kernel/trace/trace_branch.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * unlikely profiler
   4  *
   5  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
   6  */
   7 #include <linux/kallsyms.h>
   8 #include <linux/seq_file.h>
   9 #include <linux/spinlock.h>
  10 #include <linux/irqflags.h>
  11 #include <linux/uaccess.h>
  12 #include <linux/module.h>
  13 #include <linux/ftrace.h>
  14 #include <linux/hash.h>
  15 #include <linux/fs.h>
  16 #include <asm/local.h>
  17
  18 #include "trace.h"
  19 #include "trace_stat.h"
  20 #include "trace_output.h"
  21
  22 #ifdef CONFIG_BRANCH_TRACER
  23
  24 static struct tracer branch_trace;
  25 static int branch_tracing_enabled __read_mostly;
  26 static DEFINE_MUTEX(branch_tracing_mutex);
  27
  28 static struct trace_array *branch_tracer;
  29
  30 static void
  31 probe_likely_condition(struct ftrace_likely_data *f, int val, int expect)
  32 {
  33         struct trace_event_call *call = &event_branch;
  34         struct trace_array *tr = branch_tracer;
  35         struct trace_buffer *buffer;
  36         struct trace_array_cpu *data;
  37         struct ring_buffer_event *event;
  38         struct trace_branch *entry;
  39         unsigned long flags;
  40         int pc;
  41         const char *p;
  42
  43         if (current->trace_recursion & TRACE_BRANCH_BIT)
  44                 return;
  45
  46         /*
  47          * I would love to save just the ftrace_likely_data pointer, but
  48          * this code can also be used by modules. Ugly things can happen
  49          * if the module is unloaded, and then we go and read the
  50          * pointer.  This is slower, but much safer.
  51          */
  52
  53         if (unlikely(!tr))
  54                 return;
  55
  56         raw_local_irq_save(flags);
  57         current->trace_recursion |= TRACE_BRANCH_BIT;
  58         data = this_cpu_ptr(tr->array_buffer.data);
  59         if (atomic_read(&data->disabled))
  60                 goto out;
  61
  62         pc = preempt_count();
  63         buffer = tr->array_buffer.buffer;
  64         event = trace_buffer_lock_reserve(buffer, TRACE_BRANCH,
  65                                           sizeof(*entry), flags, pc);
  66         if (!event)
  67                 goto out;
  68
  69         entry   = ring_buffer_event_data(event);
  70
  71         /* Strip off the path, only save the file */
  72         p = f->data.file + strlen(f->data.file);
  73         while (p >= f->data.file && *p != '/')
  74                 p--;
  75         p++;
  76
  77         strncpy(entry->func, f->data.func, TRACE_FUNC_SIZE);
  78         strncpy(entry->file, p, TRACE_FILE_SIZE);
  79         entry->func[TRACE_FUNC_SIZE] = 0;
  80         entry->file[TRACE_FILE_SIZE] = 0;
  81         entry->constant = f->constant;
  82         entry->line = f->data.line;
  83         entry->correct = val == expect;
  84
  85         if (!call_filter_check_discard(call, entry, buffer, event))
  86                 trace_buffer_unlock_commit_nostack(buffer, event);
  87
  88  out:
  89         current->trace_recursion &= ~TRACE_BRANCH_BIT;
  90         raw_local_irq_restore(flags);
  91 }
  92
  93 static inline
  94 void trace_likely_condition(struct ftrace_likely_data *f, int val, int expect)
  95 {
  96         if (!branch_tracing_enabled)
  97                 return;
  98
  99         probe_likely_condition(f, val, expect);
 100 }
 101
 102 int enable_branch_tracing(struct trace_array *tr)
 103 {
 104         mutex_lock(&branch_tracing_mutex);
 105         branch_tracer = tr;
 106         /*
 107          * Must be seen before enabling. The reader is a condition
 108          * where we do not need a matching rmb()
 109          */
 110         smp_wmb();
 111         branch_tracing_enabled++;
 112         mutex_unlock(&branch_tracing_mutex);
 113
 114         return 0;
 115 }
 116
 117 void disable_branch_tracing(void)
 118 {
 119         mutex_lock(&branch_tracing_mutex);
 120
 121         if (!branch_tracing_enabled)
 122                 goto out_unlock;
 123
 124         branch_tracing_enabled--;
 125
 126  out_unlock:
 127         mutex_unlock(&branch_tracing_mutex);
 128 }
 129
 130 static int branch_trace_init(struct trace_array *tr)
 131 {
 132         return enable_branch_tracing(tr);
 133 }
 134
 135 static void branch_trace_reset(struct trace_array *tr)
 136 {
 137         disable_branch_tracing();
 138 }
 139
 140 static enum print_line_t trace_branch_print(struct trace_iterator *iter,
 141                                             int flags, struct trace_event *event)
 142 {
 143         struct trace_branch *field;
 144
 145         trace_assign_type(field, iter->ent);
 146
 147         trace_seq_printf(&iter->seq, "[%s] %s:%s:%d\n",
 148                          field->correct ? "  ok  " : " MISS ",
 149                          field->func,
 150                          field->file,
 151                          field->line);
 152
 153         return trace_handle_return(&iter->seq);
 154 }
 155
 156 static void branch_print_header(struct seq_file *s)
 157 {
 158         seq_puts(s, "#           TASK-PID    CPU#    TIMESTAMP  CORRECT"
 159                     "  FUNC:FILE:LINE\n"
 160                     "#              | |       |          |         |   "
 161                     "    |\n");
 162 }
 163
 164 static struct trace_event_functions trace_branch_funcs = {
 165         .trace          = trace_branch_print,
 166 };
 167
 168 static struct trace_event trace_branch_event = {
 169         .type           = TRACE_BRANCH,
 170         .funcs          = &trace_branch_funcs,
 171 };
 172
 173 static struct tracer branch_trace __read_mostly =
 174 {
 175         .name           = "branch",
 176         .init           = branch_trace_init,
 177         .reset          = branch_trace_reset,
 178 #ifdef CONFIG_FTRACE_SELFTEST
 179         .selftest       = trace_selftest_startup_branch,
 180 #endif /* CONFIG_FTRACE_SELFTEST */
 181         .print_header   = branch_print_header,
 182 };
 183
 184 __init static int init_branch_tracer(void)
 185 {
 186         int ret;
 187
 188         ret = register_trace_event(&trace_branch_event);
 189         if (!ret) {
 190                 printk(KERN_WARNING "Warning: could not register "
 191                                     "branch events\n");
 192                 return 1;
 193         }
 194         return register_tracer(&branch_trace);
 195 }
 196 core_initcall(init_branch_tracer);
 197
 198 #else
 199 static inline
 200 void trace_likely_condition(struct ftrace_likely_data *f, int val, int expect)
 201 {
 202 }
 203 #endif /* CONFIG_BRANCH_TRACER */
 204
 205 void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 206                           int expect, int is_constant)
 207 {
 208         unsigned long flags = user_access_save();
 209
 210         /* A constant is always correct */
 211         if (is_constant) {
 212                 f->constant++;
 213                 val = expect;
 214         }
 215         /*
 216          * I would love to have a trace point here instead, but the
 217          * trace point code is so inundated with unlikely and likely
 218          * conditions that the recursive nightmare that exists is too
 219          * much to try to get working. At least for now.
 220          */
 221         trace_likely_condition(f, val, expect);
 222
 223         /* FIXME: Make this atomic! */
 224         if (val == expect)
 225                 f->data.correct++;
 226         else
 227                 f->data.incorrect++;
 228
 229         user_access_restore(flags);
 230 }
 231 EXPORT_SYMBOL(ftrace_likely_update);
 232
 233 extern unsigned long __start_annotated_branch_profile[];
 234 extern unsigned long __stop_annotated_branch_profile[];
 235
 236 static int annotated_branch_stat_headers(struct seq_file *m)
 237 {
 238         seq_puts(m, " correct incorrect  % "
 239                     "       Function                "
 240                     "  File              Line\n"
 241                     " ------- ---------  - "
 242                     "       --------                "
 243                     "  ----              ----\n");
 244         return 0;
 245 }
 246
 247 static inline long get_incorrect_percent(const struct ftrace_branch_data *p)
 248 {
 249         long percent;
 250
 251         if (p->correct) {
 252                 percent = p->incorrect * 100;
 253                 percent /= p->correct + p->incorrect;
 254         } else
 255                 percent = p->incorrect ? 100 : -1;
 256
 257         return percent;
 258 }
 259
 260 static const char *branch_stat_process_file(struct ftrace_branch_data *p)
 261 {
 262         const char *f;
 263
 264         /* Only print the file, not the path */
 265         f = p->file + strlen(p->file);
 266         while (f >= p->file && *f != '/')
 267                 f--;
 268         return ++f;
 269 }
 270
 271 static void branch_stat_show(struct seq_file *m,
 272                              struct ftrace_branch_data *p, const char *f)
 273 {
 274         long percent;
 275
 276         /*
 277          * The miss is overlayed on correct, and hit on incorrect.
 278          */
 279         percent = get_incorrect_percent(p);
 280
 281         if (percent < 0)
 282                 seq_puts(m, "  X ");
 283         else
 284                 seq_printf(m, "%3ld ", percent);
 285
 286         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 287 }
 288
 289 static int branch_stat_show_normal(struct seq_file *m,
 290                                    struct ftrace_branch_data *p, const char *f)
 291 {
 292         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 293         branch_stat_show(m, p, f);
 294         return 0;
 295 }
 296
 297 static int annotate_branch_stat_show(struct seq_file *m, void *v)
 298 {
 299         struct ftrace_likely_data *p = v;
 300         const char *f;
 301         int l;
 302
 303         f = branch_stat_process_file(&p->data);
 304
 305         if (!p->constant)
 306                 return branch_stat_show_normal(m, &p->data, f);
 307
 308         l = snprintf(NULL, 0, "/%lu", p->constant);
 309         l = l > 8 ? 0 : 8 - l;
 310
 311         seq_printf(m, "%8lu/%lu %*lu ",
 312                    p->data.correct, p->constant, l, p->data.incorrect);
 313         branch_stat_show(m, &p->data, f);
 314         return 0;
 315 }
 316
 317 static void *annotated_branch_stat_start(struct tracer_stat *trace)
 318 {
 319         return __start_annotated_branch_profile;
 320 }
 321
 322 static void *
 323 annotated_branch_stat_next(void *v, int idx)
 324 {
 325         struct ftrace_likely_data *p = v;
 326
 327         ++p;
 328
 329         if ((void *)p >= (void *)__stop_annotated_branch_profile)
 330                 return NULL;
 331
 332         return p;
 333 }
 334
 335 static int annotated_branch_stat_cmp(const void *p1, const void *p2)
 336 {
 337         const struct ftrace_branch_data *a = p1;
 338         const struct ftrace_branch_data *b = p2;
 339
 340         long percent_a, percent_b;
 341
 342         percent_a = get_incorrect_percent(a);
 343         percent_b = get_incorrect_percent(b);
 344
 345         if (percent_a < percent_b)
 346                 return -1;
 347         if (percent_a > percent_b)
 348                 return 1;
 349
 350         if (a->incorrect < b->incorrect)
 351                 return -1;
 352         if (a->incorrect > b->incorrect)
 353                 return 1;
 354
 355         /*
 356          * Since the above shows worse (incorrect) cases
 357          * first, we continue that by showing best (correct)
 358          * cases last.
 359          */
 360         if (a->correct > b->correct)
 361                 return -1;
 362         if (a->correct < b->correct)
 363                 return 1;
 364
 365         return 0;
 366 }
 367
 368 static struct tracer_stat annotated_branch_stats = {
 369         .name = "branch_annotated",
 370         .stat_start = annotated_branch_stat_start,
 371         .stat_next = annotated_branch_stat_next,
 372         .stat_cmp = annotated_branch_stat_cmp,
 373         .stat_headers = annotated_branch_stat_headers,
 374         .stat_show = annotate_branch_stat_show
 375 };
 376
 377 __init static int init_annotated_branch_stats(void)
 378 {
 379         int ret;
 380
 381         ret = register_stat_tracer(&annotated_branch_stats);
 382         if (!ret) {
 383                 printk(KERN_WARNING "Warning: could not register "
 384                                     "annotated branches stats\n");
 385                 return 1;
 386         }
 387         return 0;
 388 }
 389 fs_initcall(init_annotated_branch_stats);
 390
 391 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 392
 393 extern unsigned long __start_branch_profile[];
 394 extern unsigned long __stop_branch_profile[];
 395
 396 static int all_branch_stat_headers(struct seq_file *m)
 397 {
 398         seq_puts(m, "   miss      hit    % "
 399                     "       Function                "
 400                     "  File              Line\n"
 401                     " ------- ---------  - "
 402                     "       --------                "
 403                     "  ----              ----\n");
 404         return 0;
 405 }
 406
 407 static void *all_branch_stat_start(struct tracer_stat *trace)
 408 {
 409         return __start_branch_profile;
 410 }
 411
 412 static void *
 413 all_branch_stat_next(void *v, int idx)
 414 {
 415         struct ftrace_branch_data *p = v;
 416
 417         ++p;
 418
 419         if ((void *)p >= (void *)__stop_branch_profile)
 420                 return NULL;
 421
 422         return p;
 423 }
 424
 425 static int all_branch_stat_show(struct seq_file *m, void *v)
 426 {
 427         struct ftrace_branch_data *p = v;
 428         const char *f;
 429
 430         f = branch_stat_process_file(p);
 431         return branch_stat_show_normal(m, p, f);
 432 }
 433
 434 static struct tracer_stat all_branch_stats = {
 435         .name = "branch_all",
 436         .stat_start = all_branch_stat_start,
 437         .stat_next = all_branch_stat_next,
 438         .stat_headers = all_branch_stat_headers,
 439         .stat_show = all_branch_stat_show
 440 };
 441
 442 __init static int all_annotated_branch_stats(void)
 443 {
 444         int ret;
 445
 446         ret = register_stat_tracer(&all_branch_stats);
 447         if (!ret) {
 448                 printk(KERN_WARNING "Warning: could not register "
 449                                     "all branches stats\n");
 450                 return 1;
 451         }
 452         return 0;
 453 }
 454 fs_initcall(all_annotated_branch_stats);
 455 #endif /* CONFIG_PROFILE_ALL_BRANCHES */