kernel/trace/trace_stat.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Infrastructure for statistic tracing (histogram output).
   4  *
   5  * Copyright (C) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com>
   6  *
   7  * Based on the code from trace_branch.c which is
   8  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
   9  *
  10  */
  11
  12 #include <linux/security.h>
  13 #include <linux/list.h>
  14 #include <linux/slab.h>
  15 #include <linux/rbtree.h>
  16 #include <linux/tracefs.h>
  17 #include "trace_stat.h"
  18 #include "trace.h"
  19
  20
  21 /*
  22  * List of stat red-black nodes from a tracer
  23  * We use a such tree to sort quickly the stat
  24  * entries from the tracer.
  25  */
  26 struct stat_node {
  27         struct rb_node          node;
  28         void                    *stat;
  29 };
  30
  31 /* A stat session is the stats output in one file */
  32 struct stat_session {
  33         struct list_head        session_list;
  34         struct tracer_stat      *ts;
  35         struct rb_root          stat_root;
  36         struct mutex            stat_mutex;
  37         struct dentry           *file;
  38 };
  39
  40 /* All of the sessions currently in use. Each stat file embed one session */
  41 static LIST_HEAD(all_stat_sessions);
  42 static DEFINE_MUTEX(all_stat_sessions_mutex);
  43
  44 /* The root directory for all stat files */
  45 static struct dentry            *stat_dir;
  46
  47 static void __reset_stat_session(struct stat_session *session)
  48 {
  49         struct stat_node *snode, *n;
  50
  51         rbtree_postorder_for_each_entry_safe(snode, n, &session->stat_root, node) {
  52                 if (session->ts->stat_release)
  53                         session->ts->stat_release(snode->stat);
  54                 kfree(snode);
  55         }
  56
  57         session->stat_root = RB_ROOT;
  58 }
  59
  60 static void reset_stat_session(struct stat_session *session)
  61 {
  62         mutex_lock(&session->stat_mutex);
  63         __reset_stat_session(session);
  64         mutex_unlock(&session->stat_mutex);
  65 }
  66
  67 static void destroy_session(struct stat_session *session)
  68 {
  69         tracefs_remove(session->file);
  70         __reset_stat_session(session);
  71         mutex_destroy(&session->stat_mutex);
  72         kfree(session);
  73 }
  74
  75 static int insert_stat(struct rb_root *root, void *stat, cmp_func_t cmp)
  76 {
  77         struct rb_node **new = &(root->rb_node), *parent = NULL;
  78         struct stat_node *data;
  79
  80         data = kzalloc(sizeof(*data), GFP_KERNEL);
  81         if (!data)
  82                 return -ENOMEM;
  83         data->stat = stat;
  84
  85         /*
  86          * Figure out where to put new node
  87          * This is a descendent sorting
  88          */
  89         while (*new) {
  90                 struct stat_node *this;
  91                 int result;
  92
  93                 this = container_of(*new, struct stat_node, node);
  94                 result = cmp(data->stat, this->stat);
  95
  96                 parent = *new;
  97                 if (result >= 0)
  98                         new = &((*new)->rb_left);
  99                 else
 100                         new = &((*new)->rb_right);
 101         }
 102
 103         rb_link_node(&data->node, parent, new);
 104         rb_insert_color(&data->node, root);
 105         return 0;
 106 }
 107
 108 /*
 109  * For tracers that don't provide a stat_cmp callback.
 110  * This one will force an insertion as right-most node
 111  * in the rbtree.
 112  */
 113 static int dummy_cmp(const void *p1, const void *p2)
 114 {
 115         return -1;
 116 }
 117
 118 /*
 119  * Initialize the stat rbtree at each trace_stat file opening.
 120  * All of these copies and sorting are required on all opening
 121  * since the stats could have changed between two file sessions.
 122  */
 123 static int stat_seq_init(struct stat_session *session)
 124 {
 125         struct tracer_stat *ts = session->ts;
 126         struct rb_root *root = &session->stat_root;
 127         void *stat;
 128         int ret = 0;
 129         int i;
 130
 131         mutex_lock(&session->stat_mutex);
 132         __reset_stat_session(session);
 133
 134         if (!ts->stat_cmp)
 135                 ts->stat_cmp = dummy_cmp;
 136
 137         stat = ts->stat_start(ts);
 138         if (!stat)
 139                 goto exit;
 140
 141         ret = insert_stat(root, stat, ts->stat_cmp);
 142         if (ret)
 143                 goto exit;
 144
 145         /*
 146          * Iterate over the tracer stat entries and store them in an rbtree.
 147          */
 148         for (i = 1; ; i++) {
 149                 stat = ts->stat_next(stat, i);
 150
 151                 /* End of insertion */
 152                 if (!stat)
 153                         break;
 154
 155                 ret = insert_stat(root, stat, ts->stat_cmp);
 156                 if (ret)
 157                         goto exit_free_rbtree;
 158         }
 159
 160 exit:
 161         mutex_unlock(&session->stat_mutex);
 162         return ret;
 163
 164 exit_free_rbtree:
 165         __reset_stat_session(session);
 166         mutex_unlock(&session->stat_mutex);
 167         return ret;
 168 }
 169
 170
 171 static void *stat_seq_start(struct seq_file *s, loff_t *pos)
 172 {
 173         struct stat_session *session = s->private;
 174         struct rb_node *node;
 175         int n = *pos;
 176         int i;
 177
 178         /* Prevent from tracer switch or rbtree modification */
 179         mutex_lock(&session->stat_mutex);
 180
 181         /* If we are in the beginning of the file, print the headers */
 182         if (session->ts->stat_headers) {
 183                 if (n == 0)
 184                         return SEQ_START_TOKEN;
 185                 n--;
 186         }
 187
 188         node = rb_first(&session->stat_root);
 189         for (i = 0; node && i < n; i++)
 190                 node = rb_next(node);
 191
 192         return node;
 193 }
 194
 195 static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
 196 {
 197         struct stat_session *session = s->private;
 198         struct rb_node *node = p;
 199
 200         (*pos)++;
 201
 202         if (p == SEQ_START_TOKEN)
 203                 return rb_first(&session->stat_root);
 204
 205         return rb_next(node);
 206 }
 207
 208 static void stat_seq_stop(struct seq_file *s, void *p)
 209 {
 210         struct stat_session *session = s->private;
 211         mutex_unlock(&session->stat_mutex);
 212 }
 213
 214 static int stat_seq_show(struct seq_file *s, void *v)
 215 {
 216         struct stat_session *session = s->private;
 217         struct stat_node *l = container_of(v, struct stat_node, node);
 218
 219         if (v == SEQ_START_TOKEN)
 220                 return session->ts->stat_headers(s);
 221
 222         return session->ts->stat_show(s, l->stat);
 223 }
 224
 225 static const struct seq_operations trace_stat_seq_ops = {
 226         .start          = stat_seq_start,
 227         .next           = stat_seq_next,
 228         .stop           = stat_seq_stop,
 229         .show           = stat_seq_show
 230 };
 231
 232 /* The session stat is refilled and resorted at each stat file opening */
 233 static int tracing_stat_open(struct inode *inode, struct file *file)
 234 {
 235         int ret;
 236         struct seq_file *m;
 237         struct stat_session *session = inode->i_private;
 238
 239         ret = security_locked_down(LOCKDOWN_TRACEFS);
 240         if (ret)
 241                 return ret;
 242
 243         ret = stat_seq_init(session);
 244         if (ret)
 245                 return ret;
 246
 247         ret = seq_open(file, &trace_stat_seq_ops);
 248         if (ret) {
 249                 reset_stat_session(session);
 250                 return ret;
 251         }
 252
 253         m = file->private_data;
 254         m->private = session;
 255         return ret;
 256 }
 257
 258 /*
 259  * Avoid consuming memory with our now useless rbtree.
 260  */
 261 static int tracing_stat_release(struct inode *i, struct file *f)
 262 {
 263         struct stat_session *session = i->i_private;
 264
 265         reset_stat_session(session);
 266
 267         return seq_release(i, f);
 268 }
 269
 270 static const struct file_operations tracing_stat_fops = {
 271         .open           = tracing_stat_open,
 272         .read           = seq_read,
 273         .llseek         = seq_lseek,
 274         .release        = tracing_stat_release
 275 };
 276
 277 static int tracing_stat_init(void)
 278 {
 279         int ret;
 280
 281         ret = tracing_init_dentry();
 282         if (ret)
 283                 return -ENODEV;
 284
 285         stat_dir = tracefs_create_dir("trace_stat", NULL);
 286         if (!stat_dir) {
 287                 pr_warn("Could not create tracefs 'trace_stat' entry\n");
 288                 return -ENOMEM;
 289         }
 290         return 0;
 291 }
 292
 293 static int init_stat_file(struct stat_session *session)
 294 {
 295         int ret;
 296
 297         if (!stat_dir && (ret = tracing_stat_init()))
 298                 return ret;
 299
 300         session->file = tracefs_create_file(session->ts->name, TRACE_MODE_WRITE,
 301                                             stat_dir, session,
 302                                             &tracing_stat_fops);
 303         if (!session->file)
 304                 return -ENOMEM;
 305         return 0;
 306 }
 307
 308 int register_stat_tracer(struct tracer_stat *trace)
 309 {
 310         struct stat_session *session, *node;
 311         int ret = -EINVAL;
 312
 313         if (!trace)
 314                 return -EINVAL;
 315
 316         if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
 317                 return -EINVAL;
 318
 319         /* Already registered? */
 320         mutex_lock(&all_stat_sessions_mutex);
 321         list_for_each_entry(node, &all_stat_sessions, session_list) {
 322                 if (node->ts == trace)
 323                         goto out;
 324         }
 325
 326         ret = -ENOMEM;
 327         /* Init the session */
 328         session = kzalloc(sizeof(*session), GFP_KERNEL);
 329         if (!session)
 330                 goto out;
 331
 332         session->ts = trace;
 333         INIT_LIST_HEAD(&session->session_list);
 334         mutex_init(&session->stat_mutex);
 335
 336         ret = init_stat_file(session);
 337         if (ret) {
 338                 destroy_session(session);
 339                 goto out;
 340         }
 341
 342         ret = 0;
 343         /* Register */
 344         list_add_tail(&session->session_list, &all_stat_sessions);
 345  out:
 346         mutex_unlock(&all_stat_sessions_mutex);
 347
 348         return ret;
 349 }
 350
 351 void unregister_stat_tracer(struct tracer_stat *trace)
 352 {
 353         struct stat_session *node, *tmp;
 354
 355         mutex_lock(&all_stat_sessions_mutex);
 356         list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
 357                 if (node->ts == trace) {
 358                         list_del(&node->session_list);
 359                         destroy_session(node);
 360                         break;
 361                 }
 362         }
 363         mutex_unlock(&all_stat_sessions_mutex);
 364 }