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 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 */ 456