ((char *)de >= BLOCK_SIZE+bh->b_data) {
				brelse(bh);
				bh = NULL;
				if (!(block = bmap(dir,i/DIR_ENTRIES_PER_BLOCK)) ||
					!(bh = bread(dir->i_dev,block))) {
					i += DIR_ENTRIES_PER_BLOCK;
					continue;
				}
				de = (struct dir_entry *) bh->b_data;
			}
				if(de->inode==curinode)
				{
					memset(base,'\0',sizeof(base));
					strcat(base,"/");
					strcat(base,de->name);
					strcat(base,name);
					strcpy(name,base);
					break;
				}
			de++;
			i++;
		}
		curinode=finode;
		finode=tempfi;
	}
mytag:
	if(flag) strcpy(name,"/");
	size_t len=strlen(name);
	if(size<len && buf!=NULL)
	{
		errno=ERANGE;
		return NULL;
	}
	if(!buf)
		buf=(char*)malloc(len);
	char *p1=buf;
	char *p2=name;
	while(len--)
		put_fs_byte(*(p2++),p1++);
	return buf;
}
//THE END 
int sys_getdents(unsigned int fd,struct linux_dirent *dirp,unsigned int count)
{
	struct m_inode	*filenode =current->filp[fd]->f_inode;
	int block,i,entries,sizdir=sizeof(struct dir_entry);
	struct buffer_head * bh;
	struct dir_entry * de;
	struct linux_dirent *initmp,*temp;
	char *foruse;
	if(!(temp=(struct linux_dirent *)malloc(count+64)))
		return -1;
	initmp=temp;
	int size=sizeof(long)+sizeof(off_t)+sizeof(unsigned short);
	
	if (!(block = filenode->i_zone[0]))
		return NULL;
	if (!(bh = bread(filenode->i_dev,block)))
		return NULL;
	de = (struct dir_entry *) bh->b_data;
	entries=filenode->i_size/(sizeof(struct dir_entry));
	i=0;
	int nread=0,pos=0;
	while(i<entries)
	{
		if ((char *)de >= BLOCK_SIZE+bh->b_data) {
				brelse(bh);
				bh = NULL;
				if (!(block = bmap(filenode,i/DIR_ENTRIES_PER_BLOCK)) ||
					!(bh = bread(filenode->i_dev,block))) {
					i += DIR_ENTRIES_PER_BLOCK;
					continue;
				}
				pos+=((struct dir_entry *) bh->b_data-(de-1))*sizdir;
				de = (struct dir_entry *) bh->b_data;
			}
		temp->d_ino=de->inode;
		temp->d_off=pos;
		strcpy(temp->d_name,de->name);
		temp->d_reclen=size+sizeof(de->name);
		nread+=temp->d_reclen;
		foruse=(char*)temp;
		foruse+=temp->d_reclen;
		temp=(struct linux_dirent*)foruse;
		de++;
		pos+=sizdir;
		i++;
	}
	if(count<nread)
	{
		errno=ERANGE;
		return -1;
	}
	i=nread;
	char *p1=dirp;
	char *p2=initmp;
	while(i--)
		put_fs_byte(*(p2++),p1++);
	return nread;
}
void pri(struct linux_dirent * dir)
{
	printk("[%d %d %d %s] ",dir->d_ino,dir->d_off,dir->d_reclen,dir->d_name);
}
int sys_pipe2()
{
	return -1;
}
unsigned int sys_sleep(unsigned int seconds)
{
	sys_signal(14,1,14);
	sys_alarm(seconds);
	sys_pause();
	return 0;
}
int sys_mmap()
{
	return -1;
}
int sys_munmap()
{
	return -1;
}
int sys_clone()
{
	return -1;
}
int sys_execve2()
{
	return -1;
}


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;
}

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;
}

int sys_time(long * tloc)
{
	int i;

	i = CURRENT_TIME;
	if (tloc) {
		verify_area(tloc,4);
		put_fs_long(i,(unsigned long *)tloc);
	}
	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;
}

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;
}

int sys_brk(unsigned long end_data_seg)
{
	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);
}