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