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
probe_likely_condition(struct ftrace_likely_data * f,int val,int expect)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_buffer *buffer;
36 	struct trace_array_cpu *data;
37 	struct ring_buffer_event *event;
38 	struct trace_branch *entry;
39 	unsigned long flags;
40 	unsigned int trace_ctx;
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->array_buffer.data);
59 	if (atomic_read(&data->disabled))
60 		goto out;
61 
62 	trace_ctx = tracing_gen_ctx_flags(flags);
63 	buffer = tr->array_buffer.buffer;
64 	event = trace_buffer_lock_reserve(buffer, TRACE_BRANCH,
65 					  sizeof(*entry), trace_ctx);
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
trace_likely_condition(struct ftrace_likely_data * f,int val,int expect)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 
enable_branch_tracing(struct trace_array * tr)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 
disable_branch_tracing(void)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 
branch_trace_init(struct trace_array * tr)130 static int branch_trace_init(struct trace_array *tr)
131 {
132 	return enable_branch_tracing(tr);
133 }
134 
branch_trace_reset(struct trace_array * tr)135 static void branch_trace_reset(struct trace_array *tr)
136 {
137 	disable_branch_tracing();
138 }
139 
trace_branch_print(struct trace_iterator * iter,int flags,struct trace_event * event)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 
branch_print_header(struct seq_file * s)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 
init_branch_tracer(void)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
trace_likely_condition(struct ftrace_likely_data * f,int val,int expect)200 void trace_likely_condition(struct ftrace_likely_data *f, int val, int expect)
201 {
202 }
203 #endif /* CONFIG_BRANCH_TRACER */
204 
ftrace_likely_update(struct ftrace_likely_data * f,int val,int expect,int is_constant)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 
annotated_branch_stat_headers(struct seq_file * m)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 
get_incorrect_percent(const struct ftrace_branch_data * p)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 
branch_stat_process_file(struct ftrace_branch_data * p)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 
branch_stat_show(struct seq_file * m,struct ftrace_branch_data * p,const char * f)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 
branch_stat_show_normal(struct seq_file * m,struct ftrace_branch_data * p,const char * f)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 
annotate_branch_stat_show(struct seq_file * m,void * v)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 
annotated_branch_stat_start(struct tracer_stat * trace)317 static void *annotated_branch_stat_start(struct tracer_stat *trace)
318 {
319 	return __start_annotated_branch_profile;
320 }
321 
322 static void *
annotated_branch_stat_next(void * v,int idx)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 
annotated_branch_stat_cmp(const void * p1,const void * p2)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 
init_annotated_branch_stats(void)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 
all_branch_stat_headers(struct seq_file * m)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 
all_branch_stat_start(struct tracer_stat * trace)407 static void *all_branch_stat_start(struct tracer_stat *trace)
408 {
409 	return __start_branch_profile;
410 }
411 
412 static void *
all_branch_stat_next(void * v,int idx)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 
all_branch_stat_show(struct seq_file * m,void * v)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 
all_annotated_branch_stats(void)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