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1/*
2 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
3 *
4 */
5#include <linux/stacktrace.h>
6#include <linux/kallsyms.h>
7#include <linux/seq_file.h>
8#include <linux/spinlock.h>
9#include <linux/uaccess.h>
10#include <linux/ftrace.h>
11#include <linux/module.h>
12#include <linux/sysctl.h>
13#include <linux/init.h>
14
15#include <asm/setup.h>
16
17#include "trace.h"
18
19static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
20 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
21unsigned stack_trace_index[STACK_TRACE_ENTRIES];
22
23/*
24 * Reserve one entry for the passed in ip. This will allow
25 * us to remove most or all of the stack size overhead
26 * added by the stack tracer itself.
27 */
28struct stack_trace stack_trace_max = {
29 .max_entries = STACK_TRACE_ENTRIES - 1,
30 .entries = &stack_dump_trace[0],
31};
32
33unsigned long stack_trace_max_size;
34arch_spinlock_t stack_trace_max_lock =
35 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
36
37static DEFINE_PER_CPU(int, trace_active);
38static DEFINE_MUTEX(stack_sysctl_mutex);
39
40int stack_tracer_enabled;
41static int last_stack_tracer_enabled;
42
43void stack_trace_print(void)
44{
45 long i;
46 int size;
47
48 pr_emerg(" Depth Size Location (%d entries)\n"
49 " ----- ---- --------\n",
50 stack_trace_max.nr_entries);
51
52 for (i = 0; i < stack_trace_max.nr_entries; i++) {
53 if (stack_dump_trace[i] == ULONG_MAX)
54 break;
55 if (i+1 == stack_trace_max.nr_entries ||
56 stack_dump_trace[i+1] == ULONG_MAX)
57 size = stack_trace_index[i];
58 else
59 size = stack_trace_index[i] - stack_trace_index[i+1];
60
61 pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i],
62 size, (void *)stack_dump_trace[i]);
63 }
64}
65
66/*
67 * When arch-specific code overides this function, the following
68 * data should be filled up, assuming stack_trace_max_lock is held to
69 * prevent concurrent updates.
70 * stack_trace_index[]
71 * stack_trace_max
72 * stack_trace_max_size
73 */
74void __weak
75check_stack(unsigned long ip, unsigned long *stack)
76{
77 unsigned long this_size, flags; unsigned long *p, *top, *start;
78 static int tracer_frame;
79 int frame_size = ACCESS_ONCE(tracer_frame);
80 int i, x;
81
82 this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
83 this_size = THREAD_SIZE - this_size;
84 /* Remove the frame of the tracer */
85 this_size -= frame_size;
86
87 if (this_size <= stack_trace_max_size)
88 return;
89
90 /* we do not handle interrupt stacks yet */
91 if (!object_is_on_stack(stack))
92 return;
93
94 /* Can't do this from NMI context (can cause deadlocks) */
95 if (in_nmi())
96 return;
97
98 local_irq_save(flags);
99 arch_spin_lock(&stack_trace_max_lock);
100
101 /*
102 * RCU may not be watching, make it see us.
103 * The stack trace code uses rcu_sched.
104 */
105 rcu_irq_enter();
106
107 /* In case another CPU set the tracer_frame on us */
108 if (unlikely(!frame_size))
109 this_size -= tracer_frame;
110
111 /* a race could have already updated it */
112 if (this_size <= stack_trace_max_size)
113 goto out;
114
115 stack_trace_max_size = this_size;
116
117 stack_trace_max.nr_entries = 0;
118 stack_trace_max.skip = 3;
119
120 save_stack_trace(&stack_trace_max);
121
122 /* Skip over the overhead of the stack tracer itself */
123 for (i = 0; i < stack_trace_max.nr_entries; i++) {
124 if (stack_dump_trace[i] == ip)
125 break;
126 }
127
128 /*
129 * Some archs may not have the passed in ip in the dump.
130 * If that happens, we need to show everything.
131 */
132 if (i == stack_trace_max.nr_entries)
133 i = 0;
134
135 /*
136 * Now find where in the stack these are.
137 */
138 x = 0;
139 start = stack;
140 top = (unsigned long *)
141 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
142
143 /*
144 * Loop through all the entries. One of the entries may
145 * for some reason be missed on the stack, so we may
146 * have to account for them. If they are all there, this
147 * loop will only happen once. This code only takes place
148 * on a new max, so it is far from a fast path.
149 */
150 while (i < stack_trace_max.nr_entries) {
151 int found = 0;
152
153 stack_trace_index[x] = this_size;
154 p = start;
155
156 for (; p < top && i < stack_trace_max.nr_entries; p++) {
157 if (stack_dump_trace[i] == ULONG_MAX)
158 break;
159 /*
160 * The READ_ONCE_NOCHECK is used to let KASAN know that
161 * this is not a stack-out-of-bounds error.
162 */
163 if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {
164 stack_dump_trace[x] = stack_dump_trace[i++];
165 this_size = stack_trace_index[x++] =
166 (top - p) * sizeof(unsigned long);
167 found = 1;
168 /* Start the search from here */
169 start = p + 1;
170 /*
171 * We do not want to show the overhead
172 * of the stack tracer stack in the
173 * max stack. If we haven't figured
174 * out what that is, then figure it out
175 * now.
176 */
177 if (unlikely(!tracer_frame)) {
178 tracer_frame = (p - stack) *
179 sizeof(unsigned long);
180 stack_trace_max_size -= tracer_frame;
181 }
182 }
183 }
184
185 if (!found)
186 i++;
187 }
188
189 stack_trace_max.nr_entries = x;
190 for (; x < i; x++)
191 stack_dump_trace[x] = ULONG_MAX;
192
193 if (task_stack_end_corrupted(current)) {
194 stack_trace_print();
195 BUG();
196 }
197
198 out:
199 rcu_irq_exit();
200 arch_spin_unlock(&stack_trace_max_lock);
201 local_irq_restore(flags);
202}
203
204static void
205stack_trace_call(unsigned long ip, unsigned long parent_ip,
206 struct ftrace_ops *op, struct pt_regs *pt_regs)
207{
208 unsigned long stack;
209 int cpu;
210
211 preempt_disable_notrace();
212
213 cpu = raw_smp_processor_id();
214 /* no atomic needed, we only modify this variable by this cpu */
215 if (per_cpu(trace_active, cpu)++ != 0)
216 goto out;
217
218 ip += MCOUNT_INSN_SIZE;
219
220 check_stack(ip, &stack);
221
222 out:
223 per_cpu(trace_active, cpu)--;
224 /* prevent recursion in schedule */
225 preempt_enable_notrace();
226}
227
228static struct ftrace_ops trace_ops __read_mostly =
229{
230 .func = stack_trace_call,
231 .flags = FTRACE_OPS_FL_RECURSION_SAFE,
232};
233
234static ssize_t
235stack_max_size_read(struct file *filp, char __user *ubuf,
236 size_t count, loff_t *ppos)
237{
238 unsigned long *ptr = filp->private_data;
239 char buf[64];
240 int r;
241
242 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
243 if (r > sizeof(buf))
244 r = sizeof(buf);
245 return simple_read_from_buffer(ubuf, count, ppos, buf, r);
246}
247
248static ssize_t
249stack_max_size_write(struct file *filp, const char __user *ubuf,
250 size_t count, loff_t *ppos)
251{
252 long *ptr = filp->private_data;
253 unsigned long val, flags;
254 int ret;
255 int cpu;
256
257 ret = kstrtoul_from_user(ubuf, count, 10, &val);
258 if (ret)
259 return ret;
260
261 local_irq_save(flags);
262
263 /*
264 * In case we trace inside arch_spin_lock() or after (NMI),
265 * we will cause circular lock, so we also need to increase
266 * the percpu trace_active here.
267 */
268 cpu = smp_processor_id();
269 per_cpu(trace_active, cpu)++;
270
271 arch_spin_lock(&stack_trace_max_lock);
272 *ptr = val;
273 arch_spin_unlock(&stack_trace_max_lock);
274
275 per_cpu(trace_active, cpu)--;
276 local_irq_restore(flags);
277
278 return count;
279}
280
281static const struct file_operations stack_max_size_fops = {
282 .open = tracing_open_generic,
283 .read = stack_max_size_read,
284 .write = stack_max_size_write,
285 .llseek = default_llseek,
286};
287
288static void *
289__next(struct seq_file *m, loff_t *pos)
290{
291 long n = *pos - 1;
292
293 if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
294 return NULL;
295
296 m->private = (void *)n;
297 return &m->private;
298}
299
300static void *
301t_next(struct seq_file *m, void *v, loff_t *pos)
302{
303 (*pos)++;
304 return __next(m, pos);
305}
306
307static void *t_start(struct seq_file *m, loff_t *pos)
308{
309 int cpu;
310
311 local_irq_disable();
312
313 cpu = smp_processor_id();
314 per_cpu(trace_active, cpu)++;
315
316 arch_spin_lock(&stack_trace_max_lock);
317
318 if (*pos == 0)
319 return SEQ_START_TOKEN;
320
321 return __next(m, pos);
322}
323
324static void t_stop(struct seq_file *m, void *p)
325{
326 int cpu;
327
328 arch_spin_unlock(&stack_trace_max_lock);
329
330 cpu = smp_processor_id();
331 per_cpu(trace_active, cpu)--;
332
333 local_irq_enable();
334}
335
336static void trace_lookup_stack(struct seq_file *m, long i)
337{
338 unsigned long addr = stack_dump_trace[i];
339
340 seq_printf(m, "%pS\n", (void *)addr);
341}
342
343static void print_disabled(struct seq_file *m)
344{
345 seq_puts(m, "#\n"
346 "# Stack tracer disabled\n"
347 "#\n"
348 "# To enable the stack tracer, either add 'stacktrace' to the\n"
349 "# kernel command line\n"
350 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
351 "#\n");
352}
353
354static int t_show(struct seq_file *m, void *v)
355{
356 long i;
357 int size;
358
359 if (v == SEQ_START_TOKEN) {
360 seq_printf(m, " Depth Size Location"
361 " (%d entries)\n"
362 " ----- ---- --------\n",
363 stack_trace_max.nr_entries);
364
365 if (!stack_tracer_enabled && !stack_trace_max_size)
366 print_disabled(m);
367
368 return 0;
369 }
370
371 i = *(long *)v;
372
373 if (i >= stack_trace_max.nr_entries ||
374 stack_dump_trace[i] == ULONG_MAX)
375 return 0;
376
377 if (i+1 == stack_trace_max.nr_entries ||
378 stack_dump_trace[i+1] == ULONG_MAX)
379 size = stack_trace_index[i];
380 else
381 size = stack_trace_index[i] - stack_trace_index[i+1];
382
383 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size);
384
385 trace_lookup_stack(m, i);
386
387 return 0;
388}
389
390static const struct seq_operations stack_trace_seq_ops = {
391 .start = t_start,
392 .next = t_next,
393 .stop = t_stop,
394 .show = t_show,
395};
396
397static int stack_trace_open(struct inode *inode, struct file *file)
398{
399 return seq_open(file, &stack_trace_seq_ops);
400}
401
402static const struct file_operations stack_trace_fops = {
403 .open = stack_trace_open,
404 .read = seq_read,
405 .llseek = seq_lseek,
406 .release = seq_release,
407};
408
409static int
410stack_trace_filter_open(struct inode *inode, struct file *file)
411{
412 return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER,
413 inode, file);
414}
415
416static const struct file_operations stack_trace_filter_fops = {
417 .open = stack_trace_filter_open,
418 .read = seq_read,
419 .write = ftrace_filter_write,
420 .llseek = tracing_lseek,
421 .release = ftrace_regex_release,
422};
423
424int
425stack_trace_sysctl(struct ctl_table *table, int write,
426 void __user *buffer, size_t *lenp,
427 loff_t *ppos)
428{
429 int ret;
430
431 mutex_lock(&stack_sysctl_mutex);
432
433 ret = proc_dointvec(table, write, buffer, lenp, ppos);
434
435 if (ret || !write ||
436 (last_stack_tracer_enabled == !!stack_tracer_enabled))
437 goto out;
438
439 last_stack_tracer_enabled = !!stack_tracer_enabled;
440
441 if (stack_tracer_enabled)
442 register_ftrace_function(&trace_ops);
443 else
444 unregister_ftrace_function(&trace_ops);
445
446 out:
447 mutex_unlock(&stack_sysctl_mutex);
448 return ret;
449}
450
451static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
452
453static __init int enable_stacktrace(char *str)
454{
455 if (strncmp(str, "_filter=", 8) == 0)
456 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
457
458 stack_tracer_enabled = 1;
459 last_stack_tracer_enabled = 1;
460 return 1;
461}
462__setup("stacktrace", enable_stacktrace);
463
464static __init int stack_trace_init(void)
465{
466 struct dentry *d_tracer;
467
468 d_tracer = tracing_init_dentry();
469 if (IS_ERR(d_tracer))
470 return 0;
471
472 trace_create_file("stack_max_size", 0644, d_tracer,
473 &stack_trace_max_size, &stack_max_size_fops);
474
475 trace_create_file("stack_trace", 0444, d_tracer,
476 NULL, &stack_trace_fops);
477
478 trace_create_file("stack_trace_filter", 0444, d_tracer,
479 NULL, &stack_trace_filter_fops);
480
481 if (stack_trace_filter_buf[0])
482 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
483
484 if (stack_tracer_enabled)
485 register_ftrace_function(&trace_ops);
486
487 return 0;
488}
489
490device_initcall(stack_trace_init);
1/*
2 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
3 *
4 */
5#include <linux/stacktrace.h>
6#include <linux/kallsyms.h>
7#include <linux/seq_file.h>
8#include <linux/spinlock.h>
9#include <linux/uaccess.h>
10#include <linux/debugfs.h>
11#include <linux/ftrace.h>
12#include <linux/module.h>
13#include <linux/sysctl.h>
14#include <linux/init.h>
15#include <linux/fs.h>
16#include "trace.h"
17
18#define STACK_TRACE_ENTRIES 500
19
20static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
21 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
22static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
23
24static struct stack_trace max_stack_trace = {
25 .max_entries = STACK_TRACE_ENTRIES,
26 .entries = stack_dump_trace,
27};
28
29static unsigned long max_stack_size;
30static arch_spinlock_t max_stack_lock =
31 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
32
33static int stack_trace_disabled __read_mostly;
34static DEFINE_PER_CPU(int, trace_active);
35static DEFINE_MUTEX(stack_sysctl_mutex);
36
37int stack_tracer_enabled;
38static int last_stack_tracer_enabled;
39
40static inline void check_stack(void)
41{
42 unsigned long this_size, flags;
43 unsigned long *p, *top, *start;
44 int i;
45
46 this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1);
47 this_size = THREAD_SIZE - this_size;
48
49 if (this_size <= max_stack_size)
50 return;
51
52 /* we do not handle interrupt stacks yet */
53 if (!object_is_on_stack(&this_size))
54 return;
55
56 local_irq_save(flags);
57 arch_spin_lock(&max_stack_lock);
58
59 /* a race could have already updated it */
60 if (this_size <= max_stack_size)
61 goto out;
62
63 max_stack_size = this_size;
64
65 max_stack_trace.nr_entries = 0;
66 max_stack_trace.skip = 3;
67
68 save_stack_trace(&max_stack_trace);
69
70 /*
71 * Now find where in the stack these are.
72 */
73 i = 0;
74 start = &this_size;
75 top = (unsigned long *)
76 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
77
78 /*
79 * Loop through all the entries. One of the entries may
80 * for some reason be missed on the stack, so we may
81 * have to account for them. If they are all there, this
82 * loop will only happen once. This code only takes place
83 * on a new max, so it is far from a fast path.
84 */
85 while (i < max_stack_trace.nr_entries) {
86 int found = 0;
87
88 stack_dump_index[i] = this_size;
89 p = start;
90
91 for (; p < top && i < max_stack_trace.nr_entries; p++) {
92 if (*p == stack_dump_trace[i]) {
93 this_size = stack_dump_index[i++] =
94 (top - p) * sizeof(unsigned long);
95 found = 1;
96 /* Start the search from here */
97 start = p + 1;
98 }
99 }
100
101 if (!found)
102 i++;
103 }
104
105 out:
106 arch_spin_unlock(&max_stack_lock);
107 local_irq_restore(flags);
108}
109
110static void
111stack_trace_call(unsigned long ip, unsigned long parent_ip)
112{
113 int cpu;
114
115 if (unlikely(!ftrace_enabled || stack_trace_disabled))
116 return;
117
118 preempt_disable_notrace();
119
120 cpu = raw_smp_processor_id();
121 /* no atomic needed, we only modify this variable by this cpu */
122 if (per_cpu(trace_active, cpu)++ != 0)
123 goto out;
124
125 check_stack();
126
127 out:
128 per_cpu(trace_active, cpu)--;
129 /* prevent recursion in schedule */
130 preempt_enable_notrace();
131}
132
133static struct ftrace_ops trace_ops __read_mostly =
134{
135 .func = stack_trace_call,
136 .flags = FTRACE_OPS_FL_GLOBAL,
137};
138
139static ssize_t
140stack_max_size_read(struct file *filp, char __user *ubuf,
141 size_t count, loff_t *ppos)
142{
143 unsigned long *ptr = filp->private_data;
144 char buf[64];
145 int r;
146
147 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
148 if (r > sizeof(buf))
149 r = sizeof(buf);
150 return simple_read_from_buffer(ubuf, count, ppos, buf, r);
151}
152
153static ssize_t
154stack_max_size_write(struct file *filp, const char __user *ubuf,
155 size_t count, loff_t *ppos)
156{
157 long *ptr = filp->private_data;
158 unsigned long val, flags;
159 int ret;
160 int cpu;
161
162 ret = kstrtoul_from_user(ubuf, count, 10, &val);
163 if (ret)
164 return ret;
165
166 local_irq_save(flags);
167
168 /*
169 * In case we trace inside arch_spin_lock() or after (NMI),
170 * we will cause circular lock, so we also need to increase
171 * the percpu trace_active here.
172 */
173 cpu = smp_processor_id();
174 per_cpu(trace_active, cpu)++;
175
176 arch_spin_lock(&max_stack_lock);
177 *ptr = val;
178 arch_spin_unlock(&max_stack_lock);
179
180 per_cpu(trace_active, cpu)--;
181 local_irq_restore(flags);
182
183 return count;
184}
185
186static const struct file_operations stack_max_size_fops = {
187 .open = tracing_open_generic,
188 .read = stack_max_size_read,
189 .write = stack_max_size_write,
190 .llseek = default_llseek,
191};
192
193static void *
194__next(struct seq_file *m, loff_t *pos)
195{
196 long n = *pos - 1;
197
198 if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX)
199 return NULL;
200
201 m->private = (void *)n;
202 return &m->private;
203}
204
205static void *
206t_next(struct seq_file *m, void *v, loff_t *pos)
207{
208 (*pos)++;
209 return __next(m, pos);
210}
211
212static void *t_start(struct seq_file *m, loff_t *pos)
213{
214 int cpu;
215
216 local_irq_disable();
217
218 cpu = smp_processor_id();
219 per_cpu(trace_active, cpu)++;
220
221 arch_spin_lock(&max_stack_lock);
222
223 if (*pos == 0)
224 return SEQ_START_TOKEN;
225
226 return __next(m, pos);
227}
228
229static void t_stop(struct seq_file *m, void *p)
230{
231 int cpu;
232
233 arch_spin_unlock(&max_stack_lock);
234
235 cpu = smp_processor_id();
236 per_cpu(trace_active, cpu)--;
237
238 local_irq_enable();
239}
240
241static int trace_lookup_stack(struct seq_file *m, long i)
242{
243 unsigned long addr = stack_dump_trace[i];
244
245 return seq_printf(m, "%pS\n", (void *)addr);
246}
247
248static void print_disabled(struct seq_file *m)
249{
250 seq_puts(m, "#\n"
251 "# Stack tracer disabled\n"
252 "#\n"
253 "# To enable the stack tracer, either add 'stacktrace' to the\n"
254 "# kernel command line\n"
255 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
256 "#\n");
257}
258
259static int t_show(struct seq_file *m, void *v)
260{
261 long i;
262 int size;
263
264 if (v == SEQ_START_TOKEN) {
265 seq_printf(m, " Depth Size Location"
266 " (%d entries)\n"
267 " ----- ---- --------\n",
268 max_stack_trace.nr_entries - 1);
269
270 if (!stack_tracer_enabled && !max_stack_size)
271 print_disabled(m);
272
273 return 0;
274 }
275
276 i = *(long *)v;
277
278 if (i >= max_stack_trace.nr_entries ||
279 stack_dump_trace[i] == ULONG_MAX)
280 return 0;
281
282 if (i+1 == max_stack_trace.nr_entries ||
283 stack_dump_trace[i+1] == ULONG_MAX)
284 size = stack_dump_index[i];
285 else
286 size = stack_dump_index[i] - stack_dump_index[i+1];
287
288 seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size);
289
290 trace_lookup_stack(m, i);
291
292 return 0;
293}
294
295static const struct seq_operations stack_trace_seq_ops = {
296 .start = t_start,
297 .next = t_next,
298 .stop = t_stop,
299 .show = t_show,
300};
301
302static int stack_trace_open(struct inode *inode, struct file *file)
303{
304 return seq_open(file, &stack_trace_seq_ops);
305}
306
307static const struct file_operations stack_trace_fops = {
308 .open = stack_trace_open,
309 .read = seq_read,
310 .llseek = seq_lseek,
311 .release = seq_release,
312};
313
314int
315stack_trace_sysctl(struct ctl_table *table, int write,
316 void __user *buffer, size_t *lenp,
317 loff_t *ppos)
318{
319 int ret;
320
321 mutex_lock(&stack_sysctl_mutex);
322
323 ret = proc_dointvec(table, write, buffer, lenp, ppos);
324
325 if (ret || !write ||
326 (last_stack_tracer_enabled == !!stack_tracer_enabled))
327 goto out;
328
329 last_stack_tracer_enabled = !!stack_tracer_enabled;
330
331 if (stack_tracer_enabled)
332 register_ftrace_function(&trace_ops);
333 else
334 unregister_ftrace_function(&trace_ops);
335
336 out:
337 mutex_unlock(&stack_sysctl_mutex);
338 return ret;
339}
340
341static __init int enable_stacktrace(char *str)
342{
343 stack_tracer_enabled = 1;
344 last_stack_tracer_enabled = 1;
345 return 1;
346}
347__setup("stacktrace", enable_stacktrace);
348
349static __init int stack_trace_init(void)
350{
351 struct dentry *d_tracer;
352
353 d_tracer = tracing_init_dentry();
354
355 trace_create_file("stack_max_size", 0644, d_tracer,
356 &max_stack_size, &stack_max_size_fops);
357
358 trace_create_file("stack_trace", 0444, d_tracer,
359 NULL, &stack_trace_fops);
360
361 if (stack_tracer_enabled)
362 register_ftrace_function(&trace_ops);
363
364 return 0;
365}
366
367device_initcall(stack_trace_init);