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debugfs: Implement debugfs_create_str()

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

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210412102001.415407080@infradead.org
This commit is contained in:
Peter Zijlstra 2021-03-25 10:53:55 +01:00
parent 1011dcce99
commit 9af0440ec8
2 changed files with 108 additions and 0 deletions
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91
fs/debugfs/file.c
View File

@ -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)
{

17
include/linux/debugfs.h
View File

@ -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
/**