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_array_cpu *data;
  36         struct ring_buffer_event *event;
  37         struct trace_branch *entry;
  38         struct ring_buffer *buffer;
  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->trace_buffer.data);
  59         if (atomic_read(&data->disabled))
  60                 goto out;
  61
  62         pc = preempt_count();
  63         buffer = tr->trace_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         /* A constant is always correct */
 209         if (is_constant) {
 210                 f->constant++;
 211                 val = expect;
 212         }
 213         /*
 214          * I would love to have a trace point here instead, but the
 215          * trace point code is so inundated with unlikely and likely
 216          * conditions that the recursive nightmare that exists is too
 217          * much to try to get working. At least for now.
 218          */
 219         trace_likely_condition(f, val, expect);
 220
 221         /* FIXME: Make this atomic! */
 222         if (val == expect)
 223                 f->data.correct++;
 224         else
 225                 f->data.incorrect++;
 226 }
 227 EXPORT_SYMBOL(ftrace_likely_update);
 228
 229 extern unsigned long __start_annotated_branch_profile[];
 230 extern unsigned long __stop_annotated_branch_profile[];
 231
 232 static int annotated_branch_stat_headers(struct seq_file *m)
 233 {
 234         seq_puts(m, " correct incorrect  % "
 235                     "       Function                "
 236                     "  File              Line\n"
 237                     " ------- ---------  - "
 238                     "       --------                "
 239                     "  ----              ----\n");
 240         return 0;
 241 }
 242
 243 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
 244 {
 245         long percent;
 246
 247         if (p->correct) {
 248                 percent = p->incorrect * 100;
 249                 percent /= p->correct + p->incorrect;
 250         } else
 251                 percent = p->incorrect ? 100 : -1;
 252
 253         return percent;
 254 }
 255
 256 static const char *branch_stat_process_file(struct ftrace_branch_data *p)
 257 {
 258         const char *f;
 259
 260         /* Only print the file, not the path */
 261         f = p->file + strlen(p->file);
 262         while (f >= p->file && *f != '/')
 263                 f--;
 264         return ++f;
 265 }
 266
 267 static void branch_stat_show(struct seq_file *m,
 268                              struct ftrace_branch_data *p, const char *f)
 269 {
 270         long percent;
 271
 272         /*
 273          * The miss is overlayed on correct, and hit on incorrect.
 274          */
 275         percent = get_incorrect_percent(p);
 276
 277         if (percent < 0)
 278                 seq_puts(m, "  X ");
 279         else
 280                 seq_printf(m, "%3ld ", percent);
 281
 282         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 283 }
 284
 285 static int branch_stat_show_normal(struct seq_file *m,
 286                                    struct ftrace_branch_data *p, const char *f)
 287 {
 288         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 289         branch_stat_show(m, p, f);
 290         return 0;
 291 }
 292
 293 static int annotate_branch_stat_show(struct seq_file *m, void *v)
 294 {
 295         struct ftrace_likely_data *p = v;
 296         const char *f;
 297         int l;
 298
 299         f = branch_stat_process_file(&p->data);
 300
 301         if (!p->constant)
 302                 return branch_stat_show_normal(m, &p->data, f);
 303
 304         l = snprintf(NULL, 0, "/%lu", p->constant);
 305         l = l > 8 ? 0 : 8 - l;
 306
 307         seq_printf(m, "%8lu/%lu %*lu ",
 308                    p->data.correct, p->constant, l, p->data.incorrect);
 309         branch_stat_show(m, &p->data, f);
 310         return 0;
 311 }
 312
 313 static void *annotated_branch_stat_start(struct tracer_stat *trace)
 314 {
 315         return __start_annotated_branch_profile;
 316 }
 317
 318 static void *
 319 annotated_branch_stat_next(void *v, int idx)
 320 {
 321         struct ftrace_likely_data *p = v;
 322
 323         ++p;
 324
 325         if ((void *)p >= (void *)__stop_annotated_branch_profile)
 326                 return NULL;
 327
 328         return p;
 329 }
 330
 331 static int annotated_branch_stat_cmp(void *p1, void *p2)
 332 {
 333         struct ftrace_branch_data *a = p1;
 334         struct ftrace_branch_data *b = p2;
 335
 336         long percent_a, percent_b;
 337
 338         percent_a = get_incorrect_percent(a);
 339         percent_b = get_incorrect_percent(b);
 340
 341         if (percent_a < percent_b)
 342                 return -1;
 343         if (percent_a > percent_b)
 344                 return 1;
 345
 346         if (a->incorrect < b->incorrect)
 347                 return -1;
 348         if (a->incorrect > b->incorrect)
 349                 return 1;
 350
 351         /*
 352          * Since the above shows worse (incorrect) cases
 353          * first, we continue that by showing best (correct)
 354          * cases last.
 355          */
 356         if (a->correct > b->correct)
 357                 return -1;
 358         if (a->correct < b->correct)
 359                 return 1;
 360
 361         return 0;
 362 }
 363
 364 static struct tracer_stat annotated_branch_stats = {
 365         .name = "branch_annotated",
 366         .stat_start = annotated_branch_stat_start,
 367         .stat_next = annotated_branch_stat_next,
 368         .stat_cmp = annotated_branch_stat_cmp,
 369         .stat_headers = annotated_branch_stat_headers,
 370         .stat_show = annotate_branch_stat_show
 371 };
 372
 373 __init static int init_annotated_branch_stats(void)
 374 {
 375         int ret;
 376
 377         ret = register_stat_tracer(&annotated_branch_stats);
 378         if (!ret) {
 379                 printk(KERN_WARNING "Warning: could not register "
 380                                     "annotated branches stats\n");
 381                 return 1;
 382         }
 383         return 0;
 384 }
 385 fs_initcall(init_annotated_branch_stats);
 386
 387 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 388
 389 extern unsigned long __start_branch_profile[];
 390 extern unsigned long __stop_branch_profile[];
 391
 392 static int all_branch_stat_headers(struct seq_file *m)
 393 {
 394         seq_puts(m, "   miss      hit    % "
 395                     "       Function                "
 396                     "  File              Line\n"
 397                     " ------- ---------  - "
 398                     "       --------                "
 399                     "  ----              ----\n");
 400         return 0;
 401 }
 402
 403 static void *all_branch_stat_start(struct tracer_stat *trace)
 404 {
 405         return __start_branch_profile;
 406 }
 407
 408 static void *
 409 all_branch_stat_next(void *v, int idx)
 410 {
 411         struct ftrace_branch_data *p = v;
 412
 413         ++p;
 414
 415         if ((void *)p >= (void *)__stop_branch_profile)
 416                 return NULL;
 417
 418         return p;
 419 }
 420
 421 static int all_branch_stat_show(struct seq_file *m, void *v)
 422 {
 423         struct ftrace_branch_data *p = v;
 424         const char *f;
 425
 426         f = branch_stat_process_file(p);
 427         return branch_stat_show_normal(m, p, f);
 428 }
 429
 430 static struct tracer_stat all_branch_stats = {
 431         .name = "branch_all",
 432         .stat_start = all_branch_stat_start,
 433         .stat_next = all_branch_stat_next,
 434         .stat_headers = all_branch_stat_headers,
 435         .stat_show = all_branch_stat_show
 436 };
 437
 438 __init static int all_annotated_branch_stats(void)
 439 {
 440         int ret;
 441
 442         ret = register_stat_tracer(&all_branch_stats);
 443         if (!ret) {
 444                 printk(KERN_WARNING "Warning: could not register "
 445                                     "all branches stats\n");
 446                 return 1;
 447         }
 448         return 0;
 449 }
 450 fs_initcall(all_annotated_branch_stats);
 451 #endif /* CONFIG_PROFILE_ALL_BRANCHES */