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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         /* A constant is always correct */
209         if (is_constant) {
210                 f->constant++;
211                 val = expect;
212         }
213         /*
214          * I would love to have a trace point here instead, but the
215          * trace point code is so inundated with unlikely and likely
216          * conditions that the recursive nightmare that exists is too
217          * much to try to get working. At least for now.
218          */
219         trace_likely_condition(f, val, expect);
220 
221         /* FIXME: Make this atomic! */
222         if (val == expect)
223                 f->data.correct++;
224         else
225                 f->data.incorrect++;
226 }
227 EXPORT_SYMBOL(ftrace_likely_update);
228 
229 extern unsigned long __start_annotated_branch_profile[];
230 extern unsigned long __stop_annotated_branch_profile[];
231 
232 static int annotated_branch_stat_headers(struct seq_file *m)
233 {
234         seq_puts(m, " correct incorrect  % "
235                     "       Function                "
236                     "  File              Line\n"
237                     " ------- ---------  - "
238                     "       --------                "
239                     "  ----              ----\n");
240         return 0;
241 }
242 
243 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
244 {
245         long percent;
246 
247         if (p->correct) {
248                 percent = p->incorrect * 100;
249                 percent /= p->correct + p->incorrect;
250         } else
251                 percent = p->incorrect ? 100 : -1;
252 
253         return percent;
254 }
255 
256 static const char *branch_stat_process_file(struct ftrace_branch_data *p)
257 {
258         const char *f;
259 
260         /* Only print the file, not the path */
261         f = p->file + strlen(p->file);
262         while (f >= p->file && *f != '/')
263                 f--;
264         return ++f;
265 }
266 
267 static void branch_stat_show(struct seq_file *m,
268                              struct ftrace_branch_data *p, const char *f)
269 {
270         long percent;
271 
272         /*
273          * The miss is overlayed on correct, and hit on incorrect.
274          */
275         percent = get_incorrect_percent(p);
276 
277         if (percent < 0)
278                 seq_puts(m, "  X ");
279         else
280                 seq_printf(m, "%3ld ", percent);
281 
282         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
283 }
284 
285 static int branch_stat_show_normal(struct seq_file *m,
286                                    struct ftrace_branch_data *p, const char *f)
287 {
288         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
289         branch_stat_show(m, p, f);
290         return 0;
291 }
292 
293 static int annotate_branch_stat_show(struct seq_file *m, void *v)
294 {
295         struct ftrace_likely_data *p = v;
296         const char *f;
297         int l;
298 
299         f = branch_stat_process_file(&p->data);
300 
301         if (!p->constant)
302                 return branch_stat_show_normal(m, &p->data, f);
303 
304         l = snprintf(NULL, 0, "/%lu", p->constant);
305         l = l > 8 ? 0 : 8 - l;
306 
307         seq_printf(m, "%8lu/%lu %*lu ",
308                    p->data.correct, p->constant, l, p->data.incorrect);
309         branch_stat_show(m, &p->data, f);
310         return 0;
311 }
312 
313 static void *annotated_branch_stat_start(struct tracer_stat *trace)
314 {
315         return __start_annotated_branch_profile;
316 }
317 
318 static void *
319 annotated_branch_stat_next(void *v, int idx)
320 {
321         struct ftrace_likely_data *p = v;
322 
323         ++p;
324 
325         if ((void *)p >= (void *)__stop_annotated_branch_profile)
326                 return NULL;
327 
328         return p;
329 }
330 
331 static int annotated_branch_stat_cmp(void *p1, void *p2)
332 {
333         struct ftrace_branch_data *a = p1;
334         struct ftrace_branch_data *b = p2;
335 
336         long percent_a, percent_b;
337 
338         percent_a = get_incorrect_percent(a);
339         percent_b = get_incorrect_percent(b);
340 
341         if (percent_a < percent_b)
342                 return -1;
343         if (percent_a > percent_b)
344                 return 1;
345 
346         if (a->incorrect < b->incorrect)
347                 return -1;
348         if (a->incorrect > b->incorrect)
349                 return 1;
350 
351         /*
352          * Since the above shows worse (incorrect) cases
353          * first, we continue that by showing best (correct)
354          * cases last.
355          */
356         if (a->correct > b->correct)
357                 return -1;
358         if (a->correct < b->correct)
359                 return 1;
360 
361         return 0;
362 }
363 
364 static struct tracer_stat annotated_branch_stats = {
365         .name = "branch_annotated",
366         .stat_start = annotated_branch_stat_start,
367         .stat_next = annotated_branch_stat_next,
368         .stat_cmp = annotated_branch_stat_cmp,
369         .stat_headers = annotated_branch_stat_headers,
370         .stat_show = annotate_branch_stat_show
371 };
372 
373 __init static int init_annotated_branch_stats(void)
374 {
375         int ret;
376 
377         ret = register_stat_tracer(&annotated_branch_stats);
378         if (!ret) {
379                 printk(KERN_WARNING "Warning: could not register "
380                                     "annotated branches stats\n");
381                 return 1;
382         }
383         return 0;
384 }
385 fs_initcall(init_annotated_branch_stats);
386 
387 #ifdef CONFIG_PROFILE_ALL_BRANCHES
388 
389 extern unsigned long __start_branch_profile[];
390 extern unsigned long __stop_branch_profile[];
391 
392 static int all_branch_stat_headers(struct seq_file *m)
393 {
394         seq_puts(m, "   miss      hit    % "
395                     "       Function                "
396                     "  File              Line\n"
397                     " ------- ---------  - "
398                     "       --------                "
399                     "  ----              ----\n");
400         return 0;
401 }
402 
403 static void *all_branch_stat_start(struct tracer_stat *trace)
404 {
405         return __start_branch_profile;
406 }
407 
408 static void *
409 all_branch_stat_next(void *v, int idx)
410 {
411         struct ftrace_branch_data *p = v;
412 
413         ++p;
414 
415         if ((void *)p >= (void *)__stop_branch_profile)
416                 return NULL;
417 
418         return p;
419 }
420 
421 static int all_branch_stat_show(struct seq_file *m, void *v)
422 {
423         struct ftrace_branch_data *p = v;
424         const char *f;
425 
426         f = branch_stat_process_file(p);
427         return branch_stat_show_normal(m, p, f);
428 }
429 
430 static struct tracer_stat all_branch_stats = {
431         .name = "branch_all",
432         .stat_start = all_branch_stat_start,
433         .stat_next = all_branch_stat_next,
434         .stat_headers = all_branch_stat_headers,
435         .stat_show = all_branch_stat_show
436 };
437 
438 __init static int all_annotated_branch_stats(void)
439 {
440         int ret;
441 
442         ret = register_stat_tracer(&all_branch_stats);
443         if (!ret) {
444                 printk(KERN_WARNING "Warning: could not register "
445                                     "all branches stats\n");
446                 return 1;
447         }
448         return 0;
449 }
450 fs_initcall(all_annotated_branch_stats);
451 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
452 

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