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Message-ID: <YF3Hv5zXb/6lauzs@hirez.programming.kicks-ass.net>
Date: Fri, 26 Mar 2021 12:38:39 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Greg KH <greg@...ah.com>
Cc: mingo@...nel.org, mgorman@...e.de, juri.lelli@...hat.com,
vincent.guittot@...aro.org, dietmar.eggemann@....com,
rostedt@...dmis.org, bsegall@...gle.com, bristot@...hat.com,
joshdon@...gle.com, valentin.schneider@....com,
linux-kernel@...r.kernel.org
Subject: [PATCH v2 6/9] debugfs: Implement debugfs_create_str()
On Fri, Mar 26, 2021 at 12:30:24PM +0100, Greg KH wrote:
> Great, change that and limit the size of the string that can be written
> and it looks good to me, thanks for adding this.
Here goes..
---
Subject: debugfs: Implement debugfs_create_str()
From: Peter Zijlstra <peterz@...radead.org>
Date: Thu Mar 25 10:53:55 CET 2021
Implement debugfs_create_str() to easily display names and such in
debugfs.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
fs/debugfs/file.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/debugfs.h | 27 ++++++++
2 files changed, 175 insertions(+)
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -865,6 +865,154 @@ struct dentry *debugfs_create_bool(const
}
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;
+
+again:
+ rcu_read_lock();
+ str = rcu_dereference(*(char **)file->private_data);
+ len = strlen(str) + 1;
+
+ if (!copy || copy_len < len) {
+ rcu_read_unlock();
+ kfree(copy);
+ copy = kmalloc(len + 1, GFP_KERNEL);
+ if (!copy) {
+ debugfs_file_put(dentry);
+ return -ENOMEM;
+ }
+ copy_len = len;
+ goto again;
+ }
+
+ strncpy(copy, str, len);
+ copy[len] = '\n';
+ copy[len+1] = '\0';
+ rcu_read_unlock();
+
+ debugfs_file_put(dentry);
+
+ ret = simple_read_from_buffer(user_buf, count, ppos, copy, len + 1);
+ kfree(copy);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(debugfs_read_file_str);
+
+ssize_t debugfs_write_file_str(struct file *file, const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct dentry *dentry = F_DENTRY(file);
+ char *old, *new = NULL;
+ int pos = *ppos;
+ int r;
+
+ r = debugfs_file_get(dentry);
+ if (unlikely(r))
+ return r;
+
+ old = *(char **)file->private_data;
+
+ /* only allow strict concattenation */
+ r = -EINVAL;
+ if (pos && pos != strlen(old))
+ goto error;
+
+ r = -E2BIG;
+ if (pos + count + 1 > PAGE_SIZE)
+ goto error;
+
+ r = -ENOMEM;
+ new = kmalloc(pos + count + 1, GFP_KERNEL);
+ if (!new)
+ goto error;
+
+ if (pos)
+ memcpy(new, old, pos);
+
+ r = -EFAULT;
+ if (copy_from_user(new + pos, user_buf, count))
+ goto error;
+
+ new[pos + count] = '\0';
+ strim(new);
+
+ rcu_assign_pointer(*(char **)file->private_data, new);
+ synchronize_rcu();
+ kfree(old);
+
+ debugfs_file_put(dentry);
+ return count;
+
+error:
+ kfree(new);
+ debugfs_file_put(dentry);
+ return r;
+}
+EXPORT_SYMBOL_GPL(debugfs_write_file_str);
+
+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.
+ *
+ * NOTE: when writing is enabled it will replace the string, string lifetime is
+ * assumed to be RCU managed.
+ *
+ * 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);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_str);
+
static ssize_t read_file_blob(struct file *file, char __user *user_buf,
size_t count, loff_t *ppos)
{
--- a/include/linux/debugfs.h
+++ b/include/linux/debugfs.h
@@ -128,6 +128,8 @@ void debugfs_create_atomic_t(const char
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 +158,12 @@ ssize_t debugfs_read_file_bool(struct fi
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);
+
+ssize_t debugfs_write_file_str(struct file *file, const char __user *user_buf,
+ size_t count, loff_t *ppos);
+
#else
#include <linux/err.h>
@@ -297,6 +305,11 @@ static inline struct dentry *debugfs_cre
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)
@@ -347,6 +360,20 @@ static inline ssize_t debugfs_write_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;
+}
+
+static inline ssize_t debugfs_write_file_str(struct file *file,
+ const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ return -ENODEV;
+}
#endif
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