C++ IS_RDONLY函数代码示例

/* 向文件发送一个命令，如获取文件信息的命令，
 * 将文件的信息拷贝到arg所指向的内存，如关于文件的flag和版本等信息
 */
int ext2_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,
		unsigned long arg)
{

	ext2_debug ("cmd = %u, arg = %lu\n", cmd, arg);

	switch (cmd) {
	case EXT2_IOC_GETFLAGS:
		put_fs_long (inode->u.ext2_i.i_flags, (long *) arg);
		return 0;
	case EXT2_IOC_SETFLAGS:
		if ((current->euid != inode->i_uid) && !suser())
			return -EPERM;
		if (IS_RDONLY(inode))
			return -EROFS;
		inode->u.ext2_i.i_flags = get_fs_long ((long *) arg);
		inode->i_ctime = CURRENT_TIME;
		inode->i_dirt = 1;
		return 0;
	case EXT2_IOC_GETVERSION:
		put_fs_long (inode->u.ext2_i.i_version, (long *) arg);
		return 0;
	case EXT2_IOC_SETVERSION:
		if ((current->euid != inode->i_uid) && !suser())
			return -EPERM;
		if (IS_RDONLY(inode))
			return -EROFS;
		inode->u.ext2_i.i_version = get_fs_long ((long *) arg);
		inode->i_ctime = CURRENT_TIME;
		inode->i_dirt = 1;
		return 0;
	default:
		return -EINVAL;
	}
}

static int xiafs_readdir(struct inode * inode, 
		       struct file * filp, struct dirent * dirent, int count)
{
    u_int offset, i;
    struct buffer_head * bh;
    struct xiafs_direct * de;

    if (!inode || !inode->i_sb || !S_ISDIR(inode->i_mode))
        return -EBADF;
    if (inode->i_size & (XIAFS_ZSIZE(inode->i_sb) - 1) )
        return -EBADF;
    while (filp->f_pos < inode->i_size) {
        offset = filp->f_pos & (XIAFS_ZSIZE(inode->i_sb) - 1);
	bh = xiafs_bread(inode, filp->f_pos >> XIAFS_ZSIZE_BITS(inode->i_sb),0);
	if (!bh) {
	    filp->f_pos += XIAFS_ZSIZE(inode->i_sb)-offset;
	    continue;
	}
	de = (struct xiafs_direct *) (offset + bh->b_data);
	while (offset < XIAFS_ZSIZE(inode->i_sb) && filp->f_pos < inode->i_size) {
	    if (de->d_ino > inode->i_sb->u.xiafs_sb.s_ninodes ||
		de->d_rec_len < 12 || 
		(char *)de+de->d_rec_len > XIAFS_ZSIZE(inode->i_sb)+bh->b_data ||
		de->d_name_len < 1 || de->d_name_len + 8 > de->d_rec_len ||
		de->d_name_len > _XIAFS_NAME_LEN ||
		de->d_name[de->d_name_len] ) {
	        printk("XIA-FS: bad directory entry (%s %d)\n", WHERE_ERR);
		brelse(bh);
		return 0;
	    }  
	    offset += de->d_rec_len;
	    filp->f_pos += de->d_rec_len;
	    if (de->d_ino) {
	        for (i = 0; i < de->d_name_len ; i++)
		    put_fs_byte(de->d_name[i],i+dirent->d_name);
		put_fs_byte(0,i+dirent->d_name);
		put_fs_long(de->d_ino,&dirent->d_ino);
		put_fs_word(i,&dirent->d_reclen);
		brelse(bh);
		if (!IS_RDONLY (inode)) {
		    inode->i_atime=CURRENT_TIME;		    
		    inode->i_dirt=1;
		}
		return i;
	    }
	    de = (struct xiafs_direct *) (offset + bh->b_data);
	}
	brelse(bh);
	if (offset > XIAFS_ZSIZE(inode->i_sb)) {
	    printk("XIA-FS: bad directory (%s %d)\n", WHERE_ERR);
	    return 0;
	}
    }
    if (!IS_RDONLY (inode)) {
	inode->i_atime=CURRENT_TIME;		    
	inode->i_dirt=1;
    }
    return 0;
}

int sys_chmod(char *filename, mode_t mode)
{
    struct inode *inode;
    register struct inode *inodep;
    int error = namei(filename, &inode, 0, 0);

#ifdef USE_NOTIFY_CHANGE
    struct iattr newattrs;
    register struct iattr *nap = &newattrs;

    inodep = inode;
    if (error)
	return error;
    if (IS_RDONLY(inodep)) {
	iput(inodep);
	return -EROFS;
    }
    if (mode == (mode_t) - 1)
	mode = inodep->i_mode;
    nap->ia_mode = (mode & S_IALLUGO) | (inodep->i_mode & ~S_IALLUGO);
    nap->ia_valid = ATTR_MODE | ATTR_CTIME;
    inodep->i_dirt = 1;
    error = notify_change(inodep, nap);
    iput(inodep);
#else
    if (!error) {
	inodep = inode;
	if (IS_RDONLY(inodep)) {
	    iput(inodep);
	    return -EROFS;
	}
	if (mode == (mode_t) - 1)
	    mode = inodep->i_mode;
	mode = (mode & S_IALLUGO) | (inodep->i_mode & ~S_IALLUGO);
	if ((current->euid != inodep->i_uid) && !suser()) {
/* FIXME - Should we iput(inodep); at this point? */
	    return -EPERM;
	}
	if (!suser() && !in_group_p(inodep->i_gid)) {
	    mode &= ~S_ISGID;
	}
	inodep->i_mode = mode;
	inodep->i_dirt = 1;
	iput(inodep);
    }
#endif
    return error;
}

asmlinkage int sys_chmod(const char * filename, mode_t mode)
{
	struct inode * inode;
	int error;
	struct iattr newattrs;

	error = namei(filename,&inode);
	if (error)
		return error;
	if (IS_RDONLY(inode)) {
		iput(inode);
		return -EROFS;
	}
	if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) {
		iput(inode);
		return -EPERM;
	}
	if (mode == (mode_t) -1)
		mode = inode->i_mode;
	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
	inode->i_dirt = 1;
	error = notify_change(inode, &newattrs);
	iput(inode);
	return error;
}

/* If times==NULL, set access and modification to current time,
 * must be owner or have write permission.
 * Else, update from *times, must be owner or super user.
 */
asmlinkage int sys_utime(char * filename, struct utimbuf * times)
{
	int error;
	struct inode * inode;
	struct iattr newattrs;

	error = namei(filename,&inode);
	if (error)
		return error;
	if (IS_RDONLY(inode)) {
		iput(inode);
		return -EROFS;
	}
	/* Don't worry, the checks are done in inode_change_ok() */
	newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
	if (times) {
		error = verify_area(VERIFY_READ, times, sizeof(*times));
		if (error) {
			iput(inode);
			return error;
		}
		newattrs.ia_atime = get_user(&times->actime);
		newattrs.ia_mtime = get_user(&times->modtime);
		newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
	} else {
		if (current->fsuid != inode->i_uid &&
		    (error = permission(inode,MAY_WRITE)) != 0) {
			iput(inode);
			return error;
		}
	}
	error = notify_change(inode, &newattrs);
	iput(inode);
	return error;
}

int sys_truncate(char *path, loff_t length)
{
    struct inode *inode;
    register struct inode *inodep;
    int error;

    error = namei(path, &inode, NOT_DIR, MAY_WRITE);
    inodep = inode;
    if (error)
	return error;
    if (IS_RDONLY(inodep)) {
	iput(inodep);
	return -EROFS;
    }
#ifdef BLOAT_FS
    error = get_write_access(inodep);
    if (error) {
	iput(inodep);
	return error;
    }
#endif
    error = do_truncate(inodep, length);
    put_write_access(inodep);
    iput(inodep);
    return error;
}

static int do_chown(register struct inode *inode, uid_t user, gid_t group)
{
    struct iattr newattrs;
    register struct iattr *nap = &newattrs;

    if (IS_RDONLY(inode))
	return -EROFS;
    if (user == (uid_t) - 1)
	user = inode->i_uid;
    if (group == (gid_t) - 1)
	group = inode->i_gid;
    nap->ia_mode = inode->i_mode;
    nap->ia_uid = user;
    nap->ia_gid = group;
    nap->ia_valid = ATTR_UID | ATTR_GID | ATTR_CTIME;

    /*
     * If the owner has been changed, remove the setuid bit
     */
    if (user != inode->i_uid && (inode->i_mode & S_ISUID)) {
	nap->ia_mode &= ~S_ISUID;
	nap->ia_valid |= ATTR_MODE;
    }

    /*
     * If the group has been changed, remove the setgid bit
     */
    if (group != inode->i_gid && (inode->i_mode & S_ISGID)) {
	nap->ia_mode &= ~S_ISGID;
	nap->ia_valid |= ATTR_MODE;
    }

    inode->i_dirt = 1;
    return notify_change(inode, nap);
}

STATIC int
xfs_attrmulti_attr_set(
	struct inode		*inode,
	char			*name,
	const char		__user *ubuf,
	__uint32_t		len,
	__uint32_t		flags)
{
	char			*kbuf;
	int			error = EFAULT;

	if (IS_RDONLY(inode))
		return -EROFS;
	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
		return EPERM;
	if (len > XATTR_SIZE_MAX)
		return EINVAL;

	kbuf = memdup_user(ubuf, len);
	if (IS_ERR(kbuf))
		return PTR_ERR(kbuf);

	error = xfs_attr_set(XFS_I(inode), name, kbuf, len, flags);

	return error;
}

struct chan *devopen(struct chan *c, int omode, struct dirtab *tab, int ntab,
                     Devgen * gen)
{
    int i;
    struct dir dir;

    dir.qid.path = 0;
    for (i = 0;; i++) {
        switch ((*gen) (c, NULL, tab, ntab, i, &dir)) {
        case -1:
            goto Return;
        case 0:
            break;
        case 1:
            if (c->qid.path == dir.qid.path) {
                devpermcheck(dir.uid, dir.mode, omode);
                goto Return;
            }
            break;
        }
    }
Return:
    c->offset = 0;
    if ((c->qid.type & QTDIR) && !IS_RDONLY(omode))
        error("Tried opening dir with non-read-only mode %o", omode);
    c->mode = openmode(omode);
    c->flag |= COPEN;
    return c;
}

asmlinkage long sys_chmod(const char * filename, mode_t mode)
{
	struct nameidata nd;
	struct inode * inode;
	int error;
	struct iattr newattrs;

	error = user_path_walk(filename, &nd);
	if (error)
		goto out;
	inode = nd.dentry->d_inode;

	error = -EROFS;
	if (IS_RDONLY(inode))
		goto dput_and_out;

	error = -EPERM;
	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
		goto dput_and_out;

	if (mode == (mode_t) -1)
		mode = inode->i_mode;
	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
	error = notify_change(nd.dentry, &newattrs);

dput_and_out:
	path_release(&nd);
out:
	return error;
}

int sys_utimes(char *filename, struct timeval *utimes)
{
    int error;
    struct inode *inode;
    register struct inode *inodep;
    struct iattr newattrs;

    error = namei(filename, &inode, 0, 0);
    inodep = inode;
    if (error)
	return error;
    if (IS_RDONLY(inodep)) {
	iput(inodep);
	return -EROFS;
    }
    /* Don't worry, the checks are done in inode_change_ok() */
    newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
    if (utimes) {
	struct timeval times[2];
	if (error = verified_memcpy_fromfs(&times, utimes, sizeof(times))) {
	    iput(inodep);
	    return error;
	}
	newattrs.ia_atime = times[0].tv_sec;
	newattrs.ia_mtime = times[1].tv_sec;
	newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
    } else if ((error = permission(inodep, MAY_WRITE)) != 0) {
	iput(inodep);
	return error;
    }
    error = notify_change(inodep, &newattrs);
    iput(inodep);
    return error;
}

STATIC int
xfs_attrmulti_attr_set(
	struct vnode		*vp,
	char			*name,
	const char		__user *ubuf,
	__uint32_t		len,
	__uint32_t		flags)
{
	char			*kbuf;
	int			error = EFAULT;

	if (IS_RDONLY(&vp->v_inode))
		return -EROFS;
	if (IS_IMMUTABLE(&vp->v_inode) || IS_APPEND(&vp->v_inode))
		return EPERM;
	if (len > XATTR_SIZE_MAX)
		return EINVAL;

	kbuf = kmalloc(len, GFP_KERNEL);
	if (!kbuf)
		return ENOMEM;

	if (copy_from_user(kbuf, ubuf, len))
		goto out_kfree;
			
	VOP_ATTR_SET(vp, name, kbuf, len, flags, NULL, error);

 out_kfree:
	kfree(kbuf);
	return error;
}

static inline long do_sys_truncate(const char * path, loff_t length)
{
    struct nameidata nd;
    struct inode * inode;
    int error;

    error = -EINVAL;
    if (length < 0)	/* sorry, but loff_t says... */
        goto out;

    error = user_path_walk(path, &nd);
    if (error)
        goto out;
    inode = nd.dentry->d_inode;

    /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
    error = -EISDIR;
    if (S_ISDIR(inode->i_mode))
        goto dput_and_out;

    error = -EINVAL;
    if (!S_ISREG(inode->i_mode))
        goto dput_and_out;

    error = permission(inode,MAY_WRITE);
    if (error)
        goto dput_and_out;

    error = -EROFS;
    if (IS_RDONLY(inode))
        goto dput_and_out;

    error = -EPERM;
    if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
        goto dput_and_out;

    /*
     * Make sure that there are no leases.
     */
    error = get_lease(inode, FMODE_WRITE);
    if (error)
        goto dput_and_out;

    error = get_write_access(inode);
    if (error)
        goto dput_and_out;

    error = locks_verify_truncate(inode, NULL, length);
    if (!error)
    {
        DQUOT_INIT(inode);
        error = do_truncate(nd.dentry, length);
    }
    put_write_access(inode);

dput_and_out:
    path_release(&nd);
out:
    return error;
}

asmlinkage long sys_fchmod(unsigned int fd, mode_t mode)
{
	struct inode * inode;
	struct dentry * dentry;
	struct file * file;
	int err = -EBADF;
	struct iattr newattrs;

	file = fget(fd);
	if (!file)
		goto out;

	dentry = file->f_dentry;
	inode = dentry->d_inode;

	err = -EROFS;
	if (IS_RDONLY(inode))
		goto out_putf;
	err = -EPERM;
	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
		goto out_putf;
	if (mode == (mode_t) -1)
		mode = inode->i_mode;
	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
	err = notify_change(dentry, &newattrs);

out_putf:
	fput(file);
out:
	return err;
}

static int chown_common(struct dentry * dentry, uid_t user, gid_t group)
{
	struct inode * inode;
	int error;
	struct iattr newattrs;

	error = -ENOENT;
	if (!(inode = dentry->d_inode)) {
		printk("chown_common: NULL inode\n");
		goto out;
	}
	error = -EROFS;
	if (IS_RDONLY(inode))
		goto out;
	error = -EPERM;
	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
		goto out;
	if (user == (uid_t) -1)
		user = inode->i_uid;
	if (group == (gid_t) -1)
		group = inode->i_gid;
	newattrs.ia_mode = inode->i_mode;
	newattrs.ia_uid = user;
	newattrs.ia_gid = group;
	newattrs.ia_valid =  ATTR_UID | ATTR_GID | ATTR_CTIME;
	/*
	 * If the user or group of a non-directory has been changed by a
	 * non-root user, remove the setuid bit.
	 * 19981026	David C Niemi <[email protected]>
	 *
	 * Changed this to apply to all users, including root, to avoid
	 * some races. This is the behavior we had in 2.0. The check for
	 * non-root was definitely wrong for 2.2 anyway, as it should
	 * have been using CAP_FSETID rather than fsuid -- 19990830 SD.
	 */
	if ((inode->i_mode & S_ISUID) == S_ISUID &&
		!S_ISDIR(inode->i_mode))
	{
		newattrs.ia_mode &= ~S_ISUID;
		newattrs.ia_valid |= ATTR_MODE;
	}
	/*
	 * Likewise, if the user or group of a non-directory has been changed
	 * by a non-root user, remove the setgid bit UNLESS there is no group
	 * execute bit (this would be a file marked for mandatory locking).
	 * 19981026	David C Niemi <[email protected]>
	 *
	 * Removed the fsuid check (see the comment above) -- 19990830 SD.
	 */
	if (((inode->i_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) 
		&& !S_ISDIR(inode->i_mode))
	{
		newattrs.ia_mode &= ~S_ISGID;
		newattrs.ia_valid |= ATTR_MODE;
	}
	error = DQUOT_TRANSFER(dentry, &newattrs);
out:
	return error;
}