aboutsummaryrefslogtreecommitdiff
path: root/kernel/trace/trace_branch.c
blob: 23f9b02ce967a2a2564a13e67e77b92552bbfb6f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
/*
 * unlikely profiler
 *
 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
 */
#include <linux/kallsyms.h>
#include <linux/seq_file.h>
#include <linux/spinlock.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/hash.h>
#include <linux/fs.h>
#include <asm/local.h>
#include "trace.h"

#ifdef CONFIG_BRANCH_TRACER

static int branch_tracing_enabled __read_mostly;
static DEFINE_MUTEX(branch_tracing_mutex);
static struct trace_array *branch_tracer;

static void
probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
{
	struct trace_array *tr = branch_tracer;
	struct ring_buffer_event *event;
	struct trace_branch *entry;
	unsigned long flags, irq_flags;
	int cpu, pc;
	const char *p;

	/*
	 * I would love to save just the ftrace_likely_data pointer, but
	 * this code can also be used by modules. Ugly things can happen
	 * if the module is unloaded, and then we go and read the
	 * pointer.  This is slower, but much safer.
	 */

	if (unlikely(!tr))
		return;

	raw_local_irq_save(flags);
	cpu = raw_smp_processor_id();
	if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
		goto out;

	event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
					 &irq_flags);
	if (!event)
		goto out;

	pc = preempt_count();
	entry	= ring_buffer_event_data(event);
	tracing_generic_entry_update(&entry->ent, flags, pc);
	entry->ent.type		= TRACE_BRANCH;

	/* Strip off the path, only save the file */
	p = f->file + strlen(f->file);
	while (p >= f->file && *p != '/')
		p--;
	p++;

	strncpy(entry->func, f->func, TRACE_FUNC_SIZE);
	strncpy(entry->file, p, TRACE_FILE_SIZE);
	entry->func[TRACE_FUNC_SIZE] = 0;
	entry->file[TRACE_FILE_SIZE] = 0;
	entry->line = f->line;
	entry->correct = val == expect;

	ring_buffer_unlock_commit(tr->buffer, event, irq_flags);

 out:
	atomic_dec(&tr->data[cpu]->disabled);
	raw_local_irq_restore(flags);
}

static inline
void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
{
	if (!branch_tracing_enabled)
		return;

	probe_likely_condition(f, val, expect);
}

int enable_branch_tracing(struct trace_array *tr)
{
	int ret = 0;

	mutex_lock(&branch_tracing_mutex);
	branch_tracer = tr;
	/*
	 * Must be seen before enabling. The reader is a condition
	 * where we do not need a matching rmb()
	 */
	smp_wmb();
	branch_tracing_enabled++;
	mutex_unlock(&branch_tracing_mutex);

	return ret;
}

void disable_branch_tracing(void)
{
	mutex_lock(&branch_tracing_mutex);

	if (!branch_tracing_enabled)
		goto out_unlock;

	branch_tracing_enabled--;

 out_unlock:
	mutex_unlock(&branch_tracing_mutex);
}

static void start_branch_trace(struct trace_array *tr)
{
	enable_branch_tracing(tr);
}

static void stop_branch_trace(struct trace_array *tr)
{
	disable_branch_tracing();
}

static int branch_trace_init(struct trace_array *tr)
{
	int cpu;

	for_each_online_cpu(cpu)
		tracing_reset(tr, cpu);

	start_branch_trace(tr);
	return 0;
}

static void branch_trace_reset(struct trace_array *tr)
{
	stop_branch_trace(tr);
}

struct tracer branch_trace __read_mostly =
{
	.name		= "branch",
	.init		= branch_trace_init,
	.reset		= branch_trace_reset,
#ifdef CONFIG_FTRACE_SELFTEST
	.selftest	= trace_selftest_startup_branch,
#endif
};

__init static int init_branch_trace(void)
{
	return register_tracer(&branch_trace);
}

device_initcall(init_branch_trace);
#else
static inline
void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
{
}
#endif /* CONFIG_BRANCH_TRACER */

void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
{
	/*
	 * I would love to have a trace point here instead, but the
	 * trace point code is so inundated with unlikely and likely
	 * conditions that the recursive nightmare that exists is too
	 * much to try to get working. At least for now.
	 */
	trace_likely_condition(f, val, expect);

	/* FIXME: Make this atomic! */
	if (val == expect)
		f->correct++;
	else
		f->incorrect++;
}
EXPORT_SYMBOL(ftrace_likely_update);

struct ftrace_pointer {
	void		*start;
	void		*stop;
};

static void *
t_next(struct seq_file *m, void *v, loff_t *pos)
{
	struct ftrace_pointer *f = m->private;
	struct ftrace_branch_data *p = v;

	(*pos)++;

	if (v == (void *)1)
		return f->start;

	++p;

	if ((void *)p >= (void *)f->stop)
		return NULL;

	return p;
}

static void *t_start(struct seq_file *m, loff_t *pos)
{
	void *t = (void *)1;
	loff_t l = 0;

	for (; t && l < *pos; t = t_next(m, t, &l))
		;

	return t;
}

static void t_stop(struct seq_file *m, void *p)
{
}

static int t_show(struct seq_file *m, void *v)
{
	struct ftrace_branch_data *p = v;
	const char *f;
	unsigned long percent;

	if (v == (void *)1) {
		seq_printf(m, " correct incorrect  %% "
			      "       Function                "
			      "  File              Line\n"
			      " ------- ---------  - "
			      "       --------                "
			      "  ----              ----\n");
		return 0;
	}

	/* Only print the file, not the path */
	f = p->file + strlen(p->file);
	while (f >= p->file && *f != '/')
		f--;
	f++;

	if (p->correct) {
		percent = p->incorrect * 100;
		percent /= p->correct + p->incorrect;
	} else
		percent = p->incorrect ? 100 : 0;

	seq_printf(m, "%8lu %8lu %3lu ", p->correct, p->incorrect, percent);
	seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
	return 0;
}

static struct seq_operations tracing_likely_seq_ops = {
	.start		= t_start,
	.next		= t_next,
	.stop		= t_stop,
	.show		= t_show,
};

static int tracing_likely_open(struct inode *inode, struct file *file)
{
	int ret;

	ret = seq_open(file, &tracing_likely_seq_ops);
	if (!ret) {
		struct seq_file *m = file->private_data;
		m->private = (void *)inode->i_private;
	}

	return ret;
}

static struct file_operations tracing_likely_fops = {
	.open		= tracing_likely_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
};

extern unsigned long __start_likely_profile[];
extern unsigned long __stop_likely_profile[];
extern unsigned long __start_unlikely_profile[];
extern unsigned long __stop_unlikely_profile[];

static struct ftrace_pointer ftrace_likely_pos = {
	.start			= __start_likely_profile,
	.stop			= __stop_likely_profile,
};

static struct ftrace_pointer ftrace_unlikely_pos = {
	.start			= __start_unlikely_profile,
	.stop			= __stop_unlikely_profile,
};

static __init int ftrace_branch_init(void)
{
	struct dentry *d_tracer;
	struct dentry *entry;

	d_tracer = tracing_init_dentry();

	entry = debugfs_create_file("profile_likely", 0444, d_tracer,
				    &ftrace_likely_pos,
				    &tracing_likely_fops);
	if (!entry)
		pr_warning("Could not create debugfs 'profile_likely' entry\n");

	entry = debugfs_create_file("profile_unlikely", 0444, d_tracer,
				    &ftrace_unlikely_pos,
				    &tracing_likely_fops);
	if (!entry)
		pr_warning("Could not create debugfs"
			   " 'profile_unlikely' entry\n");

	return 0;
}

device_initcall(ftrace_branch_init);