include/linux/tracefs.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  *  tracefs.h - a pseudo file system for activating tracing
   4  *
   5  * Based on debugfs by: 2004 Greg Kroah-Hartman <greg@kroah.com>
   6  *
   7  *  Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com>
   8  *
   9  * tracefs is the file system that is used by the tracing infrastructure.
  10  */
  11
  12 #ifndef _TRACEFS_H_
  13 #define _TRACEFS_H_
  14
  15 #include <linux/fs.h>
  16 #include <linux/seq_file.h>
  17
  18 #include <linux/types.h>
  19
  20 struct file_operations;
  21
  22 #ifdef CONFIG_TRACING
  23
  24 struct eventfs_file;
  25
  26 /**
  27  * eventfs_callback - A callback function to create dynamic files in eventfs
  28  * @name: The name of the file that is to be created
  29  * @mode: return the file mode for the file (RW access, etc)
  30  * @data: data to pass to the created file ops
  31  * @fops: the file operations of the created file
  32  *
  33  * The evetnfs files are dynamically created. The struct eventfs_entry array
  34  * is passed to eventfs_create_dir() or eventfs_create_events_dir() that will
  35  * be used to create the files within those directories. When a lookup
  36  * or access to a file within the directory is made, the struct eventfs_entry
  37  * array is used to find a callback() with the matching name that is being
  38  * referenced (for lookups, the entire array is iterated and each callback
  39  * will be called).
  40  *
  41  * The callback will be called with @name for the name of the file to create.
  42  * The callback can return less than 1 to indicate  that no file should be
  43  * created.
  44  *
  45  * If a file is to be created, then @mode should be populated with the file
  46  * mode (permissions) for which the file is created for. This would be
  47  * used to set the created inode i_mode field.
  48  *
  49  * The @data should be set to the data passed to the other file operations
  50  * (read, write, etc). Note, @data will also point to the data passed in
  51  * to eventfs_create_dir() or eventfs_create_events_dir(), but the callback
  52  * can replace the data if it chooses to. Otherwise, the original data
  53  * will be used for the file operation functions.
  54  *
  55  * The @fops should be set to the file operations that will be used to create
  56  * the inode.
  57  *
  58  * NB. This callback is called while holding internal locks of the eventfs
  59  *     system. The callback must not call any code that might also call into
  60  *     the tracefs or eventfs system or it will risk creating a deadlock.
  61  */
  62 typedef int (*eventfs_callback)(const char *name, umode_t *mode, void **data,
  63                                 const struct file_operations **fops);
  64
  65 typedef void (*eventfs_release)(const char *name, void *data);
  66
  67 /**
  68  * struct eventfs_entry - dynamically created eventfs file call back handler
  69  * @name:       Then name of the dynamic file in an eventfs directory
  70  * @callback:   The callback to get the fops of the file when it is created
  71  *
  72  * See evenfs_callback() typedef for how to set up @callback.
  73  */
  74 struct eventfs_entry {
  75         const char                      *name;
  76         eventfs_callback                callback;
  77         eventfs_release                 release;
  78 };
  79
  80 struct eventfs_inode;
  81
  82 struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry *parent,
  83                                                 const struct eventfs_entry *entries,
  84                                                 int size, void *data);
  85
  86 struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode *parent,
  87                                          const struct eventfs_entry *entries,
  88                                          int size, void *data);
  89
  90 void eventfs_remove_events_dir(struct eventfs_inode *ei);
  91 void eventfs_remove_dir(struct eventfs_inode *ei);
  92
  93 struct dentry *tracefs_create_file(const char *name, umode_t mode,
  94                                    struct dentry *parent, void *data,
  95                                    const struct file_operations *fops);
  96
  97 struct dentry *tracefs_create_dir(const char *name, struct dentry *parent);
  98
  99 void tracefs_remove(struct dentry *dentry);
 100
 101 struct dentry *tracefs_create_instance_dir(const char *name, struct dentry *parent,
 102                                            int (*mkdir)(const char *name),
 103                                            int (*rmdir)(const char *name));
 104
 105 bool tracefs_initialized(void);
 106
 107 #endif /* CONFIG_TRACING */
 108
 109 #endif