[PATCH] proc: sysctl: add _proc_do_string helper

The logic in proc_do_string is worth re-using without passing in a
ctl_table structure (say, we want to calculate a pointer and pass that in
instead); pass in the two fields it uses from that structure as explicit
arguments.

Signed-off-by: Sam Vilain <sam.vilain@catalyst.net.nz>
Cc: Serge E. Hallyn <serue@us.ibm.com>
Cc: Kirill Korotaev <dev@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Andrey Savochkin <saw@sw.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/sysctl.c

@@ -1624,32 +1624,14 @@ static ssize_t proc_writesys(struct file * file, const char __user * buf,
 	return do_rw_proc(1, file, (char __user *) buf, count, ppos);
 }
 
-/**
- * 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
- * @ppos: file position
- *
- * 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 __user *buffer, size_t *lenp, loff_t *ppos)
+int _proc_do_string(void* data, int maxlen, int write, struct file *filp,
+		    void __user *buffer, size_t *lenp, loff_t *ppos)
 {
 	size_t len;
 	char __user *p;
 	char c;
 
-	if (!table->data || !table->maxlen || !*lenp ||
+	if (!data || !maxlen || !*lenp ||
 	    (*ppos && !write)) {
 		*lenp = 0;
 		return 0;
@@ -1665,20 +1647,20 @@ int proc_dostring(ctl_table *table, int write, struct file *filp,
 				break;
 			len++;
 		}
-		if (len >= table->maxlen)
-			len = table->maxlen-1;
-		if(copy_from_user(table->data, buffer, len))
+		if (len >= maxlen)
+			len = maxlen-1;
+		if(copy_from_user(data, buffer, len))
 			return -EFAULT;
-		((char *) table->data)[len] = 0;
+		((char *) data)[len] = 0;
 		*ppos += *lenp;
 	} else {
-		len = strlen(table->data);
-		if (len > table->maxlen)
-			len = table->maxlen;
+		len = strlen(data);
+		if (len > maxlen)
+			len = maxlen;
 		if (len > *lenp)
 			len = *lenp;
 		if (len)
-			if(copy_to_user(buffer, table->data, len))
+			if(copy_to_user(buffer, data, len))
 				return -EFAULT;
 		if (len < *lenp) {
 			if(put_user('\n', ((char __user *) buffer) + len))
@@ -1691,6 +1673,31 @@ int proc_dostring(ctl_table *table, int write, struct file *filp,
 	return 0;
 }
 
+/**
+ * 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
+ * @ppos: file position
+ *
+ * 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 __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	return _proc_do_string(table->data, table->maxlen, write, filp,
+			       buffer, lenp, ppos);
+}
+
 /*
  *	Special case of dostring for the UTS structure. This has locks
  *	to observe. Should this be in kernel/sys.c ????