kernel/trace/trace_branch.c

   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 #include "trace.h"
  18
  19 #ifdef CONFIG_BRANCH_TRACER
  20
  21 static int branch_tracing_enabled __read_mostly;
  22 static DEFINE_MUTEX(branch_tracing_mutex);
  23 static struct trace_array *branch_tracer;
  24
  25 static void
  26 probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
  27 {
  28         struct trace_array *tr = branch_tracer;
  29         struct ring_buffer_event *event;
  30         struct trace_branch *entry;
  31         unsigned long flags, irq_flags;
  32         int cpu, pc;
  33         const char *p;
  34
  35         /*
  36          * I would love to save just the ftrace_likely_data pointer, but
  37          * this code can also be used by modules. Ugly things can happen
  38          * if the module is unloaded, and then we go and read the
  39          * pointer.  This is slower, but much safer.
  40          */
  41
  42         if (unlikely(!tr))
  43                 return;
  44
  45         local_irq_save(flags);
  46         cpu = raw_smp_processor_id();
  47         if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
  48                 goto out;
  49
  50         event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
  51                                          &irq_flags);
  52         if (!event)
  53                 goto out;
  54
  55         pc = preempt_count();
  56         entry   = ring_buffer_event_data(event);
  57         tracing_generic_entry_update(&entry->ent, flags, pc);
  58         entry->ent.type         = TRACE_BRANCH;
  59
  60         /* Strip off the path, only save the file */
  61         p = f->file + strlen(f->file);
  62         while (p >= f->file && *p != '/')
  63                 p--;
  64         p++;
  65
  66         strncpy(entry->func, f->func, TRACE_FUNC_SIZE);
  67         strncpy(entry->file, p, TRACE_FILE_SIZE);
  68         entry->func[TRACE_FUNC_SIZE] = 0;
  69         entry->file[TRACE_FILE_SIZE] = 0;
  70         entry->line = f->line;
  71         entry->correct = val == expect;
  72
  73         ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
  74
  75  out:
  76         atomic_dec(&tr->data[cpu]->disabled);
  77         local_irq_restore(flags);
  78 }
  79
  80 static inline
  81 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
  82 {
  83         if (!branch_tracing_enabled)
  84                 return;
  85
  86         probe_likely_condition(f, val, expect);
  87 }
  88
  89 int enable_branch_tracing(struct trace_array *tr)
  90 {
  91         int ret = 0;
  92
  93         mutex_lock(&branch_tracing_mutex);
  94         branch_tracer = tr;
  95         /*
  96          * Must be seen before enabling. The reader is a condition
  97          * where we do not need a matching rmb()
  98          */
  99         smp_wmb();
 100         branch_tracing_enabled++;
 101         mutex_unlock(&branch_tracing_mutex);
 102
 103         return ret;
 104 }
 105
 106 void disable_branch_tracing(void)
 107 {
 108         mutex_lock(&branch_tracing_mutex);
 109
 110         if (!branch_tracing_enabled)
 111                 goto out_unlock;
 112
 113         branch_tracing_enabled--;
 114
 115  out_unlock:
 116         mutex_unlock(&branch_tracing_mutex);
 117 }
 118
 119 static void start_branch_trace(struct trace_array *tr)
 120 {
 121         enable_branch_tracing(tr);
 122 }
 123
 124 static void stop_branch_trace(struct trace_array *tr)
 125 {
 126         disable_branch_tracing();
 127 }
 128
 129 static int branch_trace_init(struct trace_array *tr)
 130 {
 131         int cpu;
 132
 133         for_each_online_cpu(cpu)
 134                 tracing_reset(tr, cpu);
 135
 136         start_branch_trace(tr);
 137         return 0;
 138 }
 139
 140 static void branch_trace_reset(struct trace_array *tr)
 141 {
 142         stop_branch_trace(tr);
 143 }
 144
 145 struct tracer branch_trace __read_mostly =
 146 {
 147         .name           = "branch",
 148         .init           = branch_trace_init,
 149         .reset          = branch_trace_reset,
 150 #ifdef CONFIG_FTRACE_SELFTEST
 151         .selftest       = trace_selftest_startup_branch,
 152 #endif
 153 };
 154
 155 __init static int init_branch_trace(void)
 156 {
 157         return register_tracer(&branch_trace);
 158 }
 159
 160 device_initcall(init_branch_trace);
 161 #else
 162 static inline
 163 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 164 {
 165 }
 166 #endif /* CONFIG_BRANCH_TRACER */
 167
 168 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
 169 {
 170         /*
 171          * I would love to have a trace point here instead, but the
 172          * trace point code is so inundated with unlikely and likely
 173          * conditions that the recursive nightmare that exists is too
 174          * much to try to get working. At least for now.
 175          */
 176         trace_likely_condition(f, val, expect);
 177
 178         /* FIXME: Make this atomic! */
 179         if (val == expect)
 180                 f->correct++;
 181         else
 182                 f->incorrect++;
 183 }
 184 EXPORT_SYMBOL(ftrace_likely_update);
 185
 186 struct ftrace_pointer {
 187         void            *start;
 188         void            *stop;
 189         int             hit;
 190 };
 191
 192 static void *
 193 t_next(struct seq_file *m, void *v, loff_t *pos)
 194 {
 195         const struct ftrace_pointer *f = m->private;
 196         struct ftrace_branch_data *p = v;
 197
 198         (*pos)++;
 199
 200         if (v == (void *)1)
 201                 return f->start;
 202
 203         ++p;
 204
 205         if ((void *)p >= (void *)f->stop)
 206                 return NULL;
 207
 208         return p;
 209 }
 210
 211 static void *t_start(struct seq_file *m, loff_t *pos)
 212 {
 213         void *t = (void *)1;
 214         loff_t l = 0;
 215
 216         for (; t && l < *pos; t = t_next(m, t, &l))
 217                 ;
 218
 219         return t;
 220 }
 221
 222 static void t_stop(struct seq_file *m, void *p)
 223 {
 224 }
 225
 226 static int t_show(struct seq_file *m, void *v)
 227 {
 228         const struct ftrace_pointer *fp = m->private;
 229         struct ftrace_branch_data *p = v;
 230         const char *f;
 231         long percent;
 232
 233         if (v == (void *)1) {
 234                 if (fp->hit)
 235                         seq_printf(m, "   miss      hit    %% ");
 236                 else
 237                         seq_printf(m, " correct incorrect  %% ");
 238                 seq_printf(m, "       Function                "
 239                               "  File              Line\n"
 240                               " ------- ---------  - "
 241                               "       --------                "
 242                               "  ----              ----\n");
 243                 return 0;
 244         }
 245
 246         /* Only print the file, not the path */
 247         f = p->file + strlen(p->file);
 248         while (f >= p->file && *f != '/')
 249                 f--;
 250         f++;
 251
 252         /*
 253          * The miss is overlayed on correct, and hit on incorrect.
 254          */
 255         if (p->correct) {
 256                 percent = p->incorrect * 100;
 257                 percent /= p->correct + p->incorrect;
 258         } else
 259                 percent = p->incorrect ? 100 : -1;
 260
 261         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 262         if (percent < 0)
 263                 seq_printf(m, "  X ");
 264         else
 265                 seq_printf(m, "%3ld ", percent);
 266         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 267         return 0;
 268 }
 269
 270 static struct seq_operations tracing_likely_seq_ops = {
 271         .start          = t_start,
 272         .next           = t_next,
 273         .stop           = t_stop,
 274         .show           = t_show,
 275 };
 276
 277 static int tracing_branch_open(struct inode *inode, struct file *file)
 278 {
 279         int ret;
 280
 281         ret = seq_open(file, &tracing_likely_seq_ops);
 282         if (!ret) {
 283                 struct seq_file *m = file->private_data;
 284                 m->private = (void *)inode->i_private;
 285         }
 286
 287         return ret;
 288 }
 289
 290 static const struct file_operations tracing_branch_fops = {
 291         .open           = tracing_branch_open,
 292         .read           = seq_read,
 293         .llseek         = seq_lseek,
 294 };
 295
 296 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 297 extern unsigned long __start_branch_profile[];
 298 extern unsigned long __stop_branch_profile[];
 299
 300 static const struct ftrace_pointer ftrace_branch_pos = {
 301         .start                  = __start_branch_profile,
 302         .stop                   = __stop_branch_profile,
 303         .hit                    = 1,
 304 };
 305
 306 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
 307
 308 extern unsigned long __start_annotated_branch_profile[];
 309 extern unsigned long __stop_annotated_branch_profile[];
 310
 311 static const struct ftrace_pointer ftrace_annotated_branch_pos = {
 312         .start                  = __start_annotated_branch_profile,
 313         .stop                   = __stop_annotated_branch_profile,
 314 };
 315
 316 static __init int ftrace_branch_init(void)
 317 {
 318         struct dentry *d_tracer;
 319         struct dentry *entry;
 320
 321         d_tracer = tracing_init_dentry();
 322
 323         entry = debugfs_create_file("profile_annotated_branch", 0444, d_tracer,
 324                                     (void *)&ftrace_annotated_branch_pos,
 325                                     &tracing_branch_fops);
 326         if (!entry)
 327                 pr_warning("Could not create debugfs "
 328                            "'profile_annotatet_branch' entry\n");
 329
 330 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 331         entry = debugfs_create_file("profile_branch", 0444, d_tracer,
 332                                     (void *)&ftrace_branch_pos,
 333                                     &tracing_branch_fops);
 334         if (!entry)
 335                 pr_warning("Could not create debugfs"
 336                            " 'profile_branch' entry\n");
 337 #endif
 338
 339         return 0;
 340 }
 341
 342 device_initcall(ftrace_branch_init);