sysctl.c

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 * procname - the name of the sysctl file under /proc/sys. Set to %NULL to not
 *            enter a sysctl file
 *
 * data - a pointer to data for use by proc_handler
 *
 * maxlen - the maximum size in bytes of the data
 *
 * mode - the file permissions for the /proc/sys file, and for sysctl(2)
 *
 * child - a pointer to the child sysctl table if this entry is a directory, or
 *         %NULL.
 *
 * proc_handler - the text handler routine (described below)
 *
 * strategy - the strategy routine (described below)
 *
 * de - for internal use by the sysctl routines
 *
 * extra1, extra2 - extra pointers usable by the proc handler routines
 *
 * Leaf nodes in the sysctl tree will be represented by a single file
 * under /proc; non-leaf nodes will be represented by directories.
 *
 * sysctl(2) can automatically manage read and write requests through
 * the sysctl table.  The data and maxlen fields of the ctl_table
 * struct enable minimal validation of the values being written to be
 * performed, and the mode field allows minimal authentication.
 *
 * More sophisticated management can be enabled by the provision of a
 * strategy routine with the table entry.  This will be called before
 * any automatic read or write of the data is performed.
 *
 * The strategy routine may return
 *
 * < 0 - Error occurred (error is passed to user process)
 *
 * 0   - OK - proceed with automatic read or write.
 *
 * > 0 - OK - read or write has been done by the strategy routine, so
 *       return immediately.
 *
 * There must be a proc_handler routine for any terminal nodes
 * mirrored under /proc/sys (non-terminals are handled by a built-in
 * directory handler).  Several default handlers are available to
 * cover common cases -
 *
 * proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
 * proc_dointvec_minmax(), proc_doulongvec_ms_jiffies_minmax(),
 * proc_doulongvec_minmax()
 *
 * It is the handler's job to read the input buffer from user memory
 * and process it. The handler should return 0 on success.
 *
 * This routine returns %NULL on a failure to register, and a pointer
 * to the table header on success.
 */
struct ctl_table_header *register_sysctl_table(ctl_table * table, 
					       int insert_at_head)
{
	struct ctl_table_header *tmp;
	tmp = kmalloc(sizeof(struct ctl_table_header), GFP_KERNEL);
	if (!tmp)
		return NULL;
	tmp->ctl_table = table;
	INIT_LIST_HEAD(&tmp->ctl_entry);
	if (insert_at_head)
		list_add(&tmp->ctl_entry, &root_table_header.ctl_entry);
	else
		list_add_tail(&tmp->ctl_entry, &root_table_header.ctl_entry);
#ifdef CONFIG_PROC_FS
	register_proc_table(table, proc_sys_root);
#endif
	return tmp;
}

/**
 * unregister_sysctl_table - unregister a sysctl table heirarchy
 * @header: the header returned from register_sysctl_table
 *
 * Unregisters the sysctl table and all children. proc entries may not
 * actually be removed until they are no longer used by anyone.
 */
void unregister_sysctl_table(struct ctl_table_header * header)
{
	list_del(&header->ctl_entry);
#ifdef CONFIG_PROC_FS
	unregister_proc_table(header->ctl_table, proc_sys_root);
#endif
	kfree(header);
}

/*
 * /proc/sys support
 */

#ifdef CONFIG_PROC_FS

/* Scan the sysctl entries in table and add them all into /proc */
static void register_proc_table(ctl_table * table, struct proc_dir_entry *root)
{
	struct proc_dir_entry *de;
	int len;
	mode_t mode;
	
	for (; table->ctl_name; table++) {
		/* Can't do anything without a proc name. */
		if (!table->procname)
			continue;
		/* Maybe we can't do anything with it... */
		if (!table->proc_handler && !table->child) {
			printk(KERN_WARNING "SYSCTL: Can't register %s\n",
				table->procname);
			continue;
		}

		len = strlen(table->procname);
		mode = table->mode;

		de = NULL;
		if (table->proc_handler)
			mode |= S_IFREG;
		else {
			mode |= S_IFDIR;
			for (de = root->subdir; de; de = de->next) {
				if (proc_match(len, table->procname, de))
					break;
			}
			/* If the subdir exists already, de is non-NULL */
		}

		if (!de) {
			de = create_proc_entry(table->procname, mode, root);
			if (!de)
				continue;
			de->data = (void *) table;
			if (table->proc_handler) {
				de->proc_fops = &proc_sys_file_operations;
				de->proc_iops = &proc_sys_inode_operations;
			}
		}
		table->de = de;
		if (de->mode & S_IFDIR)
			register_proc_table(table->child, de);
	}
}

/*
 * Unregister a /proc sysctl table and any subdirectories.
 */
static void unregister_proc_table(ctl_table * table, struct proc_dir_entry *root)
{
	struct proc_dir_entry *de;
	for (; table->ctl_name; table++) {
		if (!(de = table->de))
			continue;
		if (de->mode & S_IFDIR) {
			if (!table->child) {
				printk (KERN_ALERT "Help - malformed sysctl tree on free\n");
				continue;
			}
			unregister_proc_table(table->child, de);

			/* Don't unregister directories which still have entries.. */
			if (de->subdir)
				continue;
		}

		/* Don't unregister proc entries that are still being used.. */
		if (atomic_read(&de->count))
			continue;

		table->de = NULL;
		remove_proc_entry(table->procname, root);
	}
}

static ssize_t do_rw_proc(int write, struct file * file, char * buf,
			  size_t count, loff_t *ppos)
{
	int op;
	struct proc_dir_entry *de;
	struct ctl_table *table;
	size_t res;
	ssize_t error;
	
	de = (struct proc_dir_entry*) file->f_dentry->d_inode->u.generic_ip;
	if (!de || !de->data)
		return -ENOTDIR;
	table = (struct ctl_table *) de->data;
	if (!table || !table->proc_handler)
		return -ENOTDIR;
	op = (write ? 002 : 004);
	if (ctl_perm(table, op))
		return -EPERM;
	
	res = count;

	/*
	 * FIXME: we need to pass on ppos to the handler.
	 */

	error = (*table->proc_handler) (table, write, file, buf, &res);
	if (error)
		return error;
	return res;
}

static ssize_t proc_readsys(struct file * file, char * buf,
			    size_t count, loff_t *ppos)
{
	return do_rw_proc(0, file, buf, count, ppos);
}

static ssize_t proc_writesys(struct file * file, const char * buf,
			     size_t count, loff_t *ppos)
{
	return do_rw_proc(1, file, (char *) buf, count, ppos);
}

static int proc_sys_permission(struct inode *inode, int op)
{
	return test_perm(inode->i_mode, op);
}

/**
 * proc_dostring - read a string sysctl
 * @table: the sysctl table
 * @write: %TRUE if this is a write to the sysctl file
 * @filp: the file structure
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 *
 * Reads/writes a string from/to the user buffer. If the kernel
 * buffer provided is not large enough to hold the string, the
 * string is truncated. The copied string is %NULL-terminated.
 * If the string is being read by the user process, it is copied
 * and a newline '\n' is added. It is truncated if the buffer is
 * not large enough.
 *
 * Returns 0 on success.
 */
int proc_dostring(ctl_table *table, int write, struct file *filp,
		  void *buffer, size_t *lenp)
{
	size_t len;
	char *p, c;
	
	if (!table->data || !table->maxlen || !*lenp ||
	    (filp->f_pos && !write)) {
		*lenp = 0;
		return 0;
	}
	
	if (write) {
		len = 0;
		p = buffer;
		while (len < *lenp) {
			if(get_user(c, p++))
				return -EFAULT;
			if (c == 0 || c == '\n')
				break;
			len++;
		}
		if (len >= table->maxlen)
			len = table->maxlen-1;
		if(copy_from_user(table->data, buffer, len))
			return -EFAULT;
		((char *) table->data)[len] = 0;
		filp->f_pos += *lenp;
	} else {
		len = strlen(table->data);
		if (len > table->maxlen)
			len = table->maxlen;
		if (len > *lenp)
			len = *lenp;
		if (len)
			if(copy_to_user(buffer, table->data, len))
				return -EFAULT;
		if (len < *lenp) {
			if(put_user('\n', ((char *) buffer) + len))
				return -EFAULT;
			len++;
		}
		*lenp = len;
		filp->f_pos += len;
	}
	return 0;
}

/*
 *	Special case of dostring for the UTS structure. This has locks
 *	to observe. Should this be in kernel/sys.c ????
 */
 
static int proc_doutsstring(ctl_table *table, int write, struct file *filp,
		  void *buffer, size_t *lenp)
{
	int r;

	if (!write) {
		down_read(&uts_sem);
		r=proc_dostring(table,0,filp,buffer,lenp);
		up_read(&uts_sem);
	} else {
		down_write(&uts_sem);
		r=proc_dostring(table,1,filp,buffer,lenp);
		up_write(&uts_sem);
	}
	return r;
}

#define OP_SET	0
#define OP_AND	1
#define OP_OR	2
#define OP_MAX	3
#define OP_MIN	4

static int do_proc_dointvec(ctl_table *table, int write, struct file *filp,
		  void *buffer, size_t *lenp, int conv, int op)
{
	int *i, vleft, first=1, neg, val;
	size_t left, len;
	
	#define TMPBUFLEN 20
	char buf[TMPBUFLEN], *p;
	
	if (!table->data || !table->maxlen || !*lenp ||
	    (filp->f_pos && !write)) {
		*lenp = 0;
		return 0;
	}
	
	i = (int *) table->data;
	vleft = table->maxlen / sizeof(int);
	left = *lenp;
	
	for (; left && vleft--; i++, first=0) {
		if (write) {
			while (left) {
				char c;
				if(get_user(c,(char *) buffer))
					return -EFAULT;
				if (!isspace(c))
					break;
				left--;
				((char *) buffer)++;
			}
			if (!left)
				break;
			neg = 0;
			len = left;
			if (len > TMPBUFLEN-1)
				len = TMPBUFLEN-1;
			if(copy_from_user(buf, buffer, len))
				return -EFAULT;
			buf[len] = 0;
			p = buf;
			if (*p == '-' && left > 1) {
				neg = 1;
				left--, p++;
			}
			if (*p < '0' || *p > '9')
				break;
			val = simple_strtoul(p, &p, 0) * conv;
			len = p-buf;
			if ((len < left) && *p && !isspace(*p))
				break;
			if (neg)
				val = -val;
			buffer += len;
			left -= len;
			switch(op) {
			case OP_SET:	*i = val; break;
			case OP_AND:	*i &= val; break;
			case OP_OR:	*i |= val; break;
			case OP_MAX:	if(*i < val)
						*i = val;
					break;
			case OP_MIN:	if(*i > val)
						*i = val;
					break;
			}
		} else {
			p = buf;
			if (!first)
				*p++ = '\t';
			sprintf(p, "%d", (*i) / conv);
			len = strlen(buf);
			if (len > left)
				len = left;
			if(copy_to_user(buffer, buf, len))
				return -EFAULT;
			left -= len;
			buffer += len;
		}
	}

	if (!write && !first && left) {
		if(put_user('\n', (char *) buffer))
			return -EFAULT;
		left--, buffer++;
	}
	if (write) {
		p = (char *) buffer;
		while (left) {
			char c;
			if(get_user(c, p++))
				return -EFAULT;
			if (!isspace(c))
				break;
			left--;
		}
	}
	if (write && first)
		return -EINVAL;
	*lenp -= left;
	filp->f_pos += *lenp;
	return 0;
}

/**
 * proc_dointvec - read a vector of integers
 * @table: the sysctl table
 * @write: %TRUE if this is a write to the sysctl file
 * @filp: the file structure
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
 * values from/to the user buffer, treated as an ASCII string. 
 *
 * Returns 0 on success.
 */
int proc_dointvec(ctl_table *table, int write, struct file *filp,
		     void *buffer, size_t *lenp)
{
    return do_proc_dointvec(table,write,filp,buffer,lenp,1,OP_SET);
}

/*
 *	init may raise the set.
 */
 
int proc_dointvec_bset(ctl_table *table, int write, struct file *filp,
			void *buffer, size_t *lenp)
{
	if (!capable(CAP_SYS_MODULE)) {
		return -EPERM;
	}
	return do_proc_dointvec(table,write,filp,buffer,lenp,1,
				(current->pid == 1) ? OP_SET : OP_AND);
}

/**
 * proc_dointvec_minmax - read a vector of integers with min/max values
 * @table: the sysctl table
 * @write: %TRUE if this is a write to the sysctl file
 * @filp: the file structure
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
 * values from/to the user buffer, treated as an ASCII string.
 *
 * This routine will ensure the values are within the range specified by
 * table->extra1 (min) and table->extra2 (max).
 *
 * Returns 0 on success.
 */
int proc_dointvec_minmax(ctl_table *table, int write, struct file *filp,
		  void *buffer, size_t *lenp)
{
	int *i, *min, *max, vleft, first=1, neg, val;
	size_t len, left;
	#define TMPBUFLEN 20
	char buf[TMPBUFLEN], *p;
	
	if (!table->data || !table->maxlen || !*lenp ||
	    (filp->f_pos && !write)) {
		*lenp = 0;
		return 0;
	}
	
	i = (int *) table->data;
	min = (int *) table->extra1;
	max = (int *) table->extra2;
	vleft = table->maxlen / sizeof(int);
	left = *lenp;
	
	for (; left && vleft--; i++, first=0) {
		if (write) {
			while (left) {
				char c;
				if(get_user(c, (char *) buffer))
					return -EFAULT;
				if (!isspace(c))
					break;