kernel/trace/trace_dynevent.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Generic dynamic event control interface
   4  *
   5  * Copyright (C) 2018 Masami Hiramatsu <mhiramat@kernel.org>
   6  */
   7
   8 #include <linux/debugfs.h>
   9 #include <linux/kernel.h>
  10 #include <linux/list.h>
  11 #include <linux/mm.h>
  12 #include <linux/mutex.h>
  13 #include <linux/tracefs.h>
  14
  15 #include "trace.h"
  16 #include "trace_dynevent.h"
  17
  18 static DEFINE_MUTEX(dyn_event_ops_mutex);
  19 static LIST_HEAD(dyn_event_ops_list);
  20
  21 int dyn_event_register(struct dyn_event_operations *ops)
  22 {
  23         if (!ops || !ops->create || !ops->show || !ops->is_busy ||
  24             !ops->free || !ops->match)
  25                 return -EINVAL;
  26
  27         INIT_LIST_HEAD(&ops->list);
  28         mutex_lock(&dyn_event_ops_mutex);
  29         list_add_tail(&ops->list, &dyn_event_ops_list);
  30         mutex_unlock(&dyn_event_ops_mutex);
  31         return 0;
  32 }
  33
  34 int dyn_event_release(int argc, char **argv, struct dyn_event_operations *type)
  35 {
  36         struct dyn_event *pos, *n;
  37         char *system = NULL, *event, *p;
  38         int ret = -ENOENT;
  39
  40         if (argv[0][0] == '-') {
  41                 if (argv[0][1] != ':')
  42                         return -EINVAL;
  43                 event = &argv[0][2];
  44         } else {
  45                 event = strchr(argv[0], ':');
  46                 if (!event)
  47                         return -EINVAL;
  48                 event++;
  49         }
  50         argc--; argv++;
  51
  52         p = strchr(event, '/');
  53         if (p) {
  54                 system = event;
  55                 event = p + 1;
  56                 *p = '\0';
  57         }
  58         if (event[0] == '\0')
  59                 return -EINVAL;
  60
  61         mutex_lock(&event_mutex);
  62         for_each_dyn_event_safe(pos, n) {
  63                 if (type && type != pos->ops)
  64                         continue;
  65                 if (!pos->ops->match(system, event,
  66                                 argc, (const char **)argv, pos))
  67                         continue;
  68
  69                 ret = pos->ops->free(pos);
  70                 if (ret)
  71                         break;
  72         }
  73         mutex_unlock(&event_mutex);
  74
  75         return ret;
  76 }
  77
  78 static int create_dyn_event(int argc, char **argv)
  79 {
  80         struct dyn_event_operations *ops;
  81         int ret = -ENODEV;
  82
  83         if (argv[0][0] == '-' || argv[0][0] == '!')
  84                 return dyn_event_release(argc, argv, NULL);
  85
  86         mutex_lock(&dyn_event_ops_mutex);
  87         list_for_each_entry(ops, &dyn_event_ops_list, list) {
  88                 ret = ops->create(argc, (const char **)argv);
  89                 if (!ret || ret != -ECANCELED)
  90                         break;
  91         }
  92         mutex_unlock(&dyn_event_ops_mutex);
  93         if (ret == -ECANCELED)
  94                 ret = -EINVAL;
  95
  96         return ret;
  97 }
  98
  99 /* Protected by event_mutex */
 100 LIST_HEAD(dyn_event_list);
 101
 102 void *dyn_event_seq_start(struct seq_file *m, loff_t *pos)
 103 {
 104         mutex_lock(&event_mutex);
 105         return seq_list_start(&dyn_event_list, *pos);
 106 }
 107
 108 void *dyn_event_seq_next(struct seq_file *m, void *v, loff_t *pos)
 109 {
 110         return seq_list_next(v, &dyn_event_list, pos);
 111 }
 112
 113 void dyn_event_seq_stop(struct seq_file *m, void *v)
 114 {
 115         mutex_unlock(&event_mutex);
 116 }
 117
 118 static int dyn_event_seq_show(struct seq_file *m, void *v)
 119 {
 120         struct dyn_event *ev = v;
 121
 122         if (ev && ev->ops)
 123                 return ev->ops->show(m, ev);
 124
 125         return 0;
 126 }
 127
 128 static const struct seq_operations dyn_event_seq_op = {
 129         .start  = dyn_event_seq_start,
 130         .next   = dyn_event_seq_next,
 131         .stop   = dyn_event_seq_stop,
 132         .show   = dyn_event_seq_show
 133 };
 134
 135 /*
 136  * dyn_events_release_all - Release all specific events
 137  * @type:       the dyn_event_operations * which filters releasing events
 138  *
 139  * This releases all events which ->ops matches @type. If @type is NULL,
 140  * all events are released.
 141  * Return -EBUSY if any of them are in use, and return other errors when
 142  * it failed to free the given event. Except for -EBUSY, event releasing
 143  * process will be aborted at that point and there may be some other
 144  * releasable events on the list.
 145  */
 146 int dyn_events_release_all(struct dyn_event_operations *type)
 147 {
 148         struct dyn_event *ev, *tmp;
 149         int ret = 0;
 150
 151         mutex_lock(&event_mutex);
 152         for_each_dyn_event(ev) {
 153                 if (type && ev->ops != type)
 154                         continue;
 155                 if (ev->ops->is_busy(ev)) {
 156                         ret = -EBUSY;
 157                         goto out;
 158                 }
 159         }
 160         for_each_dyn_event_safe(ev, tmp) {
 161                 if (type && ev->ops != type)
 162                         continue;
 163                 ret = ev->ops->free(ev);
 164                 if (ret)
 165                         break;
 166         }
 167 out:
 168         mutex_unlock(&event_mutex);
 169
 170         return ret;
 171 }
 172
 173 static int dyn_event_open(struct inode *inode, struct file *file)
 174 {
 175         int ret;
 176
 177         ret = tracing_check_open_get_tr(NULL);
 178         if (ret)
 179                 return ret;
 180
 181         if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
 182                 ret = dyn_events_release_all(NULL);
 183                 if (ret < 0)
 184                         return ret;
 185         }
 186
 187         return seq_open(file, &dyn_event_seq_op);
 188 }
 189
 190 static ssize_t dyn_event_write(struct file *file, const char __user *buffer,
 191                                 size_t count, loff_t *ppos)
 192 {
 193         return trace_parse_run_command(file, buffer, count, ppos,
 194                                        create_dyn_event);
 195 }
 196
 197 static const struct file_operations dynamic_events_ops = {
 198         .owner          = THIS_MODULE,
 199         .open           = dyn_event_open,
 200         .read           = seq_read,
 201         .llseek         = seq_lseek,
 202         .release        = seq_release,
 203         .write          = dyn_event_write,
 204 };
 205
 206 /* Make a tracefs interface for controlling dynamic events */
 207 static __init int init_dynamic_event(void)
 208 {
 209         struct dentry *d_tracer;
 210         struct dentry *entry;
 211
 212         d_tracer = tracing_init_dentry();
 213         if (IS_ERR(d_tracer))
 214                 return 0;
 215
 216         entry = tracefs_create_file("dynamic_events", 0644, d_tracer,
 217                                     NULL, &dynamic_events_ops);
 218
 219         /* Event list interface */
 220         if (!entry)
 221                 pr_warn("Could not create tracefs 'dynamic_events' entry\n");
 222
 223         return 0;
 224 }
 225 fs_initcall(init_dynamic_event);