Commit 9af0440e authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

debugfs: Implement debugfs_create_str() 



Implement debugfs_create_str() to easily display names and such in
debugfs.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tested-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210412102001.415407080@infradead.org
parent 1011dcce

fs/debugfs/file.c

+91 −0
Original line number Diff line number Diff line
@@ -865,6 +865,97 @@ struct dentry *debugfs_create_bool(const char *name, umode_t mode, 
}

EXPORT_SYMBOL_GPL(debugfs_create_bool);



ssize_t debugfs_read_file_str(struct file *file, char __user *user_buf,

			      size_t count, loff_t *ppos)

{

	struct dentry *dentry = F_DENTRY(file);

	char *str, *copy = NULL;

	int copy_len, len;

	ssize_t ret;



	ret = debugfs_file_get(dentry);

	if (unlikely(ret))

		return ret;



	str = *(char **)file->private_data;

	len = strlen(str) + 1;

	copy = kmalloc(len, GFP_KERNEL);

	if (!copy) {

		debugfs_file_put(dentry);

		return -ENOMEM;

	}



	copy_len = strscpy(copy, str, len);

	debugfs_file_put(dentry);

	if (copy_len < 0) {

		kfree(copy);

		return copy_len;

	}



	copy[copy_len] = '\n';



	ret = simple_read_from_buffer(user_buf, count, ppos, copy, copy_len);

	kfree(copy);



	return ret;

}



static ssize_t debugfs_write_file_str(struct file *file, const char __user *user_buf,

				      size_t count, loff_t *ppos)

{

	/* This is really only for read-only strings */

	return -EINVAL;

}



static const struct file_operations fops_str = {

	.read =		debugfs_read_file_str,

	.write =	debugfs_write_file_str,

	.open =		simple_open,

	.llseek =	default_llseek,

};



static const struct file_operations fops_str_ro = {

	.read =		debugfs_read_file_str,

	.open =		simple_open,

	.llseek =	default_llseek,

};



static const struct file_operations fops_str_wo = {

	.write =	debugfs_write_file_str,

	.open =		simple_open,

	.llseek =	default_llseek,

};



/**

 * debugfs_create_str - create a debugfs file that is used to read and write a string value

 * @name: a pointer to a string containing the name of the file to create.

 * @mode: the permission that the file should have

 * @parent: a pointer to the parent dentry for this file.  This should be a

 *          directory dentry if set.  If this parameter is %NULL, then the

 *          file will be created in the root of the debugfs filesystem.

 * @value: a pointer to the variable that the file should read to and write

 *         from.

 *

 * This function creates a file in debugfs with the given name that

 * contains the value of the variable @value.  If the @mode variable is so

 * set, it can be read from, and written to.

 *

 * This function will return a pointer to a dentry if it succeeds.  This

 * pointer must be passed to the debugfs_remove() function when the file is

 * to be removed (no automatic cleanup happens if your module is unloaded,

 * you are responsible here.)  If an error occurs, ERR_PTR(-ERROR) will be

 * returned.

 *

 * If debugfs is not enabled in the kernel, the value ERR_PTR(-ENODEV) will

 * be returned.

 */

void debugfs_create_str(const char *name, umode_t mode,

			struct dentry *parent, char **value)

{

	debugfs_create_mode_unsafe(name, mode, parent, value, &fops_str,

				   &fops_str_ro, &fops_str_wo);

}



static ssize_t read_file_blob(struct file *file, char __user *user_buf,

			      size_t count, loff_t *ppos)

{

include/linux/debugfs.h

+17 −0
Original line number Diff line number Diff line
@@ -128,6 +128,8 @@ void debugfs_create_atomic_t(const char *name, umode_t mode, 
			     struct dentry *parent, atomic_t *value);

struct dentry *debugfs_create_bool(const char *name, umode_t mode,

				  struct dentry *parent, bool *value);

void debugfs_create_str(const char *name, umode_t mode,

			struct dentry *parent, char **value);



struct dentry *debugfs_create_blob(const char *name, umode_t mode,

				  struct dentry *parent,
@@ -156,6 +158,9 @@ ssize_t debugfs_read_file_bool(struct file *file, char __user *user_buf, 
ssize_t debugfs_write_file_bool(struct file *file, const char __user *user_buf,

				size_t count, loff_t *ppos);



ssize_t debugfs_read_file_str(struct file *file, char __user *user_buf,

			      size_t count, loff_t *ppos);



#else



#include <linux/err.h>
@@ -297,6 +302,11 @@ static inline struct dentry *debugfs_create_bool(const char *name, umode_t mode, 
	return ERR_PTR(-ENODEV);

}



static inline void debugfs_create_str(const char *name, umode_t mode,

				      struct dentry *parent,

				      char **value)

{ }



static inline struct dentry *debugfs_create_blob(const char *name, umode_t mode,

				  struct dentry *parent,

				  struct debugfs_blob_wrapper *blob)
@@ -348,6 +358,13 @@ static inline ssize_t debugfs_write_file_bool(struct file *file, 
	return -ENODEV;

}



static inline ssize_t debugfs_read_file_str(struct file *file,

					    char __user *user_buf,

					    size_t count, loff_t *ppos)

{

	return -ENODEV;

}



#endif



/**