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Linux/kernel/trace/trace_branch.c

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  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(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(void *p1, void *p2)
336 {
337         struct ftrace_branch_data *a = p1;
338         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 

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