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   1 /*
   2  * unlikely profiler
   3  *
   4  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
   5  */
   6 #include <linux/kallsyms.h>
   7 #include <linux/seq_file.h>
   8 #include <linux/spinlock.h>
   9 #include <linux/irqflags.h>
  10 #include <linux/debugfs.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_output.h"
  20
  21 static struct tracer branch_trace;
  22
  23 #ifdef CONFIG_BRANCH_TRACER
  24
  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_branch_data *f, int val, int expect)
  32 {
  33         struct trace_array *tr = branch_tracer;
  34         struct ring_buffer_event *event;
  35         struct trace_branch *entry;
  36         unsigned long flags, irq_flags;
  37         int cpu, pc;
  38         const char *p;
  39
  40         /*
  41          * I would love to save just the ftrace_likely_data pointer, but
  42          * this code can also be used by modules. Ugly things can happen
  43          * if the module is unloaded, and then we go and read the
  44          * pointer.  This is slower, but much safer.
  45          */
  46
  47         if (unlikely(!tr))
  48                 return;
  49
  50         local_irq_save(flags);
  51         cpu = raw_smp_processor_id();
  52         if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
  53                 goto out;
  54
  55         event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
  56                                          &irq_flags);
  57         if (!event)
  58                 goto out;
  59
  60         pc = preempt_count();
  61         entry   = ring_buffer_event_data(event);
  62         tracing_generic_entry_update(&entry->ent, flags, pc);
  63         entry->ent.type         = TRACE_BRANCH;
  64
  65         /* Strip off the path, only save the file */
  66         p = f->file + strlen(f->file);
  67         while (p >= f->file && *p != '/')
  68                 p--;
  69         p++;
  70
  71         strncpy(entry->func, f->func, TRACE_FUNC_SIZE);
  72         strncpy(entry->file, p, TRACE_FILE_SIZE);
  73         entry->func[TRACE_FUNC_SIZE] = 0;
  74         entry->file[TRACE_FILE_SIZE] = 0;
  75         entry->line = f->line;
  76         entry->correct = val == expect;
  77
  78         ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
  79
  80  out:
  81         atomic_dec(&tr->data[cpu]->disabled);
  82         local_irq_restore(flags);
  83 }
  84
  85 static inline
  86 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
  87 {
  88         if (!branch_tracing_enabled)
  89                 return;
  90
  91         probe_likely_condition(f, val, expect);
  92 }
  93
  94 int enable_branch_tracing(struct trace_array *tr)
  95 {
  96         int ret = 0;
  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 ret;
 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 void start_branch_trace(struct trace_array *tr)
 125 {
 126         enable_branch_tracing(tr);
 127 }
 128
 129 static void stop_branch_trace(struct trace_array *tr)
 130 {
 131         disable_branch_tracing();
 132 }
 133
 134 static int branch_trace_init(struct trace_array *tr)
 135 {
 136         int cpu;
 137
 138         for_each_online_cpu(cpu)
 139                 tracing_reset(tr, cpu);
 140
 141         start_branch_trace(tr);
 142         return 0;
 143 }
 144
 145 static void branch_trace_reset(struct trace_array *tr)
 146 {
 147         stop_branch_trace(tr);
 148 }
 149
 150 static int
 151 trace_print_print(struct trace_seq *s, struct trace_entry *entry, int flags)
 152 {
 153         struct print_entry *field;
 154
 155         trace_assign_type(field, entry);
 156
 157         if (seq_print_ip_sym(s, field->ip, flags))
 158                 goto partial;
 159
 160         if (trace_seq_printf(s, ": %s", field->buf))
 161                 goto partial;
 162
 163  partial:
 164         return TRACE_TYPE_PARTIAL_LINE;
 165 }
 166
 167 static int
 168 trace_branch_print(struct trace_seq *s, struct trace_entry *entry, int flags)
 169 {
 170         struct trace_branch *field;
 171
 172         trace_assign_type(field, entry);
 173
 174         if (trace_seq_printf(s, "[%s] %s:%s:%d\n",
 175                              field->correct ? "  ok  " : " MISS ",
 176                              field->func,
 177                              field->file,
 178                              field->line))
 179                 return TRACE_TYPE_PARTIAL_LINE;
 180
 181         return 0;
 182 }
 183
 184
 185 static struct trace_event trace_branch_event = {
 186         .type           = TRACE_BRANCH,
 187         .trace          = trace_branch_print,
 188         .latency_trace  = trace_branch_print,
 189         .raw            = trace_nop_print,
 190         .hex            = trace_nop_print,
 191         .binary         = trace_nop_print,
 192 };
 193
 194 #else
 195 static inline
 196 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 197 {
 198 }
 199 #endif /* CONFIG_BRANCH_TRACER */
 200
 201 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
 202 {
 203         /*
 204          * I would love to have a trace point here instead, but the
 205          * trace point code is so inundated with unlikely and likely
 206          * conditions that the recursive nightmare that exists is too
 207          * much to try to get working. At least for now.
 208          */
 209         trace_likely_condition(f, val, expect);
 210
 211         /* FIXME: Make this atomic! */
 212         if (val == expect)
 213                 f->correct++;
 214         else
 215                 f->incorrect++;
 216 }
 217 EXPORT_SYMBOL(ftrace_likely_update);
 218
 219 extern unsigned long __start_annotated_branch_profile[];
 220 extern unsigned long __stop_annotated_branch_profile[];
 221
 222 static int annotated_branch_stat_headers(struct seq_file *m)
 223 {
 224         seq_printf(m, " correct incorrect  %% ");
 225         seq_printf(m, "       Function                "
 226                               "  File              Line\n"
 227                               " ------- ---------  - "
 228                               "       --------                "
 229                               "  ----              ----\n");
 230         return 0;
 231 }
 232
 233 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
 234 {
 235         long percent;
 236
 237         if (p->correct) {
 238                 percent = p->incorrect * 100;
 239                 percent /= p->correct + p->incorrect;
 240         } else
 241                 percent = p->incorrect ? 100 : -1;
 242
 243         return percent;
 244 }
 245
 246 static int branch_stat_show(struct seq_file *m, void *v)
 247 {
 248         struct ftrace_branch_data *p = v;
 249         const char *f;
 250         long percent;
 251
 252         /* Only print the file, not the path */
 253         f = p->file + strlen(p->file);
 254         while (f >= p->file && *f != '/')
 255                 f--;
 256         f++;
 257
 258         /*
 259          * The miss is overlayed on correct, and hit on incorrect.
 260          */
 261         percent = get_incorrect_percent(p);
 262
 263         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 264         if (percent < 0)
 265                 seq_printf(m, "  X ");
 266         else
 267                 seq_printf(m, "%3ld ", percent);
 268         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 269         return 0;
 270 }
 271
 272 static void *annotated_branch_stat_start(void)
 273 {
 274         return __start_annotated_branch_profile;
 275 }
 276
 277 static void *
 278 annotated_branch_stat_next(void *v, int idx)
 279 {
 280         struct ftrace_branch_data *p = v;
 281
 282         ++p;
 283
 284         if ((void *)p >= (void *)__stop_annotated_branch_profile)
 285                 return NULL;
 286
 287         return p;
 288 }
 289
 290 static int annotated_branch_stat_cmp(void *p1, void *p2)
 291 {
 292         struct ftrace_branch_data *a = p1;
 293         struct ftrace_branch_data *b = p2;
 294
 295         long percent_a, percent_b;
 296
 297         percent_a = get_incorrect_percent(a);
 298         percent_b = get_incorrect_percent(b);
 299
 300         if (percent_a < percent_b)
 301                 return -1;
 302         if (percent_a > percent_b)
 303                 return 1;
 304         else
 305                 return 0;
 306 }
 307
 308 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 309
 310 extern unsigned long __start_branch_profile[];
 311 extern unsigned long __stop_branch_profile[];
 312
 313 static int all_branch_stat_headers(struct seq_file *m)
 314 {
 315         seq_printf(m, "   miss      hit    %% ");
 316         seq_printf(m, "       Function                "
 317                               "  File              Line\n"
 318                               " ------- ---------  - "
 319                               "       --------                "
 320                               "  ----              ----\n");
 321         return 0;
 322 }
 323
 324 static void *all_branch_stat_start(void)
 325 {
 326         return __start_branch_profile;
 327 }
 328
 329 static void *
 330 all_branch_stat_next(void *v, int idx)
 331 {
 332         struct ftrace_branch_data *p = v;
 333
 334         ++p;
 335
 336         if ((void *)p >= (void *)__stop_branch_profile)
 337                 return NULL;
 338
 339         return p;
 340 }
 341
 342 static struct tracer_stat branch_stats[] = {
 343         {.name = "annotated",
 344         .stat_start = annotated_branch_stat_start,
 345         .stat_next = annotated_branch_stat_next,
 346         .stat_cmp = annotated_branch_stat_cmp,
 347         .stat_headers = annotated_branch_stat_headers,
 348         .stat_show = branch_stat_show},
 349
 350         {.name = "all",
 351         .stat_start = all_branch_stat_start,
 352         .stat_next = all_branch_stat_next,
 353         .stat_headers = all_branch_stat_headers,
 354         .stat_show = branch_stat_show},
 355
 356         { }
 357 };
 358 #else
 359 static struct tracer_stat branch_stats[] = {
 360         {.name = "annotated",
 361         .stat_start = annotated_branch_stat_start,
 362         .stat_next = annotated_branch_stat_next,
 363         .stat_cmp = annotated_branch_stat_cmp,
 364         .stat_headers = annotated_branch_stat_headers,
 365         .stat_show = branch_stat_show},
 366
 367         { }
 368 };
 369 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
 370
 371
 372 static struct tracer branch_trace __read_mostly =
 373 {
 374         .name           = "branch",
 375 #ifdef CONFIG_BRANCH_TRACER
 376         .init           = branch_trace_init,
 377         .reset          = branch_trace_reset,
 378 #ifdef CONFIG_FTRACE_SELFTEST
 379         .selftest       = trace_selftest_startup_branch,
 380 #endif /* CONFIG_FTRACE_SELFTEST */
 381 #endif
 382         .stats          = branch_stats
 383 };
 384
 385 __init static int init_branch_trace(void)
 386 {
 387 #ifdef CONFIG_BRANCH_TRACER
 388         int ret;
 389         ret = register_ftrace_event(&trace_branch_event);
 390         if (!ret) {
 391                 printk(KERN_WARNING "Warning: could not register branch events\n");
 392                 return 1;
 393         }
 394 #endif
 395
 396         return register_tracer(&branch_trace);
 397 }
 398 device_initcall(init_branch_trace);