iwlwifi: mvm: refactor debugfs copy_from_user()

Abstract the copy_from_user() pattern into the macros defining
debugfs files, reducing the code and making adding new files
safer by avoiding having deal with copy_from_user() directly.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/mvm/debugfs.h b/drivers/net/wireless/iwlwifi/mvm/debugfs.h
index faa73b8..85f9f95 100644
--- a/drivers/net/wireless/iwlwifi/mvm/debugfs.h
+++ b/drivers/net/wireless/iwlwifi/mvm/debugfs.h
@@ -68,17 +68,34 @@
 	.llseek = generic_file_llseek,					\
 }
 
-#define MVM_DEBUGFS_READ_WRITE_FILE_OPS(name)				\
+#define MVM_DEBUGFS_WRITE_WRAPPER(name, buflen, argtype)		\
+static ssize_t _iwl_dbgfs_##name##_write(struct file *file,		\
+					 const char __user *user_buf,	\
+					 size_t count, loff_t *ppos)	\
+{									\
+	argtype *arg = file->private_data;				\
+	char buf[buflen] = {};						\
+	size_t buf_size = min(count, sizeof(buf) -  1);			\
+									\
+	if (copy_from_user(buf, user_buf, buf_size))			\
+		return -EFAULT;						\
+									\
+	return iwl_dbgfs_##name##_write(arg, buf, buf_size, ppos);	\
+}									\
+
+#define _MVM_DEBUGFS_READ_WRITE_FILE_OPS(name, buflen, argtype)		\
+MVM_DEBUGFS_WRITE_WRAPPER(name, buflen, argtype)			\
 static const struct file_operations iwl_dbgfs_##name##_ops = {		\
-	.write = iwl_dbgfs_##name##_write,				\
+	.write = _iwl_dbgfs_##name##_write,				\
 	.read = iwl_dbgfs_##name##_read,				\
 	.open = simple_open,						\
 	.llseek = generic_file_llseek,					\
 };
 
-#define MVM_DEBUGFS_WRITE_FILE_OPS(name)				\
+#define _MVM_DEBUGFS_WRITE_FILE_OPS(name, buflen, argtype)		\
+MVM_DEBUGFS_WRITE_WRAPPER(name, buflen, argtype)			\
 static const struct file_operations iwl_dbgfs_##name##_ops = {		\
-	.write = iwl_dbgfs_##name##_write,				\
+	.write = _iwl_dbgfs_##name##_write,				\
 	.open = simple_open,						\
 	.llseek = generic_file_llseek,					\
 };